Next Article in Journal
Copaiba Oil-Loaded Polymeric Nanocapsules: Production and In Vitro Biosafety Evaluation on Lung Cells as a Pre-Formulation Step to Produce Phytotherapeutic Medicine
Next Article in Special Issue
Extracellular Vesicles for Dental Pulp and Periodontal Regeneration
Previous Article in Journal
In Silico Quantification of Intersubject Variability on Aerosol Deposition in the Oral Airway
Previous Article in Special Issue
Functional Hydrogels and Their Applications in Craniomaxillofacial Bone Regeneration
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Pharmaceutics
Volume 15
Issue 1
10.3390/pharmaceutics15010158
pharmaceutics-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles thumb_up
...
Endorse textsms
...
Comment
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Review

Creating a Microenvironment to Give Wings to Dental Pulp Regeneration—Bioactive Scaffolds

by
Nan Hu
1,2,
Weiping Li
2,3,
Wentao Jiang
1,2,
Jin Wen
2,4,5,* and
Shensheng Gu
1,2,*
1
Department of Endodontics, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai 200011, China
2
National Center for Stomatology, National Clinical Research Center for Oral Diseases, Shanghai Key Laboratory of Stomatology, Shanghai Research Institute of Stomatology, Shanghai 200011, China
3
Department of Oral and Maxillofacial Head & Neck Oncology, Shanghai Ninth People’s Hospital, College of Stomatology, Shanghai Jiao Tong University, Shanghai 200011, China
4
Department of Prosthodontics, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, College of Stomatology, Shanghai Jiao Tong University, Shanghai 200011, China
5
Shanghai Key Laboratory of Stomatology, Shanghai Engineering Research Center of Advanced Dental Technology and Materials, Shanghai 200125, China
*
Authors to whom correspondence should be addressed.
Pharmaceutics 2023, 15(1), 158; https://doi.org/10.3390/pharmaceutics15010158
Submission received: 31 October 2022 / Revised: 13 December 2022 / Accepted: 23 December 2022 / Published: 3 January 2023
(This article belongs to the Special Issue Biomaterials and Agents: Pharmaceutical and Biomedical Applications in Dental Research)
Browse Figures
Versions Notes

Abstract

:
Dental pulp and periapical diseases make patients suffer from acute pain and economic loss. Although root canal therapies, as demonstrated through evidence-based medicine, can relieve symptoms and are commonly employed by dentists, it is still difficult to fully restore a dental pulp’s nutrition, sensory, and immune-regulation functions. In recent years, researchers have made significant progress in tissue engineering to regenerate dental pulp in a desired microenvironment. With breakthroughs in regenerative medicine and material science, bioactive scaffolds play a pivotal role in creating a suitable microenvironment for cell survival, proliferation, and differentiation, following dental restoration and regeneration. This article focuses on current challenges and novel perspectives about bioactive scaffolds in creating a microenvironment to promote dental pulp regeneration. We hope our readers will gain a deeper understanding and new inspiration of dental pulp regeneration through our summary.

1. Introduction

As a unique structure in our body, the tooth contains a hard shell and soft inner tissues to perform the chewing function. Once the hard shell is injured by caries or trauma, the outer bacterium will not only exert detrimental influences on the internal environment of the teeth but may also give rise to inflammation of the pulp or periapical tissue [1]. The onset of caries, pulpitis, and periapical periodontitis is more easily overlooked, so the incidence rate has been comparatively high in recent years. [2,3]. This results in painful experiences, tooth defects, and even tooth loss, which have long perplexed people tremendously. The conventional treatment method is root canal therapy, but that still leaves challenging problems such as persistent periapical infection, tooth discoloration, and heightened tooth brittleness [4,5,6]. Dental pulp regeneration with the participation of stem cells is an excellent way to resolve it. For some young permanent teeth, regenerative pulp therapy can partially be achieved by indirect or direct pulp capping, apexification, and revascularization [7]. However, the methods have limited effectiveness for mature permanent teeth, and further studies are still in the laboratory or clinical trial stage [8].
The tooth development process provides a favorable reference for pulp tissue engineering. In the seventh week of an embryo, the tooth lamina is formed in the primitive mouth. Then, mesenchymal stem cells from the ectodermal mesenchymal layer start to form dental papilla, which further develops into dentin and pulp through three continuing stages: the bud, cap, and bell phase [9]. This process is regulated by complex signals, such as TGF-β, Wnt, and FGF signaling pathways, during epithelial-mesenchymal interactions [10]. Furthermore, blood supply is vital for early tooth development. The papilla is infiltrated by multitudinous capillaries during the bell stage of embryonic development [1,11]. In a healthy and mature tooth, the vascular system predominantly contains supply arterioles, capillary networks, and venular networks, which constantly adapt to the nutritional, metabolic, and homeostatic needs of the tissues [1,12,13]. Regarding neurogenesis, pioneer nerve fibers ramify into the tooth germ and penetrate the inner dental papilla until dentinogenesis begins to form pulp tissue [9,14].
Teeth can regenerate once affected by caries, trauma, or other severe external stimuli. Odontoblasts around the dental pulp will secrete reparative dentin to cope with mild injuries. Nonetheless, suppose the damage is extensive and results in the death of odontoblasts; the mesenchymal stem cells will first redifferentiate into odontoblast-like cells and then secrete extracellular components to form restorative dentin subsequently [15]. This process is also regulated by many growth factors, such as TGF-β, IGF, and FGF2 [16,17,18]. When the damage continues to evolve, it will affect the dental pulp cells and the local blood supply and nerve function [19,20]. It is easy to obtain an oxygen-deficient environment since oxygen can travel about 100–200 microns through diffusion [21]. Such hypoxia conditions result in cells secreting pro-angiogenic factors that act on adjacent vascular endothelial cells to propel neovascularization. Unfortunately, this self-regulation is comparatively limited [22,23]. If the pulp continues to suffer from the insufficient blood supply, pulpitis and pulp necrosis may occur and even deteriorate to periapical periodontitis [24]. Meanwhile, peripheral nerve damage and gene expression changes will also occur, resulting in changes in pain thresholds and then give rise to various painful symptoms [25]. Consequently, it is paramount to maintaining a suitable microenvironment for dental pulp restoration and regeneration to enhance its regenerative capacity, whether the pulp is mildly irritated or even completely necrosis.
The effects of tissue regeneration rest with mesenchymal stem cells and their microenvironment, just as plants’ growth depends on their healthy seeds and fertile soil (Figure 1) [26,27,28]. Dental stem cells are a large class of commonly used seed cells with the ability of cell proliferation and multi-differentiation, such as dental pulp stem cells (DPSCs), stem cells from the apical papilla (SCAPs), and stem cells from human exfoliated deciduous teeth (SHEDs), which have the potential to differentiating dental pulp [29,30,31,32]. The natural dental pulp microenvironment is crucial to maintaining the phenotype and differentiation potential of stem cells [33]. Specifically, the cellular microenvironment is the local and micro-scale environment of cell interaction, including soluble biochemicals, insoluble extracellular matrix, and surrounding cells, which is vital for regulating cell behavior and function [34,35,36]. It is well known that mesenchymal stem cells, scaffolds, and growth factors are the three critical components of tissue regeneration [37]. In other words, scaffolds and bioactive factors provide a favorable microenvironment and stimulate the differentiation of stem cells to propel pulp regeneration [38]. This paper primarily concentrates on forming bioactive materials with strategies from different angles to provide a favorable microenvironment for dental pulp regeneration.

2. Strategies

From January 2010 to October 2022, we conducted a literature search on the PubMed, ScienceDirect, and Web of Science databases, involving keywords such as “pulp regeneration”, “bioactive scaffold”, “regeneration microenvironment”, and “angiogenesis” to summarize strategies for creating a pulp regeneration microenvironment; 718 research articles were retrieved after removing duplicate records. Due to the wide range of retrieval and different methods for measuring the experimental research results, it is challenging to compare articles with each other to form a systematic literature review. Therefore, our review mainly includes 146 research articles on dental pulp regeneration microenvironmental scaffolds for a comprehensive narrative review, focusing on constructing bioactive scaffolds and their biological effects.

2.1. Natural and Naturally Derived Biomaterials

Many biological materials derived from natural tissues or cells have been reported, such as sodium alginate, gelatin, and collagen, which have been widely utilized in regenerative tissue engineering [39]. Here we will introduce some innovative, newly reported, tissue-specific bioactive materials that achieve satisfactory results through simple treatment.

2.1.1. Decellularized Extracellular Matrix

Decellularized extracellular matrix (dECM) refers to biological materials formed by human or animal tissues or organs through decellularized methods [40]. Decellularized muscle matrix biomaterials were first reported in 1948; scientists have gradually deepened their research correlated with dECM in recent years [41,42,43,44,45]. Some dECM materials are FDA-approved, such as AlloDerm® for skin repair [46]. Decellularized extracellular matrix refers to a kind of 3D culture framework that contains many extracellular macromolecules, including collagen, elastin, fibronectin, and matricellular proteins, creating a perfect regeneration microenvironment [47]. Furthermore, it retains some physicochemical properties and signal molecules obtained from the original tissues and provides a favorable carrier for recellularization [48]. Consequently, dECM has promising application prospects in damaged organ repair and tissue regeneration.
Decellularized pulp matrix from humans, swine, bovines, and rats have been experimented with using hypotonic or surfactant methods, exhibiting satisfactory decellularization efficiency [49,50,51,52,53]. Decellularized pulp retains major extracellular matrix components, such as type I collagen, type III collagen, laminin, and fibronectin [50]. Moreover, it contains some bioactive factors, including transforming growth factor β (TGF-β), dentin matrix protein 1 (DMP-1), and dentin sialoprotein (DSP) [51]. Furthermore, it retains the vascular structure and vascular endothelial growth factor (VEGF) and increases the relative mRNA expression level of angiogenesis markers during the treatment of recellularization [54]. Conditioned medium made from decellularized scaffolds can ameliorate the proliferation and migration ability of DPSCs, and the animal model of dental pulp regeneration demonstrates ideal results [51,54,55,56,57]. Decellularized pulp matrix also enhanced the odontogenic differentiation ability of DPSCs with high BMP4 expression with the help of recombinant adenovirus [58]. Considering the loss of extracellular matrix components during the acellular process, some researchers modified the decellularized dental pulp matrix materials with laminin, a kind of extracellular matrix protein, which exhibits more advantages in odontogenic differentiation [59]. Moreover, other soft tissue components of teeth, such as the tooth bud, indicate promising pulp regeneration potential after decellularized treatment [60,61,62].
Furthermore, the hydrogel derived from bone decellularized matrix showed a similar ability to promote odontogenic differentiation [63]. According to the related report, bovine bone tissue was treated to form 5 wt% dECM solution after decellularized treatment; then, the solution was mixed with DPSCs as part of the bio-ink to conduct 3D printing. As confirmed by experiments in vitro and in vivo, this 3D printing material has the characteristics of promoting bone/tooth differentiation [64]. Human amniotic tissue, rich in bioactive factors, forms a gel scaffold after decellularization that can sufficiently support the directional differentiation of DPSCs [65].
Apart from the description mentioned above, DPSCs-derived extracellular matrix has been reported. As revealed by relevant reports, such a matrix can enhance the mineralization level of dental pulp stem cells or gingival fibroblasts [66,67,68]. Regarding application, DPSCs can be seeded on another material, cultured for some time, and then treated with a decellularized method to form the decellularized composite material. For instance, DPSCs were cultured in a collagen/chitosan hydrogel for 2 weeks or grown on 3D-printed porous polylactic acid scaffolds for 7 days and then were decellularized [69,70]. These dECM-composites had favorable effects, indicating their potential application in pulp regeneration. DPSCs-derived extracellular matrix combined with colloidal microgels also enhanced the expression level of odontogenic genes in DPSCs [71]. Similarly, the extracellular matrix derived from other stem cells, such as stem cells from exfoliated deciduous teeth (SHEDs) or periodontal ligament stem cells (PDLSCs), also improved the mineralization ability of DPSCs [72].
The decellularized pulp matrix is obtained from the dental pulp tissue after decellularization, which retains most of the microstructures of the pulp tissue, carries some bioactive factors related to dental pulp regeneration, and largely preserves the original microenvironment of dental pulp cells, showing good potential for promoting pulp regeneration using bioactive scaffolds for the growth, proliferation, and differentiation of stem cells in clinical pulp regenerative therapy, despite the lack of clinical trial evidence to confirm it. Nonetheless, decellularized extracellular matrix materials have minor shortcomings, such as their complex steps, disinfection, batch-to-batch variation, and toxicity of residual decellularized liquids, which require further improvements to meet the needs of clinical practice [48].

2.1.2. Treated Dentin Matrix

Treated dentin matrix (TDM) is made of dentin, the hard tissue that accounts for the most significant proportion of teeth after treatment with ethylenediaminetetraacetic acid (EDTA), which has a certain degree of demineralization, containing fully exposed dentin tubules and loose fiber bundles [73]. This material is abundant in proteins involved in dentin production, such as COL-1, DSP, TGF-β1, and DMP-1, suggesting that TDM can create a favorable microenvironment for dentin regeneration, confirmed by in vitro and in vivo experiments [74,75,76,77]. Further mechanistic studies revealed that the biological activity of TDM was achieved by regulating Wnt/β-catenin pathway [78]. SHEDs sheet-derived pellets with TDM are a promising strategy for pulp regeneration [79].
Treated dentin matrix paste (TDMP) could be used for pulp capping. TDMP could contribute to the odontogenic differentiation and create a more continuous dentin bridge in the dental pulp exposure model in miniature pigs [80]. Another improved TDM material, treated dentin matrix hydrogel, exhibited excellent results in direct capping [81,82]. TDM and stem cells have also been studied in periodontal tissue regeneration [83]. Apart from the previously introduced TDM (dentin treated with EDTA), lyophilized dentin had a similar effect [84].
Furthermore, a randomized controlled clinical trial involving 25 patients aged 7–12 years old with tooth avulsion caused by dental trauma also confirmed that decellularized dentin matrix combined with autologous DPSCs aggregates at the root of the tooth could effectively simulate the microenvironment of tooth development and support the continued root growth of young permanent teeth [85]. Similarly, TDM can also be used as a component of pulp-capping agent, which will play an influential role in direct or indirect pulp-capping clinical treatment.
In conclusion, the composition of TDM is similar to dentin, but its structure is looser than that of dentin. It contains and properly releases bioactive factors to create a microenvironment for pulp regeneration.

2.1.3. Exosomes

Exosomes are extracellular vesicles generated by cells and contain nucleic acids, proteins, lipids, and metabolites, which play a vital role in intercellular communication and microenvironment creation [86,87]. Some studies have revealed that exosomes derived from dental stem cells favor promoting dental pulp regeneration [88,89]. Huang et al. [90] first isolated and identified DSPC-derived exosomes, and then confirmed that other DPSCs could endocytose these exosomes to activate the P38 MAPK pathway and have an odontogenic differentiation effect on DPSCs, which was also validated in animal models. Aside from that, exosomes derived from Hertwig’s epithelial root sheath cells, SCAPs, SHEDs, and Schwann cells could give an impetus to regenerating pulp dentin complex tissue [91,92,93,94,95].
As was reported in the relevant study, DPSCs-derived exosomes can enhance the angiogenic capacity of HUVECs [96]. Apoptotic vesicles from SHEDs stimulated vascular endothelial cells through the transcription factor EB-autophagy pathway and exerted similar effects [97]. LPS-pretreated DPSCs-derived exosomes make efforts to propel odontogenic differentiation of Schwann cells. Because exosomes are in small quantities and difficult to store, type I collagen membranes and fibrin gels could be loaded with exosomes to better simulate the microenvironment for in vivo experiments, which exhibits promising clinical applications [90,98].
Due to the complex production and the difficulty in storing and transporting exosomes, there are currently no reports on clinical trials in dental pulp regeneration [99]. Since exosomes participate in and contribute to a better regenerative microenvironment, they are waiting for follow-up research progress to meet the needs of clinical treatment and play an active role in cell homing and promoting stem cell proliferation in pulp regenerative treatment.

2.1.4. Other Perspectives

Aside from the dECM, TDM, and exosomes mentioned above, other strategies utilize bioactive substances derived from natural ingredients to help create a microenvironment for regeneration.
Microvascular fragments isolated from adipose tissue ameliorated the vascularization and the dental pulp regeneration ability of DPSCs aggregates [100]. Regarding the construction of cell aggregates, Itoh et al. [101] scraped DPSCs from a culture plate. They filled the cell sheet in a gel model to obtain a rod-shaped 3D cell structure after culturing for 2 days, which then exhibited a satisfactory effect of dental pulp differentiation in related studies. In terms of clinical trials, 40 patients with pulp necrosis of young permanent teeth caused by tooth trauma were recruited. The researchers cultured DPSCs from autologous deciduous teeth to form aggregates and collected them into treated root canals. A two-year follow-up showed continuous development of tooth root and more blood flow signal through the ultrasound doppler test, which will be more widely used in clinical practice in the future [102]. There are problems in the preparation and application efficiency in forming cell aggregates, suggesting that a more extensive and convenient clinical application also needs better assistance from scaffold materials to achieve the curative effect of dental pulp regeneration.
As for platelets-derived bioactive substances, platelet lysates loaded with hyaluronic acid hydrogels or gelatin methacrylate (GelMA) microspheres also create a microenvironment to propel vascularized pulp regeneration [103,104]. Platelet-rich fibrin showed a more substantial regenerative potential of DPSCs, compared with platelet-rich plasma, mainly in LPS-induced inflammatory states, which has been confirmed by clinical trials of necrotic permanent teeth [105,106,107,108]. Studies have shown that placing autologous platelet-rich plasma or platelet-rich fibrin into the treated root canal could promote the continued development of the root apex of young permanent teeth, and it also promotes the restoration of pulp sensitivity to a certain extent when applied to mature permanent teeth with pulp necrosis [107,109,110].
Microvascular fragments, cell sheets, and blood component derivatives are abundant in bioactive factors, which can become part of the extracellular microenvironment to help regenerate dental pulp tissue.

2.2. Artificial Synthetic Material

Apart from the natural or naturally derived materials summarized above, synthetic materials can create a suitable microenvironment for tissue regeneration by assisting in 3D culture, simulating extracellular matrix, and loading bioactive factors.

2.2.1. Agents for Creating a 3D Environment

As illustrated by relevant studies, the 3D culture of DPSCs can ameliorate the multidirectional differentiation potential and improve the mineralization level, helping to maintain the in vivo microenvironment of stem cells [111,112]. On that account, we primarily introduce three novel strategies to realize 3D culture.

Self-Assembled Peptide Hydrogel

Self-assembled peptide hydrogel is a bioactive peptide motif that forms an ordered structure on a micro-scale through molecular self-assembly. It can simulate the system of natural extracellular matrix to a certain extent, encapsulate bioactive factors with satisfactory biocompatibility and degradability, and show a promising application in tissue engineering [113,114]. Meanwhile, it is easy to achieve a 3D culture of cells because it is performed by self-assembling peptide motifs through non-covalent interactions [115].
Commercialized self-assembled peptide hydrogel, Puramatrix (RADA16-I), has been reported in dental pulp regeneration. For instance, DPSCs cultured in Puramatrix for 3 weeks could obtain odontogenic markers with high protein levels [116]. DPSCs alone or co-cultured with HUVECs in the same hydrogel exhibited vascularized pulp-like tissue in the subcutaneous model of nude mice for 4 weeks [117]. HIF-1α-stabilized SHEDs cultured in Puramatrix displayed ideal pulp regeneration effects in vivo and in vitro experiments [118]. Some researchers combined RAD with dentonin, a functional peptide motif of an extracellular phosphoglycoprotein, to form a functionalized self-assembling peptide hydrogel. As revealed by their research findings, it could give an impetus to the odontogenic differentiation of DPSCs [119]. Similarly, it has been reported that the self-assembled peptide hydrogels with RAD and VEGF mimetic epitopes have comparable results [120]. Using self-assembled hydrogels derived from the angiogenic peptide, SLan, to create an angiogenic niche has also been demonstrated to form dental pulp-like tissue in the canine orthotopic model [121]. Apart from that, the dentinogenic peptide is applied to self-assemble into hydrogels to support the growth of DPSCs, but it suffers from the problem of rapid degradation [122]. Similarly, self-assembled peptide hydrogels can cooperate with bioactive factors to create a pulp regeneration microenvironment. For instance, Mu et al. [123] constructed Puramatrix (RADA16-I) encapsulated with stem cell factor (SCF) to generate more blood vessel-like structures.

Microspheres

Microspheres are spherical polymeric networks with diameters ranging from about 100 to 400 microns, with sufficient oxygen diffusion capacity and a high surface area [124]. They can provide a 3D biomimetic environment and are commonly utilized in tissue regeneration and cell delivery [125]. As has been reported, different types of microspheres, such as nanofibrous spongy microspheres and gelatin methacrylate microspheres, were used to propel odontogenic differentiation of DPSCs and this achieved favorable results [126,127,128]. In line with related reports, unique microcapsules composed of co-encapsulation of DPSCs and HUVECs have been used for microstructural delivery in dental pulp regeneration [129,130].
Microspheres loaded with bioactive factors have also been reported, such as those containing the platelet lysates mentioned above [103]. The hierarchical nanofiber microsphere system loaded with VEGF or the gelatin methacrylate frozen gel microspheres loaded with simvastatin will be introduced in the following section of scaffold materials with bioactive factors [129,131,132].

3D Printing

Apart from self-assembled hydrogel or microsphere systems, 3D printing technology is suitable for creating a comfortable 3D environment for cell culture. Park et al. [133] incorporated BMP-2 simulated peptides into gelatin methacrylate bio-ink and found it could give an impetus to the odontogenic differentiation of DPSCs after 3D printing. Decellularized dentin matrix or calcium silicate could be applied as part of bio-ink for 3D printing, exhibiting satisfactory effects of promoting odontogenic regeneration [134,135].
Altogether, the 3D culture of DPSCs is still in the developing stage. Furthermore, building a dental pulp organoid model with a complex microenvironment is one of the goals of tissue engineering in the future, as was reported on the organoid models of the intestine, lung, and other structures [136,137].

2.2.2. Biomimetic Scaffolds

Because natural materials are limited by sources, costs, and mechanical properties, it is considered an excellent strategy to use bioactive materials that simulate extracellular matrix to provide an appropriate microenvironment. In line with research from Wang et al. [138], a poly-L-lactic acid nanofiber scaffold mimicking the structure of type I collagen can propel the odontogenic differentiation of DPSCs, showing a better effect if loaded with BMP-7. Similarly, Qu et al. [139] adopted nanostructured gelatin/bioactive glass to mimic collagen, which promoted the differentiation and biomineralization of DPSCs.
Moreover, a 3D tubular nanofiber matrix was created by adopting micropatterning technology to regulate the arrangement, migration, and differentiation of DPSCs, which helped obtain the dental pulp and dentin complex, which was analogous to the natural structure in the further in vivo experiments [140]. Based on the problem that DPSCs could not stably adhere to the root canal wall, some researchers, inspired by mussel adhesion, designed a dopamine-modified hyaluronic acid coating on the dentin surface to form an effective attachment bridge between DPSCs and dentin, which had a favorable performance on odontogenic differentiation ability [141]. Dopamine coating on the mineral trioxide aggregate (MTA) surface had a similar effect [142]. Consequently, biomimetic materials simulating extracellular matrix components or natural binding structures are widely used in tissue regeneration.

2.2.3. Scaffolds Loaded with Bioactive Factors

As described in the first part, dental pulp restoration and regeneration is regulated by a series of bioactive factors. Therefore, bioactive factors could be introduced to provide a regeneration microenvironment to improve stem cells’ proliferation and directional differentiation ability during tissue engineering. Since bioactive factors are mainly ions, peptides, and proteins, the scaffold loaded with bioactive factors is expected to have stable concentrations. This better and more lasting effect makes this strategy more applicable in tissue engineering.

Bioactive Factors

The following list (Table 1) contains the common bioactive factors that regulate dental pulp regeneration.

Scaffolds Loaded with Bioactive Factors

Given the complicated clinical situation, the release of bioactive factors needs to consider such issues as activity, concentration, and effect, so it is essential to use scaffolds with specific biological effects to load bioactive factors to play the leading role. The standard methods of scaffolding loaded with bioactive factors include surface presentation, encapsulation, and layer-by-layer assembly [170,171]. Different loading strategies were selected based on the characteristics of materials and biological activity of factors, which showed satisfactory results.
➀ Surface presentation
The surface presentation can be achieved by physical adsorption or chemical binding to create the ideal microenvironment due to the unique morphology, functional groups, and charge on the material’s surface.
Based on the microporous structure and adsorption properties, silk protein was used for physical absorption of SDF-1α and slowly released the factor within 24 h after loading, exhibiting a good pulp regeneration effect [165]. In line with the relevant report, researchers loaded collagen with BMP-7, injected it into the root canal, and then added DPSCs to the root tip to simulate endogenous stem cells. They found that it could stimulate cell migration and propel regeneration of vascularized pulp tissue in subcutaneously nude mice models [172]. The 50 mm diameter polydioxanone fibers containing VEGF exhibited a good angiogenic effect [173]. Another example of the synergistic effect of this material with some bioactive factors is chitosan and its derivatives scaffolds; they were loaded with simvastatin, displaying the ability to improve the odontogenic differentiation and mineralization of DPSCs [174,175,176]. Regarding chemical binding, chitosan-loaded calcium ions through coordination bond is a good example; they continued to release calcium ions for 21 days, displaying potential applications in dental tissue engineering [177]. Like calcium ions, strontium could become part of nano-bioactive glass through the ionic bond and can be slowly released from the material, facilitating dentin formation in vivo studies [178].
The binding of cytokines to materials through chemical bonding has not been reported in dental tissue engineering. Although the number of bioactive factors adsorbed on the physical surface is limited, the experimental results are comparatively ideal, which adequately exhibits its potential clinical application.
➁ Encapsulation and layer-by-layer assembly
Encapsulation is an intelligent strategy that can protect the bioactive factors from premature degradation [170]. Some scholars have made relevant attempts. TGF-β and FGF2 were coated with degradable lactide and ethyl lactide polymers to form microspheres to continuously release the two factors and facilitate the proliferation and migration ability of DPSCs [144]. Porous chitosan microspheres containing TGF-β1 showed more restorative dentin in the pulp-capping model than the control one [179]. Li et al. [131] prepared a hierarchical nanofiber microsphere system encapsulated with VEGF, which simulated the structure of natural collagen fibers at the nanoscale. As demonstrated by their research findings, the VEGF in the system could be released slowly and uniformly within 4 weeks. Moreover, vascularized regenerated pulp tissue was successfully formed, accounting for over two-thirds of the entire root canal in the subcutaneous semi-in situ model of nude mice.
The materials mentioned above are primarily loaded with bioactive factors through the strategies of surface presentation or encapsulation according to their surface properties, thereby forming a favorable microenvironment for dental pulp regeneration. Meanwhile, endogenous bioactive factors can be released through special treatment to play their biological roles. For instance, endogenous TGF-β could be activated and released through low-intensity laser or injectable alkaline gel treatments, which is conducive to stimulating the differentiation of pulp dentin of DPSCs [16,180]. Apart from the traditional methods of loading bioactive factors, we expect that there will be new strategies for the design of scaffolds loaded with bioactive factors to simulate the structure of the extracellular microenvironment as well as the temporal and spatial distribution of bioactive substances based on the latest physical and chemical principles, to meet the needs of clinical practices better.

3. Novel Perspectives of Pulp Regeneration

Tissue regeneration rests on the interactions among scaffolds, bioactive factors, and stem cells. The above studies primarily concentrate on natural and naturally derived materials and artificial synthetic materials that simulate a microenvironment by creating a 3D culture environment or loading bioactive factors. The following content introduces different strategies for pulp regeneration from a novel perspective to better supplement the potential of the regeneration microenvironment.

3.1. Changing Physical Conditions

The biological activities of tissue cells are regulated by physical signals, such as matrix stiffness, magnetism, and light, which have been attempted as additional interventions for tissue engineering [181].
As revealed by research conducted by Qu et al. [182], DPSCs formed mineralized tissue on a 3D NF-gelatin scaffold with a high-stiff surface and pulp-like tissues on a low-stiff structure. They first designed a scaffold structure with a low-stiffness inner core and a high-stiffness surface and simulated the actual structure of teeth. Then, the subcutaneous experiments in nude mice revealed that the pulp dentin composite-like structure was successfully generated.
The external magnetic field can modulate the behavior of stem cells. As indicated in related studies, static magnetic fields can ameliorate the proliferation, migration, and odontogenic differentiation ability of DPSCs through the activation of YAP/TAZ and p38 MAPK signaling pathways [183,184]. Some researchers have adopted magnetic fields to control the transportation and relative location of cells [185]. For example, DPSCs and HUVECs were labeled with magnetic nanoparticles and the two cells were assembled layer by layer under magnetic control. The experimental results showed that the functional vascular network could be formed within 3 days, providing a fundamental basis for pulp regeneration [186]. The synergistic effect of graphene and pulsed electromagnetic fields on DPSCs can implement their neurogenic differentiation [187]. Future attempts can also be made to construct scaffolds containing endogenous magnetic fields to propel odontogenic differentiation of DPSCs, as described in a report where the magnetic layer drove the osteogenic differentiation of MC3T3 cells [188].
Likewise, photobiomodulation and optogenetics have been introduced to use DPSCs for regeneration. As the primary method of photobiomodulation, the low-level laser can enhance the odontogenic differentiation ability of DPSCs and SCAPs on scaffolds [189,190]. Arany et al. [16] found that low-level laser could activate endogenous TGF-β1 through reactive oxygen species. The in vitro and rat pulp-capping model experiments demonstrated that activated TGF-βs could improve the odontogenic differentiation ability of DPSCs. Regarding optogenetic regulation, Niyazi et al. [191] have transfected the light-sensitive protein, channelrhodopsins, which could activate the CaMKIIa (a kind of protein involved in nerve cell function) in DPSCs. After optical stimulation for 5 days and 90 min per day, it can propel the neural differentiation of DPSCs. Furthermore, the photothermal effect of gold nanoparticles is also adopted to elevate the mitochondrial metabolism and energy supply levels, enhancing the odontogenic differentiation of DPSCs [192].
Furthermore, the 3D microgravity culture system’s construction positively improves the proliferation and odontogenic differentiation of DPSCs [193,194]. The above physical conditions, such as matrix stiffness, magnetic field, and light stimulation, can ameliorate the survival-promoting potential of the microenvironment. The specific biological regulation needs further exploration.

3.2. Antibacterial Material

Root canal environments expected to realize pulp regeneration in clinical practice may still have residual bacterial toxin components, which raises an antibacterial requirement for pro-regenerative scaffolds, including hydrogels, nanomaterials, microspheres, etc. For instance, Afami et al. [112] developed functionalized hydrogels with cell adhesion motifs for the 3D culture of DPSCs, which had antibacterial activity against common bacteria in the root canal. As was precisely described in relevant studies [195,196], a low concentration of graphene oxide-copper composites can give an impetus to odontogenic differentiation of DPSCs while inhibiting the formation of biofilm from Streptococcus mutans. Meanwhile, pulp-capping materials with antibacterial and dentin regeneration properties are in considerable demand. Calcium–zinc–silicon-based micro-nano spheres have advantageous antibacterial effects. In particular, they can lessen the release of pro-inflammatory factors from M1 macrophages and give an impetus to DPSCs’ odontogenic differentiation [197]. The antibacterial property is easy to ignore in tissue regeneration materials; how to skillfully achieve the balance between antibacterial and stem cell regeneration remains further discussed.

3.3. Other Novel Viewpoints

Cerium oxide has a favorable function of scavenging active oxygen. In consideration of these properties, researchers made cerium oxide nanoparticles. They found that they could be internalized into DPSCs to play an antioxidant role and ameliorate cell viability, showing their potential applications in dental pulp regeneration [198].
Oxygen is the fundamental prerequisite for cell proliferation and differentiation during tissue regeneration. Oxygen diffuses into every corner of the tissue through dissimilar types of blood vessels in human tissue, supporting cell survival and physiological functions. Reviewing the existing literature, the current strategies to propel angiogenesis predominantly use scaffold materials with or without bioactive factors, as mentioned. Similarly, the co-culture of vascular endothelial cells (ECs) and dental pulp stem cells (DPSCs) can heighten their ability for odontogenic differentiation and angiogenesis [199]. In accordance with the relevant report, microtissue spheroids composed of HUVECs and DPSCs could successfully form vascular pulp-like tissue in vivo after transplantation in animal models [200]. In addition, making oxygen-containing hydrogels is also a preferable choice. Zou et al. [201] produced a gelatin methacrylate (GelMA) hydrogel containing calcium peroxide to release oxygen in situ to ensure the average growth of SCAP under a hypoxic environment.
Unlike the above small-scale clinical trials of natural or natural-derived materials such as PRF and TDM, artificial synthetic materials must undergo more stringent demonstrations and plans. Currently, there is no relevant clinical trial report, and we are waiting for further research.

4. Summary

In conclusion, we first reviewed the primary process and participating elements involved in dental pulp development and restoration, indicating that the microenvironment is vital for tissue regeneration. The microenvironment is composed of surrounding cells, insoluble extracellular matrix, and soluble bioactive factors, each of which can affect the state of stem cells to some extent and can exert a specific influence on the construction of a suitable regenerative microenvironment.
From the viewpoint of creating a microenvironment that propels tissue regeneration, the above studies summarized three topics containing natural and naturally derived materials, synthetic materials, and novel perspectives applied to materials (Figure 2). Natural and naturally derived materials consist of decellularized extracellular matrix, treated dentin matrix, exosomes, and platelet derivatives, which can simulate the microenvironment of tissue for the most part. This has a preferable effect on odontogenic differentiation. Nevertheless, some problems need to be solved. For example, it is not easy to mass produce and achieves homogenization between different batches. Artificial materials can overcome some of these problems quickly. Synthetic materials mainly consist of 3D culture scaffolds, biomimetic scaffolds, and bioactive factor-loading scaffolds, which primarily simulate the microenvironment by creating 3D culture conditions, imitating the morphology of the extracellular matrix or loading bioactive factors to help achieve pulp regeneration. As for novel perspectives, it contains materials or conditions that change the physical environment, have antibacterial effects, and elevate the oxygen content of tissue, which exhibits promising prospects in achieving pulp regeneration.
We put forth some strategies to assist in creating a microenvironment, hoping to inspire subsequent research on pulp regeneration. We look forward to more inspiring, practical, and clinically applicable strategies for pulp regeneration in the future.

Author Contributions

Conceptualization, N.H. and J.W.; methodology, N.H. and W.L.; data curation, W.J.; writing—original draft preparation, N.H.; essay—review and editing, N.H. and W.J.; supervision, J.W. and S.G.; project administration, S.G.; funding acquisition, S.G. All authors have read and agreed to the published version of the manuscript.

Funding

This research was funded by the Natural Science Foundation of Shanghai, grant number 20ZR1448700, and the Research Discipline fund from the Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, and the College of Stomatology, Shanghai Jiao Tong University, grant number KQYJXK2020.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

All data are included in this published review.

Conflicts of Interest

The authors declare no conflict of interest.

References

  1. Gulabivala, K.; Ng, Y.L. 1—Tooth organogenesis, morphology and physiology. In Endodontics (Fourth Edition); Gulabivala, K., Ng, Y.-L., Eds.; Mosby/Elsevier: Edinburgh, UK, 2014; pp. 2–32. [Google Scholar]
  2. Si, Y.; Tai, B.; Hu, D.; Lin, H.; Wang, B.; Wang, C.; Zheng, S.; Liu, X.; Rong, W.; Wang, W.; et al. Oral health status of Chinese residents and suggestions for prevention and treatment strategies. Glob. Health J. 2019, 3, 50–54. [Google Scholar] [CrossRef]
  3. Qin, X.; Zi, H.; Zeng, X. Changes in the global burden of untreated dental caries from 1990 to 2019: A systematic analysis for the Global Burden of Disease study. Heliyon 2022, 8, e10714. [Google Scholar] [CrossRef] [PubMed]
  4. Krastl, G.; Allgayer, N.; Lenherr, P.; Filippi, A.; Taneja, P.; Weiger, R. Tooth discoloration induced by endodontic materials: A literature review. Dent. Traumatol. 2013, 29, 2–7. [Google Scholar] [CrossRef] [PubMed]
  5. Zhang, C.; Yang, Z.; Hou, B. Diverse bacterial profile in extraradicular biofilms and periradicular lesions associated with persistent apical periodontitis. Int. Endod. J. 2021, 54, 1425–1433. [Google Scholar] [CrossRef] [PubMed]
  6. Ganesh, A.; Venkateshbabu, N.; John, A.; Deenadhayalan, G.; Kandaswamy, D. A comparative assessment of fracture resistance of endodontically treated and re-treated teeth: An in vitro study. J. Conserv. Dent. 2014, 17, 61–64. [Google Scholar] [CrossRef] [Green Version]
  7. Winters, J.; Cameron, A.C.; Widmer, R.P. 7—Pulp therapy for primary and immature permanent teeth. In Handbook of Pediatric Dentistry (Fourth Edition); Cameron, A.C., Widmer, R.P., Eds.; Mosby: Canberra, Australia, 2013; pp. 103–122. [Google Scholar]
  8. He, L.; Kim, S.G.; Gong, Q.; Zhong, J.; Wang, S.; Zhou, X.; Ye, L.; Ling, J.; Mao, J.J. Regenerative Endodontics for Adult Patients. J. Endod. 2017, 43, S57–S64. [Google Scholar] [CrossRef]
  9. Nanci, A. (Ed.) Chapter 5—Development of the Tooth and Its Supporting Tissues. In Ten Cate’s Oral Histology (Ninth Edition); Elsevier: St. Louis, MO, USA, 2016; pp. 68–83. [Google Scholar]
  10. Balic, A.; Thesleff, I. Chapter Seven—Tissue Interactions Regulating Tooth Development and Renewal. In Current Topics in Developmental Biology; Chai, Y., Ed.; Academic Press: Cambridge, MA, USA, 2015; Volume 115, pp. 157–186. [Google Scholar]
  11. Ilan Rotstein, D.; John, I.; Ingle, D. 2—Structure and Function of the Pulp–Dentin Complex. In Ingle’s Endodontics; PMPH USA, Limited: Hamilton, ON, Canada, 2019; pp. 59–84. [Google Scholar]
  12. Provenza, D.V. The blood vascular supply of the dental pulp with emphasis on capillary circulation. Circ. Res. 1958, 6, 213–218. [Google Scholar] [CrossRef] [Green Version]
  13. Iijima, T.; Zhang, J.Q. Three-dimensional wall structure and the innervation of dental pulp blood vessels. Microsc. Res. Tech. 2002, 56, 32–41. [Google Scholar] [CrossRef]
  14. Luukko, K.; Kettunen, P. Coordination of tooth morphogenesis and neuronal development through tissue interactions: Lessons from mouse models. Exp. Cell Res. 2014, 325, 72–77. [Google Scholar] [CrossRef]
  15. Yu, T.; Volponi, A.A.; Babb, R.; An, Z.; Sharpe, P.T. Chapter Eight—Stem Cells in Tooth Development, Growth, Repair, and Regeneration. In Current Topics in Developmental Biology; Chai, Y., Ed.; Academic Press: Cambridge, MA, USA, 2015; Volume 115, pp. 187–212. [Google Scholar]
  16. Arany, P.R.; Cho, A.; Hunt, T.D.; Sidhu, G.; Shin, K.; Hahm, E.; Huang, G.X.; Weaver, J.; Chen, A.C.; Padwa, B.L.; et al. Photoactivation of endogenous latent transforming growth factor-β1 directs dental stem cell differentiation for regeneration. Sci. Transl. Med. 2014, 6, 238ra269. [Google Scholar] [CrossRef]
  17. He, P.; Zheng, L.; Zhou, X. IGFs in Dentin Formation and Regeneration: Progress and Remaining Challenges. Stem Cells Int. 2022, 2022, 3737346. [Google Scholar] [CrossRef]
  18. Sagomonyants, K.; Kalajzic, I.; Maye, P.; Mina, M. Enhanced Dentinogenesis of Pulp Progenitors by Early Exposure to FGF2. J. Dent. Res. 2015, 94, 1582–1590. [Google Scholar] [CrossRef] [Green Version]
  19. Kim, S.; Liu, M.; Simchon, S.; Dörscher-Kim, J.E. Effects of selected inflammatory mediators on blood flow and vascular permeability in the dental pulp. Proc. Finn. Dent. Soc. 1992, 88 (Suppl. 1), 387–392. [Google Scholar]
  20. Bletsa, A.; Berggreen, E.; Fristad, I.; Tenstad, O.; Wiig, H. Cytokine signalling in rat pulp interstitial fluid and transcapillary fluid exchange during lipopolysaccharide-induced acute inflammation. J. Physiol. 2006, 573, 225–236. [Google Scholar] [CrossRef]
  21. Hoeben, A.; Landuyt, B.; Highley, M.S.; Wildiers, H.; Van Oosterom, A.T.; De Bruijn, E.A. Vascular endothelial growth factor and angiogenesis. Pharm. Rev. 2004, 56, 549–580. [Google Scholar] [CrossRef] [Green Version]
  22. Rombouts, C.; Giraud, T.; Jeanneau, C.; About, I. Pulp Vascularization during Tooth Development, Regeneration, and Therapy. J. Dent. Res. 2017, 96, 137–144. [Google Scholar] [CrossRef]
  23. Saghiri, M.A.; Asatourian, A.; Sorenson, C.M.; Sheibani, N. Role of Angiogenesis in Endodontics: Contributions of Stem Cells and Proangiogenic and Antiangiogenic Factors to Dental Pulp Regeneration. J. Endod. 2015, 41, 797–803. [Google Scholar] [CrossRef] [Green Version]
  24. Gomez-Sosa, J.F.; Cardier, J.E.; Caviedes-Bucheli, J. The hypoxia-dependent angiogenic process in dental pulp. J. Oral Biosci. 2022, 64, 381–391. [Google Scholar] [CrossRef]
  25. Luukko, K.; Kettunen, P.; Fristad, I.; Berggreen, E. Chapter 12—Structure and Functions of the Dentin-Pulp Complex. In Cohen’s Pathways of the Pulp (Tenth Edition); Hargreaves, K.M., Cohen, S., Eds.; Mosby: St. Louis, MO, USA, 2011; pp. 452–503. [Google Scholar]
  26. Aslankoohi, N.; Mondal, D.; Rizkalla, A.S.; Mequanint, K. Bone Repair and Regenerative Biomaterials: Towards Recapitulating the Microenvironment. Polymers 2019, 11, 1437. [Google Scholar] [CrossRef] [Green Version]
  27. Lumelsky, N. Creating a Pro-Regenerative Tissue Microenvironment: Local Control is the Key. Front. Bioeng. Biotechnol. 2021, 9, 712685. [Google Scholar] [CrossRef]
  28. Kaushik, S.N.; Kim, B.; Walma, A.M.; Choi, S.C.; Wu, H.; Mao, J.J.; Jun, H.W.; Cheon, K. Biomimetic microenvironments for regenerative endodontics. Biomater. Res. 2016, 20, 14. [Google Scholar] [CrossRef] [PubMed]
  29. Gronthos, S.; Brahim, J.; Li, W.; Fisher, L.W.; Cherman, N.; Boyde, A.; DenBesten, P.; Robey, P.G.; Shi, S. Stem Cell Properties of Human Dental Pulp Stem Cells. J. Dent. Res. 2002, 81, 531–535. [Google Scholar] [CrossRef] [PubMed]
  30. Cordeiro, M.M.; Dong, Z.; Kaneko, T.; Zhang, Z.; Miyazawa, M.; Shi, S.; Smith, A.J.; Nör, J.E. Dental Pulp Tissue Engineering with Stem Cells from Exfoliated Deciduous Teeth. J. Endod. 2008, 34, 962–969. [Google Scholar] [CrossRef] [PubMed]
  31. Sonoyama, W.; Liu, Y.; Yamaza, T.; Tuan, R.S.; Wang, S.; Shi, S.; Huang, G.T. Characterization of the apical papilla and its residing stem cells from human immature permanent teeth: A pilot study. J. Endod. 2008, 34, 166–171. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  32. De Souza Araújo, I.J.; Münchow, E.A.; Tootla, S.; Bottino, M.C. Chapter 13—Dental pulp tissue regeneration. In Tissue Engineering; Sharma, C.P., Chandy, T., Thomas, V., Thankam, F.G., Eds.; Academic Press: Cambridge, MA, USA, 2022; pp. 313–346. [Google Scholar]
  33. Smith, J.G.; Smith, A.J.; Shelton, R.M.; Cooper, P.R. Dental Pulp Cell Behavior in Biomimetic Environments. J. Dent. Res. 2015, 94, 1552–1559. [Google Scholar] [CrossRef]
  34. Krebs, N.J.; Neville, C.; Vacanti, J.P. 12—Cellular Transplants for Liver Diseases. In Cellular Transplantation; Halberstadt, C., Emerich, D., Eds.; Academic Press: Burlington, MA, USA, 2007; pp. 215–240. [Google Scholar]
  35. Hoffman, B.D.; Grashoff, C.; Schwartz, M.A. Dynamic molecular processes mediate cellular mechanotransduction. Nature 2011, 475, 316–323. [Google Scholar] [CrossRef]
  36. Collins, K.L.; Gates, E.M.; Gilchrist, C.L.; Hoffman, B.D. Chapter 1—Bio-Instructive Cues in Scaffolds for Musculoskeletal Tissue Engineering and Regenerative Medicine. In Bio-Instructive Scaffolds for Musculoskeletal Tissue Engineering and Regenerative Medicine; Brown, J.L., Kumbar, S.G., Banik, B.L., Eds.; Academic Press: Cambridge, MA, USA, 2017; pp. 3–35. [Google Scholar]
  37. Sui, B.; Chen, C.; Kou, X.; Li, B.; Xuan, K.; Shi, S.; Jin, Y. Pulp Stem Cell-Mediated Functional Pulp Regeneration. J. Dent. Res. 2019, 98, 27–35. [Google Scholar] [CrossRef]
  38. Xie, Z.; Shen, Z.; Zhan, P.; Yang, J.; Huang, Q.; Huang, S.; Chen, L.; Lin, Z. Functional Dental Pulp Regeneration: Basic Research and Clinical Translation. Int. J. Mol. Sci. 2021, 22, 8991. [Google Scholar] [CrossRef]
  39. Moussa, D.G.; Aparicio, C. Present and future of tissue engineering scaffolds for dentin-pulp complex regeneration. J. Tissue Eng. Regen. Med. 2019, 13, 58–75. [Google Scholar] [CrossRef] [Green Version]
  40. Taylor, D.A.; Sampaio, L.C.; Ferdous, Z.; Gobin, A.S.; Taite, L.J. Decellularized matrices in regenerative medicine. Acta Biomater. 2018, 74, 74–89. [Google Scholar] [CrossRef]
  41. Poel, W.E. Preparation of Acellular Homogenates from Muscle Samples. Science 1948, 108, 390–391. [Google Scholar] [CrossRef]
  42. Smoak, M.M.; Hogan, K.J.; Grande-Allen, K.J.; Mikos, A.G. Bioinspired electrospun dECM scaffolds guide cell growth and control the formation of myotubes. Sci. Adv. 2021, 7, eabg4123. [Google Scholar] [CrossRef]
  43. Cao, H.; Wang, X.; Chen, M.; Liu, Y.; Cui, X.; Liang, J.; Wang, Q.; Fan, Y.; Zhang, X. Childhood Cartilage ECM Enhances the Chondrogenesis of Endogenous Cells and Subchondral Bone Repair of the Unidirectional Collagen-dECM Scaffolds in Combination with Microfracture. ACS Appl. Mater. Interfaces 2021, 13, 57043–57057. [Google Scholar] [CrossRef]
  44. Kim, J.W.; Nam, S.A.; Yi, J.; Kim, J.Y.; Lee, J.Y.; Park, S.Y.; Sen, T.; Choi, Y.M.; Lee, J.Y.; Kim, H.L.; et al. Kidney Decellularized Extracellular Matrix Enhanced the Vascularization and Maturation of Human Kidney Organoids. Adv. Sci. 2022, 9, e2103526. [Google Scholar] [CrossRef]
  45. Yao, Q.; Zheng, Y.-W.; Lan, Q.-H.; Kou, L.; Xu, H.-L.; Zhao, Y.-Z. Recent development and biomedical applications of decellularized extracellular matrix biomaterials. Mater. Sci. Eng. C 2019, 104, 109942. [Google Scholar] [CrossRef]
  46. Juhasz, I.; Kiss, B.; Lukacs, L.; Erdei, I.; Peter, Z.; Remenyik, E. Long-term followup of dermal substitution with acellular dermal implant in burns and postburn scar corrections. Dermatol. Res. Pract. 2010, 2010, 210150. [Google Scholar] [CrossRef] [Green Version]
  47. Brown, M.; Li, J.; Moraes, C.; Tabrizian, M.; Li-Jessen, N.Y.K. Decellularized extracellular matrix: New promising and challenging biomaterials for regenerative medicine. Biomaterials 2022, 289, 121786. [Google Scholar] [CrossRef]
  48. Zhang, X.; Chen, X.; Hong, H.; Hu, R.; Liu, J.; Liu, C. Decellularized extracellular matrix scaffolds: Recent trends and emerging strategies in tissue engineering. Bioact. Mater. 2022, 10, 15–31. [Google Scholar] [CrossRef]
  49. Matoug-Elwerfelli, M.; Nazzal, H.; Raif, E.M.; Wilshaw, S.P.; Esteves, F.; Duggal, M. Ex-vivo recellularisation and stem cell differentiation of a decellularised rat dental pulp matrix. Sci. Rep. 2020, 10, 21553. [Google Scholar] [CrossRef]
  50. Matoug-Elwerfelli, M.; Duggal, M.S.; Nazzal, H.; Esteves, F.; Raïf, E. A biocompatible decellularized pulp scaffold for regenerative endodontics. Int. Endod. J. 2018, 51, 663–673. [Google Scholar] [CrossRef]
  51. Alqahtani, Q.; Zaky, S.H.; Patil, A.; Beniash, E.; Ray, H.; Sfeir, C. Decellularized Swine Dental Pulp Tissue for Regenerative Root Canal Therapy. J. Dent. Res. 2018, 97, 1460–1467. [Google Scholar] [CrossRef] [PubMed]
  52. Bakhtiar, H.; Pezeshki-Modaress, M.; Kiaipour, Z.; Shafiee, M.; Ellini, M.R.; Mazidi, A.; Rajabi, S.; Zamanlui Benisi, S.; Ostad, S.N.; Galler, K.; et al. Pulp ECM-derived macroporous scaffolds for stimulation of dental-pulp regeneration process. Dent. Mater. 2020, 36, 76–87. [Google Scholar] [CrossRef] [PubMed]
  53. Bakhtiar, H.; Rajabi, S.; Pezeshki-Modaress, M.; Ellini, M.R.; Panahinia, M.; Alijani, S.; Mazidi, A.; Kamali, A.; Azarpazhooh, A.; Kishen, A. Optimizing Methods for Bovine Dental Pulp Decellularization. J. Endod. 2021, 47, 62–68. [Google Scholar] [CrossRef] [PubMed]
  54. Alghutaimel, H.; Yang, X.; Drummond, B.; Nazzal, H.; Duggal, M.; Raïf, E. Investigating the vascularization capacity of a decellularized dental pulp matrix seeded with human dental pulp stem cells: In vitro and preliminary in vivo evaluations. Int. Endod. J. 2021, 54, 1300–1316. [Google Scholar] [CrossRef] [PubMed]
  55. Hu, L.; Gao, Z.; Xu, J.; Zhu, Z.; Fan, Z.; Zhang, C.; Wang, J.; Wang, S. Decellularized Swine Dental Pulp as a Bioscaffold for Pulp Regeneration. Biomed Res. Int. 2017, 2017, 9342714. [Google Scholar] [CrossRef]
  56. Kim, I.H.; Jeon, M.; Cheon, K.; Kim, S.H.; Jung, H.S.; Shin, Y.; Kang, C.M.; Kim, S.O.; Choi, H.J.; Lee, H.S.; et al. In Vivo Evaluation of Decellularized Human Tooth Scaffold for Dental Tissue Regeneration. Appl. Sci. 2021, 11, 8472. [Google Scholar] [CrossRef]
  57. Song, J.S.; Takimoto, K.; Jeon, M.; Vadakekalam, J.; Ruparel, N.B.; Diogenes, A. Decellularized Human Dental Pulp as a Scaffold for Regenerative Endodontics. J. Dent. Res. 2017, 96, 640–646. [Google Scholar] [CrossRef]
  58. Tan, Q.; Cao, Y.; Zheng, X.; Peng, M.; Huang, E.; Wang, J. BMP4-regulated human dental pulp stromal cells promote pulp-like tissue regeneration in a decellularized dental pulp matrix scaffold. Odontology 2021, 109, 895–903. [Google Scholar] [CrossRef]
  59. Fu, J.; Chen, J.; Li, W.; Yang, X.; Yang, J.; Quan, H.; Huang, H.; Chen, G. Laminin-Modified Dental Pulp Extracellular Matrix for Dental Pulp Regeneration. Front. Bioeng. Biotechnol. 2020, 8, 595096. [Google Scholar] [CrossRef]
  60. Zhang, W.; Vazquez, B.; Oreadi, D.; Yelick, P.C. Decellularized Tooth Bud Scaffolds for Tooth Regeneration. J. Dent. Res. 2017, 96, 516–523. [Google Scholar] [CrossRef] [Green Version]
  61. Oshima, M.; Mizuno, M.; Imamura, A.; Ogawa, M.; Yasukawa, M.; Yamazaki, H.; Morita, R.; Ikeda, E.; Nakao, K.; Takano-Yamamoto, T.; et al. Functional tooth regeneration using a bioengineered tooth unit as a mature organ replacement regenerative therapy. PLoS ONE 2011, 6, e21531. [Google Scholar] [CrossRef]
  62. Traphagen, S.B.; Fourligas, N.; Xylas, J.F.; Sengupta, S.; Kaplan, D.L.; Georgakoudi, I.; Yelick, P.C. Characterization of natural, decellularized and reseeded porcine tooth bud matrices. Biomaterials 2012, 33, 5287–5296. [Google Scholar] [CrossRef] [Green Version]
  63. Paduano, F.; Marrelli, M.; White, L.J.; Shakesheff, K.M.; Tatullo, M. Odontogenic Differentiation of Human Dental Pulp Stem Cells on Hydrogel Scaffolds Derived from Decellularized Bone Extracellular Matrix and Collagen Type I. PLoS ONE 2016, 11, e0148225. [Google Scholar] [CrossRef] [Green Version]
  64. Kim, D.; Lee, H.; Lee, G.H.; Hoang, T.H.; Kim, H.R.; Kim, G.H. Fabrication of bone-derived decellularized extracellular matrix/ceramic-based biocomposites and their osteo/odontogenic differentiation ability for dentin regeneration. Bioeng. Transl. Med. 2022, 7, e10317. [Google Scholar] [CrossRef]
  65. Bakhtiar, H.; Ashoori, A.; Rajabi, S.; Pezeshki-Modaress, M.; Ayati, A.; Mousavi, M.R.; Ellini, M.R.; Kamali, A.; Azarpazhooh, A.; Kishen, A. Human amniotic membrane extracellular matrix scaffold for dental pulp regeneration in vitro and in vivo. Int. Endod. J. 2022, 55, 374–390. [Google Scholar] [CrossRef]
  66. Nowwarote, N.; Petit, S.; Ferre, F.C.; Dingli, F.; Laigle, V.; Loew, D.; Osathanon, T.; Fournier, B.P.J. Extracellular Matrix Derived From Dental Pulp Stem Cells Promotes Mineralization. Front. Bioeng. Biotechnol. 2021, 9, 740712. [Google Scholar] [CrossRef]
  67. Zhang, X.; Li, H.; Sun, J.; Luo, X.; Yang, H.; Xie, L.; Yang, B.; Guo, W.; Tian, W. Cell-derived micro-environment helps dental pulp stem cells promote dental pulp regeneration. Cell Prolif. 2017, 50, e12361. [Google Scholar] [CrossRef] [Green Version]
  68. Huang, C.C.; Narayanan, R.; Warshawsky, N.; Ravindran, S. Dual ECM Biomimetic Scaffolds for Dental Pulp Regenerative Applications. Front. Physiol. 2018, 9, 495. [Google Scholar] [CrossRef]
  69. Alksne, M.; Kalvaityte, M.; Simoliunas, E.; Gendviliene, I.; Barasa, P.; Rinkunaite, I.; Kaupinis, A.; Seinin, D.; Rutkunas, V.; Bukelskiene, V. Dental pulp stem cell-derived extracellular matrix: Autologous tool boosting bone regeneration. Cytotherapy 2022, 24, 597–607. [Google Scholar] [CrossRef]
  70. Ravindran, S.; Zhang, Y.; Huang, C.C.; George, A. Odontogenic induction of dental stem cells by extracellular matrix-inspired three-dimensional scaffold. Tissue Eng. Part A 2014, 20, 92–102. [Google Scholar] [CrossRef]
  71. Aksel, H.; Sarkar, D.; Lin, M.H.; Buck, A.; Huang, G.T.J. Cell-derived Extracellular Matrix Proteins in Colloidal Microgel as a Self-Assembly Hydrogel for Regenerative Endodontics. J. Endod. 2022, 48, 527–534. [Google Scholar] [CrossRef] [PubMed]
  72. Heng, B.C.; Zhu, S.; Xu, J.; Yuan, C.; Gong, T.; Zhang, C. Effects of decellularized matrices derived from periodontal ligament stem cells and SHED on the adhesion, proliferation and osteogenic differentiation of human dental pulp stem cells in vitro. Tissue Cell 2016, 48, 133–143. [Google Scholar] [CrossRef] [PubMed]
  73. Grawish, M.E.; Grawish, L.M.; Grawish, H.M.; Grawish, M.M.; Holiel, A.A.; Sultan, N.; El-Negoly, S.A. Demineralized Dentin Matrix for Dental and Alveolar Bone Tissues Regeneration: An Innovative Scope Review. Tissue Eng. Regen. Med. 2022, 19, 687–701. [Google Scholar] [CrossRef] [PubMed]
  74. Guo, W.; He, Y.; Zhang, X.; Lu, W.; Wang, C.; Yu, H.; Liu, Y.; Li, Y.; Zhou, Y.; Zhou, J.; et al. The use of dentin matrix scaffold and dental follicle cells for dentin regeneration. Biomaterials 2009, 30, 6708–6723. [Google Scholar] [CrossRef] [PubMed]
  75. Li, R.; Guo, W.; Yang, B.; Guo, L.; Sheng, L.; Chen, G.; Li, Y.; Zou, Q.; Xie, D.; An, X.; et al. Human treated dentin matrix as a natural scaffold for complete human dentin tissue regeneration. Biomaterials 2011, 32, 4525–4538. [Google Scholar] [CrossRef]
  76. Li, J.; Yang, H.; Lu, Q.; Chen, D.; Zhou, M.; Kuang, Y.; Ying, S.; Song, J. Proteomics and N-glycoproteomics analysis of an extracellular matrix-based scaffold-human treated dentin matrix. J. Tissue Eng. Regen. Med. 2019, 13, 1164–1177. [Google Scholar] [CrossRef]
  77. Chang, C.C.; Lin, T.A.; Wu, S.Y.; Lin, C.P.; Chang, H.H. Regeneration of Tooth with Allogenous, Autoclaved Treated Dentin Matrix with Dental Pulpal Stem Cells: An In Vivo Study. J. Endod. 2020, 46, 1256–1264. [Google Scholar] [CrossRef]
  78. Liu, S.; Sun, J.; Yuan, S.; Yang, Y.; Gong, Y.; Wang, Y.; Guo, R.; Zhang, X.; Liu, Y.; Mi, H.; et al. Treated dentin matrix induces odontogenic differentiation of dental pulp stem cells via regulation of Wnt/β-catenin signaling. Bioact. Mater. 2022, 7, 85–97. [Google Scholar] [CrossRef]
  79. Na, S.; Zhang, H.; Huang, F.; Wang, W.; Ding, Y.; Li, D.; Jin, Y. Regeneration of dental pulp/dentine complex with a three-dimensional and scaffold-free stem-cell sheet-derived pellet. J. Tissue Eng. Regen. Med 2016, 10, 261–270. [Google Scholar] [CrossRef]
  80. Chen, J.; Cui, C.; Qiao, X.; Yang, B.; Yu, M.; Guo, W.; Tian, W. Treated dentin matrix paste as a novel pulp capping agent for dentin regeneration. J. Tissue Eng. Regen. Med. 2017, 11, 3428–3436. [Google Scholar] [CrossRef]
  81. Holiel, A.A.; Mahmoud, E.M.; Abdel-Fattah, W.M.; Kawana, K.Y. Histological evaluation of the regenerative potential of a novel treated dentin matrix hydrogel in direct pulp capping. Clin. Oral Investig. 2021, 25, 2101–2112. [Google Scholar] [CrossRef]
  82. Holiel, A.A.; Mahmoud, E.M.; Abdel-Fattah, W.M. Tomographic evaluation of direct pulp capping using a novel injectable treated dentin matrix hydrogel: A 2-year randomized controlled clinical trial. Clin. Oral Investig. 2021, 25, 4621–4634. [Google Scholar] [CrossRef]
  83. Yang, X.; Ma, Y.; Guo, W.; Yang, B.; Tian, W. Stem cells from human exfoliated deciduous teeth as an alternative cell source in bio-root regeneration. Theranostics 2019, 9, 2694–2711. [Google Scholar] [CrossRef]
  84. Wang, F.; Xie, C.; Ren, N.; Bai, S.; Zhao, Y. Human Freeze-dried Dentin Matrix as a Biologically Active Scaffold for Tooth Tissue Engineering. J. Endod. 2019, 45, 1321–1331. [Google Scholar] [CrossRef]
  85. Guo, H.; Li, B.; Wu, M.; Zhao, W.; He, X.; Sui, B.; Dong, Z.; Wang, L.; Shi, S.; Huang, X.; et al. Odontogenesis-related developmental microenvironment facilitates deciduous dental pulp stem cell aggregates to revitalize an avulsed tooth. Biomaterials 2021, 279, 121223. [Google Scholar] [CrossRef]
  86. Kalluri, R.; LeBleu, V.S. The biology, function, and biomedical applications of exosomes. Science 2020, 367, eaau6977. [Google Scholar] [CrossRef]
  87. Tang, Y.; Zhou, Y.; Li, H.J. Advances in mesenchymal stem cell exosomes: A review. Stem Cell Res. Ther. 2021, 12, 71. [Google Scholar] [CrossRef]
  88. Mai, Z.; Chen, H.; Ye, Y.; Hu, Z.; Sun, W.; Cui, L.; Zhao, X. Translational and Clinical Applications of Dental Stem Cell-Derived Exosomes. Front. Genet. 2021, 12, 750990. [Google Scholar] [CrossRef]
  89. Chen, Y.; Ma, Y.; Yang, X.; Chen, J.; Yang, B.; Tian, W. The Application of Pulp Tissue Derived-Exosomes in Pulp Regeneration: A Novel Cell-Homing Approach. Int. J. Nanomed. 2022, 17, 465–476. [Google Scholar] [CrossRef]
  90. Huang, C.C.; Narayanan, R.; Alapati, S.; Ravindran, S. Exosomes as biomimetic tools for stem cell differentiation: Applications in dental pulp tissue regeneration. Biomaterials 2016, 111, 103–115. [Google Scholar] [CrossRef] [Green Version]
  91. Li, J.; Ju, Y.; Liu, S.; Fu, Y.; Zhao, S. Exosomes derived from lipopolysaccharide-preconditioned human dental pulp stem cells regulate Schwann cell migration and differentiation. Connect. Tissue Res. 2021, 62, 277–286. [Google Scholar] [CrossRef] [PubMed]
  92. Zhuang, X.; Ji, L.; Jiang, H.; Liu, Y.; Liu, X.; Bi, J.; Zhao, W.; Ding, Z.; Chen, X. Exosomes Derived from Stem Cells from the Apical Papilla Promote Dentine-Pulp Complex Regeneration by Inducing Specific Dentinogenesis. Stem Cells Int. 2020, 2020, 5816723. [Google Scholar] [CrossRef] [PubMed]
  93. Wu, M.; Liu, X.; Li, Z.; Huang, X.; Guo, H.; Guo, X.; Yang, X.; Li, B.; Xuan, K.; Jin, Y. SHED aggregate exosomes shuttled miR-26a promote angiogenesis in pulp regeneration via TGF-β/SMAD2/3 signalling. Cell Prolif. 2021, 54, e13074. [Google Scholar] [CrossRef] [PubMed]
  94. Liu, P.; Qin, L.; Liu, C.; Mi, J.; Zhang, Q.; Wang, S.; Zhuang, D.; Xu, Q.; Chen, W.; Guo, J.; et al. Exosomes Derived From Hypoxia-Conditioned Stem Cells of Human Deciduous Exfoliated Teeth Enhance Angiogenesis via the Transfer of let-7f-5p and miR-210-3p. Front. Cell Dev. Biol. 2022, 10, 879877. [Google Scholar] [CrossRef] [PubMed]
  95. Wang, D.; Lyu, Y.; Yang, Y.; Zhang, S.; Chen, G.; Pan, J.; Tian, W. Schwann cell-derived EVs facilitate dental pulp regeneration through endogenous stem cell recruitment via SDF-1/CXCR4 axis. Acta Biomater. 2022, 140, 610–624. [Google Scholar] [CrossRef]
  96. Xian, X.; Gong, Q.; Li, C.; Guo, B.; Jiang, H. Exosomes with Highly Angiogenic Potential for Possible Use in Pulp Regeneration. J. Endod. 2018, 44, 751–758. [Google Scholar] [CrossRef]
  97. Li, Z.; Wu, M.; Liu, S.; Liu, X.; Huan, Y.; Ye, Q.; Yang, X.; Guo, H.; Liu, A.; Huang, X.; et al. Apoptotic vesicles activate autophagy in recipient cells to induce angiogenesis and dental pulp regeneration. Mol. Ther. 2022, 30, 3193–3208. [Google Scholar] [CrossRef]
  98. Zhang, S.; Thiebes, A.L.; Kreimendahl, F.; Ruetten, S.; Buhl, E.M.; Wolf, M.; Jockenhoevel, S.; Apel, C. Extracellular Vesicles-Loaded Fibrin Gel Supports Rapid Neovascularization for Dental Pulp Regeneration. Int. J. Mol. Sci. 2020, 21, 4226. [Google Scholar] [CrossRef]
  99. Rezaie, J.; Feghhi, M.; Etemadi, T. A review on exosomes application in clinical trials: Perspective, questions, and challenges. Cell Commun. Signal. 2022, 20, 145. [Google Scholar] [CrossRef]
  100. Xu, X.; Liang, C.; Gao, X.; Huang, H.; Xing, X.; Tang, Q.; Yang, J.; Wu, Y.; Li, M.; Li, H.; et al. Adipose Tissue–derived Microvascular Fragments as Vascularization Units for Dental Pulp Regeneration. J. Endod. 2021, 47, 1092–1100. [Google Scholar] [CrossRef]
  101. Itoh, Y.; Sasaki, J.I.; Hashimoto, M.; Katata, C.; Hayashi, M.; Imazato, S. Pulp Regeneration by 3-dimensional Dental Pulp Stem Cell Constructs. J. Dent. Res. 2018, 97, 1137–1143. [Google Scholar] [CrossRef]
  102. Xuan, K.; Li, B.; Guo, H.; Sun, W.; Kou, X.; He, X.; Zhang, Y.; Sun, J.; Liu, A.; Liao, L.; et al. Deciduous autologous tooth stem cells regenerate dental pulp after implantation into injured teeth. Sci. Transl. Med. 2018, 10, aaf3227. [Google Scholar] [CrossRef] [Green Version]
  103. Zhang, Q.; Yang, T.; Zhang, R.; Liang, X.; Wang, G.; Tian, Y.; Xie, L.; Tian, W. Platelet lysate functionalized gelatin methacrylate microspheres for improving angiogenesis in endodontic regeneration. Acta Biomater. 2021, 136, 441–455. [Google Scholar] [CrossRef]
  104. Silva, C.R.; Babo, P.S.; Gulino, M.; Costa, L.; Oliveira, J.M.; Silva-Correia, J.; Domingues, R.M.A.; Reis, R.L.; Gomes, M.E. Injectable and tunable hyaluronic acid hydrogels releasing chemotactic and angiogenic growth factors for endodontic regeneration. Acta Biomater. 2018, 77, 155–171. [Google Scholar] [CrossRef] [Green Version]
  105. Chai, J.; Jin, R.; Yuan, G.; Kanter, V.; Miron, R.J.; Zhang, Y. Effect of Liquid Platelet-rich Fibrin and Platelet-rich Plasma on the Regenerative Potential of Dental Pulp Cells Cultured under Inflammatory Conditions: A Comparative Analysis. J. Endod. 2019, 45, 1000–1008. [Google Scholar] [CrossRef]
  106. Rizk, H.M.; Salah Al-Deen, M.S.M.; Emam, A.A. Comparative evaluation of Platelet Rich Plasma (PRP) versus Platelet Rich Fibrin (PRF) scaffolds in regenerative endodontic treatment of immature necrotic permanent maxillary central incisors: A double blinded randomized controlled trial. Saudi Dent. J. 2020, 32, 224–231. [Google Scholar] [CrossRef]
  107. Nageh, M.; Ahmed, G.M.; El-Baz, A.A. Assessment of Regaining Pulp Sensibility in Mature Necrotic Teeth Using a Modified Revascularization Technique with Platelet-rich Fibrin: A Clinical Study. J. Endod. 2018, 44, 1526–1533. [Google Scholar] [CrossRef]
  108. Kim, J.-H.; Woo, S.-M.; Choi, N.-K.; Kim, W.-J.; Kim, S.-M.; Jung, J.-Y. Effect of Platelet-rich Fibrin on Odontoblastic Differentiation in Human Dental Pulp Cells Exposed to Lipopolysaccharide. J. Endod. 2017, 43, 433–438. [Google Scholar] [CrossRef]
  109. ElSheshtawy, A.S.; Nazzal, H.; El Shahawy, O.I.; El Baz, A.A.; Ismail, S.M.; Kang, J.; Ezzat, K.M. The effect of platelet-rich plasma as a scaffold in regeneration/revitalization endodontics of immature permanent teeth assessed using 2-dimensional radiographs and cone beam computed tomography: A randomized controlled trial. Int. Endod. J. 2020, 53, 905–921. [Google Scholar] [CrossRef]
  110. Rahul, M.; Lokade, A.; Tewari, N.; Mathur, V.; Agarwal, D.; Goel, S.; Keshari, P.; Sharma, S.; Bansal, K. Effect of intracanal scaffolds on the success outcomes of Regenerative Endodontic Therapy—A systematic review and meta-analysis. J. Endod. 2022. [Google Scholar] [CrossRef]
  111. Son, Y.B.; Bharti, D.; Kim, S.B.; Jo, C.H.; Bok, E.Y.; Lee, S.L.; Kang, Y.H.; Rho, G.J. Comparison of Pluripotency, Differentiation, and Mitochondrial Metabolism Capacity in Three-Dimensional Spheroid Formation of Dental Pulp-Derived Mesenchymal Stem Cells. Biomed Res. Int. 2021, 2021, 5540877. [Google Scholar] [CrossRef] [PubMed]
  112. Afami, M.E.; El Karim, I.; About, I.; Krasnodembskaya, A.D.; Laverty, G.; Lundy, F.T. Multicomponent Peptide Hydrogels as an Innovative Platform for Cell-Based Tissue Engineering in the Dental Pulp. Pharmaceutics 2021, 13, 1575. [Google Scholar] [CrossRef]
  113. Fu, K.; Wu, H.; Su, Z. Self-assembling peptide-based hydrogels: Fabrication, properties, and applications. Biotechnol. Adv. 2021, 49, 107752. [Google Scholar] [CrossRef] [PubMed]
  114. Han, C.; Zhang, Z.; Sun, J.; Li, K.; Li, Y.; Ren, C.; Meng, Q.; Yang, J. Self-Assembling Peptide-Based Hydrogels in Angiogenesis. Int. J. Nanomed. 2020, 15, 10257–10269. [Google Scholar] [CrossRef] [PubMed]
  115. Chen, J.; Zou, X. Self-assemble peptide biomaterials and their biomedical applications. Bioact. Mater. 2019, 4, 120–131. [Google Scholar] [CrossRef]
  116. Cavalcanti, B.N.; Zeitlin, B.D.; Nör, J.E. A hydrogel scaffold that maintains viability and supports differentiation of dental pulp stem cells. Dent. Mater. 2013, 29, 97–102. [Google Scholar] [CrossRef] [Green Version]
  117. Dissanayaka, W.L.; Hargreaves, K.M.; Jin, L.; Samaranayake, L.P.; Zhang, C. The interplay of dental pulp stem cells and endothelial cells in an injectable peptide hydrogel on angiogenesis and pulp regeneration in vivo. Tissue Eng. Part A 2015, 21, 550–563. [Google Scholar] [CrossRef] [Green Version]
  118. Han, Y.; Koohi-Moghadam, M.; Chen, Q.; Zhang, L.; Chopra, H.; Zhang, J.; Dissanayaka, W.L. HIF-1α Stabilization Boosts Pulp Regeneration by Modulating Cell Metabolism. J. Dent. Res. 2022, 101, 1214–1226. [Google Scholar] [CrossRef]
  119. Liu, Y.; Fan, L.; Lin, X.; Zou, L.; Li, Y.; Ge, X.; Fu, W.; Zhang, Z.; Xiao, K.; Lv, H. Functionalized self-assembled peptide RAD/Dentonin hydrogel scaffold promotes dental pulp regeneration. Biomed. Mater. 2021, 17, 015009. [Google Scholar] [CrossRef]
  120. Xia, K.; Chen, Z.; Chen, J.; Xu, H.; Xu, Y.; Yang, T.; Zhang, Q. RGD- and VEGF-Mimetic Peptide Epitope-Functionalized Self-Assembling Peptide Hydrogels Promote Dentin-Pulp Complex Regeneration. Int. J. Nanomed. 2020, 15, 6631–6647. [Google Scholar] [CrossRef]
  121. Siddiqui, Z.; Sarkar, B.; Kim, K.K.; Kadincesme, N.; Paul, R.; Kumar, A.; Kobayashi, Y.; Roy, A.; Choudhury, M.; Yang, J.; et al. Angiogenic hydrogels for dental pulp revascularization. Acta Biomater. 2021, 126, 109–118. [Google Scholar] [CrossRef]
  122. Nguyen, P.K.; Gao, W.; Patel, S.D.; Siddiqui, Z.; Weiner, S.; Shimizu, E.; Sarkar, B.; Kumar, V.A. Self-Assembly of a Dentinogenic Peptide Hydrogel. ACS Omega 2018, 3, 5980–5987. [Google Scholar] [CrossRef]
  123. Mu, X.; Shi, L.; Pan, S.; He, L.; Niu, Y.; Wang, X. A Customized Self-Assembling Peptide Hydrogel-Wrapped Stem Cell Factor Targeting Pulp Regeneration Rich in Vascular-Like Structures. ACS Omega 2020, 5, 16568–16574. [Google Scholar] [CrossRef]
  124. Leong, W.; Wang, D.A. Cell-laden Polymeric Microspheres for Biomedical Applications. Trends Biotechnol. 2015, 33, 653–666. [Google Scholar] [CrossRef]
  125. Li, Q.; Chang, B.; Dong, H.; Liu, X. Functional microspheres for tissue regeneration. Bioact. Mater. 2022. [Google Scholar] [CrossRef]
  126. Kuang, R.; Zhang, Z.; Jin, X.; Hu, J.; Gupte, M.J.; Ni, L.; Ma, P.X. Nanofibrous spongy microspheres enhance odontogenic differentiation of human dental pulp stem cells. Adv. Healthc. Mater. 2015, 4, 1993–2000. [Google Scholar] [CrossRef] [Green Version]
  127. Kuang, R.; Zhang, Z.; Jin, X.; Hu, J.; Shi, S.; Ni, L.; Ma, P.X. Nanofibrous spongy microspheres for the delivery of hypoxia-primed human dental pulp stem cells to regenerate vascularized dental pulp. Acta Biomater. 2016, 33, 225–234. [Google Scholar] [CrossRef] [Green Version]
  128. Yang, T.; Zhang, Q.; Xie, L.; Zhang, R.; Qian, R.; Tian, Y.; Chen, G.; Tian, W. hDPSC-laden GelMA microspheres fabricated using electrostatic microdroplet method for endodontic regeneration. Mater. Sci. Eng. C Mater. Biol. Appl. 2021, 121, 111850. [Google Scholar] [CrossRef]
  129. Liang, X.; Xie, L.; Zhang, Q.; Wang, G.; Zhang, S.; Jiang, M.; Zhang, R.; Yang, T.; Hu, X.; Yang, Z.; et al. Gelatin methacryloyl-alginate core-shell microcapsules as efficient delivery platforms for prevascularized microtissues in endodontic regeneration. Acta Biomater. 2022, 144, 242–257. [Google Scholar] [CrossRef]
  130. Zhang, R.; Xie, L.; Wu, H.; Yang, T.; Zhang, Q.; Tian, Y.; Liu, Y.; Han, X.; Guo, W.; He, M.; et al. Alginate/laponite hydrogel microspheres co-encapsulating dental pulp stem cells and VEGF for endodontic regeneration. Acta Biomater. 2020, 113, 305–316. [Google Scholar] [CrossRef]
  131. Li, X.; Ma, C.; Xie, X.; Sun, H.; Liu, X. Pulp regeneration in a full-length human tooth root using a hierarchical nanofibrous microsphere system. Acta Biomater. 2016, 35, 57–67. [Google Scholar] [CrossRef] [PubMed]
  132. Yuan, X.; Yuan, Z.; Wang, Y.; Wan, Z.; Wang, X.; Yu, S.; Han, J.; Huang, J.; Xiong, C.; Ge, L.; et al. Vascularized pulp regeneration via injecting simvastatin functionalized GelMA cryogel microspheres loaded with stem cells from human exfoliated deciduous teeth. Mater. Today Bio 2022, 13, 100209. [Google Scholar] [CrossRef] [PubMed]
  133. Park, J.H.; Gillispie, G.J.; Copus, J.S.; Zhang, W.; Atala, A.; Yoo, J.J.; Yelick, P.C.; Lee, S.J. The effect of BMP-mimetic peptide tethering bioinks on the differentiation of dental pulp stem cells (DPSCs) in 3D bioprinted dental constructs. Biofabrication 2020, 12, 035029. [Google Scholar] [CrossRef] [PubMed]
  134. Han, J.; Jeong, W.; Kim, M.K.; Nam, S.H.; Park, E.K.; Kang, H.W. Demineralized Dentin Matrix Particle-Based Bio-Ink for Patient-Specific Shaped 3D Dental Tissue Regeneration. Polymers 2021, 13, 1294. [Google Scholar] [CrossRef] [PubMed]
  135. Lin, Y.T.; Hsu, T.T.; Liu, Y.W.; Kao, C.T.; Huang, T.H. Bidirectional Differentiation of Human-Derived Stem Cells Induced by Biomimetic Calcium Silicate-Reinforced Gelatin Methacrylate Bioink for Odontogenic Regeneration. Biomedicines 2021, 9, 929. [Google Scholar] [CrossRef]
  136. Clevers, H. Modeling Development and Disease with Organoids. Cell 2016, 165, 1586–1597. [Google Scholar] [CrossRef] [Green Version]
  137. Nikolaev, M.; Mitrofanova, O.; Broguiere, N.; Geraldo, S.; Dutta, D.; Tabata, Y.; Elci, B.; Brandenberg, N.; Kolotuev, I.; Gjorevski, N.; et al. Homeostatic mini-intestines through scaffold-guided organoid morphogenesis. Nature 2020, 585, 574–578. [Google Scholar] [CrossRef]
  138. Wang, J.; Liu, X.; Jin, X.; Ma, H.; Hu, J.; Ni, L.; Ma, P.X. The odontogenic differentiation of human dental pulp stem cells on nanofibrous poly(L-lactic acid) scaffolds in vitro and in vivo. Acta Biomater. 2010, 6, 3856–3863. [Google Scholar] [CrossRef] [Green Version]
  139. Qu, T.; Liu, X. Nano-Structured Gelatin/Bioactive Glass Hybrid Scaffolds for the Enhancement of Odontogenic Differentiation of Human Dental Pulp Stem Cells. J. Mater. Chem. B 2013, 1, 4764–4772. [Google Scholar] [CrossRef] [Green Version]
  140. Ma, C.; Qu, T.; Chang, B.; Jing, Y.; Feng, J.Q.; Liu, X. 3D Maskless Micropatterning for Regeneration of Highly Organized Tubular Tissues. Adv. Healthc. Mater. 2018, 7, 1700738. [Google Scholar] [CrossRef]
  141. Liu, Y.; Qiu, Y.; Ni, S.; Zhang, X.; Sun, H.; Song, W.; Li, X. Mussel-Inspired Biocoating for Improving the Adhesion of Dental Pulp Stem Cells in Dental Pulp Regeneration. Macromol. Rapid Commun. 2020, 41, e2000102. [Google Scholar] [CrossRef]
  142. Tu, M.G.; Ho, C.C.; Hsu, T.T.; Huang, T.H.; Lin, M.J.; Shie, M.Y. Mineral Trioxide Aggregate with Mussel-inspired Surface Nanolayers for Stimulating Odontogenic Differentiation of Dental Pulp Cells. J. Endod. 2018, 44, 963–970. [Google Scholar] [CrossRef]
  143. He, H.; Yu, J.; Liu, Y.; Lu, S.; Liu, H.; Shi, J.; Jin, Y. Effects of FGF2 and TGFbeta1 on the differentiation of human dental pulp stem cells in vitro. Cell Biol. Int. 2008, 32, 827–834. [Google Scholar] [CrossRef]
  144. Mathieu, S.; Jeanneau, C.; Sheibat-Othman, N.; Kalaji, N.; Fessi, H.; About, I. Usefulness of controlled release of growth factors in investigating the early events of dentin-pulp regeneration. J. Endod. 2013, 39, 228–235. [Google Scholar] [CrossRef]
  145. Zhang, Y.; Liu, J.; Zou, T.; Qi, Y.; Yi, B.; Dissanayaka, W.L.; Zhang, C. DPSCs treated by TGF-β1 regulate angiogenic sprouting of three-dimensionally co-cultured HUVECs and DPSCs through VEGF-Ang-Tie2 signaling. Stem Cell Res. Ther. 2021, 12, 281. [Google Scholar] [CrossRef]
  146. Iohara, K.; Nakashima, M.; Ito, M.; Ishikawa, M.; Nakasima, A.; Akamine, A. Dentin regeneration by dental pulp stem cell therapy with recombinant human bone morphogenetic protein 2. J. Dent. Res. 2004, 83, 590–595. [Google Scholar] [CrossRef]
  147. Suzuki, T.; Lee, C.H.; Chen, M.; Zhao, W.; Fu, S.Y.; Qi, J.J.; Chotkowski, G.; Eisig, S.B.; Wong, A.; Mao, J.J. Induced migration of dental pulp stem cells for in vivo pulp regeneration. J. Dent. Res. 2011, 90, 1013–1018. [Google Scholar] [CrossRef]
  148. Li, S.; Hu, J.; Zhang, G.; Qi, W.; Zhang, P.; Li, P.; Zeng, Y.; Zhao, W.; Tan, Y. Extracellular Ca2+ Promotes Odontoblastic Differentiation of Dental Pulp Stem Cells via BMP2-Mediated Smad1/5/8 and Erk1/2 Pathways. J. Cell Physiol. 2015, 230, 2164–2173. [Google Scholar] [CrossRef]
  149. Kong, Y.; Hu, X.; Zhong, Y.; Xu, K.; Wu, B.; Zheng, J. Magnesium-enriched microenvironment promotes odontogenic differentiation in human dental pulp stem cells by activating ERK/BMP2/Smads signaling. Stem Cell Res. Ther. 2019, 10, 378. [Google Scholar] [CrossRef]
  150. Vandomme, J.; Touil, Y.; Ostyn, P.; Olejnik, C.; Flamenco, P.; El Machhour, R.; Segard, P.; Masselot, B.; Bailliez, Y.; Formstecher, P.; et al. Insulin-like growth factor 1 receptor and p38 mitogen-activated protein kinase signals inversely regulate signal transducer and activator of transcription 3 activity to control human dental pulp stem cell quiescence, propagation, and differentiation. Stem Cells Dev. 2014, 23, 839–851. [Google Scholar] [CrossRef] [Green Version]
  151. Cui, D.; Xiao, J.; Zhou, Y.; Zhou, X.; Liu, Y.; Peng, Y.; Yu, Y.; Li, H.; Zhou, X.; Yuan, Q.; et al. Epiregulin enhances odontoblastic differentiation of dental pulp stem cells via activating MAPK signalling pathway. Cell Prolif. 2019, 52, e12680. [Google Scholar] [CrossRef] [PubMed]
  152. Zhang, M.; Jiang, F.; Zhang, X.; Wang, S.; Jin, Y.; Zhang, W.; Jiang, X. The Effects of Platelet-Derived Growth Factor-BB on Human Dental Pulp Stem Cells Mediated Dentin-Pulp Complex Regeneration. Stem Cells Transl. Med. 2017, 6, 2126–2134. [Google Scholar] [CrossRef] [PubMed]
  153. Mizuno, M.; Banzai, Y. Calcium ion release from calcium hydroxide stimulated fibronectin gene expression in dental pulp cells and the differentiation of dental pulp cells to mineralized tissue forming cells by fibronectin. Int. Endod. J. 2008, 41, 933–938. [Google Scholar] [CrossRef] [PubMed]
  154. Liu, Y.; Liu, N.; Na, J.; Li, C.; Yue, G.; Fan, Y.; Zheng, L. Wnt/β-catenin plays a dual function in calcium hydroxide induced proliferation, migration, osteogenic differentiation and mineralization in vitro human dental pulp stem cells. Int. Endod. J. 2022, 56, 92–102. [Google Scholar] [CrossRef] [PubMed]
  155. Huang, M.; Hill, R.G.; Rawlinson, S.C. Strontium (Sr) elicits odontogenic differentiation of human dental pulp stem cells (hDPSCs): A therapeutic role for Sr in dentine repair? Acta Biomater. 2016, 38, 201–211. [Google Scholar] [CrossRef]
  156. Kulthanaamondhita, P.; Kornsuthisopon, C.; Photichailert, S.; Manokawinchoke, J.; Limraksasin, P.; Osathanon, T. Specific microRNAs Regulate Dental Pulp Stem Cell Behavior. J. Endod. 2022, 48, 688–698. [Google Scholar] [CrossRef]
  157. Zheng, H.; Wang, N.; Li, L.; Ge, L.; Jia, H.; Fan, Z. miR-140-3p enhanced the osteo/odontogenic differentiation of DPSCs via inhibiting KMT5B under hypoxia condition. Int. J. Oral Sci. 2021, 13, 41. [Google Scholar] [CrossRef]
  158. Zeng, L.; Zhao, N.; Li, F.; Han, D.; Liu, Y.; Liu, H.; Sun, S.; Wang, Y.; Feng, H. miR-675 promotes odontogenic differentiation of human dental pulp cells by epigenetic regulation of DLX3. Exp. Cell Res. 2018, 367, 104–111. [Google Scholar] [CrossRef]
  159. Botero, T.M.; Son, J.S.; Vodopyanov, D.; Hasegawa, M.; Shelburne, C.E.; Nör, J.E. MAPK signaling is required for LPS-induced VEGF in pulp stem cells. J. Dent. Res. 2010, 89, 264–269. [Google Scholar] [CrossRef]
  160. Janebodin, K.; Zeng, Y.; Buranaphatthana, W.; Ieronimakis, N.; Reyes, M. VEGFR2-dependent angiogenic capacity of pericyte-like dental pulp stem cells. J. Dent. Res. 2013, 92, 524–531. [Google Scholar] [CrossRef]
  161. Gonzalez-King, H.; García, N.A.; Ontoria-Oviedo, I.; Ciria, M.; Montero, J.A.; Sepúlveda, P. Hypoxia Inducible Factor-1α Potentiates Jagged 1-Mediated Angiogenesis by Mesenchymal Stem Cell-Derived Exosomes. Stem Cells 2017, 35, 1747–1759. [Google Scholar] [CrossRef]
  162. Kolar, M.K.; Itte, V.N.; Kingham, P.J.; Novikov, L.N.; Wiberg, M.; Kelk, P. The neurotrophic effects of different human dental mesenchymal stem cells. Sci. Rep. 2017, 7, 12605. [Google Scholar] [CrossRef] [Green Version]
  163. Zhang, J.; Lian, M.; Cao, P.; Bao, G.; Xu, G.; Sun, Y.; Wang, L.; Chen, J.; Wang, Y.; Feng, G.; et al. Effects of Nerve Growth Factor and Basic Fibroblast Growth Factor Promote Human Dental Pulp Stem Cells to Neural Differentiation. Neurochem. Res. 2017, 42, 1015–1025. [Google Scholar] [CrossRef]
  164. Han, Q.; Wang, Q.; Wu, J.; Li, M.; Fang, Y.; Zhu, H.; Wang, X. Nell-1 promotes the neural-like differentiation of dental pulp cells. Biochem. Biophys. Res. Commun. 2019, 513, 515–521. [Google Scholar] [CrossRef]
  165. Yang, J.W.; Zhang, Y.F.; Wan, C.Y.; Sun, Z.Y.; Nie, S.; Jian, S.J.; Zhang, L.; Song, G.T.; Chen, Z. Autophagy in SDF-1α-mediated DPSC migration and pulp regeneration. Biomaterials 2015, 44, 11–23. [Google Scholar] [CrossRef]
  166. Li, M.; Sun, X.; Ma, L.; Jin, L.; Zhang, W.; Xiao, M.; Yu, Q. SDF-1/CXCR4 axis induces human dental pulp stem cell migration through FAK/PI3K/Akt and GSK3β/β-catenin pathways. Sci. Rep. 2017, 7, 40161. [Google Scholar] [CrossRef] [Green Version]
  167. Pan, S.; Dangaria, S.; Gopinathan, G.; Yan, X.; Lu, X.; Kolokythas, A.; Niu, Y.; Luan, X. SCF promotes dental pulp progenitor migration, neovascularization, and collagen remodeling—Potential applications as a homing factor in dental pulp regeneration. Stem Cell Rev. Rep. 2013, 9, 655–667. [Google Scholar] [CrossRef] [Green Version]
  168. Nakayama, H.; Iohara, K.; Hayashi, Y.; Okuwa, Y.; Kurita, K.; Nakashima, M. Enhanced regeneration potential of mobilized dental pulp stem cells from immature teeth. Oral Dis. 2017, 23, 620–628. [Google Scholar] [CrossRef]
  169. Murakami, M.; Horibe, H.; Iohara, K.; Hayashi, Y.; Osako, Y.; Takei, Y.; Nakata, K.; Motoyama, N.; Kurita, K.; Nakashima, M. The use of granulocyte-colony stimulating factor induced mobilization for isolation of dental pulp stem cells with high regenerative potential. Biomaterials 2013, 34, 9036–9047. [Google Scholar] [CrossRef] [Green Version]
  170. Chen, L.; Liu, J.; Guan, M.; Zhou, T.; Duan, X.; Xiang, Z. Growth Factor and Its Polymer Scaffold-Based Delivery System for Cartilage Tissue Engineering. Int. J. Nanomed. 2020, 15, 6097–6111. [Google Scholar] [CrossRef]
  171. De Witte, T.M.; Fratila-Apachitei, L.E.; Zadpoor, A.A.; Peppas, N.A. Bone tissue engineering via growth factor delivery: From scaffolds to complex matrices. Regen. Biomater. 2018, 5, 197–211. [Google Scholar] [CrossRef] [PubMed]
  172. Liang, C.; Liang, Q.; Xu, X.; Liu, X.; Gao, X.; Li, M.; Yang, J.; Xing, X.; Huang, H.; Tang, Q.; et al. Bone morphogenetic protein 7 mediates stem cells migration and angiogenesis: Therapeutic potential for endogenous pulp regeneration. Int. J. Oral Sci. 2022, 14, 38. [Google Scholar] [CrossRef] [PubMed]
  173. Yadlapati, M.; Biguetti, C.; Cavalla, F.; Nieves, F.; Bessey, C.; Bohluli, P.; Garlet, G.P.; Letra, A.; Fakhouri, W.D.; Silva, R.M. Characterization of a Vascular Endothelial Growth Factor-loaded Bioresorbable Delivery System for Pulp Regeneration. J. Endod. 2017, 43, 77–83. [Google Scholar] [CrossRef] [PubMed]
  174. Soares, D.G.; Anovazzi, G.; Bordini, E.A.F.; Zuta, U.O.; Silva Leite, M.L.A.; Basso, F.G.; Hebling, J.; de Souza Costa, C.A. Biological Analysis of Simvastatin-releasing Chitosan Scaffold as a Cell-free System for Pulp-dentin Regeneration. J. Endod. 2018, 44, 971–976.e971. [Google Scholar] [CrossRef] [Green Version]
  175. Soares, D.G.; Bordini, E.A.F.; Bronze-Uhle, E.S.; Cassiano, F.B.; Silva, I.S.P.; Gallinari, M.O.; Matheus, H.R.; Almeida, J.M.; Cintra, L.T.A.; Hebling, J.; et al. Chitosan-Calcium-Simvastatin Scaffold as an Inductive Cell-Free Platform. J. Dent. Res. 2021, 100, 1118–1126. [Google Scholar] [CrossRef]
  176. Soares, D.G.; Zhang, Z.; Mohamed, F.; Eyster, T.W.; de Souza Costa, C.A.; Ma, P.X. Simvastatin and nanofibrous poly(l-lactic acid) scaffolds to promote the odontogenic potential of dental pulp cells in an inflammatory environment. Acta Biomater. 2018, 68, 190–203. [Google Scholar] [CrossRef] [Green Version]
  177. Soares, D.G.; Bordini, E.A.F.; Cassiano, F.B.; Bronze-Uhle, E.S.; Pacheco, L.E.; Zabeo, G.; Hebling, J.; Lisboa-Filho, P.N.; Bottino, M.C.; de Souza Costa, C.A. Characterization of novel calcium hydroxide-mediated highly porous chitosan-calcium scaffolds for potential application in dentin tissue engineering. J. Biomed. Mater. Res. B Appl. Biomater. 2020, 108, 2546–2559. [Google Scholar] [CrossRef]
  178. Mandakhbayar, N.; El-Fiqi, A.; Lee, J.H.; Kim, H.W. Evaluation of Strontium-Doped Nanobioactive Glass Cement for Dentin-Pulp Complex Regeneration Therapy. ACS Biomater. Sci. Eng. 2019, 5, 6117–6126. [Google Scholar] [CrossRef]
  179. Li, F.; Liu, X.; Zhao, S.; Wu, H.; Xu, H.H. Porous chitosan bilayer membrane containing TGF-β1 loaded microspheres for pulp capping and reparative dentin formation in a dog model. Dent. Mater. 2014, 30, 172–181. [Google Scholar] [CrossRef]
  180. Wang, S.; Niu, Y.; Jia, P.; Liao, Z.; Guo, W.; Chaves, R.C.; Tran-Ba, K.H.; He, L.; Bai, H.; Sia, S.; et al. Alkaline activation of endogenous latent TGFβ1 by an injectable hydrogel directs cell homing for in situ complex tissue regeneration. Bioact. Mater. 2022, 15, 316–329. [Google Scholar] [CrossRef]
  181. Handorf, A.M.; Zhou, Y.; Halanski, M.A.; Li, W.J. Tissue stiffness dictates development, homeostasis, and disease progression. Organogenesis 2015, 11, 1–15. [Google Scholar] [CrossRef]
  182. Qu, T.; Jing, J.; Ren, Y.; Ma, C.; Feng, J.Q.; Yu, Q.; Liu, X. Complete pulpodentin complex regeneration by modulating the stiffness of biomimetic matrix. Acta Biomater. 2015, 16, 60–70. [Google Scholar] [CrossRef]
  183. Zheng, L.; Zhang, L.; Chen, L.; Jiang, J.; Zhou, X.; Wang, M.; Fan, Y. Static magnetic field regulates proliferation, migration, differentiation, and YAP/TAZ activation of human dental pulp stem cells. J. Tissue Eng. Regen. Med. 2018, 12, 2029–2040. [Google Scholar] [CrossRef]
  184. Lew, W.Z.; Feng, S.W.; Lin, C.T.; Huang, H.M. Use of 0.4-Tesla static magnetic field to promote reparative dentine formation of dental pulp stem cells through activation of p38 MAPK signalling pathway. Int. Endod. J. 2019, 52, 28–43. [Google Scholar] [CrossRef] [Green Version]
  185. Kamei, N.; Adachi, N.; Ochi, M. Magnetic cell delivery for the regeneration of musculoskeletal and neural tissues. Regen. Ther. 2018, 9, 116–119. [Google Scholar] [CrossRef]
  186. Lu, Y.; Yu, C.-H.; Yang, G.; Sun, N.; Jiang, F.; Zhou, M.; Wu, X.; Luo, J.; Huang, C.; Zhang, W.; et al. A Rapidly Magnetically Assembled Stem Cell Microtissue with “Hamburger” Architecture and Enhanced Vascularization Capacity. Bioact. Mater. 2021, 6, 3756–3765. [Google Scholar] [CrossRef]
  187. Madanagopal, T.T.; Tai, Y.K.; Lim, S.H.; Fong, C.H.; Cao, T.; Rosa, V.; Franco-Obregón, A. Pulsed electromagnetic fields synergize with graphene to enhance dental pulp stem cell-derived neurogenesis by selectively targeting TRPC1 channels. Eur. Cell Mater. 2021, 41, 216–232. [Google Scholar] [CrossRef]
  188. Zhuang, J.; Lin, S.; Dong, L.; Cheng, K.; Weng, W. Magnetically actuated mechanical stimuli on Fe3O4/mineralized collagen coatings to enhance osteogenic differentiation of the MC3T3-E1 cells. Acta Biomater. 2018, 71, 49–60. [Google Scholar] [CrossRef]
  189. Moreira, M.S.; Sarra, G.; Carvalho, G.L.; Gonçalves, F.; Caballero-Flores, H.V.; Pedroni, A.C.F.; Lascala, C.A.; Catalani, L.H.; Marques, M.M. Physical and Biological Properties of a Chitosan Hydrogel Scaffold Associated to Photobiomodulation Therapy for Dental Pulp Regeneration: An In Vitro and In Vivo Study. Biomed Res. Int. 2021, 2021, 6684667. [Google Scholar] [CrossRef]
  190. Theocharidou, A.; Bakopoulou, A.; Kontonasaki, E.; Papachristou, E.; Hadjichristou, C.; Bousnaki, M.; Theodorou, G.; Papadopoulou, L.; Kantiranis, N.; Paraskevopoulos, K.; et al. Odontogenic differentiation and biomineralization potential of dental pulp stem cells inside Mg-based bioceramic scaffolds under low-level laser treatment. Lasers Med. Sci. 2017, 32, 201–210. [Google Scholar] [CrossRef]
  191. Niyazi, M.; Zibaii, M.I.; Chavoshinezhad, S.; Hamidabadi, H.G.; Dargahi, L.; Bojnordi, M.N.; Alizadeh, R.; Heravi, M.; Karimi, H.; Hosseini, M.; et al. Neurogenic differentiation of human dental pulp stem cells by optogenetics stimulation. J. Chem. Neuroanat. 2020, 109, 101821. [Google Scholar] [CrossRef] [PubMed]
  192. Wang, J.; Qu, X.; Xu, C.; Zhang, Z.; Qi, G.; Jin, Y. Thermoplasmonic Regulation of the Mitochondrial Metabolic State for Promoting Directed Differentiation of Dental Pulp Stem Cells. Anal. Chem. 2022, 94, 9564–9571. [Google Scholar] [CrossRef] [PubMed]
  193. Li, Y.; He, L.; Pan, S.; Zhang, L.; Zhang, W.; Yi, H.; Niu, Y. Three-dimensional simulated microgravity culture improves the proliferation and odontogenic differentiation of dental pulp stem cell in PLGA scaffolds implanted in mice. Mol. Med. Rep. 2017, 15, 873–878. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  194. He, L.; Pan, S.; Li, Y.; Zhang, L.; Zhang, W.; Yi, H.; Song, C.; Niu, Y. Increased proliferation and adhesion properties of human dental pulp stem cells in PLGA scaffolds via simulated microgravity. Int. Endod. J. 2016, 49, 161–173. [Google Scholar] [CrossRef] [PubMed]
  195. Mao, M.; Zhang, W.; Huang, Z.; Huang, J.; Wang, J.; Li, W.; Gu, S. Graphene Oxide-Copper Nanocomposites Suppress Cariogenic Streptococcus mutans Biofilm Formation. Int. J. Nanomed. 2021, 16, 7727–7739. [Google Scholar] [CrossRef]
  196. Li, W.; Mao, M.; Hu, N.; Wang, J.; Huang, J.; Zhang, W.; Gu, S. A graphene oxide-copper nanocomposite for the regeneration of the dentin-pulp complex: An odontogenic and neurovascularization-inducing material. Chem. Eng. J. 2021, 417, 129299. [Google Scholar] [CrossRef]
  197. Li, Z.; Xie, K.; Yang, S.; Yu, T.; Xiao, Y.; Zhou, Y. Multifunctional Ca-Zn-Si-based micro-nano spheres with anti-infective, anti-inflammatory, and dentin regenerative properties for pulp capping application. J. Mater. Chem. B 2021, 9, 8289–8299. [Google Scholar] [CrossRef]
  198. Mahapatra, C.; Singh, R.K.; Lee, J.-H.; Jung, J.; Hyun, J.K.; Kim, H.-W. Nano-shape varied cerium oxide nanomaterials rescue human dental stem cells from oxidative insult through intracellular or extracellular actions. Acta Biomater. 2017, 50, 142–153. [Google Scholar] [CrossRef]
  199. Dissanayaka, W.L.; Zhan, X.; Zhang, C.; Hargreaves, K.M.; Jin, L.; Tong, E.H.Y. Coculture of Dental Pulp Stem Cells with Endothelial Cells Enhances Osteo-/Odontogenic and Angiogenic Potential In Vitro. J. Endod. 2012, 38, 454–463. [Google Scholar] [CrossRef]
  200. Dissanayaka, W.L.; Zhu, L.; Hargreaves, K.M.; Jin, L.; Zhang, C. Scaffold-free Prevascularized Microtissue Spheroids for Pulp Regeneration. J. Dent. Res. 2014, 93, 1296–1303. [Google Scholar] [CrossRef] [Green Version]
  201. Zou, T.; Jiang, S.; Zhang, Y.; Liu, J.; Yi, B.; Qi, Y.; Dissanayaka, W.L.; Zhang, C. In Situ Oxygen Generation Enhances the SCAP Survival in Hydrogel Constructs. J. Dent. Res. 2021, 100, 1127–1135. [Google Scholar] [CrossRef]
Pharmaceutics 15 00158 g001 550
Figure 1. A schematic picture showing the relationship between mesenchymal stem cells and their microenvironment: the special microenvironment is to mesenchymal stem cells what soil is to seeds. Seeds grow slowly into trees under the nourishment of the soil just as mesenchymal stem cells strive to develop in their microenvironment, aiming to reach the goal of tissue regeneration.
Figure 1. A schematic picture showing the relationship between mesenchymal stem cells and their microenvironment: the special microenvironment is to mesenchymal stem cells what soil is to seeds. Seeds grow slowly into trees under the nourishment of the soil just as mesenchymal stem cells strive to develop in their microenvironment, aiming to reach the goal of tissue regeneration.
Pharmaceutics 15 00158 g001
Pharmaceutics 15 00158 g002 550
Figure 2. Summary of strategies for creating a microenvironment for dental pulp regeneration.
Figure 2. Summary of strategies for creating a microenvironment for dental pulp regeneration.
Pharmaceutics 15 00158 g002
Table
Table 1. Various bioactive factors involved in dental pulp regeneration.
Table 1. Various bioactive factors involved in dental pulp regeneration.
Main FunctionBioactive FactorsRelated ArticlesNotes
Odontoblastic/Odontogenic differentiationTGF-β1[143,144,145]Angiogenesis
BMP2, BMP7[146,147,148,149]Extracellular Ca2+, Mg2+ can enhance their effects
FGF[18]Angiogenesis
IGF[17,150]Cell proliferation and migration
EREG[151]/
PDGF-BB[152]Migration capability
Ca2+[153,154]
Mg2+[149]/
Sr2+[155]/
miRNA[156]For example: miR-140-3p [157], miR-675 [158], etc.
AngiogenesisVEGF[159,160]/
HIF-1α[161]/
miRNA[93]For example: miR-26a (SHED)
NeurogenesisBDNF[162]/
bFGF + NGF[163]/
Nell-1[164]/
Chemotactic functionSDF-1α[95,165,166]Homing factors in dental pulp regeneration
SCF[166,167]
G-CSF[168,169]Ameliorate regeneration potential
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Hu, N.; Li, W.; Jiang, W.; Wen, J.; Gu, S. Creating a Microenvironment to Give Wings to Dental Pulp Regeneration—Bioactive Scaffolds. Pharmaceutics 2023, 15, 158. https://doi.org/10.3390/pharmaceutics15010158

AMA Style

Hu N, Li W, Jiang W, Wen J, Gu S. Creating a Microenvironment to Give Wings to Dental Pulp Regeneration—Bioactive Scaffolds. Pharmaceutics. 2023; 15(1):158. https://doi.org/10.3390/pharmaceutics15010158

Chicago/Turabian Style

Hu, Nan, Weiping Li, Wentao Jiang, Jin Wen, and Shensheng Gu. 2023. "Creating a Microenvironment to Give Wings to Dental Pulp Regeneration—Bioactive Scaffolds" Pharmaceutics 15, no. 1: 158. https://doi.org/10.3390/pharmaceutics15010158

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop