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Review

Mesenchymal Stem/Stromal Cells Microencapsulation for Cell Therapy

1
Department of Prosthodontics, Faculty of Dentistry, Cairo University, Giza 12613, Egypt
2
Department of Biochemistry, Faculty of Science, Alexandria University, Alexandria 21526, Egypt
3
Department of Surgery, Medical University of South Carolina, Charleston, SC 29425, USA
4
Ralph H. Johnson Veterans Affairs Medical Center, Charleston, SC 29401, USA
*
Authors to whom correspondence should be addressed.
Cells 2025, 14(3), 149; https://doi.org/10.3390/cells14030149
Submission received: 6 December 2024 / Revised: 11 January 2025 / Accepted: 16 January 2025 / Published: 21 January 2025
(This article belongs to the Section Stem Cells)

Abstract

:
Cell microencapsulation is one of the most studied strategies to overcome the challenges associated with the implementation of mesenchymal stem/stromal cells (MSCs) in vivo. This approach isolates/shields donor MSCs from the host immune system using a semipermeable membrane that allows for the diffusion of gases, nutrients, and therapeutics, but not host immune cells. As a result, microencapsulated MSCs survive and engraft better after infusion, and they can be delivered specifically to the targeted site. Additionally, microencapsulation enables the co-culture of MSCs with different types of cells in a three-dimensional (3D) environment, allowing for better cellular interaction. Alginate, collagen, and cellulose are the most popular materials, and air jet extrusion, microfluidics, and emulsion are the most used techniques for MSC cell encapsulation in the literature. These materials and techniques differ in the size range of the resultant microcapsules and their compatibility with the applied materials. This review discusses various materials and techniques used for the microencapsulation of MSCs. We also shed light on the recent findings in this field, the advantages and drawbacks of using encapsulated MSCs, and the in vivo translation of the microencapsulated MSCs in cell therapy.

1. Introduction

Mesenchymal stem/stromal cells (MSCs) are multipotent adult stem cells that can be derived from a variety of mammalian tissues, such as bone marrow, umbilical cord, and adipose tissue, among others [1,2,3]. Their importance originates from their ability to proliferate and differentiate into multiple types of cell lineages. Additionally, studies have shown that MSCs modulate host immunity by secreting immune modulators, including cytokines and growth factors, which could protect them from host immune rejection responses and apoptosis [4,5,6]. These unique characteristics make MSC therapy an attractive approach for cell therapy. However, many challenges still exist upon local or systemic infusion of MSCs, including rapid clearance from circulation, instant blood-mediated inflammatory reaction (IBMIR), and poor homing of exogenous MSC to the targeted sites, which can hamper their therapeutic efficacy [7].
Microencapsulation is a strategy of encapsulating implanted cells with a biomaterial fabricated from natural or synthetic polymers, which can act as a protective shield against the host immune response while allowing essential nutrients to pass to the cells. Hence, they provide a more favorable environment for the implanted cells to survive and grow while avoiding possible fibrosis [8,9]. In addition, microencapsulation is a means of holding and transporting the encapsulated cells to the target bodily site [10]. Major encapsulating materials that have been tested include alginate [11], collagen [12], and cellulose [13], among others.
Recently, investigators have tested the use of encapsulated MSCs as an alternative to traditionally used tissue regenerative medicine [14,15]. In some studies, MSCs were co-cultured with other cell types, including pancreatic islet-derived insulin-producing cells [16] and hepatocytes [17,18] to enhance the growth rate of the cultured cells and to provide higher regeneration capacity. Notably, microencapsulated MSCs hold great promise for tissue regeneration medicine, offering potential treatment for various chronic diseases, including cardiovascular [19] and liver failure [20,21], cancer [22], diabetes [16,23,24], and neurological disorders [25]. In this review, we discuss different materials and techniques used for their microencapsulation and preclinical applications of microencapsulated MSCs in cell therapy.

2. MSCs

MSCs are extensively employed in cell therapy due to their many beneficial attributes, such as their potential for self-renewal and differentiation into several lineages without ethical concerns. In addition, MSC therapy is safe, as the risk of teratoma formation and immunogenicity are modest to low [2,3]. MSCs can be isolated from various tissues, including bone marrow, adipose tissue, cord blood, placenta, lung, liver, and skin [4,26]. Consequently, MSCs can differentiate into several tissue forms, including bone, cartilage, muscle, fat, tendon, ligament, and other connective tissues [5]. MSCs must be treated with certain stimuli introduced in a particular sequence for this process to work. In vitro, MSC differentiation is also impacted by the cellular environment, such as hypoxia and inflammatory signals, in addition to the substrate characteristics. For example, it has been demonstrated that rigid culture surfaces promote osteogenesis, while soft gels enhance adipogenesis [27]. In addition, MSCs secrete numerous cytokines and growth factors, including interleukin-2 (IL-2), interleukin-8 (IL-8), monocyte chemotactic protein-1 (MCP-1), stromal-derived factor-1 (SDF-1), vascular endothelial growth factor (VEGF), and transforming growth factor-beta (TGF-β), which regulate the immune system along with numerous intercellular signaling pathways [28,29]. These secreted bioactive compounds can inhibit fibrosis and apoptosis and stimulate organotypic cells, hence boosting their activity [6]. MSCs can, therefore, influence diverse bodily processes and signaling pathways in addition to their differentiation capability.

3. Microencapsulation

Various types of biomaterials fabricated from natural or synthetic polymers have been extensively applied to fabricate artificial 3D scaffolds capable of holding, transporting, and protecting cells from the external environment [10,30]. These scaffolds should provide a supportive microenvironment for encapsulated cells that promotes cell survival, proliferation, and the controlled release of therapeutic substances. This has resulted in the development of numerous cell therapy strategies for drug and cell delivery, which are now employed in organ replacement, tissue engineering, and regenerative medicine [8,31,32]. One of these strategies is cell microencapsulation, which aims to overcome the obstacles associated with whole-organ graft rejection and the side-effects of immunomodulatory protocols or immunosuppressive drugs. Cell microencapsulation permits the implantation of both allogeneic and xenogeneic cells while isolating them from the host immune response using a semipermeable membrane that allows the diffusion of gases, nutrients, and therapeutics, but not host immune cells [31].
The scientific community is becoming increasingly interested in this cell-based technology because of its therapeutic potential in many disciplines other than organ replacement. The microencapsulation of cells can be used to release proteins and morphogens over an extended period [9], making it a promising platform for drug delivery. In addition, research has progressed toward designing and constructing active 3D scaffolds that may be used to monitor encapsulated cells [33] or to build biomimetic scaffolds by including peptides in the matrix that influence the destiny of enclosed cells [34]. Cell microencapsulation is considered a cost-effective approach for studying and promoting stem cell growth and differentiation in a 3D environment [14], and an efficient platform for cell retention and delivery in various anatomical sites [15,35]. Here, we discuss various materials and techniques used to microencapsulate MSCs.

4. Materials Used for MSC Microencapsulation

To deliver MSCs and preserve their viability and differentiation potential in damaged tissues, it is essential to replicate the in vivo microenvironment using 3D scaffolds. This approach maintains the diverse functions of cells within this 3D environment, including their phenotype, adhesion, metabolism, and response to soluble factors [36]. Furthermore, MSCs interact with other cells more effectively in a 3D environment than a 2D monolayer, enhancing co-culture outcomes and promoting cell growth and tissue regeneration. Microencapsulation is one of the primary techniques for stem cell tissue engineering, which attempts to preserve the survival, phenotype, and differentiation potential of MSCs [15,37]. Furthermore, microcapsules shield MSCs from the host immune response by controlling the exchange of chemical substances between the cells and their environment [38]. In addition, microencapsulation allows MSCs to be co-cultured with other cell types, such as islet cells [16] and hepatocytes [17,18].
Several polymers have been investigated for MSC microencapsulation in research studies. Some of these biomaterials have been tested in clinical settings (see reviews by Trucillo P et al. [39] and Li H et al. [40]); this section discusses the characteristics of these polymers and factors that influence their encapsulation efficiency (Table 1).

4.1. Alginate

Alginate is a popular polymer for MSC microencapsulation [11,41,42,43]. This block copolymer comprises subunits of mannuronic acid (M) and guluronic acid (G) [44]. A variety of alginate forms are currently available on the market. Several factors are critical in defining the characteristics and functionality of the polymer, including the M/G ratio, viscosity, purity, and permeability of alginate [42]. For instance, the swelling behavior and stability of microcapsules in the form of core-and-shell structure are highly related to the M/G content. Alginates with a higher G content (lower viscosity) exhibit higher stability and swell at lower rates when compared with high-M-content alginates. Meanwhile, there is no significant difference regarding cell viability or protection against immune cells between both types of alginates [11,41]. On the other hand, it has been reported that high-G-content alginate is less cell-biocompatible than high-M-content alginate, which has a higher swelling tendency that contributes to better cell biocompatibility [42]. Furthermore, the modification of alginate microcapsules by extracellular matrix proteins or their derivatives, such as RGD (Arg-Gly-Asp), can improve the potency of encapsulated cells because these adhesion ligands mimic the natural microenvironment of the engrafted cells [45].
The purity of alginate is also critical for its function as the innate immune system can detect pathogen-associated molecular patterns (PAMPs) in alginate preparations via pattern recognition receptors (PRRs) [46,47], resulting in proinflammatory cytokine production and detrimental anti-capsular immune responses [48]. Toll-like receptors (TLRs) on the cell surface or inside the cells are a type of PRR that recognize PAMPs. Despite rigorous purification, alginate polymers can still contain impurities such as lipopolysaccharides, which are recognized by TLR4 [49], peptidoglycan, and lipoteichoic acid, detected by TLR2 [46], and small molecular poly-M residues, which can be identified by both TLR2 and TLR4 [50]. Therefore, achieving high-quality alginate purification is crucial for ensuring the long-term survival of encapsulated cells.
The permeability of alginate capsules is reported to vary widely in the literature. Some studies indicate that proteins up to 250 kDa and polysaccharides up to 50 kDa can diffuse through alginate capsules [51]. In contrast, other studies suggest that their capsules are impermeable to proteins as small as 25 kDa [52]. This discrepancy may originate from differences in capsule production processes and cell encapsulation techniques, resulting in variations in the capsule’s biochemical properties and pore size. These variations have crucial implications as they affect the effectiveness of the technique, as encapsulated cells can produce immune mediators and respond to host-derived signals [38].

4.2. Collagen

Collagens are the most abundant form of animal protein and encompass a family of 28 distinct types. Each collagen type has at least one triple-helical domain. In vertebrates, these collagens are classified using Roman numbers (I–XXVIII). Most collagens are organized into supra-molecular assemblies within the extracellular matrix. Collagens are the most critical component of tissue structures and influence the mechanical characteristics, organization, and shape of the tissue. They regulate cellular processes, including cell proliferation, migration, and differentiation, by interacting with various receptor families [53]. Type 1 collagen is the most widely used collagen in cell microencapsulation due to its exceptional biological qualities to control the development of stem cells. They have been extensively utilized in different applications associated with bone [54,55,56], cartilage [13,57,58], liver [59], and skin regeneration [60].
On the other hand, collagen, like the other polysaccharide hydrogels, has notable drawbacks. For instance, it needs more robust mechanical qualities, and some may be difficult to manage owing to batch-to-batch variance. Polysaccharide hydrogels are frequently mixed with protein-based polymers to create composite or co-polymer hydrogels [15]. Collagen has been introduced into alginate microcapsules as it is a component of the extracellular matrix (ECM) that provides binding sites for cell adhesion to enhance cell proliferation or differentiation [59,60]. The combination of collagen with other polysaccharides, such as agarose [61] and chitosan [54], has also been reported.

4.3. Cellulose

Cellulose, a polysaccharide composed of several hundred to several thousand linked D-glucose units in a linear chain, has been explored for MSC microencapsulation [62,63]. Cellulose has many advantages in MSC encapsulation, including its superior biocompatibility, biodegradability, tunable properties, low cost, and renewability [63]. Carboxymethyl cellulose has shown promise in the microencapsulation of bone marrow-derived MSCs (BM-MSCs), with promising outcomes for controlling their osteogenic differentiation [62].
Silanized hydroxypropylmethyl cellulose (Si-HPMC) hydrogel has been used to microencapsulate adipose tissue-derived MSCs (ASCs). The findings demonstrated that Si-HPMC facilitates the nutrient exchange required for the survival of the encapsulated cells [64].

4.4. Agarose

In MSC therapy, agarose hydrogels have emerged as versatile materials for delivery, offering a promising platform for creating microenvironments that enhance MSC viability and function owing to their biocompatibility and adjustable mechanical properties. When combined with collagen, agarose has been shown to develop three-dimensional microenvironments that increase MSC survival and retention, and regulate cell development through regulated cell–matrix interactions [61]. Agarose-based hydrogels have also been modified to mitigate host immunological responses by incorporating immunosuppressive substances like Fas ligand (FasL). This strategy has been shown to increase MSC survival in traumatic brain injury models, promoting the expression of neurotrophic factors at the site of injury [65]. Additionally, optimizing agarose–alginate hydrogel formulations has enhanced encapsulation stability and made it easier to transfer viable MSCs, opening up possibilities for broader therapeutic applications [66]. Nevertheless, challenges remain, including limited bioactivity and the need for better degradation profiles. Further investigation has focused on incorporating bioactive components into agarose, which may improve its therapeutic effectiveness in regenerative medicine.

4.5. Chitosan

Chitosan-based hydrogels have gained significant interest in regenerative medicine due to their ability to facilitate MSC encapsulation, along with their biocompatibility and biodegradability. These hydrogels provide a biomimetic environment that improves MSC survival and paracrine activity, as well as their therapeutic potential. Injectable chitosan hydrogels, for example, have been used to support MSCs in spinal cord injury treatment. In addition to preserving MSC viability, these hydrogels facilitated the release of MSC-derived vesicles. They maintained their anti-inflammatory and antioxidant qualities, essential for preventing glial scarring and encouraging regeneration in spinal cord injury [67]. Furthermore, adding carboxymethyl chitosan to hydrogels improves MSC osteodifferentiation, enabling early osteogenesis and maturation without external differentiation factors [68]. Additionally, MSCs have been seeded onto macroporous calcium phosphate cement scaffolds using chitosan and β-glycerophosphate (C/GP) hydrogel, which protects the cells during scaffold creation and improves osteoconductivity [69]. These findings demonstrate the versatility of chitosan-based hydrogels as effective MSC delivery vehicles, providing viable options for tissue engineering and regenerative medicine.

4.6. Dextran

Hydrogels based on dextran are biomaterials that have attracted attention in tissue engineering and regenerative medicine due to their adaptability. A study used UC-MSCs and oxidized dextran combined with gelatin methacrylate to form injectable hydrogels with excellent biocompatibility and cell delivery capabilities in myocardial infarction treatment. This hydrogel promoted UC-MSC survival, proliferation, and differentiation into cardiac-like cells, exhibiting electrical conductivity similar to that of native heart tissue, which was further enhanced by reduced graphene oxide [70]. Similarly, dextran/gelatin hydrogels loaded with TGF-β3- nanoparticles have shown promise for intervertebral disc degeneration treatment by facilitating MSC differentiation into nucleus pulposus-like cells [71]. Furthermore, dextran-based hydrogels synthesized through thiol–Michael addition reactions, such as Dex-l-DTT, offer adjustable mechanical characteristics and the best 3D microenvironment for encapsulating stem cells while preserving their viability and capacity for differentiation [72]. These diverse applications highlight how dextran can improve cell treatment results, support controlled release mechanisms, and mimic the natural cellular environment, making it an important component in the development of cell-based regenerative therapies.

4.7. Gelatin

Gelatin-based hydrogels have become a viable biomaterial in regenerative medicine because they are biocompatible, tunable, and can form MSC-supporting microenvironments. In cardiac repair, gelatin–hydroxyphenyl propionic acid hydrogels have been developed as injectable, in situ cross-linkable carriers for MSCs, significantly improving the survival and retention of encapsulated MSCs [73]. These hydrogels have been shown to reduce fibrosis, enhance myocardial wall thickness, and improve cardiac functions, as evidenced by the improvement in ejection fraction and end-systolic volume. The versatility of gelatin microparticles also allowed them to be integrated into thermally and chemically gelling hydrogels, providing a three-dimensional environment that preserves MSC viability, promotes osteogenic differentiation, and facilitates hydrogel mineralization [74]. Together, these findings highlight the potential of gelatin-based hydrogels in advancing tissue regeneration and cell-based therapies.

4.8. Hyaluronic Acid

Hyaluronic acid (HA), a natural glycosaminoglycan, has emerged as a pivotal biomaterial in regenerative medicine and tissue engineering, particularly for MSC applications. Its capacity to mimic natural extracellular matrix enables the creation of sD microenvironments that support MSC survival and development. Compared with conventional 2D cultures, studies have revealed that MSCs grown in HA-based hydrogels exhibit improved proliferation and stemness. For example, alginate–hyaluronic acid (AL-HA) hydrogels upregulate the expression of genes essential for tissue growth and stemness, such as OCT-4, NANOG, and SOX2, while maintaining high survival rates and promoting the formation of cellular spheroids [75]. Additionally, HA hydrogels modified with tyramine and dopamine have demonstrated improved MSC survival under oxidative stress, providing a viable platform for cell encapsulation in harsh microenvironments [76]. The cartilage-mimicking capabilities of HA have also been used for chondrogenesis; MSCs encapsulated in HA hydrogels have outperformed inert materials, like polyethylene glycol, in terms of the significant elevation of cartilage-specific markers, including type-II collagen and aggrecan [77]. These findings underscore HA’s potential as a flexible biomaterial for promoting tailored differentiation, preserving stemness, and advancing MSC administration in various therapeutic applications.

4.9. Polyethylene Glycol

Polyethylene glycol (PEG) is a widely used biomaterial in regenerative medicine, often used alone or in combination with other biomaterials to encapsulate MSCs for therapeutic applications. For example, MSCs encapsulated in PEG-collagen hydrogels have been used to deliver their secretome in treating alkali-burn-induced corneal damage. This approach reduces fibrotic repair and restores corneal transparency, suggesting that PEG-based encapsulation may enhance MSC-based therapies for ocular inflammation [78]. In another study, the role of PEG in cell encapsulation was further explored using microfluidic devices to fabricate PEG norbornene (PEGNB) microgels. These microgels, which encapsulated equine MSCs, maintained cell viability for more than 14 days and promoted the secretion of growth factors, such as FGF-2 and TGF-β. Thus, research highlights PEG’s potential to create uniform, supportive environments for MSCs, offering a versatile platform for high-throughput, precise cell therapies in tissue engineering and regenerative medicine [79].

4.10. Poly (Lactic-Co-Glycolic Acid)

Poly (lactic-co-glycolic acid) (PLGA) is a versatile biomaterial that has garnered significant attention in tissue engineering and regenerative medicine, primarily due to its ability to encapsulate growth factors and protect therapeutic cells. One study combined PLGA microspheres containing bone morphogenetic protein-2 (BMP-2) and vascular endothelial growth factor (VEGF) with MSCs to reconstruct critical-sized mandibular defects in pigs. The results demonstrated enhanced defect healing, with the PLGA microspheres facilitating the controlled release of growth factors, promoting improved tissue mineralization and bone remodeling [80]. Similarly, PLGA nanoparticles were used to modify MSCs by encapsulating silibinin, a cytoprotective compound. This modification enhanced MSCs’ resistance to oxidative stress, improving their survival and therapeutic efficacy in treating cutaneous wounds [81]. Together, these studies underscore the potential of PLGA as an effective tool in controlled delivery systems for growth factors and cytoprotective agents, significantly enhancing the regenerative capacity of MSCs in challenging clinical applications, like bone repair and wound healing.

5. Microencapsulation Techniques

5.1. Extrusion

Extrusion is one of the most widely used techniques for cell microencapsulation in regenerative medicine. It includes methods such as electrospray droplet extrusion, air jet extrusion, syringe droplet extrusion, centrifugal extrusion, electrostatic extrusion, and vibrational extrusion. Notably, electrospray droplet extrusion has been extensively applied in stem cell microencapsulation research [36]. This technique, which uses an organic solvent, enables the production of hydrogel beads of approximately 50 µm in diameter without compromising cell viability. The procedure involves gravity dripping, where a hydrogel precursor and cell suspension are extruded through a needle into a hardening solution [63]. The diameter of microspheres is determined by several parameters, including the density of the solution, the diameter of the extrusion needle/nozzle, and the surface tension of the droplets [63]. A homogeneous cell solution and rinsing the nozzle with sodium citrate help to minimize clogging. Additionally, using appropriate settings and a blunt-tip nozzle can help to prevent cell injury [82].

5.2. Emulsion

Emulsion-based cell encapsulation typically involves distributing hydrogel precursor in a non-miscible solution, notably a water-in-oil emulsion. At equilibrium, internal gelation occurs, followed by centrifugation to collect the emulsified hydrogels [83]. This method offers various benefits, including lower production costs and scalability. However, the vast size distribution and cell disruptions at the oil–water interface have prompted some concerns. In addition, prolonged exposure to oil and surfactants results in a cytotoxic environment that disrupts cells and adversely affects cell viability [12].

5.3. Microfluidics

Microfluidics is a technique for manipulating fluids in microenvironments, enabling the development of microgels. Droplet-based microfluidics represents a potent and versatile tool for reconstructing microenvironments, offering exceptionally high throughput and tight control over cells, biomolecules, and extracellular matrix [84]. There are two major categories of droplet-based microfluidics techniques: active and passive. Passive techniques, such as flow-focusing, co-flow, and T-junction design, are prevalent in cell microencapsulation [85]. In droplet-based microfluidics, droplets are typically produced using flow-focusing and co-flow microfluidic devices, where the shear stress exerted by a continuous phase on a dispersed phase generates the droplets. Typically, both phases are composed of immiscible liquids. In T-junction devices, droplets are formed when two channels meet at the 90° angle and exit by a perpendicular stem. The dimensions of the microchannel and flow rates of the two phases affect the size and shape of the droplets in microfluidics-based synthesis. Owing to the simplicity of droplets and homogeneous size distribution of microbeads, T-junctions are frequently used in microfluidics for cell microencapsulation [86].

5.4. Micromolding

Micro-molding is a recently introduced bio-fabrication method for hydrogels with regulated size and shape. Photolithography technology creates these micro-molds with predetermined patterns into which intended polymers are poured and then gelled to create three-dimensional hydrogel constructs [87]. Micro-molding offers several benefits for cell microencapsulation compared with other techniques, including eliminating shear stress from the cell suspension passing through a nozzle and reducing the impact of oils and surfactants that might affect cell viability or behavior [36]. Polydimethylsiloxane was used to create micro-mold chips using photolithography [87] to mitigate osteoarthritis severity. Then, a mixture of adipose-derived stem cells and alginate was poured and gelled inside the micro-mold to form microcapsules of 150 µm size. These micro-encapsulated cells were used for intra-articular injection in a rabbit model. The same research group reported the use of the micro-molding technique to fabricate cross-linked alginate microcapsules with 170 µm size to encapsulate MSCs for better hydrogel stability in the synovial fluid upon its use in intra-articular injection [87].

6. Pre-Clinical Studies Using Microencapsulated MSCs

Pre-clinical studies have demonstrated that microencapsulation of MSCs enhances their therapeutic potential in various disease models. This approach improves cell viability, functionality, and immune evasion, making it a promising strategy for regenerative medicine applications across musculoskeletal, cardiovascular, neurological, and other conditions in preclinical settings (Table 2).

6.1. Musculoskeletal Diseases

Microencapsulation has been shown to enhance the viability and functionality of MSCs for musculoskeletal tissue regeneration. MSC encapsulation provides a biocompatible 3D microenvironment that facilitates the differentiation capacity of the immobilized stem cells and modulates the inflammatory reaction upon implementation [88,89,90,91,92,93]. For example, when a composite of alginate-microencapsulated rabbit BM-MSCs with β-tricalcium phosphate/calcium phosphate cement was implanted into rabbits with critical size defects, the composite group showed more new bone formation in the bone defects when compared with the control group [94]. Similarly, synchronized 3D vehicle delivery of encapsulated BM-MSCs and the bone morphogenetic protein-2 (BMP-2) showed better efficacy for large bone defects, as evidenced by enhanced osteogenic differentiation and accelerated maturity of newly formed bone tissue [90,95,96].
Additionally, the immobilization of periodontal ligament stem cells (PDLSCs) and gingival MSCs (GMSCs) in alginate microcapsules has been demonstrated as a therapeutically potent strategy in bone tissue engineering [89,97]. Alginate hydrogel microbeads allow the influx of nutrients and oxygen to the encapsulated cells, as well as the efflux of metabolites. This results in prolonged stem cell viability, lasting up to 28 days after encapsulation. The osteogenic differentiation capacity of GMSCs was enhanced by encapsulation, although to a lesser extent in GMSCs. Additionally, ectopic mineralization significantly increases due to both in vitro and in vivo encapsulation, demonstrating their ability to repair calvaria defects [55]. The intra-articular injection of alginate-microencapsulated ASCs was also investigated to manage anterior cruciate ligament transection in a rabbit model. Microencapsulated cells showed a significant chondroprotective effect, which could be a promising strategy for treating osteoarthritis [98].

6.2. Cardiovascular Diseases

The use of MSCs as an alternative therapy for cardiovascular diseases is challenging, primarily due to the low retention rate of the introduced stem cells. Studies have reported that less than 10% of cells remain in the heart after one hour of intracoronary infusion [99]. The short retention period may result from various factors, including cell removal through lymphatic or vascular channels or clearance by the immune system.
Encapsulating MSCs before their in vivo application may prolong their initial retention period because the size and physical structure of the capsules protect them from being washed out through lymphatic or venous channels and provide a barrier against the immune system [46]. Bioluminescence imaging has shown that encapsulated MSCs exhibit prolonged retention throughout the myocardium. As a result, encapsulated MSCs reduced scarring after myocardial infarction (MI), significantly enhancing the microvasculature around the area of infarction [99].
Much work has been conducted to elucidate the efficacy and potential of encapsulated MSCs for cardiovascular diseases. Encapsulated MSCs are potent cell therapy approaches for the regeneration of myocardial infarction (MI), as they lead to improved cardiovascular functions and the formation of new blood vessels [99,100]. MSCs encapsulated by arginine-glycine-aspartate (RGD)-coupled alginate are potent in regenerating damaged heart tissue caused by myocardial infarction [101]. The microspheres efficiently enhance the behavior of MSCs and facilitate their transport to the site of damage. They likely serve as a scaffold to preserve the shape of the left ventricle and avoid its adverse remodeling after a myocardial infarction [102]. Furthermore, when MSCs were co-transplanted with Schwan cells, they enhanced angiogenesis inside the ischemic myocardium, resulting in improved cardiac function in rats [103]. Encapsulation in alginate/graphene oxide micro-gel has also been shown to promote MSC antioxidant activity, offering a protective environment against oxidative stress associated with acute myocardial infarction [19]. In comparative studies, encapsulating human MSCs has demonstrated notable superiority over non-encapsulated MSCs in promoting vascular regeneration in a hindlimb ischemia mouse model [104].

6.3. Diabetes

The selective destruction of insulin-producing β cells within pancreatic islets is a hallmark of type 1 diabetes, which requires patients to take daily exogenous insulin to maintain normal blood glucose levels [105]. The transplantation of pancreatic islets encapsulated inside alginate microcapsules to avoid islet immune rejection has been considered a treatment option for patients with type 1 diabetes. However, immediate inflammatory reactions around the capsules still occur, leading to the formation of pericapsular fibrotic overgrowth (PFO) and engraftment failure of the islets. PFO occurs because of the host’s inflammatory reaction to antigens released by encapsulated allogeneic or xenogeneic tissue. The formation of a physical barrier, mainly consisting of macrophages and fibroblasts, hinders the transportation of oxygen and other nutrients. Consequently, this results in a state of malnourishment and hypoxia, ultimately leading to the death of the islet. PFO persists despite the use of immunosuppressive therapy. To solve these issues, it is necessary to investigate the co-encapsulation of MSCs with islet cells to utilize their immunomodulating and revascularization potential [23].
The co-encapsulation of MSCs with pancreatic islets has effectively promoted insulin production and maintained normal blood glucose levels in diabetic mouse models [23]. The formation of PFO was dramatically reduced with enhancement in the islet viability, suggesting the immunosuppressive potential of MSCs and their role in improving the functionality of the co-encapsulated islet cells. For further improvements, Razavi and colleagues have developed a non-invasive method in which ultrasound activation is applied for the microcapsules to stimulate both islets and MSCs. This strategy has proven effective in inhibiting islet cell death and maintaining functionality. Furthermore, it has successfully improved the engraftment of islets by promoting their revascularization and mitigating inflammation [106].

6.4. Neurological Disorders

MSC therapy has been used as an effective alternative therapy for neurological disorders, mainly based on its immunomodulatory properties via attenuating neuroinflammation and the production of anti-inflammatory cytokines [107]. MSCs have also proven potent in treating central nervous system (CNS) injuries and neurodegenerative disorders, as they can differentiate into neuronal phenotypes [108]. Microencapsulation has been suggested to improve the potency of MSC therapy. For example, encapsulated MSCs have exhibited higher efficacy in mitigating CNS injuries and their associated inflammation [109]. MSCs encapsulated by alginate microencapsulation have effectively attenuated neuroinflammation resulting from post-spinal-cord [110] injury and brain damage [109]. Encapsulated hMSCs not only retain their viability and their secretory activity, but also modulate the inflammatory response. As for the mechanism, encapsulated stem cells secrete anti-inflammatory cytokines, such as IL-4, IL-13, IL-2, IL-1b, and IL-9, upon exposure to pro-inflammatory mediators, such as TNF-α and interferon-gamma (IFN-α). In addition, they regulate the activity of inflammatory macrophages both in vitro and in vivo. This effect was seen even when there was no direct contact between human MSCs and macrophages, promoting the alternative M2 macrophage phenotype [109].
Glucagon-like peptide 1 (GLP-1) has a neuroprotective effect against cytotoxicity and neurodegeneration. Thus, the subcutaneous injection of GLP-1 analogs is an approved therapy for amyotrophic lateral sclerosis (ALS). Alginate-encapsulated MSCs producing GLP-1 have demonstrated effectiveness as a cell therapy for ALS [25]. Encapsulated MSCs have been produced by transfection with a plasmid encoding a GLP-1 fusion gene before injection to improve their neuroprotective properties. Encapsulated GLP-1 MSCs have been injected into an ALS mouse model intracerebroventricularly before disease onset. Animal survival was prolonged by 13 days, the disease onset was delayed by 15 days, and the motor functions were improved; this was associated with reduced serum proinflammatory cytokine levels [25].

6.5. Cancer

While MSCs have emerged as a promising cell-based therapy for various cancers, several drawbacks have been identified that may diminish their antitumorigenic potential. For instance, after in vivo infusion, MSCs have been shown to migrate toward tumors and interact directly with tumor stromal elements in the case of colonic adenocarcinoma, multiple myeloma [111], and melanoma [112]. MSC encapsulation has been proposed to provide a 3D microenvironment in which cell contact with cancer cells is inhibited. This approach also has the potential to enhance their therapeutic effects and increase their paracrine activity [22,113].
Alginate-encapsulated MSCs have successfully reduced tumor volume in a syngeneic rat glioma model [113]. The tumor-suppressive effect of encapsulated, unmodified MSCs is about twofold higher than that of MSCs transfected to produce endostatin, an antiangiogenic peptide. Alginate-encapsulated Wharton’s jelly MSCs (WJ-MSCs) are efficient as a cell-based therapy for breast cancer and in inhibiting the formation of the self-renewing cell population, the cancer stem cells [22]. This inhibitory activity was likely attributed to the downregulation of several cancer-associated genes and the induction of cell apoptosis factors, such as caspases, and increased ROS production in cancer cells. In addition, encapsulated stem cells were able to trigger the expression of Wnt antagonists, such as Secreted Frizzled-related protein 4 (sFRP4), Dickkopf-1 (DKK1), and glycogen synthase kinase 3 beta (GSK-3β), downregulating the β-catenin pathway, which is involved in tumor promotion [22].

6.6. Liver Diseases

Hepatocytes comprise about 80% of the liver mass and are crucial for liver function. Liver failure is usually associated with hepatocyte malfunctioning [21,114]. Hepatocyte transplantation is an alternative therapy to orthotopic liver transplantation for liver fibrosis and acute liver failure [17,114]. However, some drawbacks have been reported; for example, the immune system initiates a foreign-body-fighting mechanism against the transplanted cells, which hampers its functionality. This was attributed to a possible direct contact between the introduced hepatocytes and recipient immune cells. Immunosuppressive drugs used to attenuate the immune activity can be toxic [59]. Hence, exploring alternative therapeutic strategies, such as microencapsulated MSCs or the co-encapsulation of MSCs with hepatocytes in the recovery of liver failure, has emerged and been investigated [17,20,21,115].
Table 2. MSCs and microencapsulation in in vivo models.
Table 2. MSCs and microencapsulation in in vivo models.
Ref.Cell TypeEncapsulation MaterialEncapsulation TechniqueApplicationOutcomes
[11]BM-MSCsAlginateSyringe droplet extrusionOsteoarthritisHigh G alginate prolonged the presence of metabolically active allogenic MSC in immune-competent rats.
[88]BM-MSCsCollagenSyringe droplet extrusionCartilage regenerationPromotion of chondrogenic differentiation of MSCs when high cell density and high collagen concentration were applied.
[90]BM-MSCsAlginate modified with glycine-arginine-glycine-aspartic acid-glycineMicrofluidicBone regenerationEnhancement of osteogenic differentiation and acceleration of mineralization
[91]BM-MSCsFibrin/AlginateSyringe droplet extrusionVolumetric muscle loss (VML) injuriesGreater muscle regeneration of rat VML in a shorter period.
[92]BM-MSCsCollagen-chitosanEmulsionBone regenerationEnhancement of ectopic bone formation
[93]SHEDRGD-modified alginateMicrofluidicBone regenerationEnhanced cell viability and increased ectopic bone formation
[116]BM-MSCsAlginateElectrostatic extrusionBone regenerationEnhanced bone formation and bone marrow growth
[95]BM-MSCs transduced with BMP2 and/or VEGFAlginateElectrostatic extrusionBone regenerationSignificant improvement in release of BMP2 and VEGF from genetically modified MSCs with enhancement in osteogenic differentiation.
[96]BM-MSCsAlginateElectrostatic extrusionBone regenerationPromotion of the osteogenic differentiation of BM-MSCs.
[97]PDLSCs, GMSCs, and BM-MSCsRGD-modified Alginate loaded with TGF-β3 ligandSyringe droplet extrusionTendon regenerationEffective differentiation into tendon tissue.
[98]ASCsAlginateVibrational extrusionOsteoarthritisEnhancement of the viability of ASCs in the knee joint and significant reduction in the Osteoarthritis progression and extent.
[117]BM-MSCsAlginateSyringe droplet extrusionBone regenerationEncapsulating MSCs with PEDF improves differentiation and release of cells compared to encapsulation of MSCs alone
[118]PDLSCs and GMSCsRGD-modified alginateMicrofluidicBone regenerationHigher amounts of ectopic bone regeneration.
[119]BM-MSCsAlginateElectrostatic extrusionOrbital bone repair-Effective induction of osteogenic differentiation.
-Greatest bone repair of the orbital wall defect.
[120]BM-MSCsAlginateElectrostatic extrusionOsteoarthritis-Chondroprotective effect through paracrine signaling.
-Augmentation of the compensatory increases in osteophyte formation.
[121]PDLSCs and GMSCsRGD-modified AlginateMicrofluidicCartilage regenerationChondrogenic differentiation of encapsulated PDLSCs and GMSCs.
[122]BM-MSCs, PDLSCs, and GMSCsAlginateSyringe droplet extrusionBone regenerationEctopic bone formation around and inside the implemented microcapsules
[13]BM-MSCsAlginate–poly-l-lysine–alginateEmulsionEnhancement of vascularizationReduced immune reaction against grafted MSCs cells by microencapsulation
[19]UC-MSCsGO/AlginateElectrostatic extrusionMyocardial infarction-Enhancement of the therapeutic activity of the MSCs.
-Reduction of post-injection oxidative stress.
[37]MSCs modified to express erythropoietinAlginateElectrostatic extrusionErythropoietin deliveryCapsules with lower cell loading showed higher erythropoietin secretion.
[123]BM-MSCsAgaroseSyringe droplet extrusionVascular regeneration-Improvement of viability and metabolic activity of the MSCs as well as cell–cytoskeletal patterning.
-Significant increase in the number of engrafted cells.
[99]MSCsAlginateElectrostatic extrusionMyocardial infarctionHigher cell retention and increase in vasculature around infarct site
[101]MSCsRGD- modified AlginateElectrostatic extrusionMyocardial infarction-Effective delivery of the MSCs to the site of infraction.
-Maintaining the LV shape and preventing its negative remodeling.
[103]BM-MSCsAlginate–poly-L-lysine–alginateElectrostatic extrusionMyocardial infarctionAngiogenesis augmentation and heart function improvement in acute myocardial infarction.
[104]BM-MSCsAlginateElectrostatic extrusionHindlimb ischemiaSignificant enhancement of vascular recovery in mouse model of ischemic hindlimb.
[124]IX–engineered MSCsAlginateElectrostatic extrusionHemophilia treatment.-Factor IX secretion was increased by encapsulated MSCs
-osteogenic differentiation was also observed
[125]MSCsAlginate-poly-L-lysine-alginateElectrostatic ExtrusionErythropoietin deliveryLong-lasting (up to 210 days) secretion of erythropoietin after loading the microcapsules in vivo.
[1]BM-MSCsAlginateAir jet extrusionIslets transplantation-Improvement of the viability of islets.
-MSC–alginate beads exhibited an ability to interactively modulate their microenvironment by IDO activity and secreting several immunomodulatory and trophic factors over a long-term.
[16]UC-MSCsAlginateSyringe droplet extrusionType 1 diabetesReversal of hyperglycemic status by the synergistic effect of MSCs with pancreatic islet-derived progenitor cells.
[23]BM-MSCsAlginate-chitosanElectrostatic extrusionType 1 diabetesReduction of blood glucose to levels close to the normal blood glucose level of healthy mice.
[106]ASCsAlginateAir-jet extrusionCo-encapsulation of MSCs with pancreatic Islets transplantationSignificant improvement in the functionality and viability of the transplanted islets.
[25]GLP-1 releasing MSCsAlginateExtrusionAmyotrophic lateral sclerosis (ALS)-Delayed symptom onset and reduction of inflammatory markers
-Improved motor performance and prolonged survival.
[110]MSCsAlginate poly-L-lysineElectrostatic extrusionPost-spinal cord injuryMicroencapsulation of MSC is involved in the post-CNS traumatic tissue protective therapy through the conversion of macrophages to the M2 subset.
[126]BDNF-over-expressing BM-MSCsAlginateAir-jet extrusionDeafnessImproved cochlear implant outcome; increased spiral ganglion neuron survival, bipolar morphology, and neurite outgrowth.
[113]BM-MSCsAlginateAir-jet extrusionGlioma tumorSuppression of the tumor growth.
[22]WJ-MSCsAlginateSyringe droplet extrusionBreast cancerDown-regulation of pro-proliferation markers, drug transporters, epithelial-mesenchymal transition-associated markers, and angiogenesis-related genes.
[127]BM-MSCsAlginate-poly-L-lysine-alginateAir-jet extrusionGlioblastomaA 3-fold decrease in cytokine expression compared to entrapped cell lines.
[17]BM-MSCsAlginate-poly-L-lysine-alginateElectrostatic extrusionAcute liver failureSignificant enhancement of hepatocyte-specific functions, including albumin secretion and urea synthesis.
[18]BM-MSCsAlginateAir jet extrusionPericapsular fibrotic overgrowth around alginate microcapsule PFODose-dependent reduction in PFO and improved graft survival with significantly higher cell viability.
[20]BM-MSCsAlginateAir jet extrusionLiver fibrosisMicroencapsulated BM-MSCs showed anti-fibrotic effect
[21]BM-MSCsAlginate/collagenElectrostatic extrusionLiver repair and regenerationCo-encapsulation with AML12 hepatocytes allowed MSCs to differentiate into hepatocytes and be involved in hepatic regeneration
[35]ASCsAlginateVibrational extrusionCell viability inside the microcapsuleImproved cell viability and retention in vivo.
[128]BM-MSCsAlginateVibrational extrusionCell viability inside the microcapsuleEncapsulated cells remained viable under the kidney capsule with the release of factor bFGF.
[129]MSCsAlginateExtrusionCell viability inside the microcapsuleEncapsulated MSCs were active for several weeks and acted as a release system
BM-MSCs (Bone marrow-derived mesenchymal stem cells), SHED (Stem cells from human-exfoliated deciduous teeth), PDLSCs (Periodontal ligament stem cells), GMSCs (Gingiva-derived mesenchymal stem cells), ASC (Adipose-derived stem cells), UC-MSCs (Umbilical cord-derived mesenchymal stem cells), WJ-MSCs (Wharton’s jelly-derived mesenchymal stem cells), BMP2 (Bone morphogenetic protein 2), VEGF (Vascular endothelial growth factor), TGFβ (Transforming growth factor β), BDNF (Brain-derived neurotrophic factor), EPO (Extrapontine), PFO (Pericapsular fibrotic overgrowth), RGD (Arginine–glycine–aspartic acid).
The microencapsulation of MSCs preserved functionality and attenuated immune rejection after MSC transplantation, exhibiting enhancements in liver rescuing [17,20]. The co-encapsulation of hepatocytes and BM-MSCs in alginate-poly-L-lysine-alginate microencapsulation improved hepatocyte-specific functions, including albumin secretion and urea synthesis, both in vitro and in vivo [17]. Thus, the survival rate and liver function were enhanced after the transplantation of encapsulated hepatocytes and MSCs in a rat model of acute liver failure. Furthermore, MSC and AML12 hepatocyte co-encapsulation in volvox spheres promotes hepatocyte regeneration in rat model necrotic liver failure, as assessed by albumin and cytokeratin 18 expression [21]. A volvox sphere microencapsulation comprises a large outer sphere containing smaller spheres that encapsulate the culturing cells, which finally provides a double-layer 3D microencapsulation. The microencapsulation of MSCs by alginate–polyethylene glycol (Alg-PEG) hybrid hydrogel facilitated the protection of MSCs against in vivo immune rejection upon transplantation into the fibrotic liver in mice. Microencapsulated human mesenchymal stem cells decrease liver fibrosis in mice [20]. This protective effect has been attributed to the selective permeability of the hybrid hydrogel, which is permissive to soluble factors, such as oxygen and glucose, and non-permissive to immune cells and antibodies. This property keeps the MSCs from direct contact with the immune cells and mitigates immune rejection after in vivo infusion [20]. All these data support the idea that MSC microencapsulation is a promising cell-based therapy for liver diseases.

7. Current Challenges and Future Perspectives

Despite significant advances in MSC microencapsulation, several challenges remain. One notable issue is that the encapsulation process may alter MSC function, including cell survival in the capsule and reducing the secretion of growth factors [38,130]. Additionally, ongoing research is focused on identifying the most effective strategies for utilizing microencapsulated MSCs in regenerative therapies. Numerous studies have investigated factors such as the MSC source, encapsulation materials, delivery mechanisms, and specific pathologies. However, significant gaps and biases persist, which need to be addressed. Furthermore, a method that shows promise for one disease may not yield the same results for others. Further research is needed to optimize encapsulation techniques that preserve and potentially enhance MSC functions for broader therapeutic applications.
One of the unresolved issues is material long-term biocompatibility. The functionality of the capsules is closely related to their interaction with the immune system. The immunogenicity of the capsules triggers a series of cellular reactions, including inflammation, pericapsular fibrosis, and damage to the grafted region. This reaction is harmful to both the subjects and the implanted cells. Multiple strategies have been tested to address this issue. For instance, administering anti-inflammatory molecules such as pentoxifylline [131], dexamethasone [132], and curcumin [133] has shown promising outcomes. Furthermore, the encapsulating polymers themselves might pose a risk for immunogenicity. Polyoxazolines [134] and zwitterionic polymers [135] have low immunogenicity and are more suitable in MSC microencapsulation. These neutrally charged synthetic polymers offer a variety of beneficial qualities over other materials, including high hydrophilicity, minimal non-specific interaction, and minimal immunogenicity [136,137].
Maintaining control over the intra-capsular microenvironment is a significant concern, as cells are not isolated entities, but rather part of a complex and dynamic mixture that includes the cells themselves, extracellular matrix, growth factors, and surrounding cells. Cultivating cells outside their native environments requires a thorough understanding of cell biology. The capsules can be modified with different motifs to replicate their natural habitat. One effective approach involves short peptide sequences comprising functional domains derived from ECM proteins [138]. For example, arginine–glycine–aspartic acid, a component of many extracellular matrix proteins like collagen and fibronectin, has shown promising results [45,139]. Other examples include laminin motifs, such as Tyr-Ile-Gly-Ser-Arg and Ile-Lys-Val-Ala-Val [24]. Moreover, emerging trends in capsule design, such as the development of “smart” biomaterials with real-time monitoring capabilities and stimuli-responsive hydrogels that release therapeutic agents in response to environmental changes (e.g., pH or temperature), promise to address many of the challenges associated with MSC encapsulation.

8. Conclusions

This review summarizes studies using microencapsulation techniques to address challenges associated with MSC therapy (Figure 1). A variety of materials and key techniques used for microencapsulation have been explored. This review also highlights the diverse applications of MSC microencapsulation, with a particular emphasis on regenerative medicine and immunomodulation. There is a growing focus on employing microencapsulation technology to effectively replicate the in vivo microenvironment. An ideal microcapsule should provide a 3D scaffold, shield the MSCs from the host’s immune response, and maintain key MSC characteristics, such as phenotypic differentiation and adhesion. Additionally, the microcapsule must exhibit selective permeability, allowing essential nutrients and gasses to pass through while preserving cell viability and preventing fibrosis formation. Achieving this balance is crucial for enhancing the therapeutic potential of MSCs in clinical applications.

Author Contributions

S.E.M.A., G.M., H.W. and A.L. wrote the article. H.W. and A.L. contributed equally to the study design and critical review of the manuscript. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported by NIDDK grants 1R01DK105183, R01DK123094, R01DK118529, and R01DK125464 and the Department of Veterans Affairs grants 5I01CX002516 and I01BX004536.

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

Not applicable.

Acknowledgments

The figure was created using the BioRender.com.

Conflicts of Interest

The authors declare no other conflict of interest.

References

  1. Vaithilingam, V.; Evans, M.D.M.; Lewy, D.M.; Bean, P.A.; Bal, S.; Tuch, B.E. Co-encapsulation and co-transplantation of mesenchymal stem cells reduces pericapsular fibrosis and improves encapsulated islet survival and function when allografted. Sci. Rep. 2017, 7, 10059. [Google Scholar]
  2. Liu, S.; Zhou, J.; Zhang, X.; Liu, Y.; Chen, J.; Hu, B.; Song, J.; Zhang, Y. Strategies to Optimize Adult Stem Cell Therapy for Tissue Regeneration. Int. J. Mol. Sci. 2016, 17, 982. [Google Scholar] [CrossRef] [PubMed]
  3. Kim, H.J.; Park, J.-S. Usage of Human Mesenchymal Stem Cells in Cell-based Therapy: Advantages and Disadvantages. Dev. Reprod. 2017, 21, 1–10. [Google Scholar] [PubMed]
  4. Chen, Q.; Shou, P.; Zheng, C.; Jiang, M.; Cao, G.; Yang, Q.; Cao, J.; Xie, N.; Velletri, T.; Zhang, X.; et al. Fate decision of mesenchymal stem cells: Adipocytes or osteoblasts? Cell Death Differ. 2016, 23, 1128–1139. [Google Scholar] [PubMed]
  5. Caplan, A.I. Mesenchymal stem cells. J. Orthop. Res. 1991, 9, 641–650. [Google Scholar] [PubMed]
  6. Caplan, A.I.; Dennis, J.E. Mesenchymal stem cells as trophic mediators. J. Cell. Biochem. 2006, 98, 1076–1084. [Google Scholar] [CrossRef]
  7. Li, C.; Zhao, H.; Wang, B. Challenges for Mesenchymal Stem Cell-Based Therapy for COVID-19. Drug Des. Dev. Ther. 2020, 14, 3995–4001. [Google Scholar]
  8. de Vos, P.; Bučko, M.; Gemeiner, P.; Navrátil, M.; Svitel, J.; Faas, M.; Strand, B.L.; Skjak-Braek, G.; Morch, Y.A.; Vikartovská, A.; et al. Multiscale requirements for bioencapsulation in medicine and biotechnology. Biomaterials 2009, 30, 2559–2570. [Google Scholar] [PubMed]
  9. Orive, G.; De Castro, M.; Ponce, S.; Hernández, R.M.; Gascón, A.R.; Bosch, M.; Alberch, J.; Pedraz, J.L. Long-term expression of erythropoietin from myoblasts immobilized in biocompatible and neovascularized microcapsules. Mol. Ther. 2005, 12, 283–289. [Google Scholar]
  10. Griffith, L.G.; Naughton, G. Tissue engineering—Current challenges and expanding opportunities. Science 2002, 295, 1009–1014. [Google Scholar] [CrossRef] [PubMed]
  11. Khatab, S.; Leijs, M.J.; van Buul, G.; Haeck, J.; Kops, N.; Nieboer, M.; Bos, P.K.; Verhaar, J.A.N.; Bernsen, M.; van Osch, G.J.V.M. MSC encapsulation in alginate microcapsules prolongs survival after intra-articular injection, a longitudinal in vivo cell and bead integrity tracking study. Cell Biol. Toxicol. 2020, 36, 553–570. [Google Scholar] [CrossRef]
  12. Daly, A.C.; Riley, L.; Segura, T.; Burdick, J.A. Hydrogel microparticles for biomedical applications. Nat. Rev. Mater. 2020, 5, 20–43. [Google Scholar] [CrossRef] [PubMed]
  13. Wang, G.; Fu, Y.; Shea, S.M.; Hegde, S.S.; Kraitchman, D.L. Quantitative CT and 19 F-MRI tracking of perfluorinated encapsulated mesenchymal stem cells to assess graft immunorejection. Magn. Reson. Mater. Phys. Biol. Med. 2019, 32, 147–156. [Google Scholar] [CrossRef] [PubMed]
  14. Wang, N.; Adams, G.; Buttery, L.; Falcone, F.H.; Stolnik, S. Alginate encapsulation technology supports embryonic stem cells differentiation into insulin-producing cells. J. Biotechnol. 2009, 144, 304–312. [Google Scholar] [CrossRef]
  15. Lee, S.-Y.; Ma, J.; Khoo, T.S.; Abdullah, N.; Kahar, N.N.F.N.M.N.; Hamid, Z.A.A.; Mustapha, M. Polysaccharide-Based Hydrogels for Microencapsulation of Stem Cells in Regenerative Medicine. Front. Bioeng. Biotechnol. 2021, 9, 735090. [Google Scholar]
  16. Montanucci, P.; Pescara, T.; Greco, A.; Leonardi, G.; Marini, L.; Basta, G.; Calafiore, R. Co-microencapsulation of human umbilical cord-derived mesenchymal stem and pancreatic islet-derived insulin producing cells in experimental type 1 diabetes. Diabetes/Metab. Res. Rev. 2021, 37, e3372. [Google Scholar] [CrossRef] [PubMed]
  17. Shi, X.-L.; Zhang, Y.; Gu, J.-Y.; Ding, Y.-T. Coencapsulation of hepatocytes with bone marrow mesenchymal stem cells improves hepatocyte-specific functions. Transplantation 2009, 88, 1178–1185. [Google Scholar] [CrossRef]
  18. Vaithilingam, V.; Evans, M.D.M.; Rowe, A.; Bean, P.A.; Tuch, B.E. Coencapsulation of Target Effector Cells with Mesenchymal Stem Cells Reduces Pericapsular Fibrosis and Improves Graft Survival in a Xenotransplanted Animal Model. Cell Transplant. 2016, 25, 1299–1317. [Google Scholar] [CrossRef]
  19. Choe, G.; Kim, S.W.; Park, J.; Park, J.; Kim, S.; Kim, Y.S.; Ahn, Y.; Jung, D.W.; Williams, D.R.; Lee, J.Y. Anti-oxidant activity reinforced reduced graphene oxide/alginate microgels: Mesenchymal stem cell encapsulation and regeneration of infarcted hearts. Biomaterials 2019, 225, 119513. [Google Scholar]
  20. Meier, R.P.; Mahou, R.; Morel, P.; Meyer, J.; Montanari, E.; Muller, Y.D.; Christofilopoulos, P.; Wandrey, C.; Gonelle-Gispert, C.; Bühler, L.H. Microencapsulated human mesenchymal stem cells decrease liver fibrosis in mice. J. Hepatol. 2015, 62, 634–641. [Google Scholar] [CrossRef]
  21. Chang, S.H.; Huang, H.H.; Kang, P.L.; Wu, Y.C.; Chang, M.-H.; Kuo, S.M. In vitro and in vivo study of the application of volvox spheres to co-culture vehicles in liver tissue engineering. Acta Biomater. 2017, 63, 261–273. [Google Scholar] [CrossRef] [PubMed]
  22. Mandal, S.; Arfuso, F.; Sethi, G.; Dharmarajan, A.; Warrier, S. Encapsulated human mesenchymal stem cells (eMSCs) as a novel anti-cancer agent targeting breast cancer stem cells: Development of 3D primed therapeutic MSCs. Int. J. Biochem. Cell Biol. 2019, 110, 59–69. [Google Scholar] [CrossRef] [PubMed]
  23. Long, R.; Liu, Y.; Wang, S.; Ye, L.; He, P. Co-microencapsulation of BMSCs and mouse pancreatic beta cells for improving the efficacy of type I diabetes therapy. Int. J. Artif. Organs 2017, 40, 169–175. [Google Scholar] [CrossRef] [PubMed]
  24. Llacua, A.; de Haan, B.J.; Smink, S.A.; de Vos, P. Extracellular matrix components supporting human islet function in alginate-based immunoprotective microcapsules for treatment of diabetes. J. Biomed. Mater. Res A 2016, 104, 1788–1796. [Google Scholar] [CrossRef]
  25. Knippenberg, S.; Thau, N.; Dengler, R.; Brinker, T.; Petri, S. Intracerebroventricular injection of encapsulated human mesenchymal cells producing glucagon-like peptide 1 prolongs survival in a mouse model of ALS. PLoS ONE 2012, 7, e36857. [Google Scholar] [CrossRef] [PubMed]
  26. Jin, H.J.; Bae, Y.K.; Kim, M.; Kwon, S.-J.; Jeon, H.B.; Choi, S.J.; Kim, S.W.; Yang, Y.S.; Oh, W.; Chang, J.W. Comparative analysis of human mesenchymal stem cells from bone marrow, adipose tissue, and umbilical cord blood as sources of cell therapy. Int. J. Mol. Sci. 2013, 14, 17986–18001. [Google Scholar] [CrossRef] [PubMed]
  27. Pittenger, M.F.; Discher, D.E.; Péault, B.M.; Phinney, D.G.; Hare, J.M.; Caplan, A.I. Mesenchymal stem cell perspective: Cell biology to clinical progress. NP Regen. Med. 2019, 4, 22. [Google Scholar] [CrossRef]
  28. Kyurkchiev, D.; Bochev, I.; Ivanova-Todorova, E.; Mourdjeva, M.; Oreshkova, T.; Belemezova, K.; Kyurkchiev, S. Secretion of immunoregulatory cytokines by mesenchymal stem cells. World J. Stem Cells 2014, 6, 552–570. [Google Scholar] [CrossRef] [PubMed]
  29. Park, C.W.; Kim, K.-S.; Bae, S.; Son, H.K.; Myung, P.-K.; Hong, H.J.; Kim, H. Cytokine secretion profiling of human mesenchymal stem cells by antibody array. Int. J. Stem Cells 2009, 2, 59–68. [Google Scholar] [CrossRef] [PubMed]
  30. Orive, G.; Santos, E.; Pedraz, J.L.; Hernández, R.M. Application of cell encapsulation for controlled delivery of biological therapeutics. Adv. Drug Deliv. Rev. 2014, 67–68, 3–14. [Google Scholar] [CrossRef] [PubMed]
  31. Orive, G.; Hernandez, R.M.; Gascón, A.R.; Calafiore, R.; Chang, T.M.; Vos, P.D.; Hortelano, G.; Hunkeler, D.; Lacik, I.; Shapiro, A.J.; et al. Cell encapsulation: Promise and progress. Nat. Med. 2003, 9, 104–107. [Google Scholar] [CrossRef] [PubMed]
  32. Orive, G.; Hernández, R.M.; Gascón, A.R.; Calafiore, R.; Chang, T.M.S.; de Vos, P.; Hortelano, G.; Hunkeler, D.; Lacík, I.; Pedraz, J.L. History, challenges and perspectives of cell microencapsulation. Trends Biotechnol. 2004, 22, 87–92. [Google Scholar] [CrossRef]
  33. Barnett, B.P.; Arepally, A.; Karmarkar, P.V.; Qian, D.; Gilson, W.D.; Walczak, P.; Howland, V.; Lawler, L.; Lauzon, C.; Stuber, M.; et al. Magnetic resonance–guided, real-time targeted delivery and imaging of magnetocapsules immunoprotecting pancreatic islet cells. Nat. Med. 2007, 13, 986–991. [Google Scholar] [CrossRef]
  34. Orive, G.; De Castro, M.; Kong, H.-J.; Hernández, R.M.; Ponce, S.; Mooney, D.J.; Pedraz, J.L. Bioactive cell-hydrogel microcapsules for cell-based drug delivery. J. Control. Release 2009, 135, 203–210. [Google Scholar] [CrossRef] [PubMed]
  35. Koh, E.; Jung, Y.C.; Woo, H.-M.; Kang, B.-J. Injectable alginate-microencapsulated canine adipose tissue-derived mesenchymal stem cells for enhanced viable cell retention. J. Vet. Med. Sci. 2017, 79, 492–501. [Google Scholar] [CrossRef] [PubMed]
  36. Kim, H.; Bae, C.; Kook, Y.-M.; Koh, W.-G.; Lee, K.; Park, M.H. Mesenchymal stem cell 3D encapsulation technologies for biomimetic microenvironment in tissue regeneration. Stem Cell Res. Ther. 2019, 10, 51. [Google Scholar] [CrossRef] [PubMed]
  37. Lopez-Mendez, T.B.; Santos-Vizcaino, E.; Blanco, F.J.; Pedraz, J.L.; Hernandez, R.M.; Orive, G. Improved control over MSCs behavior within 3D matrices by using different cell loads in both in vitro and in vivo environments. Int. J. Pharm. 2017, 533, 62–72. [Google Scholar] [CrossRef]
  38. Ashimova, A.; Yegorov, S.; Negmetzhanov, B.; Hortelano, G. Cell Encapsulation Within Alginate Microcapsules: Immunological Challenges and Outlook. Front. Bioeng. Biotechnol. 2019, 7, 380. [Google Scholar] [CrossRef] [PubMed]
  39. Trucillo, P. Biomaterials for Drug Delivery and Human Applications. Materials 2024, 17, 456. [Google Scholar] [CrossRef]
  40. Li, H.; Xu, X.; Wu, L.; Chen, X.; Akhter, H.; Wang, Y.; Song, P.; Liao, X.; Zhang, Z.; Li, Z.; et al. Recent progress and clinical applications of advanced biomaterials in cosmetic surgery. Regen. Biomater. 2023, 10, rbad005. [Google Scholar] [CrossRef] [PubMed]
  41. Gryshkov, O.; Mutsenko, V.; Tarusin, D.; Khayyat, D.; Naujok, O.; Riabchenko, E.; Nemirovska, Y.; Danilov, A.; Petrenko, A.Y.; Glasmacher, B. Coaxial Alginate Hydrogels: From Self-Assembled 3D Cellular Constructs to Long-Term Storage. Int. J. Mol. Sci. 2021, 22, 3096. [Google Scholar] [CrossRef]
  42. Tam, S.K.; Dusseault, J.; Bilodeau, S.; Langlois, G.; Hallé, J.; Yahia, L. Factors influencing alginate gel biocompatibility. J. Biomed. Mater. Res. Part A 2011, 98, 40–52. [Google Scholar] [CrossRef] [PubMed]
  43. Hached, F.; Vinatier, C.; Le Visage, C.; Gondé, H.; Guicheux, J.; Grimandi, G.; Billon-Chabaud, A. Biomaterial-assisted cell therapy in osteoarthritis: From mesenchymal stem cells to cell encapsulation. Best Pr. Res. Clin. Rheumatol. 2017, 31, 730–745. [Google Scholar] [CrossRef]
  44. de Vos, P.; Lazarjani, H.A.; Poncelet, D.; Faas, M.M. Polymers in cell encapsulation from an enveloped cell perspective. Adv. Drug Deliv. Rev. 2014, 67–68, 15–34. [Google Scholar] [CrossRef]
  45. Garate, A.; Ciriza, J.; Casado, J.G.; Blazquez, R.; Pedraz, J.L.; Orive, G.; Hernandez, R.M. Assessment of the Behavior of Mesenchymal Stem Cells Immobilized in Biomimetic Alginate Microcapsules. Mol. Pharm. 2015, 12, 3953–3962. [Google Scholar] [CrossRef] [PubMed]
  46. Paredes-Juarez, G.A.; de Haan, B.J.; Faas, M.M.; de Vos, P. A Technology Platform to Test the Efficacy of Purification of Alginate. Materials 2014, 7, 2087–2103. [Google Scholar] [CrossRef] [PubMed]
  47. Krishnan, R.; Ko, D.; Foster, C.E., III; Liu, W.; Smink, A.M.; de Haan, B.; De Vos, P.; Lakey, J.R. Immunological Challenges Facing Translation of Alginate Encapsulated Porcine Islet Xenotransplantation to Human Clinical Trials. Methods Mol. Biol. 2017, 1479, 305–333. [Google Scholar] [PubMed]
  48. Dorrington, M.G.; Fraser, I.D.C. NF-kappaB Signaling in Macrophages: Dynamics, Crosstalk, and Signal Integration. Front. Immunol. 2019, 10, 705. [Google Scholar] [CrossRef]
  49. Pearl, J.I.; Ma, T.; Irani, A.R.; Huang, Z.; Robinson, W.H.; Smith, R.L.; Goodman, S.B. Role of the Toll-like receptor pathway in the recognition of orthopedic implant wear-debris particles. Biomaterials 2011, 32, 5535–5542. [Google Scholar] [CrossRef]
  50. Vaure, C.; Liu, Y. A comparative review of toll-like receptor 4 expression and functionality in different animal species. Front. Immunol. 2014, 5, 316. [Google Scholar] [CrossRef] [PubMed]
  51. Vaithilingam, V.; Kollarikova, G.; Qi, M.; Larsson, R.; Lacik, I.; Formo, K.; Marchese, E.; Oberholzer, J.; Guillemin, G.J.; Tuch, B.E. Beneficial effects of coating alginate microcapsules with macromolecular heparin conjugates-in vitro and in vivo study. Tissue Eng. Part A 2014, 20, 324–334. [Google Scholar] [CrossRef]
  52. Paredes-Juarez, G.A.; Sahasrabudhe, N.M.; Tjoelker, R.S.; de Haan, B.J.; Engelse, M.A.; de Koning, E.J.P.; Faas, M.M.; de Vos, P. DAMP production by human islets under low oxygen and nutrients in the presence or absence of an immunoisolating-capsule and necrostatin-1. Sci. Rep. 2015, 5, 14623. [Google Scholar] [CrossRef]
  53. Ricard-Blum, S. The collagen family. Cold Spring Harb. Perspect. Biol. 2011, 3, a004978. [Google Scholar] [CrossRef] [PubMed]
  54. Wise, J.K.; Alford, A.I.; Goldstein, S.A.; Stegemann, J.P. Comparison of uncultured marrow mononuclear cells and culture-expanded mesenchymal stem cells in 3D collagen-chitosan microbeads for orthopedic tissue engineering. Tissue Eng. Part A 2014, 20, 210–224. [Google Scholar] [CrossRef]
  55. Chan, B.P.; Hui, T.Y.; Wong, M.Y.; Yip, K.H.K.; Chan, G.C.F. Mesenchymal stem cell-encapsulated collagen microspheres for bone tissue engineering. Tissue Eng. Part C Methods 2010, 16, 225–235. [Google Scholar] [CrossRef]
  56. Lee, H.; Woo, H.M.; Kang, B.J. Impact of collagen-alginate composition from microbead morphological properties to microencapsulated canine adipose tissue-derived mesenchymal stem cell activities. J. Biomater. Sci. Polym. Ed. 2018, 29, 1042–1052. [Google Scholar] [CrossRef]
  57. Li, Y.Y.; Lam, K.L.; Chen, A.D.; Zhang, W.; Chan, B.P. Collagen microencapsulation recapitulates mesenchymal condensation and potentiates chondrogenesis of human mesenchymal stem cells—A matrix-driven in vitro model of early skeletogenesis. Biomaterials 2019, 213, 119210. [Google Scholar] [CrossRef] [PubMed]
  58. Han, S.; Li, Y.Y.; Chan, B.P. Extracellular Protease Inhibition Alters the Phenotype of Chondrogenically Differentiating Human Mesenchymal Stem Cells (MSCs) in 3D Collagen Microspheres. PLoS ONE 2016, 11, e0146928. [Google Scholar] [CrossRef]
  59. Teong, B.; Manousakas, I.; Chang, S.J.; Huang, H.H.; Ju, K.-C.; Kuo, S.M. Alternative approach of cell encapsulation by Volvox spheres. Mater. Sci. Eng. C 2015, 55, 79–87. [Google Scholar] [CrossRef] [PubMed]
  60. Bussche, L.; Harman, R.M.; A Syracuse, B.; Plante, E.L.; Lu, Y.-C.; Curtis, T.M.; Ma, M.; Van de Walle, G.R. Microencapsulated equine mesenchymal stromal cells promote cutaneous wound healing in vitro. Stem Cell Res. Ther. 2015, 6, 66. [Google Scholar] [CrossRef] [PubMed]
  61. Batorsky, A.; Liao, J.; Lund, A.W.; Plopper, G.E.; Stegemann, J.P. Encapsulation of adult human mesenchymal stem cells within collagen-agarose microenvironments. Biotechnol. Bioeng. 2005, 92, 492–500. [Google Scholar] [CrossRef]
  62. Du, X.; Huang, F.; Zhang, S.; Yao, Y.; Chen, Y.; Chen, Y.; Huang, H.; Bai, B. Carboxymethylcellulose with phenolic hydroxyl microcapsules enclosinggene-modified BMSCs for controlled BMP-2 release In Vitro. Artif. Cells Nanomed. Biotechnol. 2017, 45, 1710–1720. [Google Scholar] [PubMed]
  63. Hashemi, M.; Kalalinia, F. Application of encapsulation technology in stem cell therapy. Life Sci. 2015, 143, 139–146. [Google Scholar]
  64. Nativel, F.; Renard, D.; Hached, F.; Pinta, P.-G.; D’arros, C.; Weiss, P.; Le Visage, C.; Guicheux, J.; Billon-Chabaud, A.; Grimandi, G. Application of Millifluidics to Encapsulate and Support Viable Human Mesenchymal Stem Cells in a Polysaccharide Hydrogel. Int. J. Mol. Sci. 2018, 19, 1952. [Google Scholar] [CrossRef]
  65. Alvarado-Velez, M.; Enam, S.F.; Mehta, N.; Lyon, J.G.; LaPlaca, M.C.; Bellamkonda, R.V. Immuno-suppressive hydrogels enhance allogeneic MSC survival after transplantation in the injured brain. Biomaterials 2021, 266, 120419. [Google Scholar]
  66. Xiang, P.M.K.; Zhi, H.W.; Aziz, N.S.; Hadri, N.A.; Ghazalli, N.F.; Yusop, N. Optimization of agarose-alginate hydrogel bead components for encapsulation and transportation of stem cells. J. Taibah Univ. Med. Sci. 2023, 18, 104–116. [Google Scholar]
  67. Boido, M.; Ghibaudi, M.; Gentile, P.; Favaro, E.; Fusaro, R.; Tonda-Turo, C. Chitosan-based hydrogel to support the paracrine activity of mesenchymal stem cells in spinal cord injury treatment. Sci. Rep. 2019, 9, 6402. [Google Scholar]
  68. Sharifi, F.; Hasani, M.; Atyabi, S.M.; Yu, B.; Ghalandari, B.; Li, D.; Ghorbani, F.; Irani, S.; Gholami, M. Mesenchymal stem cells encapsulation in chitosan and carboxymethyl chitosan hydrogels to enhance osteo-differentiation. Mol. Biol. Rep. 2022, 49, 12063–12075. [Google Scholar]
  69. Liu, T.; Li, J.; Shao, Z.; Ma, K.; Zhang, Z.; Wang, B.; Zhang, Y. Encapsulation of mesenchymal stem cells in chitosan/beta-glycerophosphate hydrogel for seeding on a novel calcium phosphate cement scaffold. Med. Eng. Phys. 2018, 56, 9–15. [Google Scholar] [CrossRef] [PubMed]
  70. Zhu, S.; Yu, C.; Liu, N.; Zhao, M.; Chen, Z.; Liu, J.; Li, G.; Huang, H.; Guo, H.; Sun, T.; et al. Injectable conductive gelatin methacrylate/oxidized dextran hydrogel encapsulating umbilical cord mesenchymal stem cells for myocardial infarction treatment. Bioact. Mater. 2022, 13, 119–134. [Google Scholar] [CrossRef]
  71. Gan, Y.; Li, S.; Li, P.; Xu, Y.; Wang, L.; Zhao, C.; Ouyang, B.; Tu, B.; Zhang, C.; Luo, L.; et al. A Controlled Release Codelivery System of MSCs Encapsulated in Dextran/Gelatin Hydrogel with TGF-beta3-Loaded Nanoparticles for Nucleus Pulposus Regeneration. Stem Cells Int. 2016, 2016, 9042019. [Google Scholar] [CrossRef]
  72. Liu, Z.Q.; Wei, Z.; Zhu, X.L.; Huang, G.Y.; Xu, F.; Yang, J.H.; Osada, Y.; Zrínyi, M.; Li, J.H.; Chen, Y.M. Dextran-based hydrogel formed by thiol-Michael addition reaction for 3D cell encapsulation. Colloids Surf. B Biointerfaces 2015, 128, 140–148. [Google Scholar] [CrossRef] [PubMed]
  73. Kim, C.J.; Park, E.-H.; Ryu, S.; Lee, Y.; Kim, E.; Kang, K.; Lee, K.Y.; Choo, E.-H.; Hwang, B.-H.; Youn, H.-J.; et al. MSC-Encapsulating in Situ Cross-Linkable Gelatin Hydrogels to Promote Myocardial Repair. ACS Appl. Bio Mater. 2020, 3, 1646–1655. [Google Scholar] [CrossRef]
  74. Tzouanas, S.N.; Ekenseair, A.K.; Kasper, F.K.; Mikos, A.G. Mesenchymal stem cell and gelatin microparticle encapsulation in thermally and chemically gelling injectable hydrogels for tissue engineering. J. Biomed. Mater. Res. Part A 2014, 102, 1222–1230. [Google Scholar] [CrossRef] [PubMed]
  75. Pangjantuk, A.; Kaokaen, P.; Kunhorm, P.; Chaicharoenaudomrung, N.; Noisa, P. 3D culture of alginate-hyaluronic acid hydrogel supports the stemness of human mesenchymal stem cells. Sci. Rep. 2024, 14, 4436. [Google Scholar] [CrossRef] [PubMed]
  76. Hao, S.; Tian, C.; Bai, Y.; Wu, L.; Hao, L.; Kuang, Y.; Yang, S.; Mao, H.; Gu, Z. Photo-crosslinkable hyaluronic acid microgels with reactive oxygen species scavenging capacity for mesenchymal stem cell encapsulation. Int. J. Biol. Macromol. 2023, 243, 124971. [Google Scholar] [CrossRef] [PubMed]
  77. Chung, C.; Burdick, J.A. Influence of three-dimensional hyaluronic acid microenvironments on mesenchymal stem cell chondrogenesis. Tissue Eng. Part A 2009, 15, 243–254. [Google Scholar] [CrossRef] [PubMed]
  78. Na, K.-S.; Fernandes-Cunha, G.M.; Varela, I.B.; Lee, H.J.; Seo, Y.A.; Myung, D. Effect of mesenchymal stromal cells encapsulated within polyethylene glycol-collagen hydrogels formed in situ on alkali-burned corneas in an ex vivo organ culture model. Cytotherapy 2021, 23, 500–509. [Google Scholar] [CrossRef]
  79. Jiang, Z.; Jiang, K.; Si, H.; McBride, R.; Kisiday, J.; Oakey, J. One Step Encapsulation of Mesenchymal Stromal Cells in PEG Norbornene Microgels for Therapeutic Actions. ACS Biomater. Sci. Eng. 2023, 9, 6322–6332. [Google Scholar] [CrossRef]
  80. Tee, B.C.; Desai, K.G.H.; Kennedy, K.S.; Sonnichsen, B.; Kim, D.-G.; Fields, H.W.; Mallery, S.R.; Schwendeman, S.P.; Sun, Z. Reconstructing jaw defects with MSCs and PLGA-encapsulated growth factors. Am. J. Transl. Res. 2016, 8, 2693–2704. [Google Scholar]
  81. Shen, N.; Polyanskaya, A.; Qi, X.; Al Othman, A.; Permyakova, A.; Volkova, M.; Mezentsev, A.; Durymanov, M. Modification of mesenchymal stromal cells with silibinin-loaded PLGA nanoparticles improves their therapeutic efficacy for cutaneous wound repair. Nanomedicine 2024, 61, 102767. [Google Scholar] [CrossRef] [PubMed]
  82. Xu, H.; Huang, S.; Wang, J.; Lan, Y.; Feng, L.; Zhu, M.; Xiao, Y.; Cheng, B.; Xue, W.; Guo, R. Enhanced cutaneous wound healing by functional injectable thermo-sensitive chitosan-based hydrogel encapsulated human umbilical cord-mesenchymal stem cells. Int. J. Biol. Macromol. 2019, 137, 433–441. [Google Scholar] [CrossRef] [PubMed]
  83. Choe, G.; Park, J.; Park, H.; Lee, J.Y. Hydrogel Biomaterials for Stem Cell Microencapsulation. Polymers 2018, 10, 997. [Google Scholar] [CrossRef] [PubMed]
  84. Halldorsson, S.; Lucumi, E.; Gomez-Sjoberg, R.; Fleming, R.M.T. Advantages and challenges of microfluidic cell culture in polydimethylsiloxane devices. Biosens. Bioelectron. 2015, 63, 218–231. [Google Scholar] [CrossRef]
  85. Zhang, H.; Zhang, L.; An, C.; Zhang, Y.; Shao, F.; Gao, Y.; Zhang, Y.; Li, H.; Zhang, Y.; Ren, C.; et al. Large-scale single-cell encapsulation in microgels through metastable droplet-templating combined with microfluidic-integration. Biofabrication 2022, 14, 035015. [Google Scholar] [CrossRef] [PubMed]
  86. Alkayyali, T.; Cameron, T.; Haltli, B.; Kerr, R.; Ahmadi, A. Microfluidic and cross-linking methods for encapsulation of living cells and bacteria—A review. Anal. Chim. Acta 2019, 1053, 1–21. [Google Scholar] [CrossRef]
  87. Nativel, F.; Smith, A.; Boulestreau, J.; Lépine, C.; Baron, J.; Marquis, M.; Vignes, C.; Le Guennec, Y.; Veziers, J.; Lesoeur, J.; et al. Micromolding-based encapsulation of mesenchymal stromal cells in alginate for intraarticular injection in osteoarthritis. Mater. Today Bio. 2023, 19, 100581. [Google Scholar] [CrossRef]
  88. Hui, T.; Cheung, K.; Cheung, W.; Chan, D.; Chan, B. In vitro chondrogenic differentiation of human mesenchymal stem cells in collagen microspheres: Influence of cell seeding density and collagen concentration. Biomaterials 2008, 29, 3201–3212. [Google Scholar] [CrossRef]
  89. Moshaverinia, A.; Chen, C.; Akiyama, K.; Ansari, S.; Xu, X.; Chee, W.W.; Schricker, S.R.; Shi, S. Alginate hydrogel as a promising scaffold for dental-derived stem cells: An in vitro study. J. Mater. Sci. Mater. Med. 2012, 23, 3041–3051. [Google Scholar] [CrossRef] [PubMed]
  90. An, C.; Liu, W.; Zhang, Y.; Pang, B.; Liu, H.; Zhang, Y.; Zhang, H.; Zhang, L.; Liao, H.; Ren, C.; et al. Continuous microfluidic encapsulation of single mesenchymal stem cells using alginate microgels as injectable fillers for bone regeneration. Acta Biomater. 2020, 111, 181–196. [Google Scholar] [CrossRef] [PubMed]
  91. Lalegul-Ulker, O.; Seker, S.; Elcin, A.E.; Elcin, Y.M. Encapsulation of bone marrow-MSCs in PRP-derived fibrin microbeads and preliminary evaluation in a volumetric muscle loss injury rat model: Modular muscle tissue engineering. Artif. Cells Nanomed. Biotechnol. 2019, 47, 10–21. [Google Scholar] [CrossRef]
  92. Wise, J.K.; Alford, A.I.; Goldstein, S.A.; Stegemann, J.P. Synergistic enhancement of ectopic bone formation by supplementation of freshly isolated marrow cells with purified MSC in collagen–chitosan hydrogel microbeads. Connect. Tissue Res. 2016, 57, 516–525. [Google Scholar] [CrossRef]
  93. Ansari, S.; Chen, C.; Hasani-Sadrabadi, M.M.; Yu, B.; Zadeh, H.H.; Wu, B.M.; Moshaverinia, A. Hydrogel elasticity and microarchitecture regulate dental-derived mesenchymal stem cell-host immune system cross-talk. Acta Biomater. 2017, 60, 181–189. [Google Scholar] [CrossRef] [PubMed]
  94. Skok, V.I. Channel-blocking mechanism ensures specific blockade of synaptic transmission. Neuroscience 1986, 17, 1–9. [Google Scholar] [CrossRef] [PubMed]
  95. Deng, Y.; Zhou, H.; Yan, C.; Wang, Y.; Xiao, C.; Gu, P.; Fan, X. In Vitro osteogenic induction of bone marrow stromal cells with encapsulated gene-modified bone marrow stromal cells and in vivo implantation for orbital bone repair. Tissue Eng. Part A 2014, 20, 2019–2029. [Google Scholar] [CrossRef] [PubMed]
  96. Kong, Y.; Zhao, Y.; Li, D.; Shen, H.; Yan, M. Dual delivery of encapsulated BM-MSCs and BMP-2 improves osteogenic differentiation and new bone formation. J. Biomed. Mater. Res. Part A 2019, 107, 2282–2295. [Google Scholar] [CrossRef]
  97. Moshaverinia, A.; Xu, X.; Chen, C.; Ansari, S.; Zadeh, H.H.; Snead, M.L.; Shi, S. Application of stem cells derived from the periodontal ligament or gingival tissue sources for tendon tissue regeneration. Biomaterials 2014, 35, 2642–2650. [Google Scholar] [CrossRef]
  98. Choi, S.; Kim, J.H.; Ha, J.; Jeong, B.I.; Jung, Y.C.; Lee, G.S.; Woo, H.M.; Kang, B.J. Intra-Articular Injection of Alginate-Microencapsulated Adipose Tissue-Derived Mesenchymal Stem Cells for the Treatment of Osteoarthritis in Rabbits. Stem Cells Int. 2018, 2018, 2791632. [Google Scholar] [CrossRef]
  99. Levit, R.D.; Landázuri, N.; Phelps, E.A.; Brown, M.E.; García, A.J.; Davis, M.E.; Joseph, G.; Long, R.; Safley, S.A.; Suever, J.D.; et al. Cellular encapsulation enhances cardiac repair. J. Am. Heart Assoc. 2013, 2, e000367. [Google Scholar] [CrossRef] [PubMed]
  100. de Jong, R.; van Hout, G.P.; Houtgraaf, J.H.; Kazemi, K.; Wallrapp, C.; Lewis, A.; Pasterkamp, G.; Hoefer, I.E.; Duckers, H.J. Intracoronary infusion of encapsulated glucagon-like peptide-1-eluting mesenchymal stem cells preserves left ventricular function in a porcine model of acute myocardial infarction. Circ. Cardiovasc. Interv. 2014, 7, 673–683. [Google Scholar] [CrossRef]
  101. Yu, J.; Du, K.T.; Fang, Q.; Gu, Y.; Mihardja, S.S.; Sievers, R.E.; Wu, J.C.; Lee, R.J. The use of human mesenchymal stem cells encapsulated in RGD modified alginate microspheres in the repair of myocardial infarction in the rat. Biomaterials 2010, 31, 7012–7020. [Google Scholar] [CrossRef] [PubMed]
  102. Mu, L.; Dong, R.; Li, C.; Chen, J.; Huang, Y.; Li, T.; Guo, B. ROS responsive conductive microspheres loaded with salvianolic acid B as adipose derived stem cell carriers for acute myocardial infarction treatment. Biomaterials 2025, 314, 122849. [Google Scholar] [CrossRef] [PubMed]
  103. Wang, Y.; Zhang, G.; Hou, Y.; Chen, J.; Wang, J.; Zou, C.; Li, D.; Li, H.; Zhang, Q.; Wang, A.; et al. Transplantation of microencapsulated Schwann cells and mesenchymal stem cells augment angiogenesis and improve heart function. Mol. Cell. Biochem. 2012, 366, 139–147. [Google Scholar] [CrossRef] [PubMed]
  104. Landázuri, N.; Levit, R.D.; Joseph, G.; Ortega-Legaspi, J.M.; Flores, C.A.; Weiss, D.; Sambanis, A.; Weber, C.J.; Safley, S.A.; Taylor, W.R. Alginate microencapsulation of human mesenchymal stem cells as a strategy to enhance paracrine-mediated vascular recovery after hindlimb ischaemia. J. Tissue Eng. Regen. Med. 2016, 10, 222–232. [Google Scholar] [CrossRef]
  105. Basile, G.; Qadir, M.M.F.; Mauvais-Jarvis, F.; Vetere, A.; Shoba, V.; Modell, A.E.; Pastori, R.L.; Russ, H.A.; Wagner, B.K.; Dominguez-Bendala, J. Emerging diabetes therapies: Bringing back the beta-cells. Mol. Metab. 2022, 60, 101477. [Google Scholar] [CrossRef]
  106. Razavi, M.; Ren, T.; Zheng, F.; Telichko, A.; Wang, J.; Dahl, J.J.; Demirci, U.; Thakor, A.S. Facilitating islet transplantation using a three-step approach with mesenchymal stem cells, encapsulation, and pulsed focused ultrasound. Stem Cell Res. Ther. 2020, 11, 405. [Google Scholar] [CrossRef]
  107. Badyra, B.; Sułkowski, M.; Milczarek, O.; Majka, M. Mesenchymal stem cells as a multimodal treatment for nervous system diseases. Stem Cells Transl. Med. 2020, 9, 1174–1189. [Google Scholar] [CrossRef] [PubMed]
  108. Mukai, T.; Sei, K.; Nagamura-Inoue, T. Mesenchymal stromal cells: Cell-based therapies for traumatic central nervous system injuries. J. Integr. Neurosci. 2022, 21, 44. [Google Scholar] [CrossRef]
  109. Stucky, E.C.; Schloss, R.S.; Yarmush, M.L.; Shreiber, D.I. Alginate micro-encapsulation of mesenchymal stromal cells enhances modulation of the neuro-inflammatory response. Cytotherapy 2015, 17, 1353–1364. [Google Scholar] [CrossRef] [PubMed]
  110. Barminko, J.; Kim, J.H.; Otsuka, S.; Gray, A.; Schloss, R.; Grumet, M.; Yarmush, M.L. Encapsulated mesenchymal stromal cells for in vivo transplantation. Biotechnol. Bioeng. 2011, 108, 2747–2758. [Google Scholar] [CrossRef] [PubMed]
  111. Momin, E.N.; Vela, G.; Zaidi, H.A.; Quinones-Hinojosa, A. The Oncogenic Potential of Mesenchymal Stem Cells in the Treatment of Cancer: Directions for Future Research. Curr. Immunol. Rev. 2010, 6, 137–148. [Google Scholar] [CrossRef] [PubMed]
  112. Kucerova, L.; Matuskova, M.; Hlubinova, K.; Altanerova, V.; Altaner, C. Tumor cell behaviour modulation by mesenchymal stromal cells. Mol. Cancer 2010, 9, 129. [Google Scholar] [CrossRef]
  113. Kleinschmidt, K.; Klinge, P.M.; Stopa, E.; Wallrapp, C.; Glage, S.; Geigle, P.; Brinker, T. Alginate encapsulated human mesenchymal stem cells suppress syngeneic glioma growth in the immunocompetent rat. J. Microencapsul. 2011, 28, 621–627. [Google Scholar] [CrossRef]
  114. Han, B.; Lu, Y.; Meng, B.; Qu, B. Cellular loss after allogenic hepatocyte transplantation. Transplantation 2009, 87, 1–5. [Google Scholar] [CrossRef] [PubMed]
  115. Jin, Y.; Shi, R.; Qi, T.; Li, Q.; Chen, C.; Gao, S.; Gao, F.; Yang, D.; Sun, G.; Xu, J.; et al. Adipose-derived stem cells show hepatic differentiation potential and therapeutic effect in rats with acute liver failure. Acta Biochim. Biophys. Sin. 2023, 55, 601–612. [Google Scholar] [CrossRef] [PubMed]
  116. Wang, J.; Qiao, P.; Dong, L.; Li, F.; Xu, T.; Xie, Q. Microencapsulated rBMMSCs/calcium phosphate cement for bone formation in vivo. Bio-Medical Mater. Eng. 2014, 24, 835–843. [Google Scholar] [CrossRef]
  117. Elahy, M.; Doschak, M.R.; Hughes, J.D.; Baindur-Hudson, S.; Dass, C.R. Alginate Bead-Encapsulated PEDF Induces Ectopic Bone Formation In Vivo in the Absence of Co-Administered Mesenchymal Stem Cells. Curr. Drug Targets 2018, 19, 467–478. [Google Scholar] [CrossRef] [PubMed]
  118. Moshaverinia, A.; Chen, C.; Xu, X.; Akiyama, K.; Ansari, S.; Zadeh, H.H.; Shi, S. Bone regeneration potential of stem cells derived from periodontal ligament or gingival tissue sources encapsulated in RGD-modified alginate scaffold. Tissue Eng. Part A 2013, 20, 611–621. [Google Scholar] [CrossRef]
  119. Moshaverinia, A.; Ansari, S.; Chen, C.; Xu, X.; Akiyama, K.; Snead, M.L.; Zadeh, H.H.; Shi, S. Co-encapsulation of anti-BMP2 monoclonal antibody and mesenchymal stem cells in alginate microspheres for bone tissue engineering. Biomaterials 2013, 34, 6572–6579. [Google Scholar] [CrossRef]
  120. McKinney, J.M.; Doan, T.N.; Wang, L.; Deppen, J.; Reece, D.S.; Pucha, K.A.; Ginn, S.; Levit, R.D.; Willett, N.J. Therapeutic efficacy of intra-articular delivery of encapsulated human mesenchymal stem cells on early stage osteoarthritis. Eur. Cell Mater. 2019, 37, 422–459. [Google Scholar] [CrossRef] [PubMed]
  121. Moshaverinia, A.; Xu, X.; Chen, C.; Akiyama, K.; Snead, M.L.; Shi, S. Dental mesenchymal stem cells encapsulated in an alginate hydrogel co-delivery microencapsulation system for cartilage regeneration. Acta Biomater. 2013, 9, 9343–9350. [Google Scholar] [CrossRef] [PubMed]
  122. Moshaverinia, A.; Chen, C.; Akiyama, K.; Xu, X.; Chee, W.W.L.; Schricker, S.R.; Shi, S. Encapsulated dental-derived mesenchymal stem cells in an injectable and biodegradable scaffold for applications in bone tissue engineering. J. Biomed. Mater. Res. Part A 2013, 101, 3285–3294. [Google Scholar]
  123. Karoubi, G.; Ormiston, M.L.; Stewart, D.J.; Courtman, D.W. Single-cell hydrogel encapsulation for enhanced survival of human marrow stromal cells. Biomaterials 2009, 30, 5445–5455. [Google Scholar]
  124. Sayyar, B.; Dodd, M.; Wen, J.; Ma, S.; Marquez-Curtis, L.; Janowska-Wieczorek, A.; Hortelano, G. Encapsulation of factor IX-engineered mesenchymal stem cells in fibrinogen-alginate microcapsules enhances their viability and transgene secretion. J. Tissue Eng. 2012, 3, 2041731412462018. [Google Scholar]
  125. Gurruchaga, H.; Ciriza, J.; Saenz Del Burgo, L.; Rodriguez-Madoz, J.R.; Santos, E.; Prosper, F.; Hernández, R.M.; Orive, G.; Pedraz, J.L. Cryopreservation of microencapsulated murine mesenchymal stem cells genetically engineered to secrete erythropoietin. Int. J. Pharm. 2015, 485, 15–24. [Google Scholar] [PubMed]
  126. Schwieger, J.; Hamm, A.; Gepp, M.M.; Schulz, A.; Hoffmann, A.; Lenarz, T.; Scheper, V. Alginate-encapsulated brain-derived neurotrophic factor–overexpressing mesenchymal stem cells are a promising drug delivery system for protection of auditory neurons. J. Tissue Eng. 2020, 11, 2041731420911313. [Google Scholar] [PubMed]
  127. Goren, A.; Dahan, N.; Goren, E.; Baruch, L.; Machluf, M. Encapsulated human mesenchymal stem cells: A unique hypoimmunogenic platform for long-term cellular therapy. FASEB J. 2010, 24, 22–31. [Google Scholar] [PubMed]
  128. Trouche, E.; Girod Fullana, S.; Mias, C.; Ceccaldi, C.; Tortosa, F.; Seguelas, M.H.; Calise, D.; Parini, A.; Cussac, D.; Sallerin, B. Evaluation of alginate microspheres for mesenchymal stem cell engraftment on solid organ. Cell Transplant. 2010, 19, 1623–1633. [Google Scholar]
  129. Leijs, M.J.; Villafuertes, E.; Haeck, J.C.; Koevoet, W.J.; Fernandez-Gutierrez, B.; Hoogduijn, M.J.; Verhaar, J.A.; Bernsen, M.R.; van Buul, G.M.; van Osch, G.J. Encapsulation of allogeneic mesenchymal stem cells in alginate extends local presence and therapeutic function. Eur. Cell Mater. 2017, 33, 43–58. [Google Scholar] [CrossRef]
  130. Kin, K.; Yasuhara, T.; Date, I. Encapsulation of Mesenchymal Stem Cells: Dissecting the Underlying Mechanism of Mesenchymal Stem Cell Transplantation Therapy. Neurosci. Insights 2020, 15, 2633105520959064. [Google Scholar]
  131. Azadi, S.A.; Vasheghani-Farahani, E.; Hashemi-Najafbabadi, S.; Godini, A. Co-encapsulation of pancreatic islets and pentoxifylline in alginate-based microcapsules with enhanced immunosuppressive effects. Prog. Biomater. 2016, 5, 101–109. [Google Scholar] [CrossRef] [PubMed]
  132. Acarregui, A.; Herrán, E.; Igartua, M.; Blanco, F.J.; Pedraz, J.L.; Orive, G.; Hernandez, R.M. Multifunctional hydrogel-based scaffold for improving the functionality of encapsulated therapeutic cells and reducing inflammatory response. Acta Biomater. 2014, 10, 4206–4216. [Google Scholar] [CrossRef]
  133. Dang, T.T.; Thai, A.V.; Cohen, J.; Slosberg, J.E.; Siniakowicz, K.; Doloff, J.C.; Ma, M.; Hollister-Lock, J.; Tang, K.M.; Gu, Z.; et al. Enhanced function of immuno-isolated islets in diabetes therapy by co-encapsulation with an anti-inflammatory drug. Biomaterials 2013, 34, 5792–5801. [Google Scholar] [CrossRef] [PubMed]
  134. Konradi, R.; Acikgoz, C.; Textor, M. Polyoxazolines for Nonfouling Surface Coatings—A Direct Comparison to the Gold Standard PEG. Macromol. Rapid Commun. 2012, 33, 1663–1676. [Google Scholar] [CrossRef] [PubMed]
  135. Li, G.; Cheng, G.; Xue, H.; Chen, S.; Zhang, F.; Jiang, S. Ultra low fouling zwitterionic polymers with a biomimetic adhesive group. Biomaterials 2008, 29, 4592–4597. [Google Scholar] [CrossRef] [PubMed]
  136. Sanchez-Cano, C.; Carril, M. Recent Developments in the Design of Non-Biofouling Coatings for Nanoparticles and Surfaces. Int. J. Mol. Sci. 2020, 21, 1007. [Google Scholar] [CrossRef] [PubMed]
  137. Lorson, T.; Lübtow, M.M.; Wegener, E.; Haider, M.S.; Borova, S.; Nahm, D.; Jordan, R.; Sokolski-Papkov, M.; Kabanov, A.V.; Luxenhofer, R. Poly(2-oxazoline)s based biomaterials: A comprehensive and critical update. Biomaterials 2018, 178, 204–280. [Google Scholar] [CrossRef]
  138. Santos, E.; Pedraz, J.L.; Hernández, R.M.; Orive, G. Therapeutic cell encapsulation: Ten steps towards clinical translation. J. Control. Release 2013, 170, 1–14. [Google Scholar] [CrossRef] [PubMed]
  139. Garate, A.; Santos, E.; Pedraz, J.L.; Hernández, R.M.; Orive, G. Evaluation of different RGD ligand densities in the development of cell-based drug delivery systems. J. Drug Target. 2015, 23, 806–812. [Google Scholar] [CrossRef] [PubMed]
Figure 1. MSCs microencapsulation and their application in different diseases.
Figure 1. MSCs microencapsulation and their application in different diseases.
Cells 14 00149 g001
Table 1. Polymers have been used in MSC microencapsulation and their characteristics.
Table 1. Polymers have been used in MSC microencapsulation and their characteristics.
MaterialBiocompatibilityMechanical StrengthPermeabilityDegradationImmunomodulationClinical ChallengesAdvantagesDisadvantages
AlginateHighModerateGoodDegrades variably based on cross-linkingLow/moderatePoor reproducibility and purity standardsBiocompatible, easy to modifyImmunogenic impurities; limited mechanical strength
GelatinModerateLowModerateEnzymatically degradableModerateRapid degradation in vivoBiodegradable, good cell adhesionWeak mechanical properties
ChitosanModerateModerateLowSlow enzymatic degradationModerateLow solubility at neutral pHAntimicrobial, supports cell attachmentSolubility issues; moderate biocompatibility
Polyethylene Glycol (PEG)HighHighAdjustableNon-degradable or slow (depending on formulation)LowSynthetic nature raises regulatory hurdlesTunable properties, high mechanical strengthExpensive, non-biodegradable
Hyaluronic AcidHighLowHighEnzymatically degradableLow/moderateRapid degradation unless chemically modifiedExcellent biocompatibilityPoor mechanical strength
CollagenHighLowModerateEnzymatically degradableLowBatch variability and weak mechanical propertiesExcellent biocompatibility, natural ECM mimicLimited stability
PLGA (Poly (lactic-co-glycolic acid))HighHighAdjustableDegrades via hydrolysis into lactic and glycolic acidLowPotential acid accumulation causing inflammationTunable degradation rateExpensive, inflammatory degradation products
AgaroseModerateModerateLowNon-degradableLowLimited mechanical tunabilityEasy to handle, good thermal stabilityNon-biodegradable, limited cell adhesion
CelluloseHighModerateModerateNon-degradable or slowly enzymaticLowLimited modification options for specific applicationsAbundant, biocompatible, supports cell adhesionPoor biodegradability, difficult to process
DextranHighLowHighRapid enzymatic degradationLowRapid degradation unless chemically modifiedExcellent biocompatibility, easy to functionalizeWeak mechanical properties, short in vivo stability
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Abbas, S.E.M.; Maged, G.; Wang, H.; Lotfy, A. Mesenchymal Stem/Stromal Cells Microencapsulation for Cell Therapy. Cells 2025, 14, 149. https://doi.org/10.3390/cells14030149

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Abbas SEM, Maged G, Wang H, Lotfy A. Mesenchymal Stem/Stromal Cells Microencapsulation for Cell Therapy. Cells. 2025; 14(3):149. https://doi.org/10.3390/cells14030149

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Abbas, Sharaf Eldeen M., Ghada Maged, Hongjun Wang, and Ahmed Lotfy. 2025. "Mesenchymal Stem/Stromal Cells Microencapsulation for Cell Therapy" Cells 14, no. 3: 149. https://doi.org/10.3390/cells14030149

APA Style

Abbas, S. E. M., Maged, G., Wang, H., & Lotfy, A. (2025). Mesenchymal Stem/Stromal Cells Microencapsulation for Cell Therapy. Cells, 14(3), 149. https://doi.org/10.3390/cells14030149

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