Search Results (96)

Post-traumatic osteoarthritis (PTOA) is a rapidly progressing joint disorder initiated by acute injury, characterized by persistent inflammation, chondrocyte dysfunction, and extracellular matrix (ECM) degradation. Despite its clinical burden, effective disease-modifying therapies are lacking. Increasing evidence suggests that the ubiquitin–proteasome system, particularly E3 ubiquitin ligases, plays a pivotal role in regulating key pathogenic pathways involved in PTOA and represents a potentially druggable regulatory axis. In this review, we provide a comprehensive overview of the emerging roles of E3 ubiquitin ligases in PTOA, highlighting their involvement in inflammatory signaling, chondrocyte fate regulation, and cartilage matrix remodeling. We further integrate the current findings into a unified framework, in which E3 ligases act as central regulatory nodes linking injury-induced molecular responses to chronic joint degeneration. Importantly, we emphasize the pharmacological and translational potential of targeting E3 ubiquitin ligases as a novel therapeutic strategy. Recent advances in small-molecule modulators, gene-based interventions, and proteolysis-targeting chimeras (PROTACs) highlight the druggability of this regulatory system and provide new opportunities for disease-modifying treatment in PTOA. We also discuss the current challenges, including context-dependent effects, limited PTOA-specific validation, and delivery barriers. Overall, this review provides a comprehensive and therapeutically oriented perspective on E3 ubiquitin ligases in PTOA and highlights their potential as promising targets for pharmacological intervention and disease-modifying therapy. Full article

Objectives: To evaluate the effectiveness and durability of matrix-associated autologous chondrocyte implantation with periosteal flap (pMACI) in treating knee cartilage defects using clinical scores and MRI evaluations. Methods: Data were collected from 37 knees of 17 patients, with a mean follow-up of 5 years (range: 0.1–20 years). Clinical outcomes were assessed using the Lysholm Knee Scoring Scale (LKS) and Knee Injury and Osteoarthritis Outcome Score (KOOS). Tissue quality was quantitatively evaluated using MRI T1ρ and T2 mapping (biochemical) and MR observation of cartilage repair tissue: MOCART 2.0 (morphological). A linear mixed model was used to identify factors affecting outcomes, including etiology (trauma, OCD, OA), graft site, and defect size. Results: At the 20-year follow-up, clinical scores remained significantly improved from baseline (mean LKS: 55.6 to 86.5; KOOS: 37.8 to 70.8). The biochemical MRI parameters (T1ρ and T2 values) stabilized at levels comparable to native cartilage across all etiologies and sites (p = 0.326 and 0.412, respectively), indicating stable long-term tissue quality. In contrast, the MOCART 2.0 scores significantly declined over time (annual rate: −1.14 points; p < 0.001). Etiology was a significant factor; the OA group showed significantly lower clinical and MOCART scores compared to the trauma/OCD groups (p < 0.05). However, no significant differences were found in LKS and KOOS based on graft site (p = 0.489) or defect size (p > 0.05). Conclusions: pMACI may be a highly durable treatment capable of maintaining biological tissue quality and providing clinical benefits for two decades. The observed morphological deterioration after 20 years likely reflects joint-wide aging—especially in OA cases—rather than graft failure, highlighting the importance of long-term MRI monitoring. Full article

Cartilage is an important yet vulnerable tissue with limited self-healing capacity, where damage often progresses to joint degeneration, which eventually leads to severe osteoarthritis (OA). Current tissue engineering strategies focus on biocompatible scaffolds for cartilage regeneration, particularly amnion (or amniotic membrane), emerging as a promising biomaterial due to its wide availability, low immunogenicity, and naturally derived microenvironment that is advantageous for cartilage regeneration. This systematic review aims to evaluate the existing evidence on the efficacy of amnion as a tissue scaffolding material for cartilage regeneration in both preclinical and clinical studies. Using terms such as “cartilage damage”, “cartilage injuries”, “amnion” and “amniotic membrane”, 19 relevant studies were identified across three major databases (PubMed, Scopus and Web of Science) until 25 December 2025. All preclinical and clinical studies that utilized amnion for cartilage repair or as cartilage tissue engineering scaffolding materials were included. Evidence quality was assessed using the OHAT and MINORS risk of bias tool. This study is prospectively registered in the PROSPERO database under the ID 1178444. The findings consistently indicate that amniotic scaffolds, regardless of processing methods or cell seeding, yield favorable outcomes without adverse effects across different species. In vitro analysis revealed that treatment groups with amnion show better cell attachment, viability, and proliferation, and higher content of cartilage-related markers expressed by the seeded cells, either chondrocyte, bone marrow-derived mesenchymal stem cells (MSCs), adipose tissue-derived MSCs, placenta-derived MSCs, umbilical cord-derived MSCs, amniotic MSCs or amniotic epithelial cells. In in vivo and ex vivo studies, amnion-treated groups demonstrated improved quality of the treated cartilage, with better integration, as indicated by higher histological scores and the presence of type II collagen (COL-II). There was an inconsistency in the reporting of cartilage defect dimensions in the in vivo models across the different studies. Nevertheless, the outcome measurements were consistently reported with histological analysis, with or without International Cartilage Repair Society (ICRS) scoring and immunohistochemistry (IHC) analysis, across the studies. Clinically, most subjects show improvement in the Knee Injury and Osteoarthritis Outcome Score (KOOS) Sports and Recreation score and KOOS Quality of Life score, as well as reduced Visual Analogue Scale (VAS) average and maximum pain scores. In conclusion, preclinical and clinical studies support amnion as an ideal scaffold material for cartilage tissue engineering and regeneration. Future research should focus on optimizing and standardizing amnion scaffold preparation at a production scale to facilitate the translation of these positive outcomes into clinical applications. This study is funded by the Ministry of Higher Education Malaysia via Prototype Research Grant Scheme (PRGS/1/2021/SKK01/UM/02/1) and UM International Collaboration Grant—2023 SATU Joint Research Scheme Program: ST007-2024. Full article

Osteoarthritis (OA) is the most common multifactorial joint disease characterized by progressive cartilage degradation and impaired tissue repair. Osteochondral defects represent a major clinical challenge within OA, as damage to cartilage and underlying bone can initiate degenerative changes and contribute to joint deterioration. The Wnt/β-catenin signaling pathway plays an important role in OA pathogenesis, and its dysregulation contributes to chondrocyte catabolism and cartilage loss. NOTUM, an extracellular Wnt inhibitor, has emerged as a potential therapeutic modulator capable of restoring signaling balance and promoting cartilage homeostasis. This study aimed to evaluate the efficacy of NOTUM compared with hyaluronic acid (HA), human adipose-derived mesenchymal stromal cells (hAd-MSCs), and Colchicine in a rabbit osteochondral defect model relevant to osteoarthritis. Twenty-seven New Zealand White rabbits underwent standardized femoral condyle injury and received single-dose treatments. Serum levels of cartilage biomarkers—Procollagen Type IIA N-terminal Propeptide (PIIANP) and Cartilage Oligomeric Matrix Protein (COMP)—were measured by ELISA at 4, 6, and 8 weeks post-surgery, and histological repair at week 12 was assessed using the modified O’Driscoll scoring system. NOTUM treatment significantly increased PIIANP and decreased COMP levels compared with HA, indicating enhanced cartilage synthesis and reduced degradation. Histological scores confirmed superior surface morphology and tissue composition in NOTUM-treated joints. These findings suggest that NOTUM performs a protective and regenerative effect through Wnt/β-catenin modulation, supporting the conclusion that it enhances osteochondral defect repair and motivating further studies of NOTUM as an OA therapy. Full article

Type II collagen (Col2), a crucial structural protein in hyaline cartilage, is essential for cartilage integrity and facilitating injury repair. However, research on recombinant type II collagen still faces many challenges, such as structure and yield, which limit the application of recombinant Col2 in biomedical fields. In this study, we achieved high-yield expression of full-length human Col2 (rhCol2) in CHO cells. The physical and chemical properties of rhCol2 were very close to native Col2, including molecular weight, triple helix structure, thermal stability and self-assembly capacity. Functional assays of primary chondrocytes have demonstrated that rhCol2 can effectively promote chondrocyte proliferation and increase the expression levels of cartilage-specific genes (Col2a1, Aggrecan, and Sox-9). Moreover, a cartilage defect model was surgically created in SD rats demonstrated that rhCol2 significantly enhanced cartilage repair, and the severity of the defect was assessed through histological and micro-CT analyses. Human chondrocytes were utilized to compare the effects of different collagens and verified through a series of functional experiments. In conclusion, these findings indicate that rhCol2 is an effective biomaterial and is expected to promote the application of recombinant collagen in the field of cartilage repair. Full article

Intervertebral disc degeneration is a leading cause of chronic back pain, with existing treatments focusing on symptom management rather than true tissue repair. Cellular therapies—such as platelet-rich plasma (PRP), autologous chondrocytes, and mesenchymal stem cells (MSCs)—have emerged as promising strategies for disc regeneration. In this study, fifteen New Zealand white rabbits underwent fluoroscopy-guided needle puncture of the L4-L5 discs and were allocated to receive PRP alone, PRP-chondrocytes, or PRP-MSCs eight weeks later, while the L3-L4 disc served as a healthy internal control. At 16 weeks post-injury, histological scoring revealed significant improvements in annular integrity, cellularity, and matrix composition in all treated groups compared with untreated lesions, with the greatest gains observed in the PRP-chondrocytes arm, intermediate effects with PRP-MSCs, and more modest changes with PRP alone. Complementary RT-qPCR analysis of COL2A1 and COL10A1 expression confirmed a shift toward a more regenerative phenotype, marked by enhanced COL2A1 and reduced COL10A1 levels, which was most pronounced in the PRP-chondrocytes arm. Despite these advances, none of the interventions fully restored the healthy disc architecture, underscoring the complexity of disc repair. These findings support the potential of combining PRP with chondrocytes or MSCs for intervertebral disc regeneration and demonstrate the need for further optimization of cell doses, PRP formulations, and delivery protocols before clinical translation. Full article

Osteoarthritis (OA) is one of the most common joint diseases worldwide, which is characterized by degenerative changes in articular cartilage and secondary osteophyte formation. Numerous factors influence OA, including aging, obesity, joint injury and chronic overloading. Among them, the senescence of chondrocytes is one of the key factors leading to OA. Chondrocyte senescence can trigger inflammatory responses, extracellular matrix (ECM) degradation, mitochondrial dysfunction and oxidative stress (OS), and autophagy. Sirtuin 6 (SIRT6), as a deacetylase related to aging, can regulate chondrocyte senescence and plays a certain part in OA. SIRT6 regulates the number and membrane integrity of mitochondria, alleviates excessive Reactive Oxygen Species (ROS) in mitochondria and reduces inflammation-mediated mitochondrial damage. In addition, SIRT6 can also regulate the activity of antioxidant enzymes, inhibit excessive ROS induced by inflammatory factors, and alleviate OS. However, as aging progresses, the activity of SIRT6 will decrease. Activating the activity of SIRT6 becomes a potential therapeutic target and has a certain alleviating effect on the development of OA. The supplementation of nicotinamide adenine dinucleotide (NAD+) precursors and SIRT6-specific activators can increase SIRT6, alleviate chondrocyte senescence, and reduce OA. This paper aims to focus on mitochondrial dysfunction and OS to explore SIRT6’s effects on OA chondrocytes’ senescence under aging and summarize the potential therapeutic targets for activating SIRT6 to provide assistance for the improvement of OA. Full article

Background: Intervertebral disc degeneration (IVDD) is closely linked to low back pain (LBP), a leading cause of disability worldwide. IVDD is characterized by the loss of proteoglycans (PGs), extracellular matrix (ECM) degradation, and reduced hydration of the nucleus pulposus (NP). Extracellular vesicles (EVs) derived from human umbilical cord mesenchymal stem cells (hUC-MSCs) exhibit tissue repair and immunomodulatory effects and are emerging as promising cell-free therapeutics. Methods: We established a rat IVDD model via fluoroscopy-guided needle puncture of three consecutive coccygeal discs and confirmed degeneration through Alcian Blue and hematoxylin & eosin (H&E) staining. The gene expression of inflammatory and pain markers (ADRβ2, COMP, CXCL1, COX2, PPTA, MMP13, YKL40) was measured by qPCR. Subsequently, we implanted hUC-MSCs or EVs to evaluate their reparative potential. Results: Upregulation of inflammatory and pain genes in IVDD was associated with an immunomodulatory response. Tracking DiI-labelled hUC-MSCs and EVs revealed enhanced survival of hUC-MSCs, retention of EVs, and dispersion within rat tail discs; EVs showed greater retention than hUC-MSCs. Implanted EVs were internalized by NP cells and remained within degenerative IVDs. EVs passively diffused, accumulated at the injury site, interacted with host cells, and enhanced function, as shown by increased expression of human chondrocyte-related markers (SOX9, TGFβ1, TGFβ2, COL2) compared to hUC-MSC treatment. Histological analysis of two weeks post-transplantation showed NP cellular patterns resembling chondromas in treated discs. EVs integrated into and distributed within degenerated NP regions, with greater glycosaminoglycan (GAG) content. Conclusions: Overall, hUC-MSC EVs demonstrated superior regenerative capacity, supporting a safe, cell-free strategy for disc repair. Full article

Calvarial suture skeletal stem cells (Su-SSCs) are a distinct stem cell population for craniofacial bone formation by intramembranous ossification, compared to long bone periosteal SSCs (LB-PSSCs) with endochondral (osteochondrogenic) ossification. However, whether SSC intrinsic or extrinsic factors affect their differentiation process has not been well elucidated. Here, using an inducible Prx1-CreER-EGFP^+/−;Rosa26-tdTomato mouse model, we observed that endogenous Prx1⁺ Su-SSCs and their orthotopic transplantation into calvarial injury do not form cartilage intermediates at the injury sites, while the transplantation of Prx1⁺ LB-PSSCs into LB injury induces osteochondrogenic differentiation, respectively. However, the heterotopic transplantation of Prx1⁺ Su-SSCs (Su-SSCs into LB injury) showed some surprising findings that the transplanted Su-SSCs acquire new chondrocyte differentiation properties at the LB injury sites, although the heterotopic-transplanted Prx1⁺ LB-PSSCs maintained their endochondral ossification properties at the calvarial injury sites. Further, a comparative single-cell transcriptomic analysis of LB-PSSCs and Su-SSCs revealed that Su-SSCs express a higher set of anti-chondrogenic genes, such as Wnt5b, Twist1 while LB-PSSCs highly express chondrogenic Hoxa-9, Hoxc-9, Hoxa-10, Hoxc-10, and Comp genes. We also found that the heterotopic transplantation of LB-PSSCs into calvarial injury enhances bone healing in vivo. Taken together, these findings suggest that LB-PSSCs have high regenerative capability with invariable endochondral ossification even after the heterotopic transplantation but Su-SSCs are more flexible and regulated by the local bone environment. The transplantation of periosteal SSCs will be a promising method for large craniofacial bone defects. Full article

Osteoarthritis (OA), the most common form of arthritis, affects the whole synovial joint. Post-traumatic osteoarthritis (PTOA) is an important subtype of OA which develops after joint injury. The anti-PTOA effects of iontophoretic liposome-encapsulated strontium ranelate (L-SR) combined with low-intensity pulsed ultrasound (LIPUS) were examined by a culture of human OA chondrocytes (HOACs) in alginate beads and verified on an anterior cruciate ligament transection PTOA rat model. The aim of this study is to evaluate and establish an anti-PTOA therapy combined with L-SR, transdermal iontophoresis, and LIPUS. Treatment with 10⁻⁴ M L-SR with LIPUS-enhanced type II collagen and glycosaminoglycans (GAGs) as L-SR with LIPUS reduced the MMP-13, IL-1β, and TNF-α in HOACs. Iontophoretic L-SR at 15 mg with LIPUS increased the weight bearing, exercise endurance, GAG density, and type II collagen intensity, while L-SR with or without LIPUS further decreased MMP13 and proinflammatory cytokines in vivo. The RBC, WBC, and serum biochemistry values were not significantly affected by the treatments. Liposome encapsulation and iontophoresis reinforce the anti-PTOA effects of SR and the addictive LIPUS further improves weight-bearing and endurance performance in the rats with PTOA. Thus, iontophoretic L-SR with LIPUS could be a potential therapy for PTOA. Full article

Gout and calcium pyrophosphate crystal deposition disease (CPPD) are frequently associated with comorbid disorders, including coronary artery disease and osteoarthritis, in which ectopic calcification with basic calcium phosphate crystals commonly affects arteries and articular cartilage, respectively. Accepting the 2024 G-CAN Gold Medal, I review my research philosophy for translational etiopathogenesis investigation in gout and CPPD, atherosclerosis, responses to arterial injury, and osteoarthritis. Since molecular homeostasis points to pathophysiology and vice versa, I have followed selected molecular players and pathways to phenotypes. Typically, behind each disease target is another target. Illuminating passageways between etiopathogenic pathways is especially productive when using approaches beyond conventional “omics” to reveal the impact of specific post-translational protein modifications, and changes in protein conformation, complex assembly, and interactomes. Highlighting these concepts, I review my past studies on specific molecular pathways, and current perspectives for the following: (i) PP_i, NPP1, ANKH, and transglutaminase 2 (TG2); (ii) relationships between NPP1, ANKH, Vanin-1 Pantetheinase, and ectopic chondrogenesis; (iii) intersections between adenosine, AMPK, CXCL8 and its receptor CXCR2, the receptor for advanced glycation endproducts (RAGE) and chondrocyte hypertrophy; (iv) lubricin homeostasis and proteolysis; (v) receptor for advanced glycation endproducts (RAGE) and TG2-catalyzed post-translational calgranulin modification; (vi) complement activation and C5b-9 assembly, and the nucleotide-bound conformation of TG2. The inescapable conclusion is that these molecular pathways tightly knit crystal arthropathy with both arterial and osteoarthritis comorbidity. Full article

Developing a functional tissue-engineered articular cartilage remains a challenge to improving clinical treatment of cartilage injury and joint-related degenerative disease. The dynamic self-regenerating cartilage (dSRC) approach presented here encourages autologous chondrocytes to generate their own matrix rather than imposing a matrix upon them. dSRC constructs were grown for 12 weeks under hypoxic conditions in reciprocating motion. Biochemical composition was evaluated, specifically water, collagen, and proteoglycan content. Speckle rHEologicAl micRoscopy (SHEAR) was utilized for spatially resolved evaluation of the shear modulus in engineered cartilage. Histological and immunohistochemical analyses of dSRC were also performed. The maturation of the dSRC matrix results in collagen and glycosaminoglycan (GAG) levels around 50% of those in native cartilage. SHEAR images demonstrate an increase in shear modulus of the matrix to ~20% that of native cartilage after 12 weeks. Histological support for excellent collagen and GAG production was evident, and immunohistochemistry showed a high preference for hyaline-like type II collagen in the neomatrix. A decrease in chondrocyte density occurred from an initial hypercellular matrix to that approaching native cartilage by 12 weeks. While this maturation of dSRC in vitro should not be construed as an absolute prediction of in vivo performance, these results are encouraging, representing a potential new cartilage repair and regeneration approach. Full article

Objective: Joint injury precipitates post-traumatic osteoarthritis (PTOA) via chondrocyte mitochondrial oxidative damage. Carbon monoxide (CO) is a small molecule with potent antioxidant and mitochondrial benefits in other tissues that have not been explored in healthy chondrocytes. We hypothesized that CO would subvert the mitochondrial effects of articular cartilage injuries upon resident chondrocytes. Design: We evaluated intra-articular delivery of a novel carbon monoxide-containing foam (COF). We used in vitro impact injuries to explore mitochondrial and redox endpoints after CO exposure. We then applied intra-articular injections of COF or control room air foam (RAF) to assess safety, efficacy, and other intra-articular responses. Results: COF increased the expression of HO1 and mitofusin-1 within 1 h and this increase was sustained for 12 h in vitro. COF increased chondrocyte mitochondrial respiration by 40% and increased reduced (not oxidized) thiols by 50% following in vitro injury to osteochondral explants. After cartilage injury, COF prevented the formation of 3-nitrotyrosine and the loss of articular chondrocyte mitochondria. When injected intra-articularly, COF was retained for 24 h post-injection in mouse stifle joints. It increased HO1 in those joints, enhanced reduced thiol levels in rabbit stifle joints, and exhibited no toxicity 1 and 4 weeks after injection. Conclusions: This study supports the hypothesis that CO functions as an antioxidant for articular chondrocytes by supporting mitochondria and intracellular GSH in the presence or absence of cartilage injury. Challenges in delivering exogenous CO have limited its preclinical development, but new CO-releasing materials like COF may enable new examinations of this promising small molecule. Full article

Traumatic or degenerative defects of articular cartilage impair joint function, and the treatment of articular cartilage damage remains a challenge. By mimicking the cartilage extracellular matrix (ECM), exosome-seeded cryogels may enhance cell proliferation and chondral repair. ECM-based cryogels were cryopolymerized with gelatin, chondroitin sulfate, and various concentrations (0%, 0.3%, 0.5%, and 1%) of hyaluronic acid (HA), and their water content, swelling ratio, porosity, mechanical properties, and effects on cell viability were evaluated. The regenerative effects of bone marrow-derived mesenchymal stem cell (BM-MSC)-derived exosome (at a concentration of 10⁶ particles/mL)-seeded 0.3% HA cryogels were assessed in vitro and in surgically induced male New Zealand rabbit cartilage defects in vivo. The water content, swelling ratio, and porosity of the cryogels significantly (p < 0.05) increased and the Young’s modulus values of the cryogels decreased with increasing HA concentrations. MTT assays revealed that the developed biomaterials had no cytotoxic effects. The optimal cryogel composition was 0.3% HA, and the resulting cryogel had favorable properties and suitable mechanical strength. Exosomes alone and exosome-seeded cryogels promoted chondrocyte proliferation (with cell optical densities that were 58% and 51% greater than that of the control). The cryogel alone and the exosome-seeded cryogel facilitated ECM deposition and sulfated glycosaminoglycan synthesis. Although we observed cartilage repair via Alcian blue staining with both the cryogel alone and the exosome-seeded cryogel, the layered arrangement of the chondrocytes was superior to that of the control chondrocytes when exosome-seeded cryogels were used. This study revealed the potential value of using BM-MSC-derived exosome-seeded ECM-based cryogels for cartilage tissue engineering to treat cartilage injury. Full article

Smoking has been associated, among other factors, with musculoskeletal disorders. Although there is no consensus about the effects of smoking on osteoarthritis (OA), the increase in TNF-alpha in smokers has been considered an important factor in OA induction or progression. However, studies on the effects of smoking on chondrocytes are lacking. Here we aimed to study the effects of cigarette smoke extract (CSE) associated with a TNF-alpha inhibitor on cell death of primary human chondrocytes derived from osteoarthritic patients. CSE at 10% led to cell death by apoptosis after 48 h of incubation, together with caspase 3/7 activation, decrease in mitochondrial transmembrane potential, ROS production, and improvement in syndercan-1, perlecan, and RUNX2 gene expression. All these effects promoted by CSE were reversed by TNF-alpha inhibitor. Collagen II, F-actin, and SOX9 were also analyzed, and CSE promoted alteration in the expression of these proteins. In conclusion, our results support the clinical impact of smoking on OA development by showing the detrimental action of CSE on osteoarthritis-derived chondrocytes and the protective effects of TNF-alpha inhibitors, reinforcing the importance of this cytokine in the cartilage injury process. Full article