Single-cell RNA sequencing reveals different chondrocyte states in femoral cartilage between osteoarthritis and healthy individuals.

Background: Cartilage injury is the main pathological manifestation of osteoarthritis (OA). Healthy chondrocyte is a prerequisite for cartilage regeneration and repair. Differences between healthy and OA chondrocyte types and the role these types play in cartilage regeneration and OA progression are unclear. Method: This study conducted single-cell RNA sequencing (scRNA-seq) on the cartilage from normal distal femur of the knee (NC group) and OA femur (OA group) cartilage, the chondrocyte atlas was constructed, and the differences of cell subtypes between the two groups were compared. Pseudo-time and RNA velocity analysis were both performed to verify the possible differentiation sequence of cell subtypes. GO and KEGG pathway enrichment analysis were used to explore the potential functional characteristics of each cell subtype, and to predict the functional changes during cell differentiation. Differences in transcriptional regulation in subtypes were explored by single-cell regulatory network inference and clustering (SCENIC). The distribution of each cell subtype in cartilage tissue was identified by immunohistochemical staining (IHC). Result: A total of 75,104 cells were included, they were divided into 19 clusters and annotated as 11 chondrocyte subtypes, including two new chondrocyte subtypes: METRNL+ and PRG4+ subtype. METRNL+ is in an early stage during chondrocyte differentiation, and RegC-B is in an intermediate state before chondrocyte dedifferentiation. With cell differentiation, cell subtypes shift from genetic expression to extracellular matrix adhesion and collagen remodeling, and signal pathways shift from HIF-1 to Hippo. The 11 subtypes were finally classified as intrinsic chondrocytes, effector chondrocytes, abnormally differentiated chondrocytes and dedifferentiated chondrocytes. IHC was used to verify the presence and distribution of each chondrocyte subtype. Conclusion: This study screened two new chondrocyte subtypes, and a novel classification of each subtype was proposed. METRNL+ subtype is in an early stage during chondrocyte differentiation, and its transcriptomic characteristics and specific pathways provide a foundation for cartilage regeneration. EC-B, PRG4+ RegC-B, and FC are typical subtypes in the OA group, and the HippO-Taz pathway enriched by these cell subtypes may play a role in cartilage repair and OA progression. RegC-B is in the intermediate state before chondrocyte dedifferentiation, and its transcriptomic characteristics may provide a theoretical basis for intervening chondrocyte dedifferentiation.

Loss of ß-arrestin2 aggravated condylar cartilage degeneration at the early stage of temporomandibular joint osteoarthritis.

OBJECTIVE: Temporomandibular joint osteoarthritis (TMJOA) is a chronic degenerative joint disorder characterized by extracellular matrix degeneration and inflammatory response of condylar cartilage. ß-arrestin2 is an important regulator of inflammation response, while its role in TMJOA remains unknown. The objective of this study was to investigate the role of ß-arrestin2 in the development of TMJOA at the early stage and the underlying mechanism. METHODS: A unilateral anterior crossbite (UAC) model was established on eight-week-old wild-type (WT) and ß-arrestin2 deficiency mice to simulate the progression of TMJOA. Hematoxylin-eosin (HE) staining and microcomputed tomography (micro-CT) analysis were used for histological and radiographic assessment. Immunohistochemistry was performed to detect the expression of inflammatory and degradative cytokines, as well as autophagy related factors. Terminal-deoxynucleotidyl transferase mediated nick end labeling (TUNEL) assay was carried out to assess chondrocyte apoptosis. RESULTS: The loss of ß-arrestin2 aggravated cartilage degeneration and subchondral bone destruction in the model of TMJOA at the early stage. Furthermore, in UAC groups, the expressions of degradative (Col-X) and inflammatory (TNF-α and IL-1ß) factors in condylar cartilage were increased in ß-arrestin2 null mice compared with WT mice. Moreover, the loss of ß-arrestin2 promoted apoptosis and autophagic process of chondrocytes at the early stage of TMJOA. CONCLUSION: In conclusion, we demonstrated for the first time that ß-arrestin2 plays a protective role in the development of TMJOA at the early stage, probably by inhibiting apoptosis and autophagic process of chondrocytes. Therefore, ß-arrestin2 might be a potential therapeutic target for TMJOA, providing a new insight for the treatment of TMJOA at the early stage.

Exosomes derived from miR-146a-overexpressing fibroblast-like synoviocytes in cartilage degradation and macrophage M1 polarization: a novel protective agent for osteoarthritis?

Introduction: Pathological changes in the articular cartilage (AC) and synovium are major manifestations of osteoarthritis (OA) and are strongly associated with pain and functional limitations. Exosome-derived microRNAs (miRNAs) are crucial regulatory factors in intercellular communication and can influence the progression of OA by participating in the degradation of chondrocytes and the phenotypic transformation in the polarization of synovial macrophages. However, the specific relationships and pathways of action of exosomal miRNAs in the pathological progression of OA in both cartilage and synovium remain unclear. Methods: This study evaluates the effects of fibroblast-like synoviocyte (FLS)-derived exosomes (FLS-Exos), influenced by miR-146a, on AC degradation and synovial macrophage polarization. We investigated the targeted relationship between miR-146a and TRAF6, both in vivo and in vitro, along with the involvement of the NF-κB signaling pathway. Results: The expression of miR-146a in the synovial exosomes of OA rats was significantly higher than in healthy rats. In vitro, the upregulation of miR-146a reduced chondrocyte apoptosis, whereas its downregulation had the opposite effect. In vivo, exosomes derived from miR-146a-overexpressing FLSs (miR-146a-FLS-Exos) reduced AC injury and chondrocyte apoptosis in OA. Furthermore, synovial proliferation was reduced, and the polarization of synovial macrophages shifted from M1 to M2. Mechanistically, the expression of TRAF6 was inhibited by targeting miR-146a, thereby modulating the Toll-like receptor 4/TRAF6/NF-κB pathway in the innate immune response. Discussion: These findings suggest that miR-146a, mediated through FLS-Exos, may alleviate OA progression by modulating cartilage degradation and macrophage polarization, implicating the NF-κB pathway in the innate immune response. These insights highlight the therapeutic potential of miR-146a as a protective agent in OA, underscoring the importance of exosomal miRNAs in the pathogenesis and potential treatment of the disease.

Exercise following joint distraction inhibits muscle wasting and delays the progression of post-traumatic osteoarthritis in rabbits by activating PGC-1α in skeletal muscle.

OBJECTIVE: Muscle wasting frequently occurs following joint trauma. Previous research has demonstrated that joint distraction in combination with treadmill exercise (TRE) can mitigate intra-articular inflammation and cartilage damage, consequently delaying the advancement of post-traumatic osteoarthritis (PTOA). However, the precise mechanism underlying this phenomenon remains unclear. Hence, the purpose of this study was to examine whether the mechanism by which TRE following joint distraction delays the progression of PTOA involves the activation of peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), as well as its impact on muscle wasting. METHODS: Quadriceps samples were collected from patients with osteoarthritis (OA) and normal patients with distal femoral fractures, and the expression of PGC-1α was measured. The hinged external fixator was implanted in the rabbit PTOA model. One week after surgery, a PGC-1α agonist or inhibitor was administered for 4 weeks prior to TRE. Western blot analysis was performed to detect the expression of PGC-1α and Muscle atrophy gene 1 (Atrogin-1). We employed the enzyme-linked immunosorbent assay (ELISA) technique to examine pro-inflammatory factors. Additionally, we utilized quantitative real-time polymerase chain reaction (qRT-PCR) to analyze genes associated with cartilage regeneration. Synovial inflammation and cartilage damage were evaluated through hematoxylin-eosin staining. Furthermore, we employed Masson's trichrome staining and Alcian blue staining to analyze cartilage damage. RESULTS: The decreased expression of PGC-1α in skeletal muscle in patients with OA is correlated with the severity of OA. In the rabbit PTOA model, TRE following joint distraction inhibited the expressions of muscle wasting genes, including Atrogin-1 and muscle ring finger 1 (MuRF1), as well as inflammatory factors such as interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) in skeletal muscle, potentially through the activation of PGC-1α. Concurrently, the production of IL-1ß, IL-6, TNF-α, nitric oxide (NO), and malondialdehyde (MDA) in the synovial fluid was down-regulated, while the expression of type II collagen (Col2a1), Aggrecan (AGN), SRY-box 9 (SOX9) in the cartilage, and superoxide dismutase (SOD) in the synovial fluid was up-regulated. Additionally, histological staining results demonstrated that TRE after joint distraction reduced cartilage degeneration, leading to a significant decrease in OARSI scores.TRE following joint distraction could activate PGC-1α, inhibit Atrogin-1 expression in skeletal muscle, and reduce C-telopeptides of type II collagen (CTX-II) in the blood compared to joint distraction alone. CONCLUSION: Following joint distraction, TRE might promote the activation of PGC-1α in skeletal muscle during PTOA progression to exert anti-inflammatory effects in skeletal muscle and joint cavity, thereby inhibiting muscle wasting and promoting cartilage regeneration, making it a potential therapeutic intervention for treating PTOA.

Excessive load promotes temporomandibular joint chondrocyte apoptosis via Piezo1/endoplasmic reticulum stress pathway.

Excessive load on the temporomandibular joint (TMJ) is a significant factor in the development of TMJ osteoarthritis, contributing to cartilage degeneration. The specific mechanism through which excessive load induces TMJ osteoarthritis is not fully understood; however, mechanically-activated (MA) ion channels play a crucial role. Among these channels, Piezo1 has been identified as a mediator of chondrocyte catabolic responses and is markedly increased in osteoarthritis. Our observations indicate that, under excessive load conditions, endoplasmic reticulum stress in chondrocytes results in apoptosis of the TMJ chondrocytes. Importantly, using the Piezo1 inhibitor GsMTx4 demonstrates its potential to alleviate this condition. Furthermore, Piezo1 mediates endoplasmic reticulum stress in chondrocytes by inducing calcium ion influx. Our research substantiates the role of Piezo1 as a pivotal ion channel in mediating chondrocyte overload. It elucidates the link between excessive load, cell apoptosis, and calcium ion influx through Piezo1. The findings underscore Piezo1 as a key player in the pathogenesis of TMJ osteoarthritis, shedding light on potential therapeutic interventions for this condition.

MST1 knockdown inhibits osteoarthritis progression through Parkin-mediated mitophagy and Nrf2/NF-κB signalling pathway.

Osteoarthritis (OA) is a complicated disease that involves apoptosis and mitophagy. MST1 is a pro-apoptotic factor. Hence, decreasing its expression plays an anti-apoptotic effect. This study aims to investigate the protective effect of MST1 inhibition on OA and the underlying processes. Immunofluorescence (IF) was used to detect MST1 expression in cartilage tissue. Western Blot, ELISA and IF were used to analyse the expression of inflammation, extracellular matrix (ECM) degradation, apoptosis and mitophagy-associated proteins. MST1 expression in chondrocytes was inhibited using siRNA and shRNA in vitro and in vivo. Haematoxylin-Eosin, Safranin O-Fast Green and alcian blue staining were used to evaluate the therapeutic effect of inhibiting MST1. This study discovered that the expression of MST1 was higher in OA patients. Inhibition of MST1 reduced inflammation, ECM degradation and apoptosis and enhanced mitophagy in vitro. MST1 inhibition slows OA progression in vivo. Inhibiting MST1 suppressed apoptosis, inflammation and ECM degradation via promoting Parkin-mediated mitophagy and the Nrf2-NF-κB axis. The results suggest that MST1 is a possible therapeutic target for the treatment of osteoarthritis as its inhibition delays the progression of OA through the Nrf2-NF-κB axis and mitophagy.

TAK-242 (Resatorvid) inhibits proinflammatory cytokine production through the inhibition of NF-κB signaling pathway in fibroblast-like synoviocytes in osteoarthritis patients.

BACKGROUND: Fibroblast-like synoviocytes (FLSs) are involved in osteoarthritis (OA) pathogenesis through pro-inflammatory cytokine production. TAK-242, a TLR4 blocker, has been found to have a significant impact on the gene expression profile of pro-inflammatory cytokines such as IL1-ß, IL-6, TNF-α, and TLR4, as well as the phosphorylation of Ikßα, a regulator of the NF-κB signaling pathway, in OA-FLSs. This study aims to investigate this effect because TLR4 plays a crucial role in inflammatory responses. MATERIALS AND METHODS: Ten OA patients' synovial tissues were acquired, and isolated FLSs were cultured in DMEM in order to assess the effectiveness of TAK-242. The treated FLSs with TAK-242 and Lipopolysaccharides (LPS) were analyzed for the mRNA expression level of IL1-ß, IL-6, TNF-α, and TLR4 levels by Real-Time PCR. Besides, we used western blot to assess the protein levels of Ikßα and pIkßα. RESULTS: The results represented that TAK-242 effectively suppressed the gene expression of inflammatory cytokines IL1-ß, IL-6, TNF-α, and TLR4 which were overexpressed upon LPS treatment. Additionally, TAK-242 inhibited the phosphorylation of Ikßα which was increased by LPS treatment. CONCLUSION: According to our results, TAK-242 shows promising inhibitory effects on TLR4-mediated inflammatory responses in OA-FLSs by targeting the NF-κB pathway. TLR4 inhibitors, such as TAK-242, may be useful therapeutic agents to reduce inflammation and its associated complications in OA patients, since traditional and biological treatments may not be adequate for all of them.

Development of primary osteoarthritis during aging in genetically diverse UM-HET3 mice.

BACKGROUND: Primary osteoarthritis (OA) occurs without identifiable underlying causes such as previous injuries or specific medical conditions. Age is a major contributing factor to OA, and as one ages, various joint tissues undergo gradual change, including degeneration of the articular cartilage, alterations in subchondral bone (SCB) morphology, and inflammation of the synovium. METHODS: We investigated the prevalence of primary OA in aged, genetically diverse UM-HET3 mice. Articular cartilage (AC) integrity and SCB morphology were assessed in 182 knee joints of 22-25 months old mice using the Osteoarthritis Research Society International (OARSI) scoring system and micro-CT, respectively. Additionally, we explored the effects of methylene blue (MB) and mitoquinone (MitoQ), two agents that affect mitochondrial function, on the prevalence and progression of OA during aging. RESULTS: Aged UM-HET3 mice showed a high prevalence of primary OA in both sexes. Significant positive correlations were found between cumulative AC (cAC) scores and synovitis in both sexes, and osteophyte formation in female mice. Ectopic chondrogenesis did not show significant correlations with cAC scores. Significant direct correlations were found between AC scores and inflammatory markers in chondrocytes, including matrix metalloproteinase-13, inducible nitric oxide synthase, and the NLR family pyrin domain containing-3 inflammasome in both sexes, indicating a link between OA severity and inflammation. Additionally, markers of cell cycle arrest, such as p16 and ß-galactosidase, also correlated with AC scores. In male mice, no significant correlations were found between SCB morphology traits and cAC scores, while in female mice, significant correlations were found between cAC scores and tibial SCB plate bone mineral density. Notably, MB and MitoQ treatments influenced the disease's progression in a sex-specific manner. MB treatment significantly reduced cAC scores at the medial knee joint, while MitoQ treatment reduced cAC scores, but these did not reach significance. CONCLUSIONS: Our study provides comprehensive insights into the prevalence and progression of primary OA in aged UM-HET3 mice, highlighting the sex-specific effects of MB and MitoQ treatments. The correlations between AC scores and various pathological factors underscore the multifaceted nature of OA and its association with inflammation and subchondral bone changes.

Comprehensive Analysis of Sphingolipid Metabolism-Related Genes in Osteoarthritic Diagnosis and Synovial Immune Dysregulation.

BACKGROUND Osteoarthritis (OA) is a chronic degenerative disease characterized by synovitis and has been implicated in sphingolipid metabolism disorder. However, the role of sphingolipid metabolism pathway (SMP)-related genes in the occurrence of OA and synovial immune dysregulation remains unclear. MATERIAL AND METHODS In this study, we obtained synovium-related databases from GEO (n=40 for both healthy controls and OA) and analyzed the expression levels of SMP-related genes. Using 2 algorithms, we identified hub genes and developed a diagnostic model incorporating these hub genes to predict the occurrence of OA. Subsequently, the hub genes were further validated in peripheral blood samples from OA patients. Additionally, CIBERSORT and MCP-counter analyses were employed to explore the correlation between hub genes and immune dysregulation in OA synovium. WGCNA was used to determine enriched modules in different clusters. RESULTS Overall, the expression levels of SMP genes were upregulated in OA synovium. We identified 6 hub genes of SMP and constructed an excellent diagnostic model (AUC=0.976). The expression of re-confirmed hub genes showed associations with immune-related cell infiltration and levels of inflammatory cytokines. Furthermore, we observed heterogeneity in the expression patterns of hub genes across different clusters of OA. Notably, older patients displayed increased susceptibility to elevated levels of pain-related inflammatory cytokines and infiltration of immune cells. CONCLUSIONS The SMP-related hub genes have the potential to serve as diagnostic markers for OA patients. Moreover, the 4 hub genes of SMP demonstrate wide participation in immune dysregulation in OA synovium. The activation of different pathways is observed among different populations of patients with OA.

Cartilage progenitor cells derived extracellular vesicles-based cell-free strategy for osteoarthritis treatment by efficient inflammation inhibition and extracellular matrix homeostasis restoration.

Osteoarthritis (OA) is a common degenerative joint disease which currently lacks of effective agents. It is therefore urgent and necessary to seek an effective approach that can inhibit inflammation and promote cartilage matrix homeostasis. Cartilage progenitor cells (CPCs) are identified as a cell population of superficial zone in articular cartilage which possess strong migration ability, proliferative capacity, and chondrogenic potential. Recently, the application of CPCs may represent a novel cell therapy strategy for OA treatment. There is growing evidence that extracellular vesicles (EVs) are primary mediators of the benefits of stem cell-based therapy. In this study, we explored the protective effects of CPCs-derived EVs (CPCs-EVs) on IL-1ß-induced chondrocytes. We found CPCs-EVs exhibited chondro-protective effects in vitro. Furthermore, our study demonstrated that CPCs-EVs promoted matrix anabolism and inhibited inflammatory response at least partially via blocking STAT3 activation. In addition, liquid chromatography-tandem mass spectrometry analysis identified 991 proteins encapsulated in CPCs-EVs. By bioinformatics analysis, we showed that STAT3 regulatory proteins were enriched in CPCs-EVs and could be transported to chondrocytes. To promoting the protective function of CPCs-EVs in vivo, CPCs-EVs were modified with cationic peptide ε-polylysine-polyethylene-distearyl phosphatidylethanolamine (PPD) for surface charge reverse. In posttraumatic OA mice, our results showed PPD modified CPCs-EVs (PPD-EVs) effectively inhibited extracellular matrix catabolism and attenuated cartilage degeneration. Moreover, PPD-EVs down-regulated inflammatory factors expressions and reduced OA-related pain in OA mice. In ex-vivo cultured OA cartilage explants, PPD-EVs successfully promoted matrix anabolism and inhibited inflammation. Collectively, CPCs-EVs-based cell-free therapy is a promising strategy for OA treatment.

Activation of kappa opioid receptor suppresses post-traumatic osteoarthritis via sequestering STAT3 on the plasma membrane.

OBJECTIVE: Kappa opioid receptor (KOR) signaling is involved in joint development and inflammation in Osteoarthritis (OA), while the biochemical mechanism remains unclarified. This study aims to investigate downstream molecular events of KOR activation, to provide novel perspectives in OA pathology. METHODS: U50,488H, a selective KOR agonist, was intra-articularly injected in mice upon destabilization of the medial meniscus (DMM) as OA models, with PBS injection as control. The behavioral and histological evaluation was assessed by hot plate test and red solid green staining, respectively. Alterations in mRNA and protein expression were assessed by RNA-seq, RT-qPCR, immunohistochemistry and western blotting (WB) in chondrocytes treated with TNF-α or TNF-α + U50,488H. Proteins interacted with KOR were explored using proximity labeling followed by mass spectrometry and then testified by co-immunoprecipitation (Co-IP) assay and immunofluorescence (IF). RESULTS: OA-induced pain was reduced and cartilage degeneration was alleviated upon KOR activation in DMM mice. In chondrocytes, activation of KOR reversed the upregulation of MMPs, IL-6, IL-1ß and phosphorylated(p-) STAT3, stimulated by TNF-α, while the expression of NF-κB, MAPKs and AKT signaling weren't reversed. RNA-seq and IF results presented that KOR activation evidently reduced STAT3 nuclear translocation in chondrocytes upon TNF-α stimuli. The reduction may be resulted from the binding of KOR and STAT3 in the plasma membrane, revealed by proximity labeling and Co-IP results. CONCLUSIONS: KOR activation protects cartilage from OA, and this protective effect is mainly exerted via sequestering STAT3 on the plasma membrane, resulting in inactivation of STAT3-dependent immune responses which otherwise contributes to OA.

Mitochondrial Role on Cellular Apoptosis, Autophagy, and Senescence during Osteoarthritis Pathogenesis.

Authors have demonstrated that apoptosis activation is a pathway related to cartilage degradation characteristics of the OA process. Autophagy is an adaptive response to protect cells from various environmental changes, and defects in autophagy are linked to cell death. In this sense, decreased autophagy of chondrocytes has been observed in OA articular cartilage. The aim of this work was to study the role of OA mitochondria in apoptosis, autophagy, and senescence, using OA and Normal (N) transmitochondrial cybrids. Results: OA cybrids incubated with menadione showed a higher percentage of late apoptosis and necrosis than N cybrids. Stimulation of cybrids with staurosporine and IL-1ß showed that OA cybrids were more susceptible to undergoing apoptosis than N cybrids. An analysis of the antioxidant response using menadione on gene expression revealed a lower expression of nuclear factor erythroid 2-like 2 and superoxide dismutase 2 in OA than N cybrids. Activation of microtubule-associated protein 1A/1B-light chain 3 was reduced in OA compared to N cybrids. However, the percentage of senescent cells was higher in OA than N cybrids. Conclusion: This work suggests that mitochondria from OA patients could be involved in the apoptosis, autophagy, and senescence of chondrocytes described in OA cartilage.

Induction of Human Wharton's Jelly of Umbilical Cord Derived Mesenchymal Stem Cells to Be Chondrocytes and Transplantation in Guinea Pig Model with Spontaneous Osteoarthritis.

Osteoarthritis (OA) is a degenerative joint disease commonly found in elderly people and obese patients. Currently, OA treatments are determined based on their condition severity and a medical professional's advice. The aim of this study was to differentiate human Wharton's jelly-derived mesenchymal stem cells (hWJ-MSCs) into chondrocytes for transplantation in OA-suffering guinea pigs. hWJ-MSCs were isolated using the explant culture method, and then, their proliferation, phenotypes, and differentiation ability were evaluated. Subsequently, hWJ-MSCs-derived chondrocytes were induced and characterized based on immunofluorescent staining, qPCR, and immunoblotting techniques. Then, early-OA-suffering guinea pigs were injected with hyaluronic acid (HA) containing either MSCs or 14-day-old hWJ-MSCs-derived chondrocytes. Results showed that hWJ-MSCs-derived chondrocytes expressed specific markers of chondrocytes including Aggrecan, type II collagen, and type X collagen proteins and ß-catenin, Sox9, Runx2, Col2a1, Col10a1, and ACAN gene expression markers. Administration of HA plus hWJ-MSCs-derived chondrocytes (HA-CHON) produced a better recovery rate of degenerative cartilages than HA plus MSCs or only HA. Histological assessments demonstrated no significant difference in Mankin's scores of recovered cartilages between HA-CHON-treated guinea pigs and normal articular cartilage guinea pigs. Transplantation of hWJ-MSCs-derived chondrocytes was more effective than undifferentiated hWJ-MSCs or hyaluronic acid for OA treatment in guinea pigs. This study provides a promising treatment to be used in early OA patients to promote recovery and prevent disease progression to severe osteoarthritis.

Therapeutic Potential of Ginsenosides on Bone Metabolism: A Review of Osteoporosis, Periodontal Disease and Osteoarthritis.

Ginsenosides, bioactive compounds from the genus Panax, have potential therapeutic effects on diverse ailments, including diabetes. Emerging evidence suggests their involvement in bone metabolism. The present review summarizes the current understanding of the effects of ginsenosides on osteoporosis, periodontal disease, and osteoarthritis. Their mechanisms of action include effects on osteoblasts, osteoclasts, periodontal ligament fibroblasts (PDLFs), and chondrocytes, which are pivotal in maintaining bone, periodontal tissue, and cartilage homeostasis. Ginsenosides may exert their beneficial effects by enhancing PDLF and osteoblast activity, suppressing osteoclast function, augmenting chondrocyte synthesis in the cartilage matrix, and mitigating connective tissue degradation. Moreover, they possess antioxidant, anti-inflammatory, antimicrobial, and anti-pyroptotic properties. Their efficacy in increasing bone density, ameliorating periodontitis, and alleviating osteoarthritis symptoms has been demonstrated in preclinical studies using animal models. In terms of their mechanism of action, ginsenosides modulate cellular differentiation, activity, and key signaling pathway molecules, such as mitogen-activated protein kinases (MAPKs), while also regulating various mediators. Furthermore, the symptomatic relief observed in animal models lends further credence to their therapeutic utility. However, to translate these preclinical findings into clinical practice, rigorous animal and clinical investigations are imperative to ascertain the safety, efficacy, and optimal dosing regimens in human subjects.

A Narrative Review of the Roles of Chondromodulin-I (Cnmd) in Adult Cartilage Tissue.

Articular cartilage is crucial for joint function but its avascularity limits intrinsic repair, leading to conditions like osteoarthritis (OA). Chondromodulin-I (Cnmd) has emerged as a key molecule in cartilage biology, with potential implications for OA therapy. Cnmd is primarily expressed in cartilage and plays an important role in chondrocyte proliferation, cartilage homeostasis, and the blocking of angiogenesis. In vivo and in vitro studies on Cnmd, also suggest an involvement in bone repair and in delaying OA progression. Its downregulation correlates with OA severity, indicating its potential as a therapeutic target. Further research is needed to fully understand the mode of action of Cnmd and its beneficial implications for managing OA. This comprehensive review aims to elucidate the molecular characteristics of Cnmd, from its expression pattern, role in cartilage maintenance, callus formation during bone repair and association with OA.

Potential Roles of Inflammation on Post-Traumatic Osteoarthritis of the Ankle.

Post-traumatic osteoarthritis of the ankle (PTOA) is frequently observed following a debilitating consequence of intra-articular ankle fractures. Numerous risk factors contribute to the pathogenesis of PTOA, including articular incongruity, joint malalignment, and concomitant soft tissue damage. Despite attempts to restore joint anatomy and manage soft tissues to avoid long-term complications after intra-articular ankle fractures, the incidence of PTOA remains markedly elevated. Inflammatory processes triggered by intra-articular ankle fractures have emerged as potential instigators that expedite the progression of PTOA. Injury to the articular cartilage and subchondral bone may lead to the release of inflammatory mediators, which can contribute to cartilage degradation and bone resorption. This study provides a narrative review on the current knowledge concerning the association between inflammation and the development of PTOA following intra-articular ankle fractures. We also discuss novel therapeutic agents that target inflammatory pathways to impede the progression of post-traumatic osteoarthritis after intra-articular ankle fractures. These medication and interventions were summarized within this review article.

α-Ketoglutarate alleviates osteoarthritis by inhibiting ferroptosis via the ETV4/SLC7A11/GPX4 signaling pathway.

Osteoarthritis (OA) is the most common degenerative joint disorder that causes disability in aged individuals, caused by functional and structural alterations of the knee joint. To investigate whether metabolic drivers might be harnessed to promote cartilage repair, a liquid chromatography-mass spectrometry (LC-MS) untargeted metabolomics approach was carried out to screen serum biomarkers in osteoarthritic rats. Based on the correlation analyses, α-ketoglutarate (α-KG) has been demonstrated to have antioxidant and anti-inflammatory properties in various diseases. These properties make α-KG a prime candidate for further investigation of OA. Experimental results indicate that α-KG significantly inhibited H2O2-induced cartilage cell matrix degradation and apoptosis, reduced levels of reactive oxygen species (ROS) and malondialdehyde (MDA), increased superoxide dismutase (SOD) and glutathione (GSH)/glutathione disulfide (GSSG) levels, and upregulated the expression of ETV4, SLC7A11 and GPX4. Further mechanistic studies observed that α-KG, like Ferrostatin-1 (Fer-1), effectively alleviated Erastin-induced apoptosis and ECM degradation. α-KG and Fer-1 upregulated ETV4, SLC7A11, and GPX4 at the mRNA and protein levels, decreased ferrous ion (Fe2+) accumulation, and preserved mitochondrial membrane potential (MMP) in ATDC5 cells. In vivo, α-KG treatment inhibited ferroptosis in OA rats by activating the ETV4/SLC7A11/GPX4 pathway. Thus, these findings indicate that α-KG inhibits ferroptosis via the ETV4/SLC7A11/GPX4 signaling pathway, thereby alleviating OA. These observations suggest that α-KG exhibits potential therapeutic properties for the treatment and prevention of OA, thereby having potential clinical applications in the future.

HDAC4 represses ER stress induced chondrocyte apoptosis by inhibiting ATF4 and attenuates cartilage degeneration in an osteoarthritis rat model.

BACKGROUND: The present study evaluated whether the lack of histone deacetylase 4 (HDAC4) increases endoplasmic reticulum stress-induced chondrocyte apoptosis by releasing activating transcription factor 4 (ATF4) in human osteoarthritis (OA) cartilage degeneration. METHODS: Articular cartilage from the tibial plateau was obtained from patients with OA during total knee replacement. Cartilage extracted from severely damaged regions was classified as degraded cartilage, and cartilage extracted from a relatively smooth region was classified as preserved cartilage. Terminal deoxynucleotidyl transferase dUTP nick end labeling staining was used to detect chondrocyte apoptosis. HDAC4, ATF4, and C/EBP homologous protein (CHOP) expression levels were measured using immunohistochemistry staining and real-time quantitative PCR. Chondrocytes were transfected with HDAC4 or HDAC4 siRNA for 24 h and stimulated with 300 µM H2O2 for 12 h. The chondrocyte apoptosis was measured using flow cytometry. ATF4, CHOP, and caspase 12 expression levels were measured using real-time quantitative PCR and western blotting. Male Sprague-Dawley rats (n = 15) were randomly divided into three groups and transduced with different vectors: ACLT + Ad-GFP, ACLT + Ad-HDAC4-GFP, and sham + Ad-GFP. All rats received intra-articular injections 48 h after the operation and every three weeks thereafter. Cartilage damage was assessed using Safranin O staining and quantified using the Osteoarthritis Research Society International score. ATF4, CHOP, and collagen II expression were detected using immunohistochemistry, and chondrocyte apoptosis was detected using terminal deoxynucleotidyl transferase dUTP nick end labeling staining. RESULTS: The chondrocyte apoptosis was higher in degraded cartilage than in preserved cartilage. HDAC4 expression was lower in degraded cartilage than in preserved cartilage. ATF4 and CHOP expression was increased in degraded cartilage. Upregulation of HDAC4 in chondrocytes decreased the expression of ATF4, while the expression of ATF4 was increased after downregulation of HDAC4. Upregulation of HDAC4 decreased the chondrocyte apoptosis under endoplasmic reticulum stress, and chondrocyte apoptosis was increased after downregulation of HDAC4. In a rat anterior cruciate ligament transection OA model, adenovirus-mediated transduction of HDAC4 was administered by intra-articular injection. We detected a stronger Safranin O staining with lower Osteoarthritis Research Society International scores, lower ATF4 and CHOP production, stronger collagen II expression, and lower chondrocyte apoptosis in rats treated with Ad-HDAC4. CONCLUSION: The lack of HDAC4 expression partially contributes to increased ATF4, CHOP, and endoplasmic reticulum stress-induced chondrocyte apoptosis in OA pathogenesis. HDAC4 attenuates cartilage damage by repressing ATF4-CHOP signaling-induced chondrocyte apoptosis in a rat model of OA.

Inhibition of CC chemokine receptor 1 ameliorates osteoarthritis in mouse by activating PPAR-γ.

BACKGROUND: Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage destruction and inflammation. CC chemokine receptor 1 (CCR1), a member of the chemokine family and its receptor family, plays a role in the autoimmune response. The impact of BX471, a specific small molecule inhibitor of CCR1, on CCR1 expression in cartilage and its effects on OA remain underexplored. METHODS: This study used immunohistochemistry (IHC) to assess CCR1 expression in IL-1ß-induced mouse chondrocytes and a medial meniscus mouse model of destabilization of the medial meniscus (DMM). Chondrocytes treated with varying concentrations of BX471 for 24 h were subjected to IL-1ß (10 ng/ml) treatment. The levels of the aging-related genes P16INK4a and P21CIP1 were analyzed via western blotting, and senescence-associated ß-galactosidase (SA-ß-gal) activity was measured. The expression levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), aggrecan (AGG), and the transcription factor SOX9 were determined through western blotting and RT‒qPCR. Collagen II, matrix metalloproteinase 13 (MMP13), and peroxisome proliferator-activated receptor (PPAR)-γ expression was analyzed via western blot, RT‒qPCR, and immunofluorescence. The impact of BX471 on inflammatory metabolism-related proteins under PPAR-γ inhibition conditions (using GW-9662) was examined through western blotting. The expression of MAPK signaling pathway-related molecules was assessed through western blotting. In vivo, various concentrations of BX471 or an equivalent medium were injected into DMM model joints. Cartilage destruction was evaluated through Safranin O/Fast green and hematoxylin-eosin (H&E) staining. RESULTS: This study revealed that inhibiting CCR1 mitigates IL-1ß-induced aging, downregulates the expression of iNOS, COX-2, and MMP13, and alleviates the IL-1ß-induced decrease in anabolic indices. Mechanistically, the MAPK signaling pathway and PPAR-γ may be involved in inhibiting the protective effect of CCR1 on chondrocytes. In vivo, BX471 protected cartilage in a DMM model. CONCLUSION: This study demonstrated the expression of CCR1 in chondrocytes. Inhibiting CCR1 reduced the inflammatory response, alleviated cartilage aging, and retarded degeneration through the MAPK signaling pathway and PPAR-γ, suggesting its potential therapeutic value for OA.

Vitamin B6 alleviates osteoarthritis by suppressing inflammation and apoptosis.

BACKGROUND: Although various anti-inflammatory medicines are widely recommended for osteoarthritis (OA) treatment, no significantly clinical effect has been observed. This study aims to examine the effects of vitamin B6, a component that has been reported to be capable of alleviating inflammation and cell death in various diseases, on cartilage degeneration in OA. METHODS: Collagen-induced arthritis (CIA) mice model were established and the severity of OA in cartilage was determined using the Osteoarthritis Research Society International (OARSI) scoring system. The mRNA and protein levels of indicators associated with extracellular matrix (ECM) metabolism, apoptosis and inflammation were detected. The effect of vitamin B6 (VB6) on the mice were assessed using HE staining and masson staining. The apoptosis rate of cells was assessed using TdT-mediated dUTP nick end labeling. RESULTS: Our results showed a trend of improved OARSI score in mice treated with VB6, which remarkably inhibited the hyaline cartilage thickness, chondrocyte disordering, and knees hypertrophy. Moreover, the VB6 supplementation reduced the protein expression of pro-apoptosis indicators, including Bax and cleaved caspase-3 and raised the expression level of anti-apoptosis marker Bcl-2. Importantly, VB6 improved ECM metabolism in both in vivo and in vitro experiments. CONCLUSIONS: This study demonstrated that VB6 alleviates OA through regulating ECM metabolism, inflammation and apoptosis in chondrocytes and CIA mice. The findings in this study provide a theoretical basis for targeted therapy of OA, and further lay the theoretical foundation for studies of mechanisms of VB6 in treating OA.