Potential Therapeutic Target For Osteoarthritis Research Articles

Identification of ion channel-related genes as diagnostic markers and potential therapeutic targets for osteoarthritis through bioinformatics and machine learning-based approaches

Background Osteoarthritis (OA) is a debilitating joint disorder characterized by the progressive degeneration of articular cartilage. Although the role of ion channels in OA pathogenesis is increasingly recognized, diagnostic markers and targeted therapies remain limited. Methods In this study, we analyzed the GSE48556 dataset to identify differentially expressed ion channel-related genes (DEGs) in OA and normal controls. We employed machine learning algorithms, least absolute shrinkage and selection operator(LASSO), and support vector machine recursive feature elimination(SVM-RFE) to select potential diagnostic markers. Then the gene set enrichment analysis (GSEA) and gene set variation analysis (GSVA) were performed to explore the potential diagnostic markers’ involvement in biological pathways. Finally, weighted gene co-expression network analysis (WGCNA) was used to identify key genes associated with OA. Results We identified a total of 47 DEGs, with the majority involved in transient receptor potential (TRP) pathways. Seven genes (CHRNA4, GABRE, HTR3B, KCNG2, KCNJ2, LRRC8C, and TRPM5) were identified as the best characteristic genes for distinguishing OA from healthy samples. We performed clustering analysis and identified two distinct subtypes of OA, C1, and C2, with differential gene expression and immune cell infiltration profiles. Then we identified three key genes (PPP1R3D, ZNF101, and LOC651309) associated with OA. We constructed a prediction model using these genes and validated it using the GSE46750 dataset, demonstrating reasonable accuracy and specificity. Conclusions Our findings provide novel insights into the role of ion channel-related genes in OA pathogenesis and offer potential diagnostic markers and therapeutic targets for the treatment of OA.

TfR1 mediated iron metabolism dysfunction as a potential therapeutic target for osteoarthritis.

Transferrin receptor-1 (TfR1) plays important roles in controlling cellular iron levels, but its role in OA pathology is unknown. Herein we aim to investigate the role of TfR1 in OA progression and its underlying mechanisms. TfR1 expression in cartilage during OA development were examined both in vivo and in vitro. Then IL-1β was used to induce chondrocytes degeneration in vitro and TfR1 siRNA was used for observing the effect of TfR1 in modulating iron homeostasis, mitochondrial function and degrading enzymes expression. Also the inhibitor of TfR1 was exploited to analyze the protective effect of TfR1 inhibition in vivo. TfR1 is elevated in OA cartilage and contributes to OA inflammation condition. Excess iron not only results in oxidative stress damage and sensitizes chondrocytes to ferroptosis, but also triggers c-GAS/STING-mediated inflammation by promoting mitochondrial destruction and the release of mtDNA. Silencing TfR1 using TfR1 siRNA not only reduced iron content in chondrocytes and inhibited oxidative stress, but also facilitated the mitophagy process and suppressed mtDNA/cGAS/STING-mediated inflammation. Importantly, we also found that Ferstatin II, a novel and selective TfR1 inhibitor, could substantially suppress TfR1 activity both in vivo and in vitro and ameliorated cartilage degeneration. Our work demonstrates that TfR1 mediated iron influx plays important roles in chondrocytes degeneration and OA pathogenesis, suggesting that maintaining iron homeostasis through the targeting of TfR1 may represent a novel therapeutic strategy for the treatment of OA.

Exploring m6A-linked aging genes in osteoarthritis and broad cancer spectrum: Prospects for diagnostic and therapeutic advancements.

Osteoarthritis (OA) is a prevalent degenerative joint disease that significantly impacts individuals and healthcare systems worldwide. However, the exploration of N6-methyladenosine (m6A)-related aging genes in OA pathogenesis remains largely underexplored. This study aimed to elucidate the role of m6A-related aging genes in OA and to develop a robust diagnostic model based on their expression profiles. Leveraging publicly available gene expression datasets, we conducted consensus clustering to categorize OA into distinct subtypes, guided by the expression patterns of m6A-related aging genes. Utilizing XGBoost, a cutting-edge machine learning approach, we identified key diagnostic genes and constructed a predictive model. Our investigation extended to the immune functions of these genes, shedding light on potential therapeutic targets and underlying regulatory mechanisms. Our analysis unveiled specific OA subtypes, each marked by unique expression profiles of m6A-related aging genes. We pinpointed a set of pivotal diagnostic genes, offering potential therapeutic avenues. The developed diagnostic model exhibited exceptional capability in distinguishing OA patients from healthy controls. To corroborate our computational findings, we performed quantitative real-time polymerase chain reaction analyses on two cell lines: HC-OA (representing adult osteoarthritis cells) and C-28/I2 (representative of normal human chondrocytes). The gene expression patterns observed were consistent with our bioinformatics predictions, further validating our initial results. In conclusion, this study underscores the significance of m6A-related aging genes as promising biomarkers for diagnosis and prognosis, as well as potential therapeutic targets in OA. Although these findings are encouraging, further validation and functional analyses are crucial for their clinical application.

Downregulation of Gadd45β alleviates osteoarthritis by repressing lipopolysaccharide-induced fibroblast-like synoviocyte inflammation, proliferation and migration

ObjectiveGadd45β have a regulatory role in cellular inflammation, proliferation and migration. However, the role of Gadd45β in synovial inflammation in osteoarthritis (OA) remains to be explored. This study aimed to ascertain whether Gadd45β is involved in OA synovial inflammation. MethodsThe rat model was induced by sodium iodoacetate and the cellular model was constructed with lipopolysaccharide (LPS)-induced fibroblast-like synoviocytes (FLSs). siRNA was applied to interfere with the expression of intracellular Gadd45β. Real-time quantitative polymerase chain reaction (RT-qPCR) and western blotting were used to detect the expression of Gadd45β mRNA and protein. The inflammation, proliferation, and migration of OA-FLSs were detected by enzyme-linked immunosorbent assay, cell scratch assay, 5-ethynyl-2′-deoxyuridine assay, etc. The effect of downregulation of Gadd45β on the nuclear factor-κB (NF-κB) pathway was investigated. ResultsExpression of Gadd45β in OA rat synovial tissues and OA-FLSs was increased, and LPS treatment promoted cell proliferation and enhanced cell migration. Gadd45β interference inhibited the inflammation, proliferation and migration of cells induced by LPS. LPS promoted P65 expression in the nucleus and activated the NF-κB signaling pathway, whereas si-Gadd45β reversed this situation. Conclusionssi-Gadd45β inhibited the inflammatory response, proliferation and migration of FLSs, and activation of the NF-κB signaling pathway, which could delay the progression of OA. Hence, it may become a potential therapeutic target for OA.

Nuclear protein-1 is the common link for pathways activated by aging and obesity in chondrocytes: A potential therapeutic target for osteoarthritis.

Pathways leading to osteoarthritis (OA) are diverse depending on the risk factors involved; thus, developing OA therapeutics has been challenging. Here we report that nuclear protein-1 (Nupr1), a stress-inducible protein/transcription factor, is activated by pathways associated with obesity and aging in chondrocytes. Treatment of human chondrocytes with free fatty acids (palmitate and oleate; a model for high-fat diet/obesity) induced PERK signaling and increased expression of caspase-3, TRB3, and Nupr1. On the other hand, treatment of chondrocytes with menadione (oxidative stress inducer) induced oxidation of IRE1, activated antioxidant response (higher Nrf2 expression), and increased expression of Nupr1 and matrix metalloproteinases. Experimental OA was induced by destabilization of the medial meniscus (DMM) in the knee joints of Nupr1+/+ and Nupr1-/- mice. Loss of Nupr1 expression reduced the severity of cartilage lesions in this model. Together, our findings suggest that Nupr1 is a common factor activated by signaling pathways activated by obesity (ER stress) and age (oxidative stress) and a potential drug target for OA resulting from various risk factors.

Suramin analogues protect cartilage against osteoarthritic breakdown by increasing levels of tissue inhibitor of metalloproteinases 3 (TIMP-3) in the tissue

Osteoarthritis is a chronic degenerative joint disease affecting millions of people worldwide, with no disease-modifying drugs currently available to treat the disease. Tissue inhibitor of metalloproteinases 3 (TIMP-3) is a potential therapeutic target in osteoarthritis because of its ability to inhibit the catabolic metalloproteinases that drive joint damage by degrading the cartilage extracellular matrix. We previously found that suramin inhibits cartilage degradation through its ability to block endocytosis and intracellular degradation of TIMP-3 by low-density lipoprotein receptor-related protein 1 (LRP1), and analysis of commercially available suramin analogues indicated the importance of the 1,3,5-trisulfonic acid substitutions on the terminal naphthalene rings for this activity. Here we describe synthesis and structure–activity relationship analysis of additional suramin analogues using ex vivo models of TIMP-3 trafficking and cartilage degradation. This showed that 1,3,6-trisulfonic acid substitution of the terminal naphthalene rings was also effective, and that the protective activity of suramin analogues depended on the presence of a rigid phenyl-containing central region, with para/para substitution of these phenyl rings being most favourable. Truncated analogues lost protective activity. The physicochemical characteristics of suramin and its analogues indicate that approaches such as intra-articular injection would be required to develop them for therapeutic use.

Identification of aging-related biomarkers and immune infiltration characteristics in osteoarthritis based on bioinformatics analysis and machine learning.

Osteoarthritis (OA) is a degenerative disease closely related to aging. Nevertheless, the role and mechanisms of aging in osteoarthritis remain unclear. This study aims to identify potential aging-related biomarkers in OA and to explore the role and mechanisms of aging-related genes and the immune microenvironment in OA synovial tissue. Normal and OA synovial gene expression profile microarrays were obtained from the Gene Expression Omnibus (GEO) database and aging-related genes (ARGs) from the Human Aging Genomic Resources database (HAGR). Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG), Disease Ontology (DO), and Gene set variation analysis (GSVA) enrichment analysis were used to uncover the underlying mechanisms. To identify Hub ARDEGs with highly correlated OA features (Hub OA-ARDEGs), Weighted Gene Co-expression Network Analysis (WGCNA) and machine learning methods were used. Furthermore, we created diagnostic nomograms and receiver operating characteristic curves (ROC) to assess Hub OA-ARDEGs' ability to diagnose OA and predict which miRNAs and TFs they might act on. The Single sample gene set enrichment analysis (ssGSEA) algorithm was applied to look at the immune infiltration characteristics of OA and their relationship with Hub OA-ARDEGs. We discovered 87 ARDEGs in normal and OA synovium samples. According to functional enrichment, ARDEGs are primarily associated with inflammatory regulation, cellular stress response, cell cycle regulation, and transcriptional regulation. Hub OA-ARDEGs with excellent OA diagnostic ability were identified as MCL1, SIK1, JUND, NFKBIA, and JUN. Wilcox test showed that Hub OA-ARDEGs were all significantly downregulated in OA and were validated in the validation set and by qRT-PCR. Using the ssGSEA algorithm, we discovered that 15 types of immune cell infiltration and six types of immune cell activation were significantly increased in OA synovial samples and well correlated with Hub OA-ARDEGs. Synovial aging may promote the progression of OA by inducing immune inflammation. MCL1, SIK1, JUND, NFKBIA, and JUN can be used as novel diagnostic biomolecular markers and potential therapeutic targets for OA.

MicroRNA-224-5p nanoparticles balance homeostasis via inhibiting cartilage degeneration and synovial inflammation for synergistic alleviation of osteoarthritis

MicroRNAs play a crucial role in regulating cartilage extracellular matrix (ECM) metabolism and are being explored as potential therapeutic targets for osteoarthritis (OA). The present study indicated that microRNA-224-5p (miR-224-5p) could balance the homeostasis of OA via regulating cartilage degradation and synovium inflammatory simultaneously. Multifunctional polyamidoamine dendrimer with amino acids used as efficient vector to deliver miR-224-5p. The vector could condense miR-224-5p into transfected nanoparticles, which showed higher cellular uptake and transfection efficiency compared to lipofectamine 3000, and also protected miR-224-5p from RNase degradation. After treatment with the nanoparticles, the chondrocytes showed an increase in autophagy rate and ECM anabolic components, as evidenced by the upregulation of autophagy-related proteins and OA-related anabolic mediators. This led to a corresponding inhibition of cell apoptosis and ECM catabolic proteases, ultimately resulting in the alleviation of ECM degradation. In addition, miR-224-5p also inhibited human umbilical vein endothelial cells angiogenesis and fibroblast-like synoviocytes inflammatory hyperplasia. Integrating the above synergistic effects of miR-224-5p in regulating homeostasis, intra-articular injection of nanoparticles performed outstanding therapeutic effect by reducing articular space width narrowing, osteophyte formation, subchondral bone sclerosis and inhibiting synovial hypertrophy and proliferation in the established mouse OA model. The present study provides a new therapy target and an efficient intra-articular delivery method for improving OA therapy. Statement of significanceOsteoarthritis (OA) is the most prevalent joint disease worldwide. Gene therapy, which involves delivering microRNAs, has the potential to treat OA. In this study, we demonstrated that miR-224-5p can simultaneously regulate cartilage degradation and synovium inflammation, thereby restoring homeostasis in OA gene therapy. Moreover, compared to traditional transfection reagents such as lipofectamine 3000, G5-AHP showed better efficacy in both microRNA transfection and protection against degradation due to its specific surface structure. In summary, G5-AHP/miR-224-5p was developed to meet the clinical needs of OA patients and the high requirement of gene transfection efficiency, providing a promising paradigm for the future application and development of gene therapy.

Decreased Peli1 expression attenuates osteoarthritis by protecting chondrocytes and inhibiting M1-polarization of macrophages.

Pellino1 (Peli1) has been reported to regulate various inflammatory diseases. This study aims to explore the role of Peli1 in the occurrence and development of osteoarthritis (OA), so as to find new targets for the treatment of OA. After inhibiting Peli1 expression in chondrocytes with small interfering RNA (siRNA), interleukin (IL)-1β was used to simulate inflammation, and OA-related indicators such as synthesis, decomposition, inflammation, and apoptosis were detected. Toll-like receptor (TLR) and nuclear factor-kappa B (NF-κB) signalling pathway were detected. After inhibiting the expression of Peli1 in macrophages Raw 264.7 with siRNA and intervening with lipopolysaccharide (LPS), the polarization index of macrophages was detected, and the supernatant of macrophage medium was extracted as conditioned medium to act on chondrocytes and detect the apoptosis index. The OA model of mice was established by destabilized medial meniscus (DMM) surgery, and adenovirus was injected into the knee cavity to reduce the expression of Peli1. The degree of cartilage destruction and synovitis were evaluated by haematoxylin and eosin (H&E) staining, Safranin O/Fast Green staining, and immunohistochemistry. In chondrocytes, knockdown of Peli1 produced anti-inflammatory and anti-apoptotic effects by targeting the TLR and NF-κB signalling pathways. We found that in macrophages, knockdown of Peli1 can inhibit M1-type polarization of macrophages. In addition, the corresponding conditioned culture medium of macrophages applied to chondrocytes can also produce an anti-apoptotic effect. During in vivo experiments, the results have also shown that knockdown Peli1 reduces cartilage destruction and synovial inflammation. Knockdown of Peli1 has a therapeutic effect on OA, which therefore makes it a potential therapeutic target for OA.Cite this article: Bone Joint Res2023;12(2):121-132.

Circ_0001721 knockdown relieves IL-1β-induced chondrocyte injury via regulating miR-373-3p/CXCR4 in osteoarthritis.

Circular RNA (circRNA) plays an important role in osteoarthritis (OA) progression. Circ_0001721 has been noted to be significantly overexpressed in OA patients, but its function in OA progression remain unclear. The purpose of this study was to investigate the role and mechanism of circ_0001721 in OA progression. Interleukin-1β (IL-1β)-induced chondrocytes were used to mimic OA cell model in vitro. The expression of circ_0001721, microRNA (miR)-373-3p and CXC chemokine receptor 4 (CXCR4) was examined by quantitative real-time PCR. The concentrations of inflammatory factors were assessed by ELISA assay. Cell proliferation and apoptosis were determined by MTT assay, EdU assay and flow cytometry. Protein levels were detected by western blot analysis. The interaction between miR-373-3p and circ_0001721 or CXCR4 was confirmed by dual-luciferase reporter assay, RIP assay and RNA pull-down assay. Our results showed that circ_0001721 was highly expressed in OA patients and IL-1β-induced chondrocytes. IL-1β treatment could suppress the proliferation, while promote the apoptosis, extracellular matrix (ECM) degradation and inflammation of chondrocytes. Knockdown of circ_0001721 alleviated IL-1β-induced chondrocyte injury. MiR-373-3p could be sponged by circ_0001721, and its inhibitor reversed the regulation of circ_0001721 knockdown on IL-1β-induced chondrocyte injury. CXCR4 was a target of miR-373-3p, and circ_0001721 could sponge miR-373-3p to regulate CXCR4. Furthermore, miR-373-3p overexpression inhibited IL-1β-induced chondrocyte injury, and these effects could be overturned by CXCR4 upregulation. Our data confirmed that circ_0001721 knockdown alleviated IL-1β-induced chondrocyte injury by miR-373-3p/CXCR4 axis, which suggested that circ_0001721 might be a potential therapeutic target for OA.

Mechanism of immune infiltration in synovial tissue of osteoarthritis: a gene expression-based study

BackgroundOsteoarthritis is a chronic degenerative joint disease, and increasing evidences suggest that the pathogenic mechanism involves immune system and inflammation.AimsThe aim of current study was to uncover hub genes linked to immune infiltration in osteoarthritis synovial tissue using comprehensive bioinformatics analysis and experimental confirmation.MethodsMultiple microarray datasets (GSE55457, GSE55235, GSE12021 and GSE1919) for osteoarthritis in Gene Expression Omnibus database were downloaded for analysis. Differentially expressed genes (DEGs) were identified using Limma package in R software, and immune infiltration was evaluated by CIBERSORT algorithm. Then weighted gene co-expression network analysis (WGCNA) was performed to uncover immune infiltration-associated gene modules. Protein–protein interaction (PPI) network was constructed to select the hub genes, and the tissue distribution of these genes was analyzed using BioGPS database. Finally, the expression pattern of these genes was confirmed by RT-qPCR using clinical samples.ResultsTotally 181 DEGs between osteoarthritis and normal control were screened. Macrophages, mast cells, memory CD4 T cells and B cells accounted for the majority of immune cell composition in synovial tissue. Osteoarthritis synovial showed high abundance of infiltrating resting mast cells, B cells memory and plasma cells. WGCNA screened 93 DEGs related to osteoarthritis immune infiltration. These genes were involved in TNF signaling pathway, IL-17 signaling pathway, response to steroid hormone, glucocorticoid and corticosteroid. Ten hub genes including MYC, JUN, DUSP1, NFKBIA, VEGFA, ATF3, IL-6, PTGS2, IL1B and SOCS3 were selected by using PPI network. Among them, four genes (MYC, JUN, DUSP1 and NFKBIA) specifically expressed in immune system were identified and clinical samples revealed consistent change of these four genes in synovial tissue retrieved from patients with osteoarthritis.ConclusionA 4-gene-based diagnostic model was developed, which had well predictive performance in osteoarthritis. MYC, JUN, DUSP1 and NFKBIA might be biomarkers and potential therapeutic targets in osteoarthritis.

Triclocarban triggers osteoarthritis via DNMT1-mediated epigenetic modification and suppression of COL2A in cartilage tissues

Triclocarban (TCC) is a widely used environmental endocrine-disrupting chemical (EDC). Articular injury of EDCs has been reported; however, whether and how TCCs damage the joint have not yet been determined. Herein, we revealed that exposure to TCC caused osteoarthritis (OA) within the zebrafish anal fin. Mechanistically, TCC stimulates the expression of DNMT1 and initiates DNA hypermethylation of the type II collagen coding gene, which further suppresses the expression of type II collagen and other extracellular matrices. This further results in decreased cartilage tissue and narrowing of the intraarticular space, which is typical of the pathogenesis of OA. The regulation of OA occurrence by TCC is conserved between zebrafish cartilage tissue and human chondrocytes. Our findings clarified the hazard and potential mechanisms of TCC towards articular health and highlighted DNMT1 as a potential therapeutic target for OA caused by TCC.

An update on the use of conventional and biological disease-modifying anti-rheumatic drugs in hand osteoarthritis.

Osteoarthritis (OA) is a highly prevalent condition worldwide associated with pain, progressive disability, reduced participation in social activities, and impaired quality of life. Despite its growing burden, the therapeutic options are still limited and almost exclusively addressed to symptoms' management, while no disease-modifying OA drugs able to prevent or retard disease progression are actually available. For these reasons, in the last decades, relevant efforts to find new potential therapeutic targets in OA have been made and a number of existing conventional and biological disease-modifying anti-rheumatic drugs (DMARDs), including hydroxychloroquine (HCQ), methotrexate (MTX), tumor necrosis factor (TNF)-α, interleukin (IL)-1, and IL-6 inhibitors, commonly used to treat inflammatory rheumatic diseases, have been repurposed for the treatment of OA and explored also in hand osteoarthritis (HOA). The current narrative review was aimed to provide a comprehensive and updated understanding of the possibilities and the criticisms related to the treatment of HOA with conventional and biological DMARDs. Unfortunately, therapy with conventional and biologic drugs in HOA has not achieved the expected success, despite a rationale for their use exists. Thus, our findings outline the urgent need to enhance the exploration of HOA basic molecular mechanisms to find new potential therapeutic targets, personalized for each patient, and appropriate for the different subsets of HOA and for the different phases of disease.

Therapeutic Potential of POU3F3, a Novel Long Non-coding RNA, Alleviates the Pathogenesis of Osteoarthritis by Regulating the miR-29a- 3p/FOXO3 Axis

Osteoarthritis (OA) is the predominant threat to the health of the elderly, and it is crucial to understand the molecular pathogenetic mechanisms involved in it. This study aims to investigate the role of a well-studied cancer-related long non-coding RNA (lncRNA)-POU3F3 in OA and its implicated molecular mechanisms. The expression of POU3F3 and miR-29a-3p was examined in osteoarthritis patients, as well as destabilization of the medial meniscus (DMM) mouse OA model and IL- 1β induced chondrocytes cell OA model, by quantitative real-time PCR. The interaction between POU3F3, miR-29a-3p and transcription factor forkhead box O3 (FOXO3) was verified via dual-luciferase reporter analysis and RNA immunoprecipitation analyses. Cell proliferation and apoptosis were evaluated by cell viability assay and flow cytometry, respectively. Cartilage extracellular matrix (ECM) degradation was investigated with ELISA and western blotting. In addition, the in vivo regulation of POU3F3 in OA was verified by intra-articular injection of lentivirus overexpression POU3F31 in mice models. The expression level of POU3F3 was decreased in OA patients/animal cartilage tissues and IL-1β-stimulated in vitro chondrocyte model. POU3F3 overexpression inhibited IL-1β-induced injury of chondrocytes, enhancing cell viability, suppressing apoptosis and inflammatory cytokine secretion, rescuing metabolic dysfunction, and restraining autophagy in vitro. Mechanistically, Luciferase reporter and RNA immunoprecipitation (RIP) assays indicated that miR-29a-3p could directly bind to POU3F3, and FOXO3 was a target gene of miR-29a-3p. Functional rescue assays confirmed this POU3F3/miR-29a-3p/FOXO3 axis in chondrocytes during OA occurrence. Furthermore, intraarticularly delivery of lentivirus containing POU3F3 alleviates the damage in mouse OA model in vivo. In conclusion, this work highlights the role of the POU3F3/miR-29a-3p/FOXO3 axis in the OA pathogenesis, suggesting this axis as a potential therapeutic target for OA.

The Mechanism and Role of ADAMTS Protein Family in Osteoarthritis

Osteoarthritis (OA) is a principal cause of aches and disability worldwide. It is characterized by the inflammation of the bone leading to degeneration and loss of cartilage function. Factors, including diet, age, and obesity, impact and/or lead to osteoarthritis. In the past few years, OA has received considerable scholarly attention owing to its increasing prevalence, resulting in a cumbersome burden. At present, most of the interventions only relieve short-term symptoms, and some treatments and drugs can aggravate the disease in the long run. There is a pressing need to address the safety problems due to osteoarthritis. A disintegrin-like and metalloprotease domain with thrombospondin type 1 repeats (ADAMTS) metalloproteinase is a kind of secretory zinc endopeptidase, comprising 19 kinds of zinc endopeptidases. ADAMTS has been implicated in several human diseases, including OA. For example, aggrecanases, ADAMTS-4 and ADAMTS-5, participate in the cleavage of aggrecan in the extracellular matrix (ECM); ADAMTS-7 and ADAMTS-12 participate in the fission of Cartilage Oligomeric Matrix Protein (COMP) into COMP lyase, and ADAMTS-2, ADAMTS-3, and ADAMTS-14 promote the formation of collagen fibers. In this article, we principally review the role of ADAMTS metalloproteinases in osteoarthritis. From three different dimensions, we explain how ADAMTS participates in all the following aspects of osteoarthritis: ECM, cartilage degeneration, and synovial inflammation. Thus, ADAMTS may be a potential therapeutic target in osteoarthritis, and this article may render a theoretical basis for the study of new therapeutic methods for osteoarthritis.

Transcriptional regulation of FRZB in chondrocytes by Osterix and Msx2

Osteoarthritis is a common joint disease that causes destruction of articular cartilage and severe inflammation surrounding knee and hip joints. However, to date, effective therapeutic reagents for osteoarthritis have not been developed because the underlying molecular mechanisms are complex. Recent genetic findings suggest that a Wnt antagonist, frizzled-related protein B (FRZB), is a potential therapeutic target for osteoarthritis. Therefore, this study aimed to examine the transcriptional regulation of FRZB in chondrocytes. Frzb/FRZB expression was assessed by RT-qPCR analyses in murine articular chondrocytes and SW1353 chondrocyte cell line. Overexpression and knockdown experiments were performed using adenovirus and lentivirus, respectively. Luciferase-reporter and chromatin immunoprecipitation assays were performed for determining transcriptional regulation. Protein-protein interaction was determined by co-immunoprecipitation analysis. Frzb was highly expressed in cartilages, especially within articular chondrocytes. Interleukin-1α markedly reduced Frzb expression in articular chondrocytes in association with cartilage destruction and increases in ADAM metallopeptidase with thrombospondin type 1 motif (Adamts) 4 and Adamts5 expression. Bone morphogenetic protein 2 (BMP2) increased FRZB expression in SW1353 cells through Smad signaling. Osterix and msh homeobox 2 (Msx2), both of which function as downstream transcription factors of BMP2, induced FRZB expression and upregulated its promoter activity. Co-immunoprecipitation results showed a physical interaction between Osterix and Msx2. Knockdown of either Osterix or Msx2 inhibited BMP2-dependent FRZB expression. Chromatin immunoprecipitation indicated a direct association of Osterix and Msx2 with the FRZB gene promoter. These results suggest that BMP2 regulates FRZB expression through Osterix and Msx2.

CD38 Drives Progress of Osteoarthritis by Affecting Cartilage Homeostasis.

ObjectiveTo observe expression of CD38, a key modulator of nicotinamide dinucleotide (NAD+) metabolism in mice with knee osteoarthritis, and protective effect of CD38 inhibition during the osteoarthritis (OA) development.MethodThe destabilization of the medial meniscus (DMM) model was performed in mice to mimic the process of OA. Immunofluorescence of CD38 was performed to evaluate its response during the OA process. Limb bud‐derived mesenchymal cells were isolated for micromass culture. 100 nM or 1 μM CD38 inhibitor (78c) treatment for 14 days and CD38 sgRNA infection were then used to explore the effects of chondrogenic differentiation via Alcian blue staining. The expressions of chondrogenic markers were detected using RT‐PCR and Western blot. To explore the protective effect of CD38 inhibitor on cartilage degradation during OA in vivo, a CD38 inhibitor was injected into the knee joint after DMM operations. Micro‐CT analysis and Safranin O‐fast green staining were used to evaluate subchondral bone micro‐architecture changes and cartilage degeneration.ResultsCompared to the control group, the CD38 expression in superficial cartilage was obviously increased in DMM group (P < 0.05). During the normal chondrogenic differentiation, the extracellular matrix formed and expression of Sox9, Col2, aggrecan increased apparently while CD38 expression decreased, which could be reversed with ablation of CD38 in limb bud‐derived mesenchymal cells. Consistent with findings in vitro, CD38 blockage via CD38 inhibitor injection protected against osteosclerosis in medial subchondral bone and cartilage degeneration in DMM‐induced experimental mice. Compared to the Sham group, DMM mice showed significantly increased values of BV and BV/TV in subchondral bone (P < 0.05) and Mankin score, which could be rescued by 78c treatment (P < 0.05). Also the CD38 inhibitor contributed to homeostasis of anabolism and catabolism by upregulating Sox9, Col2, aggrecan and downregulating Runx2, Col10 and Mmp13.ConclusionThis study primarily implicates CD38 as an important regulator of chondrogenic differentiation. Inhibition of CD38 demonstrated protection against cartilage degeneration, which suggests that CD38 could be a potential therapeutic target for OA.

HUMAN SPECIFIC DUPLICATE CHRFAM7A GENE IS ASSOCIATED WITH MORE SEVERE OSTEOARTHRITIS AND MODULATES GENERAL BASELINE FOR PAIN BEHAVIORS

Purpose: Alpha 7 acetylcholine nicotinic receptor (α7nAChR) (composed of 5 α7 subunits encoded by Chrna7 gene) activation by endogenous (Ach) or exogenous ligand (nicotine) attenuates inflammation, including in osteoarthritis (OA). Therefore, enhancing α7nAChR signaling might be a potential therapeutic target for OA. However, during evolution a human specific partial duplicate of chrna7 called CHRFAM7A has emerged, and it is expressed in 75% of the population. It functions as a dominant negative of α7nAChR and may decrease α7nAChR signaling and agonist efficiency in OA.

Kindlin-2 preserves integrity of the articular cartilage to protect against osteoarthritis.

Osteoarthritis (OA) is an aging-related degenerative joint disease with a poorly defined mechanism. Here we report that kindlin-2 is highly expressed in articular chondrocytes and downregulated in the degenerated cartilage of aged mice and patients with OA. Kindlin-2 deletion in articular chondrocytes leads to spontaneous OA and exacerbates instability-induced OA lesions in adult mice. Kindlin-2 deficiency promotes mitochondrial oxidative stress and activates Stat3, leading to Runx2-mediated chondrocyte catabolism. Pharmacological inhibition of Stat3 activation or genetic ablation of Stat3 in chondrocytes reverses aberrant accumulation of Runx2 and extracellular-matrix-degrading enzymes and limits OA deteriorations caused by kindlin-2 deficiency. Deleting Runx2 in chondrocytes reverses structural changes and OA lesions caused by kindlin-2 deletion without downregulating p-Stat3. Intra-articular injection of AAV5-kindlin-2 decelerates progression of aging- and instability-induced knee joint OA in mice. Collectively, we identify a pathway consisting of kindlin-2, Stat3 and Runx2 in articular chondrocytes that is responsible for maintaining articular cartilage integrity and define a potential therapeutic target for OA.

TLR4 downregulation by the RNA-binding protein PUM1 alleviates cellular aging and osteoarthritis.

Dysfunction of mRNA or RNA-binding proteins (RBPs) causes cellular aging and age-related degenerative diseases; however, information regarding the mechanism through which RBP-mediated posttranscriptional regulation affects cellular aging and related disease processes is limited. In this study, PUM1 was found to be associated with the self-renewal capacity and aging process of human mesenchymal stem cells (MSC). PUM1 interacted with the 3'-untranslated region of Toll-like receptor 4 (TLR4) to suppress TLR4 mRNA translation and regulate the activity of nuclear factor-κB (NF-κB), a master regulator of the aging process in MSCs. PUM1 overexpression protected MSCs against H2O2-induced cellular senescence by suppressing TLR4-mediated NF-κB activity. TLR4-mediated NF-κB activation is a key regulator in osteoarthritis (OA) pathogenesis. PUM1 overexpression enhanced the chondrogenic potential of MSCs even under the influence of inflammation-inducing factors, such as lipopolysaccharide (LPS) or interleukin-1β (IL-1β), whereas the chondrogenic potential was reduced following the PUM1 knockdown-mediated TLR4 activation. PUM1 levels decreased under inflammatory conditions in vitro and during OA progression in human and mouse disease models. PUM1 knockdown in human chondrocytes promoted chondrogenic phenotype loss, whereas PUM1 overexpression protected the cells from inflammation-mediated disruption of the chondrogenic phenotype. Gene therapy using a lentiviral vector encoding mouse PUM1 showed promise in preserving articular cartilage integrity in OA mouse models. In conclusion, PUM1 is a novel suppressor of MSC aging, and the PUM1-TLR4 regulatory axis represents a potential therapeutic target for OA.