Osteoarthritis (OA) is a common joint disease in the elderly population. Its development has been reported to be associated with cartilage degradation and inflammatory responses. Schisandrin A, a bioactive lignin in Schisandra sphenanthera, has shown its anti-inflammatory potential in various inflammation diseases. However, the effects of Schisandrin A on OA remain to explore. In this study, rat chondrocytes were treated with IL-1β (10 ng/ml) with or without different concentrations of Schisandrin A for 24 h. Cell viability was evaluated by CCK-8 assay. Production of nitric oxide (NO) and prostaglandin E2 (PGE2) was measured by the Griess reaction and ELISA. The MAPK/NF-κB-related signaling molecules expression and the protein production of inducible nitric oxide synthase (iNOS), cyclooxygenase (Cox)-2, MMPs (MMP1, MMP3, MMP13), ADAMTS5, Collagen II, aggrecan, and Sox9 were detected by Western blot. Protein expression of Collagen II, aggrecan, and p65 nuclear translocation was evaluated by immunofluorescence. In vivo, intra-articular injection of 50 μM Schisandrin A or equal volume of vehicle was performed on rat OA models. Severity of cartilage damage was evaluated by HE and Safranin-O-Fast green staining. Our results revealed that Schisandrin A could suppress the IL-1β-induced production of NO and PGE2 in rat chondrocytes. Consistent with these findings, the upregulation of iNOS and Cox2 could also been decreased by Schisandrin A. Additionally, Schisandrin A could inhibit IL-1β-induced cartilage matrix catabolic enzymes including MMPs and ADAMTS5. Moreover, the IL-1β-induced downregulation of Collagen II, aggrecan, and Sox9 could be ameliorated by Schisandrin A. Mechanistically, Schisandrin A functioned by suppressing MAPK and NF-κB signal pathways. In vivo, Schisandrin A prevented cartilage damage in rat OA model. In conclusion, this study elucidates that Schisandrin A inhibits the IL-1β-induced inflammation and cartilage degradation via suppression of MAPK and NF-κB signal pathways, indicating its potential role in OA therapy.

Osteoarthritis (OA), characterized by chronic systemic low‐level inflammation and cartilage degeneration, is a type of arthritis closely associated with aging. Inflammation and aging play a pivotal role in the occurrence and progression of OA. NLRP3 inflammasome is involved in many inflammatory and aging diseases, and NLRP3 inhibitor MCC950 has anti‐inflammatory and antisenescence effects on some diseases such as Alzheimer’s disease. In the present study, we found that NLRP3 protein was upregulated in human and mouse OA cartilage. Moreover, NLRP3 and Caspase1 expression induced by IL‐1β in chondrocytes was blocked by MCC950. In addition, MCC950 inhibited the expression of inflammatory mediators, matrix‐degrading enzymes, senescence marker protein P16 (INK4A), and β‐galactosidase, as well as excessive production of ROS. Meanwhile, MCC950 promoted autophagy‐related protein expression and autophagy flux under the inflammatory condition. However, autophagy inhibitor 3‐MA reversed anti‐inflammatory and anticatabolic effects of MCC950. In in vivo experiments, intra‐articular administration of MCC950 further showed its protective effect on cartilage degeneration. Bioinformatic analysis and in vitro experimental results revealed that MCC950 might play a protective role in cartilage by regulating Nrf2/HO‐1/NQO1, PI3k/Akt/mTOR, P38/MAPK, and JNK/MAPK pathways. In conclusion, our work demonstrated that NLRP3 inhibitor MCC950 might serve as a promising strategy for OA treatment.

Osteoarthritis (OA) has become the most common degenerative disease in the world, which brings a serious economic burden to society and the country. Although epidemiological studies have shown that the occurrence of osteoarthritis is associated with obesity, sex, and trauma, the biomolecular mechanisms for the development and progression of osteoarthritis remain ambiguous. Several studies have drawn a connection between SPP1 and osteoarthritis. SPP1 was first found to be highly expressed in osteoarthritic cartilage, and later more studies have shown that SPP1 is also highly expressed in subchondral bone and synovial in OA patients. However, the biological function of SPP1 remains unclear. Single-cell RNA sequencing (scRNA-seq) is a novel technique that reflects gene expression at the cellular level, making it better depict the state of different cells than ordinary transcriptome data. However, most of the existing chondrocyte scRNA-seq studies focus on the occurrence and development of OA chondrocytes and lack analysis of normal chondrocyte development. Therefore, to better understand the mechanism of OA, scRNA-seq analysis of a larger cell volume containing normal and osteoarthritic cartilage is of great importance. Our study identifies a unique cluster of chondrocytes characterized by high SPP1 expression. The metabolic and biological characteristics of these clusters were further investigated. Besides, in animal models, we found that the expression of SPP1 is spatially heterogeneous in cartilage. Overall, our work provides novel insight into the potential role of SPP1 in OA, which sheds light on understanding the role of SPP1 in OA, promoting the progress of the treatment and prevention in the field of OA.

Osteoarthritis (OA), an age‐related degenerative joint disease, is pathologically characterized by articular cartilage degeneration and synovial inflammation. Nephroblastoma overexpressed (NOV or CCN3), a matricellular protein, is a primary member of the CCN family (Cyr61, Ctgf, NOV) of proteins and is involved in various inflammatory disorders. Previous studies reported that CCN3 might play a therapeutic role in OA. However, the underlying mechanism remains unclear. In this study, we confirmed the expression of CCN3 was decreased in human and rat OA articular cartilage. Recombinant CCN3 ameliorated the IL‐1β‐induced matrix catabolism, as demonstrated by MMP1, MMP3, MMP13, ADAMTS5 and iNOS expression, in vitro. In addition, the degradation of cartilage matrix such as collagen 2 and aggrecan could be reversed by CCN3. Furthermore, we found CCN3 promoted autophagy as Atg5, Beclin1 and LC3‐II expression were increased. High‐mobility group box 1 was negatively correlated with CCN3 in IL‐1β‐induced osteoarthritis responses, and HMGB1 is involved in the protective effect of CCN3 in OA. Moreover, CCN3 overexpression decreased the expression of HMGB1 and reversed the IL‐1β induced MMPs production. Additionally, recombinant CCN3 or CCN3 overexpression attenuated the activation of PI3K/AKT/mTOR pathway induced by IL‐1β. Our study presents new mechanisms of CCN3 in osteoarthritis and indicates that CCN3 can serve as a novel potential therapeutic target for osteoarthritis.