SPARCL1 promotes chondrocytes extracellular matrix degradation and inflammation in osteoarthritis via TNF/NF-κB pathway.

Objectives: SPARCL1 is a matricellular protein that mediates the cell-matrix interactions and participates in physiological processes such as cell adhesion, differentiation and proliferation. However, its role in chondrocyte and osteoarthritis (OA) progression has not been fully characterized. We aimed to evaluate the effects of SPARCL1 on OA through in vitro and Methods: Expression of SPARCL1 was examined in 55 paired human OA samples. Effects of Sparcl1 on chondrocytes were identified in vitro. Intra-articular injection was performed in an anterior cruciate ligament transection (ACLT) mouse model. Alterations of SPARCL1-mediated signaling pathway were identified by RNA-seq analysis. qPCR and western-blot were used to demonstrate the potential signaling pathway. Results: SPARCL1 expression in the OA cartilage was increased compared with undamaged cartilage. Recombinant Sparcl1 protein induced extracellular matrix degradation in chondrocytes. Furthermore, intra-articular injection of recombinant Sparcl1 protein in ACLT mice could promote OA pathogenesis. Mechanistically, Sparcl1 activated TNF/NF-κB pathway and consequently led to increased transcription of inflammatory factors and catabolism genes of cartilage, which could be reversed by NF-κB inhibitor BAY 11-7082. Conclusion: SPARCL1 could promote extracellular matrix degradation and inflammatory response to accelerate OA progression via TNF/NF-κB pathway. The translational potential of this article: The current research could help to gain further insights into the underlying molecular mechanism in OA development, and provides a biological rationale for the use of SPARCL1 as a potential therapeutic target of OA.