Osteoarthritis (OA) is the most common joint disease. Recently, a novel variant near the nuclear receptor coactivator 3 (NCOA3) has been identified in association with greater risk of developing OA. However, how NCOA3 is regulated in chondrocytes and involved in OA pathogenesis remain elusive.
The expression and DNA methylation of NCOA3 in knee OA cartilage and in vitro dedifferentiated chondrocytes with or without rs6094710 SNP were analyzed by qRT-PCR, immunoblotting, methylation-specific PCR and bisulfite sequencing. NCOA3 was depleted by siRNA or shRNA or inhibited by a chemical inhibitor to assess its role in chondrocyte dedifferentiation or OA pathogenesis in posttraumatic OA animal model established by cruciate ligament transection surgery.
We found that compared with normal counterparts, samples with rs6094710 SNP failed to upregulate NCOA3. Further evidence associated this phenotype with DNMT1-mediated hypermethylation in gene promoter region. Moreover, we showed that NCOA3 maintained the molecular signature of chondrocytes dedifferentiating in vitro or exposed to IL-1β, nevertheless, NCOA3 appeared dispensable for preventing OA initiation, since NCOA3 loss did not trigger OA in young mice. Instead, NCOA3 loss promoted posttraumatic OA progression, and in parallel, enhanced NF-κB activation. Finally, the promoted posttraumatic OA progression was significantly retarded when administrated with NF-κB pathway inhibitor, suggesting that NCOA3 lose promotes posttraumatic OA at least partially by enhancing NF-κB activation.
Thus, our findings indicate a critical role of NCOA3 in chondrocytes, and imply that manipulating NCOA3 might present a potential therapeutic approach to interfere OA progression.