Method: Primary rat articular chondrocytes (rArCs) were isolated from adult Sprague-Dawley rat femurs. An osteoarthritic phenotype was induced in confluent cultures with 1, 5, and 10ng/ml IL-1β for 24h. To investigate effects of 24R,25(OH)2D3 and TGF-β1 on osteoarthritis markers prostaglandin E2 (PGE2) and matrix metalloproteinase-13 (MMP-13), rArCs were treated with 10-8M 24R,25(OH)2D3 ± 0.1ng/ml TGF-β1 for the last 12h in addition to the IL-1β treatment. mRNA levels for Smad2, Smad3, and receptor TGFbrII were measured by real-time RT-PCR. Production of PGE2, MMP-13, and active and latent TGF-β1 were measured using ELISA.
Result: IL-1β caused a dose-dependent increase in production of PGE2 and MMP-13, which was partially inhibited by 24R,25(OH)2D3, similar to the effect of TGF-β1. IL-1β down-regulated mRNA levels for Smad2 and TGFbrII while up-regulating Smad3 and increased both active and latent TGF-β1 protein levels. 10-8M 24R,25(OH)2D3 increased Smad 2, Smad3, TGFbrII mRNAs, and the protein production of active TGF-β1. 24R,25(OH)2D3 and TGF-β1 treatment resulted in a synergistic reduction of MMP-13.
Conclusion: Our data indicate that 24R,25(OH)2D3 can inhibit chondrocyte matrix degradation stimulated by IL-1β and its effect is partially mediated through the TGF-β1 signaling pathway. This suggests that 24R,25(OH)2D3 may be used as a local therapeutic factor in the treatment of osteoarthritis.