Molecular mechanism study of 1, 25(OH)₂D₃ alleviating osteoarthritis by up-regulating IL-10 receptor and inhibiting chondrocyte apoptosis

Objective: To investigate the protective effect and molecular mechanism of calcitriol 1, 25(OH)₂D₃on knee articular cartilage in rats with post-traumatic osteoarthritis (PTOA).Methods: The PTOA rat model was established.Twenty SD rats were randomly divided into control group, sham operation group, PTOA group and 1, 25(OH)₂D₃ group, with 5 rats in each group.Immunohistochemistry (IHC) was used to detect the expression of IL-10 receptor(IL-10R)and matrix metalloproteinase-13 (MMP-13)in knee articular cartilage.Safranin O stain-ing method was used to determine the degree of knee articular cartilage injury.Rat bone marrow stem cells(BM-SCs) were isolated and divided into undifferentiation group, differentiation group, 1, 25(OH)₂D₃ intervention group and 1, 25(OH)₂D₃+IL-10R antibody group.The expression of MMP-13 and collagen 10a1 (Col10a1)mRNA in cells were detected by real-time fluorescence quantitative PCR (RT-qPCR).Western blotting was used to detect the expression of phospho (p)-JAK, JAK, transforming growth factor-β1 (TGF-β1), SOX9, Smad2 and Runx2 and the apoptosis rate was detected by TUNEL assay.Results: IHC staining results showed that compared with the control group, the expression level of IL-10R decreased and the expression level of MMP-13 increased in the PTOA group (both P< 0.05).Compared with the PTOA group, the expression level of IL-10R increased and the expression level MMP-13 decreased in the 1, 25(OH)₂D₃ group (both P< 0.05).Safranin O staining results showed that the thickness of cartilage layer in the PTOA group was lower than that in the control group (P< 0.05), and the thickness of cartilage layer in the 1, 25(OH)₂D₃ group was higher than that in the PTOA group (both P< 0.05).Compared with the differentiation group, the relative expression level of MMP-13 mRNA in the 1, 25(OH)₂D₃ intervention group decreased, and the relative expression level of Col10a1 mRNA and the pro-tein expression levels of p-JAK, TGF-β1, SOX9, Smad2 and Runx2 increased (all P< 0.05).The rate of TUNEL positive cells decreased(P< 0.05).Compared with the 1, 25(OH)₂D₃ intervention group, 1, 25(OH)₂D₃+IL-10R an-tibody group cells partially reversed the above indicators (P< 0.05).Conclusion: The 1, 25(OH)₂D₃ may play a protective role in knee articular cartilage of rats with PTOA by up-regulating the expression of IL-10R in knee ar-ticular cartilage and inhibiting chondrocyte apoptosis.