Direct protective effect of interleukin-10 on articular chondrocytes in vitro

OBJECTIVE: To assess whether interleukin-10 (IL-10) is chondroprotective in vitro. METHODS: Chondrocytes were isolated from femoral cartilage of rats (7-10 days) by digestion with collagenase II. The first passage cells were grown in 24- well plates with DMEM, supplemented with 10% fetal bovine serum, for 2-4 days. The cells were then cultured in 0.1% fetal bovine serum DMEM medium, and given respectively interleukin-1 (IL-1) 100 mu/ml, IL-1 100 mu/ml + recombinant murine interleukin-10 (rmIL-10) 20 ng/ml, rmIL-10 20 ng/ml, and cultured for 48 hours. Scanning electron morphology and immunohistochemical study of nitric oxide synthase 2 and matric metalloproteinase 3 mRNA in situ hybridization were performed. Cell proliferation and morphology were observed under inverted microscope from the beginning of cell culture for three weeks. RESULTS: IL-1 stimulated granule production in the cytoplasma of chondrocytes, and the cells died in the second and third weeks of culture. IL-10 antagonized IL-1, protected the cells from death and maintained chondrocyte proliferation. Scanning electron morphology showed that IL-1 stimulated the formation of numerous microvilli on the cell surface, while thin and less numerous microvilli were found in cultures with IL-10. Immunohistochemical study and in situ hybridization showed that IL-10 inhibited NOS2 and MMP3 expression. CONCLUSION: IL-10 not only inhibits the synthesis of inflammatory cytokines, but also directly protects chondrocytes by antagonizing IL-1.