Effects of miR-145 on the inhibition of chondrocyte proliferation and fibrosis by targeting TNFRSF11B in human osteoarthritis

Osteoarthritis (OA) is a common cause of functional deterioration in older adults, and altered chondrogenesis is the most common pathophysiological process involved in the development of OA. MicroRNA-145 (miR-145) has been shown to regulate chondrocyte homeostasis. However, the function of miR-145 in OA remains to be elucidated. In the present study, the expression levels of miR-145 were examined in cartilage specimens from 25 patients with knee OA using reverse transcription-quantitative polymerase chain reaction analysis. The effects of miR-145 on the proliferation and fibrosis of the C-20/A4 and CH8 cell lines were also investigated using 3-(4,5-dimethylth-iazol-2-y1)-2,5-diphenyltetrazolium bromide and western blot assays in vitro. The results revealed that the expression of miR-145 was decreased in the OA cartilage tissues, compared with normal cartilage tissues. The overexpression of miR-145 by transfection of cells with miR-145 mimics significantly inhibited C-20/A4 and CH8 cell proliferation and fibrosis. Furthermore, tumor necrosis factor receptor superfamily, member lib (TNFRSF11B) was identified as a direct target of miR-145 in chondrocytes, which was confirmed using a dual-luciferase reporter assay. The expression level of TNFRSF11B was markedly upregulated in the patients with OA, and the ectopic expression of miR-145 was capable of suppressing the expression of TNFRSF11B. In addition, the knock down of TNFRSF11B using specific small interfering RNA also inhibited the proliferation and fibrosis of C-20/A4 and CH8 cells in vitro. These data provide the first evidence, to the best of our knowledge, to suggest the critical function of miR-145 in regulating the expression of TNFRSF11B, which may have important implications on the regulation of chondrocyte proliferation and fibrosis in OA.