MicroRNA-16-5p Controls Development of Osteoarthritis by Targeting SMAD3 in Chondrocytes

MicroRNAs (miRNA), small noncoding RNA molecules, are endogenous regulators of gene expression that have been implicated in the pathogenesis of various diseases such as cancer and arthritis. The aim of this study was to explore the biological function of microRNA-16-5p (miR-16-5p) and the molecular mechanism in osteoarthritis (OA). MiRNA targets were identified using bioinformatics. Using real-time PCR, the expression of miR-16-5p and SMAD3 in cartilage specimens was determined in 10 patients with knee OA and in 10 traumatic amputees (control). Functional analysis of miR-16-5p in chondrocytes was performed at both mRNA and protein levels after miRNA transfection. A luciferase reporter assay was used to verify interaction between miRNA and target mRNA. Expression of miR-16-5p was significantly higher in OA cartilages than in healthy cartilages. The data from the reporter assay and western blots indicated that miR-16- 5p regulated SMAD3 expression. Functional analysis showed that miR-16-5p could reduce expression of type IIcollagen and aggrecan while inducing expression of matrix metalloproteinases and ADAMTS; however, miR-16-5p inhibition could reverse these effects. Our results indicate that miR-16-5p is an important regulator of SMAD3 expression in human chondrocytes and may contribute to the development of OA.