miR-483 targets SMAD4 to suppress chondrogenic differentiation of human mesenchymal stem cells

MicroRNAs (miRNAs) can regulate cellular differentiation processes by modulating multiple pathways simultaneously. Previous studies to analyze in vivo miRNA expression patterns in developing human limb cartilage tissue identified significant downregulation of miR-483 in hypertrophic chondrocytes relative to proliferating and differentiated chondrocytes. To test the function of miR-483 during chondrogenesis, lentiviral strategies were used to overexpress miR-483 during in vitro chondrogenesis of human bone marrow-derived mesenchymal stem cells (hBM-MSCs). While the in vivo expression patterns led us to hypothesize that miR-483 may enhance chondrogenesis or suppress hypertrophic marker expression, surprisingly, miR-483 overexpression reduced chondrocyte gene expression and cartilage matrix production. In addition, cell death was induced at later stages of the chondrogenesis assay. Mechanistic studies revealed that miR-483 overexpression resulted in downregulation of the TGF-β pathway member SMAD4, a known direct target of miR-483-3p. From these studies, we conclude that constitutive overexpression of miR-483 in hBM-MSCs inhibits chondrogenesis of these cells and does not represent an effective strategy to attempt to enhance chondrocyte differentiation and anabolism in this system in vitro.