Expression of microRNA-27a in a rat model of osteonecrosis of the femoral head and its association with TGF-/Smad7 signalling in osteoblasts

The present study assessed whether microRNA (miR)-27a is an influential factor in steroid-induced osteonecrosis of the femoral head (ONFH) and investigated the underlying mechanism of action. The results indicated that serum miR-27a was decreased in a rat model of ONFH compared with that in control rats. It was also observed that increased miR-27a expression promoted osteogenic differentiation and cell proliferation, inhibited caspase-3/9 and B-cell lymphoma-2-associated X protein expression and induced alkaline phosphatase (ALP) activity and bone morphogenetic protein (BMP)-2, runt-related transcription factor (Runx)2 and osteonectin mRNA expression in osteoblastic MC3T3-E1 cells. miR-27a mimics also induced transforming growth factor (TGF)- and Smad7 protein expression in MC3T3-E1 cells. Furthermore, transfection with TGF- expression plasmid was able to enhance the effects of miR-27a mimics on osteoblastic differentiation, cell proliferation, ALP activity, BMP-2, Runx2 and osteonectin mRNA expression, and Smad7 protein expression in the MC3T3-E1 cells. Transfection with a TGF- or Smad7 expression plasmid also enhanced the effects of miR-27a mimics on osteoblastic differentiation, cell proliferation, ALP activity and osteonectin mRNA expression in the MC3T3-E1 cells. Taken together, the results of the present study suggested that the induction of TGF-/Smad7 signaling in osteoblasts may be a potential mechanism by which miR-27a regulates steroid-induced ONFH.