Downregulation of Annexin A1 by short hairpin RNA inhibits the osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells.

Annexin A1 (ANX A1) is essential in cell differentiation and proliferation. However, the role of ANX A1 in bone marrow-derived mesenchymal stem cell (BM-MSC) osteogenic differentiation and proliferation remains unclear. To investigate whether endogenous ANX A1 influences BM-MSC proliferation and osteogenic differentiation, a stable ANX A1-knockdown cell line was generated using short hairpin RNA (shRNA). The proliferation rate of BM-MSCs was analyzed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide proliferation assay. Additionally, BM-MSCs were differentiated into osteoblasts and subsequently used to isolate total proteins to analyze the expression of ANX A1. Cell differentiation was assayed using Alizarin red S staining. The results revealed that the knockdown of ANX A1 in BM-MSCs exerts no apparent effect on the proliferation rate under normal conditions, however, following exposure to an osteogenic medium, downregulation of ANX A1 protected cells from the effect of osteogenic medium-induced inhibition of cell proliferation. Silencing ANX A1 with shRNA significantly inhibited the phosphorylation of extracellular signal-regulated kinase 1/2 and the expression of differentiation-associated genes (including runt-related transcription factor 2, osteopontin and osteocalcin) during osteogenesis and resulted in reduced differentiation of BM-MSCs. The results indicate the potential role of ANX A1 in the regulation of BM-MSC proliferation and osteogenic differentiation.