The effect of gap junction-mediated transfer of miR-200b on osteogenesis and angiogenesis in a co-culture of MSCs and HUVECs

For successful engineering of pre-vascularized bone tissue in vitro, understanding the interactions between vasculogenic cells and bone-forming cells is a prerequisite. Mounting evidence indicates that microRNAs serve as the intercellular signals that allow cell-cell communication. Here, a new transfer machine, miR-200b, was explored in a coculture system between vasculogenic and osteogenic cells. Rat bone-marrow derived mesenchymal stem cells (BMSCs) formed functional gap junctions composed of connexin 43 (Cx43) with human umbilical vein endothelial cells (HUVECs), through which miR-200b can transfer from BMSCs to HUVECs to regulate osteogenesis and angiogenesis. As a negative regulator, the decrease in miR-200b level in BMSCs derepressed the expression of VEGF-A, leading to promoted osteogenic differentiation. Once inside HUVECs, miR-200b blunted the angiogenic potential of HUVECs by down-regulation of ZEB 2, ETS 1, KDR and GATA 2. Additionally, TGF-β was found to trigger the transfer of miR-200b to HUVECs. By adding TGF-β inhibitor SB431542 or neutralizing antibody, the formation of capillary-like structure in coculture could be partially rescued. These findings may be fundamental to the development of cell-based bone regeneration strategy.