The development of bone tissue depends on the interactions between osteogenic cells and the surrounding vasculogenic tissue, such as endothelial cells. Apart from the action of paracrine factors, this interaction is achieved through intercellular gap junction channels. Furthermore, increasing evidence points to the contribution of microRNAs (miR) in this communication. Now, Yan Zhou and colleagues (Fan et al., 2018) set out to gain insight into the molecular mechanisms of cell coupling and the conditions needed to engineer pre-vascularised bone tissue in vitro. The authors co-culture rat bone-marrow derived mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs) and observe the formation of gap junctions from connexin 43. Importantly, miR-200b transfers from BMSCs to HUVECs, which is promoted by transforming growth factor β (TGF-β). The authors show that the decrease of miR-200b in BMSCs stimulates osteogenic differentiation, whereas in HUVECs, miR-200b downregulates expression of angiogenic genes. Taken together, this work describes miR-200b as an important regulator for osteogenesis and angiogenesis. In addition, the modulation of miR-200b expression or its intercellular transfer in co-culturing approaches could further lead to the improvement of bone tissue vascularisation in vitro.
