Research On Regulation Of Angiogenesis And Osteogenesis In Mesenchymal Stem Cells And Endothelial Cells Coculture

Coculture of mesenchymal stem cells(MSCs)and endothelial cells(ECs)in vitro to construct prevascularized bone tissue is one of the most direct and effective methods to solve the problem of mass transfer limitation in traditional bone tissue engineering.However,in the osteogenic induction environment,cocultured ECs have problems such as poor proliferation,low survival rate,and poor vascular-like network formation ability.Therefore,it is urgent to explore the factors that affect the angiogenesis of ECs and their mechanisms in coculture.In addition,fluid shear stress(FSS)is an important factor in regulating bone formation and bone remodeling in vivo.To construct prevascularized bone tissue by simulating the mechanical microenvironment in vivo,it is necessary to explore the influence and mechanisms of FSS loading on coculture of MSCs and ECs.Based on this,the study first investigated the effects and mechanisms of osteodifferentiating bone marrow mesenchymal stem cells(BMSCs)on the angiogenesis of human umbilical vein endothelial cells(HUVECs)to promote angiogenesis of cocultured HUVECs;Secondly,the effects of cyclic oscillating FSS on the physiological characteristics in cocultured cells and the regulatory mechanism were investigated to promote osteogenesis of prevascularized bone tissue engineering.The results of the study showed that the BMSCs isolated by the whole bone marrow adherence method conformed to the basic characteristics of MSCs in terms of morphology,surface antigen expression and three-differentiation capabilities.In a static osteogenic environment,coculture of BMSCs and HUVECs promoted the ALP activity and calcium deposition of BMSCs as well as the expression of osteogenic marker genes(ALP,Runx2,COLI,and OCN).However,the formation of vascular-like network in HUVECs was significantly inhibited.It is further found that osteogenic differentiated BMSCs express TSP-1 through the p38-p53 pathway,which leads to low proliferation and angiogenesis of HUVECs,decrease the phosphorylation levels of KDR,AKT,ERK1/2 and eNOS,increase apoptosis rate and activation level of apoptosis-related protein Caspase-3.Inhibiting the expression of TSP-1 in BMSCs restored angiogenesis of coculture.According to the previous screening in the laboratory,2 h/d of FSS was used in this research.It was found that FSS significantly promote the proliferation of cocultured cells by accelerating the cell cycle from G0/G1 phase to S phase,and no effect was observed on proliferation of monocultured BMSCs and monocultured HUVECs.FSS was beneficial to maintain the cell proportion of HUVECs in coculture under an osteoinductive environment.In addition,FSS further promoted ALP activity and calcium deposition in BMSCs based on coculture,significantly increased the mRN A levels of osteogenic markers(ALP,Runx2,COLI,and OCN),and the protein levels(OPN and OCN).Moreover,it was found that FSS up-regulated the expression of TGF-? in cocultured HUVECs,which further promoted the expression of Integrin ?1 in BMSCs,activated the downstream FAK-ERK1/2 signaling pathway,and up-regulated the expression of Runx2,thereby synergistically enhancing the osteogenic differentiation of BMSCs.This research provided a theoretical basis and guiding significance for improving the angiogenensis and osteogenesis of prevascularized bone tissue engineering based on coculture of MSCs and ECs,and established a foundation for the clinical transformation of engineered bone tissue.