Conditioned medium from human umbilical vein endothelial cells markedly improves the proliferation and differentiation of circulating endothelial progenitors

The endothelial-promoting effect of CM seems to be related to smaller vesicles including exosomes (sEV/exo) contained in this medium and transferred to CB CD34+ EPCs: in fact, purified preparations of sEV/exo isolated from CM mimicked the effect of CM to sustain endothelial formation. These observations provided the interesting indication that mature ECs exert a stimulatory effect on endothelial cell differentiation from CD34+ cells.