BMP Signaling Is Crucial for Regulation Vascular Progenitor Development in Human Embryonic Stem Cells.

Abstract 3037

Poster Board II-1013

The generation of vascular cells from pluripotent stem cells, including human embryonic stem cells (hESCs) and induced pluripotent stem (iPS) cells, may facilitate tissue transplantation, reperfusion of ischemic tissues, and treatment of pathologies in which endothelial cell dysfunction exists. The signals that direct pluripotent stem cell differentiation into lineage-specific cells remain largely unknown. To identify vascular progenitor cells during hESC differentiation, we characterized various subpopulations that may differentiate into endothelial cells (ECs) and smooth muscle cells (SMCs). In our newly established serum-free medium, hESCs sequentially differentiated into CD34+CD31-, CD34+CD31+, and then CD34-CD31+ cells. Real-time PCR analysis indicated that EC- and SMC-specific genes, including VEGFR2, Tie2, VE-Cad, vWF, SMA, SM22-alpha, calponin, and caldesmon, were expressed significantly high in CD34+CD31+ cells. Furthermore, the CD34+CD31+ cells that were cultured in EC or SMC growth medium had high differentiation potential to become ECs and SMCs. These data suggested that CD34+CD31+ cells contain vascular progenitor cells. By treating hESCs with various factors at different time points, we found that BMP4 was critical to initiate hESC differentiation into CD34+CD31+ progenitor cells, whereas VEGF and FGF2 facilitated CD34+CD31+ cell development in the later stage. Conversely, TGFbeta promoted CD34+CD31- cells that were unable to give rise to ECs and SMCs. In addition, TGFbeta blocked the development of CD34+CD31+ cells induced by BMP4, suggesting that TGFbeta signaling negatively regulates the development of CD34+CD31+ cells during hESC differentiation. DNA microarray analysis indicated that a number of mesodermal genes were increased in BMP4-induced CD34+ cells, and a number of ectodermal genes were increased in TGFbeta-induced CD34+ cells. Therefore, the roles of BMP and TGFbeta signals in lineage differentiation may be inversely reflected in mesoderm and ectoderm. In addition, several pluripotent genes were expressed in TGFbeta-induced CD34+ cells, suggesting that TGFbeta signaling affects maintenance of stem cell pluripotency. The BMP-Smad inhibitor, dorsomorphin, inhibited phosphorylation of Smad1/5/8, and blocked hESC differentiation to CD34+CD31+ progenitor cells, suggesting that BMP Smad-dependent signaling is critical for CD34+CD31+ vascular progenitor development. Our findings provide new insight into how pluripotent hESCs differentiate to generate vascular cells.