Identification and Characterization of Hemoangiogenic Progenitors During Cynomolgus Monkey Embryonic Stem Cell Differentiation

We identified intermediate-stage progenitor cells that have the potential to differentiate into hematopoietic and endothelial lineages from nonhuman primate embryonic stem (ES) cells. Sequential fluorescence-activated cell sorting and immunostaining analyses showed that when ES cells were cultured in an OP9 coculture system, both lineages developed after the emergence of two hemoangiogenic progenitor-bearing cell fractions, namely, vascular endothelial growth factor receptor (VEGFR)-2(high) CD34(-) and VEGFR-2(high) CD34(+) cells. Exogenous vascular endothelial growth factor increased the proportion of VEGFR-2(high) cells, particularly that of VEGFR-2(high) CD34(+) cells, in a dose-dependent manner. Although either population of VEGFR-2(high) cells could differentiate into primitive and definitive hematopoietic cells (HCs), as well as endothelial cells (ECs), the VEGFR-2(high) CD34(+) cells had greater hemoangiogenic potential. Both lineages developed from VEGFR-2(high) CD34(-)or VEGFR-2(high) CD34(+) precursor at the single-cell level, which strongly supports the existence of hemangioblasts in these cell fractions. Thus, this culture system allows differentiation into the HC and EC lineages to be defined by surface markers. These observations should facilitate further studies both on early developmental processes and on regeneration therapies in human.