Hemogenic endothelium (HE) has been recognized as a source of hematopoietic stem cells (HSCs) in the embryo. Access to human HE progenitors (HEPs) is essential for enabling the investigation of the molecular determinants of HSC specification. Here, we show that HEPs capable of generating definitive hematopoietic cells can be obtained from human pluripotent stem cells (hPSCs) and identified precisely by a VE-cadherin+CD73-CD235a/CD43- phenotype. This phenotype discriminates true HEPs from VE-cadherin+CD73+ non-HEPs and VE-cadherin+CD235a+CD41a- early hematopoietic cells with endothelial and FGF2-dependent hematopoietic colony-forming potential. We found that HEPs arise at the post-primitive-streak stage of differentiation directly from VE-cadherin-negative KDRbrightAPLNR+PDGFRαlow/- hematovascular mesodermal precursors (HVMPs). In contrast, hemangioblasts, which are capable of forming endothelium and primitive blood cells, originate from more immature APLNR+PDGFRα+ mesoderm. The demarcation of HEPs and HVMPs provides a platform for modeling blood development from endothelium with a goal of facilitating the generation of HSCs from hPSCs
Bibliographical noteFunding Information:
We thank Dr. Toru Nakano for providing OP9 cells, Dr. Dietmar Vestweber for providing endomucin antibodies, Su-Chun Zhang for providing H9-EGFP cells, and Gene Uenishi for editorial assistance. This work was supported by funds from the National Institute of Health (R01 HL081962, U01HL099773, P01 GM081629, and P51 RR000167), the Charlotte Geyer Foundation, and the Lupus Foundation of America. K.S. is supported by funds from the Department of Pharmacology, Faculty of Science, Mahidol University, Bangkok, Thailand. J.A.T. owns stock in, serves on the Board of Directors of, and serves as Chief Scientific Officer of Cellular Dynamics International. J.A.T. also serves as Scientific Director of the WiCell Research Institute. I.S. owns stock in and is a scientific founder of Cellular Dynamics International. I.S. is also a scientific founder of Cynata. M.V. is a scientific founder of Cynata.