Human ESC-derived hemogenic endothelial cells undergo distinct waves of endothelial to hematopoietic transition

Author(s): Rafii, Shahin; Kloss, Christopher C.; Butler, Jason M.; Ginsberg, Michael; Gars, Eric; Lis, Raphael; Zhan, Qiansheng; Josipovic, Pavle; Ding, Bi-Sen; Xiang, Jenny; Elemento, Olivier; Zaninovic, Nikica; Rosenwaks, Zev; Sadelain, Michel; Rafii, Jeremie A.; James, Daylon

Several studies have demonstrated that hematopoietic cells originate from endothelium in early development; however, the phenotypic progression of progenitor cells during human embryonic hemogenesis is not well described. Here, we define the developmental hierarchy among intermediate populations of hematopoietic progenitor cells (HPCs) derived from human embryonic stem cells (hESCs).

We genetically modified hESCs to specifically demarcate acquisition of vascular (VE-cadherin) and hematopoietic (CD41a) cell fate and used this dual-reporting transgenic hESC line to observe endothelial to hematopoietic transition by real-time confocal microscopy. Live imaging and clonal analyses revealed a temporal bias in commitment of HPCs that recapitulates discrete waves of lineage differentiation noted during mammalian hemogenesis. Specifically, HPCs isolated at later time points showed reduced capacity to form erythroid/megakaryocytic cells and exhibited a tendency toward myeloid fate that was enabled by expression of the Notch ligand Dll4 on hESC-derived vascular feeder cells.

These data provide a framework for defining HPC lineage potential, elucidate a molecular contribu-tion from the vascular niche in promoting hematopoietic lineage progression, and distinguish unique subpopulations of hemogenic endothelium during hESC differentiation.