Lympho-hematopoietic development from human embryonic stem cells

Derivation of multiple blood cell lineages from human embryonic stem cells (hESCs) clearly establishes these cells as an important model system to better characterize human hematopoietic ontogeny. However, the progenitor cells that give rise to mature hematopoietic lineages, the cellular and molecular mechanisms that regulate their development, as well as the lymphoid potential of hESCs, remain poorly characterized. The goal of this project was to prospectively isolate and characterize the earliest hematopoietic precursor cells derived from hESCs and investigate the role of Wnt signaling for their development. In addition, we investigated the lymphoid potential of hESC-derived progenitor cells by differentiation into natural killer (NK) cells that were functionally evaluated in vivo and in vitro.; By detailed flow cytometric analysis of differentiated hESCs over a defined time-course, we identify development of two waves of CD34+ cells. The first wave consists of CD34brightCD31+Flk1 + cells with ability to differentiate into both hematopoietic and endothelial cells, whereas the second wave consists of CD34dimCD45 + cells restricted to the hematopoietic lineage. Inhibition of canonical Wnt signaling dramatically decreases development of both progenitor cell populations, whereas stimulation of Wnt signaling accelerates their development.; Next, we better characterized the lymphoid developmental potential of the CD34dimCD45+ cells by the ability of hESCs to differentiate into NK cells. Using a two-step differentiation process we find that hESC-derived NK cells express a wide repertoire of activating and inhibitory receptors similar to NK cells derived from other sources. Functional analysis demonstrates that these hESC-derived NK cells acquire in vitro cytolytic activity against a wide range of tumor cell lines. More importantly, hESC-derived NK cells demonstrate potent in vivo anti-tumor activity in a xenogeneic human tumor model.; Taken together, these studies characterize the earliest hematopoietic progenitors as they develop from hESCs during in vitro differentiation, and an important role for Wnt signaling in promoting their development. This is an import step towards approaching more defined conditions to facilitate more effective development of hematopoietic progenitors from hESCs. This will translate into even more efficient derivation of NK cells from hESCs with a potential use for cancer immunotherapy.