Development of the hemangioblast defines the onset of hematopoiesis in human ES cell differentiation cultures

Abstract

The onset of hematopoiesis in the mouse embryo and in the embryonic stem (ES) cell differentiation model is defined by the emergence of the hemangioblast, a progenitor with both hematopoietic and vascular potential. While there is evidence for the existence of a hemangioblast in the mouse, it is unclear if this progenitor develops during the establishment of the human hematopoietic system. In this report, we have mapped hematopoietic development in human ES cell (hESC) differentiation cultures and demonstrated that a comparable hemangioblast population exists. The human hemangioblasts were identified by their capacity to generate blast colonies that display both hematopoietic and vascular potential. These colony-forming cells express the receptor tyrosine kinase KDR (VEGF receptor 2) and represent a transient population that develops in BMP-4-stimulated embryoid bodies (EBs) be IntroductionThe earliest stage of hematopoietic development in the mouse has been historically associated with the appearance of yolk sac blood islands that consist of clusters of primitive erythroblasts surrounded by maturing endothelial cells. [1][2][3] The close temporal and spatial development of the hematopoietic and endothelial cells in these blood islands provided the basis for the hypothesis that these lineages share a common ancestor, a progenitor known as the hemangioblast. 4,5 While expression analyses 6-10 and gene targeting approaches [11][12][13][14] have provided circumstantial evidence in support of this concept, it was studies using the embryonic stem (ES) cell differentiation model that first identified a progenitor with properties of the hemangioblast. 15,16 When cultured in methylcellulose, these progenitors generate immature blast colonies that display both hematopoietic and vascular potential. 15 The cell that initiates these colonies, the blast colony-forming cell (BL-CFC) or hemangioblast, expresses the receptor tyrosine kinase Flk-1 and the mesodermal gene T (brachyury), indicating that it represents a population undergoing mesoderm specification to the hematopoietic and vascular lineages. 17 A progenitor comparable with the BL-CFC has also been identified in the early gastrulating embryo. 18 Similar to the BL-CFC, the embryo-derived progenitor displays primitive erythroid and myeloid potential and expresses both Flk-1 and T. Mapping studies revealed that the embryo hemangioblast is found at highest numbers in the posterior region of the primitive streak and not in the yolk sac, an observation that further supports the interpretation that this progenitor represents a transient mesodermal population undergoing hematopoietic and vascular commitment. The identification of the hemangioblast in the primitive streak of the early embryo demonstrates that hematopoietic commitment initiates earlier than previously described, prior to the establishment of the yolk sac blood islands. The striking similarities between the ES cell-and embryo-derived hemangioblasts add strong support to a growing body of evidence indicating tha...

Pluripotent stem cells reveal erythroid-specific activities of the GATA1 N-terminus

“…We investigated the functions of the GATA1 N-terminus by analyzing induced pluripotent stem cells (iPSCs) from patients with GATA1s mutations and Gata1 gene-disrupted murine embryonic stem cells (ESCs). Both ESCs and iPSCs self renew in culture and generate multiple hematopoietic lineages through directed in vitro differentiation (15,16). Our findings provide 2 major mechanistic insights into functions of the GATA1 N-terminus and pathophysiologies of human diseases associated with its loss.…”

Molecular and developmental biology of the hemangioblast

“…Therefore, the hemogenic endothelial cells have characteristics of definitive hemangioblasts in late somite stage embryos (Jaffredo et al, 2005;Tavian and Peault, 2005). These early observations in chick, mouse, and human embryos play an important role in the evolution of the hemangioblast concept and the ultimate identification of hemangioblasts in mouse and human ESC-derived embryoid bodies (EBs), and mouse and zebrafish embryos as described below (Choi et al, 1998;Lu et al, 2006;Vogeli et al, 2006;Kennedy et al, 2007).…”

“…This hypothesis is supported by studies using in vitro mouse and human embryonic stem cell (ESC) cultures, and in vivo animal model systems, including zebrafish, chick, and mice. By using mouse and human ESC cultures, blast-colonyforming cells (BL-CFCs) are isolated and characterized clonally to produce both endothelial and hematopoietic cells in the presence of vascular endothelial growth factor-A (VEGF-A) and bone morphogenetic protein-4 (BMP4; Choi et al, 1998;Nishikawa et al, 1998;Lu et al, 2006;Kennedy et al, 2007). Fate mapping in the zebrafish gastrula suggests that hemangioblasts are interspersed with hematopoietic and endothelial progenitors in the ventral-lateral mesoderm (Lee et al, 1994;Vogeli et al, 2006).…”

Early Exposure of Murine Embryonic Stem Cells to Hematopoietic Cytokines Differentially Directs Definitive Erythropoiesis and Cardiomyogenesis in Alginate Hydrogel Three-Dimensional Cultures

“…Current protocols for in vitro production of RBCs from ESCs are fragmented and involve multiple (three) stages: (1) maintenance/expansion of undifferentiated ESCs, (2) spontaneous differentiation through formation of embryoid bodies (EBs) incorporating all three germ layers, and (3) dissociation of EBs with re-plating for terminal differentiation to desired lineages [16,18]. Ideal conditions for such cultures are not fully identified but result in sub-optimal control of differentiation and heterogeneity [19,20].…”

“…H ematopoiesis in the early mouse embryo has been recapitulated by in vitro differentiation culture of human and murine embryonic stem cells (mESCs) by which mesodermal cells commit to the hematopoietic lineage before giving rise to other blood cells [1][2][3][4][5][6][7]. During embryogenesis, hematopoietic cells originate from the lateral plate mesoderm in an ordered program of development occurring in conjunction with cells of the cardiovascular system and share a common precursor, the hemangioblast [8][9][10][11].…”