Embryonic vasculogenesis and hematopoietic specification

Abstract

Vasculogenesis is the process by which blood vessels are formed de novo. In mammals, vasculogenesis occurs in parallel with hematopoiesis, the formation of blood cells. Thus, it is debated whether vascular endothelial cells and blood cells are derived from a common progenitor. Whether or not this is the case, there certainly is commonality among regulatory factors that control the differentiation and differentiated function of both cell lineages. VEGF is a major regulator of both cell types and plays a critical role, in coordination with other signaling pathways and transcriptional regulators, in controlling the differentiation and behavior of endothelial and blood cells during early embryonic development, as further discussed herein.

Keywords: endothelial cell specialization; endothelium; hematopoiesis; hemogenic endothelium; vasculogenesis.

Figure 1

Molecular regulation of primitive hematopoietic specification and vascular remodeling during murine development. (A) Schematic representation of the developing murine embryo, highlighting the primary sites of embryonic hematopoiesis. (B) Schematic representation of endoderm-derived molecular signals with known roles in the specification of mesodermal precursors. (C) Schematic representation of primitive hematopoietic development within the yolk sac vascular plexus.

Figure 2

Theories of hematopoietic specification during embryogenesis. Schematic representation of the three major alternative theories for the developmental emergence of primitive endothelial and hematopoietic lineages: (A) the bipotent “hemangioblast”, (B) “hemogenic” endothelium and (C) gastrulation-specified endothelial and hematopoietic progenitors.