Vasculogenesis in the chick embryo. An ultrastructural study

Abstract

The morphogenesis of the extra-embryonic circulatory system of the chick was studied by light and electron microscopy, from precirculatory stages until the beginning of the definitive circulation. Early mesodermal migrations of prospective vasoformative cells and formation of blood islands take place with minimal morphologically expressed cytodifferentiation. The earliest mesodermal clusters are not syncytial. Formation of vascular lumina is not due to lysis of central cells. Undifferentiated mesenchyme possesses the capacity to establish complex junctional devices at points of contact with like cells. The first formed blood islands show intimate relationships with endoderm. The initial capillary network is sinusoidal in type, the endothelium being unsupported by a basement membrane. The major vitelline vessels acquire a more complex anatomy but the capillaries retain this simple pattern throughout the period studied. Several phases in the histogenesis of vitelline vessels are recognized, which could be correlated with the known progression of arterial pressure patterns. Continuing differentiation and mesenchymal investment of vascular walls, after stages 22-23 of Hamburger and Hamilton ('511, in correspondence with the last sustained pressure elevation, leads to completion of the adult vascular structure.

In vitro differentiation of murine embryonic stem cells. New approaches to old problems.

“…Within these blood islands, clusters of hematopoietic cells are surrounded by endothelial cells which are believed to eventually establish the yolk sac vasculature (33, [37][38][39][40]. The close relationship between hematopoietic and vascular development is underscored by marked deficiencies of both cell types in embryos lacking the receptor tyrosine kinase Flk-1 (41).…”

Primitive and definitive erythropoiesis in the yolk sac: a birds eye view

“…From E2 to E5, yolk sac vasculature undergoes at least two phases of remodeling. Hemodynamic changes initiated by heart pulsation remodels early vascular plexus into arterial and venous trees between E2 and E3, followed by the remodeling from two-dimensional apposing arterial/venous trees to a three-dimensional paired arterial/venous network between E3 and E5 (Eichmann et al, 2005;Gonzalez-Crussi, 1971;le Noble et al, 2004;Nagai and Sheng, 2008;Van Mierop and Bertuch, 1967) (Fig. 4).…”

Hedgehog signaling is essential for endothelial tube formation during vasculogenesis

“…However, the first blood vessels within the embryo always form in mesoderm that is in close proximity to endoderm (Mato et al, 1964;Wilt, 1965;Gonzalez-Crussi, 1971;Mobbs and McMillan, 1979;Meier, 1980;Kessel and Fabian, 1985;Pardanaud et al, 1989). Furthermore, we have recently demonstrated that a signal originating from the endoderm is essential for the assembly of angioblasts into tubes (Vokes and Krieg, 2002a).…”