Blood vessel formation in the avian limb bud involves angioblastic and angiotrophic growth

Abstract

The vasculature of the avian limb bud takes its origin from the intersomitic vessels as can be shown by ink perfusion of the embryo. While the primitive vessels form a central network in the early limb bud, an area of about 100 p m in width from the ectoderm inward remains free from lumenized vessels. However, this subectodermal avascular zone contains isolated angioblasts, which can be demonstrated by confocal laser scanning microscopy in connection with QH-1-staining. QH-1-positive cells from the avascular zone are capable of giving rise to endothelial cells when grafted ectopically into a "permissive" environment such as the dorso-lateral paraxial mesoderm. Several grafting sites are compared regarding their permissiveness for capillary formation. In order to investigate the origin of the QH-1-positive angioblasts we carried out injections of DiI-Ac-LDL, which is specifically taken up by endothelial cells and macrophages, and found the lumenized vessels and a few isolated cells in the peripheral limb mesoderm stained. In double-labelling studies combining DiI-Ac-LDL and QH-1, it can be shown that there exists a pool of isolated angioblasts that are only QH-l-positive, but have not incorporated DiI-Ac-LDL. In contrast to the lumenized vessels in the core of the limb bud, we found that angioblasts in the avascular zone do not proliferate, as shown by proliferation studies applying the BrdU-method to semithin sections in connection with QH-l-labelled parallel sections. We conclude that the vascularization of the avian limb bud is achieved by a combination of angiotrophic growth (sprouting of vessels) and angioblastic growth (recruitment of angioblasts from the limb mesoderm).0 1995 Wiley-Liss, Inc.

Erythropoiesis from acetyl LDL incorporating endothelial cells at the preliver stage

“…[30][31][32][33] The first DiI ϩ illumination was observed as early as 30 minutes after inoculation. One hour later, the whole vascular tree in the YS and the embryo proper was labeled.…”

Neurovascular Anatomy of the Embryonic Quail Hindlimb

“…Recent findings point to a similarity extending beyond anatomical pattern to that of shared molecular guidances molecules (Kitsukawa et al, 1995;Eberhart et al, 2000;Oosthuyse et el., 2001;Mukouyama et al, 2002Mukouyama et al, , 2005Bates et al, 2003;Vieira et al, 2007;Zacchigna et al, 2008). Studies have documented the neurovascular pattern of the quail and chick forelimb, and numerous studies have detailed the motor and sensory pattern of the chick hindlimb, however the neurovascular pattern of the quail hindlimb has yet to documented (Landmesser, 1978;Drushel et al, 1985;Tyrrell et al, 1990;Brand-Saberi et al, 1995;Scott, 1999, 2000;Taylor et al, 2001;Bates et al, 2002). …”

SDF-1 controls the muscle and blood vessel formation of the somite

“…The colonization of somite-derived angiogenic cells might mainly occur via the sprouting of blood vessels rather than progenitor cell migration found in myogenic progenitor cells. Brand-Saberi et al, (1995) have shown that the vasculature of the avian limb bud is accomplished mainly by the sprouting of vessels. We assume that somite-derived angiogenic progenitor cells differentiate into endothelial cells at the site of their origin and from there they move to the limb via blood vessel sprouting.…”

“…The vasculogenic capacity of the avascular zone depends on local influences, maybe mediated by the local extracellular matrix (Brand-Saberi et al, 1995). Reversely, ectopic vessels control extracellular matrix production.…”