Localized vascular regression during limb morphogenesis in the chicken embryo: II. Morphological changes in the vasculature

Abstract

The regression of blood vessels in the distal wing bud of chicken embryos from stages 19 to 31 was examined by light and electron microscopy. The vessels were double-labelled by an injection of Monastral blue B (MB) to label the regressing endothelial cells, followed 6-48 hours later with an injection of India ink which marked the lumens of patent vessels. Prior to stage 26 the vessels contained only India ink since the endothelial cells were not phagocytic at this stage. Vessels at stage 26 or later were often double-labelled, with MB sequestered in the endothelial cell cytoplasm and India ink in the vessel lumens. After stage 27 cells not associated with lumens, but labelled with MB, were observed in areas undergoing vascular regression. Ultrastructural changes in the endothelial cells as the vessels regressed included formation of luminal and abluminal processes, long complex junctions, and vacuoles containing MB. In many involuting vessels the endothelial cells appeared normal even though the lumens were collapsed. Occasionally, isolated pyknotic cells were observed in regions that had been previously vascularized. At stage 31 cells in the developing cartilage had vacuoles containing MB. Our study suggests that blood vessels may disappear from the prechondrogenic zone of the distal wing bud by several mechanisms. These could include a type of cell death that does not elicit a cellular infiltrate, migration of the endothelial cells away from vascularized regions, and/or transdifferentiation into cells that resembled chondrocytes.

Regression of blood vessels in the ventral velum of Xenopus laevis Daudin during metamorphosis: light microscopic and transmission electron microscopic study

“…The formation of luminal and abluminal cytoplasmic processes, vacuolation, and cytoplasmic and nuclear chromatin condensation indicated the beginning of endothelial cell degeneration. These changes closely resembled those described as occurring in early stages of physiological blood vessel regression in the corpus luteum (O'Shea et al 1977 ;Modlich et al 1996), in limb morphogenesis (Latker et al 1986) and in experimentally induced regression of corneal capillaries (Ausprunk et al 1978). A prominent feature of capillary involution was basal lamina thickening and local folding.…”

“…In the ventral velum of tadpoles of Xenopus laevis we identified only few apoptotic endothelial cells with fragmented DNA on applying the ApopTagFluorescein kit in vessels which still exhibited a normal appearance. However, from the ultrastructural changes observed in the velar capillaries which showed many similarities to those seen in other systems (O'Shea et al 1977 ;Ausprunk et al 1978 ;Latker & Kuwabara, 1981 ;Hurle et al 1985 ;Latker et al 1986 ;Lang et al 1994 ;Modlich et al 1996) we have shown that during amphibian metamorphosis capillary regression in the filter apparatus and the ventral velum involved programmed death (apoptosis) of endothelial cells.…”

Apoptosis in Glomerular Endothelial Cells during the Development of Glomerulosclerosis in the Remnant-Kidney Model

“…The disappearance of endothelial cells results in the regression of the vascular system which is often seen in embryogenesis, wound healing, and resolution of tumors [43, 44, 45]. In the processes of the vascular regression, apoptosis plays a crucial role.…”

Apoptosis During Cardiovascular Development

“…Examples of the latter include the paired first, second, and fifth aortic arches and one of the fourth arches (right in mammals, left in birds), as well as vessels in the microvasculature, especially at sites of bone formation. 62,63 These processes may be dominated by cell death, although cell migration or transdifferentiation to mesenchyme, 62 matrix degradation, and internal division of vessels to form multiple smaller channels (intussusception) 64,65 may also occur. In addition to vessel deletion, the vasculature undergoes continuous reorganization during development that occasionally is very dramatic.…”