REGIONAL DIFFERENCES IN SPONTANEOUSLY OCCURRING ANGIOGENESIS IN THE ADULT-RAT MESENTERY

Despite intensive study in the area of angiogenesis, relatively little is known about normal angiogenesis in adult animals. Preliminary studies using the Griffonia simplicifolia I (GSI) lectin as a microvascular marker indicated that capillary sprouting occurs in the clear ''windows'' of normal intact adult rat mesentery. The purpose of this study was to determine whether angiogenesis occurs uniformly within the mesenteric windows and whether maturational age affects the extent of angiogenesis in the absence of any experimental of pathological perturbation. Four groups of female Sprague-Dawley rats were used, ''weanling'' (4-5 weeks), ''juvenile'' (6-8 weeks), ''young adult'' (10-13 weeks), and ''adult'' (16-20 weeks). Microvessels sprouting into proximal and distal windows were delineated in whole mounts by use of fluorescent derivative of the GSI lectin. Microvascular sprouting, indicating angiogenesis, was found in all age groups, but was most frequent in the windows sampled from the distal region of the small intestine when compared with those from the proximal region. The mean number of microvessels per sample site was significantly higher in the distal windows of adults than in the weanling of juvenile rats. Angiogenesis was found to occur asymmetrically within the individual windows in the two adult groups, with significantly more angiogenesis on the intestinal side compared to that along the portal vessels. We conclude that the intestinal side is more prone to spontaneous angiogenesis than is the portal side. These results have important applications to the use of mesentery as an assay system for intact vessels in adults and to the use of mesentery as an in vivo model system to bridge the gap between our understanding of angiogenesis in vivo and intact vascular systems. (C) 1994 Academic Press, Inc.