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 stud ies using the Griffonia simplicifolia I (GSI) lectin as a microvascula r marker indicated that capillary sprouting occurs in the clear ''wind ows'' of normal intact adult rat mesentery. The purpose of this study was to determine whether angiogenesis occurs uniformly within the mese nteric windows and whether maturational age affects the extent of angi ogenesis in the absence of any experimental of pathological perturbati on. 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 d erivative of the GSI lectin. Microvascular sprouting, indicating angio genesis, was found in all age groups, but was most frequent in the win dows sampled from the distal region of the small intestine when compar ed with those from the proximal region. The mean number of microvessel s per sample site was significantly higher in the distal windows of ad ults than in the weanling of juvenile rats. Angiogenesis was found to occur asymmetrically within the individual windows in the two adult gr oups, with significantly more angiogenesis on the intestinal side comp ared to that along the portal vessels. We conclude that the intestinal side is more prone to spontaneous angiogenesis than is the portal sid e. These results have important applications to the use of mesentery a s an assay system for intact vessels in adults and to the use of mesen tery as an in vivo model system to bridge the gap between our understa nding of angiogenesis in vivo and intact vascular systems. (C) 1994 Ac ademic Press, Inc.