Mast Cell Activation Accelerates the Normal Rate of Angiogenesis in the Chick Chorioallantoic Membrane

Abstract

Using shell-less cultures of chick embryos, the effect of mast cell degranulation on normal rates of angiogenesis in the chorioallantoic membrane (CAM) was recorded from Day 6 to Day 9. Based on the centripetal ordering method with capillaries as the initial point of reference, the first two orders of pre- and postcapillary microvessels were evaluated. After infusion of compound 48/80 into the allantoic cavity, the normal proliferation rate of order-1 pre- and postcapillaries was markedly increased. Increases of second-order vessel numerical densities (number/cm2) were less than those of the order-1 vessels. Thus, length densities (mean length × numerical density) were increased for the order-1 vessels only. During the accelerated rate of CAM angiogenesis, endothelial restriction of FITC–dextran 150 remained uniformly high. Hence, secreted mast cell products likely worked synergistically with endogenous CAM angiogenic factors between Days 6 and 9, without increasing rates of macromolecular extravasation. However, histamine injection into the allantoic cavity at Day 10, in conjunction with calcium supplementation of the shell-less cultures at Day 9, elevated the rate of FITC–dextran 150 extravasation. Whether differentiation of this transendothelial pathway is required for enhancement of CAM angiogenesis after Day 10 remains uncertain.