Intravital Video Microscopic Analysis of the Mucosal Microvascular Dysfunction Associated with Intestinal Allograft Rejection in the Rat

Abstract

The mucosa of the intestinal allograft is sensitive to microvascular injury during rejection. Using intravital video microscopy we have directly examined the microcirculatory changes occurring in the mucosal villi of rejecting rat intestinal allografts. Vascularized, heterotopic, intestinal transplants were performed in three groups: 1) Sham operated Lewis rats (n:5), 2) Lewis to Lewis isografts (n:5), 3) ACI to Lewis allografts (n:5) . Analysis of the mucosal microvasculature revealed a significant decrease (p<0.05) in the area ratio of perfused capillaries to nonvascular mucosal tissue in rejection allografts versus isografts and sham operated animals. Allografts also demonstrated significantly larger (p<0.05) perfused capillary diameters as compared to sham operated animals, but not isografts. Only 3.3% of perfused capillaries measured less than 4.0µm in the allograft group as compared to 8.8% of isograft and 13.9% of sham perfused capillaries. Together this evidence suggests a decrease in the mucosal capillary density of rejecting allografts as a result of occlusion of the smaller diameter capillaries.