Morphologic observations on experimental vascularization in the rat

The morphologic evolution of the early events of corneal vascularization in the rat cornea induced by silver nitrate cautery were followed by light and electron microscopy. An initial acute inflammatory response occurred within the first 6 hours after cautery as evidenced by vascular dilation, diapedesis of leukocytes, and an increased vascular permeability, as manifested by distended lymphatics and the presence of extravascular fibrin. At 24 hours after injury, the hypertrophy and the prominence of nucleoli and the presence of abundant polyribosomes were the initial suggestion that vascular endothelial cells and pericytes had entered the mitotic cycle. Nine hours later, at 33 hours after cautery, the first new vessels were observed as sprouts from the capillary arcade and postcapillary venules. The experiments reemphasize the association of acute inflammation and corneal vascularization in this model and underscore the early occurrence of vascular endothelial cell replication.