Angiogenic activity in injured rat corneas as assayed on the chick chorioallantoic membrane

The temporal appearance of an angiogenic effect in chemically cauterized rat corneas was determined by studying the responses that they induced in the vessels of the chick chorioallantoic membrane (CAM). Injured rat corneas were grafted to the CAM from 90 minutes to 7 days after cautery. As controls, uninjured rat corneas and corneas of healthy rats cauterized immediately after death were also grafted. The vascular responses to the grafts were graded in a masked fashion by stereoscopic biomicroscopy on a five-tiered scale, by evaluations of projected colored photographs on the same scale, and by histologic examination of the grafts. Separate coefficients of angiogenesis were determined for the stereoscopic and photographic evaluations. We detected significant differences between corneas of healthy rats that were uninjured or cauterized chemically immediately after death and those that were cauterized in the living rat. Uninjured corneas and corneas cauterized postmortem elicited a mild vascular response in the CAM, as reflected by low coefficients of angiogenesis. Whereas blood vessels were not detected in corneas injured postmortem, some normal corneas vascularized but only after being on the CAM for at least 7 days. The coefficients of angiogenesis of corneas that were cauterized during life were significantly higher than those of both control groups prior to grafting after comparable times on the CAM. Corneas vascularized on the CAM included those that were cauterized as soon as 90 minutes prior to grafting. The strongest vascular responses, as reflected by coefficient of angiogenesis and the frequency of histological confirmed nucleated avian erythrocytes with intracorneal blood vessels, were found with corneas that were grafted to the CAM 3 days after chemical cauterization. Corneas that vascularized on the CAM were associated with a prominent leukocytic infiltrate suggestively derived from the chick embryo. The results suggest that chemically cauterized rat corneas contain a chemoattractant for polymorphonuclear leukocytes within 90 minutes of injury and that such polymorphonuclear leukocytes or other components of the injured corneas possess the ability to stimulate angiogenesis on the CAM.