Endothelial cell surface-associated keratan sulfate after excimer laser photoablation of the anterior rabbit cornea

PURPOSE: The expression of keratan sulfate on the surfaces of corneal endot helial cells is altered when the cells are responding to injury. The purpos e of this study was to investigate whether excimer laser surgery affected c orneal endothelial cells and the levels of keratan sulfate associated with them. METHODS: We performed 14 bilateral, transepithelial phototherapeutic kerate ctomies in rabbits using a Nidek EC-5000 excimer laser. Ablations were 6 mm in diameter and 50 mu m, 150 mu m, or 240 mu m deep. At various times foll owing surgery the endothelium was immunolabeled for keratan sulfate and exa mined by scanning electron microscopy. Four untreated corneas were also exa mined. RESULTS: Three days after surgery, endothelial cells were not flat but were rounded or domed, a finding that was more pronounced after deeper ablation s. No rounded cells, however, were seen at post-operative day 12. Keratan s ulfate immunolabel was elevated on endothelial cells 3 days after surgery. By postoperative day 36, its expression was normal under the 50-mu m ablati ons, but remained elevated under one of two 240-mu m ablations. CONCLUSIONS: Corneal endothelial cells take on a rounded appearance in the early stages after excimer laser photoablations in rabbits, especially afte r deeper ablations. The apical surface of the endothelium also transiently expresses elevated levels of cell surface-associated keratan sulfate follow ing surgery. These changes appear to be responses to some aspect of the sur gery, and may have physiological implications.