Effects of Topically Applied 0.1%Dexamethasone on Endothelial Healing and Aqueous Composition Following Experimental Corneal Alkali Wounds

The effects of topical dexamethasone on the endothelial healing and the change of aqueous composition were examined in the repair process of experimental corneal alkali wounds. Corneal alkali wounds were induced, then the eyes were treated topically with either 0.1%dexamethasone or abalanced salt solution[BSS]4 times per day for 8 weeks. Endothelial wound morphometry was performed after alizarin red and trypan blue staining. The concentrations of ascorbic acid, glucose, and the ions, Na, K , Ca2 and Mg2 , were measured in the aqueous humor. Endothelial healing in control corneas showed a biphasic pattern of healing:an initial short-term healing for the first week and then a late long-term healing following a secondary endothelial breakdown. Topical administration of 0.1%dexamethasone deterred endothelial healing during the early period and prevented secondary endothelial breakdown. Total repair process of endothelium was accelerated by the dexamethasone treatment. Among the various components of the aqueous humor examined, ascorbic acid seemed most sensitive to change caused by the alkali injury and dexametha-sone treatment. The present data indicate that dexamethasone may have a therapeutic potential in the management of endothelial healing after corneal alkali injury.

Optimal Concentrations of hEGF for Epithelial and Endothelial Healing in Corneal Alkali Wounds: An Organ Cultured Study

Optimal concentrations of hEGF for epithelial and endothelial healing after alkali-injury were determined in an organ cultured system. By using a 5.5 mmround filter paper, corneal alkali wounds (1N NaOH, 60sec.) were induced in the rabbit eyes and then the whole cornea with 1 mmscleral rim were excised.The excised corneas were immersed in the Eagle`s minimum essential medium supplemented with 5% Dextran, 1%antibiotics and different concentrations of hEGF (DaeWoong Pharma.Co.Ltd. Seoul, Korea), i.e., O (control), 0.01, 0.1, 1.0, 10, 100ng/ml. After tryphan blue staining, morphometric analysis was performed at 1, 2, 3, 4 and 6 days time periods. The healing rates were calculated by using an image analysis system. After 7 days, the corneas were processed for an immunohistochemical observation of proliferating cell nuclear antigen (PCNA) positive cells in the re-surfaced epithelium. Epithelial re-surfacing was significantly enhanced by the hEGF treatment at a concentration of 1.0ng/ml. The thickness of regenerated epithelium appeared to be increased in a dose-dependent man-ner. The rate of endothelial healing was increased at the concentration of 100ng/ml. The results indicate that epithelial healing was stimulated at about 100 times lower concentration of hEGF than endothelial healing.

Endothelial F-actin changes in the alkali burned rabbit cornea

The healing mechanism of corneal endothelium after alkali burn was not completely understood. Rabbit cornea was burned with 1N sodium hydxoside for 1 minute. Endothelial F-actin was stained with NBD-phallacidin in regular sequence to find out the details of endothelial healing after alkali burn. F-actin was completely destroyed leaving a sharp margin against the unaffected area 1 hour after the burn. In the 3, 5 and 7 day specimens, highly active F-actin reactions were noted at the wound margin. New multiple F-actin layers, arising from the intact endothelium near the wound margin, were noted in the 9 day specimen. In the 8 1/2 month specimen, the endothelial defected area was covered by large primitive cells, each of which showed F-actin fiber bundles in the cytoplasm with a large nuclear shadow. Nearly all of the large primitive cells showed F-actin fibers arranged in shapes of cell junctions. Twelve months after the burn, endothelial defects were not found. Nearly all of the endothelial cells were normal in size and shape except for some mushroom-like projections toward the anterior chamber in some areas. Nineteen months after the burn, the endothelial cells were normal. Endothelial wound healing process can be continued even 1 year after the alkali burn in rabbit cornea.