Unique Parameters in the Healing of Linear Partial Thickness Penetrating Corneal Incisions in Rabbit: Immunohistochemical Evaluation

Abstract

The healing of penetrating nonperforating linear corneal incisions in rabbit was analysed immunohistochemically. Regeneration of the basement membrane (BM) zone was evaluated by analysing the following components using monoclonal antibodies (MAbs): 1) an antigen designated AgHEBM1 (a 66k Mr polypeptide), 2) type VII collagen which is associated with anchoring fibrils and 3) an antigen designated Ag63/D7 which is associated with the lamina densa and anchoring plaques. Concomitant activity in the regenerating stroma was evaluated by analysing the distribution of 1) fibronectin, 2) keratan sulfate and 3) a fetal antigen, designated AgM12, (an intermediate filament associated protein with a Mr of 130k). Synthesis of the BM zone components was not evident at day 2 postwounding but was seen at day 7, only at the deepest aspects of the wounds. Re-establishment of a continuous BM zone was evident by day 60. The stromal regeneration had started by day 7, at the deepest aspect of the wounds, as judged from the distribution of stromal antiens including the fetal antigen AgM12. The number of activated cells (cells exressing AgM12) had decreased significantly by day 30 and diminished by day 60. Between day 30 and day 180 the thickness of the regenerated tissues had not increased significantly although the stroma had not yet reached its normal thickness. Even after six months, the epithelial plug persisted and the concentration of the sulfated epitopes of keratan sulfates in the regenerated stromal matrix were less than in the surrounding nonwounded regions. The cessation of expression of AgM12, by the cells in regenerating stroma, coincided with the relative decrease in extracellular matrix syntheses. The return of the stromal cells to the quiescent state also coincided with re-establishment of a continuous BM zone between the epithelium and the stroma in the regenerated tissue. These observations suggested that the synthesis, assembly and remodeling of stromal and epithelial extracellular matrices during the healing of penetrating corneal wounds may be influenced by the interactions between activated stromal cells and epithelial cells.