Corneal Epithelial Regeneration Is Accelerated in Le-AP-2 Mutant Mice

Abstract

Purpose:: Our lab has previously demonstrated the importance of transcription factor AP-2α in early eye development as well as in the regenerating corneal epithelium. It has also been shown that Pax6 directs the activity of the gelatinase B (gelB) promoter in conjunction with AP-2α during corneal wound healing. The specific role of AP-2α during wound re-epithelialization, however, has not yet been tested. In this study we examine the wound healing response in Le-AP-2α mutant mice, in which AP-2α has been conditionally deleted from the corneal epithelium.

Methods:: Le-AP-2α mutant mice were generated using the Cre/loxP system, in which a targeted deletion removes AP-2α from the lens placode and its derivatives, including the corneal epithelium. Wild type and Le-AP-2α mice were sacrificed and corneal epithelia were debrided within a fixed radius. Eyes were enucleated and cultured. Re-epithelialization was observed at 18 hours with topical fluorescein. Images were captured, enlarged and the change in radius for each wound was subsequently measured. The changes in area and rates of re-epithelialization were calculated accordingly. Wound edge characteristics were also examined with histological cross sections.

Results:: Observation of the wounds after 18 hours revealed that Le-AP-2α mutant corneas (n=7) re-epithelialized faster than wild type corneas (n=7) with a significance of p<0.07. Histological sections of the wounded wild type eyes revealed that the migrating wound edge stratified during re-epithelialization. In contrast, cells in the resurfaced epithelia of the mutant corneas were extremely flattened, suggestive of improper post-wound epithelial stratification in the Le-AP-2α mutant mice.

Conclusions:: These data demonstrate that in the absence of AP-2α (Le-AP-2α mice), corneal regeneration is accelerated and occurs abnormally. These findings are similar to previous studies utilizing Pax6^+/- (sey) and gelB knockout mice, which exhibit faster corneal re-epithelialization and altered epithelial morphology as compared to wild type littermates. Since AP-2α and Pax6 are known to interact to control expression of gelatinase B, our future studies will examine gelatinase B expression and other candidate downstream genes within this model.

Keywords: cornea: epithelium • wound healing • transcription factors