TGM2 inhibition with cysteamine hydrochloride does not impact corneal epithelial and stromal wound healing in vitro and in vivo

Abstract

Purpose : Tissue transglutaminase 2 (TGM2), a protein cross-linker associated with scar tissue development following wound healing, is integral for epithelial cell migration and adhesion and involved in the transformation of keratocytes to fibroblasts and myofibroblasts (“KFM” transformation). We hypothesized that TGM2 inhibition with cysteamine hydrochloride (CH), the active compound in CystaranÒ, would not impair epithelial migration in vitro, would be safe for application to epithelial and stromal wounds, and would result in decreased corneal haze formation following stromal wound healing.

Methods : CH was applied to corneal epithelial cells in vitro and migration assays were performed. 3 New Zealand white rabbits received bilateral corneal epithelial wounds, and 8 rabbits received bilateral stromal wounds by PTK. In each trial, one eye received CH and the contralateral eye received vehicle control, QID (until healed or until euthanasia, respectively). Rabbits received daily ophthalmic examinations, inflammation scoring, and fluorescein photography. SD-OCT was also performed at fixed time-points in the stromal wound trial. Corneas from the stromal trial were collected following euthanasia at day 28 or 42, and H&E, IHC, qPCR, and Western blots were performed to assess healing and KFM transformation.

Results : Epithelial cell migration was unaffected by CH in vitro. Topical application of CH to experimentally wounded rabbit corneas was safe following both epithelial wounding and stromal wounding, with no difference in healing found between treated versus control eyes regardless of depth of wound. There was no difference in KFM transformation in vitro or in stromal haze development in vivo between CH treated and control tissues with comparable haze areas on OCT and a-smooth muscle actin expression in corneal tissue.

Conclusions : Despite previous reports highlighting the importance of TGM2 in epithelial cell processes, no effect on corneal epithelial cell migration or epithelial or stromal wound healing was found in this study. These results support the safe use of this compound in patients, including when corneal wounds are present. There was no effect on corneal scar tissue formation in this study, highlighting the need for future studies investigating additional inhibitors.

This is a 2021 ARVO Annual Meeting abstract.