Corneal scarring is a major cause of blindness worldwide with few effective therapeutic options. Finding a treatment would be of tremendous public health benefit, but requires a thorough understanding of the complex interactions that underlie this phenomenon. Here, we tested the hypothesis that the large increase in expression of Semaphorin 3A (SEMA3A) in corneal wounds contributes to the development of stromal fibrosis. We first verified this increased expression in vivo, in a cat model of photorefractive keratectomy-induced corneal wounding. We then examined the impact of adding exogenous SEMA3A to cultured corneal fibroblasts, and assessed how this affected the ability of transforming growth factorbetal (TGE-beta 1) to induce their differentiation into myofibroblasts. Finally, we examined how siRNA knockdown of endogenous SEMA3A affected these same phenomena. We found exogenous SEMA3A to significantly potentiate TGE-beta 1's profibrotic effects, with only a minimal contribution from cell-intrinsic SEMA3A. Our results suggest a previously unrecognized interaction between SEMA3A and TGE-beta 1 in the wounded cornea, and a possible contribution of SEMA3A to the regulation of tissue fibrosis and remodeling in this transparent organ. (C) 2019 Elsevier Inc. All rights reserved.