Lacking TRPA1 Cation Channel Impairs Primary Closure of a Stromal Incision Injury in a Mouse Cornea

Abstract

The cornea is a highly sensory, innervated, avascular tissue that consists of epithelium, keratocytes, endothelium, and an extracellular matrix. We evaluated the effects of gene knockout (KO) of the TRPA1, a membrane cation channel potentially activated by various external stimuli, on the wound-healing process in corneal stroma following an incision injury in mice. TRPA1 protein was detected markedly in the corneal epithelium and cells in the stroma in a healthy, uninjured wild-type cornea. Deletion of TRPA1 gene function delayed wound closure of a full-thickness incision injury in the corneal stroma. Peak of the appearance of Sox10-positive (Schwann cell marker) and Sox2- or p75-expressing (both repair-type Schwann cell markers) cells in the healing stroma was at day 2 postincision injury in a wild-type mouse, but was delayed in a TRPA1-KO mouse during the healing process. Expression of TGFβ1 mRNA was suppressed, in association with a reduction in p-Smad3 expression in stromal cells, by TRPA1 gene deletion. We also observed that the loss of TRPA1 suppressed the appearance of myofibroblasts and expression of Col1a1 and fibronectin in the healing stroma. In vitro gel culture study showed that chemical TRPA1 inhibition attenuated TGFβ-induced fibroblast contractility. These results indicate that TRPA1 is involved in the process of corneal stromal wound healing in response to tissue laceration in mice. The phenotype was associated with the attenuation of the generation of repair Schwann cells, TGFβ signaling in stromal cells, keratocyte-myofibroblast transformation, and collagen-type I expression.