Important role of epiregulin in inflammatory responses during corneal epithelial wound healing

To investigate the role played by epiregulin in corneal epithelial wound healing in vivo in epiregulin-knockout (KO) mice and cultured mouse corneal epithelial cells (MCECs).

A 2-mm diameter central epithelial wound was created in epiregulin-KO and wild-type (WT) mouse corneas. The size of the unhealed area and the epithelial cell proliferation and migration were examined. Myeloperoxidase assay was performed to determine the number of polymorphonuclear (PMN) cells infiltrating corneal stroma. Real-time PCR was used to determine expression of the mRNA of inflammatory cytokines in the corneal epithelial cells. Expression of chemokine (C-X-C motif) ligand 2 (CXCL2) response to IL-1β was examined in MCECs with or without recombinant mouse epiregulin. Repetitive injuries were created to determine the effect of inflammation in healing in epiregulin-KO mice.

After a single injury, corneal epithelial wound healing and cell migration and proliferation were unimpaired. However, corneal opacities and a larger number of infiltrating PMN cells were observed in epiregulin-KO mice. Expression levels of IL-1β, IL-6, CXCL1, and CXCL2 were higher in epiregulin-KO than in WT corneal epithelia cells. The addition of epiregulin significantly reduced the expression of CXCL2 in response to IL-1β in MCECs. In response to repetitive injuries, a significant delay in healing and more severe opacities were observed in epiregulin-KO mice than in WT mice.

Our results indicate that during wound healing, epiregulin may regulate the expression of cytokines and chemokines to reduce an excessive accumulation of PMN cells, which will cause corneal opacity and persistent epithelial defects.