Effects of MMP12 on cell motility and inflammation during corneal epithelial repair

Corneal epithelial defects are a common cause of ocular morbidity and can result in corneal scarring if they do not heal properly. Matrix metalloproteinases (MMPs) are extracellular matrix proteinases that regulate multiple aspects of corneal repair. We have previously shown that MMP12 has a protective effect on corneal fibrosis through its regulation of neutrophil and macrophage infiltration and angiogenesis in a chemical injury model involving full thickness damage to the cornea. However, the role of MMP12 in injuries limited to the corneal epithelium is relatively unknown. This study investigates the reparative effects of MMP12 following isolated corneal epithelial injury. Using a corneal epithelial debridement injury model performed on corneas of wild-type (WT) mice, we show that Mmp12 is expressed early following corneal epithelial injury with highest expression levels at 8 h after injury and lower expression levels at 4 and 8 days after injury. We investigated whether MMP12 has an effect on the rate of epithelial repair and cell migration using in vivo and in vitro scratch assays performed on WT and Mmp12^-/- mice. We found that loss of MMP12 results in a slower scratch wound repair rate both in vivo and in vitro. We also found that corneas of Mmp12^-/- mice have decreased neutrophil infiltration following injury. Loss of MMP12, however, does not affect cell proliferation in the center of the wounds. These data support a role of MMP12 in promoting early repair processes following corneal epithelial injury by enhancing epithelial cell migration and neutrophil infiltration.