Expression of Matrix Metalloproteinases (MMP)-12 by Myofibroblasts during Alkali-Burned Corneal Wound Healing

PURPOSE: The purpose of this study was to determine the expression of MMP-12 by myofibroblasts during the healing of alkali-burned rabbit corneas (ARC), thus implicating its role in ECM remodeling. METHODS: Rabbit corneas during alkali burn were examined for MMP-12 mRNA expression by RT-PCR. Immunohistochemistry was used to determine the presence of alpha-SMA, MMP-12 protein, and macrophages. In situ hybridization was performed to identify MMP-12 mRNA expressing cells. RESULTS: RT-PCR showed that MMP-12 mRNA was expressed in the alkali-burned corneas from one week after the injury. Immunohistochemistry showed myofibroblasts positive for MMP-12 expression. In situ hybridization revealed that MMP-12 mRNA was expressed by myofibroblasts. CONCLUSION: Our results indicate that, in alkali-burned corneas, myofibroblasts express both MMP-12 mRNA and protein. We suggest that MMP-12 may disintegrate some components of the ECM released after severe alkali burn, which may be involved in the ECM remodeling.