Differential expression of MT1-MMP (MMP-14) and collagenase III (MMP-13) genes in normal and wounded rat corneas

PURPOSE. Several members of the matrix metalloproteinase (MMP) group have b een identified in the rat cornea during corneal mound healing. The aim of t he present study was to identify additional members of the MMP gene family in the rat cornea and localize the expression of membrane type-1 matrix met alloproteinase (MT1-MMP; MMP-14) and collagenase III (MMP-13) in normal and wounded corneas. METHODS. Adult rats underwent laser keratectomy on the right eye. Unwounded left eyes were normal controls. Corneas were collected and processed at di fferent times post-wounding. Reverse transcription-polymerase chain reactio n (RT-PCR) and DNA sequencing were used to discover the MMP genes expressed in the corneas, In situ hybridization was performed to localize the mRNA e xpression of MMP-14 and MMP-13. RESULTS. MMP-13 mRNA was detected in epithelial cells of wounded corneas, b ut not in normal controls; MMP-14 was found in both normal and wounded corn eas, MMP-14 mRNA was expressed predominantly in the stromal keratocytes and rarely in the basal epithelial cells in normal and wounded corneas. MMP-13 mRNA was localized exclusively to basal cells of the epithelium at the wou nded area from 6 hours to 3 days after wounding. CONCLUSIONS. MMP-14 and MMP-13 expression in rat corneas parallels that of gelatinases A and B, respectively. MMP-13 may play an important role in the gelatinase B-associated proteolytic cascade that allows rapid turnover of the extracellular matrix (ECM) components during corneal wound healing. MMP -14 may contribute to removing abnormal ECM components through activation o f gelatinase A in rat corneas.