Expression of matrix metalloproteinases in experimental herpes simplex virus keratitis

Abstract

To determine the distribution and activities of matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) during the course of experimental herpes simplex virus type-1 (HSV-1) keratitis. Keratitis was induced in BALB/c mice by inoculating the cornea with 10(5) plaque-forming units (pfu) of HSV-1 (KOS strain). Corneas were harvested at days 0, 2, 7, 14 and 28 post-infection. Expression of MMP-2, MMP-9, MMP-8, TIMP-1 and TIMP-2 were detected by immunohistochemistry and Western blot. The enzymatic activities were analyzed by Zymography. At day 2 post-infection, MMP-2 and MMP-9 expression were increased in the epithelium as compared to the uninfected control eyes, and were detected in the superficial stroma and in inflammatory cells beneath the epithelium. Similar staining patterns were detected for TIMP-1 and TIMP-2. MMP-2 and MMP-9 epithelial staining persisted until day 28 post-infection. Necrotizing keratitis with corneal ulceration was present on days 14 and 28 post-infection. This correlated with increased expression of MMP-2 and MMP-9 within the stroma and in infiltrating inflammatory cells. MMP-2, MMP-9, TIMP-1 and TIMP-2 staining were particularly intense in the proximity of the ulcers. The neutrophils, which were abundant at the site of ulceration, were stained positive with MMP-8. Both gelatinolytic activities and caseinolytic activities were upregulated after HSV-1 corneal infection. Our data suggest that MMPs produced by resident corneal cells and by inflammatory cells possibly promote epithelial keratitis and ulcerative process after corneal HSV-1 infection. The interaction of MMPs and TIMPs may regulate the course of necrotizing HSV keratitis.