Transplantation of Amniotic Membrane in Murine Herpes Stromal Keratitis Modulates Matrix Metalloproteinases in the Cornea

Abstract

To study matrix metalloproteinases (MMP) and tissue inhibitors of metalloproteinases (TIMP) in the corneas from mice with ulcerative herpes stromal keratitis (HSK) treated with amniotic membrane transplantation (AMT). The corneas from BALB/c mice were infected with HSV-1. Mice with ulcerative HSK on postinfection (PI) day 14 were used for the experiments. In one group of mice, the corneas were treated with transplantation of amniotic membrane (AMT) that was secured with a tarsorrhaphy, and a control group underwent tarsorrhaphy alone. After 2 days, the appearance of corneal ulcers and stromal inflammation was judged clinically. Corneal sections were studied by immunohistochemistry for the expression of MMP-2, -8, and -9 and TIMP-1 and -2. MMP activity in the corneas was investigated by zymography, and the expression of the enzymes was measured by the Western blot technique. At day 14 PI, the ulcers stained intensely positive for MMP-2, -8, and -9 and TIMP-1 and -2. Ulceration (P < 0.001), stromal inflammation (P < 0.01) and inflammatory cell infiltration (P < 0.001) markedly improved by day 2 after AMT. This was associated with reduced expression (P < 0.01) and activity of MMP-8, and -9 and increased localization of TIMP-1 (P < 0.01), whereas TIMP-2 was not affected. In contrast, high levels of expression of MMP-8 and -9 remained in the cornea after tarsorrhaphy, and the TIMP-1 expression was only slightly upregulated. Rapid improvement of HSV-1-induced ulcerative keratitis is noted after amniotic membrane transplantation. This may be caused by reduced expression and activity of MMP-8 and -9, increased expression of TIMP-1, and sustained expression of TIMP-2.