Purpose: Glaucomatous optic neuropathy involves tissue remodeling by matrix metalloproteinases (MMPs). In this study we investigated MMP gene expression in circulating leukocytes isolated from normal tension glaucoma (NTG) patients in comparison to healthy controls.
Methods: Blood samples were collected from 6 glaucoma patients and 6 age- and sex-matched healthy controls. Leukocytes were separated using Ficoll-Hypaque gradient. mRNA pools were used for subtractive hybridization to identify genes with altered expression. The subtracted genes were sequenced and individual mRNA pools were quantified using semiquantitative RT-PCRs. Target PCR products were confirmed using sequence-based restriction analysis. In this study we focused on MMPs.
Results: MMP-9 and MT1-MMP (MMP-14) were subtracted as upregulated genes in the group of NTG patients. Upregulation of these genes was confirmed by RT-PCR and Western-blot analysis in all 6 patients. The expression of the tissue inhibitor of matrix metalloproteinases TIMP-1 was slightly enhanced in patients as compared with controls. Expression of MMP-2 was not detected in leukocytes either in glaucoma patients or in healthy subjects.
Conclusion: A simultaneous upregulation of both MMP-9 and MT1-MMP gene expression and only slightly enhanced expression of TIMP-1 suggest an increased enzymatic matrix metalloproteinase activity delivered by mononuclear blood cells in these patients.