The Expression of Tissue Factor in Eyes With Age-Related Macular Degeneration

Abstract

Purpose: : Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly in the Western world. The wet and dry forms of AMD are characterized by choroidal neovascularization and geographic atrophy, respectively. Tissue factor (TF), the primary initiator of blood coagulation, regulates the production of vascular endothelial growth factor (VEGF), which promotes angiogenesis. Previous studies reported selective expression of TF on endothelial cells of AMD subretinal membranes. In this study, we examined TF expression in human AMD eyes, as well as in the eyes of Ccl2^-/-/Cx3cr1^-/- mice (DKO), a murine AMD model.Methods and Materials: Four paraffin-embedded slides of tissues from eyes of patients with AMD (two dry and two wet AMD) and two age-matched normal eyes were examined by immunohistochemsitry (IHC) using the avidin-biotin-immunoperoxidase method with a mouse monoclonal anti-TF antibody [human; American Diagnostica Inc. (ADI)]. Retinal cells including RPE were microdissected from the maculae to quantitate TF mRNA transcript using RQ-PCR. Frozen eye sections, isolated RPE, and neuroretina of DKOas well as age-matched wild type (WT) mice were sampled to determine TF antigen expression in situ by IHC [polyclonal anti-TF antibody (mouse; ADI)] and mRNA by RQ-PCR. Cultured RPE cells were obtained from both WT and DKO mice and evaluated for TF expression using IHC and RQ-PCR.

Results: : IHC showed enhanced TF expression in both dry and wet AMD lesions as compared to the controls. RQ-PCR result indicated a twofold increase of TF transcripts in dry AMD and a 32-fold increase in wet AMD compared to normal maculae. IHC on frozen sections of mouse eyes and cultured RPE cells demonstrated moderately higher TF expression in DKO than WT. RQ-PCR showed 1.8 times higher TF expression in microdissected retinal lesions and 1.4-fold increase in RPE cells of DKO compared to WT. RQ-PCR on whole retinal tissue indicated that the TF expression level was higher in DKO mice and increased with age in both WT and DKO mice.

Keywords: age-related macular degeneration • retinal pigment epithelium • neovascularization