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Jian Hua Qi, Heidi Stoehr, Bela Anand-Apte; Sorsby Fundus Dystrophy S156C-TIMP3 mutation promotes angiogenesis and choroidal neovascularization via a FGF receptor-1 signaling pathway. Invest. Ophthalmol. Vis. Sci. 2014;55(13):1192.
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© ARVO (1962-2015); The Authors (2016-present)
Sorsby Fundus Dystrophy (SFD), an inherited, early onset macular degenerative disorder with choroidal neovascularization (CNV) which closely resembles age-related macular degeneration (AMD) is caused by mutations in the TIMP3 gene. The objective of this study was to investigate the mechanism by which SFD-related S156C-TIMP3 mutation promotes angiogenesis or CNV.
In vitro angiogenesis was induced by FGF, VEGF or the conditioned medium (CM) from human retinal pigment epithelial (RPE) cells expressing wild-type (WT), S156C-TIMP3 or empty vector, and analyzed for tube formation and/or cell proliferation. The laser-induced CNV responses in Timp3 S156C/S156C knock-in mice and their corresponding WT littermates were quantitated. VEGFR-2 ,FGFR-1 tyrosine phosphorylation and MAP kinase phosphorylation in ECs or the RPE-choroid tissue following ligand stimulation or laser treatment were analyzed by Western blots.
The expression of S156C-TIMP3 in RPE cells exhibited increased glycosylation and decreased MMP inhibitory activity of the mutant protein. Increased levels of bFGF and Heparan Sulfate (HS) but not VEGF were observed in the CM of mutant cells. The CM from mutant RPE cells induced increased tube formation in PAE/FGFR-1 cells with a bFGF dependency. Proliferation, tube formation, FGFR-2 tyrosine phosphorylation and MAP kinase activation were increased in mouse aortic endothelial cells from either heterozygous TIMP3+/S156 or homozygous TIMP3S156C/S156C following bFGF stimulation relative to WT control cells. Consistent with the results from in vitro experiments, Timp3 S156C/S156C mice showed increased glycosylation and reduced MMP inhibitory activity of mutant protein, increased tyrosine phosphorylation of FGFR-2 and increased MAP kinase activation in RPE-choroids after a laser burn. Furthermore, at 2 weeks post-laser induction, the area of CNV at Bruch’s membrane (BM) rupture sites was observed to be significantly larger in mutant mice compared to their WT controls.
S156C-TIMP3 may up-regulate angiogenesis and CNV by increasing bFGF-FGFR-2 signaling.
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