Abstract
Abstract: :
Purpose: Early age related macular degeneration (ARMD) is characterized by atrophy of the choroid and the thickening of Bruch's membrane by the accumulation of extracellular matrix (ECM). These findings could be related to hypoxia of the outer retina and retinal pigment epithelium (RPE). One factor known to increase the formation of ECM is connective tissue growth factor (CTGF). Additional CTGF has been proposed to be involved in the angiogenesis. The enzyme plasminogen activator inhibitor–1 (PAI–1) inhibits the degradation of ECM. In the present study we investigated the effect of hypoxia on the expression of CTGF and PAI–1 in cultivated human RPE cells. Methods: The expression of CTGF and PAI–1 in native RPE cells of 6 donors was investigated by RT–PCR, northern–blot and western–blot analysis. Cultivated RPE cellsfrom 5 human donors of the third passage were:1. 4 – 12 hours under hypoxic conditions (1% O2) incubated 2. 1 – 16 hours re–oxygenated.The induction of CTGF and PAI–1 were quantified by using immunohistochemical staining, western–blot and northern–blot analysis. Results: Native RPE cells constitutively express CTGF and PAI–1. Hypoxia increases the expression of CTGF in cultivated RPE cells about the factor 2–3x. Following re–oxygenation there was an increase about 3–4x fold. Hypoxia increased the expression of the enzyme PAI–1 about the factor 3–4x, while the phase of re–oxygenation lead to a 5–6x fold increase. Conclusions: Local hypoxia in ARMD seems to induce the expression of CTGF and PAI–1 in the RPE. This cascade may play an important role in the observed early and late changes of ARMD like thickening of Bruch's membrane and formation of choroidal neovascularisations.
Keywords: age–related macular degeneration • retinal pigment epithelium • choroid: neovascularization