Expression of Endoglin in Choroidal Neovascularization and Human Eyes

Abstract

Abstract: : Purpose: Endoglin (CD105) is a membrane protein involved in the TGF-ß receptor signalling pathway. Its predominant expression in proliferating endothelial cells lead to the assumption, that this protein could serve in drug targeting of neovascularization. The aim of this study is to analyze the expression of CD105 in choroidal neovascularization membranes (CNVMs) and in human eyes and to compare it to the proliferative status of CNVMs. Methods: Thirty surgically excised CNVMs, secondary to age-related macular degeneration (AMD), were investigated by light microscopic immunohistochemistry and confocal immunofluorescence microscopy using verified antibodies to the endothelial cell markers CD105, von Willebrand factor (vWF) and CD34 and the proliferation marker Ki-67. Results: A selective expression of CD34 and vWF as well as CD105 was found in endothelial cells. CD105 expression was elevated in vascular endothelial cells within CNVMs, but a moderate CD105 expression could also be found in quiescent CD34 and vWF positive ocular vasculature. Ki-67 positive cells could be detected in CNVMs, but these were rarely endothelial cells. Conclusions: Endoglin expression in endothelial cells of CNVMs is increased, but rarely associated with a concomitant expression of the proliferation marker Ki-67. The elevated expression of CD105 in this neovascular tissue suggests a persisting post-mitotic activation. The modest but consistent expression of endoglin in physiologic non-proliferating vasculature may, however, exclude this protein from drug targeting.

Keywords: age-related macular degeneration • choroid: neovascularization • microscopy: light/fluorescence/immunohistochem