Abstract
Abstract: :
Purpose: Recent evidence suggests that vasculogenesis as well as angiogenesis occurs during vessel formation in wound repair throughout the body. The recruitment of circulating stem cells is a key feature of vasculogenesis. The purpose of this study was to immunohistochemically determine whether markers of hematopoietic stem cells are present in choroidal neovascular membranes. Methods: Choroidal neovascular membranes were surgically removed from patients with age-related macular degeneration (n=8). All membranes were fixed in formalin, embedded in wax and serially sectioned for histochemical and immunohistochemical evaluation. Monoclonal antibodies against cell markers for AC133-1 and AC133-2 a human antigen recently identified as endothelial progenitor cell marker absent on mature endothelium; endothelial cell markers CD31, CD34 and von Willebrand factor, as well as for other cell types known to be found within CNV membranes such as RPE (cytokeratins) and macrophages (CD68). Secondary antibody amplification was with Dako Envision and visualised with nova red substrate. Results: Histochemical evaluation revealed the presence of an avascular fibrous stromal "core" in all the specimens. In this region, the predominant cellular immunoreactivity was for CD68 and cytokeratin, indicating the presence of RPE cells and/or macrophages. Conversely, the central stroma was devoid of endothelial cells in two of the CNV membranes and, in the remaining specimens, less than twenty percent of the cells were immunoreactive for endothelial markers. The peripheral area surrounding the fibrous core was highly vascular and showed varying immunoreactivity for all endothelial markers tested. Greatest immunoreactivity was observed with CD34 and von Willebrand factor and least for CD31 and AC133. The AC133 labelling was diffuse throughout cells. Macrophages and/or RPE cells were also present between the vessels. Conclusions: CNV membranes contain endothelial cells, which are immunoreactive for various markers of endothelial cell differentiation. The finding indicates that CNVs contain endothelial cells in different stages of differentiation from endothelial progenitor cells to mature endothelial cells and supports the suggestion of a possible role for vasculogenesis as well as angiogenesis during CNV pathogenesis.
Keywords: age-related macular degeneration • choroid: neovascularization • pathology: human