Abstract
Abstract: :
Purpose: Choroidal neovascularization (CNV) represents the leading cause of vision loss in elderly patients with AMD. While the exact etiology and pathogenesis of abnormal neovascularization remains unclear, we have recently shown that post–natal vasculogenic pathways involving endothelial progenitor cells (EPCs) can contribute to some forms of CNV. However, the exact source of these cells has not been determined. Our aim in this study is to identify the origin of EPCs during neovascularization. Methods: We have used a modified chick CAM assay system in which we induced CAM angiogenesis in 10–day old embryos with different factors including bFGF, VEGF, and IGF–II. Bone marrow (BM) cells, BM cell subpopulations including lineage negative and CD11b+, peripheral blood mononuclear cells (PBMC), and spleen cells were isolated from C57BL/6 mice over–expressing EGFP under the ß–actin promoter and xenotransplanted directly into CAM vasculature. Human umbilical vein endothelial cells (HUVEC) labeled with the fluorescent dye PKH26 were also used. Cells were visualized by fluorescent microscopy for their localization in neovascular areas. Results: We have found that only total BM derived cells appear to co–localize in the newly vascularized bFGF areas but not in areas induced by VEGF. Interestingly, the lineage negative BM subpopulation, in which >30% of the cells express the presumptive EPC marker CD34, does not co–localize in this area. To rule out the role of circulating EPCs present in BM, we excluded this cell population and found no effect in our results. PBMC and cells derived from the spleen were not found in angiogenic sites whereas preliminary results showed that HUVEC can localize to these sites. Conclusions: We have developed a new system for rapidly screening various cell populations that could potentially contribute to new blood vessel formation. This system is simple to implement and results can be obtained within 3 days after xenotransplantation. Furthermore, only total BM cells can localize to the angiogenic area. We are presently examining which BM cell subpopulations home to newly vascularized areas and which cell markers they express.
Keywords: neovascularization • vascular cells • choroid: neovascularization