Possible mechanism of endothelial progenitor cells in the development of rat choroidal neovascularization

Abstract

To investigate the role and possible mechanism of endothelial progenitor cell (EPC) in the development of choroidal neovascularization (CNV). Experimental study. Twenty-four BN rats were divided into 3 groups.One eye of each animal was induced by laser photocoagulation with 532 nm laser and the contralateral eye was taken as control. Three, seven and fourteen days after photocoagulation the formation of CNV was observed by histopathological study and the recruitment of EPC and the possible pro-angiogenic growth factors released by EPC during the development of CNV were examined by multi-labeled immunofluorescence staining. The difference among the 3 groups was analyzed by ANOVA and the comparison between any 2 groups was further checked by LSD-t test. Both the histopathological study and the immunofluorescence staining indicated that within the laser lesions proliferated and migrated cells grew into the subretinal space through the broken Bruch membrane 3 days after photocoagulation, 7 days after photocoagulation lumen-like structures were observed and CNV became stable until 14 days after photocoagulation. No EPC was observed in the normal retina whereas EPC were recruited into the laser lesions 3 days after photocoagulation, comprising (79.29 ± 11.27)% of the total endothelial cell population within CNV. At 7-day EPC constituted new vessels within CNV area and the proportion decreased to (47.13 ± 5.78)%. Then its number decreased dramatically 14 days after photocoagulation contributing to (10.83 ± 2.79)% of the endothelial cells in CNV. The differences either among the 3 groups (F = 104.623, P < 0.05) or between any 2 groups (P < 0.05) were statistically significant. Moreover, triple labelled immunofluorescence staining showed that the EPC within CNV area could also secret pro-angiogenic factors such as vascular endothelial growth factor, IL-10, bFGF and MMP9. EPC involves in the development of CNV not only through participating in the formation of new vessels within the CNV area but also through secreting pro-angiogenic factors.