Abstract
Abstract: :
Purpose: Histological examination of experimental CNV in rabbits has demonstrated the presence of newly formed RPE-like cells in the subretinal space. It was the purpose of this study to characterize these cells regarding their origin, distribution and potential role in the development of CNV. Methods: Experimental CNV in D-B rabbits (n=10) was established by a single subretinal administration of a cocktail that contained 100 ng LPS and 100-ng bFGF. Subretinal hyper-pigmentation at the area of CNV was monitored for a period of one year by fundus photography and fluorescein angiography. Cell infiltration into the subretinal space was studied in a series of paraffin tissue sections with Hematoxylin and Eosin (H&E;) stain. Characterization of these cells utilized the methods of Fontana-Masson histological stain and HRP-AEC staining with the anti- macrophage antibody RAM11. Results: Clinically, subretinal hyper-pigmentation at the area of CNV can be observed in all 10 eyes by two weeks after administration of angiogenic molecules. The hyper-pigmentation lasted throughout the entire observation period. Histologically, large numbers of newly formed pigment cells were found in all of the 10 study eyes. These cells were located in the subretinal space, surrounding the choroidal neovascularization, and limited to the area formed by the bleb associated with the original subretinal injection. These newly formed pigment cells reacted positively with Fontana-Masson stain, which identifies melanin-associated cells. These cells also were RAM11 positive, a macrophage marker. In addition, the primary RPE cells had atrophied and it is suggested that these newly formed pigment cells may originate from primary RPE cells. Conclusions: Our data suggest that the growth and maintenance of rabbit CNV are characterized by atrophy of primary RPE cells and by the presence of secondary pigmented cells, which may be of RPE cell origin. These secondary RPE-like cells express macrophage markers and may contribute pro-angiogenic factors. Primary RPE and newly formed secondary RPE-like cells, through autocrine and/or paracrine cytokine pathways, may furnish a stimulus for new vessel formation and stabilization, similar to what is observed in the course of CNV in patients clinically.
Keywords: age-related macular degeneration • retinal pigment epithelium • choroid: neovascularization