Proliferative vitreo-retinal disorders: experimental models in vivo and in vitro

The aim of the present thesis was to develop, refine, and assess experimental models for the study of proliferative vitreo-retinal disorders. An intravitreal injection of a colloidal solution of microparticles was used in the primate eye to produce pathologic changes including intraocular cell invasion, cell proliferation, neovascularization, collagen synthesis, and tractional retinal detachment. In a separate primate model for laser-induced subretinal neovascularization, the origin and the occurrence of macrophages was evaluated. Examinations were performed using ophthalmoscopy, slit-lamp microscopy, light microscopy, and transmission electron microscopy. Cell cultures were employed to study the effects of vitreous humor and macrophages on the proliferation of cultured retinal pigment epithelial (RPE) cells and cultured fibroblasts using a Coulter counter. Morphologic changes were documented by phase micrography. A quantitative estimation of the extracellular matrix deposition of fibrous proteins by macrophage-modulated RPE cells as well as by vitreous-modulated RPE cells was done using enzymatic digestion and radioactive labeling techniques. A qualitative analysis of the types of collagen that was deposited in the extracellular matrices by vitreous modulated cultures was also made using indirect immunofluorescence. Using a newly developed RPE cell specific monoclonal antibody, the avidin-biotin-peroxidase labeling technique was finally employed to test the phenotypic epitope expression of macrophage-modulated and non-modulated RPE cells. A new experimental in vivo model for pathologic changes that characterize proliferative vitreo-retinal disorders was developed in the primate eye. In the model for laser-induced subretinal neovascularization, macrophages were shown to be principally recruited from the systemic circulation. Using cell cultures, it was found that both macrophage-conditioned medium and vitreous humor, separately or combined, exert mitogenic effects on RPE cells and fibroblasts. The combined effect of the two stimuli was additive, but not synergistic, on both cell lines. When incubated with macrophage-conditioned culture medium or vitreous humor, RPE cells exhibited a metaplastic transformation towards fusiform, spindle-shaped cells that were morphologically indistinguishable from fibroblasts. The extracellular matrices of RPE cells modulated by macrophage-conditioned medium also appeared converted to a more striated pattern as compared to non-modulated controls. The metaplastic transformation of cultured RPE cells reverted when experimental stimuli, macrophage-conditioned medium or vitreous humor, were withdrawn. A new in vitro method for evaluating fibrous protein deposition in the extracellular matrix by RPE cells was also described. RPE cells, that were modulated by macrophage-conditioned medium or vitreous humor, deposited less fibrous proteins per cell.(ABSTRACT TRUNCATED AT 400 WORDS)