Presence of endothelial cell growth factor activity in normal and diabetic eyes

Two classes of growth factors affecting endothelial cell proliferation have been found previously in ocular tissues: a heat labile mitogen from retina (RDGF) and a heat stable inhibitor of proliferation from vitreous. The relative amounts of these growth factors in normal and diabetic cadaver eyes were investigated using fetal bovine aortic endothelial cell proliferation as an assay. Equivalent levels of RDGF activity were extracted from diabetic and normal sensory retinas. An extract from pigment epithelium and choroid was found to have similar levels of mitogenic activity, but this activity was not as heat labile as RDGF. Like RDGF, equivalent amounts of mitogen were extracted from diabetic and normal tissue. Normal human vitreous inhibited endothelial cell proliferation, and this activity was enhanced by heating the material (10 min., 95 degrees C). Four of the five individual diabetic vitreous samples of identical postmortem times were mitogenic when not heated, and exhibited little or no inhibitory activity when heated. Vitreous of identical postmortem times was pooled and fractionated by heparin-Sepharose chromatography to determine if the heat labile mitogen in vitreous was RDGF. From the insulin-dependent diabetic (IDDM) pooled vitreous sample, a prominent protein of 18 Kd was eluted from the column with 1.2 M NaC1, a characteristic of RDGF. This work suggests that both RDGF and the vitreous inhibitor are found in human vitreous, but their relative concentrations may change in the diabetic state so that retinal neovascularization from retina can occur.