Insulin-like growth factor I (IGF-I) receptor/binding protein in human diabetic epiretinal membranes

Insulin-like growth factor I (IGF-I) is thought to play a role in the development of proliferative diabetic retinopathy. Proliferative diabetic retinopathy is characterised by the formation of fibrovascular epiretinal membranes, and IGF-I may initiate and/or potentiate this epiretinal proliferation. To evaluate further the part played by IGF-I in the development of epiretinal tissue, we investigated the presence of IGF-I receptor/binding protein in proliferating diabetic fibrovascular epiretinal membranes. Five fibrovascular epiretinal membranes were obtained by vitrectomy from five patients with proliferating diabetic retinopathy. The presence of IGF-I receptors was investigated by autoradiography using 125I-labeled IGF-I on frozen sections. To characterise binding specificity, some sections were preincubated with either insulin or unlabeled IGF-I. Sections of post-mortem liver were used as controls. Strong labeling of cells with 125I-labeled IGF-I was observed in all epiretinal membranes and in liver cells. Almost no autoradiographic labeling was observed in sections that had been blocked with non-radioactive IGF-I, and very little labeling was found following blockage with insulin. Our preliminary study suggests the presence of IGF-I receptor/binding protein in human diabetic epiretinal membranes. These results support the hypothesis that IGF-I may be involved in the formation of proliferative diabetic membranes.