Vasculotropin-VEGF stimulates retinal capillary endothelial cells through an autocrine pathway.

To determine whether bovine retinal endothelial cells (BRECs) bind, synthesize, and respond to vasculotropin-vascular endothelial growth factor (VAS-VEGF). Cultured BRECs were tested for their ability to bind 125I VAS-VEGF and their response to the growth and migration-promoting effect of VAS-VEGF. Total RNAs extracted from BRECs were reverse transcribed and amplified by polymerase chain reaction using VAS-VEGF primers. The translation was assessed by a Western blot analysis and a radioreceptor assay in the BREC-conditioned medium. Neutralization with anti-VAS-VEGF antibodies ascertained the autocrine role of VAS-VEGF. BRECs bind VAS-VEGF on two high-affinity binding sites (apparent Kd of 2 and 56 pM) and can proliferate and migrate upon the addition of recombinant VAS-VEGF. Furthermore, BRECs synthesize and secrete into their own culture medium a mitogen related to VAS-VEGF as far as two factors are concerned: chromatographic behavior on heparin-affinity columns, and cross-reactivity with recombinant VAS-VEGF to the binding to its receptors or antibodies. Neutralization of the purified conditioned medium with anti-VAS-VEGF antibodies revealed that VAS-VEGF can act on BRECs through an autocrine pathway. This is the first description of an autocrine regulation of endothelial cell growth by VAS-VEGF that could be involved in the pathogenesis of retinal neovascularization.