Induction of angiogenesis by growth factors: relevance to pancreatic islet transplantation

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Abstract
Biodegradable pellets releasing 20 ng/day of endothelial cell growth factor alpha (αECGF) or a- or b-fibroblast growth factor (FGF) and 90 μg/day of heparin were implanted beneath the renal capsule in rats and dogs and the muscularis/serosal border of the pyloric stomach in dogs to test for angiogenesis in a potential pancreatic islet transplant site. These factors were also tested in vitro to determine whether the capillary bed of the isolated islet could be preserved. αECGF was superior to a- or bFGF in promoting endothelial cell growth and capillary formation in isolated islets. Both a- or bFGF and αECGF induced the development of a dense capillary bed in the dog stomach, whereas in the kidney site αECGF was more effective in the rat than was a- or bFGF. Priming the isolated islet as well as the transplant site prior to islet transplantation resulted in islet blood flow being established within 3 days in contrast to 7–14 days in controls.