Insulin and local growth factor PDGF induce intimal hyperplasia in bypass graft culture models of saphenous vein and internal mammary artery.

OBJECTIVE: In arteriosclerosis and bypass graft stenosis, intimal proliferation is controlled by local and systemic growth factors, such as platelet derived growth factor (PDGF) or insulin. Intimal hyperplasia can be produced in organ culture models. Our aim was to compare neointima formation in two organ culture models of internal mammary artery (IMA) and saphenous vein (SV), with special reference to the influence of systemic and local growth stimuli.
METHODS: Rings of freshly isolated human SV and IMA were cultured over a 3-, 6- or 8-day period. They were distributed into five groups of incubation protocols: incubation with 10% serum; insulin 50 ng/ml and 100 ng/ml; PDGF-BB 5 ng/ml and 10 ng/ml. Frozen sections of cultured rings and pre-culture segments were subjected to elastic stain and immunohistochemistry. Antibodies directed against beta-actin and smooth muscle alpha-actin were used to characterize smooth muscle cell phenotype and against proliferating cell nuclear antigen (PCNA) to demonstrate proliferating cells.
RESULTS: Growth factor incubation caused massive intimal hyperplasia with increased elastic fibers in SV and intimal smooth muscle cell as well as matrix accumulation in IMA. Intimal thickening, PCNA and beta-actin expression reached their maximum on day 6 of culture. In both culture models, serum, insulin and PDGF caused increasing intimal thickening, with more pronounced effects in SV.
CONCLUSIONS: These organ culture models demonstrate the effects of insulin and PDGF on intimal hyperplasia in IMA and SV representing models for arteriosclerosis and bypass graft stenosis and stressing the role of insulin and growth factors for neointima development.