Validation of an in vitro model of human saphenous vein hyperplasia.

OBJECTIVE: The purpose of this study was the validation of the physiologic appropriateness of in vitro organ culture of human saphenous vein as a model with the demonstration of the occurrence of the processes of cell proliferation, remodeling, and hyperplasia.
METHODS: Saphenous vein from 28 patients was cross-sectioned into seven 2-mm segments and maintained in organ culture for 2 days or 2 weeks. Three organ culture media were used: a chemically well-defined medium (RPMI-1640) and the same medium supplemented with the undefined protein-containing supplements fetal bovine serum (FBS) or pooled adult human plasma (type AB). The outcome measures at 2 days and 2 weeks were compared with measurements of segments from the same vein at the time of harvest. Excess saphenous vein harvested for arterial bypass grafting was obtained after approval of the study protocol by the Institutional Review Board. Cell proliferation was measured with immunostaining for proliferating cell nuclear antigen. Remodeling and intimal hyperplasia were measured with micromorphometric comparisons of vein segment cross-sectional area before and after organ culture.
RESULTS: There was no evidence of cell death or tissue degeneration on histologic examination of the cultured vein segments. Cell proliferation, expressed as proliferation index (PI; positive proliferating cell nuclear antigen nuclei/total nuclei), significantly increased as compared with freshly harvested vein after 2 days of culture in undefined, protein-supplemented media (mean PI, 42.4 +/- 7.4%; P <.001). A significant increase in cell proliferation did not occur in the defined, unsupplemented medium until 2 weeks (mean PI, 16.2 +/- 7.1%; P <.001). The cross-sectional area of the vein wall increased during culture in all media. A statistically significant increase in the cross-sectional area of the vein wall occurred during culture with plasma (P <.001) and FBS supplementation (P =.002). The increase in the cross-sectional area of the vein in defined media was almost statistically significant (P =.089). A significant increase was seen in the cross-sectional area of the media (P =.006) and adventitia (P =.030) of veins cultured with plasma supplementation and in the cross-sectional area of the adventitia (P =.034) of veins cultured with FBS supplementation.
CONCLUSION: These results show that human saphenous vein in culture is viable, shows cell proliferation, and exhibits remodeling of the layers of the vein wall. This is the first report to document hyperplasia in human vascular tissue cultured in a defined medium.