Restenosis in human vein bypass grafts.

The restenosis rate in vein bypass grafts is higher than in native coronary arteries, and both the cascade of regulatory factors and the vessel reaction may be altered. In this study, vein bypass atherectomy specimens were classified as primary (n = 10) or restenotic (n = 12). Immunohistochemistry with 11 primary antibodies showed low levels of proliferation in both tissues and similar amounts of extracellular matrix components in both primary and restenotic specimens at the time points at which tissue was removed for clinical reasons. Inflammation appeared increased in restenotic specimens. Using in situ hybridization, transforming growth factor-beta1 messenger RNA was detected in both primary and restenotic tissue, with a trend to higher expression in restenosis (8.4 +/- 5.3 vs. 9.4 +/- 7.4 grains/nucleus) and further increased expression in multiple compared with single restenoses (15.1 +/- 6.1 vs. 5.6 +/- 5.1 grains/nucleus, P < 0.05). Hence, there were no great differences in cell proliferation or extracellular matrix formation between primary and restenosis vein graft tissue, in contrast to previously described findings in arterial tissue. This suggests that primary vein graft tissue is already in a chronic 'restenosis-like' state and subsequent injury creates minimal additional upregulation.