Adaptive remodelling of smooth muscle in the neo-intima of vein-to-artery grafts in rats: a detailed morphometric analysis.

End-to-end autogenous vein-to-artery grafts in rats have been used extensively as a model for neointimal thickening (hyperplasia), which develops over the first 6 weeks after grafting. This study employed computerised morphometric techniques to analyse 16 grafts, in order to quantitate precisely how the neointima develops. Two important features were described that have not been identified previously, due to the extensive variation in neo-intimal thickness inherent in vein grafts. Firstly, the proximal region of the graft was significantly thicker than the distal region, up until 6 months after grafting. The smooth muscle cells in the graft may have developed more rapidly in the proximal region, due to the altered haemodynamics within the graft. Secondly, within the central region of the graft the characteristic focal nature of neo-intimal hyperplasia was evident throughout the period of the study, but by 6 months the neo-intima tended to be distributed more evenly. By 6 months remodelling of smooth muscle throughout the graft neo-intima had occurred, and the neo-intima had matured to a thickness equivalent to that of the intima plus media of the adjacent iliac artery.