Prevention of smooth muscle cell phenotypic modulation in vein grafts: a histomorphometric study

This is a prospective study of the relationship between graft preparation technique and the subsequent morphologic fate of vein grafts. Paired vein grafts (optimal vs injury prepared) were placed in a canine model and removed over time. Vein grafts intentionally injured by warm saline storage demonstrated endothelial and smooth muscle cell damage. In the acute postimplantation period, platelet adhesion and white cell infiltration of the graft were present. By 7 days, the endothelium had "healed", but the underlying smooth muscle cells had modulated and were of the transitional or synthetic phenotype. This persisted at 30 days, but by 60 days the graft wall had remodeled to a contractile smooth muscle cell phenotype. Changes in the extracellular matrix were greatest at 30 days corresponding to changes in the smooth muscle cell phenotype. None of these injurious responses were noted in optimally prepared, papaverine treated vein grafts. The combined intima and media (lumen to adventitial edge) was measured at baseline and at graft excision with use of digitized graphic techniques. The intimal/medial thickness of injured vein graft walls was always greater than that of pair-matched optimally treated vein grafts (p less than 0.01 analysis of variance). Optimal preparation of vein grafts is effective in minimizing endothelial and smooth muscle cell injury at the time of arterial reconstruction. This preservation of endothelial and smooth muscle cell integrity prevents subsequent morphologic changes associated with the "arterialization response".