Does the method of harvesting the saphenous vein for coronary artery bypass surgery affect venous smooth muscle cells? iNOS immunolabelling and ultrastructural findings

ObjectivesCoronary artery bypass surgery (CABG) using conventionally harvested saphenous vein (SV) as a graft is characterised by a high graft failure rate. It is believed that vein handling during harvesting is responsible for this, as damage to the vein's structure including its sources of endothelial nitric oxide synthase (eNOS) is apparent. Here we investigated the distribution of inducible nitric oxide synthase (iNOS) in conventionally harvested SV grafts and grafts prepared by a less-invasive ‘no-touch’ technique for CABG. Focus was on vascular smooth muscle cells (VSMCs).Patients and methodsSix patients undergoing CABG were selected for the study; their SVs were harvested as grafts by conventional and ‘no-touch’ techniques and subsequently examined using fluorescent and transmission electron microscopy combined with immunolabelling to detect iNOS and structural changes in the grafts at the time of implantation.ResultsThe following were observed in conventionally harvested grafts: (i) damage to the VSMCs and (ii) induction of iNOS in these cells, (iii) heterogeneity of VSMCs—the presence of iNOS-positive and iNOS-negative VSMCs which were also (iv) in close contact with each other. In contrast, no damage to VSMCs and no expression of iNOS in these cells were observed in the ‘no-touch’ SV preparations.ConclusionsThe harvesting procedure influences the structure of VSMCs and the expression of iNOS in SV graft at the time of implantation. Whether rapid stimulation of iNOS in VSMCs in conventional SV grafts has a protective or harmful effect on the graft patency remains to be determined.