| Objective: Autologous saphenous vein continues to be one of the most commonly used conduits for coronary artery bypass graft surgery, however the long-term clinical success of the procedure is limited by the late graft failure due to neointima formation and progressive thickening. External-stenting of vein grafts is a promising approach to prevent neointima hyperplasia and wall thickness of the vein grafts. In the present study, we investigated the effect and the potential mechanisms of non-restrictive external stent to prevent neointima hyperplasia and cell proliferation of vein grafts and the influence of non restrictive external stent on expression of platelet-derived growth factor (PDGF) which is a potent mediator of vascular smooth muscle cell(VSMC).Material and methods: Thirty-six "New Zealand white rabbit" were randomly divided into two groups, stenting group (group S) and control group (non-stenting group, group NS). Each rabbit underwent a reversed autologous external jugular vein into common carotid artery bypass grafting. In group S, the vein graft were surrounded by a non restrictive stent which was 6mm in diameter (a kind of Dacron vascular prosthesis); and in group NS, there was no stent to support the vein grafts. The grafts were harvested at lweek(1W), 2weeks(2W), 4weeks(4W) after surgery, respectively. Color Doppler ultrasonography was applied to test the patency of the grafts. The sections were stained with hematoxylin and eosin stain and elastic van Gieson's stain, and examined under a light microscope. The dimensions(including the thickness and area of the intima and media, luminal area) were measured by computer-aided image analysis system, and the intimal encroachment was defined as the percentage of the area enclosed by the internal elastic lamina occupied by the intima. Sections were also stained with a-smooth muscle actin(a-SMA) and proliferating cell nuclear antigen (PCNA) immunocytochemistry stain to identify the VSMC and judge the cell proliferation of the vein grafts. PCNA index was calculated as the percentage of positive cells among the total number cells in a microscopic field with x400 magnified in intima, media and adventitia, respectively. Imrnunohistochemistryand reverse transcription-polymerase chain reaction (RT-PCR) technique were employed to investigate the expression of PDGF in vein grafts. The percentage of PDGF immunocytochemistry stain positive cells were also calculated in intima, media and adventitia, respectively; and total RNA of whole wall of the vein grafts were extracted and performed RT-PCR.Results: (l)One rabbit died before harvest and one rabbit developed occlusive thrombus in group S, and the material like the"jelly" (neoadventitia) occupied the space between the grafts and the stents. Hemiplegia occurred in one rabbit and the rabbit died before harvest, and non-occlusive thrombus formed in one graft in group NS. The results of Color Doppler ultrasonography were in accordance with the findings of harvest. (2)HE stain: intima and media of vein grafts proliferated in both group S and NS gradually from 1W to 4W, and the neoadventitia in group S was formed with granulation, and many inflammatory cells aggregated in it. (3)Computer-aided image analysis system study: from 1W to 4W, the thickness and area of the intiam and media were increased gradually. At 1W, the difference of the thickness and area of the intiam and the intimal encroachment between group S and NS were no significance, P>0.05; at 2W, 4W, the thickness and area of the intiam in group S were smaller than those in group NS, P < 0.05; from 1W to 4W, the thickness and area of the media in group S were smaller than those in group NS, P<0.05. (4)PCNA index: the index of intima in both two groups were peaked at 2 W, and the index of intima in group S was less than in group NS at 2 W and 4W, P<0.05; the index of media in both two groups were peaked at 1W, and the index of media in group S was less than in group NS fron 1W to 4W, P<0.05; the index of adventitia in both two groups were peaked at 2W, and the index of adventitia in group S was greater than in group NS at 2W and 4W, P<0.05. (5)Immunocytochemistry stain of PDGF-B: the percentage of positive cells of intima in both two groups were peaked at 2W, and a significantly smaller percentage were detected in group S compared with in group NS at 2W and 4W, P <0.05; and the percentage of PDGF-B positive cells of media in both two groups were also peaked at 2 W, and the percentage of media in group S was smaller than in group NS fron 1W to 4W, P<0.05; and the percentage of PDGF-B positive cells of adventitia in group S was peaked at 4W, whereas the percentage of...
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