Effects and mechanisms of non-restrictive external stent for prevention of vein graft restenosis in a rabbit model.

BACKGROUND

Among various treatments preventing vein graft restenosis, external stent is receiving more and more attention. This study aimed to investigate the effect of non-restrictive external stent on the prevention of vein graft restenosis and the potential mechanisms of platelet-derived growth factor (PDGF) in the process of restenosis.

METHODS

Thirty-six "New Zealand white rabbits" were randomly divided into two groups, stented group (group S) and control group (non-stented group, group NS). Each rabbit underwent a reversed autologous external jugular vein into common carotid artery bypass grafting. In group S, the vein grafts were surrounded by a non restrictive stent which was 6 mm 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 the first week (1W), second week (2W) and fourth week (4W) after surgery respectively. 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 hyperplasia ratio was defined as the percentage of the area enclosed by the internal elastic lamina occupied by the intima.

RESULTS

At 1W, the difference of the thickness and area of the intima between groups S and NS was not significant (P > 0.05); at 2W and 4W, the thickness and area of the intima and the intimal hyperplasia ratio in group S were less significant 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). Immunocytochemistry staining of PDGF-B showed that the percentage of positive cells of intima in both two groups was peaked at 2W, and a significantly smaller percentage was detected in group S compared with that in group NS at 2W and 4W (P < 0.05); the percentage of PDGF-B positive cells of media in both two groups was also peaked at 2W, and that in group S was smaller than that in group NS from 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 adventitia in group NS peaked at 2W, and the percentage of adventitia in group S was greater than in group NS at 4W (P < 0.05).

CONCLUSIONS

Non-restrictive external stenting inhibits the hyperplasia of the intima and media of the vein grafts and reduces the thickness and area of the intima and media; Non-restrictive external stenting inhibits the synthesis of PDGF and changes its distribution, and then inhibits the hyperplasia of the intima.