| Objective: To observe the effects of endovascular brachytherapy with 32P liquid filled ballon on the apoptosis of vascular smooth muscle cell(VSMC) and the dose-effect ralation.To discuss the possible mechainismas of radiation in the prevention of vascular restenosis.Methods: After ballon endothelial injury of double iliac arteries and six weeks cholesterol-fed in 24 rabbits,the double iliac atherosclerotic steosis model was set up.Twenty-four rabbits were randomly divided into three groups.We procedured angioplasty and 32P brachytherapy at one side randomly,the absorbed dose were 9.1Gy,21.8Gy and 33.4Gy respectively, the other side non-radiative therapy was served as self-controled. After five weeks cholesterol-fed,the iliac artery angiography was performed to observe the target vessel restenosis degree.Rabbits were killed after operation.Pathological sections of iliac arteries were observed with light-microscope,transmisson electron. Apoptosis was examined using terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL). Results:After five weeks of brachytherapy,the results showed:(1) Angiography: the average luminal diameter stenosis was 55.20±14.47% in control vessels;57.5±13.08% in 9.1Gy vessels;25.27±5.77% in 21.8Gy vessels;78.33± 14.72% in 33.4Gy vessels.(2) Light-microscope :strong neointimal proliferation and strait lumen were observed in the control vessel;there weren't obvious changes in 9.1Gy group(P>0.05);in 21.8Gy group,the lumen areas did not decrease;the cavity serious stenosis,and smooth in media was shrinked and thinned in 33.4Gy group,four vessels occurred arterial thrombosis.(3) Transmission electron: in control vessel the VSMC was synthetical type, thestructure was similar to apoptic body in plasma,collagrn fiber was hyperplastic and fused,formed disorganized,a lot of fatty vacuoles deposited in plasma;there was no difference in 9.1Gy group(P>0.05);in 21.8Gy group the VSMC was contractive type,a lot of apoptic body could be seen in plasma,the collagen fiber was ordinal and obvious decreasing in partial area,,small quantity of fatty vacuoles deposited;in 33.4Gy group the cell dissolved,membrance structure was damaged,coagulation necresis of the cells was showed,collagen fiber was metamorphic and ruptured,fatty vacuoles was filled distributing.(4) TUNEL:the AI was 5.60+1.11% in control vessels;6.10±1.78% in 9.1Gy group vessels;17.31±3.66% in 21.8Gy group vessels;8.89±1.03% in 33.4Gy group vessels ,except 9.1Gy vessels compared with the control (P>0.05),the other groups compared with the control (P<0.01).The effect was much more evident in 21.8Gy group.The dose-effectiveness relation was observed.Conclusions: Endovascular brachytherapy with 32P filled ballon catheter system could prevent restenosis after angioplasty .Inducing VSMC apoptosis may contribute to the preventing of restenosis.
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