Local Application Of Rapamycin Inhibits Restenosis In Experimental Vein Grafts

PrefaceCoronary artery bypass surgery ( CABG) has already been a very operative therapy for cronery heart disease patients . arteria and vein are the routine vessal in the suegery now, great saphenous vein is easily harvested, long enough, it has suit vessal area, especially it will not spasm after operation so more and more cardiac surgeons like to use it, but what puzzled us is the graft's restenosis laterly , it has been a focal point of cardiac surgeon how to prevent the restenosis in postoperation, rise the quality of patients life, make them live longer.In 1977, people detected that rapamycin ( RAPA) posses Immunosuppres-sive action and proceed the background and clinical experiment . in 1999, the A-merica FDA gave approval to applicate RAPA in clinic as a immunosuppressive agent.Although RAPA is applicated in clinic as a immunosuppressive agent, more and more people pay attention to its action to an - Immunologic cell. Marx et al find that RAPA in low Concentration (1μg/ml) can prevent the DNA synthesizing of the vascular smooth muscle cell( VSMC) in rat and human, with the pre-treatment to VSMC, RAPA (2ng/ml) can prevent the migration induced by PDGF after 48h,animal experiment also certificate that RAPA can prevent the stricture of artery. Now RAPA is clinically used in a coating of coronary artery stents, the effect is positive. If RAPA can be used onto the graft vein in Coronary artery surgery, so that rise the quality of patient s life, make them live longer.Material and mathodMaterial1 Wistar rat;the 3 months - old, 300g weight, male Wistar rat were purchased from china medical university, animal laboratory . All animals were treated in 24 —26℃ room temperature, breeded by mice food and water.2 Rapamycin;purchased from Fujian Kerui Pharmaceutical Co. , Ltd. Pure RAPA was measured by electronic balance, 1 mg each portion was preservated in bottle , room temperature.3 Fibrin Sealant;produced by Guangzhou Bioseal Biotech Co. , Ltd. carrier of RAPA. RAPA can dissolved in Fibrin Sealants main body glue, the Fibrin Sealant can sustaind -release RAPA,and it can be absorbed by degree in 2 weeks.4 Microsurgery tools and 8-0 bi - bullet suture5 Reagent:primary antibody; mouse anti — bcl - 2, bax monoclonal antibody were purchased from Wuhan Boster Biological Technology Co. , Ltd. Working Concentration is 1:50, DAB reagent and other reagent are offered by china medical university . Tumor institute.6 Instrument: Resection machine( LEITZ 1512) , LG microwave oven, etc.7 Image analysis system;IBM PS/2 80486 DX 33 main unit, NEC Multisync 3FGx Color display, Wescom 600C color viedeo monitor, Olympus BH - 2 bio - microscop , Panasonic WV -CP410 book holders, etc. MethodRat underwent interposition of the Jugular vein into the common carotid artery, 100μg or 200μg of Rapamycin was applied locally around the graft vein. The control group did not receive local treatment. Grafts were harvested at 2, 4, and 6 weeks and underwent morphometric analysis as well as immunohistochemi-cal analysis. Statistical analysisThe SPSS software was used for statistical analysis. Neointimal thickness is given as median and range. Comparisons of histologic measurements of the inti-mal thickness and of immunohistochemistry were made by the T test. Results were considered statistically significant at P <0.05.Results1. H - E staining:the thickness of vein neointimal in case group is less than that of control group, the amount of nucleus is the same changing, the different is obviously at 4 weeks postoperation , the neointimal hyperplasia in control group is significant at 4th week, the hyperplasia in case group is less than control group, the average of control group is 15. 8μm(2th week) , 36. 4μm(4th week) , 42. 8μm(6th week). Case group with 100μg is 9. 4μm(2th week) , 18. 5μm(4th week) , 22. 3μm(6th week). Case group with 200μg is: 8. 5μm(2th week) , 13. 8μm(4th week) , 15.4μm (6th week).2. Immunohistochemistry:bcl - 2 protein is lay in mitochondrion membrane, it also expressed in endoplasmic reticulum membrane and nuclear membrane, after applying RAPA , there is less bcl - 2 protein, bax is an acceleration gene of apopto-sis, it also lay in mitochondrion membrane, it can inactivate bcl - 2, the bax positive cell is obviously increased in case group when RAPA was applied to it.DiscussionsThe restenosis in graft vein after CABG always puzzle cardiac surgeon.