Anti In-Stent Restenosis Performance Of Phosphocholine Stent In A Porcine Coronary Model

Background and ObjectiveIn-stent restenosis is the main bottleneck of prognosis after percutaneous stent therapy for coronary heart disease. Factors like lesion,inflammation and neointima formation are known as the important contributing elements in restenosis mechanism. The study and utilization of new types of polymer is one of the key roads to resolve the hard nut of restenosis. Our study uses a porcine model of coronary stent lesion and restenosis to evaluate the anti in-stent restenosis performance of phosphocholine stent.MethodsTwenty four healthy male minature pig(weight 28-38kg,aged 6-9 months) were divided at random into four groups:BMS (6, implanting bare cobalt-chromi-um stent), low dose DES(6, implanting phosphocholine stent with 120μg/cm2 sirolimus), high dose DES(6, implanting phosphocholine stent with 150μg/cm2 sirolimus)and refined DES(6, implanting rerefinedd phosphocholine stent with 120μg/cm2 sirolimus). The animals in four groups are comparable at base line.1.The establishment of miniature pig coronary stent lesion and restenosis model and the evaluation of histocompatibility of the new stent.After the animals completed adaptative period,angiography and stents implantation were performed through femoral artery percutaneously.After the operation each pig was given aspirin(100mg/d),clopidogrel(75mg/d) and routine feed. The blood samples were taken at base line and on 28th day after operation for routine and biochemical analysis.The samples of artery with stent were fixed and proceeded to do SEM analysis for endothelialization assessment. The histocompatibility of the stent was evaluated.2.On 28th day after operation, the samples of artery with stent were fixed and proceeded to plastic embedding, sectioning and staining. The cross sections were analyzed under optical microscope to assess the injury and inflammation score. Digital pictures were obtained and analyzed by professional image analysis software to measure and analyze parameters of restenosis.Those data were conducted correlation and difference analysis between groups to evaluate the safety and validity of the anti restenosis effect of the stent.Results1. HistocompatibiltyAfter phosphocholine stents were implanted into miniature pigs'coronary, no serious whole body adverse effect was observed. Gross pathological observation revealed that all samples of coronary arterys with stent showed fat-like change,which was more apparent in DES groups and mild in refined DES. SEM analysis indicated full endothelialization above stent struts with integrated neointima in all coronary arteries with stent.2.Anti in-stent restenosis effectThe Schwartz injury score and Kornowski inflammation score of coronary arteries with stents are positively correlated to those morphologic parameters of restenosis.Pathological results of BMS, low dose, high dose and refined groups show their inhibition ability of neointima with an upward trend.But only the difference between refined DES and BMS group shows statistical significance in neointima thickness.There are no statistically significant differences in parameters of neointimal area and degree of area restenosis.ConclusionsThe phosphocholine stents show preferable gross histocomparability and endothelialization above stent strut. BWS group shows area restenosis of 52.73% (more than 50%).While low dose, high dose and refined DES groups show no restenosis occurrence(not more than 50%).Their area restenosis is 38.01%,34.17% and 31.62% respectively. Pathological results of BMS, low dose, high dose and refined group show their inhibition ability of neointima with an upward trend. But only the difference of neointima thickness between refined DES group and BMS group was statistically significant.There are no statistical difference in parameters of neointimal area and degree of area restenosis between defined and BMS group.