Pathogenesis And Risk Assessment Of Abdominal Aortic Aneurysm Progressing—a PET/CT Study In Vivo

Background and purposeAbdominal aortic aneurysm(abdominal aortic aneurysm,AAA)is a localized sustained widening of abdominal aorta.The expansion degree is more than 50%.AAA is a common and potentially lethal vascular disease,the development of AAA is not linear,it may accelerate suddenly and rupture,which may cause death of patients.So effectively predictive method of AAA progress is needed urgently,thereby,we can do the surgery before it is too late.With the progress of the research on AAA,recent years,some researchers fund that inflammation palys an inportant roles on AAA's development.PET/CT as a new compound imaging technology which is thought to combine the anatomical structure and physiological function information at same time.At present,it is mainly used in the diagnosis of tumor and inflammatory disease.Theoretically,PET/CT can predict the AAA progress by showing local inflammatory state.But the conliutions are still controversial.In this research,we will adopting a new rabbit infrarenal AAA model produced by perfuse elastic protease,and inject angiotensin sequentialy to accelerate the progress of AAA.So we can explore the role of PET/CT in assessment the AAA progress by compare the results of PET/CT of AAA with different advance rate.MethodsMethods Select 30 New Zealand male rabbits,randomly classify them into 2 groups,the AAA group(group A,n=15)and the hypertension AAA group(group B,n=15).Both two groups are perfused with high elastic protease(100 iu/ml)to establish AAA model.Group B is injected angiotensin II(Ang II)sequentialy After the surgery.Monitor the boold pressure and development of AAA with ultrasound,drawing blood samples(MCP-1?MMP9?MMP2).Two weeks later,after surgery,do the PET/CT scans for both groups.After the scan part of the rabbits(group A=8,groupB=8)were executed to fulfill artery pathological staining(HE,EVG and masson)and immunohistochemical(macrophages CD68?MMP9)staining.The rest of the animal fulfill the ultrasound follow-up to 4 weeks.Analyze the results with SPSS.Results Ultrasound showed that all experimental AAA rabbits model were created successfully.With continuous angiotensin II injection,the rebbits of group B showed significant higher blood pressure and faster rate of ries of AAA than group A's rebbits.Results show that compared with group A,group B had increased serum MMP9,MMP2(all P<0.01),expression of MMP9 and CD68 protein measured by immunohistochemistry method also increased(all P<0.01),and there was no significant difference in MCP-1.The two-week pathology results showed that the arteries organization of group A was changed,elastic fiber was fractured,debris and cavity formation,collagen fibers was increased;the pathologic changes in group B were more severity.Four-week pathology results showed that the arteries organization of group B was broken,normal tissue structures were disappear.As for PET/CT,compared with group A,group B showed higher standardized uptake value(SUV)(P<0.01).Correlation analysis showed positive correlationship between SUV(r = 0.751,P < 0.01)and macrophages dyeing integrated opticdensity,between SUV(r = 0.55,P < 0.05)and MMP9 integrated opticdensity also showed positive correlation.Conclusions PET/CT can detect inflammatory infiltration of AAA,and assess the advance rate of AAA by SUV.