The Primary Study On Residual Stress In Elastase-Induced Abdominal Aortic Aneurysms Model Of Rat

Purpose:To investigate the biomechanical mechanism of artery tissue remodeling,stress distribution and the elasticity of abdominal aortic aneurysms(AAA) model of rats,the effect of intraluminal thrombus on AAA model wall stress so as to forecast the rupture position and the growth direction of AAA.The study was by calculating the opening angel of the artery rings along the AAA。Methods:(1).five adult male Wistar rats underwent blood pressure endoluminally recording at six peculiar different sites ,respectively the common iliac artery,the inferior mesenteric artery,the renal artery,the diaphragm, the ninth thoracic vertebrae and the fifth thoracic vertebrae.compared the blood pressure at the same site with healthy adults; compared the residual stress at same site with healthy adults; compared the the amount contrast of elastin ply in medial with healthy adults of thoracic and abdominal aorta.(2).forty-five adult male Wistar rats were randomly divided into three groups,fifteen rats every group.Fifteen rats(B group) underwent 2-hour aortic perfusion with porcine pancreatic elastase(PPE),and Fifteen rats(C group) underwent the same treatment,in additon the intima destroyed.The final aortic diameters(AD) were determined after 14 days. The last fifteen rats(A group) were control group.(3)Measuring the opening angel of three groups,and comparing the creep velocity,residual stress and wall thickness of the artery rings between the three groups.Results: (1).The adult male Wistar rats have the similar systolic pressure fluctuate with the healthy adult in the the same sites.The systolic pressure gradually increased along the aorta(P<0.01);the pressure of abdominal aorta was high than the thoracic aorta's(P<0.01);the inferior mesenteric's was high than the renal artery's(P<0.01);the difference between the the common iliac artery's and thoracic aorta(P>0.05). The adult male Wistar rats have the similar the amount contrast of elastin ply in medial with the healthy adult.The rats had 15-17 layers in the thoracic aorta medial,7-9 layers in the abdominal aorta medial.The healthy adult had 56 layers in the thoracic aorta medial,25-28 layers in the abdominal aorta medial.The residual stress of the rats and the adult descended from the thoracic aorta to the diaphragm(P>0.05),thenascended along the abdominal aorta(P<0.01).The highest residual stress was at the infranrenal abdominal aorta. (2)The AAA model length was between 12mm and 15mm,excended the inferior mesenteric artery,and the great AAA radius was two times than the normal abdominal aorta's,between 3mm and 3.5mm.The AAA model was an axisymmetric fusiform aneurysm. (3)The thickness of AAA medial and ectoblast had no differenence with the normal abdominal aorta.The thickness of AAA intimal increase remarkably than the the normal abdominal aorta(P<0.05). The light microscopic features of AAA were architectural degeneration of the elastic media.The cellular composition of AAA typically included chronic inflammatory cell infiltrates.The ultrastructural features of AAA were examined aortic tissues by transmission electron microscopy.The extracellular matrix of AAA was dominated by disordered collagen fibers and elastin-associated microfibrillar material,with little detectable insoluble elastin.The morphological characteristics of SMC(smooth muscle cell) were loss of cell volume,cytoplasmic contracture,dissolution of cytoskeletal actin filaments,the apoptotic cell death.The creep velocity of theA group,the B group and the C group increased in turn.It means that the elasticity drceased in turn.The residual stress of the A group were remarkably high than the B,C group(P<0.01). The residual stress of the C group had some difference with the B group(P<0.05).The importment influencial factor were intima hyperplasia ,medial destroyed and intraluminal thrombus.The highest residual stress was in the inlet and outlet of AAA,and the lowest inner radius and the lowest wall thickness was the same sites. Conclusions: Elastase-induced AAA model of rats was a representative model for res...