Clinical Histopathology And Related Pathogenesis Of 'Degenerative' Calcific Aortic Valve Disease

Objectives:To analyze the histopathological features of degenerative calcific aortic valve disease(DCAVD) and to find related clinical risk factors.To find the roles of hypercholesterolemia and atorvastatin intervention in the pathological changes of rabbit aortic valves.To observe the effects of hypercholesterolemia and atorvastatin on the nano-structures of rabbit aortic valvular endothelial cells by atomic force microscope(AFM).Methods:Histological and immunohistochemical studies were performed on aortic valve leaflets obtained at autopsy from 18 adults with normal leaflets(n=3), mild and moderate leaflet thickening(n=15),or obtained at aortic valve replacement surgery from 37 patients with clinical severe DCAVD. Cardiovascular diseases risk factors were recorded for each case.New Zealand white rabbits(n=30) were randomly divided into three groups:control group (Group N),high cholesterol diet group(Group HC),and high cholesterol diet plus atorvastatin group(Group AI).After 8 weeks,plasma cholesterol,triglyceride, lipoprotein,aminopherase,and phosphocreatine kinase were measured by standard assays.The aortic valves obtained from each groups were examined histologically and immunohistochemicaUy.New Zealand white rabbits(n=60) were randomly divided into 3 groups:control group,high cholesterol diet group, and high cholesterol diet plus atorvastatin group.After feeding for 2,4,6,or 8 weeks,5 rabbits selected randomly from each groups were executed separately. Fresh aortic valves were dissected from the hearts.After processing,they were loaded on the platform of NanoScopeâ…¢a AFM and scanned in tapping mode. Image analysis system integrated in the AFM was applied to measure the topography structures.Results:Significant thickening in the third basal leaflets could be seen for each case of DCAVD.Thickening was characterized by the presence of intracellular and extracellular neutral lipids,protein and fine,stippled mineralization in subendothelial space on the aortic side of the leaflets and adjacent fibrosa. Accumulation of the materials increased with the degree of lesions. Immunohistochemical studies showed that clustered mono-macrophages,T lymphocytes,neo-formative capillaries,and osteoblasts could be seen both in mild to moderate lesions and in severe lesions of DCAVD.Control valves showed none of these abnormalities.Expression of above mentioned antibodies increased from mild to severe cases.Prevalence of smoking,hyperlipidemia,hypertension,and coronary heart disease in DCAVD with clinical aortic stenosis were significantly higher than that in mild to moderate DCAVD.Plasma cholesterol,triglyceride,and lipoprotein increased in group HC when compared with group AI.Oil red, Von-kossa,and alizarin red histochemical staining were positive in group HC whereas all negative in group N.Immunohistochemistry staining of CD68,CD3, CD31,and osteopontin were positive in group HC,whereas negative or seldom positive in group N.All these characteristics were diminished or weakened in group AI.Under the scanning of AFM,arrangement of endothelial cells changed from intensive regular paliform alignment to disorder scattered alignment when high cholesterol diet was administrated.The shape of endothelial cell transformed from long fusiform to short round shape.Interstitial areas between endothelial cells were enlarged.When the scanning dimention of AFM on the surface of endothelial cells was decreased further to nanometer scale,receptor-like globular bulged structures with center hollow became low,fused,and diminished gradually. The extent of structure changes of endothelial cells of high cholesterol diet plus atorvastatin group was between those of the other two groups.Conclusions:DCAVD is an active inflammatory process with similarities to atherosclerosis.Experimental hypercholesterolemia could induce histopathological changes of early DCAVD that could be transversed by atorvastatin.AFM could display the 3-Dimentional morphology of the surface of aortic valve endothelial cells.High cholesterol diet could influence the arrangement,distribution,and shape of endothelial cells,which might be the basis for DCAVD,and treatment with atorvastatin could modify this transformation.