Relation Between Aortic Smooth Muscle Cells Outgrowth and Vascular Wall Tissue Disorder

We developed a rabbit model of atherosclerosis showing increased triglycerides, blood pressure, plasma glucose and insulin levels, and presenting with sclerotic lesions in the aorta, coronary artery and cerebral artery without cholesterol loading. This model is considered to closely reflect atherosclerosis in humans. The relation between the extent of aortic medial smooth muscle cells outgrowth (COG) in the aorta and vascular wall tissue disorder has not yet been thoroughly investigated in the human aorta. In this regard, we used this Syndrome X-like atherosclerosis rabbit model to assess COG in atherosclerosis. We compared the percent of COG with the quantitated values (%Extinction) of various histochemical arterial wall components (smooth muscle cells, elastin, collagen type III, type I, hyaluronic acid, glycoproteins, Alcian Blue-positive substance, PASpositive substance, calcium and cholesterol) which reflect arterial wall tissue disorder, using two-dimensional patterns.Since eicosapentaenoic acid (EPA), an omega-3 polyvalent unsaturated fatty acid contained in fish oil, is known to have anti-atherosclerosis effects, the influence of EPA on COG and wall components was also investigated by comparing the two-dimensional patterns of COG and wall components in rabbits with atherosclerosis (atherosclerosis group), rabbits with atherosclerosis administered EPA (300mg/rabbit/day; EPA group) and healthy rabbits fed a standard diet (control group).It is said that the percent of COG increases in proportion to the severity of vascular wall tissue disorder in rabbits in which atherosclerosis is induced by a high cholesterol diet. However, we observed that COG increased in the initial to middle stage of the vascular disorder, then decreased from the middle to terminal stage in our rabbit model.According to the two-dimensional patterns of COG and wall components, the EPA group definitely differed from the atherosclerotic group in comparison with the status assessed based on wall component alone and was distributed in a position closer to the control group, indicating more clearly the anti-atherosclerotic action of EPA.