[Analysis of the inflammatory processes in the diffuse thickening of the intima of human aorta]

It is generally recognized that the accumulation of lipids and immuno-inflammatory cells are early signs of atherosclerosis. In the present study, we have investigated the relationship between the deposition of lipids, of immuno-inflammatory cells and the expression of HLA-DR molecules (a marker of immune activation), the molecules of the class II of major histocompatibility complex (MHC) in diffuse thickening of the intima (DIT). Lipids, including triglycerides, cholesterol esters, free cholesterol and phospholipids were studied by chromatography, Oil Red O histochemisty, as well as by electron microscopic analysis. Immuno-inflammatory cells and the expression of HLA-DR were investigated by immunohistochemistry in consecutive section of the same tissue samples. It has been shown that the lipids were unevenly distributed in DIT. In juxtaluminal sublayer, lipids were detected both in the cytoplasm of intimal cells and extracellularly. In the juxtamedial musculoelastic sublayer of the intima, lipids were present predominantly along elastic fibers. The positive correlation between the presence of lipids and the expression of HLA-DR was revealed (r = 0.79; P < 0.001). Also, a positive correlation was found between the deposition of lipids and the number of immune-inflammatory cells, although correlations was different for different sublayers of the intima. In particular, the correlation between the deposition of lipids and immune-inflammatory cells in the juxtaluminal sublayer of the intima was higher (r = 0.99; P < 0.001) than in the juxtamedial musculoelastic layer (r = 0.28; P < 0.001). These data support the hypothesis that postulates that the accumulation of lipids in the intima is a key factor in the initiation of inflammatory reactions. At the pre-atherosclerotic stage of the development of this disease, earlier pathological processes associated with lipid-dependent activation of immune cells occur mainly in the juxtaluminal portion of the intima.