人粥状硬化初期像における血栓の役割

Abstract

The role of thrombosis on the genesis of early atherosclerosis was discussed on this paper.Forty-four human aortas were dissected respectively into 30-50 step sections, and were studied morphologically about the existence of thrombi and, if they existed, about their types, and the relation to intimal surface on which they grew.569 thrombi were found histologically in 1500 sections taken from 44 aortas about mentioned, and the results were as follows:1) Thrombus formation of human aortas were the findings which could be seen very frequently. The frequency of thrombus formation is 7% in young age group under 30 years old, and with advancing age, its frequency increased; 8% in 3rd decade, 9% in 4th decade, 13.5% in 5th decade, 10.5% in 6th decade, 25.5% in 6th decade and 33.5% in over 80 years old.2) Thrombi were morphologically classified into three types: microthrombus, membranous fibrin thrombus and organizing thrombus. These thrombi could be found not frequently ever on intimal surface where no sclerotic lesion was seen (“no lesion”).3) In the section of “no lesion”, the frequency of thromosis was 11%, and almost all of them were microthrombi. The areas of “cloudy thickening” (early lesion) revealed 47% in its frequency, and 6% of all of them were “membranous fibrin” and “organizing” thrombi.The frequency of thrombus formation on atherosclerotic plaque was 42%. It was remarkably high in comparison with others, and 32% of them were “membranous fibrin” or “organizing” thrombi.4) Electron-microscopically, endothelial change such as increased cytoplasmic density, lipid droplets, dilatation of endoplasmic reticulum, detachment of endothelium and subendothelial edema were found in varying degrees.These changes were frequently observed in normal intima and increased with aging.These findings were also observed in the intima beneath the thrombi. It was suggested that the change of intima, especially that of endothelium would contribute to thrombus formation. In this study, “no lesion”means the classification of macroscopic level.5) The trasformation into elevated fibrous lesions or fibrous intimal thickening from microthrombi and membranous fibrin thrombi was demonstrated in serial sections.6) Though early atherosclerosis could certainly result from the organization of throbus, “cloudy thickening” as an early atherosclerotic lesion would be originated also from tissue reactions occured by hemodynamic or chemical stimili.These early intimal changes would offer the base for thrombosis and is followed by the development of fibrous plaque and atheroma. It seems doubtful, however, that all of the microthrombi could be organized and transform into fibrous lesions.Some of them, at least, will disappear by detatching or fibrinolytic activity.