The role of vascular smooth muscle cell phenotypic modulation at the aortic branch in atherogenesis

Abstract

To elucidate the mechanism of the development of atherosclerosis, we have investigated the cell population of phenotypes of contractile (C-SMC) and synthetic (S-SMC) states of SMCs at proximal and distal areas of bifurcation of the celiac and superior mesenteric arteries in children and young persons by transmission electron microscopy. The previous studies in patients with hypercholesterolemia and who were young indicated that percentages of proximal area at bifurcation of both arteries were greater than that of C-SMC (P 0.01), and that C-SMCs at distal area were less than that of S-SMC (P 0.05). Ultrastructurally, SMCs at proximal area were S-SMCs containing many synthetic organelles and intermediate filaments. On the other hand, those at distal area were C-SMCs containing actin, myosin, dense bodies and microtubules. In the present study, we have ascertained that the phenotypic modulation of SMCs in the intima and media might correlate to the physico-medial relationship between SMCs and elastic tissues. In this communication, we have observed that the intimal SMCs transformed their phenotypes from the internal elastic layer (S-SMC) to the superficial layer (C-SMC), and that the medial SMCs in the arteries of the young clearly consisted of two types: one type adhered to the elastic layer and the other type existed with the separated one. The difference between both areas in the relatively young need to be observed in detail from now on. In summary, the vascular SMCs and the elastic lamina are considered to contribute to the subsequent phenotypic modulation and their migration of SMCs.