| Research Abstract |
The liver is characterized by its low-pressure circulatory system and has a unique vascular architecture. In this study, we investigated the heterogeneity of vascular endothelial cells and pericytes/smooth muscle cells in the porto-sinusoidal-hepatic venous system.
In a mouse model of hepatitis induced by concanavalin A administration, lymphocyte adherence, transmigration, and adhesion molecule (VCAM-1, E-selectin) expression were most prominent in the sublobular veins, moderate in the sinusoids and small hepatic veins, and negligible in the portal tract (Morikawa et al. 2000). In the same model, hemostasis was most striking in the intermediate zone of the liver lobule, and not obvious in the periportal zone (Miyazawa et al. 1998), indicating the intralobular heterogeneity of the sinusoids.
In the experiment of endothelin-1 perfusion using rats, a distal segment of the preterminal portal venules (300 μm in length) showed a striking constriction of perivascular smooth muscle cells, while stellate cells around the sinusoid underwent negligible constriction, indicating that presinusoidal segments play important roles in the regulation of hepatic microcirculation (Kaneda et al. 1998 ; Ekataksin and Kaneda 1999). Stellate cells have distinct properties from perivascular smooth muscle cells. However, they undergo transformation and gain some properties common to the latter cells. In the capsule of human hepatocellular carcinoma, it is suggested that stellate cells may come to express smooth muscle actin and myosin.
The present results provide basic data on intrahepatic vasculatures to understand the physiological function of the liver and pathogenesis of the hepatic disorders.
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