Experimental study of the reversibility of sinusoidal capillarization.

This study investigated the reversibility of sinusoidal capillarization in fibrotic rat liver induced by thioacetamide (TAA; 200 mg/kg body weight three times a week). Six weeks later, collagen fibers and hepatic lobular disarrangement were observed on light microscopy and basement membrane formation was noted in the space of Disse. Sinusoidal endothelial fenestrations (SEFs) were decreased in size and number (defenestration), and factor VIII-related antigen was observed in the cytoplasm. We also clarified the phenotypic reversibility of the sinusoidal endothelial cells. After 4 months following discontinuation of TAA exposure, the diameters and numbers of SEFs were increased. Six months later, the basement membrane in the space of Disse disappeared (as assessed by electron microscopy) and 12 months later, factor VIII-related antigen also disappeared. These results indicate that phenotypical changes in the sinusoidal endothelial cells and sinusoidal capillarization in hepatic fibrosis may be reversed.