Phenotypical and morphological alterations to rat sinusoidal endothelial cells in arterialized livers after portal branch ligation.

The hepatic sinusoids are preferentially supplied with portal venous blood and equipped with fenestrated endothelial cells that are distinct from capillary endothelial cells. We previously observed in rats that sinusoidal capillarization proceeded concurrently with arterial blood supply during hepatocarcinogenesis. This study aimed to clarify the inducing role of arterialization in sinusoidal capillarization by investigating phenotypical, morphological and functional alterations to sinusoidal endothelial cells (SECs) in arterialized rat livers induced by portal branch ligation. At one week, after massive hepatic necrosis following ligation, the livers were restored to their normal architecture without causing post-necrotic fibrosis. At 12-21 weeks, they exhibited a normal histology except for mild pericellular fibrosis which developed along sinusoids or between adjacent hepatocytes. SECs expressed factor VIII-related antigen and showed a decrease in the number of fenestrae and porosity, still lacking any basement membrane but further retaining the functional capacity for carmine dye uptake. Stellate cells, while occasionally associated with large amounts of collagen bundles, contained many lipid droplets and expressed no alpha-smooth muscle actin, indicating a quiescent property. Kupffer cells were commonly found within the sinusoids. The present results indicate that arterialization of the liver induces a partial (but not complete) transition of SECs into capillary-type endothelial cells, suggesting that arterialization might be one of the factors which induce sinusoidal capillarization in the development of hepatocellular carcinoma.