Three-dimensional examination of hepatic stellate cells in rat liver and response to endothelin-1 using confocal laser scanning microscopy

Background and Aim: Hepatic stellate cells (HSC) are located in the space of Disse and are considered to participate in the regulation of sinusoidal flow. The contractility of quiescent HSC in normal liver has remained controversial, unlike activated HSC in injured liver. The aim of the present study was to examine the morphological changes in quiescent HSC in response to endothelin-1 (ET-1) perfusion. Methods: Sections (50 µm thick) obtained from 15 normal rat livers with or without ET-1 perfusion (1 or 400 nmol/L) were stained immunohistochemically with antiglial fibrillary acidic protein (GFAP) antibody and then examined using confocal laser scanning microscopy. For examination of HSC, hepatic lobules were divided into three anatomic regions from the portal areas to the central veins. The length of HSC cytoplasmic processes and area of the sinusoids relative to the section area, excluding portal tracts and central veins, were measured. Results: The GFAP-positive HSC were distributed relatively evenly in the hepatic lobules and those in region 2 (the area between periportal and pericentral areas) tended to have longer cytoplasmic processes. Perfusion of 1 or 400 nmol/L ET-1 for 25 min resulted in swelling of the cell bodies of GFAP-positive HSC and condensation of the intermediate filaments compared with those perfused with buffer only. Although narrowing of the sinusoidal lumen was observed in each region after perfusion with 400 nmol/L ET-1, there was no apparent shortening of the cytoplasmic processes of HSC. These findings were also confirmed quantitatively. Conclusion: In the normal rat liver, quiescent HSC are not involved in the regulation of sinusoidal blood flow in response to ET-1.