Immunolocalization of a fibronectin-binding proteoglycan (PG-P1) immunologically related to HSPG2/perlecan in normal and fibrotic human liver.

Immunolocalization of a fibronectin-binding proteoglycan (PG-P1) in relation to fibronectin, type IV collagen and laminin, in normal and fibrotic human liver was investigated by light and electron microscopy. HS-42, which is a monoclonal antibody to PG-P1 and is reported to recognize a heparan sulfate proteoglycan named HSPG2/perlecan, was used for this purpose. Light microscopy in the human liver with minimal changes revealed that PG-P1 was present along the hepatic sinusoids as well as fibronectin and type IV collagen, whereas laminin was only weakly detected. In portal areas, PG-P1 was only localized on basement membranes around bile duct systems and blood vessels, as well as laminin and type IV collagen, while fibronectin was scarcely detected in basement membranes. In the fibrotic liver, fibronectin was abundant in necrotic and/or newly fibrosing areas, while PG-P1 was absent in these regions. Using immunoelectron microscopy, PG-P1 was localized in the space of Disse in nearly normal livers and was only detected on basement membranes in portal tracts. In fibrotic livers, PG-P1 in the space of Disse occasionally showed a basement-membrane-like deposition in parallel with the increased light microscopical deposition of laminin in this area, suggesting the positive participation of PG-P1 in the sinusoidal capillarization. Most capillary and sinusoidal endothelial cells, and rarely bile epithelial cells revealed the reaction products of PG-P1 in their rough endoplasmic reticulum and small vesicles. Thus, it was suggested that these cell types are mainly, if not wholly, responsible for PG-P1 production.(ABSTRACT TRUNCATED AT 250 WORDS)