Immunohistochemical localization of laminin, nidogen, and type IV collagenduring the early development of human liver

There is evidence that basement membrane components control differentiation of liver sinusoids and bile ducts. These processes occur in humans in the 9th gestational week (GW). Distribution of laminin, nidogen, and type IV co llagen was studied during human liver development between the 6th and the 1 0th GW. Laminin and nidogen lined intrahepatic microvessels in the 6th and 7th GW decreasing in quantity at the beginning of the fetal period (9th-l0t h GW). Type IV collagen was detected in microvessels only from the 9th GW o nward. In the early periportal matrix (9th-l0th GW) laminin, nidogen, and t ype IV collagen were diffusely distributed. At these stages, basement membr ane zones of larger portal vessels and of early bile ducts were also staine d for all three glycoproteins. These results show that laminin and nidogen are localized in microvessels during early human liver development and decr ease in concentration at the developmental stage during which microvessels become discontinuous. In contrast, type IV collagen is not present in early microvessels but occurs when laminin and nidogen disappear. The three glyc oproteins occur together only in those areas of the developing liver in whi ch, from the 9th GW onward, the differentiation of immature liver cells int o biliary epithelium takes place.