Distribution of Collagen I, III, and IV and Laminin in the Human Liver during Prenatal Development.

In the absence of systematized data on the extracellular matrix components during prenatal liver development, the present study aimed to investigate the time of appearance and distribution of collagen types I, III, and IV and laminin. The study material included embryonic and fetal livers, aged 7-37 weeks, categorized into 3 trimesters. The material was stained using hematoxylin-eosin and immunohistochemistry methods for the identification of collagen I, III, and IV and laminin. Collagen I was detected near the end of the first trimester in the capsules and walls of interlobular veins. As the liver matures, collagen I is increasingly abundant in the capsules, portal area connective tissues, arterial walls, interlobular veins, sinusoids, and central veins. Collagen III and collagen IV appear in the middle of the first trimester in the capsules, portal areas, and walls of central veins, as well as the sinusoids particularly. In trimesters 2 and 3, these collagens are increasingly present in all the structures, but collagen IV is also present in nerve fibers. Laminin is sporadically present adjacent to the sinusoids in trimester 1, while in trimesters 2 and 3 this protein commonly appears in the walls of arteries and interlobular veins, in the basal membrane of bile ducts, and in nerve fibers. The contents of collagen I, III, and IV increase during prenatal development in the liver capsule, arterial and vein walls, sinusoids, and portal area. Laminin expression is consistent with that of the collagens with the exception that, within lobules, laminin disappears with liver maturation.