Periductal Fibrosis and Lipocytes (Fat–Storing Cells or Ito Cells) During Biliary Atresia in the Lamprey

Abstract

Transmission and scanning electron microscopy were utilized to follow the degeneration of bile ducts of lampreys (Petromyzon marinus L.) during metamorphosis. The convoluted bile ducts of larval lampreys are surrounded by rich sinusoids, but this intimate biliovascular relationship is lost during metamorphosis because the bile duct degeneration is accompanied by the development of thick periductal fibrosis. Lipocytes, which are present not only in the parenchyma but also in the interstitial tissue of the liver, increase in number in the periductal fibrous tissue, and their processes are directly opposed to collagen fibrils. Fibrillar materials in the dilated cisternae of the rough endoplasmic reticulum and the nuclear envelope of lipocytes are believed to be excreted by exocytosis in a manner similar to such excretion by fibroblasts. The findings suggest that lipocytes are responsible for the periductal fibrosis during biliary atresia in lampreys. This animal might prove to be an interesting model in which to study the biology and fibrogenic potential of lipocytes.

How Do Lampreys Avoid Cholestasis After Bile Duct Degeneration?

“…The stage by stage features of hepatocyte transformation with a gradual loss www.intechopen.com of bile canaliculi (Sidon & Youson, 1983) along with the gradual disappearance of tight junctions at the bile canaliculi and an increase in area occupied by gap junctions (Youson et al, 1987) have been described in previous studies. Moreover, the degeneration of bile ducts has been associated with the development of marked periductal fibrosis due to fibroblast activation caused by leaked biliary materials (Youson et al, 1987;Yamamoto et al, 1986). Our observation of apoptosis in biliary epithelial cells detected prior to changes in hepatocyte morphology (Morii et al, 2010) was consistent with the results of previous reports.…”

Comparative morphology of the gallbladder and biliary tract in vertebrates: Variation in structure, homology in function and gallstones

“…The livers of adult lampreys, possess cells similar to those of other vertebrates and do not show marked changes due to bile stasis (Youson et al, 1985). The vascular channels surrounding the bile ducts become separated from the ducts by thick fibrous tissue (Yamamoto et al, 1986). Extrahepatic common bile duct cells dedifferentiate and in time give rise to the adult pancreas (Elliott and Youson, 1993;Youson et al, 1987).…”

Male Sea Lampreys, Petromyzon marinus L., Excrete a Sex Pheromone from Gill Epithelia1

“…Larval sea lampreys appear to have evolved this route as well [4,5]. However, this same route is not available to adult sea lampreys, which lack gallbladders and bile ducts [6].…”