Ultrastructural and Immunohistochemical Study of Hepatic Fibrosis after the Ligation of the Common Bile Duct in Rats / 대한소아소화기영양학회지

PURPOSE: Proliferation of bile duct-like structures and fibrosis is a hepatic cellular reaction observed in most forms of human liver disease and in a variety of experimental conditions associated with liver injury. The aim of this study was to investigate the activation of Ito cells and bile duct proliferation in the rat after common bile duct ligation (CBDL). METHODS: Hepatic morphological abnormalities were examined in rats whose bile ducts had been irreversibly ligated for 15, 21, 24 and 28 days. The liver was examined by immunohistochemical staining for alpha-smooth muscle actin, the known marker of activated Ito cells, and light and electron microscopes. RESULTS: After CBDL, the bile canalicular proliferation and interstitial fibrosis were gradually increased in the periportal areas extended to hepatic sinusoids. Ito cells positive for alpha-smooth muscle actin were frequently observed in the periductular space and in perisinusoidal space of Disse. Ito cells and myofibroblasts were gradually increased in the interstitial fibrosis until the 28th day after CBDL. Ito cells and myofibroblasts had microfilaments with dense body at the periphery of the cell. CONCLUSIONS: Our results suggest that Ito cells may be fibroblastic or myogenic. It has also been postulated that during the development of hepatic fibrosis, Ito cells become myofibroblasts or fibroblast like cells.

The Relevance of Degree of Liver Fibrosis, Ito cell, and PKC Activity in Hepatic Fibrogenesis / 대한간학회지

BACKGROUND/AIMS: Hepatic fibrosis in rat induced by thioacet amide shares similar morphological and biochemical characteristics with human liver cirrhosis. Thioacetamide (T AA) initially induces accumulation of collagen in Disse space and eventually leads to macro- and micronodular cirrhos is. Ito cell was believed to play a main role in hepatic fibrosis. And it s activity was known to be regulated by the expression of various genes. But little has been discovered about the upstream signal trans duction pathway of these genes in hepatic fibrosis. The expression of genesrelated to Ito cell activity was regulated by many transcription factors , the activity of which was regulated by protein kinase C( PKC) is oforms. So it is s upposed that PKC could be as s ociated with fibrosis in liver. METHODS: We investigated the correlation of PKC is oforms and It ocell activity in the course of hepatic fibrosis using TAA induced rat liver cirrhosis model. We used six week- old male rats , and administered 0.03% TAA in drinking water. The animals were sacrificed at 9, 20, and 30 weeks after TAA administration. The degree of hepatic fibrosis was evaluated by measuring the total amount of collagen.-SMA immunohist ochemical st aining of liver tissue was done to determine the Ito cell activity. The expression pattern of PKC isoforms was investigated by West ern blotting. RESULTS: In TAA- treated group, collagen cont ent and Ito cell activity did not increase until 30 weeks and 20 weeks of treatment , respectively, while in control group collagen cont ent and Ito cell activity were not detected. Collagen content showed linear correlation with Ito cell activity. This implied that the proliferation of activated Ito cells was prior to the increase of collagen content. In view of expression pattern of PKC is oforms, PKC alpha showed no difference in TAA- treated group and control group. In TAA-treated group, PKCbeta1 exhibited increased level of expression in both particulate and cytosolic forms at 9 weeks, while PKCdelta and PKC epsilon showed striking shift to particulated form. After 20 weeks, all of the PKC beta1, delta, and epsilon degenerated and showed remarkably decreased level of expression. This suggested PKC alpha had no relation to hepatic fibrosis,while PKC beta1, delta, and epsilon, showing activity at 9 weeks, were related to fibrosis og liver. In response to fibrogenic factors, molecules engaged in intracellular signal transduction pathway like PKC beta1, delta, and epsilon, began to change prior to the increase of Ito cell activity, morphologic changes and alterations of collagen content. CONCLUSION: Our results strongly suggest that the activity of PKC isoforms play an important role in early step of hepatic fibrosis, while accompanying Ito cell activity do in later step.

Ito Cell Activity and Hepatocyte Proliferation Activity According to Collagen Content in Liver Cirrhosis / 대한간학회지

BACKGROUND/AIMS: Liver cirrhosis is an end-stage liver disease. Ito cell is known to have central role in fibrogenes is of liver cirrhosis. But collagen content and Ito cell activity in liver cirr hosis have received little attention. So Ito cell activity and hepatocyte proliferation activity according to collagen content was investigated. WAF-1 and c- met were studied to evaluate the effect of cell cycle. METHODS: We analyzed 56 cases of liver cirrhosis ( viral:41, biliary:11, alcoholic:2, Wilson' s disease:2). Collagen content was measured by spectrophot ometry. Ito cell activity and prolifer ation index was measured by-SMA and Ki- 67 immunohistochemistry. RESULTS: In viral cirrhosis, high collagen group showed increased Ito cell activity compared to low collagen group. There was no difference in hepatocyte prolifer ation activity bet ween high and low collagen group in viral cirrhosis. In biliary cirrhos is, high collagen group showed increased Ito cell activity in septal zones compared to low collagen group. WAF- 1and c- met were negative in most of cases. CONCLUSION: Collagen content of liver cirrhosis is closely related to increment of activated Ito cells . Ito cell activity was prominent in septal zones than in parenchymal areas of viral cirrhosis and that was only significant in septal zones of biliary cirrhosis. There is no correlation bet ween collagen content and hepatocyte proliferation activity.

The Role of Ito Cell in Hepatic Fibrosis after Common Bile Duct Ligation: inhibitory role of vitamin A in Ito cell

The purpose of this study was to investigate the inhibitory role of vitamin A with respect to activation of Ito cells in fibrosis of the rat liver induced by common bile duct ligation(CBDL). The liver was examined by immunohistochemical staining for a-smooth muscle actin,the known marker of activated Ito cells, and light and electron microscopy after CBDL andCBDL with intraperitoneal injection of retinoic acid (Sigma, USA) 1 mg/Kg in 3 times per week. The results were sumrrlerized as follows: After CBDL, the bile ductules were markedly proliferated in the periportal areas extending toterminal hepatic veins. Interstitial fibrosis and inflammatory cell infiltration appeared, however,cholestasis was minimal. Retinoic acid treatment with CBDL decreased bile ductular proliferationand interstitial fibrosis compared to CBDL only. After CBDL, proliferated and activated Ito ceIs showing positive reaction in smooth muscle actin were present in the periductular andperisinusoidal areas, and areas of increased interstitial fibrosis. Activated ito cells weredecreased in number after CBDL with vitamin A treatment. Electron microscopically,intracytoplasmic fat droplets and the cytoplasmic processes of Ito cells were decreased afterCBDL. Myofibroblasts were frequently appeared in the interstitial fibrosis after CBDL. But,intracytoplasmic fat droplets of Ito cells were well preserved, and myofibroblasts were found lessfrequently after CBDL with vitamin A treatment. The results suggest that vitamin A plays an inbitory role in the activation and fibrogenesis ofIto cells after CBDL.