Dynamic expression of desmin, α-SMA and TGF-β1 during hepatic fibrogenesis induced by selective bile duct ligation in young rats

We previously described a selective bile duct ligation model to elucidate the process of hepatic fibrogenesis in children with biliary atresia or intrahepatic biliary stenosis. Using this model, we identified changes in the expression of alpha smooth muscle actin (α-SMA) both in the obstructed parenchyma and in the hepatic parenchyma adjacent to the obstruction. However, the expression profiles of desmin and TGF-β1, molecules known to be involved in hepatic fibrogenesis, were unchanged when analyzed by semiquantitative polymerase chain reaction (RT-PCR). Thus, the molecular mechanisms involved in the modulation of liver fibrosis in this experimental model are not fully understood. This study aimed to evaluate the molecular changes in an experimental model of selective bile duct ligation and to compare the gene expression changes observed in RT-PCR and in real-time quantitative PCR (qRT‐PCR). Twenty-eight Wistar rats of both sexes and weaning age (21-23 days old) were used. The rats were separated into groups that were assessed 7 or 60 days after selective biliary duct ligation. The expression of desmin, α-SMA and TGF-β1 was examined in tissue from hepatic parenchyma with biliary obstruction (BO) and in hepatic parenchyma without biliary obstruction (WBO), using RT-PCR and qRT‐PCR. The results obtained in this study using these two methods were significantly different. The BO parenchyma had a more severe fibrogenic reaction, with increased α-SMA and TGF-β1 expression after 7 days. The WBO parenchyma presented a later, fibrotic response, with increased desmin expression 7 days after surgery and increased α-SMA 60 days after surgery. The qRT‐PCR technique was more sensitive to expression changes than the semiquantitative method.

Hepatic Fibrogenesis / 대한소화기학회지

In acute injury, liver recovers completely without any scarring change or complication. However, large portion of liver is changed into fibrotic state by excessive production of extracellular matrix (ECM) under chronic injury. Excessive production of ECM results in hepatic fibrosis and repeated process of hepatic fibrosis progress into liver cirrhosis. Liver cirrhosis is an irreversible and terminal state of chronic liver disease and one of the major causes of death in Korea. To block the progression to liver cirrhosis, various studies in the field of virology and immunology have been proceeded. Recently, studies on the hepatic fibrogenesis have progressed with the development of molecular biology. Hepatic stellate cells (HSC) play a key role in the pathogenesis of hepatic fibrosis by producing ECM. The degree of hepatic fibrosis depends on the proliferation and activation of HSC and increased net production of collagen. Therefore, inhibition of HSC activation is one of the main ways to block the progression of hepatic fibrosis. Many kinds of factors such as oxidative stress, acetaldehyde, ascorbic acid, transforming growth factor-beta (TGF-beta) and carbon tetrachloride (CCl4) have been reported to activate HSC and stimulate collagen gene expression. Although there are no definite and effective antifibrogenic agents, possible candidates are antioxidants, interferon, retinoids such as beta-carotene, flavonoids, renin-angiotensin system inhibitors and peroxisome proliferator activated receptor-gamma (PPAR-gamma) agonists. We tried to evaluate the charateristics of HSC in order to develop agents that inhibit hepatic fibrogenesis.

Histochemical and Ultrastructural Studies of Hepatic Fibrogenesis; Its Initiation and the Effect of Dexamethasone in Rats

Intralobular fibrogenesis of the liver following hepatocellular damage has long been a controversial subject in regard to its initiation and prevention. To investigate the site of hepatic fibrogenesis and the effect of glucocorticoids during the early stage of hepatic fibrogenesis, dexamethasone was administered in a daily dose of 8 mg/rat following a sing1e dose of CCl4 to induce hepatic necrosis with or without combination of vitamin A to Stimulate lipocytes. Light and electron microscopic examinations of the liver at 2, 4, 6, 8 and 10 days after CCl4, vitamin A and dexamethasone treatment demonstrated that hepatocellular damage stimulated perisinusoidal lipocytes which in turn actively produced collagens. Concomitant administration of vitamin A enhanced stimulation of lipocytic activity and consequently increased collagen formation, while administration of dexamethasone suppressed lipocytic activity leading to an inhibition of collagen formation.