Repolarization Precedes Oval Cell-mediated Hepatocytic Regeneration in the CDE Diet Mouse Model.

The liver has a unique ability to recover from injury unlike any other organ. A poorly understood aspect of liver regeneration is the role of hepatocellular polarization. Neighbor of Punc E11 (Nope) is an oncofetal stem/progenitor cell marker, which is expressed by depolarized adult hepatocytes after cholestatic liver injury and in hepatocellular carcinoma. Liver injury induced by a choline-deficient and ethionine-supplemented diet is reversible if followed by an additional dietary stop interval and enabled us to study the expression of Nope during the induction of chronic liver injury and during subsequent liver regeneration. We could show by quantitative RT-PCR, Western blotting, and immunohistochemistry that the expression of Nope is induced in depolarized adult hepatocytes during injury. However, after another 2 weeks of a normal diet, the polarization of hepatocytes was almost completely restored and the expression of Nope remained limited to bile ducts and oval cells. Using an inducible CK19-lineage tracing model, we could demonstrate that oval cell-mediated hepatocyte regeneration is rare and was preceded by repolarization of hepatocytes. In conclusion, polarization of hepatocytes is an important part of liver regeneration and precedes oval cell-mediated regeneration of the liver. This process can be visualized by a characteristic expression pattern of Nope.

Telmisartan plus propranolol improves liver fibrosis and bile duct proliferation in the PSC-like Abcb4-/- mouse model.

BACKGROUND: Primary sclerosing cholangitis (PSC) is a chronic cholestatic liver disease leading to cirrhosis and cholangiocellular carcinoma. Inhibitors of the renin-angiotensin system or the sympathetic nervous system delay liver fibrogenesis in animal models. AIMS: We investigated the antifibrotic potential of telmisartan, an angiotensin II type 1 receptor antagonist, and the ß-adrenoceptor blocker propranolol in the PSC-like Abcb4 knockout mouse model. METHODS: Sixty-five Abcb4 (-/-) mice were treated with telmisartan for 3 or 5 months (T) and with telmisartan plus propranolol for 3, 5, or 8 months (TP), or for 2 or 5 months starting with a delay of 3 months (TP delayed). Liver hydroxyproline content, inflammation, fibrosis, and bile duct proliferation were assessed; fibrosis-related molecules were analyzed by real-time polymerase chain reaction and Western blotting. RESULTS: Compared to controls, telmisartan monotherapy had no significant influence on hydroxyproline; however, telmisartan plus propranolol reduced hydroxyproline (TP 3 months, p = 0.008), fibrosis score (TP 3 months and TP 8 months, p = 0.043 and p = 0.008, respectively; TP delayed 8 months, p < 0.0005), bile duct proliferation (TP 8 months and TP delayed 8 months, p = 0.006 and p < 0.0005, respectively), and procollagen α1(I), endothelin-1, TIMP-1 and MMP3 mRNA as well as α-SMA, CK-19, and TIMP-1 protein. CONCLUSIONS: Telmisartan plus propranolol reduces liver fibrosis and bile duct proliferation in the PSC-like Abcb4 (-/-) mouse model, even when started at late stages of fibrosis, and may thus represent a novel therapeutic option for cholestatic liver diseases such as PSC.