Stage-specific expression of the oncofetal marker Neighbor of Punc E11 in Mdr2-/- mice as a model of chronic cholestatic liver injury

Background:

We have shown in previous studies that Neighbor of Punc E11 (Nope) is expressed by hepatocytes in fetal and postnatal liver, after acute cholestatic liver injury due to bile duct ligation or CDE diet and in hepatocellular carcinoma. The Mdr2-/- mouse is a pathophysiological model of cholestatic liver injury allowing us to study the expression of Nope in chronic cholestatic liver injury over long-term periods including chronic liver regeneration as well as tumor development.

Methods:

Mdr2-/- mice were sacrificed at different time points from 6 weeks to 24 months of age. Fibrosis and bile duct proliferation were semi-quantified on H&E staining by a pathologist. Nope expression was quantified by qRT-PCR. Immunofluorescence on cryosections was performed for Nope in combination with Troma (bile ducts), E-cadherin (hepatocytes), DPPIV (both) and Connexin 26 (hepatocytic gap junctions).

Results:

QRT-PCR showed that Nope is expressed in Mdr2-/- mice as early as 6 weeks after birth and increases further thereafter correlating with the degree of fibrosis and biliary injury in H&E staining. In young mice, mainly bile duct proliferations express Nope. With progressive liver damage, Nope expression was also found in fibrotic septae and in hepatocytic clusters located next to portal bile duct proliferation or fibrosis. In these clusters, Cx26 expression was ubiquitously on all membranes of hepatocytes, though it is usually restricted to the canalicular membrane. In old mice, all discovered HCC were found to be Nope positive, while Cx26 was completely absent.

Conclusions:

Nope identifies a subset of depolarized adult hepatocytes after chronic cholestatic liver injury as well as HCC in Mdr2-/- mice. We therefore postulate that Nope might be a valuable biomarker allowing stage-specific stratifications or therapeutic monitoring in cholestatic liver diseases.