Question To identify the cellular source of TgfB2 in a time course of cholestatic liver disease
using Abcb4-KO mice and PSC patients, and to correlate findings to disease stages.
Methods Liver samples from PSC liver biopsies and Abcb4-KO mice at the age of 2-, 6-, 8-
and 12-months were stained for HE, Sirius Red and Orcein to visualize inflammation
and fibrosis. Morphological evaluation was performed using Ishak and Nakanuma scoring
systems. Tgfb2 mRNA expression was analysed by in situ hybridisation using the RNAscope
technique and then compared to age matched wildtype Balb/c mice and disease-free human
liver as well as PSC samples.
Results In Abcb4-KO tissues, we found an increase in grade and stage of fibrosis and inflammation
with advancing disease progression using both scoring systems in comparison to wild
type mice. Disease progression was faster in female than in male mice, especially
with regard to inflammation. Subscores, e.g. portal tract inflammation and interface
hepatitis increased first, while confluent necrosis occurred not before the age of
12 months. Tgfb2 mRNA was expressed in areas of proliferating bile ducts and fibrotically
rearranged tissue at all stages of cholestatic disease. Both murine and human livers
showing higher Ishak and Nakanuma scores also showed stronger tgfb2 expression, particularly
in samples with a high grade of portal inflammation. We are currently performing costaining
with cell type/cell fate markers to specifically identify the cell type that upregulates
TGFb2 expression.
Conclusions The expression of tgfb2 mRNA increased with disease progression of Abcb4-KO mice,
whereby prominent inflammatory grades present with the highest expression levels in
mice and human.
