Dysregulated miR-124 and miR-200 expression contribute to cholangiocyte proliferation in the cholestatic liver by targeting IL-6/STAT3 signalling.

Background & Aims Cholestatic liver disease is associated with dysregulated expression of microRNAs (miRNAs). However, it remains unknown whether miRNAs are involved in the cholestasis-induced proliferation of cholangiocytes. In this study, we tested the hypothesis that miRNAs modulate cholangiocyte proliferation through effects on the IL-6 pathway, a known regulator of cholangiocyte proliferation. Methods Expression of IL-6, Foxa2, and phosphorylated signal transducer activator of transcription 3 (STAT3) was investigated in patients with biliary atresia (BA) and in rats subjected to bile duct ligation (BDL). miRNA expression was determined in BA patients and BDL rats, with miRNA array and quantitative real-time PCR. Biological functions of miRNAs were studied using immunoblot, immunohistochemical and proliferation assays. Luciferase reporter assays and Western blots were performed to identify miRNA targets. Results Hepatic interleukin-6 (IL-6) expression was significantly elevated in BA patients and BDL rats, while the expression of miR-124 was dramatically decreased in comparison to controls. Moreover, mRNA levels of STAT3 and IL-6 receptor ( IL-6R ) were inversely correlated with those of miR-124. Ectopic expression of miR-124 inhibited IL-6-mediated cholangiocyte proliferation in vitro and cholangiocyte hyperplasia in vivo , through a mechanism involving direct targeting of the 3’-untranslated region of STAT3 and IL-6R . We further demonstrated that miR-200 family members were significantly upregulated in cholestasis and inhibited FOXA2 expression in cholangiocytes, which further enhanced the expression of IL-6. Conclusions Our findings suggest that downregulation of miR-124 and upregulation of miR-200 collaboratively promote bile duct proliferation through the IL-6/STAT3 pathway. [ABSTRACT FROM AUTHOR]