miRNA-27a-3p is involved in the plasticity of differentiated hepatocytes.

Background: Epigenetic mechanisms, including DNA methylation, histone modifications, and chromatin remodeling, are highly involved in the regulation of hepatocyte viability, proliferation, and plasticity. We have previously demonstrated that repression of H3K27 methylation in differentiated hepatic HepaRG cells by treatment with GSK-J4, an inhibitor of JMJD3 and UTX H3K27 demethylase activity, changed their phenotype, inducing differentiated hepatocytes to proliferate. In addition to the epigenetic enzymatic role in the regulation of the retro-differentiation process, emerging evidence indicate that microRNAs (miRNAs) are involved in controlling hepatocyte proliferation during liver regeneration. Hence, the aim of this work is to investigate the impact of H3K27 methylation on miRNAs expression profile and its role in the regulation of the differentiation status of human hepatic progenitors HepaRG cells.

Methods: A miRNA-sequencing was carried out in differentiated HepaRG cells treated or not with GSK-J4. Target searching and Gene Ontology analysis were performed to identify the molecular processes modulated by differentially expressed miRNAs. The biological functions of selected miRNAs was further investigated by transfection of miRNAs inhibitors or mimics in differentiated HepaRG cells followed by qPCR analysis, albumin ELISA assay, CD49a FACS analysis and EdU staining.

Results: We identified 12 miRNAs modulated by GSK-J4; among these, miR-27a-3p and miR- 423-5p influenced the expression of several proliferation genes in differentiated HepaRG cells. MiR-27a-3p overexpression increased the number of hepatic cells reentering proliferation. Interestingly, both miR-27a-3p and miR-423-5p did not affect the expression levels of genes involved in the differentiation of progenitors HepaRG cells.

Conclusions: Modulation of H3K27me3 methylation in differentiated HepaRG cells, by GSK-J4 treatment, influenced miRNA' s expression profile pushing liver cells towards a proliferating phenotype. We demonstrated the involvement of miR-27a-3p in reinducing proliferation of differentiated hepatocytes suggesting a potential role in liver plasticity.