The Epigenetic Modifications by the Histone Demethylase LSD1 in Hepatic Stellate Cells Contribute to Liver Fibrosis

Background and Aim: Liver fibrosis, representing the final common pathway of all types of chronic liver diseases, is a major public health problem worldwide. After chronic liver injury, Hepatic Stellate Cells (HSCs) differentiate into myofibroblasts, which are central players of liver fibrogenesis. LSD1 is a histone H3 lysine 4 (K4) and lysine 9 (K9) demethylase which acts a key player in carcinogenesis, but its function in liver fibrosis is unknown. Hereby, we aim to study the role of LSD1 and its function in epigenetic modifications during liver fibrogenesis.

Methods: Therefore, we inhibited LSD1 function in the HSC cell line, HSC-T6, by a reversible LSD1 inhibitor (HCI-2509). In addition, silenced LSD1 expression by a short hairpin (sh) anti-LSD1 RNA using a pSuper.Retro viral transduction system, generate stable polyclonal and monoclonal LSD1 knockdown HSC cell lines. Expression profilingg of LSD1 silenced HSC was performed by microarrays. Gene and miRNA expression was further quantified by qPCR and changing in the histone modification was studied by Western blot.

Results: In both, HSC knockdown cells and in HSC treated with the HCI-2509 LSD1 inhibitor, LSD1 downregulation resulted in a decreased of epigenetic writers and erasers HDAC3, EZH2, and Mecp2, shown previously to be involved in fibrotic features. In addition we demonstrate that LSD1 silencing causes an altered gene and miRNA expression profile in HSC. Thus, the fibrogenic markers collagen I and SMA were decreased, whereas PPARγ was enhanced. LSD1 mediated alteration of fibrotic components was associated with an altered miRNA pattern, in particular with an increase of the anti-fibrotic miRNA29a, which targets collagen biosynthesis.

Conclusions: In our studies, we collected evidence that LSD1 plays a central role in HSCs, contributing to liver fibrosis. Anti-fibrotic function of LSD1 is suggested to be mediated by its influence on miRNA expression and its impact on other epigenetic modifiers.