Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Gastroenterol. Jun 7, 2015; 21(21): 6591-6603
Published online Jun 7, 2015. doi: 10.3748/wjg.v21.i21.6591
Loss of Dicer1 impairs hepatocyte survival and leads to chronic inflammation and progenitor cell activation
Xu-Feng Lu, Yong-Jie Zhou, Lei Zhang, Hong-Jie Ji, Li Li, Yu-Jun Shi, Hong Bu
Xu-Feng Lu, Yong-Jie Zhou, Lei Zhang, Hong-Jie Ji, Li Li, Yu-Jun Shi, Hong Bu, Laboratory of Pathology, West China Hospital, Sichuan University, Chengdu 610041, Sichuan Province, China
Xu-Feng Lu, Regenerative Medicine Research Center, West China Hospital, Sichuan University, Chengdu 610041, Sichuan Province, China
Hong Bu, Department of Pathology, West China Hospital, Sichuan University, Chengdu 610041, Sichuan Province, China
Author contributions: Lu XF, Shi YJ and Bu H designed the research; Lu XF performed the research; Zhou YJ and Zhang L contributed analytic tools; Ji HJ and Li L analyzed the data; and Lu XF, Shi YJ and Bu H wrote the paper; all authors read and approved the final manuscript.
Supported by National Key Clinical Project, and National Sciences; and Technology Major Project of China, No. 2012ZX10002-017.
Ethics approval: This study was reviewed and approved by the ethic committee of the West China Hospital of Sichuan University’s Institutional Review Board.
Institutional animal care and use committee: All procedures involving animals were reviewed and approved by the Institutional Animal Care and Use Committee of the West China Hospital of Sichuan University (IACUC-No. S200904-P001).
Conflict-of-interest: The authors declare that they have no conflict of interest or financial interests.
Data sharing: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Yu-Jun Shi, MD, PhD, Laboratory of Pathology, West China Hospital, Sichuan University, 37 Wainan Guoxuexiang, Chengdu 610041, Sichuan Province, China. shiyujun@scu.edu.cn
Telephone: +86-28-85164030 Fax: +86-28-85164034
Received: November 7, 2014
Peer-review started: November 8, 2014
First decision: December 11, 2014
Revised: December 22, 2014
Accepted: January 8, 2015
Article in press: January 8, 2015
Published online: June 7, 2015
Abstract

AIM: To investigate the continuous hepatic histopathological processes which occur in response to the loss of Dicer1.

METHODS: We generated a hepatocyte-selective Dicer1 knockout mouse and observed the gradual hepatic histopathological changes in the mutant liver. Immunohistochemistry and Western blotting were performed to detect Dicer1 expression. We performed hematoxylin and eosin staining, Periodic acid-Schiff staining, Oil Red O staining, and Masson’s trichrome staining to detect histological changes in Dicer1-deficient livers. Ki67 immunohistochemistry, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay, and Western blotting were used to determine hepatocyte proliferation and apoptosis. Serum biochemistry, cytokine assays, and flow cytometric analysis were performed to quantity liver necrosis and inflammation. Fibrogenic markers were determined by Western blotting and qPCR. CK19, CD133, and OV6 immunofluorescence were used to observe liver progenitor cells. Immunofluorescence and qPCR were performed to reveal embryonic gene expression. We also performed histological staining and Western blotting to analyze hepatocellular carcinoma (HCC) development.

RESULTS: Dicer1 inactivation resulted in significant architecture disorganization and metabolism disruption in the liver. Dicer1 disruption impaired hepatocyte survival and resulted in profound cell apoptosis and continuous necrosis. In contrast to previous reports, the mutant liver exhibited chronic inflammation and progressive fibrosis, and could not be repopulated by Dicer1-positive cells. In addition, extensive activation of hepatic progenitor cells was observed. Primary HCC was observed as early as 4 mo after birth.

CONCLUSION: Hepatic loss of Dicer1 results in complex chronic pathological processes, including hepatocyte death, inflammatory infiltration, chronic fibrosis, compensatory proliferation, progenitor activation, and spontaneous hepatocarcinogenesis.

Keywords: Dicer1, microRNAs, Liver inflammation, Liver fibrosis, Hepatocellular carcinoma

Core tip: MicroRNAs (miRNAs) play a critical role in the regulation of multiple biological genes in the liver. The liver-specific loss of Dicer1, an endoribonuclease essential for precursor miRNAs maturation, results in liver injury and spontaneous development of hepatocellular carcinoma (HCC); however, the gradual histological changes involved in these processes have not been completely characterized. In contrast to previous reports, we found that Dicer1 inactivation causes typical chronic liver injury characterized by profound hepatocyte apoptosis, continuous liver necrosis, active compensatory proliferation, noticeable triad inflammation, progressive liver fibrosis, significant progenitor activation, and spontaneous hepatocarcinogenesis. Our work provides new insights into the role of miRNA in liver injury and HCC development. These results may also aid in the development of a miRNA therapeutic strategy for the prevention and treatment of HCC.