The Roles And Mechanism Of MicroRNA-127in Rat Liver Regeneration

Liver is the centre of organism for material metabolism,energy transformation andnutrition supply, also a collecting and distributing centre for signaling molecules oforganism. It is one of the few organs which have the capacity to regenerate rapidly aftersurgical or chemical injury. Normally only0.0012%-0.01%of adult liver cells divides, butrat liver can recover to its original mass and volume7-10days after70%partialhepatectomy, this process has been called liver regeneration (LR), in human, it may last6month to recover its mass and functions. LR is a complex process under precise regulationfrom numerous proliferative and inhibitory factors. The fully illustration of LR certainlywill be benefit to diagnosis and treatment of human liver disease. Despite multiple studiesof LR, many aspects of this phenomenon remain unknown, including the rapid initiation ofLR after partial hepatectomy.MicroRNAs (miRNAs) are a class of small regulatory RNAs that silence messengerRNAs by binding to their3'-untranslated regions (UTRs). MiRNAs have been reported tomodulate a variety of biological processes, including cellular differentiation, proliferation,development, metabolism and apoptosis. It is reported that almost30%of genes oforganism has been regulate by different miRNAs, studies of miRNAs is one of the hotpoints and forward field in life sciences. Considering the general down-regulation ofmiRNAs in human cancers and the possible similarities between the initiation of LR andhepatocellular carcinogenesis, although the roles of miRNAs in LR are scarcely studied,we hypothesized that the miRNAs that are down-regulated in the early stage may havecritical roles in the synchronized process of LR, although this must still be illustrated. Itcertainly will be benefit to treatment of human liver disease.In a preliminary study, using a70%rat partial hepatectomy model we found thatmiR-127was down-regulated3h after PH by a microarray analysis, and was especiallyprominent at24h by a Quantitative real-time PCR (qRT-PCR) analysis. To furtherilluminate the roles of miR-127in livers, the present work sought to elucidate whether andhow miR-127and its possible target genes are involved in LR by focusing on the earlystage of this process. In this study, Using Western bottiing and real time PCR we measuredthe expression of miR-127and the candidate target genes Bcl6, Sept7and Setd8. We alsoexamined the roles of miR-127in rat liver cells and animal models by transfection with miR-127mimics or inhibitors to mimic overexpression or downregulation of miR-127.Furthermore, we analyzed the roles of miR-127in human hepatic cancer cells in in vivosettings.Section â… : The roles of miR-127in rat liver regeneration after partial hepatectomyOur previously studies suggest that miR-127may play an important role in rat liverregeneration by microRNA array, although it had not ye been reported. To furtherinvestigate the roles of miR-127in LR, we first determined the expression pattern ofmiR-127and its predicted target genes during LR by Western blotting and real time PCR,then analyzed the functions of miR-127in normal rat liver cell line BRL-3A cells bytransfection of miR-127mimics or inhibitor. Furthermore, to determine the mechanism ofmiR-127in regulating its target genes, a luciferase assay was employed. Finally, we alsoinvestigate the activation patterns of miR-127during LR by measuring the methylationlevels of the CpG islands in the promoter region.Our studies show that overexpression of miR-127in rat liver cells significantlysuppressed cell growth and directly inhibited the expression of Bcl6, Sept7and Setd8.Furthermore, the miR-127expression level inversely correlated with the expression ofthese genes during the early phase of LR, and the down-regulation of miR-127was due tothe rapid hypermethylation of the promoter region of the miR-127gene in liver tissues24hours after PH.Section â…¡: The roles of miR-127in human hepatocellular carcinomaIt is reported that miRNAs play an important role in human cancers, and miRNAs havethe potential role of tumor diagnosis and treatment. Hepatocellular carcinoma (HCC) is the5th most frequent human cancer worldwide, and the second leading cause of cancer relateddeath in China. Hepatectomy is the first choice for treatment of HCC patients in China, butthe outcome is poor due to high recurrence, metastasis and limited anti-tumor drugs aftersurgery. Since most HCCs have dissemination within the liver before resection and areundetectable by imaging techniques, new and efficacious adjuvant therapy strategies areneeded, along with new prognostic biomarkers for early detection of at-risk patients.Therefore, it is clinically meaningful that metastasis and prognosis related molecule and itsfunctional mechanism were found. MiRNAs are small non-coding RNAs thatposttranscriptionally regulate gene expression. MiRNAs possess oncogenic or tumor suppressor activity in various tumors but little is known about miRNA expression patternin hepatocellular carcinoma (HCC). Considering the relationship of LR and HCC, thepurpose of this section was to investigate the potential roles of miR-127in HCC.We used real time PCR to investigate the expression of miR-127and its candidatetarget genes in16patients with HCC. The results showed that tumors had reduced levels ofmiR-127expression and increased the expression of Bcl6but had no differences in Sept7and Setd8as compared with paired nontumorous tissues. In HCC cell line Huh7cells, wedetected that miR-127could suppress the expression of Bcl6, Sept7and Setd8. We alsofound that overexpression of miR-127suppresses hepatocarcinoma cell growth insubcutaneous tumor models. Our studies suggest an anti-tumor role of miR-127in humanhepatocellular carcinoma.Conclusions: Our results show that miR-127is down-regulated in the early phase ofLR due to the rapid methylation of its promoter, and this event promotes hepatocyteproliferation by targeting Bcl6, Sept7and Setd8. We observed that miR-127wasdown-regulated in HCC tissues, and overexpression of miR-127suppresseshepatocarcinoma cell growth in subcutaneous tumor models. Our fndings revealed amiRNA-mediated negative regulation pattern during the early stage of LR and implicate ananti-tumor role for miR-127in liver cancer cells.