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MicroRNA-378 is involved in hedgehog-driven epithelial-to-mesenchymal transition in hepatocytes of regenerating liver.

ABSTRACT: Healthy livers have a remarkable regenerative capacity for reconstructing functional hepatic parenchyma after 70% partial hepatectomy (PH). Hepatocytes, usually quiescent in normal healthy livers, proliferate to compensate for hepatic loss after PH. However, the mechanism of hepatocyte involvement in liver regeneration remains unclear. Hedgehog (Hh) pathway plays an important role in tissue reconstitution by regulating epithelial-to-mesenchymal transition (EMT) in liver disease. MicroRNA (miRNA) is involved in cell proliferation and differentiation during embryonic development and carcinogenesis. It was recently reported that miR-378 inhibits transdifferentiation of hepatic stellate cells into myofibroblasts by suppressing Gli-Krüppel family member 3 (Gli3), the Hh-target gene. We hypothesized that miR-378 influences EMT in hepatocytes by interfering with Hh signaling during liver regeneration. As hepatocytes were highly proliferative after PH in mice, miR-378 and epithelial marker, Ppar-g or E-cadherin were downregulated, whereas both Hh activators, Smoothened (Smo) and Gli3, and the EMT-inducing genes, Tgfb, Snail and Vimentin, were upregulated in the regenerating livers and in hepatocytes isolated from them. Compared to cells with or without scramble miRNA, primary hepatocytes transfected with miR-378 inhibitor contained higher levels of Gli3 with increased expression of the EMT-promoting genes, Tgfb, Snail, Col1a1, and Vimentin, suggesting that miR-378 influenced EMT in hepatocytes. Smo-depleted hepatocytes isolated from PH livers of Smo-flox mice showed downregulation of EMT-promoting genes and Gli3, with upregulation of miR-378 and E-cadherin compared to Smo-expressing hepatocytes from PH liver. In addition, delivery hepatocyte-specific AAV8 viral vector bearing Cre recombinase into Smo-flox mice impeded EMT in Smo-suppressed hepatocytes of PH liver, indicating that Smo is critical for regulating hepatocyte EMT. Furthermore, the application of miR-378 mimic into mice with PH delayed liver regeneration by interrupting hepatocyte EMT. In conclusion, our results demonstrate that miR-378 is involved in hepatocyte EMT by regulating Hh signaling during liver regeneration.

SUBMITTER: Kim J

PROVIDER: S-EPMC6006434 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature

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MicroRNA-378 is involved in hedgehog-driven epithelial-to-mesenchymal transition in hepatocytes of regenerating liver.

Kim Jieun J Hyun Jeongeun J Wang Sihyung S Lee Chanbin C Jung Youngmi Y

Cell death & disease 20180618 7

Healthy livers have a remarkable regenerative capacity for reconstructing functional hepatic parenchyma after 70% partial hepatectomy (PH). Hepatocytes, usually quiescent in normal healthy livers, proliferate to compensate for hepatic loss after PH. However, the mechanism of hepatocyte involvement in liver regeneration remains unclear. Hedgehog (Hh) pathway plays an important role in tissue reconstitution by regulating epithelial-to-mesenchymal transition (EMT) in liver disease. MicroRNA (miRNA) ...[more]

PMID: 29915286

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Project description:Background & aimsChronic failure of mechanisms that promote effective regeneration of dead hepatocytes causes replacement of functional hepatic parenchyma with fibrous scar tissue, ultimately resulting in cirrhosis. Therefore, defining and optimizing mechanisms that orchestrate effective regeneration might prevent cirrhosis. We hypothesized that effective regeneration of injured livers requires hepatocytes to evade the growth-inhibitory actions of TGFβ, since TGFβ signaling inhibits mature hepatocyte growth but drives cirrhosis pathogenesis.MethodsWild-type mice underwent 70% partial hepatectomy (PH); TGFβ expression and signaling were evaluated in intact tissue and primary hepatocytes before, during, and after the period of maximal hepatocyte proliferation that occurs from 24-72 h after PH. To determine the role of Yap1 in regulating TGFβ signaling in hepatocytes, studies were repeated after selectively deleting Yap1 from hepatocytes of Yap1flox/flox mice.ResultsTGFβ expression and hepatocyte nuclear accumulation of pSmad2 and Yap1 increased in parallel with hepatocyte proliferative activity after PH. Proliferative hepatocytes also upregulated Snai1, a pSmad2 target gene that promotes epithelial-to-mesenchymal transition (EMT), suppressed epithelial genes, induced myofibroblast markers, and produced collagen 1α1. Deleting Yap1 from hepatocytes blocked their nuclear accumulation of pSmad2 and EMT-like response, as well as their proliferation.ConclusionInteractions between the TGFβ and Hippo-Yap signaling pathways stimulate hepatocytes to undergo an EMT-like response that is necessary for them to grow in a TGFβ-enriched microenvironment and regenerate injured livers.Lay summaryThe adult liver has an extraordinary ability to regenerate after injury despite the accumulation of scar-forming factors that normally block the proliferation and reduce the survival of residual liver cells. We discovered that liver cells manage to escape these growth-inhibitory influences by transiently becoming more like fibroblasts themselves. They do this by reactivating programs that are known to drive tissue growth during fetal development and in many cancers. Understanding how the liver can control programs that are involved in scarring and cancer may help in the development of new treatments for cirrhosis and liver cancer.

Project description:BackgroundUnderstanding how mesenchymal cells arise from epithelial cells could have a strong impact in unveiling mechanisms of epithelial cell plasticity underlying kidney regeneration and repair. In primary human tubular epithelial cells (HUTEC) under different TGF beta 1 concentrations we had observed epithelial-to-mesenchymal transition (EMT) but not epithelial-myofibroblast transdifferentiation. We hypothesized that the process triggered by TGFbeta 1 could be a dedifferentiation event. The purpose of this study is to comprehensively delineate genetic programs associated with TGF beta 1-driven EMT in our in vitro model using gene expression profile on large-scale oligonucleotide microarrays.ResultsIn HUTEC under TGF beta 1 stimulus, 977 genes were found differentially expressed. Thirty genes were identified whose expression depended directly on TGF beta 1 concentration. By mapping the differentially expressed genes in the Human Interactome Map using Cytoscape software, we identified a single scale-free network consisting of 2630 interacting proteins and containing 449 differentially expressed proteins. We identified 27 hub proteins in the interactome with more than 29 edges incident on them and encoded by differentially expressed genes. The Gene Ontology analysis showed an excess of up-regulated proteins involved in biological processes, such as "morphogenesis", "cell fate determination" and "regulation of development", and the most up-regulated genes belonged to these categories. In addition, 267 genes were mapped to the KEGG pathways and 14 pathways with more than nine differentially expressed genes were identified. In our model, Smad signaling was not the TGF beta 1 action effector; instead, the engagement of RAS/MAPK signaling pathway seems mainly to regulate genes involved in the cell cycle and proliferation/apoptosis.ConclusionOur present findings support the hypothesis that context-dependent EMT generated in our model by TGF beta 1 might be the outcome of a dedifferentiation. In fact: 1) the principal biological categories involved in the process concern morphogenesis and development; 2) the most up-regulated genes belong to these categories; and, finally, 3) some intracellular pathways are involved, whose engagement during kidney development and nephrogenesis is well known. These long-term effects of TGF beta 1 in HUTEC involve genes that are highly interconnected, thereby generating a scale-free network that we named the "TGF beta 1 interactome", whose hubs represent proteins that may have a crucial role for HUTEC in response to TGF beta 1.

Project description:The most frequent alteration in the prostate oncogenome is loss of chromosome (chr) 8p21 that has been associated with loss of NKX3.1 homeobox gene. Chr8p21 deletions increase significantly with tumor grade and are associated with poor prognosis in prostate cancer (PCa), suggesting critical involvement of this region in tumor progression. Recent studies suggest that apart from NKX3.1, this region harbors alternative tumor suppressors that are yet undefined. We proposed a novel, paradigm shifting hypothesis that this locus is associated with a miRNA gene cluster-miR-3622a/b- that plays a crucial suppressive role in PCa. Here we demonstrate the crucial role of miR-3622a in prostate cancer epithelial-to-mesenchymal transition (EMT). MicroRNA expression profiling in microdissected human PCa clinical tissues showed that miR-3622a expression is widely downregulated and is significantly correlated with poor survival outcome and tumor progression. To understand the functional significance of miR-3622a, knockdown and overexpression was performed using non-transformed prostate epithelial and PCa cell lines, respectively, followed by functional assays. Our data demonstrate that endogenous miR-3622a expression is vital to maintain the epithelial state of normal and untransformed prostate cells. miR-3622a expression inhibits EMT, progression and metastasis of PCa in vitro and in vivo. Further, we found that miR-3622a directly targets EMT effectors ZEB1 and SNAI2. In view of these data, we propose that frequent loss of miR-3622a at chr8p21 region leads to induction of EMT states that in turn, promotes PCa progression and metastasis. This study has potentially significant implications in the field of prostate cancer as it identifies an important miRNA component of a frequently lost chromosomal region with critical roles in prostate carcinogenesis which is a highly significant step towards understanding the mechanistic involvement of this locus. Also, our study indicates that miR-3622a is a novel PCa biomarker and potential drug target for developing therapeutic regimens against advanced PCa.

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MicroRNA-378 is involved in hedgehog-driven epithelial-to-mesenchymal transition in hepatocytes of regenerating liver.

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MicroRNA-378 is involved in hedgehog-driven epithelial-to-mesenchymal transition in hepatocytes of regenerating liver.

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