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Polyploid Hepatocytes Facilitate Adaptation and Regeneration to Chronic Liver Injury.

ABSTRACT: The liver contains diploid and polyploid hepatocytes (tetraploid, octaploid, etc.), with polyploids comprising ?90% of the hepatocyte population in adult mice. Polyploid hepatocytes form multipolar spindles in mitosis, which lead to chromosome gains/losses and random aneuploidy. The effect of aneuploidy on liver function is unclear, and the degree of liver aneuploidy is debated, with reports showing aneuploidy affects 5% to 60% of hepatocytes. To study relationships among liver polyploidy, aneuploidy, and adaptation, mice lacking E2f7 and E2f8 in the liver (LKO), which have a polyploidization defect, were used. Polyploids were reduced fourfold in LKO livers, and LKO hepatocytes remained predominantly diploid after extensive proliferation. Moreover, nearly all LKO hepatocytes were euploid compared with control hepatocytes, suggesting polyploid hepatocytes are required for production of aneuploid progeny. To determine whether reduced polyploidy impairs adaptation, LKO mice were bred onto a tyrosinemia background, a disease model whereby the liver can develop disease-resistant, regenerative nodules. Although tyrosinemic LKO mice were more susceptible to morbidities and death associated with tyrosinemia-induced liver failure, they developed regenerating nodules similar to control mice. Analyses revealed that nodules in the tyrosinemic livers were generated by aneuploidy and inactivating mutations. In summary, we identified new roles for polyploid hepatocytes and demonstrated that they are required for the formation of aneuploid progeny and can facilitate adaptation to chronic liver disease.

SUBMITTER: Wilkinson PD

PROVIDER: S-EPMC6547059 | biostudies-literature | 2019 Jun

REPOSITORIES: biostudies-literature

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Polyploid Hepatocytes Facilitate Adaptation and Regeneration to Chronic Liver Injury.

Wilkinson Patrick D PD Alencastro Frances F Delgado Evan R ER Leek Madeleine P MP Weirich Matthew P MP Otero P Anthony PA Roy Nairita N Brown Whitney K WK Oertel Michael M Duncan Andrew W AW

The American journal of pathology 20190328 6

The liver contains diploid and polyploid hepatocytes (tetraploid, octaploid, etc.), with polyploids comprising ≥90% of the hepatocyte population in adult mice. Polyploid hepatocytes form multipolar spindles in mitosis, which lead to chromosome gains/losses and random aneuploidy. The effect of aneuploidy on liver function is unclear, and the degree of liver aneuploidy is debated, with reports showing aneuploidy affects 5% to 60% of hepatocytes. To study relationships among liver polyploidy, aneup ...[more]

PMID: 30928253

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Project description:Whether hepatocytes can convert into biliary epithelial cells (BECs) during biliary injury is much debated. To test this concept, we traced the fate of genetically labeled [dipeptidyl peptidase IV (DPPIV)-positive] hepatocytes in hepatocyte transplantation model following acute hepato-biliary injury induced by 4,4'-methylene-dianiline (DAPM) and D-galactosamine (DAPM+D-gal) and in DPPIV-chimeric liver model subjected to acute (DAPM+D-gal) or chronic biliary injury caused by DAPM and bile duct ligation (DAPM+BDL). In both models before biliary injury, BECs are uniformly DPPIV-deficient and proliferation of DPPIV-deficient hepatocytes is restricted by retrorsine. We found that mature hepatocytes underwent a stepwise conversion into BECs after biliary injury. In the hepatocyte transplantation model, DPPIV-positive hepatocytes entrapped periportally proliferated, and formed two-layered plates along portal veins. Within the two-layered plates, the hepatocytes gradually lost their hepatocytic identity, proceeded through an intermediate state, acquired a biliary phenotype, and subsequently formed bile ducts along the hilum-to-periphery axis. In DPPIV-chimeric liver model, periportal hepatocytes expressing hepatocyte nuclear factor-1β (HNF-1β) were exclusively DPPIV-positive and were in continuity to DPPIV-positives bile ducts. Inhibition of hepatocyte proliferation by additional doses of retrorsine in DPPIV-chimeric livers prevented the appearance of DPPIV-positive BECs after biliary injury. Moreover, enriched DPPIV-positive BEC/hepatic oval cell transplantation produced DPPIV-positive BECs or bile ducts in unexpectedly low frequency and in mid-lobular regions. These results together suggest that mature hepatocytes but not contaminating BECs/hepatic oval cells are the sources of periportal DPPIV-positive BECs. We conclude that mature hepatocytes contribute to biliary regeneration in the environment of acute and chronic biliary injury through a ductal plate configuration without the need of exogenously genetic or epigenetic manipulation.

Project description:BACKGROUND & AIMS: Thirty to ninety percent of hepatocytes contain whole genome duplications, making it imperative to understand the fates and functions of these polyploid cells and how they affect development of liver disease. An important question is how polyploid cells respond to chronic proliferative demands, which are characteristic of liver diseases, but a challenging situation for cells with multiple genomes. METHODS: To interrogate liver polyploidy, we employed a mouse with reversible ANLN ( Anillin actin binding protein) knockdown that drives hepatocyte polyploidization in a doxycycline inducible fashion. Diethylnitrosamine (DEN) and carbon tetrachloride (CCl4) were used to induce chronic liver damage and hepatocellular carcinoma (HCC). We performed partial hepatectomies to test regeneration and RNA-seq to assess gene expression changes. Lineage tracing was used to rule out repopulation from non-hepatocyte sources. In vivo imaging of mitotic hepatocytes estimated the frequency of aneuploidy during regeneration, and exome sequencing of 54 human cirrhotic nodules was used to quantify aneuploidy. RESULTS: Hepatocytes from mice given chronic CCl4 alone showed significant increases in ploidy. Super-polyploid mice with 97% polyploid hepatocytes, due to induced knockdown of Anln , were almost completely protected from tumorigenesis induced by DEN and chronic CCl4 . The protection was not associated with differences in regenerative capacity, tissue fitness, gene regulation, or mitotic errors. Regenerative contributions from a non-hepatocyte population were ruled out using lineage tracing, confirming that polyploids can replenish tissues during chronic damage. No lagging chromosomes or micronuclei were found in mitotic polyploid cells and there was no evidence of chromosomal copy number variations in 54 nodules, suggesting that aneuploidy is not a common outcome of polyploid cell divisions. CONCLUSION: During chronic injury, polyploid hepatocytes readily divide and regenerate while being buffered from tumor suppressor loss and tumorigenesis. Therapeutic strategies to increase numbers of polypoid hepatocytes could prevent cancer while preserving regeneration.

Project description:The liver contains a mixture of hepatocytes with diploid or polyploid (tetraploid, octaploid, etc.) nuclear content. Polyploid hepatocytes are commonly found in adult mammals, representing ~90% of the entire hepatic pool in rodents. The cellular and molecular mechanisms that regulate polyploidization have been well characterized; however, it is unclear whether diploid and polyploid hepatocytes function similarly in multiple contexts. Answering this question has been challenging because proliferating hepatocytes can increase or decrease ploidy, and animal models with healthy diploid-only livers have not been available. Mice lacking E2f7 and E2f8 in the liver (liver-specific E2f7/E2f8 knockout; LKO) were recently reported to have a polyploidization defect, but were otherwise healthy. Herein, livers from LKO mice were rigorously characterized, demonstrating a 20-fold increase in diploid hepatocytes and maintenance of the diploid state even after extensive proliferation. Livers from LKO mice maintained normal function, but became highly tumorigenic when challenged with tumor-promoting stimuli, suggesting that tumors in LKO mice were driven, at least in part, by diploid hepatocytes capable of rapid proliferation. Indeed, hepatocytes from LKO mice proliferate faster and out-compete control hepatocytes, especially in competitive repopulation studies. In addition, diploid or polyploid hepatocytes from wild-type (WT) mice were examined to eliminate potentially confounding effects associated with E2f7/E2f8 deficiency. WT diploid cells also showed a proliferative advantage, entering and progressing through the cell cycle faster than polyploid cells, both in vitro and during liver regeneration (LR). Diploid and polyploid hepatocytes responded similarly to hepatic mitogens, indicating that proliferation kinetics are unrelated to differential response to growth stimuli. Conclusion: Diploid hepatocytes proliferate faster than polyploids, suggesting that the polyploid state functions as a growth suppressor to restrict proliferation by the majority of hepatocytes.

Project description:Prolonged exposure of mice to diet containing 0.1% 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) results in hepatobiliary injury, atypical ductular proliferation, oval cell appearance, and limited fibrosis. Previously, we reported that short-term ingestion of DDC diet by hepatocyte-specific ?-catenin conditional knockout (KO) mice led to fewer A6-positive oval cells than wildtype (WT) littermates. To examine the role of ?-catenin in chronic hepatic injury and repair, we exposed WT and KO mice to DDC for 80 and 150 days. Paradoxically, long-term DDC exposure led to significantly more A6-positive cells, indicating greater atypical ductular proliferation in KO, which coincided with increased fibrosis and cholestasis. Surprisingly, at 80 and 150 days in KO we observed a significant amelioration of hepatocyte injury. This coincided with extensive repopulation of ?-catenin null livers with ?-catenin-positive hepatocytes at 150 days, which was preceded by appearance of ?-catenin-positive hepatocyte clusters at 80 days and a few ?-catenin-positive hepatocytes at earlier times. Intriguingly, occasional ?-catenin-positive hepatocytes that were negative for progenitor markers were also observed at baseline in the KO livers, suggesting spontaneous escape from cre-mediated recombination. These cells with hepatocyte morphology expressed mature hepatocyte markers but lacked markers of hepatic progenitors. The gradual repopulation of KO livers with ?-catenin-positive hepatocytes occurred only following DDC injury and coincided with a progressive loss of hepatic cre-recombinase expression. A few ?-catenin-positive cholangiocytes were observed albeit only after long-term DDC exposure and trailed the appearance of ?-catenin-positive hepatocytes.In a chronic liver injury model, ?-catenin-positive hepatocytes exhibit growth and survival advantages and repopulate KO livers, eventually limiting hepatic injury and dysfunction despite increased fibrosis and intrahepatic cholestasis.

Project description:Background & aimsLiver regeneration is a repair process in which metabolic reprogramming of parenchymal and inflammatory cells plays a major role. Monoacylglycerol lipase (MAGL) is an ubiquitous enzyme at the crossroad between lipid metabolism and inflammation. It converts monoacylglycerols into free fatty acids and metabolises 2-arachidonoylglycerol into arachidonic acid, being thus the major source of pro-inflammatory prostaglandins in the liver. In this study, we investigated the role of MAGL in liver regeneration.MethodsHepatocyte proliferation was studied in vitro in hepatoma cell lines and ex vivo in precision-cut human liver slices. Liver regeneration was investigated in mice treated with a pharmacological MAGL inhibitor, MJN110, as well as in animals globally invalidated for MAGL (MAGL-/-) and specifically invalidated in hepatocytes (MAGLHep-/-) or myeloid cells (MAGLMye-/-). Two models of liver regeneration were used: acute toxic carbon tetrachloride injection and two-thirds partial hepatectomy. MAGLMye-/- liver macrophages profiling was analysed by RNA sequencing. A rescue experiment was performed by in vivo administration of interferon receptor antibody in MAGLMye-/- mice.ResultsPrecision-cut human liver slices from patients with chronic liver disease and human hepatocyte cell lines exposed to MJN110 showed reduced hepatocyte proliferation. Mice with global invalidation or mice treated with MJN110 showed blunted liver regeneration. Moreover, mice with specific deletion of MAGL in either hepatocytes or myeloid cells displayed delayed liver regeneration. Mechanistically, MAGLHep-/- mice showed reduced liver eicosanoid production, in particular prostaglandin E2 that negatively impacts on hepatocyte proliferation. MAGL inhibition in macrophages resulted in the induction of the type I interferon pathway. Importantly, neutralising the type I interferon pathway restored liver regeneration of MAGLMye-/- mice.ConclusionsOur data demonstrate that MAGL promotes liver regeneration by hepatocyte and macrophage reprogramming.Impact and implicationsBy using human liver samples and mouse models of global or specific cell type invalidation, we show that the monoacylglycerol pathway plays an essential role in liver regeneration. We unveil the mechanisms by which MAGL expressed in both hepatocytes and macrophages impacts the liver regeneration process, via eicosanoid production by hepatocytes and the modulation of the macrophage interferon pathway profile that restrains hepatocyte proliferation.

Dataset Information

Polyploid Hepatocytes Facilitate Adaptation and Regeneration to Chronic Liver Injury.

Publications

Polyploid Hepatocytes Facilitate Adaptation and Regeneration to Chronic Liver Injury.

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