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In vivo reprogramming drives dedifferentiation and enhances liver regeneration

ABSTRACT: Mammalian tissues have a limited regenerative capacity. Previous studies showed that dedifferentiation contributes to tissue regeneration in non-mammalian vertebrate species such as zebrafish and newt. However, dedifferentiation is rarely observed in mammalian tissues even in the neonatal stage and therefore artificial induction of dedifferentiation might enhance regeneration in mammalian tissues. Here we demonstrate that short-term expression of Yamanaka 4 factors (4F) induces dedifferentiation and proliferation in the liver by using lineage-traceable, hepatocyte-specific 4F inducible mouse model. Global transcriptome analysis shows that 4F expression transiently reduces the expression of hepatic-lineage markers and induces the expression of a large set of proliferative markers and epigenetic modifiers along with global epigenetic changes as assessed by DNA-accessibility analysis. More importantly, lineage-tracing experiments showed that 4F-expressing hepatocytes acquire liver stem/progenitor cell markers, suggesting that 4F induces partial reprogramming. Moreover, 4F enhances MyoD-mediated transdifferentiation in the liver, suggesting that 4F endows hepatocytes with plasticity. Lastly, 4F expression attenuated liver injury associated with more proliferative capacity and better survival rate, indicating that 4F enhances liver regeneration. Taken together, these results demonstrate that liver-specific 4F expression induces dedifferentiation and promotes liver regeneration.

ORGANISM(S): Mus musculus

PROVIDER: GSE144600 | GEO | 2022/04/27

REPOSITORIES: GEO

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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.

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In vivo reprogramming drives dedifferentiation and enhances liver regeneration

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