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RAD51 knockout in murine liver (11-week)

ABSTRACT: RAD51 is a highly conserved DNA repair protein and is indispensable for the execution of homologous recombination, thereby participating in maintaining genomic stability. Since constitutive Rad51 knockout mice exhibit embryonic lethality, the physiological functions of RAD51, and the consequences of lacking it, are largely unknown. We herein demonstrated a critical role of RAD51 in postnatal liver development and regeneration. RAD51 is highly expressed during liver development and during regeneration following hepatectomy and hepatic injury, and is also elevated in liver-related diseases. We generated hepatocyte-specific Rad51 deletion mouse model (Rad51-CKO) to evaluate the function of RAD51 in liver development and regeneration.RAD51 deletion in postnatal hepatocytes results in aborted mitosis, global polyploidization, oxidative stress and cellular senescence. Remarkable liver fibrosis occurs as early as in 3-month-old Rad51fl/fl; Alb-Cre+/+ mice.The senescence-associated secretory phenotype in the livers of Rad51-CKO mice creates a niche that favors the activation and propagation of hepatic progenitor cells (HPCs) in which Rad51 is spared due to lack of Alb-Cre expression. The Rad51 functional HPCs and immature hepatocytes can thus proliferate vigorously, acquire increased malignancy, and eventually give rise to HCC. Our results thus demonstrate a novel function of RAD51 in liver development, homeostasis and tumorigenesis. The RAD51-CKO mice represent a unique genetic model for premature liver senescence, fibrosis, impaired regeneration and hepatocellular carcinogenesis.

ORGANISM(S): Mus musculus

PROVIDER: GSE243719 | GEO | 2025/01/22

REPOSITORIES: GEO

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Project description:Background: HGF/c-Met signaling plays a pivotal role in hepatocyte survival and tissue remodeling during liver regeneration. Treatment with HGF has been shown to accelerate resolution of fibrotic liver lesions in experimental animal models. To formally address the importance of c-Met signaling in hepatocytes in the context of chronic liver injury, we have used hepatocyte-specific Metfl/fl;Alb-Cre+/- conditional knockout mice (KO) and a model of liver fibrosis. Methods: CCl4 was administrated biweekly over a period of 4 weeks (injury phase), and the animals were followed over the next 4 weeks (healing phase). Macroscopic and microscopic changes during the injury and healing phases were monitored by IHC. Deposition of ECM was assessed by Sirius red staining and hydroxiproline content. Activation of hepatic stellate cells (HSC) was estimated by a-SMA using WB and IHC. Expression levels of the selected key fibrotic molecules were evaluated by RT-qPCR and WB. Time-dependent global transcriptomic changes from whole livers and isolated hepatocytes were examined using gene expression microarrays. Results: Loss of HGF/c-Met signaling in hepatocytes altered the hepatic microenvironment and dramatically aggravated hepatic fibrogenesis. Increased liver damage was associated with decreased hepatocyte proliferation, progressive accumulation of HSCs, and delayed fibrinolysis causing increased collagen deposit. Dystrophic calcification of necrotic areas impaired phagocytosis, resulting in sustained inflammatory and fibrogenic signaling further augmenting severity of fibrogenesis. Global gene-expression analysis demonstrated upregulation of key fibrogenic molecules, such as Tgf-Ã¢ and Pdgf-Ã¢, paralleled by a decreased expression of genes important for cell cycle, stress response and regeneration, which could be attributed to the c-Met deficiency in hepatocytes. Additionally, key chemotactic and inflammatory cytokines, including Ccl2, SDF1/Cxcr4 and Spp1, were upregulated in Metfl/fl;Alb-Cre+/- hepatocytes. However, the major pro-fibrotic signaling originated from the non-parenchymal cell compartments, as revealed by cell type-specific gene expression signatures. Conclusion: These results indicate that lack of c-Met signaling in hepatocytes disrupts the balance between extracellular matrix production and degradation and establish a protective role for c-Met against adverse microenvironment leading to the development of fibrotic liver disease. In the present study, we reported a detailed and comprehensive dynamic characterization of the cellular and molecular alterations involved in fibrosis in the liver of c-Met transgenic mice. Liver samples from female animals were collected at various time-points after fibrosis induction using CCL4 ranging from 0 weeks to 3 weeks. Tissue samples were divided into two parts; one was fixed in 10% formalin for histological evaluation and the other was used for RNA analysis.

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RAD51 knockout in murine liver (11-week)

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