-
Military Medical Research Feb 2021Toll-like receptor 5 (TLR5)-mediated pathways play critical roles in regulating the hepatic immune response and show hepatoprotective effects in mouse models of hepatic...
BACKGROUND
Toll-like receptor 5 (TLR5)-mediated pathways play critical roles in regulating the hepatic immune response and show hepatoprotective effects in mouse models of hepatic diseases. However, the role of TLR5 in experimental models of liver regeneration has not been reported. This study aimed to investigate the role of TLR5 in partial hepatectomy (PHx)-induced liver regeneration.
METHODS
We performed 2/3 PHx in wild-type (WT) mice, TLR5 knockout mice, or TLR5 agonist CBLB502 treated mice, as a model of liver regeneration. Bacterial flagellin content was measured with ELISA, and hepatic TLR5 expression was determined with quantitative PCR analyses and flow cytometry. To study the effects of TLR5 on hepatocyte proliferation, we analyzed bromodeoxyuridine (BrdU) incorporation and proliferating cell nuclear antigen (PCNA) expression with immunohistochemistry (IHC) staining. The effects of TLR5 during the priming phase of liver regeneration were examined with quantitative PCR analyses of immediate early gene mRNA levels, and with Western blotting analysis of hepatic NF-κB and STAT3 activation. Cytokine and growth factor production after PHx were detected with real-time PCR and cytometric bead array (CBA) assays. Oil Red O staining and hepatic lipid concentrations were analyzed to examine the effect of TLR5 on hepatic lipid accumulation after PHx.
RESULTS
The bacterial flagellin content in the serum and liver increased, and the hepatic TLR5 expression was significantly up-regulated in WT mice after PHx. TLR5-deficient mice exhibited diminished numbers of BrdU- and PCNA-positive cells, suppressed immediate early gene expression, and decreased cytokine and growth factor production. Moreover, PHx-induced hepatic NF-κB and STAT3 activation was inhibited in Tlr5 mice, as compared with WT mice. Consistently, the administration of CBLB502 significantly promoted PHx-mediated hepatocyte proliferation, which was correlated with enhanced production of proinflammatory cytokines and the recruitment of macrophages and neutrophils in the liver. Furthermore, Tlr5 mice displayed significantly lower hepatic lipid concentrations and smaller Oil Red O positive areas than those in control mice after PHx.
CONCLUSION
We reveal that TLR5 activation contributes to the initial events of liver regeneration after PHx. Our findings demonstrate that TLR5 signaling positively regulates liver regeneration and suggest the potential of TLR5 agonist to promote liver regeneration.
Topics: Animals; Disease Models, Animal; Liver Regeneration; Mice; Mice, Inbred C57BL; Signal Transduction; Statistics, Nonparametric; Toll-Like Receptor 5
PubMed: 33622404
DOI: 10.1186/s40779-021-00309-4 -
Seminars in Thrombosis and Hemostasis Sep 2020The liver is unique in its remarkable regenerative capacity, which enables the use of liver resection as a treatment for specific liver diseases, including removal of... (Review)
Review
The liver is unique in its remarkable regenerative capacity, which enables the use of liver resection as a treatment for specific liver diseases, including removal of neoplastic liver disease. After resection, the remaining liver tissue (i.e, liver remnant) regenerates to maintain normal hepatic function. In experimental settings as well as patients, removal of up to two-thirds of the liver mass stimulates a rapid and highly coordinated process resulting in the regeneration of the remaining liver. Mechanisms controlling the initiation and termination of regeneration continue to be discovered, and many of the fundamental signaling pathways controlling the proliferation of liver parenchymal cells (i.e., hepatocytes) have been uncovered. Interestingly, while hemostatic complications (i.e., bleeding and thrombosis) are primarily thought of as a complication of surgery itself, strong evidence suggests that components of the hemostatic system are, in fact, powerful drivers of liver regeneration. This review focuses on the clinical and translational evidence supporting a link between the hemostatic system and liver regeneration, and the mechanisms whereby the hemostatic system directs liver regeneration discovered using experimental settings.
Topics: Hemostasis; Humans; Liver Diseases; Liver Regeneration
PubMed: 32906177
DOI: 10.1055/s-0040-1715450 -
Signal Transduction and Targeted Therapy Sep 2023The mineral dust-induced gene (MDIG) comprises a conserved JmjC domain and has the ability to demethylate histone H3 lysine 9 trimethylation (H3K9me3). Previous studies...
The mineral dust-induced gene (MDIG) comprises a conserved JmjC domain and has the ability to demethylate histone H3 lysine 9 trimethylation (H3K9me3). Previous studies have indicated the significance of MDIG in promoting cell proliferation by modulating cell-cycle transition. However, its involvement in liver regeneration has not been extensively investigated. In this study, we generated mice with liver-specific knockout of MDIG and applied partial hepatectomy or carbon tetrachloride mouse models to investigate the biological contribution of MDIG in liver regeneration. The MDIG levels showed initial upregulation followed by downregulation as the recovery progressed. Genetic MDIG deficiency resulted in dramatically impaired liver regeneration and delayed cell cycle progression. However, the MDIG-deleted liver was eventually restored over a long latency. RNA-seq analysis revealed Myc as a crucial effector downstream of MDIG. However, ATAC-seq identified the reduced chromatin accessibility of OTX2 locus in MDIG-ablated regenerating liver, with unaltered chromatin accessibility of Myc locus. Mechanistically, MDIG altered chromatin accessibility to allow transcription by demethylating H3K9me3 at the OTX2 promoter region. As a consequence, the transcription factor OTX2 binding at the Myc promoter region was decreased in MDIG-deficient hepatocytes, which in turn repressed Myc expression. Reciprocally, Myc enhanced MDIG expression by regulating MDIG promoter activity, forming a positive feedback loop to sustain hepatocyte proliferation. Altogether, our results prove the essential role of MDIG in facilitating liver regeneration via regulating histone methylation to alter chromatin accessibility and provide valuable insights into the epi-transcriptomic regulation during liver regeneration.
Topics: Animals; Mice; Liver Regeneration; Cell Proliferation; Chromatin; Liver; Demethylation
PubMed: 37709738
DOI: 10.1038/s41392-023-01575-5 -
Nature Communications Jan 2021Induction of intrinsic liver regeneration is an unmet need that can be achieved by temporally activating key hepatocyte regenerative pathways. Here, we establish an...
Induction of intrinsic liver regeneration is an unmet need that can be achieved by temporally activating key hepatocyte regenerative pathways. Here, we establish an efficient, safe, non-integrative method to transiently express hepatocyte-growth-factor (HGF) and epidermal-growth-factor (EGF) in hepatocytes via nucleoside-modified, lipid-nanoparticle-encapsulated mRNA (mRNA-LNP) delivery in mice. We confirm specific hepatotropism of mRNA-LNP via intravenous injection of firefly luciferase encoding mRNA-LNP, with protein expression lasting about 3 days. In the liver, virtually all hepatocytes are transfected along with a subpopulation of endothelial and Kupffer cells. In homeostasis, HGF mRNA-LNP efficiently induce hepatocyte proliferation. In a chronic liver injury mouse model recapitulating non-alcoholic fatty liver disease, injections of both HGF and EGF mRNA-LNP sharply reverse steatosis and accelerate restoration of liver function. Likewise, HGF and EGF mRNA-LNP accelerate liver regeneration after acetaminophen-induced acute liver injury with rapid return to baseline ALT levels. This study introduces mRNA-LNP as a potentially translatable safe therapeutic intervention to harness liver regeneration via controlled expression of endogenous mitogens in vivo.
Topics: Acetaminophen; Animals; Cell Proliferation; Chronic Disease; Disease Models, Animal; Epidermal Growth Factor; Female; Green Fluorescent Proteins; Hepatocyte Growth Factor; Hepatocytes; Homeostasis; Injections; Lipids; Liver; Liver Function Tests; Liver Regeneration; Mice, Inbred C57BL; Nanoparticles; Nucleosides; RNA, Messenger; Mice
PubMed: 33504774
DOI: 10.1038/s41467-021-20903-3 -
Hepatology (Baltimore, Md.) Aug 2018Liver sinusoidal endothelial cells (LSECs) critically regulate liver homeostasis and diseases through angiocrine factors. Notch is critical in endothelial cells (ECs)....
UNLABELLED
Liver sinusoidal endothelial cells (LSECs) critically regulate liver homeostasis and diseases through angiocrine factors. Notch is critical in endothelial cells (ECs). In the current study, Notch signaling was activated by inducible EC-specific expression of the Notch intracellular domain (NIC). We found that endothelial Notch activation damaged liver homeostasis. Notch activation resulted in decreased fenestration and increased basement membrane, and a gene expression profile with decreased LSEC-associated genes and increased continuous EC-associated genes, suggesting LSEC dedifferentiation. Consistently, endothelial Notch activation enhanced hepatic fibrosis (HF) induced by CCl . Notch activation attenuated endothelial nitric oxide synthase (eNOS)/soluble guanylate cyclase (sGC) signaling, and activation of sGC by 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole (YC-1) reversed the dedifferentiation phenotype. In addition, Notch activation subverted the hepatocyte-supporting angiocrine profile of LSECs by down-regulating critical hepatocyte mitogens, including Wnt2a, Wnt9b, and hepatocyte growth factor (HGF). This led to compromised hepatocyte proliferation under both quiescent and regenerating conditions. Whereas expression of Wnt2a and Wnt9b was dependent on eNOS-sGC signaling, HGF expression was not rescued by the sGC activator, suggesting heterogeneous mechanisms of LSECs to maintain hepatocyte homeostasis.
CONCLUSION
Endothelial Notch activation results in LSEC dedifferentiation and accelerated liver fibrogenesis through eNOS-sGC signaling, and alters the angiocrine profile of LSECs to compromise hepatocyte proliferation and liver regeneration (LR). (Hepatology 2018).
Topics: Animals; Blotting, Western; Cell Culture Techniques; Cell Proliferation; Endothelial Cells; Enzyme-Linked Immunosorbent Assay; Gene Expression Profiling; Hepatocytes; Liver; Liver Cirrhosis; Liver Regeneration; Male; Mice; Mice, Inbred C57BL; Real-Time Polymerase Chain Reaction; Receptors, Notch; Signal Transduction
PubMed: 29420858
DOI: 10.1002/hep.29834 -
Experimental & Molecular Medicine Aug 2020The liver is a highly regenerative organ, but its regenerative capacity is compromised in severe liver diseases. Hepatocyte-driven liver regeneration that involves the... (Review)
Review
The liver is a highly regenerative organ, but its regenerative capacity is compromised in severe liver diseases. Hepatocyte-driven liver regeneration that involves the proliferation of preexisting hepatocytes is a primary regeneration mode. On the other hand, liver progenitor cell (LPC)-driven liver regeneration that involves dedifferentiation of biliary epithelial cells or hepatocytes into LPCs, LPC proliferation, and subsequent differentiation of LPCs into hepatocytes is a secondary mode. This secondary mode plays a significant role in liver regeneration when the primary mode does not effectively work, as observed in severe liver injury settings. Thus, promoting LPC-driven liver regeneration may be clinically beneficial to patients with severe liver diseases. In this review, we describe the current understanding of LPC-driven liver regeneration by exploring current knowledge on the activation, origin, and roles of LPCs during regeneration. We also describe animal models used to study LPC-driven liver regeneration, given their potential to further deepen our understanding of the regeneration process. This understanding will eventually contribute to developing strategies to promote LPC-driven liver regeneration in patients with severe liver diseases.
Topics: Animals; Cell Differentiation; Hepatocytes; Humans; Liver; Liver Regeneration; Models, Biological; Stem Cells
PubMed: 32796957
DOI: 10.1038/s12276-020-0483-0 -
Proceedings of the National Academy of... Jul 2022The Hippo signaling pathway acts as a brake on regeneration in many tissues. This cascade of kinases culminates in the phosphorylation of the transcriptional cofactors...
The Hippo signaling pathway acts as a brake on regeneration in many tissues. This cascade of kinases culminates in the phosphorylation of the transcriptional cofactors Yap and Taz, whose concentration in the nucleus consequently remains low. Various types of cellular signals can reduce phosphorylation, however, resulting in the accumulation of Yap and Taz in the nucleus and subsequently in mitosis. We earlier identified a small molecule, TRULI, that blocks the final kinases in the pathway, Lats1 and Lats2, and thus elicits proliferation of several cell types that are ordinarily postmitotic and aids regeneration in mammals. In the present study, we present the results of chemical modification of the original compound and demonstrate that a derivative, TDI-011536, is an effective blocker of Lats kinases in vitro at nanomolar concentrations. The compound fosters extensive proliferation in retinal organoids derived from human induced pluripotent stem cells. Intraperitoneal administration of the substance to mice suppresses Yap phosphorylation for several hours and induces transcriptional activation of Yap target genes in the heart, liver, and skin. Moreover, the compound initiates the proliferation of cardiomyocytes in adult mice following cardiac cryolesions. After further chemical refinement, related compounds might prove useful in protective and regenerative therapies.
Topics: Animals; Cell Proliferation; Heart; Humans; Induced Pluripotent Stem Cells; Liver Regeneration; Mice; Organoids; Phosphorylation; Protein Kinase Inhibitors; Protein Serine-Threonine Kinases; Regeneration; Retina; Skin Physiological Phenomena; Transcription, Genetic; Transcriptional Activation; YAP-Signaling Proteins
PubMed: 35867764
DOI: 10.1073/pnas.2206113119 -
Aging Mar 2020
Topics: Hepatocytes; Homeostasis; Humans; Liver; Liver Regeneration
PubMed: 32205468
DOI: 10.18632/aging.102957 -
Genes & Development Apr 2020The mammalian liver possesses a unique capacity for regeneration. However, this regenerative potential declines with age due to unknown mechanisms. In this issue of ,... (Review)
Review
The mammalian liver possesses a unique capacity for regeneration. However, this regenerative potential declines with age due to unknown mechanisms. In this issue of , Ritschka and colleagues (pp. 489-494). compare liver regeneration upon partial hepatectomy in young and adult mice. Partial hepatectomy causes a transient increase in p21 in a subpopulation of hepatocytes that persists in adult mice. Remarkably, treatment with the BCL-2 family inhibitor ABT-737 blunts p21 expression, enhancing liver regeneration.
Topics: Animals; Hepatectomy; Hepatocytes; Liver; Liver Regeneration; Mice
PubMed: 32238449
DOI: 10.1101/gad.337394.120 -
Journal of Molecular Cell Biology Aug 2020Understanding the development, regeneration, and disorders of the liver is the major goal in liver biology. Current mechanistic knowledge of human livers has been... (Review)
Review
Understanding the development, regeneration, and disorders of the liver is the major goal in liver biology. Current mechanistic knowledge of human livers has been largely derived from mouse models and cell lines, which fall short in recapitulating the features of human liver cells or the structures and functions of human livers. Organoids as an in vitro system hold the promise to generate organ-like tissues in a dish. Recent advances in human liver organoids also facilitate the understanding of the biology and diseases in this complex organ. Here we review the progress in human liver organoids, mainly focusing on the methods to generate liver organoids, their applications, and possible future directions.
Topics: Cell Differentiation; Humans; Liver; Liver Regeneration; Models, Biological; Organoids; Regenerative Medicine
PubMed: 32236564
DOI: 10.1093/jmcb/mjaa013