Partial hepatectomy in mice

2,3,5,4'-tetrahydroxy-stilbene-2-O-β-D-glucoside promotes liver regeneration after partial hepatectomy in mice: The potential involvement of PPARα-mediated fatty acid metabolism

ETHNOPHARMACOLOGICAL RELEVANCE

2,3,5,4'-tetrahydroxy-stilbene-2-O-β-D-glucoside (TSG) is the principal bioactive compound contained in Polygonum multiflorum Thunb. (PMT), which is traditionally recorded to possess tonic and anti-aging efficacy.

AIM OF THE STUDY

To identify the TSG-provided promotion on liver regeneration (LR) following partial hepatectomy (PHx) in mice and to explicate its involved mechanism.

MATERIALS AND METHODS

The promotion of TSG on LR was evaluated by hematoxylin and eosin (H&E), 5-bromodeoxyuridinc (BrdU) and Ki-67 staining, and measuring the level of proliferating cell nuclear antigen (PCNA) and Cyclin D1 in mice with PHx at different time points. Gene Expression Omnibus (GEO, GSE15239) database and the label-free quantitative proteomics from liver of mice at 24 h after PHx were integrated to identify potential involved critical proteins, which were verified by Western-blot, Real-time polymerase chain reaction (RT-PCR), molecular docking and luciferase activity assay. Primary hepatocytes isolated from mice were used to investigate the TSG-provided promotion on proliferation in vitro.

RESULTS

TSG (20 mg/kg) promoted LR in mice after PHx. Results from RNA expression data from clinical samples and proteomic analysis from liver tissues indicated that peroxisome proliferator-activated receptor α (PPARα)-mediated fatty acid metabolism pathway were crucially associated with the TSG-provided promotion on LR. TSG enhanced the nuclear translocation of PPARα and the mRNA expression of a series of PPARα-regulated downstream genes. In addition, TSG lowered hepatic triglyceride (TG) and non-esterified fatty acid (NEFA) amounts and increased hepatic adenosine triphosphate (ATP) level in mice after PHx. TSG up-regulated the transcriptional activity of PPARα in vitro. Next results displayed that TSG promoted cell proliferation as well as ATP level in mice primary hepatocytes, which were abolished when PPARα was suppressed. Meanwhile, the cell viability was also elevated in mice primary hepatocytes treated with ATP.

CONCLUSION

Activating PPARα-mediated fatty acid β-oxidation (FAO) pathway led to the production of ATP, which contributed to the TSG-provided promotion on LR after PHx in mice.

Liver-specific Mettl14 deletion induces nuclear heterotypia and dysregulates RNA export machinery

Modification of RNA with N6-methyladenosine (m6A) has gained attention in recent years as a general mechanism of gene regulation. In the liver, m6A, along with its associated machinery, has been studied as a potential biomarker of disease and cancer, with impacts on metabolism, cell cycle regulation, and pro-cancer state signaling. However these observational data have yet to be causally examined in vivo. For example, neither perturbation of the key m6A writers Mettl3 and Mettl14, nor the m6A readers Ythdf1 and Ythdf2 have been thoroughly mechanistically characterized in vivo as they have been in vitro. To understand the functions of these machineries, we developed mouse models and found that deleting Mettl14 led to progressive liver injury characterized by nuclear heterotypia, with changes in mRNA splicing, processing and export leading to increases in mRNA surveillance and recycling.

First-in-class MKK4 inhibitors enhance liver regeneration and prevent liver failure

Diminished hepatocyte regeneration is a key feature of acute and chronic liver diseases and after extended liver resections, resulting in the inability to maintain or restore a sufficient functional liver mass. Therapies to restore hepatocyte regeneration are lacking, making liver transplantation the only curative option for end-stage liver disease. Here, we report on the structure-based development and characterization (nuclear magnetic resonance [NMR] spectroscopy) of first-in-class small molecule inhibitors of the dual-specificity kinase MKK4 (MKK4i). MKK4i increased liver regeneration upon hepatectomy in murine and porcine models, allowed for survival of pigs in a lethal 85% hepatectomy model, and showed antisteatotic and antifibrotic effects in liver disease mouse models. A first-in-human phase I trial (European Union Drug Regulating Authorities Clinical Trials [EudraCT] 2021-000193-28) with the clinical candidate HRX215 was conducted and revealed excellent safety and pharmacokinetics. Clinical trials to probe HRX215 for prevention/treatment of liver failure after extensive oncological liver resections or after transplantation of small grafts are warranted.

Coagulation factor XIII is a critical driver of liver regeneration after partial hepatectomy

BACKGROUND

Activation of coagulation and fibrin deposition in the regenerating liver appears to promote adequate liver regeneration in mice. In humans, perioperative hepatic fibrin deposition is reduced in patients who develop liver dysfunction after partial hepatectomy (PHx), but the mechanism underlying reduced fibrin deposition in these patients is unclear.

METHODS AND RESULTS

Hepatic deposition of cross-linked (ie, stabilized) fibrin was evident in livers of mice after two-thirds PHx. Interestingly, hepatic fibrin cross-linking was dramatically reduced in mice after 90% PHx, an experimental setting of failed liver regeneration, despite similar activation of coagulation after two-thirds or 90% PHx. Likewise, intraoperative activation of coagulation was not reduced in patients who developed liver dysfunction after PHx. Preoperative fibrinogen plasma concentration was not connected to liver dysfunction after PHx in patients. Rather, preoperative and postoperative plasma activity of the transglutaminase coagulation factor (F)XIII, which cross-links fibrin, was lower in patients who developed liver dysfunction than in those who did not. PHx-induced hepatic fibrin cross-linking and hepatic platelet accumulation were significantly reduced in mice lacking the catalytic subunit of FXIII (FXIII-/- mice) after two-thirds PHx. This was coupled with a reduction in both hepatocyte proliferation and liver-to-body weight ratio as well as an apparent reduction in survival after two-thirds PHx in FXIII-/- mice.

CONCLUSION

The results indicate that FXIII is a critical driver of liver regeneration after PHx and suggest that perioperative plasma FXIII activity may predict posthepatectomy liver dysfunction. The results may inform strategies to stabilize proregenerative fibrin during liver resection.

Durable and efficient gene silencing in vivo by hit-and-run epigenome editing

Permanent epigenetic silencing using programmable editors equipped with transcriptional repressors holds great promise for the treatment of human diseases1-3. However, to unlock its full therapeutic potential, an experimental confirmation of durable epigenetic silencing after the delivery of transient delivery of editors in vivo is needed. To this end, here we targeted Pcsk9, a gene expressed in hepatocytes that is involved in cholesterol homeostasis. In vitro screening of different editor designs indicated that zinc-finger proteins were the best-performing DNA-binding platform for efficient silencing of mouse Pcsk9. A single administration of lipid nanoparticles loaded with the editors' mRNAs almost halved the circulating levels of PCSK9 for nearly one year in mice. Notably, Pcsk9 silencing and accompanying epigenetic repressive marks also persisted after forced liver regeneration, further corroborating the heritability of the newly installed epigenetic state. Improvements in construct design resulted in the development of an all-in-one configuration that we term evolved engineered transcriptional repressor (EvoETR). This design, which is characterized by a high specificity profile, further reduced the circulating levels of PCSK9 in mice with an efficiency comparable with that obtained through conventional gene editing, but without causing DNA breaks. Our study lays the foundation for the development of in vivo therapeutics that are based on epigenetic silencing.

Decoding aging-dependent regenerative decline across tissues at single-cell resolution

Regeneration across tissues and organs exhibits significant variation throughout the body and undergoes a progressive decline with age. To decode the relationships between aging and regenerative capacity, we conducted a comprehensive single-cell transcriptome analysis of regeneration in eight tissues from young and aged mice. We employed diverse analytical models to study tissue regeneration and unveiled the intricate cellular and molecular mechanisms underlying the attenuated regenerative processes observed in aged tissues. Specifically, we identified compromised stem cell mobility and inadequate angiogenesis as prominent contributors to this age-associated decline in regenerative capacity. Moreover, we discovered a unique subset of Arg1+ macrophages that were activated in young tissues but suppressed in aged regenerating tissues, suggesting their important role in age-related immune response disparities during regeneration. This study provides a comprehensive single-cell resource for identifying potential targets for interventions aimed at enhancing regenerative outcomes in the aging population.

The spleen as a possible source of serine protease inhibitors and migrating monocytes required for liver regeneration after 70% resection in mice

Introduction: The role of the immune system in liver repair is fundamentally complex and most likely involves the spleen. The close connection between the two organs via the portal vein enables delivery of splenic cytokines and living cells to the liver. This study evaluates expression of inflammation-related genes and assesses the dynamics of monocyte-macrophage and lymphocyte populations of the spleen during the recovery from 70% hepatectomy in mice. Methods: The study used the established mouse model of 70% liver volume resection. The animals were sacrificed 24 h, 72 h or 7 days post-intervention and splenic tissues were collected for analysis: Clariom™ S transcriptomic assay, immunohistochemistry for proliferation marker Ki-67 and macrophage markers, and flow cytometry for lymphocyte and macrophage markers. Results: The loss and regeneration of 70% liver volume affected the cytological architecture and gene expression profiles of the spleen. The tests revealed significant reduction in cell counts for Ki-67+ cells and CD115+ macrophages on day 1, Ly6C + cells on days 1, 3 and 7, and CD3+CD8+ cytotoxic lymphocytes on day 7. The transcriptomic analysis revealed significant activation of protease inhibitor genes Serpina3n, Stfa2 and Stfa2l1 and decreased expression of cell cycle regulatory genes on day 1, mirrored by inverse dynamics observed on day 7. Discussion and conclusion: Splenic homeostasis is significantly affected by massive loss in liver volume. High levels of protease inhibitors indicated by increased expression of corresponding genes on day 1 may play an anti-inflammatory role upon reaching the regenerating liver via the portal vein. Leukocyte populations of the spleen react by a slow-down in proliferation. A transient decrease in the local CD115+ and Ly6C+ cell counts may indicate migration of splenic monocytes-macrophages to the liver.

Axon guidance genes control hepatic artery development

Earlier data on liver development demonstrated that morphogenesis of the bile duct, portal mesenchyme and hepatic artery is interdependent, yet how this interdependency is orchestrated remains unknown. Here, using 2D and 3D imaging, we first describe how portal mesenchymal cells become organised to form hepatic arteries. Next, we examined intercellular signalling active during portal area development and found that axon guidance genes are dynamically expressed in developing bile ducts and portal mesenchyme. Using tissue-specific gene inactivation in mice, we show that the repulsive guidance molecule BMP co-receptor A (RGMA)/neogenin (NEO1) receptor/ligand pair is dispensable for portal area development, but that deficient roundabout 2 (ROBO2)/SLIT2 signalling in the portal mesenchyme causes reduced maturation of the vascular smooth muscle cells that form the tunica media of the hepatic artery. This arterial anomaly does not impact liver function in homeostatic conditions, but is associated with significant tissular damage following partial hepatectomy. In conclusion, our work identifies new players in development of the liver vasculature in health and liver regeneration.

Dual phenotypic characteristics of P-selectin in a mouse model of hemorrhagic shock and hepatectomy

BACKGROUND

Membrane-bound P-selectin induces endothelial adhesion of leucocytes and amplifies organ inflammations during major trauma, while soluble P-selectin (sP-sel) mediates survival rescue properties. This study characterized the differential effects of P-selectin in a "2-hit" model of hemorrhagic shock (HS) and partial hepatectomy (PH).

MATERIALS AND METHODS

HS was induced by withdrawing blood (0.3 mL) directly from the mouse femoral arteries. 70% or 50% of liver volumes were resected after inducing HS. Time of survival in P-selectin deficient (Selp -/-) mice treated with and without intraperitoneal injections of recombinant P-sel IgG-Fc fusion proteins (rP-sel-Fc, 1.5 mg/kg) were recorded for up to 72h after injury. In addition, liver regeneration at 72h after HS and 50% PH was assessed in wild-type and Selp -/- mice.

RESULTS

Compared to wild-types, Selp -/- mice had significantly higher mortality rates post HS and 70% PH, as none of these animals survived up to 48h postoperatively. The survival curve was restored in Selp -/- mice pre-treated with rP-sel-Fc. In the HS followed by 50% PH experimental arm, liver remnant growth ratios were significantly higher in Selp -/- mice (15.7 ± 3.1 vs 11.7 ± 4.9, P = 0.040). The elevated serum concentrations of alanine aminotransferase post-PH were significantly reduced in Selp -/- mice. Hepatocyte proliferation indices (CYP7a1 and PCNA) expression were enhanced and myeloperoxidase activity in the regenerated remnant liver was reduced in the Selp -/- mice.

CONCLUSION

In critical conditions induced by HS and PH, P-selectin mediates two distinct phenotypic characteristics. Soluble-form circulating P-selectin improves survival in the acute stage of HS and extensive loss of liver parenchyma; membrane-bound P-selectin induces regional pro-inflammatory reactions in the remnant liver after the acute stage of two insults, thereby inhibiting hepatic regeneration. The results of this pre-clinical study may provide molecular mechanistic insight and clinical therapeutic applications of P-selectin in the acute and regenerative phases of traumatic hepatic injury.

Translational Control of Metabolism and Cell Cycle Progression in Hepatocellular Carcinoma

The liver is a metabolic hub characterized by high levels of protein synthesis. Eukaryotic initiation factors, eIFs, control the first phase of translation, initiation. Initiation factors are essential for tumor progression and, since they regulate the translation of specific mRNAs downstream of oncogenic signaling cascades, may be druggable. In this review, we address the issue of whether the massive translational machinery of liver cells contributes to liver pathology and to the progression of hepatocellular carcinoma (HCC); it represents a valuable biomarker and druggable target. First, we observe that the common markers of HCC cells, such as phosphorylated ribosomal protein S6, belong to the ribosomal and translational apparatus. This fact is in agreement with observations that demonstrate a huge amplification of the ribosomal machinery during the progression to HCC. Some translation factors, such as eIF4E and eIF6, are then harnessed by oncogenic signaling. In particular, the action of eIF4E and eIF6 is particularly important in HCC when driven by fatty liver pathologies. Indeed, both eIF4E and eIF6 amplify at the translational level the production and accumulation of fatty acids. As it is evident that abnormal levels of these factors drive cancer, we discuss their therapeutic value.

Key hepatoprotective roles of mitochondria in liver regeneration

Treatment of advanced liver disease using surgical modalities is possible due to the liver's innate ability to regenerate following resection. Several key cellular events in the regenerative process converge at the mitochondria, implicating their crucial roles in liver regeneration. Mitochondria enable the regenerating liver to meet massive metabolic demands by coordinating energy production to drive cellular proliferative processes and vital homeostatic functions. Mitochondria are also involved in terminating the regenerative process by mediating apoptosis. Studies have shown that attenuation of mitochondrial activity results in delayed liver regeneration, and liver failure following resection is associated with mitochondrial dysfunction. Emerging mitochondria therapy (i.e., mitotherapy) strategies involve isolating healthy donor mitochondria for transplantation into diseased organs to promote regeneration. This review highlights mitochondria's inherent role in liver regeneration.

Can endocan serve as a molecular "hepatostat" in liver regeneration?

BACKGROUND

Intriguingly, liver regeneration after injury does not induce uncontrolled growth and the underlying mechanisms of such a "hepatostat" are still not clear. Endocan, a proteoglycan, was implicated in liver regeneration. It can support the function of hepatocyte growth factor/scatter factor in tissue repair after injury. Endostatin, a 20 kDa C-terminal fragment of collagen XVIII, may modulate the cessation of liver regeneration. eEF2K, a protein kinase that regulates protein synthesis, can regulate angiogenesis. Thus, we investigated the role of endocan, endostatin and eEF2K during normal liver regeneration.

METHODS

Serum samples and regenerating remnant liver tissues were obtained on various days after partial hepatectomy in rats. mRNA expression levels of Vegf and Pcna were analyzed in addition to immunohistochemical evaluations. Liver tissue protein levels of endostatin, endocan and p-eEF2K/eEF2K were determined with Western blot. Serum levels of endostatin and endocan were assessed with ELISA.

RESULTS

Pcna expression level in residual liver tissues peaked on day-1, while Vegf expression reached its highest level on days 1-3 after partial hepatectomy (70%). Endocan activity declined gradually on days 1-7. The decrease in liver endocan expression was accompanied by an increase in serum endocan levels. Partial hepatectomy induced a rapid increase in liver endostatin levels. Following its surge on day-1, endostatin expression gradually declined, which was accompanied by a peak in serum endostatin. Finally, partial hepatectomy was shown to regulate eEF2K; thus, increasing protein translation.

CONCLUSIONS

We revealed possible mechanistic insights into liver regeneration by examining the associations of Pcna, Vegf, endocan, endostatin, eEF2K with hepatic regeneration after partial hepatectomy. Indeed, endocan might serve as a useful biomarker to monitor clinical prognosis in a plethora of conditions such as recovery of donor's remaining liver after living-donor liver transplant. Whether endocan might represent a strategy to optimize liver regeneration when given therapeutically needs to be investigated in future studies.

Series of Intravoxel Incoherent Motion and T2* Magnetic Resonance Imaging Mapping in Detection of Liver Perfusion Changes and Regeneration Among Partial Hepatectomy in Sprague-Dawley Rats

RATIONALE AND OBJECTIVES

To evaluate liver perfusion changes and their effect on liver regeneration (LR) after partial hepatectomy (PH) using intravoxel incoherent motion (IVIM) and T2* mapping in a rat model.

METHODS

One hundred and two rats underwent 30%, 50%, or 70% PH. Within each group (n = 34), rats in MR imaging subgroup (n = 10) underwent liver IVIM and T2* mapping before and within 2 h, 1, 2, 3, 5, 7, 14, and 21 days post-PH to measure D*, perfusion fraction (PF), and T2* values. Three rats from histologic subgroup (n = 24) sacrificed at each time point for hepatocyte Ki-67 indices and diameters measurement.

RESULTS

Liver D* and PF values decreased immediately post-PH, then returned to original level as LR progressed in all groups. PF values in 70% PH group were significantly lower than in the other two groups (p < .05). D* and PF values correlated significantly with hepatocyte Ki-67 indices (r =  -0.588 to -0.915; p < .05) and hepatocyte diameter (r  = -0.555 to -0.792; p < .05). Liver T2* values decreased immediately within 2 h post-PH, then increased to a high level and followed with returning to original level gradually. The duration of the high T2* levels was consistent with Ki-67 indices.

CONCLUSIONS

Liver perfusion decreased immediately followed with increasing gradually after PH. IVIM and T2* mapping are promising methods for monitoring changes of liver perfusion. IVIM-derived D* value is the best indicator in reflecting the process of LR noninvasively.

Effect of Curcumin on Interleukin-6 Expression and Malondialdehyde Levels in Liver Fibrosis

BACKGROUND: Chronic inflammation and excessive oxidative stress are the main mechanisms causing liver fibrosis. It releases anti-inflammatory cytokines, namely, interleukin 6 (IL-6), nitric oxide, and malondialdehyde (MDA). Curcumin acts as an anti-inflammatory, antioxidant, and antifibrotic. AIM: This study is aimed to analyze differences in IL-6 expression and MDA levels in (Deutschland, Denken, and Yoken) DDY mice with liver fibrosis after common bile duct ligation between the curcumin-treated and control groups. METHODS: This research is an experimental study with a post-test-only control group design. Seventy-five male DDY mice 20–30g were used in this study (n = 5). Mice were randomly divided into five groups, each consisting of 15 mice. The first group healthy control (HC) was the HC group given phosphate-buffered saline (PBS) solution and did not perform the CBDL. The second group negative control (NC) was a NC group given PBS solution and completed the CBDL. The third group positive control (PC) was a PC group given oral ursodeoxycholic acid (UDCA) and performed CBDL. The fourth group (P1) was assigned oral curcumin and performed the CBDL. The fifth group (P2) was given oral curcumin and UDCA and performed the CBDL. Seven, fourteen, and 21 days after ligation, liver samples were taken to examine IL-6 expression and MDA levels. RESULTS: There was a significant difference between the NC and PC groups (p = 0.00), NC and P1 (p = 0.00), NC with P2 (p = 0.00), PC with P1 (p = 0.04), PC with P2 (p = 0.04), on day 21 between the NC and PC groups (p = 0.00), NC with P1 (p = 0.00), and PC with P2 (p = 0.00). Statistical analysis of the comparison of MDA levels on days 7 and 14 found no significant difference. On day 21, there was a substantial difference between the NC group and P1 (p = 0.02). CONCLUSION: This study concluded that curcumin effectively reduced IL-6 expression and MDA levels in liver fibrosis.

Multi-parametric magnetic resonance imaging of liver regeneration in a standardized partial hepatectomy rat model

Background

We aimed to evaluate the correlation between the pathological changes and multi-parameter MRI characteristics of liver regeneration (LR) in a standard partial hepatectomy (PH) rat model.

Methods

Seventy Sprague–Dawley rats were randomly divided into two groups: MR scan group (n = 14) and pathologic analysis (PA) group (n = 56). All 14 rats in the MR group underwent liver T1 mapping, T2 mapping, and diffusion kurtosis imaging before and the 1st, 2nd, 3rd, 5th, 7th, 14th, and 21st day after 70% hepatectomy. Seven rats in the PA group were euthanized at each time point to determine Ki-67 indices, hepatocyte size (HTS), steatosis grade, and inflammation score.

Results

Liver T1 and T2 values increased to maximum on day 2 (P < 0.001 vs. baseline), D and K values decreased to minimum on day 3 and 2, respectively (P < 0.001 vs. baseline), then all parameters returned to baseline gradually. Hepatocyte Ki-67, hepatocyte size, steatosis grade, and inflammation score initially increased after surgery (P < 0.05 vs. baseline), followed by a gradual decline over time. Both T2 and K values correlated well with Ki-67 indices (r = 0.765 and − 0.807, respectively; both P < 0.001), inflammation (r = 0.809 and − 0.724, respectively; both P < 0.001), steatosis grade (r = 0.814 and − 0.725, respectively; both P < 0.001), and HTS (r = 0.830 and − 0.615, respectively; both P < 0.001).

Conclusions

PH induced liver changes that can be observed on MRI. The MRI parameters correlate with the LR activity and allow monitoring of LR process.

Mouse Models of Liver Parenchyma Injuries and Regeneration

Mice have genetic and physiological similarities with humans and a well-characterized genetic background that is easy to manipulate. Murine models have become the most favored, robust mammalian systems for experimental analyses of biological processes and disease conditions due to their low cost, rapid reproduction, a wealth of mouse strains with defined genetic conditions (both native ones as well as ones established experimentally), and high reproducibility with respect to that which can be done in experimental studies. In this review, we focus on murine models for liver, an organ with renown regenerative capacity and the organ most central to systemic, complex metabolic and physiological functions for mammalian hosts. Establishment of murine models has been achieved for all aspects of studies of normal liver, liver diseases, liver injuries, and regenerative repair mechanisms. We summarize key information on current mouse systems that partially model facets of clinical scenarios, particularly those associated with drug-induced acute or chronic liver injuries, dietary related, non-alcoholic liver disease (NAFLD), hepatitis virus infectious chronic liver diseases, and autoimmune hepatitis (AIH). In addition, we also include mouse models that are suitable for studying liver cancers (e.g., hepatocellular carcinomas), the aging process (senescence, apoptosis), and various types of liver injuries and regenerative processes associated with them.

Aging reduces liver resiliency by dysregulating Hedgehog signaling

Older age is a major risk factor for damage to many tissues, including liver. Aging undermines resiliency and impairs liver regeneration. The mechanisms whereby aging reduces resiliency are poorly understood. Hedgehog is a signaling pathway with critical mitogenic and morphogenic functions during development. Recent studies indicate that Hedgehog regulates metabolic homeostasis in adult liver. The present study evaluates the hypothesis that Hedgehog signaling becomes dysregulated in hepatocytes during aging, resulting in decreased resiliency and therefore, impaired regeneration and enhanced vulnerability to damage. Partial hepatectomy (PH) was performed on young and old wild‐type mice and Smoothened (Smo)‐floxed mice treated with viral vectors to conditionally delete Smo and disrupt Hedgehog signaling specifically in hepatocytes. Changes in signaling were correlated with changes in regenerative responses and compared among groups. Old livers had fewer hepatocytes proliferating after PH. RNA sequencing identified Hedgehog as a top downregulated pathway in old hepatocytes before and after the regenerative challenge. Deleting Smo in young hepatocytes before PH prevented Hedgehog pathway activation after PH and inhibited regeneration. Gene Ontogeny analysis demonstrated that both old and Smo‐deleted young hepatocytes had activation of pathways involved in innate immune responses and suppression of several signaling pathways that control liver growth and metabolism. Hedgehog inhibition promoted telomere shortening and mitochondrial dysfunction in hepatocytes, consequences of aging that promote inflammation and impair tissue growth and metabolic homeostasis. Hedgehog signaling is dysregulated in old hepatocytes. This accelerates aging, resulting in decreased resiliency and therefore, impaired liver regeneration and enhanced vulnerability to damage.

Spatiotemporal imaging and analysis of mouse and human liver bud morphogenesis

BACKGROUND

The process of liver organogenesis has served as a paradigm for organ formation. However, there remains a lack of understanding regarding early mouse and human liver bud morphogenesis and early liver volumetric growth. Elucidating dynamic changes in liver volumes is critical for understanding organ development, implementing toxicological studies, and for modeling hPSC-derived liver organoid growth. New visualization, analysis, and experimental techniques are desperately needed.

RESULTS

Here, we combine observational data with digital resources, new 3D imaging approaches, retrospective analysis of liver volume data, mathematical modeling, and experiments with hPSC-derived liver organoids. Mouse and human liver organogenesis, characterized by exponential growth, demonstrate distinct spatial features and growth curves over time, which we mathematically modeled using Gompertz models. Visualization of liver-epithelial and septum transversum mesenchyme (STM) interactions suggests extended interactions, which together with new spatial features may be responsible for extensive exponential growth. These STM interactions are modeled with a novel in vitro human pluripotent stem cell (hPSC)-derived hepatic organoid system that exhibits cell migration.

CONCLUSIONS

Our methods enhance our understanding of liver organogenesis, with new 3D visualization, analysis, mathematical modeling, and in vitro models with hPSCs. Our approach highlights mouse and human differences and provides potential hypothesis for further investigation in vitro and in vivo.

MARCO+ Macrophage Dynamics in Regenerating Liver after 70% Liver Resection in Mice

BACKGROUND

Macrophages play a key role in liver regeneration. The fates of resident macrophages after 70% resection are poorly investigated. In this work, using the MARCO macrophage marker (abbreviated from macrophage receptor with collagenous structure), we studied the dynamics of mouse liver resident macrophages after 70% resection.

METHODS

In BALB/c male mice, a model of liver regeneration after 70% resection was reproduced. The dynamics of markers CD68, TIM4, and MARCO were studied immunohistochemically and by using a Western blot.

RESULTS

The number of MARCO- and CD68-positive macrophages in the regenerating liver increased 1 day and 3 days after resection, respectively. At the same time, the content of the MARCO protein increased in the sorted macrophages of the regenerating liver on the third day.

CONCLUSIONS

The data indicate that the number of MARCO-positive macrophages in the regenerating liver increases due to the activation of MARCO synthesis in the liver macrophages. The increased expression of MARCO by macrophages can be regarded as a sign of their activation. In the present study, stimulation with LPS led to an increase in the expression of the Marco gene in both Kupffer cells and macrophages of bone marrow origin.

Identifying the Key Genes in Mouse Liver Regeneration After Partial Hepatectomy by Bioinformatics Analysis and in vitro/vivo Experiments

Background

The liver is the only organ that can completely regenerate after various injuries or tissue loss. There are still a large number of gene functions in liver regeneration that have not been explored. This study aimed to identify key genes in the early stage of liver regeneration in mice after partial hepatectomy (PH).

Materials and Methods

We first analyzed the expression profiles of genes in mouse liver at 48 and 72 h after PH from Gene Expression Omnibus (GEO) database. Gene ontology (GO), and the Kyoto Encyclopedia of Genes and Genomes (KEGG), and protein-protein interaction (PPI) analysis were performed to identify key genes in liver regeneration. Finally, we validated key genes in vivo and in vitro.

Results

We identified 46 upregulated genes and 19 downregulated genes at 48 h after PH, and 223 upregulated genes and 40 downregulated genes at 72 h after PH, respectively. These genes were mainly involved in cell cycle, DNA replication, and p53 signaling pathway. Among of these genes, cycle-related genes (Ccna2, Cdkn1a, Chek1, and Mcm5) and Ube2c were highly expressed in the residual liver both at 48 and 72 h after PH. Furthermore, Ube2c knockdown not only caused abnormal expression of Ccna2, Cdkn1a, Chek1, and Mcm5, but also inhibited transition of hepatocytes from G1 to S phase of the cell cycle in vitro.

Conclusion

Mouse hepatocytes enter the proliferation phase at 48 h after PH. Ube2c may mediate cell proliferation by regulating or partially regulating Ccna2, Cdkn1a, Chek1, and Mcm5.

Macro- and microtranscriptomic evidence of the monocyte recruitment to regenerating liver after partial hepatectomy in mouse model

Macrophages are important regulators of liver repair. Participation of migratory monocytes/macrophages in regeneration of hepatic tissues after resection remains disputable. In mouse the resection promotes migration of Ly6C+CD11b+ monocytes/macrophages to the remnant liver accompanied by a reduction in its CD206 + macrophage content. Macrophage proliferation within the liver reaches maximum on day 3 after the surgery. Corresponding macro- and microtranscriptomic profiles of macrophages in regeneration liver cannot be unambiguously defined as pro- or anti-inflammatory. Their typical features include elevated expression of leukocyte chemoattractant factors, and many of the differentially expressed sequences are related to the control of cell growth and metabolic processes in the liver. These findings revealed essential roles of immigration of monocytes/macrophages and macrophages proliferation in maintenance of macrophage populations in the mouse liver during its recovery from a massive resection.

Caspase-3-related apoptosis prevents pathological regeneration in a living liver donor rat model

PURPOSE

The main goal of this study was to determine the relationship of cleaved-caspase-3 (C3)-related apoptosis and hepatic proliferation, during the liver repopulation in a living liver donor rat model.

MATERIAL/METHODS

Thirty-three animals were randomized into eleven groups and evaluated on postoperative from 3 ​h until 384 ​h after 30%-partial hepatectomy (30%-PHx). Liver sections (5 ​μm) were processed by hematoxylin-eosin, and immunostaining for C3, accompanied by hepatic function test. C3 content and the hepatic lobule enlargement were analyzed by optical density, followed by cell counting.

RESULTS

Transient variations of alanine transferase (ALT), aspartate aminotransferase (AST) and lactate dehydrogenase (LDH) were found. Significant increase in the C3 levels, and cell nuclei number, were detected at 12 ​h and 48 ​h after 30%-PHx, evidencing a correlation of p ​= ​-0.3679.

CONCLUSION

In the 30%-PHx rat model, C3-related apoptosis prevents proliferative pathological conditions during the hepatic lobule re-modeling.

The protein phosphatase PPM1A dephosphorylates and activates YAP to govern mammalian intestinal and liver regeneration

The Hippo-YAP pathway responds to diverse environmental cues to manage tissue homeostasis, organ regeneration, tumorigenesis, and immunity. However, how phosphatase(s) directly target Yes-associated protein (YAP) and determine its physiological activity are still inconclusive. Here, we utilized an unbiased phosphatome screening and identified protein phosphatase magnesium-dependent 1A (PPM1A/PP2Cα) as the bona fide and physiological YAP phosphatase. We found that PPM1A was associated with YAP/TAZ in both the cytoplasm and the nucleus to directly eliminate phospho-S127 on YAP, which conferring YAP the nuclear distribution and transcription potency. Accordingly, genetic ablation or depletion of PPM1A in cells, organoids, and mice elicited an enhanced YAP/TAZ cytoplasmic retention and resulted in the diminished cell proliferation, severe gut regeneration defects in colitis, and impeded liver regeneration upon injury. These regeneration defects in murine model were largely rescued via a genetic large tumor suppressor kinase 1 (LATS1) deficiency or the pharmacological inhibition of Hippo-YAP signaling. Therefore, we identify a physiological phosphatase of YAP/TAZ, describe its critical effects in YAP/TAZ cellular distribution, and demonstrate its physiological roles in mammalian organ regeneration.

Extended liver resection in mice: state of the art and pitfalls-a systematic review

Background

Rodent models of liver resection have been used to investigate and evaluate the liver’s complex physiology and pathology since 1931. First documented by Higgins and Anderson, such models were created to understand liver regeneration mechanisms to improve outcomes in patients undergoing extensive liver resection for liver cancer or other underlying liver diseases.

Methods

A systematic search was conducted using Pubmed, gathering publications up to January 2019, which engaged with the mouse model of extended liver resection as a method itself. The results of this search were filtered according to their language, novelty, and relevancy.

Results

The Boolean search found 3741 articles on Pubmed, with 3130 publications remaining when filtered by language and the presence of a full text. In total, 21 of these publications examined the key themes of the animal model described. The mortality varied from 0 to 50% depending on the surgeon's experience and the resection method. The liver resection was mainly performed with classic sutures (14 out of 21 publications) and isoflurane was used for anaesthesia (10 out of 21 publications) in combination with analgesics (buprenorphine or ketamine/xylazine). The most used mouse strain was C57BL/6 (7 of 21 publications) which was on average 11 weeks old with a weight of 23 g.

Conclusion

Through the overview, laid out in the selected publications, this paper reviews the shift of the extended liver resection model from rat to the mouse, describes the state of the art in the experimental setting, and discusses the possible limitations and pitfalls. Clearly, the extended liver resection in mice is a reproducible, practical and easy to learn method.

Functional compensation precedes recovery of tissue mass following acute liver injury

The liver plays a central role in metabolism, protein synthesis and detoxification. It possesses unique regenerative capacity upon injury. While many factors regulating cellular proliferation during liver repair have been identified, the mechanisms by which the injured liver maintains vital functions prior to tissue recovery are unknown. Here, we identify a new phase of functional compensation following acute liver injury that occurs prior to cellular proliferation. By coupling single-cell RNA-seq with in situ transcriptional analyses in two independent murine liver injury models, we discover adaptive reprogramming to ensure expression of both injury response and core liver function genes dependent on macrophage-derived WNT/β-catenin signaling. Interestingly, transcriptional compensation is most prominent in non-proliferating cells, clearly delineating two temporally distinct phases of liver recovery. Overall, our work describes a mechanism by which the liver maintains essential physiological functions prior to cellular reconstitution and characterizes macrophage-derived WNT signals required for this compensation.

The liver possesses the ability to regenerate following sudden injury. Here, the authors use single-cell RNA-sequencing and in situ transcriptional analyses to identify a new phase of liver regeneration in mice aimed at maintaining essential functions throughout the regenerative process.

Hemostasis and Liver Regeneration

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.

Periplaneta americana Extracts Accelerate Liver Regeneration via a Complex Network of Pathways

Successful recovery from hepatectomy is partially contingent upon the rate of residual liver regeneration. The traditional Chinese medicines known as Periplaneta americana extracts (PAEs) positively influence wound healing by promoting tissue repair. However, the effect of PAEs on liver regeneration is unknown. We used a mouse liver regeneration model after 70% partial hepatectomy (PH) and a hepatocyte culture to determine whether PAEs can promote liver regeneration as effectively as skin regeneration and establish their modes of action. L02 cells were divided into serum-starved control (NC) and three PAEs (serum starvation + 0.1 mg/ml, 0.5 mg/ml, or 1 mg/ml PAEs) groups. L02 cell proliferation was assessed at 24 h, 48 h, and 72 h by CCK-8 assay. Forty male C57 mice were randomly divided into control (NC), normal saline (NS), PAEs400 (400 mg/kg/d), and PAEs800 (800 mg/kg/d) groups (n = 10 per group). The NS and both PAEs groups were administered normal saline and PAEs, respectively, by gavage for 10 days. Two hours after the tenth gavage, the NS and both PAEs groups were subjected to 70% PH and the residual liver was harvested after 48 h. The hepatic regeneration rate was evaluated and hepatocyte proliferation was estimated by immunohistochemical (IHC) staining for Ki-67. Twelve DEG libraries (three samples per group) were prepared and sequencing was performed in an Illumina HiSeq 2000 (Mus_musculus) at the Beijing Genomics Institute. The genes expressed in the liver tissues and their expression profiles were analyzed by bioinformatics. KEGG was used to annotate, enrich, and analyze the pathways. PAEs promoted hepatocyte proliferation in vitro and in vivo and accelerated mouse liver regeneration after 70% PH. The screening criteria were fold change (FC) ≥ 2 and q-value < 0.001. We identified 1,092 known DEGs in PAEs400 and PAEs800. Of these, 153 were categorized in cellular processes. The KEGG analysis revealed that the aforementioned DEGs participated in several signaling pathways closely associated with cell proliferation including PI3K-Akt, MAPK, Apelin, Wnt, FoxO, mTOR, Ras, VEGF, ErbB, Hippo, and AMPK. It was concluded that PAEs can effectively improve liver regeneration via the synergistic activation of different signaling pathways.

Regulation of liver regeneration by prostaglandin E2 and thromboxane A2 following partial hepatectomy in rats

The implication of prostaglandin E₂ (PGE₂) and thromboxane A₂ (TXA₂) in the striking process of liver regeneration has been previously reported. However, their exact roles and downstream signals have not been utterly revealed. Therefore, the present study was conducted to explore whether inhibition of cyclooxygenase-2 (COX-2)-derived PGE₂ by celecoxib and blocking of TXA₂ action by seratrodast could alter the progression of liver regeneration after 70% partial hepatectomy (PHx) in rats. Celecoxib (20 mg/kg/day) and seratrodast (2 mg/kg/day) were given orally 1 h before PHx and then daily till the end of experiment (1, 3, or 7 days after the operation). Interestingly, celecoxib-treated rats showed a further increase in interleukin-6, p65 nuclear factor κB, and phosphorylated signal transducer and activator of transcription 3 as compared with PHx control rats. Furthermore, the liver contents of growth factors as well as β-catenin and cyclin D1protein expressions were also enhanced by celecoxib. Accordingly, celecoxib significantly improved hepatic proliferation as indicated by the increase in Ki67 expression and liver index. Contrariwise, seratrodast hindered the normal regeneration process and completely abolished the proliferative effect of celecoxib. In conclusion, TXA₂ has a major role in liver regeneration that could greatly mediate the triggering effect of celecoxib on hepatocytes proliferation following PHx.

Twenty-four hour ex-vivo normothermic machine perfusion in rat livers

Ex-vivo liver perfusion (EVLP) is an ideal platform to study liver disease, therapeutic interventions, and pharmacokinetic properties of drugs without any patient risk. Rat livers are an ideal model for EVLP due to less organ quality variability, ease of hepatectomy, well-defined molecular pathways, and relatively low costs compared to large animal or human perfusions. However, the major limitation with rat liver normothermic machine perfusion (NMP) is maintaining physiologic liver function on an ex-vivo machine perfusion system. To address this need, our research demonstrates 24-hour EVLP in rats under normothermic conditions. Early (6 hour) perfusate transaminase levels and oxygen consumption of the liver graft are shown to be good markers of perfusion success and correlate with viable 24-hour post-perfusion histology. Finally, we address overcoming challenges in long-term rat liver perfusions such as rising intrahepatic pressures and contamination, and offer future directions necessary to build upon our work.

Regional Differences following Partial Salivary Gland Resection

Regenerative medicine aims to repair, replace, or restore function to tissues damaged by aging, disease, or injury. Partial organ resection is not only a common clinical approach in cancer therapy but also an experimental injury model used to examine mechanisms of regeneration and repair in organs. We performed a partial resection, or partial sialoadenectomy, in the female murine submandibular salivary gland (SMG) to establish a model for investigation of repair mechanisms in salivary glands (SGs). After partial sialoadenectomy, we performed whole-gland measurements over a period of 56 d and found that the gland increased slightly in size. We used microarray analysis and immunohistochemistry (IHC) to examine messenger RNA and protein changes in glands over time. Microarray analysis identified dynamic changes in the transcriptome 3 d after injury that were largely resolved by day 14. At the 3-d time point, we detected gene signatures for cell cycle regulation, inflammatory/repair response, and extracellular matrix (ECM) remodeling in the partially resected glands. Using quantitative IHC, we identified a transient proliferative response throughout the gland. Both secretory epithelial and stromal cells expressed Ki67 that was detectable at day 3 and largely resolved by day 14. IHC also revealed that while most of the gland underwent a wound-healing response that resolved by day 14, a small region of the gland showed an aberrant sustained fibrotic response characterized by increased levels of ECM deposition, sustained Ki67 levels in stromal cells, and a persistent M2 macrophage response through day 56. The partial submandibular salivary gland resection model provides an opportunity to examine a normal healing response and an aberrant fibrotic response within the same gland to uncover mechanisms that prevent wound healing and regeneration in mammals. Understanding regional differences in the wound-healing responses may ultimately affect regenerative therapies for patients.

Mast Cells in Liver Fibrogenesis

Mast cells (MCs) are immune cells of the myeloid lineage that are present in the connective tissue throughout the body and in mucosa tissue. They originate from hematopoietic stem cells in the bone marrow and circulate as MC progenitors in the blood. After migration to various tissues, they differentiate into their mature form, which is characterized by a phenotype containing large granules enriched in a variety of bioactive compounds, including histamine and heparin. These cells can be activated in a receptor-dependent and -independent manner. Particularly, the activation of the high-affinity immunoglobulin E (IgE) receptor, also known as FcεRI, that is expressed on the surface of MCs provoke specific signaling cascades that leads to intracellular calcium influx, activation of different transcription factors, degranulation, and cytokine production. Therefore, MCs modulate many aspects in physiological and pathological conditions, including wound healing, defense against pathogens, immune tolerance, allergy, anaphylaxis, autoimmune defects, inflammation, and infectious and other disorders. In the liver, MCs are mainly associated with connective tissue located in the surrounding of the hepatic arteries, veins, and bile ducts. Recent work has demonstrated a significant increase in MC number during hepatic injury, suggesting an important role of these cells in liver disease and progression. In the present review, we summarize aspects of MC function and mediators in experimental liver injury, their interaction with other hepatic cell types, and their contribution to the pathogenesis of fibrosis.

GSK923295 as a potential antihepatocellular carcinoma agent causing delay on liver regeneration after partial hepatectomy

Background:

The clinical trials emerged centromere protein E inhibitor GSK923295 as a promising anticancer drug, but its function in hepatocellular carcinoma (HCC) remain needs to be fully elucidated, especially as chemotherapy after hepatectomy for liver tumors. We aimed to describe anti-HCC activities of GSK923295 and compare its antiproliferative effects on liver regeneration after partial hepatectomy (PH).

Methods:

All subjects were randomized to treatment with either vehicle or GSK923295. Antitumor activity of GSK923295 was assessed by xenograft growth assays. The C57BL/6 mice were subjected to 70% PH and the proliferation was calculated by liver coefficient, further confirmed by immunohistochemistry. The proliferation and cell cycle analysis of liver cell AML12 and HCC cells LM3, HUH7, and HepG2 were investigated using the cell counting kit-8 assay and Flow Cytometry. The chromosome misalignment and segregation in AML12 cells were visualized by immunofluorescence.

Results:

Treatment with GSK923295 induced antiproliferation in HCC cell lines. It also caused delay on HCC tumor growth instead of regression both in a HCC cell line xenograft model and patient-derived tumor xenograft model. With microarray analysis, CENtromere Protein E was gradually increased in mouse liver after PH. Exposure of liver cells to GSK923295 resulted in delay on a cell cycle in mitosis with a phenotype of misaligned chromosomes and chromosomes clustered. In 70% PH mouse model, GSK923295 treatment also remarkably reduced liver regeneration in later stage, in parallel with the mitotic marker phospho-histone H3 elevation.

Conclusion:

The anticancer drug GSK923295 causes a significant delay on HCC tumor growth and liver regeneration after PH in later stage.

Omega-3 fatty acid supplementation does not influence liver regeneration in rats after partial hepatectomy

Aim of the study

In the initiation of liver regeneration, multiple stimulatory and inhibitory factors participate. In this study, we aimed to evaluate the effects of omega-3 fatty acids on liver regeneration after 30% partial hepatectomy in rats.

Material and methods

A total of 14 male Wistar Albino rats were included in this study. The animals were randomly allocated to two groups: the control group (n = 7) and the omega-3 group (n = 7). Rats in the control group were fed a standard rat chow and rats in the omega-3 group received 10 mg/kg/day omega-3 supplementation in addition to normal rat chow in the perioperative period. Rats were investigated seven days after 1/3 partial hepatectomy by liver weight change and hepatocyte proliferation.

Results

The mean liver regeneration rate was found to be slightly higher (p = 0.061) in the omega-3 group compared the control group. In addition, no significant difference was observed regarding binuclear hepatocyte ratio in pericentral and periportal areas between the two groups. However, livers from rats given omega-3 supplementation have less inflammatory cellular infiltrate in the portal space than livers from the control group.

Conclusions

Supplementation with omega-3 fatty acids showed no influence on the liver regeneration in rats undergoing 1/3 partial hepatectomy.

Gankyrin Promotes Tumor-Suppressor Protein Degradation to Drive Hepatocyte Proliferation

Background & Aims

Uncontrolled liver proliferation is a key characteristic of liver cancer; however, the mechanisms by which this occurs are not well understood. Elucidation of these mechanisms is necessary for the development of better therapy. The oncogene Gankyrin (Gank) is overexpressed in both hepatocellular carcinoma and hepatoblastoma. The aim of this work was to determine the role of Gank in liver proliferation and elucidate the mechanism by which Gank promotes liver proliferation.

Methods

We generated Gank liver-specific knock-out (GLKO) mice and examined liver biology and proliferation after surgical resection and liver injury.

Results

Global profiling of gene expression in GLKO mice showed significant changes in pathways involved in liver cancer and proliferation. Investigations of liver proliferation after partial hepatectomy and CCl4 treatment showed that GLKO mice have dramatically inhibited proliferation of hepatocytes at early stages after surgery and injury. In control LoxP mice, liver proliferation was characterized by Gank-mediated reduction of tumor-suppressor proteins (TSPs). The failure of GLKO hepatocytes to proliferate is associated with a lack of down-regulation of these proteins. Surprisingly, we found that hepatic progenitor cells of GLKO mice start proliferation at later stages and restore the original size of the liver at 14 days after partial hepatectomy. To examine the proliferative activities of Gank in cancer cells, we used a small molecule, cjoc42, to inhibit interactions of Gank with the 26S proteasome. These studies showed that Gank triggers degradation of TSPs and that cjoc42-mediated inhibition of Gank increases levels of TSPs and inhibits proliferation of cancer cells.

Conclusions

These studies show that Gank promotes hepatocyte proliferation by elimination of TSPs. This work provides background for the development of Gank-mediated therapy for the treatment of liver cancer. RNA sequencing data can be accessed in the NCBI Gene Expression Omnibus: GSE104395.

Longitudinal micro-computed tomography monitoring of progressive liver regeneration in a mouse model of partial hepatectomy

The partial hepatectomy (PH) model is widely used to study liver regeneration. Currently, the extent of regeneration is analyzed by measuring the weight of the liver post-mortem or by magnetic resonance imaging. In this study we aimed to determine whether liver volume gain can be accurately measured using micro-computed tomography (microCT). Approximately 42% of the liver was removed by ligation in C57BL/6 N mice. Mice were divided into two study groups. In group 1 conventional characterization of liver hyperplasia was performed by weighing the liver post-mortem. In group 2, liver volume gain was determined by microCT volume estimation. MicroCT results showed equivalent regeneration rates compared with the conventional method without the need to mathematically determine initial liver weights before PH. This parameter is strongly influenced by the age, strain and sex of the mice. In addition non-invasive microCT determination of volume gain over multiple time-points using the same animal reduces the number of animals needing to be used (in line with the 3R principle of replacement, reduction and refinement).

MicroRNA-21 Contributes to Liver Regeneration by Targeting PTEN

Background

Multiple microRNAs (miRNAs, miRs), including miR-21, have been documented to be critical regulators of liver regeneration, but the mechanism underlying their roles in hepatocyte proliferation and cell cycle progression is still far from understood.

Material/Methods

miR-21 levels were determined using qRT-PCRs in mouse livers at 48 h after 70% partial hepatectomy (PH-48 h). Cell proliferation was determined by use of a cell-counting kit-8 (CCK-8), EdU incorporation staining, and flow cytometry. Phosphatase and tensin homolog (PTEN) expressions were determined using qRT-PCR and Western blot analysis. PTEN siRNA was used to perform the rescue experiment.

Results

A marked upregulation of miR-21 was observed in mouse livers at 48 h after 70% partial hepatectomy (PH-48 h) compared to 0 h after PH (PH-0 h). Overexpression of miR-21 was associated with increased proliferation and a rapid G1-to-S phase transition of the cell cycle in BNL CL.2 normal liver cells in vitro. In addition, we showed that PTEN expression was inversely correlated with miR-21 in BNL CL.2 cells and demonstrated that PTEN expression is lower in mouse livers at PH-48 h. Moreover, the presence of PTEN siRNA significantly abolished the suppressive effect of miR-21 inhibitor on hepatocyte proliferation.

Conclusions

miR-21 overexpression contributes to liver regeneration and hepatocyte proliferation by targeting PTEN. Upregulation of miR-21 might be a useful therapeutic strategy to promote liver regeneration.