Early Stages Of Liver Regeneration Research Articles

CBX7 silencing promoted liver regeneration by interacting with BMI1 and activating the Nrf2/ARE signaling pathway

Multiple studies have shown knockdown of chromobox 7 (CBX7) promotes the regenerative capacity of various cells or tissues. We examined the effect of CBX7 on hepatocyte proliferation and liver regeneration after 2/3 hepatectomy in a mouse model. For in vitro experiments, NCTC 1469 and BNL CL.2 hepatocytes were co-transfected with siRNA-CBX7-1 (si-CBX7-1), siRNA-CBX7-2 (si-CBX7-2), pcDNA-CBX7, si-BMI1-1, si-BMI1-2, pcDNA-BMI1, or their negative control. For in vivo experiments, mice were injected intraperitoneally with lentivirus-packaged shRNA and shRNA CBX7 before hepatectomy. Our results showed that CBX7 was rapidly induced in the early stage of liver regeneration. CBX7 regulated hepatocyte proliferation, cell cycle, and apoptosis of NCTC 1469 and BNL CL.2 hepatocytes. CBX7 interacted with BMI1 and inhibited BMI1 expression in hepatocytes. Silencing BMI1 aggregated the inhibitory effect of CBX7 overexpression on hepatocyte viability and the promotion of apoptosis. Furthermore, silencing BMI1 enhanced the regulatory effect of CBX7 on Nrf2/ARE signaling in HGF-induced hepatocytes. In vivo, CBX7 silencing enhanced liver/body weight ratio in PH mice. CBX7 silencing promoted the Ki67-positive cell count and decreased the Tunel-positive cell count after hepatectomy, and also increased the expression of nuclear Nrf2, HO-1, and NQO-1. Our results suggest that CBX7 silencing may increase survival following hepatectomy by promoting liver regeneration.

New insights into the regulation of bile acids synthesis during the early stages of liver regeneration: A human and experimental study

Background and aims: Liver regeneration is essential for the preservation of homeostasis and survival. Bile acids (BAs)-mediated signaling is necessary for liver regeneration, but BAs levels need to be carefully controlled to avoid hepatotoxicity. We studied the early response of the BAs-fibroblast growth factor 19 (FGF19) axis in healthy individuals undergoing hepatectomy for living donor liver transplant. We also evaluated BAs synthesis in mice upon partial hepatectomy (PH) and acute inflammation, focusing on the regulation of cytochrome-7A1 (CYP7A1), a key enzyme in BAs synthesis from cholesterol.Methods: Serum was obtained from twelve human liver donors. Mice underwent 2/3-PH or sham-operation. Acute inflammation was induced with bacterial lipopolysaccharide (LPS) in mice fed control or antoxidant-supplemented diets. BAs and 7α-hydroxy-4-cholesten-3-one (C4) levels were measured by HPLC-MS/MS; serum FGF19 by ELISA. Gene expression and protein levels were analyzed by RT-qPCR and western-blot.Results: Serum BAs levels increased after PH. In patients with more pronounced hypercholanemia, FGF19 concentrations transiently rose, while C4 levels (a readout of CYP7A1 activity) dropped 2 h post-resection in all cases. Serum BAs and C4 followed the same pattern in mice 1 h after PH, but C4 levels also dropped in sham-operated and LPS-treated animals, without marked changes in CYP7A1 protein levels. LPS-induced serum C4 decline was attenuated in mice fed an antioxidant-supplemented diet.Conclusions: In human liver regeneration FGF19 upregulation may constitute a protective response from BAs excess during liver regeneration. Our findings suggest the existence of post-translational mechanisms regulating CYP7A1 activity, and therefore BAs synthesis, independent from CYP7A1/Cyp7a1 gene transcription.

Apolipoprotein A-1 Accelerated Liver Regeneration Through Regulating Autophagy Via AMPK-ULK1 Pathway

Apolipoprotein A-1 (ApoA-1), the main apolipoprotein of high-density lipoprotein, has been well studied in the area of lipid metabolism and cardiovascular diseases. In this project, we clarify the function and mechanism of ApoA-1 in liver regeneration. Seventy percent of partial hepatectomy was applied in male ApoA-1 knockout mice and wild-type mice to investigate the effects of ApoA-1 on liver regeneration. D-4F (ApoA-1 mimetic peptide), autophagy activator, and AMPK activator were used to explore the mechanism of ApoA-1 on liver regeneration. We demonstrated that ApoA-1 levels were highly expressed during the early stage of liver regeneration. ApoA-1 deficiency greatly impaired liver regeneration after hepatectomy. Meanwhile, we found that ApoA-1 deficiency inhibited autophagy during liver regeneration. The activation of autophagy protected against ApoA-1 deficiency in inhibiting liver regeneration. Furthermore, ApoA-1 deficiency impaired autophagy through AMPK-ULK1 pathway, and AMPK activation significantly improved liver regeneration. The administration of D-4F could accelerated liver regeneration after hepatectomy. These findings suggested that ApoA-1 played an essential role in liver regeneration through promoting autophagy in hepatocytes via AMPK-ULK1 pathway. Our findings enrich the understanding of the underlying mechanism of liver regeneration and provide a potential therapeutic strategy for liver injury.

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

BackgroundThe 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 MethodsWe 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.ResultsWe 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.ConclusionMouse 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.

A comprehensive investigation on liver regeneration: a meta-analysis and systems biology approach.

Aim of the studyLiver regeneration is one of the essential fields of regenerative medicine as a branch of tissue engineering and molecular biology that draws global researchers’ attention. This study aims to conduct a systematic review and meta-analysis on the high-throughput gene expression microarray dataset of liver regeneration on the NCBI-GEO database to identify the significant genes and signaling pathways and confirm the genes from literature studies on associated diseases.Material and methodsWe thoroughly searched the NCBI-GEO database to retrieve and screen the GEO microarray datasets’ contents. Due to the inclusion of different species in eligible GEO datasets in the meta-analysis, the list of significant genes for the random-effects model were identified. Moreover, we carried out detailed gene analyses for three main gene ontology components and the KEGG signaling pathway. Furthermore, we investigated the possibility of genes’ association with liver cancer through the Kaplan-Meier plot.ResultsThe random-effects model from six eligible GEO datasets identified 71 genes with eight down-regulated and 63 up-regulated genes. The target genes are involved in various cellular functions such as cell proliferation, cell death, and cell cycle control. Finally, we noted that 58 out of 71 genes are associated with different types of diseases related explicitly to other liver and inflammation diseases.ConclusionsThe current study assessed various GEO datasets at the early stages of liver regeneration with promising results. The present systematic review and meta-analysis results are beneficial for future novel drug design and discovery specifically for patients in the liver transplantation process.

Deletion of Golgi protein 73 delayed hepatocyte proliferation of mouse in the early stages of liver regeneration.

Golgi protein 73 (GP73) is a transmembrane protein that can promote the proliferation of cancer cells. However, the roles of GP73 in the proliferation of non-malignant hepatocytes have rarely been investigated. The wild-type (GP73+/+ ) and GP73 gene knockout mice (GP73-/- ) were subject to 70% partial hepatectomy (PHx) to explore the involvement of GP73 in liver regeneration. After PHx, a significant increase of GP73 expression was observed in GP73+/+ mouse liver. Noticeably, promoted recovery of liver mass was observed in GP73-/- mouse at Day 1 after PHx, as showed by the liver/body weight ratio. RNA sequencing revealed that genes relevant to cell cycle and inflammation response in the residual liver tissues were severely suppressed with the deletion of GP73, particularly the inactivation of NF-κB signal pathway in early phase of liver regeneration. In line with this, we do see the downregulation of cell cycle-related protein including cyclin D1, p-cyclin D1, β-catenin, as well as interleukin 6, tumor necrosis factor-α, CCl2, and CXCl10. In contrast, activation of mTOR signaling pathway was documented, accompanied with the histological hypertrophy of hepatocytes in GP73-/- mouse. Golgi protein 73 deletion leads to delayed response of liver regeneration and inflammation in the early stages of liver regeneration after PHx.

Liver Macrophages Stimulate the Expression of Hepatocyte Nuclear Factor-6 and Promote Hepatocyte Proliferation at the Early Stage of Liver Regeneration.

Hepatocyte nuclear factor (HNF-6) is a liver-specific protein and a key component in the differentiation process during the development of mature liver. The immunohistochemical staining and RT-PCR techniques were employed to examine the expression of HNF-6 and proliferation of Ki-67+ cells during the early regeneration of the liver on postsurgery in 3, 6, 12, and 24 h in original model of partial hepatectomy in rats. The earliest proliferating (Ki-67+) cells were observed in 3 h after surgery in liver sinusoids (liver macrophages) and then in liver parenchyma. Expression of HNF-6 in hepatocytes and epithelial cells of the bile ducts attained maximum in 6 h after surgery. At later terms, this parameter somewhat decreased, but still surpassed the control level.

Islet-cell autoantigen 69 accelerates liver regeneration by downregulating Tgfbr1 and attenuating Tgfβ signaling in mice.

Regeneration is a unique defense mechanism of liver tissue in response to functional cell loss induced by toxic chemicals or surgical resection. In this study, we found that Islet-cell autoantigen 69 (Ica69) accelerates liver regeneration in mice. Following 70% partial hepatectomy, both Ica69 mRNA and protein are significantly upregulated in mouse hepatocytes at the early stage of liver regeneration. Compared with the wild-type mice, Ica69-deficient mice have more severe liver injury, delayed liver regeneration, and high surgical accidental mortality following hepatectomy. Mechanistically, Ica69 interacts with Pick1 protein to regulate Tgfbr1 protein expression and Tgfβ-induced Smad2 phosphorylation. Our findings suggest that Ica69 in liver tissue is a new potential target for promoting liver regeneration.

Hepatocyte nuclear factor 4α negatively regulates connective tissue growth factor during liver regeneration.

Liver regeneration after injury requires fine‐tune regulation of connective tissue growth factor (Ctgf). It also involves dynamic expression of hepatocyte nuclear factor (Hnf)4α, Yes‐associated protein (Yap), and transforming growth factor (Tgf)‐β. The upstream inducers of Ctgf, such as Yap, etc, are well‐known. However, the negative regulator of Ctgf remains unclear. Here, we investigated the Hnf4α regulation of Ctgf post‐various types of liver injury. Both wild‐type animals and animals contained siRNA‐mediated Hnf4α knockdown and Cre‐mediated Ctgf conditional deletion were used. We observed that Ctgf induction was associated with Hnf4α decline, nuclear Yap accumulation, and Tgf‐β upregulation during early stage of liver regeneration. The Ctgf promoter contained an Hnf4α binding sequence that overlapped with the cis‐regulatory element for Yap and Tgf‐β. Ctgf loss attenuated inflammation, hepatocyte proliferation, and collagen synthesis, whereas Hnf4α knockdown enhanced Ctgf induction and liver fibrogenesis. These findings provided a new mechanism about fine‐tuned regulation of Ctgf through Hnf4α antagonism of Yap and Tgf‐β activities to balance regenerative and fibrotic signals.

CD11B+ Ly6G+ myeloid derived suppressor cells promote liver regeneration in a murine model of major hepatectomy

Background: Liver regeneration depends on sequential activation of multiple pathways and cell types involving the remaining organ in recovery of mass. Proliferation of parenchyma is dependent on angiogenesis. Understanding liver regeneration associated neovascularization may be useful for future development of clinical interventions. Myeloid Derived Suppressor Cells (MDSCs) promote immune suppression and tumor angiogenesis, and play a role in normal developmental processes that necessitate rapid vascularization. The role of MDSCs in liver regeneration has not been studied. Materials & Methods: The proportion of MDSC populations was assessed within remnant livers following major hepatectomy (Hx). The effect of CD11b+Ly6G+ MDSCs (G-MDSCs) depletion on post-operative mortality, liver injury, regeneration, and angiogenesis was evaluated. Transcriptional and functional characterization of regenerating liver-derived G-MDSCs was performed. All animal studies were conducted according to protocols approved by the institutional animal care and use committee of Tel-Aviv Sourasky Medical Center, strictly observing national, local, and institutional guidelines. Approval no. 13-4-16 Results: G-MDSCs were enriched within regenerating livers, and their depletion led to increased post-operative mortality, reduced liver weights, increased liver injury, decreased hepatic vascularization and hepatocyte proliferation, and to aberrant liver function indices in peripheral blood. Global gene expression profiling of regenerating liver-derived G-MDSCs demonstrated a large-scale transcriptional response, involving key pathways related to angiogenesis. Functionally, enhanced reactive oxygen species production and angiogenic capacities of regenerating liver-derived G-MDSCs were confirmed. A comparative analysis revealed that the transcriptional response of G-MDSCs during liver regeneration highly resembled that of peripheral blood G-MDSCs during progression of abdominal tumors, suggesting a common G-MDSC gene expression profile promoting angiogenesis. Conclusions: This study provides the first evidence that MDSCs contribute to early stages of liver regeneration by exerting pro-angiogenic functions using a unique transcriptional program.

CD11b + Ly6G + myeloid‐derived suppressor cells promote liver regeneration in a murine model of major hepatectomy

Liver regeneration depends on sequential activation of pathways and cells involving the remaining organ in recovery of mass. Proliferation of parenchyma is dependent on angiogenesis. Understanding liver regeneration-associated neovascularization may be useful for development of clinical interventions. Myeloid-derived suppressor cells (MDSCs) promote tumor angiogenesis and play a role in developmental processes that necessitate rapid vascularization. We therefore hypothesized that the MDSCs could play a role in liver regeneration. Following partial hepatectomy, MDSCs were enriched within regenerating livers, and their depletion led to increased liver injury and postoperative mortality, reduced liver weights, decreased hepatic vascularization, reduced hepatocyte hypertrophy and proliferation, and aberrant liver function. Gene expression profiling of regenerating liver-derived MDSCs demonstrated a large-scale transcriptional response involving key pathways related to angiogenesis. Functionally, enhanced reactive oxygen species production and angiogenic capacities of regenerating liver-derived MDSCs were confirmed. A comparative analysis revealed that the transcriptional response of MDSCs during liver regeneration resembled that of peripheral blood MDSCs during progression of abdominal tumors, suggesting a common MDSC gene expression profile promoting angiogenesis. In summary, our study shows that MDSCs contribute to early stages of liver regeneration possibly by exerting proangiogenic functions using a unique transcriptional program.-Nachmany, I., Bogoch, Y., Sivan, A., Amar, O., Bondar, E., Zohar, N., Yakubovsky, O., Fainaru, O., Klausner, J. M., Pencovich, N. CD11b+Ly6G+ myeloid-derived suppressor cells promote liver regeneration in a murine model of major hepatectomy.

Hepatic angiocrine HGF signaling plays a vital role in the early stage of liver regeneration after PHx in mice

Hepatic angiocrine HGF signaling plays a vital role in the early stage of liver regeneration after PHx in mice

MicroRNA-34a regulates liver regeneration and the development of liver cancer in rats by targeting Notch signaling pathway.

ObjectiveThis study aimed to investigate the role of microRNA-34a (miR-34a) in regulating liver regeneration (LR) and the development of liver cancer in rats by targeting Notch signaling pathway.MethodsThirty male Sprague-Dawley (SD) rats were randomly assigned into partial hepatectomy (PH) group and sham hepatectomy (SH) group. Hematoxylin and eosin (HE) staining was used to observe the histological change in liver tissues. Enzyme-linked immunosorbent assay (ELISA) was used to measure the serum tumor necrosis factor α (TNF-α) and interleukin-6 (IL-6) levels. Dual-luciferase reporter gene assay was performed to examine whether miR-34a targeted Notch1 gene. Human liver cancer Huh7 cells were transfected and divided into blank, negative control (NC), miR-34a mimics and miR-34a inhibitors groups. MTT and flow cytometry were used to detect cell growth, and cell cycle and apoptosis, respectively. Quantitative real-time polymerase chain reaction (qRT-PCR) was applied detect to the expressions of miR-34a and Notch receptor mRNA. Western blotting was performed to detect the protein expressions of Notch receptors, P21, Bax, Bcl-2 and Bcl-xL. Tumor xenograft in nude mice was done to observe tumor formation in different groups.ResultsCompared to the SH group, miR-34a expression in liver tissues in the PH group decreased first and then increased to the normal level during LR. In early stage of LR, the expressions of Notch receptors and miR-34a were negatively correlated. Compared to the blank and NC groups, the cell growth was inhibited, cell cycle was mainly arrested in the G2/M phase and cell apoptosis rate increased in the miR-34a mimics group. Moreover, the expressions of miR-34a, P21 and Bax were up-regulated, while the expressions of Notch receptors, and Bcl-2 and Bcl-xL were down-regulated in this group. Additionally, the tumor growth in the miR-34a mimics group was reduced. The miR-34a inhibitors group showed contrary tendencies.ConclusionOur study demonstrates that miR-34a regulated LR and the development of liver cancer by inhibiting Notch signaling pathway.

Apoptosis induced by boric anhydrite (B2O3) after partial hepatectomy in rat liver.

Boron is one of the important elements that have a cell-growth suppressing effect. The apoptotic effects of B(2)O(3) that were investigated in rats on liver regeneration following 70 % partial hepatectomy (PH). Wistar albino male rats were used and divided into 4 groups (n = 7). The Saline control groups were given only a single dose of saline; the B(2)O(3)-treated groups that were only given a single dose of 1800 mg.kg(-1) B(2)O(3) by means of intraperitoneal injections following hepatectomy. Three and 6 hours after surgical procedures, all the groups were dissected and liver tissue samples were taken from the groups for NF-κB for caspase-3 gene and protein levels investigation by RT-PCR and TaqMan Protein Assay and histological analyses by TUNEL assay. B(2)O(3)-treated animals were examined and it was observed that NF-κB levels were decreased; however, caspase-3 gene expression and protein levels were increased significantly. This study demonstrated that B(2)O(3) induces caspase-3 and inhibits NF-κB at the early stage of liver regeneration (Fig. 4, Ref. 26).

Amiodarone as an autophagy promoter reduces liver injury and enhances liver regeneration and survival in mice after partial hepatectomy.

The deregulation of autophagy is involved in liver regeneration. Here, we investigated the role of autophagy in the regulation of liver regeneration after partial hepatectomy (PHx) and the development of pharmacological interventions for improved liver regeneration after PHx. We show that autophagy was activated in the early stages of liver regeneration following 70% PHx in vivo. Moreover, amiodarone was associated with a significant enhancement of autophagy, liver growth, and hepatocyte proliferation, along with reduced liver injury and the termination of liver regeneration due to decreased transforming growth factor-β1 expression after 70% PHx. The promotion of autophagy appeared to selectively increase the removal of damaged mitochondria. We also found that Atg7 knockdown or pretreatment with chloroquine aggravated the liver injury associated with 70% PHx and reduced liver growth and hepatocyte proliferation. Finally, amiodarone improved liver regeneration, survival, and liver injury after 90% PHx. In conclusion, our results indicate that autophagy plays an important role in mouse liver regeneration and that modulating autophagy with amiodarone may be an effective method of improving liver regeneration, increasing survival, and ameliorating liver injury following PHx.

Dissecting the role of epidermal growth factor receptor catalytic activity during liver regeneration and hepatocarcinogenesis.

Different data support a role for the epidermal growth factor receptor (EGFR) pathway during liver regeneration and hepatocarcinogenesis. However, important issues, such as the precise mechanisms mediating its actions and the unique versus redundant functions, have not been fully defined. Here, we present a novel transgenic mouse model expressing a hepatocyte-specific truncated form of human EGFR, which acts as negative dominant mutant (ΔEGFR) and allows definition of its tyrosine kinase-dependent functions. Results indicate a critical role for EGFR catalytic activity during the early stages of liver regeneration. Thus, after two-thirds partial hepatectomy, ΔEGFR livers displayed lower and delayed proliferation and lower activation of proliferative signals, which correlated with overactivation of the transforming growth factor-β pathway. Altered regenerative response was associated with amplification of cytostatic effects of transforming growth factor-β through induction of cell cycle negative regulators. Interestingly, lipid synthesis was severely inhibited in ΔEGFR livers after partial hepatectomy, revealing a new function for EGFR kinase activity as a lipid metabolism regulator in regenerating hepatocytes. In spite of these profound alterations, ΔEGFR livers were able to recover liver mass by overactivating compensatory signals, such as c-Met. Our results also indicate that EGFR catalytic activity is critical in the early preneoplastic stages of the liver because ΔEGFR mice showed a delay in the appearance of diethyl-nitrosamine-induced tumors, which correlated with decreased proliferation and delay in the diethyl-nitrosamine-induced inflammatory process. These studies demonstrate that EGFR catalytic activity is critical during the initial phases of both liver regeneration and carcinogenesis and provide key mechanistic insights into how this kinase acts to regulate liver pathophysiology. (Hepatology 2016;63:604-619).

GPC3‐CD81 axis in the HCV mediated liver carcinogenesis

Glypican‐3 (GPC3) is highly over‐expressed in human hepatocellular carcinomas (HCC). GPC3 decreases liver regeneration by interacting with CD81. Other groups have shown that activation of CD81 increases phosphorylation of Ezrin (p‐Ezrin), which inhibits Hippo pathway. Hepatitis C virus (HCV) interacts with human CD81 by E2 protein to enter into hepatocytes. We investigated the mechanism of HCV and GPC3‐CD81 axis in liver carcinogenesis. HepaRG human hepatoma cell line was treated with E2 protein to evaluate the Hippo activity. Rat hepatocytes were treated with CD81 agonist antibody to determine if CD81 related Hippo activity depends on p‐Ezrin. Partial hepatectomy (PHx) was used to evaluate the dynamic changes of GPC3‐CD81 axis with Hippo activity. Human and rat HCC cell lines were used to define GPC3‐CD81 interactions. HCC tissue array was used to assess the expression characteristic of CD81‐GPC3. After E2 treatment, Hepa RG cells had higher activity of Hippo. Treatment of rat hepatocytes with CD81 agonist antibody led to lower Hippo activity and higher p‐Ezrin. PHx shows that GPC3 increases at the early stage of liver regeneration while CD81 decreases, while Yap activity increases. Both human and rat HCC cell lines have dramatically decreased CD81 expression levels. HCC tissue array also shows absence of CD81 in most HCC.ConclusionsDependent on CD81, GPC3 may function as tumor‐suppressor gene by modulating YAP expression. Persistent E2 HCV protein interacts with CD81 to decrease Yap via Hippo. Hepatocytes with no expression of CD81 would have a growth advantage to undergo clonal expansion, facilitating formation of HCC. After absence of CD81, GPC3 may be unable to control the Hippo, and this maybe the reason for its high expression in HCC.

An Integrated Approach for the Identification of HNF4α-Centered Transcriptional Regulatory Networks During Early Liver Regeneration

Background/Aims: Hepatocyte nuclear factor-4α (HNF4α), the liver enriched transcription factor (TF), is one of the major regulators of hepatocyte differentiation and proliferation. However, how HNF4α participate in liver regeneration after partial hepatectomy (PH) remains largely unknown. In order to identify the HNF4α-centered regulatory network, we applied an integrated analytic strategy, in which, TF array, mRNA microarray, bioinformatic analysis and ChIP-on-chip assays were integrated. Methods/Results: The TF signatures from MOUSE OATFA (TF-array) platform revealed that the activity of HNF4α was significantly reduced and 17 other TFs showed increased activity at 4 h post PH. Then the ChIP-on-chip analysis on HNF4α were combined with mRNA expression profiling to select the possible HNF4α target genes during early liver regeneration, which were then sub-grouped according to their signaling pathways. More specifically, the HNF4α target genes with the gene ontology (GO) terms of cytokine-cytokine receptor, Jak-STAT, MAPK, toll-like receptor and insulin signaling pathways were further analyzed with an advanced bioinformatics tool named oPOSSUM to identify TF binding sites occupancy and predict the co-regulatory relationship between TFs and targets. Furthermore, we identified that repressed HNF4α during the early phase of liver regeneration may contribute cooperatively to the induction of immediate early genes, such as, c-fos, c-jun and stat3. Conclusion: our data indicate that HNF4α may play an inhibitory role on the induction of specific promitogenic genes and liver regeneration initiation. The integrated approach of mRNA/OATFA/ChIP-DSL/oPOSSUM analysis may help us better characterize the target genes and co-regulatory network of HNF4α during the early stage of liver regeneration.

Impaired liver regeneration in Ldlr−/− mice is associated with an altered hepatic profile of cytokines, growth factors, and lipids

It is widely recognized that in the early stages of liver regeneration after partial hepatectomy, the hepatocytes accumulate a significant amount of lipids. The functional meaning of this transient steatosis and its effect on hepatocellular proliferation are not well defined. In addition, the basic mechanisms of this lipid accumulation are not well understood although some studies suggest the participation of the Low Density Lipoprotein Receptor (Ldlr). To address these questions, we studied the process of liver regeneration in Ldlr null mice and wild type mice following partial hepatectomy. Ldlr deficiency was associated with a significant decrease in serum albumin concentration, during early stages of liver regeneration, and a delayed hepatic regeneration. Remnant livers of Ldlr(-)(/)(-) showed a time-shifted expression of interleukin-6 (IL6) and a defective activation of tumor necrosis factor-α (TNFα) and hepatocyte growth factor (HGF) expression in early phases of liver regeneration. Unexpectedly, Ldlr(-)(/)(-) showed no significant differences in the content of lipid droplets after partial hepatectomy compared to wild type mice. However, lipidomic analysis of the regenerating liver from Ldlr(-)(/)(-) revealed a lipid profile compatible with liver quiescence: high content of cholesterol esters and ceramide, and low levels of phosphatidylcholine. Ldlr deficiency is associated with significant changes in the hepatic lipidome that affect cytokine-growth factor signaling and impair liver regeneration. These results suggest that the analysis of the hepatic lipidome may help predict the success of liver regeneration in the clinical environment, specifically in the context of pre-existing liver steatosis.

Blockade of the renin–angiotensin system improves the early stages of liver regeneration and liver function

BackgroundPartial hepatectomy is the preferred option for selected patients with colorectal cancer liver metastases (CRCLM). Sufficient liver regeneration (LR) is essential for a successful outcome in these patients. The blockade of the renin–angiotensin system (RAS) reduces the growth of several tumor types. The RAS also acts as a regulator of liver fibrosis and potentially LR. The angiotensin-converting enzyme (ACE) inhibitor, captopril, significantly inhibits the growth of CRCLM, but its effect on LR remains undefined. MethodsAfter 70% of partial hepatectomy, mice were randomly assigned to control or captopril-treated groups. LR was measured by liver-to-body weight ratio on days 1, 2, 4, 6, and 8. Hepatocyte proliferation, apoptosis and cell size, hepatic stellate cell (HSC) count, and sinusoidal endothelial cell density were quantified. Matrix metalloproteinase 9 (MMP-9) protein levels, liver injury markers, and RAS messenger RNA levels were also determined. ResultsAt day 2, captopril increased liver-to-body weight ratio (56.5 ± 1.7 captopril versus 49.3 ± 2.4 control, P = 0.027). This was associated with increased HSC count (65.4 ± 4.8 cells per 100,000 μm2, 48.7 ± 2.3, P = 0.007) and MMP-9 levels (0.68 ± 0.12 AU, 0.12 ± 0.04, P = 0.014). The messenger RNA levels of angiotensin-converting enzyme (P = 0.045) and angiotensin 1 receptor (P = 0.039) were reduced by captopril at day 2. ConclusionCaptopril enhanced early LR. This effect was associated with increased HSC numbers and MMP-9 protein, whereas hepatocyte proliferation was lower than controls. Captopril may provide a beneficial treatment option for the management of patients with CRCLM.