Proteomic analysis of regenerating mouse liver following 50% partial hepatectomy

Role of Fibrinogen-like Protein 1 in Tumor Recurrence Following Hepatectomy

Partial hepatectomy is a first-line treatment for hepatocellular carcinoma. Within 2 weeks following partial hepatectomy, specific molecular pathways are activated to promote liver regeneration. Nevertheless, residual microtumors may also exploit these pathways to reappear and metastasize. Therapeutically targeting molecules that are differentially regulated between normal cells and malignancies, such as fibrinogen-like protein 1 (FGL1), appears to be an effective approach. The potential functions of FGL1 in both regenerative and malignant cells are discussed within the ambit of this review. While FGL1 is normally elevated in regenerative hepatocytes, it is normally downregulated in malignant cells. Hepatectomy does indeed upregulate FGL1 by increasing the release of transcription factors that promote FGL1, including HNF-1α and STAT3, and inflammatory effectors, such as TGF-β and IL6. This, in turn, stimulates certain proliferative pathways, including EGFR/Src/ERK. Hepatectomy alters the phase transition of highly differentiated hepatocytes from G0 to G1, thereby transforming susceptible cells into cancerous ones. Activation of the PI3K/Akt/mTOR pathway by FGL1 allele loss on chromosome 8, a tumor suppressor area, may also cause hepatocellular carcinoma. Interestingly, FGL1 is specifically expressed in the liver via HNF-1α histone acetylase activity, which triggers lipid metabolic reprogramming in malignancies. FGL1 might also be involved in other carcinogenesis processes such as hypoxia, epithelial-mesenchymal transition, immunosuppression, and sorafenib-mediated drug resistance. This study highlights a research gap in these disciplines and the necessity for additional research on FGL1 function in the described processes.

Ubiquitin specific peptidase 47 contributes to liver regeneration

AIMS

Hepatocytes resume proliferation following liver injuries to compensate for the loss of liver mass. Robust liver regeneration is an intrinsic and pivotal process that facilitates restoration of liver anatomy and function. In the present study we investigated the role of ubiquitin-specific peptidase 47 (USP47) in liver regeneration.

METHODS AND MATERIALS

Proliferation of hepatocytes was evaluated by Ki67 staining in vivo and EdU incorporation in vitro. DNA-protein interaction was evaluated by chromatin immunoprecipitation (ChIP).

RESULTS

USP47 expression was up-regulated in hepatocytes isolated from mice subjected to partial hepatectomy (PHx) or exposed to HGF treatment. Ingenuity pathway analysis revealed E2F1 as a primary regulator of USP47 transcription. Reporter assay and ChIP assay confirmed that E2F1 directly bound to the USP47 promoter and activated USP47 transcription. Consistently, E2F1 knockdown abrogated USP47 induction by HGF. Compared to the wild type littermates, USP47 knockout mice displayed compromised liver regeneration following PHx. In addition, USP47 inhibition by a small-molecule compound impaired liver regeneration in mice. On the contrary, USP47 over-expression enhanced proliferation of hepatocytes in vitro and promoted liver regeneration in mice. Importantly, a positive correlation between USP47 expression and hepatocyte proliferation was identified in patients with acute liver failure (ALF).

SIGNIFICANCE

Our data suggest that USP47, transcriptionally activated by E2F1, plays an essential role in liver regeneration.

Aberrant regulation of autophagy disturbs fibrotic liver regeneration after partial hepatectomy

Reports indicate that autophagy is essential for maintaining hepatocyte proliferative capacity during liver regeneration. However, the role of autophagy in fibrotic liver regeneration is incompletely elucidated. We investigated the deregulation of autophagic activities in liver regeneration after partial hepatectomy using a CCl4-induced fibrosis mouse model. The baseline autophagic activity was significantly increased in the fibrotic liver. After 50% partial hepatectomy (PHx), liver regeneration was remarkably decreased, accompanied by increased hepatocyte size and binuclearity ratio. Moreover, the expression of autophagy-related proteins was functionally deregulated and resulted in a reduction in the number of autophagosome and autophagosome-lysosome fusions. We further showed upregulation of autophagy activities through verapamil administration, improved hepatocyte proliferation capacity, and restricted cellular hypertrophy and binuclearity ratio. In conclusion, we demonstrated that the impairment of liver regeneration is associated with aberrant autophagy in fibrotic liver and that enhancing autophagy with verapamil may partially restore the impaired liver regeneration following PHx.

Characteristics of mouse intestinal microbiota during acute liver injury and repair following 50% partial hepatectomy

Dysbiosis of the gut microbiota has important roles in various diseases and pathological states of the host. However, the changes of the gut microbiota during partial hepatectomy (PH)-induced acute liver injury have so far remained elusive. The present study investigated the gut microbiome and its related pathways following PH-induced acute liver injury. A total of 50 male C57/BL6 mice were divided into a normal control (NC), sham-operation and liver resection (LR) group (50% PH). Samples were collected at 3 and 14 days post-operation to obtain specimens for the Sham3, Sham14, LR3 and LR14 groups (10 mice/group). Specimens of NC group (n=10) were obtained at the same time as those of Sham3 group. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined using an automatic chemical analyzer and the gut microbiota was assessed by 16S ribosomal RNA gene sequencing of small intestinal contents. The serum levels of ALT and AST in the LR3 group were significantly increased, while those in the LR14 group were decreased again to near-normal levels. In the LR3 group, the operational taxonomic units, species richness (Chao1) and species diversity (Shannon and Simpson indices) were decreased, although without any significant difference. Furthermore, in the LR3 group, significant Cyanobacteria enrichment and Fusobacteria depletion compared with the NC and Sham3 groups was observed, while in the LR14 group, a significant depletion of the abundance of Verrucomicrobia, Chloroflexi and Deferribacteres compared to the LR3 group was obtained. The abundance of Firmicutes was increased in the LR3 group and decreased again in the LR14 group. However, the abundance of Bacteroidetes and Actinobacteria decreased in the LR3 group and increased again in the LR14 group. The alterations of the gut microbiota at the genus level were also revealed, as significant increases in Chloroplast, Curvibacter, Pelomonas, Ruminococcaceae UCG-005 and Blautia and a sharp decrease in Akkermansia and Eubacterium coprostanoligenes were caused by acute liver injury. Furthermore, functional metagenome prediction was performed by Phylogenetic Investigation of Communities by Reconstruction of Unobserved States based on the Greengenes database, revealing alterations in signal transduction, transcription and cell motility, as well as metabolism of amino acids, lipids, glucose, cofactors and terpenoids, and xenobiotics pathways. An improved understanding of the structural and functional changes of the gut microbiota following 50% PH-induced acute liver injury and repair may provide novel strategies for the recovery of hosts undergoing hepatectomy.

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.

A genetic screen reveals Foxa3 and TNFR1 as key regulators of liver repopulation

Wangensteen et al. employed a parallel screen to test the impact of 43 selected genes on liver repopulation in the Fah^−/− mouse model of hereditary tyrosinemia. The transcription factor Foxa3 was a strong promoter of liver regeneration, while tumor necrosis factor receptor 1 (TNFR1) was the most significant suppressor of repopulation among all of the genes tested.

The fundamental question of which genes are most important in controlling liver regeneration remains unanswered. We employed a parallel screen to test the impact of 43 selected genes on liver repopulation in the Fah^−/− mouse model of hereditary tyrosinemia. We discovered that the transcription factor Foxa3 was a strong promoter of liver regeneration, while tumor necrosis factor receptor 1 (TNFR1) was the most significant suppressor of repopulation among all of the genes tested. Our approach enabled the identification of these factors as important regulators of liver repopulation and potential drug targets for the promotion of liver repopulation.

Vitamin D counteracts fibrogenic TGF-β signalling in human hepatic stellate cells both receptor-dependently and independently

OBJECTIVE

Non-alcoholic fatty liver disease (NAFLD) is closely linked to obesity and constitutes part of the metabolic syndrome, which have been associated with low serum vitamin D (VD). Due to known crosstalk between VD and transforming growth factor (TGF)-β signalling, VD has been proposed as an antifibrotic treatment.

DESIGN

We evaluated the association between VD, the vitamin D receptor (VDR) and liver fibrosis in primary human hepatic stellate cells (phHSC) and 106 morbidly obese patients with NAFLD.

RESULTS

Treating phHSC with VD ameliorated TGF-β-induced fibrogenesis via both VDR-dependent and VDR-independent mechanisms. Reduction of fibrogenic response was abolished in cells homozygous for GG at the A1012G single nucleotide polymorphisms within the VDR gene. Compared with healthy livers, NAFLD livers expressed higher levels of VDR mRNA and VDR fragments. VDR mRNA was lower in patients homozygous for GG at A1012G and expression of pro-fibrogenic genes was higher in patients carrying the G allele.

CONCLUSIONS

VD may be an antifibrotic treatment option early in the onset of fibrosis in specific genotypes for VDR. Known polymorphisms of the VDR may influence the response to VD treatment.

Micron-sized iron oxide-containing particles for microRNA-targeted manipulation and MRI-based tracking of transplanted cells

Particle-based delivery systems for therapeutic manipulation and tracking of transplanted cells by magnetic resonance imaging (MRI) are commonly based on nanometer-sized superparamagnetic iron oxide particles (SPIOs). Here, we present a proof of concept for multifunctional, silica based micron-sized iron oxide-containing particles (sMPIO) that combine fluorescence imaging, MRI tracking, and on-the-spot targeting of specific microRNAs on a particle surface for therapeutic manipulation by RNA interference. Antisense locked nucleic acids (α-LNA) were covalently bound to the surface of silica-based, DAPI-integrated, micron-sized iron oxide particles (sMPIO-α-LNA). In vitro studies using primary human hepatocytes showed rapid particle uptake (4 h) that was accompanied by significant depletion of the targeted microRNA Let7g (80%), up-regulation of the target proteins Cyclin D1 and c-Myc, and specific proteome changes. sMPIO-α-LNA-labeled cells were successfully detected by fluorescence imaging and could be visualized by MRI after intrasplenic transplantation in rats. This new theranostic particle provides a promising tool for cell transplantation where cellular imaging and microRNA-based manipulation is needed. [165].

Proteomic analysis of the regenerating liver following 2/3 partial hepatectomy in rats

Background

Liver regeneration (LR) after 2/3 partial hepatectomy (PH) is one of the most studied models of cell, organ, and tissue regeneration. Although the transcriptional profile analysis of regenerating liver has been carried out by many reserachers, the dynamic protein expression profile during LR has been rarely reported up to date. Therefore, this study aims to detect the global proteomic profile of the regenerating rat liver following 2/3 hepatectomy, thereby gaining some insights into hepatic regeneration mechanism.

Results

Protein samples extracted from the sham-operated and the regenerating rat livers at 6, 12, 24, 72, 120 and 168 h after PH were separated by IEF/SDS-PAGE and then analyzed by MALDI-TOF/TOF mass spectrometry. Compared to sham-operated groups, there were totally 220 differentially expressed proteins (including 156 up-regulated, 62 down-regulated, and 2 up/down-regulated ones) identified in the regenerating rat livers, and most of them have not been previously related to liver regeneration. According to the expression pattern analysis combined with gene functional analysis, it showed that lipid and carbohydrate metabolism were enhanced at the early phase of LR and continue throughout the regeneration process. Ingenuity Pathway Analysis indicated that YWHAE protein (one of members of the 14-3-3 protein family) was located at the center of pathway networks at all the timepoints after 2/3 hepatectomy under our experimental conditions, maybe suggesting a central role of this protein in regulating liver regeneration. Additionally, we also revealed the role of Cdc42 (cell division cycle 42) in the termination of LR.

Conclusions

For the first time, our proteomic analysis suggested an important role of YWHAE and pathway mediated by this protein in liver regeneration, which might be helpful in expanding our understanding of LR amd unraveling the mechanisms of LR.

Electronic supplementary material

The online version of this article (doi:10.1186/0717-6287-47-59) contains supplementary material, which is available to authorized users.

Interleukin 17-producing γδT cells promote hepatic regeneration in mice

BACKGROUND & AIMS

Subsets of leukocytes synergize with regenerative growth factors to promote hepatic regeneration. γδT cells are early responders to inflammation-induced injury in a number of contexts. We investigated the role of γδT cells in hepatic regeneration using mice with disruptions in Tcrd (encodes the T-cell receptor δ chain) and Clec7a (encodes C-type lectin domain family 7 member a, also known as DECTIN1).

METHODS

We performed partial hepatectomies on wild-type C57BL/6, CD45.1, Tcrd(-/-), or Clec7a(-/-) mice. Cells were isolated from livers of patients and mice via mechanical and enzymatic digestion. γδT cells were purified by fluorescence-activated cell sorting.

RESULTS

In mice, partial hepatectomy up-regulated expression of CCL20 and ligands of Dectin-1, which was associated with recruitment and activation of γδT cells and their increased production of interleukin (IL)-17 family cytokines. Recruited γδT cells induced production of IL-6 by antigen-presenting cells and suppressed expression of interferon gamma by natural killer T cells, promoting hepatocyte proliferation. Absence of IL-17-producing γδT cells or deletion of Dectin-1 prevented development of regenerative phenotypes in subsets of innate immune cells. This slowed liver regeneration and was associated with reduced expression of regenerative growth factors and cell cycle regulators. Conversely, exogenous administration of IL-17 family cytokines or Dectin-1 ligands promoted regeneration. More broadly, we found that γδT cells are required for inflammatory responses mediated by IL-17 and Dectin-1.

CONCLUSIONS

γδT cells regulate hepatic regeneration by producing IL-22 and IL-17, which have direct mitogenic effects on hepatocytes and promote a regenerative phenotype in hepatic leukocytes, respectively. Dectin-1 ligation is required for γδT cells to promote hepatic regeneration.

Proteome Analyses of Hepatocellular Carcinoma

Proteomics has evolved into a powerful and widely used bioanalytical technique in the study of cancer, especially hepatocellular carcinoma (HCC). In this review, we provide an up to date overview of feasible proteome-analytical techniques for clinical questions. In addition, we present a broad summary of proteomic studies of HCC utilizing various technical approaches for the analysis of samples derived from diverse sources like HCC cell lines, animal models, human tissue and body fluids.

Proteomic analysis of immediate-early response plasma proteins after 70% and 90% partial hepatectomy

AIM

Partial hepatectomy (PH) induces robust hepatic regenerative and metabolic responses that are considered to be triggered by humoral factors. The aim of the study was to identify plasma protein factors that potentially trigger or reflect the body's immediate-early responses to liver mass reduction.

METHODS

Male C57BL/6 mice were subjected to sham operation, 70% PH or 90% PH. Blood was collected from the inferior vena cava at 20, 60 and 180 min after surgery.

RESULTS

Using a label-free quantitative mass spectrometry-based proteomics approach, we identified 399 proteins exhibiting significant changes in plasma expression between any two groups. Of the 399 proteins, 167 proteins had multiple unique sequences and high peptide ID confidence (>90%) and were defined as priority 1 proteins. A group of plasma proteins largely associated with metabolism is enriched after 70% PH. Among the plasma proteins that respond to 90% PH are a dominant group of proteins that are also associated with metabolism and one known cytokine (platelet factor 4). Ninety percent PH and 70% PH induces similar changes in plasma protein profile.

CONCLUSION

Our findings enable us to gain insight into the immediate-early response of plasma proteins to liver mass loss. Our data support the notion that increased metabolic demands of the body after massive liver mass loss may function as a sensor that calibrates hepatic regenerative response.

Proteomic analysis to display the effect of low doses of erythropoietin on rat liver regeneration

AIMS

Several groups found different impact of erythropoietin (EPO) on liver regeneration. Both pro-proliferative as well as anti-proliferative and non-proliferative activities have been reported using high dosage of EPO. Systemic administration of high doses of this cytokine is a clinical concern due to risk of thrombosis. Herein, we applied EPO in low dosages and investigated whether it can stimulate liver regeneration after liver resection.

MAIN METHODS

Parameters of liver regeneration were assessed 3 days after 70% hepatectomy by means of immunochemistry and proteomics. EPO was given twice in low dosages (200 and 600 IU/kg BW).

KEY FINDINGS

We showed that EPO facilitated hepatic regeneration in rats. Enhanced hepatocyte proliferation (Ki67, BrdU-positive cells) was observed in all EPO-treated groups. By performing Differential Proteomic analysis, we identified two proteins which resulted sensitive to EPO treatment after hepatectomy: Peroxiredoxin-1 and glutathione S-transferase Mu 1.

SIGNIFICANCE

Based on our results, low doses of rhEPO increase the hepatic regenerative capacity after partial hepatectomy in rats by enhancing hepatocyte proliferation and acting on antioxidant enzymes. Both proteins identified by proteomic analysis have not previously been associated with liver regeneration and will aid in the understanding of EPO's regenerative response having clinical implications to treat liver failure.

Proteomic characterization of early changes induced by triiodothyronine in rat liver

High doses of T3 are mitogenic in liver, causing hyperplasia that has numerous differences from the compensatory regeneration induced by partial hepatectomy (PH). T3 binds to the thyroid hormone receptor (TR), which directly regulates transcription, while PH acts indirectly through signal transduction pathways. We therefore carried out a proteomic analysis to compare early effects of the two treatments. Transcriptome analysis by DNA microarray also confirmed the observed proteomic changes, demonstrating that they were caused by transcriptional regulation. Among the differentially expressed proteins, many are directly or indirectly involved in energy metabolism and response to oxidative stress. Several enzymes of lipid metabolism (e.g., Acaa2, Acads, Hadh, and Echs1) were differentially regulated by T3. In addition, altered expression levels of several mitochondrial proteins (e.g., Hspa9, Atp5b, Cps1, Glud1, Aldh2, Ak2, Acads) demonstrated the known increase of mitochondrial biogenesis mediated by T3. The present results provide insights in changes in metabolic balance occurring following T3-stimulation and define a basis for dissecting the molecular pathways of hepatocyte hyperplasia.

Temporal expression profiles indicate a primary function for microRNA during the peak of DNA replication after rat partial hepatectomy

The liver has the unique capacity to regenerate after surgical resection. However, the regulation of liver regeneration is not completely understood. Recent reports indicate an essential role for small noncoding microRNAs (miRNAs) in the regulation of hepatic development, carcinogenesis, and early regeneration. We hypothesized that miRNAs are critically involved in all phases of liver regeneration after partial hepatectomy. We performed miRNA microarray analyses after 70% partial hepatectomy in rats under isoflurane anesthesia at different time points (0 h to 5 days) and after sham laparotomy. Putative targets of differentially expressed miRNAs were determined using a bioinformatic approach. Two-dimensional (2D)-PAGE proteomic analyses and protein identification were performed on specimens at 0 and 24 h after resection. The temporal dynamics of liver regeneration were characterized by 5-bromo- 2-deoxyuridine, proliferating cell nuclear antigen, IL-6, and hepatocyte growth factor. We demonstrate that miRNA expression patterns changed during liver regeneration and that these changes were most evident during the peak of DNA replication at 24 h after resection. Expression of 13 miRNAs was significantly reduced 12–48 h after resection (>25% change), out of which downreguation was confirmed in isolated hepatocytes for 6 miRNAs at 24 h, whereas three miRNAs were significantly upregulated. Proteomic analysis revealed 65 upregulated proteins; among them, 23 represent putative targets of the differentially expressed miRNAs. We provide a temporal miRNA expression and proteomic dataset of the regenerating rat liver, which indicates a primary function for miRNA during the peak of DNA replication. These data will assist further functional studies on the role of miRNAs during liver regeneration.