Hepatocyte growth factor in transgenic mice: effects on hepatocyte growth, liver regeneration and gene expression

Evidence supported by Mendelian randomization: impact on inflammatory factors in knee osteoarthritis

Background

Prior investigations have indicated associations between Knee Osteoarthritis (KOA) and certain inflammatory cytokines, such as the interleukin series and tumor necrosis factor-alpha (TNFα). To further elaborate on these findings, our investigation utilizes Mendelian randomization to explore the causal relationships between KOA and 91 inflammatory cytokines.

Methods

This two-sample Mendelian randomization utilized genetic variations associated with KOA from a large, publicly accessible Genome-Wide Association Study (GWAS), comprising 2,227 cases and 454,121 controls of European descent. The genetic data for inflammatory cytokines were obtained from a GWAS summary involving 14,824 individuals of European ancestry. Causal relationships between exposures and outcomes were primarily investigated using the inverse variance weighted method. To enhance the robustness of the research results, other methods were combined to assist, such as weighted median, weighted model and so on. Multiple sensitivity analysis, including MR-Egger, MR-PRESSO and leave one out, was also carried out. These different analytical methods are used to enhance the validity and reliability of the final results.

Results

The results of Mendelian randomization indicated that Adenosine Deaminase (ADA), Fibroblast Growth Factor 5(FGF5), and Hepatocyte growth factor (HFG) proteins are protective factors for KOA (IVWADA: OR = 0.862, 95% CI: 0.771-0.963, p = 0.008; IVWFGF5: OR = 0.850, 95% CI: 0.764-0.946, p = 0.003; IVWHFG: OR = 0.798, 95% CI: 0.642-0.991, p = 0.042), while Tumor necrosis factor (TNFα), Colony-stimulating factor 1(CSF1), and Tumor necrosis factor ligand superfamily member 12(TWEAK) proteins are risk factors for KOA. (IVWTNFα: OR = 1.319, 95% CI: 1.067-1.631, p = 0.011; IVWCSF1: OR = 1.389, 95% CI: 1.125-1.714, p = 0.002; IVWTWEAK: OR = 1.206, 95% CI: 1.016-1.431, p = 0.032).

Conclusion

The six proteins identified in this study demonstrate a close association with the onset of KOA, offering valuable insights for future therapeutic interventions. These findings contribute to the growing understanding of KOA at the microscopic protein level, paving the way for potential targeted therapeutic approaches.

Modulation of Immune Reaction in Hydrodynamic Gene Therapy for Hemophilia A

Hemophilia A (HA) is a monogenic disease characterized by plasma clotting factor 8 (F8) deficiency due to F8 mutation. We have been attempting to cure HA permanently using a CRISPR-Cas9 gene-editing strategy. Here, we induced targeted integration of BDDF8 (B-domain-deleted F8) gene into the albumin locus of HA mice by hydrodynamic tail vein injection of editing plasmid vectors. One week after treatment, a high F8 activity ranging from 70% to 280% of normal serum levels was observed in all treated HA mice but dropped to background levels 3-5 weeks later. We found that the humoral immune reaction targeting F8 is the predominant cause of the decreased F8 activity. We hypothesized that hydrodynamic injection-induced liver damage triggered the release of large quantities of inflammatory cytokines. However, co-injection of plasmids expressing a dozen immunomodulatory factors failed to curtail the immune reaction and stabilize F8 activity. The spCas9 plasmid carrying a miR-142-3p target sequence alleviated the cellular immune response but was unable to deliver therapeutic efficacy. Strikingly, immunosuppressant cyclo-phosphamide virtually abolished the immune response, leading to a year-long stable F8 level. Our findings should have important implications in developing therapies in mouse models using the hydrodynamic gene delivery approach, highlighting the ne-cessity of modulating the innate immune response triggered by liver damage.

Insights into Growth Factors in Liver Carcinogenesis and Regeneration: An Ongoing Debate on Minimizing Cancer Recurrence after Liver Resection

Hepatocellular carcinoma has become a leading cause of cancer-associated mortality throughout the world, and is of great concern. Currently used chemotherapeutic drugs in the treatment of hepatocellular carcinoma lead to severe side effects, thus underscoring the need for further research to develop novel and safer therapies. Liver resection in cancer patients is routinely performed. After partial resection, liver regeneration is a perfectly calibrated response apparently sensed by the body’s required liver function. This process hinges on the effect of several growth factors, among other molecules. However, dysregulation of growth factor signals also leads to growth signaling autonomy and tumor progression, so control of growth factor expression may prevent tumor progression. This review describes the role of some of the main growth factors whose dysregulation promotes liver tumor progression, and are also key in regenerating the remaining liver following resection. We herein summarize and discuss studies focused on partial hepatectomy and liver carcinogenesis, referring to hepatocyte growth factor, insulin-like growth factor, and epidermal growth factor, as well as their suitability as targets in the treatment of hepatocellular carcinoma. Finally, and given that drugs remain one of the mainstay treatment options in liver carcinogenesis, we have reviewed the current pharmacological approaches approved for clinical use or research targeting these factors.

Liver regeneration in aged mice: new insights

The regenerative capacity of the liver after resection is reduced with aging. Recent studies on rodents revealed that both intracellular and extracellular factors are involved in the impairment of liver mass recovery during aging. Among the intracellular factors, age-dependent decrease of BubR1 (budding uninhibited by benzimidazole-related 1), YAP (Yes-associated protein) and SIRT1 (Sirtuin-1) have been associated to dampening of tissue reconstitution and inhibition of cell cycle genes following partial hepatectomy. Extra-cellular factors, such as age-dependent changes in hepatic stellate cells affect liver regeneration through inhibition of progenitor cells and reduction of liver perfusion. Furthermore, chronic release of pro-inflammatory proteins by senescent cells (SASP) affects cell proliferation suggesting that senescent cell clearance might improve tissue regeneration. Accordingly, young plasma restores liver regeneration in aged animals through autophagy re-establishment. This review will discuss how intracellular and extracellular factors cooperate to guarantee a proper liver regeneration and the possible causes of its impairment during aging. The possibility that an improvement of the liver regenerative capacity in elderly might be achieved through elimination of senescent cells via autophagy or by administration of direct mitogenic agents devoid of cytotoxicity will also be entertained.

Combined Systemic Disruption of MET and Epidermal Growth Factor Receptor Signaling Causes Liver Failure in Normal Mice

MET and epidermal growth factor receptor (EGFR) tyrosine kinases are crucial for liver regeneration and normal hepatocyte function. Recently, we demonstrated that in mice, combined inhibition of these two signaling pathways abolished liver regeneration after hepatectomy, with subsequent hepatic failure and death at 15 to 18 days after resection. Morbidity was associated with distinct and specific alterations in important downstream signaling pathways that led to decreased hepatocyte volume, reduced proliferation, and shutdown of many essential hepatocyte functions, such as fatty acid synthesis, urea cycle, and mitochondrial functions. Herein, we explore the role of MET and EGFR signaling in resting mouse livers that are not subjected to hepatectomy. Mice with combined disruption of MET and EGFR signaling were noticeably sick by 10 days and died at 12 to 14 days. Mice with combined disruption of MET and EGFR signaling mice showed decreased liver/body weight ratios, increased apoptosis in nonparenchymal cells, impaired liver metabolic functions, and activation of distinct downstream signaling pathways related to inflammation, cell death, and survival. The present study demonstrates that, in addition to controlling the regenerative response, MET and EGFR synergistically control baseline liver homeostasis in normal mice in such a way that their combined disruption leads to liver failure and death.

Interventional Potential of Recombinant Feline Hepatocyte Growth Factor in a Mouse Model of Non-alcoholic Steatohepatitis

Background and Aims: Hepatocyte growth factor (HGF) is a multifunctional pleiotropic protein involved in tissue regeneration, protection, angiogenesis, anti-inflammatory and anti-fibrotic responses, and tumorigenesis, through binding to its receptor MET. Recombinant HGF protein has been shown to mitigate various liver disease models, such as alcohol-induced liver injury, hepatic ischemia-reperfusion injury, and fibrosis. This study aimed to investigate the anti-inflammatory, anti-fibrotic, and anti-lipogenic effects of exogenous administration of feline HGF on a non-alcoholic steatohepatitis (NASH) mouse model. Methods: Wild-type C57BL/6 mice were fed a choline-deficient amino acid defined (CDAA) diet for 3 weeks to create the mouse model of NASH, which displays hepatic steatosis, inflammation, injury, and very mild fibrosis. One mg/kg of recombinant feline HGF was administered intravenously daily in the last 7 days of the total 3 weeks of CDAA diet feeding. Then, hepatic steatosis, inflammation, injury, and fibrogenic gene expression was examined. Results: After 3 weeks of a CDAA diet-feeding, the vehicle-treated mice exhibited evident deposition of lipid droplets in hepatocytes, inflammatory cell infiltration, and hepatocyte ballooning along with increased serum ALT levels whereas recombinant HGF-treated mice showed reduced hepatic steatosis, inflammation, and ballooned hepatocytes with a reduction of serum ALT levels. Recombinant HGF administration promoted hepatocyte proliferation. Increased hepatic lipid accumulation was accompanied by elevated expression of lipogenesis genes Fasn and Dgat1 in vehicle-treated mice. In HGF-treated mice, these genes were reduced with a decrease of lipid accumulation in the liver. Consistent with the anti-inflammatory property of HGF, augmented macrophage infiltration and upregulation of chemokines, Cxcl1, Ccl2, and Ccl5 in the CDAA diet fed mice, were suppressed by the addition of the HGF treatment. Finally, we examined the fibrotic response. The vehicle-treated mice had mild fibrosis with upregulation of Col1a1, Acta2, Timp1, Tgfb1, and Serpine1 expression. Recombinant HGF treatment significantly suppressed fibrogenic gene expression and collagen deposition in the liver. Conclusion: Recombinant feline HGF treatment suppressed the progression of NASH in a CDAA diet feeding mouse model.This suggests that recombinant HGF protein has therapeutic potential for NASH.

Biological roles of hepatocyte growth factor-Met signaling from genetically modified animals

Hepatocyte growth factor (HGF) is produced by stromal and mesenchymal cells, and it stimulates epithelial cell proliferation, motility, morphogenesis and angiogenesis in various organs via tyrosine phosphorylation of its cognate receptor, Met. The HGF-Met signaling pathway contributes in a paracrine manner to the development of epithelial organs, exerts regenerative effects on the epithelium, and promotes the regression of fibrosis in numerous organs. Additionally, the HGF-Met signaling pathway is correlated with the biology of cancer types, neurons and immunity. In vivo analyses using genetic modification have markedly increased the profound understanding of the HGF-Met system in basic biology and its clinical applications. HGF and Met knockout (KO) mice are embryonically lethal. Therefore, amino acids in multifunctional docking sites of Met have been exchanged with specific binding motifs for downstream adaptor molecules in order to investigate the signaling potential of the HGF-Met signaling pathway. Conditional Met KO mice were generated using Cre-loxP methodology and characterization of these mice indicated that the HGF-Met signaling pathway is essential in regeneration, protection, and homeostasis in various tissue types and cells. Furthermore, the results of studies using HGF-overexpressing mice have indicated the therapeutic potential of HGF for various types of disease and injury. In the present review, the phenotypes of Met gene-modified mice are summarized.

Heparin-binding epidermal growth factor-like growth factor and hepatocyte growth factor inhibit cholestatic liver injury in mice through different mechanisms

In contrast to hepatocyte growth factor (HGF), the therapeutic potential and pathophysiologic roles of heparin-binding epidermal growth factor-like growth factor (HB-EGF) in liver diseases remain relatively unknown. To address the lack of effective pharmacologic treatments for cholestatic liver injuries, as well as to clarify the biologic features of these growth factors, we explored the effects of HB-EGF and HGF in mice with cholestatic liver injury induced by bile duct ligation (BDL). The mice were assessed 3, 5 and/or 14 days after BDL (acute, subacute and/or chronic phases, respectively) and intravenous injection of adenoviral vector expressing LacZ (control), HB-EGF, HGF, or HB-EGF and HGF. HB-EGF, HGF, or a combination of the growth factors exerted potent antioncotic (antinecrotic), antiapoptotic, anticholestatic, and regenerative effects on hepatocytes in vivo, whereas no robust antiapoptotic or regenerative effects were detected in interlobular bile ducts. Based on serum transaminase levels, the acute protective effects of HB-EGF on hepatocytes were greater than those of HGF. On the other hand, liver fibrosis and cholestasis during the chronic phase were more potently inhibited by HGF compared with HB-EGF. Compared with either growth factor alone, combining HB-EGF and HGF produced greater anticholestatic and regenerative effects during the chronic phase. Taken together, these findings suggest that HB-EGF and HGF inhibited BDL-induced cholestatic liver injury, predominantly by exerting acute cytoprotective and chronic antifibrotic effects, respectively; combining the growth factors enhanced the anticholestatic effects and liver regeneration during the chronic phase. Our results contribute to a better understanding of the pathophysiologic roles of HB-EGF and HGF, as well as to the development of novel effective therapies for cholestatic liver injuries.

Inhibition of the ubiquitin ligase activity improves the production of biologically active fusion protein HSA-HGF in Chinese hamster ovary cells

Hepatocyte growth factor (HGF) is a potent multi-functional protein that stimulates proliferation, survival, motility, scattering and differentiation during growth and development, and has been considered to be a potential therapeutic agent for the treatment of a number of intractable diseases. The aim of this study was to enhance the expression of recombinant fusion protein HSA-HGF (R494E) in CHO cells by inhibiting the intracellular ubiquitin ligase activity. The high stable expression sub-clones with different signal peptides were selected by western blot (WB) analysis and used for suspension culture. We found that the expression of fusion protein HSA-HGF (R494E) on day 3 achieved 50 mg/L during the 8 day culture process, a large number of fusion proteins were intracellular degradated by ubiquitination pathway during day 4 to day 8. Furthermore, ubiquitin ligase inhibitor, thalidomide, was added in culture process, and resulted in efficient and stable secretion of HSA-HGF (R494E) in CHO cells. According to biological activity assays, HSA-HGF (R494E) possessed various biological activities similar to native HGF. In conclusion, innhibition of intracellular ubiquitin ligase activity was successfully improve the expression of biologically active fusion protein HSA-HGF (R494E) in CHO cells. Our data may be beneficial to enhance the production of other therapeutic proteins in fed-batch culture.

Perioperative hepatocyte growth factor (HGF) infusions improve hepatic regeneration following portal branch ligation (PBL) in rodents

BACKGROUND

As hepatic surgery has become safer and more commonly performed, the extent of hepatic resections has increased. When there is not enough expected hepatic reserve to facilitate primary resection of hepatic tumors, a clinical adjunct to facilitating primary resection is portal vein embolization (PVE). PVE allows the hepatic remnant to increase to an appropriate size prior to resection via hepatocyte regeneration; however, PVE is not always successful in facilitating adequate regeneration. One of the strongest trophic factors for hepatocyte regeneration is hepatocyte growth factor (HGF). The purpose of this study was to improve hepatic regeneration with perioperative HGF infusions in an animal model that mimics PVE.

METHODS

Portal branch ligation (PBL) in rodents is equivalent to PVE in humans. We performed left-sided PBL in Sprague-Dawley rodents with the experimental group receiving perioperative HGF infusions. Baseline and postoperative liver volumetrics were obtained with CT scanning methods as performed in clinical practice. Baseline and postoperative liver functions were assessed via indocyanine green (ICG) elimination testing.

RESULTS

HGF infused rodents had statistically significant increase in all postoperative liver volumetrics. Most clinically relevant were increased right liver volumes (RLV), 14.10 versus 7.85 cm³ (p value 0.0001), and increased degree of hypertrophy (DH %), 159.23 versus 47.11 % (p value 0.0079). HGF infused rodents also had a quick return to baseline liver function, 2.38 days compared to 6.13 days (p value 0.0001).

CONCLUSION

Perioperative HGF infusions significantly increase hepatic regeneration following PBL in rodents. Perioperative HGF infusions following PVE are a possible adjunct to increase the amount of patients able to successfully undergo primary resection for hepatic tumors. Further basic science is warranted in examining the use of HGF infusions to increase hepatic regeneration and translating that basic science work to clinical practice.

Trends in the development of MET inhibitors for hepatocellular carcinoma

Hepatocellular carcinoma is the third most common cause of cancer-related deaths worldwide. The multikinase inhibitor sorafenib has improved survival and is now considered the standard of care; however, the benefits are still disappointing, and thus, new effective treatments are required. In human hepatocellular carcinoma, MET, which is encoded by the HGFR gene, is activated by amplification, overexpression or mutation, and it has recently emerged as a possible therapeutic target in various tumors including hepatocellular carcinoma. In fact, some drugs targeting the HGF/MET axis are currently under investigation in clinical trials. Here, we review the role of MET and trends in the development of MET inhibitors for hepatocellular carcinoma.

Met as a therapeutic target in HCC: facts and hopes

Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide, and its burden is expected to increase further in the next years. In spite of the advances of classical therapies, such as surgery, transplantation, use of radiofrequency and transarterial embolization, the prognosis of this neoplasm has not considerably improved over the past few years. The advent of targeted therapies and the approval of the systemic treatment of advanced HCC with the kinase inhibitor sorafenib have provided some hope for the future. Even if the molecular mechanisms responsible for the onset and progression of HCC are still largely unknown, new therapeutic targets have recently come to the spotlight. One of these targets is the tyrosine kinase receptor for the Hepatocyte Growth Factor, encoded by the MET gene, known to promote tumor growth and metastasis in many human organs. In this review we will summarize the contrasting results obtained in vitro (in HCC cell lines) and in animal experimental models and we will also try to analyze the reasons for the opposite findings, suggesting that the HGF/MET axis can have either a promoting or a suppressive role in the development of HCC. We will also reconsider the evidence of activation of this pathway in human HCCs and discuss the results of the clinical trials performed with MET inhibitors. The final purpose is to better clarify which can be the role of MET as a therapeutic target in HCC.

Targeting the HGF/c-MET pathway in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a significant cause of cancer-related morbidity and mortality worldwide. Despite improvements in local therapies, including surgical resection, liver transplantation, and transarterial embolization, the prognosis remains poor for the majority of patients who develop recurrence or present with advanced disease. Systemic therapy with the tyrosine kinase inhibitor sorafenib represents a milestone in advanced HCC but provides a limited survival benefit. Ongoing efforts to study hepatocarcinogenesis have identified an important role for c-MET signaling in the promotion of tumor growth, angiogenesis, and metastasis. In this review, we summarize the preclinical data from human tissue, cell lines, and animal models that implicate c-MET in the pathogenesis of HCC. We also evaluate potential biomarkers that may estimate prognosis or predict response to c-MET inhibitors for more rational clinical trial design. Finally, we discuss the latest clinical trials of c-MET inhibitors in advanced HCC.

Therapeutic potentials occurring during the early differentiation process of mesenchymal stem cells in a rats model with thioacetamide-induced liver fibrosis

BACKGROUNDS/AIMS

Mesenchymal stem cells (MSCs) have the capacity to differentiate into hepatocytes, The purpose of this study is to investigate the MSCs' differentiation process and therapeutic potentials by comparing isolated MSCs with HGF-treated MSCs in rat's model with thiacetamide (TAA)-induced cirrhosis.

METHODS

Male Sprague-Dawley (SD) rats, weighing 100-150 g were used in this study. To induce liver fibrosis, recipient rats were taken with 0.04% thioacetamide (TAA) in the drinking water (400 mg TAA/L) for 8 weeks. The rats underlying liver cirrhosis were divided into 3 groups according to the transplanted materials, compared to normal saline as control (I) and isolated MSCs (II) HGF-treated MSCs.

RESULTS

Severe hepatic fibrosis and hepatocyte destruction were detected in the control group. Less hepatic cirrhosis and collagen formation, more hepatocyte regeneration and glycogen storage were detected in isolated MSCs compared to HGF-treated MSCs group, Distribution of red autofluorescence is mainly localized near the sinusoids in isolated MSCs, scattered away the sinusoids in HGF-treated MSCs group. MSCs transdifferentiated into CK-19 postive Oval cells and then to albulmin-producing hepatocytes, HGF treated MSCs differentiated into hepatocyte without the intermediate oval cells phase. HGF treated MSCs became the CK18-positive, MSCs became CD 90-positive.

CONCLUSIONS

Significant hepatocyte differentiation occurred in not HGF-treated MSCs but isolated MSCs group unexpectedly. These results suggest that the beneficial effect of MSCs on in rat's model with TAA-induced cirrhosis may occur during early differentiation course of MSCs. Mature hepatocyte itself has a little effect on the accelerated differentiation and functional capacity of hepatic lineage cell-line.

c-Met: A potential therapeutic target for hepatocellular carcinoma

The approval of receptor tyrosine kinase (RTK) targeted agent sorafenib as the first effective drug for the systemic treatment of advanced hepatocellular carcinoma (HCC) represents a milestone in the treatment of this disease. A better understanding of HCC pathogenesis will lead to development of novel targeted treatments. As a typical member of the RTK family, c-Met represents an intriguing target for cancer therapy. The c-Met signaling pathway has been shown to be deregulated and to correlate with poor prognosis in a number of major human cancers. This review discusses the possibility of c-Met as a target in HCC treatment from the following respects: i) c-Met expression and activation profile in HCC, ii) relationship between c-Met and clinicopathologic state and prognosis of HCC, iii) role of c-Met signaling activity in HCC genesis and progression, and iv) strategy of c-Met pathway targeting therapy in HCC treatment.

No contribution of umbilical cord mesenchymal stromal cells to capillarization and venularization of hepatic sinusoids accompanied by hepatic differentiation in carbon tetrachloride-induced mouse liver fibrosis

BACKGROUND AIMS

The acceleration of capillarization and venularization of hepatic sinusoids after cell therapy would not be beneficial to restoration after liver disease. The goal was to observe the effects of umbilical cord (UC)-derived mesenchymal stromal cells (MSC) on liver microcirculation and their therapeutic potential in liver fibrosis.

METHODS

Human UC MSC labeled with or without CM-DIL were transplanted into NOD/SCID mice with carbon tetrachloride (CCl4)-induced chronic liver fibrosis models. Because of the high autofluorescence on the injured liver sections, we used immunohistochemistry, Western blot and reverse transcriptase-polymerase chain reaction (RT-PCR), but not immunofluorescence, in order to avoid false images under a confocal fluorescence microscope.

RESULTS

Human-specific alpha-fetoprotein and albumin mRNA and proteins were detected in CCl4-treated mouse livers receiving human UC MSC transplants. We only observed the gene expression of human-specific endothelial-like cells markers CD31 and KDR by RT-PCR, but not protein expression by immunohistochemistry, in UC MSC-transplanted mouse livers. Vascular endothelial growth factor (VEGF) expression in injured livers 4 weeks after UC MSC transplantation was higher than in normal livers. However, UC MSC injection did not increase significantly the vascular density labeled by CD31 and (vWF) in the injured livers of UC MSC-transplanted mice compared with non-transplanted mice after CCl4 treatment. In addition, liver function was partly improved after UC MSC transplantation.

CONCLUSIONS

Human UC MSC can differentiate into hepatocyte-like cells but do not accelerate the capillarization and venularization of hepatic sinusoids, finally leading to the partial improvement of liver function in mice with CCl4-mediated chronic liver fibrosis.

Hepatocyte growth factor mobilizes and recruits hematopoietic progenitor cells into liver through a stem cell factor-mediated mechanism

AIMS

Although bone marrow cells are reported to migrate to the liver under circumstances of severe liver injury, the bone marrow cell type and the mechanisms in this process, remain to be clarified. We examined the involvement of hepatocyte growth factor (HGF) in this process and the cell type of migrated hematopoietic cells by HGF.

METHODS

The CD34(+) cells and colony forming cells in the peripheral blood were examined in HGF transgenic, recombinant HGF-administered, and HGF-expressing adenovirus-administered mice. The cell type mobilized by HGF was examined by the percentages of donor cells in the peripheral blood of the recipient mice transplanted with Lin(-)c-kit(+)Sca-1(+)CD34(+) cells and those with Lin(-)c-kit(+)Sca-1(+)CD34(-) cells. Expression of stem cell factor (SCF) was examined after the addition of HGF in MS-5 stromal cells. The numbers of the cells which were mobilized from bone marrow and recruited into liver by HGF were assessed using green fluorescence fluorescent (GFP)-chimera mice.

RESULTS

Mobilized CD34+ cells and colony forming cells in the peripheral blood were increased by HGF treatment. The cells mobilized by HGF were mostly Lin(-)c-kit(+)Sca-1(+)CD34(+) cells. Recruitment of bone marrow cells into liver was not suppressed in MMP-9-/- mice. Expression of SCF was induced by HGF in MS-5 stromal cells. However, expression of CXCR4, SDF-1, MMP-9 or VCAM-1 was not changed. The numbers of GFP-positive cells in liver 1 month after treatment by HGF was greater than that by G-CSF.

CONCLUSION

The results of the present study suggest that HGF mobilizes and recruits hematopoietic progenitor cells from bone marrow into the liver through SCF-mediated mechanism.

Serum HGF and TGF-beta1 levels after right portal vein embolization

AIM

The changes in the serum hepatocyte growth factor (HGF) and transforming growth factor (TGF)-beta1 levels after portal vein embolization (PVE), and their clinical significance, remain unclear and we aimed to assess their relationship.

METHODS

The serum HGF and TGF-beta1 levels were prospectively measured in 22 patients before and 1, 3, 5, 7, and 14 day after right PVE. Computed tomographic volumetry was performed before and at a mean of 26 +/- 4 days after right PVE.

RESULTS

Three to four weeks after right PVE, the volume of embolized lobe significantly decreased from 704 +/- 157 cm(3) before PVE to 539 +/- 168 cm(3) after PVE (P < 0.001). In contrast, the volume of nonembolized lobe significantly increased from 426 +/- 142 cm(3) to 560 +/- 165 cm(3) (P < 0.001). The serum HGF level significantly increased on day 3 after PVE compared with the pretreatment level (P = 0.005), while the serum TGF-beta1 level significantly decreased and reached its lowest value on day 3 (P = 0.002). Using Pearson's correlation analysis, we found that the serum HGF and TGF-beta1 levels on day 14 negatively associated with the large hypertrophic response in the nonembolized lobe (HGF: r = -0.490, P = 0.021; TGF-beta1: r = -0.473, P = 0.026).

CONCLUSIONS

PVE induced an increase in the serum HGF level and reduced the serum TGF-beta1 level. Measurement of serum HGF and TGF-beta1 levels on day 14 after right PVE may be useful for assessment of the future liver hypertrophy in nonembolized lobe after right PVE.

Low-dose simultaneous delivery of adenovirus encoding hepatocyte growth factor and vascular endothelial growth factor in dogs enhances liver proliferation without systemic growth factor elevation

BACKGROUND

Hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) gene transfer proved to enhance liver regeneration. However, elevation of their plasma levels may induce potentially serious distant effects such as tumorigenesis or proliferative retinopathy.

AIMS

This study was performed to examine whether simultaneous administration of low-dose adenovirus encoding HGF and VEGF genes in dogs will stimulate liver proliferation but without inducing liver toxicity or systemic elevation of HGF and VEGF levels.

METHODS

Adult dogs received an intravenous injection of low-dose adenoviral vectors encoding human HGF and VEGF (HGF/VEGF), beta-galactosidase (lacZ) or phosphate-buffered saline (PBS). Liver proliferation was measured using the proliferating cell nuclear antigen (PCNA) immunostaining labelling index. HGF and VEGF plasma concentrations and transaminases were repeatedly measured. Transgene expression was evaluated using reverse-transcription polymerase chain reaction.

RESULTS

Human HGF and VEGF expressions were detected only in the liver of HGF/VEGF dogs at day 2 after injection but declined at sacrifice (day 7). No expression was detected in the liver of the lacZ or PBS groups. Plasma levels of HGF and VEGF were not statistically different from those in the lacZ group (P=0.81, P=0.22 respectively). The PCNA labelling index was five-fold higher in the HGF/VEGF group compared with the lacZ group (P<0.01). No immunostaining was detected in the PBS group. Transaminases were only elevated (P<0.01) in the lacZ group compared with the other groups.

CONCLUSIONS

We showed that simultaneous administration of low-dose adenoviral vectors encoding human HGF and VEGF genes can induce transgene expression and liver proliferation without liver toxicity or systemic growth factor elevation.

Experimental models of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a common and deadly cancer whose pathogenesis is incompletely understood. Comparative genomic studies from human HCC samples have classified HCCs into different molecular subgroups; yet, the unifying feature of this tumor is its propensity to arise upon a background of inflammation and fibrosis. This review seeks to analyze the available experimental models in HCC research and to correlate data from human populations with them in order to consolidate our efforts to date, as it is increasingly clear that different models will be required to mimic different subclasses of the neoplasm. These models will be instrumental in the evaluation of compounds targeting specific molecular pathways in future preclinical studies.

Clinical impact of serum transforming growth factor-alpha mRNA as a predictive biomarker for the prognosis of fulminant hepatitis

PURPOSE

We previously reported that measuring serum telomerase reverse transcriptase (hTERT) mRNA with a quantitative, one-step, real-time RT-PCR was superior to conventional tumor markers for hepatocellular carcinoma and lung cancer. Here, we examined serum regeneration-related mRNA detection as a biomarker for fulminant hepatitis (FH).

METHODS

In 53 patients, including 17 patients with acute hepatitis (AH), seven with severe hepatitis (SH), four with late-onset hepatic failure (LOHF), and 25 with FH, we measured serum mRNA levels of hTERT, hepatocyte growth factor (HGF), hepatocyte growth factor receptor (c-met), epidermal growth factor receptor (EGFR), and transforming growth factor-alpha (TGF-alpha). We examined the sensitivity and specificity of the technique in FH diagnosis as well as its clinical and prognostic significance compared with other clinical and prognostic tests.

RESULTS

Serum copy number of TGF-alpha mRNA in FH on admission was significantly smaller than in AH and SH. In FH, TGF-alpha mRNA level was 10(6)-fold higher in survivors than in patients who died or received liver transplants (P = 0.034), although these patients were not discriminated by other clinical parameters. The sensitivity/specificity for prognosis in FH was 74.3/65.5% for TGF-alpha mRNA. Of four prognostic scoring systems, only logit-lambda was useful for prognosis assessment.

CONCLUSIONS

TGF-alpha mRNA is an early predictor of FH outcome and a sensitive biomarker of lower regenerative liver capacity. This assay could help facilitate early therapy choice, such as liver transplantation.

Hepatocyte growth factor suppresses profibrogenic signal transduction via nuclear export of Smad3 with galectin-7

BACKGROUND & AIMS

Hepatocyte growth factor (HGF) and transforming growth factor-beta (TGF-beta) regulate diversified cellular functions and often act antagonistically against each other. For example, TGF-beta is the most potent factor accelerating liver fibrosis, whereas HGF treatment prevents its progression. Here, we propose a novel molecular mechanism by which HGF counter represses TGF-beta-stimulated profibrogenic signal transduction.

METHODS

Effects of HGF on TGF-beta-responsive gene transcription of type I collagen, the major matrix component of fibrotic liver, were examined by using cultured hepatic stellate cells (HSC) and transgenic mice harboring alpha2(I) collagen gene (COL1A2) promoter. Expression and subcellular localization of Smad3 were determined by Western blot analyses and immunofluorescence staining, respectively. A mass spectrometric analysis was employed to identify immunoprecipitated proteins with antiphospho-Smad2/3 antibodies.

RESULTS

Over expression of HGF inhibited COL1A2 transcription in cultured HSC and suppressed activation of COL1A2 promoter in liver tissue induced by carbon tetrachloride administration. A mass spectrometric analysis identified galectin-7 as one of the immunoprecipitated proteins with antiphospho-Smad2/3 antibodies following HGF treatment. HGF accelerated nuclear export of Smad3 by enhancing its interaction with galectin-7. Transfection of cells with galectin-7 small interfering RNA inhibited nuclear export of Smad3 and abolished suppressive effect of HGF on expression of TGF-beta-responsive genes such as COL1A2 and plasminogen activator inhibitor-1. On the other hand, over expression of galectin-7 suppressed TGF-beta-stimulated expression of those target genes.

CONCLUSIONS

These results reveal a novel function of intracellular galectin-7 as a transcriptional regulator via its interaction with Smad3 and provide a molecular basis for the antifibrotic effect of HGF.

Loss of hepatocyte growth factor/c-Met signaling pathway accelerates early stages of N-nitrosodiethylamine induced hepatocarcinogenesis

Hepatocyte growth factor (HGF) has been reported to have both positive and negative effects on carcinogenesis. Here, we show that the loss of c-Met signaling in hepatocytes enhanced rather than suppressed the early stages of chemical hepatocarcinogenesis. c-Met conditional knockout mice (c-metfl/fl, AlbCre+/-; MetLivKO) treated with N-nitrosodiethylamine developed significantly more and bigger tumors and with a shorter latency compared with control (w/w, AlbCre+/-; Cre-Ctrl) mice. Accelerated tumor development was associated with increased rate of cell proliferation and prolonged activation of epidermal growth factor receptor (EGFR) signaling. MetLivKO livers treated with N-nitrosodiethylamine also displayed elevated lipid peroxidation, decreased ratio of reduced glutathione to oxidized glutathione, and up-regulation of superoxide dismutase 1 and heat shock protein 70, all consistent with increased oxidative stress. Likewise, gene expression profiling done at 3 and 5 months after N-nitrosodiethylamine treatment revealed up-regulation of genes associated with cell proliferation and stress responses in c-Met mutant livers. The negative effects of c-Met deficiency were reversed by chronic p.o. administration of antioxidant N-acetyl-L-cysteine. N-acetyl-L-cysteine blocked the EGFR activation and reduced the N-nitrosodiethylamine-initiated hepatocarcinogenesis to the levels of Cre-Ctrl mice. These results argue that intact HGF/c-Met signaling is essential for maintaining normal redox homeostasis in the liver and has tumor suppressor effect(s) during the early stages of N-nitrosodiethylamine-induced hepatocarcinogenesis.

Role of hepatocyte growth factor/c-Met signaling in regulating urokinase plasminogen activator on invasiveness in human hepatocellular carcinoma: a potential therapeutic target

Hepatocyte growth factor (HGF), its transmembrane tyrosine kinase receptor (c-Met), and urokinase type plasminogen activator (uPA) is a key protein in the plasminogen activation system, which plays a proteolytically important role in the invasion and metastasis of various types of cancers. However, the mechanisms by which HGF/c-Met signaling mediates cancer progression and metastasis are unclear. This study was designed to investigate the roles of HGF/c-Met in tumor progression and metastasis in HepG2 and Hep3B hepatoma cell lines. Treatment with HGF increased c-Met phosphorylation in a dose-dependent manner. Activity of c-Met phosphorylation peaked 1-3 min after HGF treatment and then declined. HGF enhanced the protein level and the activity of uPA in HepG2 and Hep3B cells, and the uPAR protein level also increased in a HGF dose-dependent manner. HGF increased cell invasion through the Matrigel. A monoclonal antibody against human uPA receptor, mAb 3936, inhibited HGF-mediated tumor cell invasion in a dose-dependent manner. Down-regulation of uPA using uPA-shRNA induced a decrease in in vitro cell invasion. These results suggest that hepatoma cells express functional c-Met, which may provide a target for a therapeutic basis to interfere with metastases of cancer cells by inhibiting uPA system-mediated proteolysis.

Adenoviral vector expressing hepatocyte growth factor promotes liver regeneration by preoperative injection: the advantages of performing selective injection to the remnant lobe

BACKGROUND

In a cirrhotic liver, the regenerative ability is impaired and liver failure may occur after a hepatectomy. Hepatocyte growth factor (HGF) stimulates liver regeneration and adenoviral vector expressing hepatocyte growth factor (AdHGF) allows hepatocyte growth factor (HGF) to be persistently expressed. The aim of this study is to evaluate the benefits of the selective and preoperative injection of AdHGF to the remnant lobes to regenerate the liver.

METHODS

A 70% partial hepatectomy was performed in dimethylnitrosamine-induced cirrhotic rats with a preoperative injection of AdHGF, adenoviral vector carrying beta-galactosidase (AdLacZ), or phosphate-buffered saline (PBS). The morphologic, histologic, and biochemical changes in the remnant liver and survival rates were then assessed.

RESULTS

Portal injection with clamping the portal branches of the resected lobes for 5 min made it possible to effectively transduce the adenoviral vector into the remnant lobes. On day 7 after hepatectomy, the survival rates were 87% in the AdHGF group, 53% in the AdLacZ group, and 40% in the PBS group (P < .05). The ratio of the remnant liver weight/body weight (%) was 2.0 +/- 0.1 in the AdHGF group, 1.5 +/- 0.3 in the AdLacZ group, and 1.6 +/- 0.04 in the PBS group (P < .01). The 5-bromo-2'-deoxyuridine labeling index significantly increased in the AdHGF group on day 1, and the fibrous status significantly decreased in the AdHGF group on day 7 after hepatectomy.

CONCLUSIONS

Preoperatively, the selective injection of AdHGF into the remnant lobes may be an effective treatment prior to a major hepatectomy in a cirrhotic liver.

Bone marrow-derived cells express matrix metalloproteinases and contribute to regression of liver fibrosis in mice

Liver fibrosis is usually progressive, but it can occasionally be reversible if the causative agents are adequately removed or if patients are treated effectively. However, molecular mechanisms responsible for this reversibility of liver fibrosis have been poorly understood. To reveal the contribution of bone marrow (BM)-derived cells to the spontaneous regression of liver fibrosis, mice were treated with repeated carbon tetrachloride injections after hematopoietic reconstitution with enhanced green fluorescent protein (EGFP)-expressing BM cells. The distribution and characteristics of EGFP-positive (EGFP(+)) cells present in fibrotic liver tissue were examined at different time points after cessation of carbon tetrachloride intoxication. A large number of EGFP(+) cells were observed in liver tissue at peak fibrosis, which decreased during the recovery from liver fibrosis. Some of them, as well as EGFP-negative (EGFP(-)) liver resident cells, expressed matrix metalloproteinase (MMP)-13 and MMP-9. Whereas MMP-13 was transiently expressed mainly in the cells clustering in the periportal areas, MMP-9 expression and enzymatic activity were detected over the resolution process in several different kinds of cells located in the portal areas and along the fibrous septa. Therapeutic recruitment of BM cells by granulocyte colony-stimulating factor (G-CSF) treatment significantly enhanced migration of BM-derived cells into fibrotic liver and accelerated the regression of liver fibrosis. Experiments using transgenic mice overexpressing hepatocyte growth factor (HGF) indicated that G-CSF and HGF synergistically increased MMP-9 expression along the fibrous septa.

CONCLUSION

Autologous BM cells contribute to the spontaneous regression of liver fibrosis, and their therapeutic derivation could be a new treatment strategy for intractable liver fibrosis.

Mechanisms of aging and liver functions

BACKGROUND/AIMS

Morphofunctional studies suggest that the liver, compared with other organs, ages fairly well. Its success is ascribable to its lasting ability to regenerate, even if the potential of the cells to replicate progressively declines with age. The aim of this study was to analyze some aspects of the early phases of liver regeneration, its capacity to mount a stress response, and the inflammatory response in the early stage of an acute injury.

METHODS

Rats aged 2, 6, 12 and 19 months received a single intraperitoneal injection of CCl(4), and morphological, biochemical and molecular evaluations were done 2 and 24 h later.

RESULTS

AST and ALT, starting at age 12 months, were significantly higher than in the younger rats after CCl(4). Histological modifications were already detectable after 2 h in rats aged 12 and 19 months, thereafter becoming more diffuse and marked, whereas they become evident only 24 h after the intoxication in rats aged 2 and 6 months. Albumin, c-fos, c-myc, hepatocyte growth factor, transforming growth factor-alpha and HSP70 mRNA levels decreased 24 h after CCl(4 )starting at age 12 months. Mast cell density was higher in the young rats than the old ones.

CONCLUSION

Our results point to: (a) a basically preserved regenerative response of the aged liver, although somehow weaker and slower, with reduced ability to counteract agents inducing cell necrosis; (b) a decrease in the HSP70 response suggesting a reduction in homeostatic capacity, and (c) a lower inflammatory response during aging.

Combination gene therapy of HGF and truncated type II TGF-beta receptor for rat liver cirrhosis after partial hepatectomy

BACKGROUND

In a cirrhotic liver, the regenerative ability and specific functions are impaired; a hepatic resection increases the possibility of postoperative liver failure. Hepatocyte growth factor (HGF) stimulates liver regeneration, accelerates restoration of hepatic function, and improves fibrosis. A truncated type II transforming growth factor-beta receptor (TbetaTR), which specifically inhibits TGF-beta signaling as a dominant-negative receptor, appears to prevent the progression of liver fibrosis. We demonstrated the therapeutic efficacy of adenovirus-mediated HGF and TbetaTR gene transduction after partial hepatectomy for liver cirrhosis.

METHODS

Rats were treated with dimethylnitrosamine for 3 weeks, and they all had severe cirrhosis. After partial hepatectomy (10%), we injected adenovirus expressing bacterial beta-galactosidase (AdLacZ), adenovirus expressing a truncated type II TGF-beta receptor (AdTbetaTR), adenovirus expressing hepatocyte growth factor (AdHGF), or AdTbetaTR + AdHGF into the portal vein, which was followed by an additional 2-week dimethylnitrosamine treatment.

RESULTS

On histologic examination, fibrotic tissue had decreased in the livers of the AdTbetaTR + AdHGF-treated rats compared with rats that were treated by AdLacZ, AdTbetaTR alone, and AdHGF alone. Liver function, which included serum levels of alanine aminotransferase, improved significantly in AdTbetaTR + AdHGF-treated rats compared with all other groups. The number of hepatocytes that were positive for proliferating-cell nuclear antigen was greater (P < .05) in AdHGF alone and AdTbetaTR + AdHGF-treated rat livers than in AdLacZ- and AdTbetaTR-treated rats. All AdTbetaTR + AdHGF-treated rats survived >60 days, and AdTbetaTR + AdHGF treatment markedly improved the survival rate after a partial hepatectomy.

CONCLUSION

Our results suggest that the combination of HGF and TbetaTR gene therapy may increase the possibility of hepatectomy in a cirrhotic liver by improving fibrosis, hepatic function, and hepatocyte regeneration.

Progenitor cells in liver regeneration: molecular responses controlling their activation and expansion

Although normally quiescent, the adult mammalian liver possesses a great capacity to regenerate after different types of injuries in order to restore the lost liver mass and ensure maintenance of the multiple liver functions. Major players in the regeneration process are mature residual cells, including hepatocytes, cholangiocytes and stromal cells. However, if the regenerative capacity of mature cells is impaired by liver-damaging agents, hepatic progenitor cells are activated and expand into the liver parenchyma. Upon transit amplification, the progenitor cells may generate new hepatocytes and biliary cells to restore liver homeostasis. In recent years, hepatic progenitor cells have been the subject of increasing interest due to their therapeutic potential in numerous liver diseases as alternative or supportive/complementary tools to liver transplantation. While the first investigations on hepatic progenitor cells have focused on their origin and phenotypic characterization, recent attention has focused on the influence of the hepatic microenvironment on their activation and proliferation. This microenvironment comprises the extracellular matrix, epithelial and non-epithelial resident liver cells, and recruited inflammatory cells as well as the variety of growth-modulating molecules produced and/or harboured by these elements. The cellular and molecular responses to different regenerative stimuli seem to depend on the injury inflicted and consequently on the molecular microenvironment created in the liver by a certain insult. This review will focus on molecular responses controlling activation and expansion of the hepatic progenitor cell niche, emphasizing similarities and differences in the microenvironments orchestrating regeneration by recruitment of progenitor cell populations or by replication of mature cells.

Overexpression of NK2 inhibits liver regeneration after partial hepatectomy in mice

AIM

To investigate the in vivo effects of NK2 on liver regeneration after partial hepatectomy (PH).

METHODS

Survival after PH was observed with 21 NK2 transgenic mice and 23 wild-type (WT) mice over 10 d. Liver regeneration was analyzed using histology and immunohistochemistry. Expressions of genes were analyzed using Northern blot analysis, immunoprecipitation and immunoblotting, and reverse transcriptase polymerase chain reaction assay. Kaplan-Meier method and the log-rank test were used for analyzing the survival after PH. Differences in the results of immunohistochemistry and percentage of liver regeneration was determined by the Student's t-test.

RESULTS

More than half of NK2 transgenic mice died within 48 h after PH. After PH, increased deposition of small lipid droplets in hepatocytes was evident and hepatic proliferation was inhibited in NK2 transgenic mice. The hepatic expression and kinase activity of HGF receptor, c-Met, were unchanged among WT mice and NK2 transgenic mice after PH. The expression of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) in liver tissues were prolonged in NK2 transgenic mice that died after PH.

CONCLUSION

Our findings indicate that over-expression of NK2 inhibits liver regeneration after PH.

Endothelial progenitor cell transplantation improves the survival following liver injury in mice

BACKGROUND & AIMS

Neovascularization, which is vital to the healing of injured tissues, recently has been found to include both angiogenesis, which involves in mature endothelial cells, and vasculogenesis, involving endothelial progenitor cells. The aim of this study was to clarify the possible roles of endothelial progenitor cells during postnatal liver regeneration.

METHODS

To determine how endothelial progenitor cells participate in liver regeneration, human or mouse endothelial progenitor cells were transplanted into the mice with carbon tetrachloride-induced acute liver injury. Survival rate of the mice in endothelial progenitor cell-transplanted and control groups was calculated. Separately, livers removed temporally from both groups were examined.

RESULTS

At an early stage, transplanted human endothelial progenitor cells were seen mainly surrounding hepatic central veins where hepatocytes showed extensive necrosis; later, the transplanted cells formed tubular structures. More of these cells were observed along hepatic sinusoids. Transplantation of human or mouse endothelial progenitor cells improved survival of the mice following liver injury (from 28.6% to 85.7%, P < .0005 and from 33.3% to 80.0%, P < .001, respectively), accompanied by greater proliferation of hepatocytes. Human endothelial progenitor cells produced several growth factors, such as hepatocyte growth factor, transforming growth factor-alpha, heparin-binding epidermal growth factor-like growth factor, and vascular endothelial growth factor, and also elicited endogenous growth factors.

CONCLUSIONS

Endogenous and exogenous growth factors and direct neovascularization after endothelial progenitor cell transplantation promoted liver regeneration, thus improving survival after liver injury. Transplantation of endothelial progenitor cells could represent a new therapeutic strategy for promoting liver regeneration.

Activation of hepatocyte growth factor by urokinase-type plasminogen activator is ionic strength-dependent

The hepatocyte growth factor (HGF) is a multifunctional cytokine that is produced as latent scHGF (single chain HGF). Various proteases reportedly cleave scHGF to generate the active two-chain form (HGF), including u-PA (urokinase-type plasminogen activator), t-PA (tissue-type plasminogen activator), kallikrein, Factor XIa, Factor XIIa, HGF activator and matriptase. Considerable evidence indicates that, in vivo, u-PA activates scHGF in the liver; however, the in vivo results have not been uniformly supported by in vitro experiments. We now report that cleavage of scHGF by high-molecular-mass u-PA (abbreviated u-PA throughout) is sensitive to ionic strength. scHGF cleavage by u-PA was accelerated as the ionic strength was decreased. This result was equivalent irrespective of whether the predominant anion was chloride or acetate. Lmw-u-PA (low-molecular-mass u-PA) was ineffective at cleaving scHGF, regardless of ionic strength. Although scHGF shares homology with plasminogen, EACA (-amino-caproic acid) did not regulate u-PA-mediated scHGF cleavage. Soluble HGF receptor (MET) and soluble u-PAR (u-PA receptor) inhibited the scHGF cleavage. These results support a model in which the ability of u-PA to activate scHGF in vivo may be highly dependent on local conditions within the extracellular space.

Hepatocyte growth factor (HGF) in patients with hepatitis B and meningitis

OBJECTIVES

The present study investigates serum hepatocyte growth factor (HGF) levels in patients with acute and chronic hepatitis B and the relation between these levels and intrahepatic inflammatory markers of the liver and fibrosis, as well as the cerebrospinal fluid (CSF) HGF levels in patients with meningitis and the relation between these levels and CSF findings. To our knowledge this is the first study regarding CSF HGF levels in tuberculous meningitis.

PATIENTS AND METHODS

The study consisted of 35 patients with chronic hepatitis B (HbeAg and HBV-DNA positive), 20 with acute hepatitis B, 20 with acute bacterial meningitis and 15 having tuberculous meningitis. HGF levels in the serum and CSF samples were measured by using the ELISA method.

RESULTS

The mean serum HGF levels in acute hepatitis B group were found statistically significantly higher than those in the control group and chronic hepatitis B group (p<0.0001). It was established that serum HGF levels in patients with chronic hepatitis B were significantly correlated with serum alanine aminotransferase (ALT) and HBV-DNA levels (r: 0.816, 0.951; p<0.05, respectively). Similarly, serum HGF levels of patients with chronic hepatitis B were correlated with fibrosis score and hepatic activity index of the liver histopathology (r: 0.750, 0.459; p<0.05, respectively). The mean CSF HGF levels of patients with acute bacterial meningitis and tuberculous meningitis were higher than those in the control group (p<0.05). In addition, it was observed that mean CSF HGF levels in patients suffered from tuberculous meningitis were statistically significantly higher than those in acute bacterial meningitis (p<0.05).

CONCLUSIONS

We suggest that serum HGF level in patients with chronic hepatitis B might reflect viral load, necro-inflammatory activity in the liver and the degree of structural progression. Our findings have demonstrated that tuberculous meningitis cause increased HGF concentrations in CSF. It is, therefore, suggested that examination of HGF levels in CSF may provide additional information in the differential diagnosis.

Treatment with leucine stimulates the production of hepatocyte growth factor in vivo

Hepatocyte growth factor (HGF) has pleiotropic effects. Up-regulation of HGF activity in vivo may be beneficial. Branched-chain amino acids (BCAAs) are known to modulate various cellular functions. When starved rats received intraperitoneal injections of valine, leucine or isoleucine, only leucine treatment increased both hepatic and circulating levels of HGF in a dose-dependent manner, up to 1.5 and 2.3 times higher, respectively, than in controls. When young growing rats with free access to food were injected with leucine once a day for a week, HGF levels and liver weights were significantly higher than those of control rats. Furthermore, 1 week of leucine treatment of adult rats resulted in elevated serum albumin levels with an increase in HGF levels. Taken together with our previous report showing that leucine stimulates HGF production by hepatic stellate cells in culture, leucine, among BCAAs, may induce an increase in HGF production by the liver in vivo.

Met provides essential signals for liver regeneration

Genetic analysis in mice has demonstrated a crucial role of the Met tyrosine kinase receptor and its ligand, hepatocyte growth factor/scatter factor (HGF/SF), in development of the liver, muscle, and placenta. Here, we use conditional mutagenesis in mice to analyze the function of Met during liver regeneration, using the Mx-cre transgene to introduce the mutation in the adult. After partial hepatectomy in mice carrying the Mx-cre-induced Met mutation, regeneration of the liver is impaired. Comparison of signal transduction pathways in control and mutant livers indicates that Met and other signaling receptors cooperate to fully activate particular signaling molecules, for instance, the protein kinase Akt. However, activation of the Erk1/2 kinase during liver regeneration depends exclusively on Met. Signaling crosstalk is thus an important aspect of the regulation of liver regeneration. Analysis of cell cycle progression of hepatocytes in conditional Met mutant mice indicates a defective exit from quiescence and diminished entry into S phase. Impaired liver regeneration is accompanied by compensatory physiological responses that include prolonged up-regulation of HGF/SF and IL-6 in peripheral blood. Our data demonstrate that the HGF/SF/Met signaling system is essential not only during liver development but also for the regeneration of the organ in the adult.

Induction by staurosporine of hepatocyte growth factor production in human skin fibroblasts independent of protein kinase inhibition

Staurosporine is one of the most potent and well known inhibitors of protein kinases, and it is often used to study the involvement of protein kinases in signal transduction pathways. We now report that staurosporine can induce the production of hepatocyte growth factor (HGF) independently of protein kinase inhibition. Staurosporine markedly stimulated the production of HGF in various cell types, including human skin fibroblasts. Its effect was accompanied by up-regulation of HGF gene expression. The inhibition of protein kinases appears not to be involved in staurosporine-induced HGF production, because other protein kinase inhibitors, K-252a, H-7, GF 109203X and genistein, had no HGF-inducing activity. UCN-01, 7-hydroxystaurosporine, which differs from staurosporine only in its aglycone moiety, also showed HGF-inducing activity, and inactive K-252a differs from staurosporine only in its sugar moiety. These results indicate that the sugar moiety, a six-atom ring structure, is important in the HGF-inducing activity of staurosporine. Experiments were then carried out to determine whether the characteristics of staurosporine-induced HGF production have similarities to those of HGF production stimulated by other HGF inducers. The effect of staurosporine like that of 8-bromo-cAMP and that of cholera toxin was marked in human skin fibroblasts from all four different sources, whereas the effects of epidermal growth factor and phorbol 12-myristate 13-acetate were variable depending on cells. The net increase in HGF production induced by staurosporine was not reduced in protein kinase C-depleted human skin fibroblasts. Moreover, synergistic induction of HGF was detected between staurosporine and interferon-gamma as well as between 8-bromo-cAMP and interferon-gamma. Staurosporine, however, did not increase intracellular cAMP levels in human skin fibroblasts. These results indicate that staurosporine induced HGF in different cell types via a signaling pathway similar to the cAMP-mediated pathway without increasing cAMP levels.

Human adult chondrocytes express hepatocyte growth factor (HGF) isoforms but not HgF: potential implication of osteoblasts on the presence of HGF in cartilage

HGF is increased in human OA cartilage, possibly from Ob's. RT-PCR shows HGF isoforms are differently regulated between chondrocytes and Ob. A paracrine cross-talk between subchondral bone and cartilage may occur during OA. Recently, hepatocyte growth factor (HGF) has been identified by immunohistochemistry in cartilage and more particularly in the deep zone of human osteoarthritic (OA) cartilage. By investigating HGF expression in cartilage, we found that chondrocytes did not express HGF; however, they expressed the two truncated isoforms, namely HGF/NK1 and HGF/NK2. Because the only other cells localized near the deep zone are osteoblasts from the subchondral bone plate, we hypothesized that they were expressing HGF. Indeed, we found that HGF was synthesized by osteoblasts from the subchondral bone plate. Moreover, OA osteoblasts produced five times more HGF than normal osteoblasts and almost no HGF/NK1, unlike normal osteoblasts. Because prostaglandin E2 (PGE2) and pro-inflammatory cytokines such as interleukin (IL)-1 and IL-6 are involved in OA progression, we investigated whether these factors impact HGF produced by normal osteoblasts. PGE2 was the only factor tested that was able to stimulate HGF synthesis. However, the addition of NS398, a selective inhibitor of cyclo-oxygenase-2 (COX-2) had no effect on HGF produced by OA osteoblasts. HGF/NK2 had a moderate stimulating effect on HGF production by normal osteoblasts, whereas osteocalcin was not modulated by either HGF or HGF/NK2. When investigating signaling routes that might be implicated in OA osteoblast-produced HGF, we found that protein kinase A was at least partially involved. In summary, this study raises the hypothesis that the HGF found in articular cartilage is produced by osteoblasts, diffuses into the cartilage, and may be implicated in the OA process.

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Liver regeneration in heparin-binding EGF-like growth factor transgenic mice after partial hepatectomy

BACKGROUND & AIMS

Heparin-binding epidermal growth factor-like growth factor (HB-EGF), a member of the EGF family, is synthesized in the form of a membrane-anchored precursor (proHB-EGF), which subsequently is processed proteolytically to mature HB-EGF. This study describes the effects of HB-EGF on liver regeneration after 70% partial hepatectomy in proHB-EGF transgenic mice with liver-specific expression.

METHODS & RESULTS

No significant differences in liver/body weight ratios and in bromodeoxyuridine (BrdU)-labeling index (the ratios of BrdU-positive hepatocyte nuclei) were found between adult transgenic and wild-type mice. However, in regenerating liver after partial hepatectomy, transgenic mice had higher liver/body weight ratios than wild-type mice and at 120 hours reached a level equal to that before partial hepatectomy. The BrdU-labeling index was about 5 times higher in the livers of transgenic mice compared with the wild type (51.5% vs. 10.2%, respectively; P < 0.01) at 48 hours after partial hepatectomy. Activation of microtubule-associated protein kinase after partial hepatectomy was higher and earlier in the transgenic mice as compared with the wild-type mice. Soluble HB-EGF was increased in the liver (at 8 min) after partial hepatectomy, indicating that the shedding of proHB-EGF occurred after partial hepatectomy.

CONCLUSIONS

The transgenic expression of HB-EGF accelerates the proliferation of hepatocytes after partial hepatectomy, suggesting that HB-EGF functions as a hepatotrophic factor in vivo.

The role of cytokines in liver failure and regeneration: potential new molecular therapies

The liver is a unique organ, and first in line, the hepatocytes encounter the potential to proliferate during cell mass loss. This phenomenon is tightly controlled and resembles in some way the embryonal co-inhabitant cell lineage of the liver, the embryonic hematopoietic system. Interestingly, both the liver and hematopoietic cell proliferation and growth are controlled by various growth factors and cytokines. IL-6 and its signaling cascade inside the cells through STAT3 are both significantly important for liver regeneration as well as for hematopoietic cell proliferation. The process of liver regeneration is very complex and is dependent on the etiology and extent of liver damage and the genetic background. In this review we will initially describe the clinical relevant condition, portraying a number of available animal models with an emphasis on the relevance of each one to the human condition of fulminant hepatic failure (FHF). The discussion will then be focused on the role of cytokines in liver failure and regeneration, and suggest potential new therapeutic modalities for FHF. The recent findings on the role of IL-6 in liver regeneration and the activity of the designer IL-6/sIL-6R fusion protein, hyper-IL-6, in particular, suggest that this molecule could significantly enhance liver regeneration in humans, and as such could be a useful treatment for FHF in patients.

Acute liver CCl(4) intoxication causes low HSP70 gene expression and a delayed transition through the cell cycle in aged rats

Since there is still debate about the ability of the aged liver to regenerate, we compared some aspects of this response in young, adult and old rodents. 2, 6, 12 and 19-month-old rats were intraperitoneally injected with CCl(4) (3mg/kg) or left untreated (CT) and killed either 2h (group A) or 24h (group B) after intoxication. Liver injury was checked histologically and by assaying transaminases. mRNA levels of albumin (Alb), c-fos, c-myc, hepatocyte growth factor (HGF), transforming growth factor (TGF)-alpha and TGF-beta1 were also analyzed. Heat shock protein (HSP)70 gene expression was evaluated, and liver GSH content. Transaminases and histology show more damage in aged rats. Alb mRNA was reduced starting at 12 months in group A and at all ages in group B; c-fos and c-myc mRNAs reached the highest levels in 6-month-old rats and the lowest in those aged 12 and 19 months of group A. In group B, c-fos was detectable only in 6-month animals, but c-myc at all ages. HGF, TGF-alpha and TGF-beta1 mRNAs were up-regulated in treated rats, but to a lesser extent in the aged. HSP70 mRNA, absent in CT, was significantly increased at the age of 6 months, undetectable in the oldest rats in group A; in group B it was only visible in 6-month animals. GSH content was reduced with aging. In conclusion, during aging the liver regenerative machinery is preserved but its activation is reduced and delayed.

Hepatocyte growth factor promotes hepatocarcinogenesis through c-Met autocrine activation and enhanced angiogenesis in transgenic mice treated with diethylnitrosamine

Hepatocyte growth factor (HGF) is a mitogen for hepatocytes, but it is not clear whether HGF stimulates or inhibits hepatocarcinogenesis. We previously reported that HGF transgenic mice under the metallothionein gene promoter developed benign and malignant liver tumors spontaneously after 17 months of age. To elucidate the role of HGF in hepatocarcinogenesis, diethylnitrosamine (DEN) was administered to HGF transgenic mice. HGF overexpression accelerated DEN-induced hepatocarcinogenesis, often accompanied by abnormal blood vessel formation. In this study, 59% of transgenic males (versus 20% of wild-type males) and 39% of transgenic females (versus 2% of wild-type females) developed either benign or malignant liver tumors by 48 weeks (P<0.005, P<0.001, respectively). Moreover, 33% of males and 23% of female transgenic mice developed hepatocellular carcinoma (HCC), while none of the wild-type mice developed HCC (P<0.001, P<0.005, respectively). Enhanced kinase activity of the HGF receptor, Met, was detected in most of these tumors. Expression of vascular endothelial growth factor (VEGF) was up-regulated in parallel with HGF transgene expression. Taken together, our results suggest that HGF promotes hepatocarcinogenesis through the autocrine activation of the HGF-Met signaling pathway in association with stimulation of angiogenesis by HGF itself and/or indirectly through VEGF.

Synergy between truncated c-Met (cyto-Met) and c-Myc in liver oncogenesis: importance of TGF-beta signalling in the control of liver homeostasis and transformation

The c-Met tyrosine kinase receptor and its ligand, Hepatocyte Growth Factor/ Scatter Factor, have been implicated in human cancer. We have previously described that the transgenic expression of a truncated form of human c-Met (cyto-Met) in the liver confers resistance to several apoptotic stimuli. Here we show the impact of cyto-Met expression on liver proliferation and transformation. Despite a sixfold increase of hepatocyte proliferation, adult transgenic livers displayed normal size and architecture. We present evidence showing that activation of TGF-beta1 signalling controls the liver mass in cyto-Met mice. The oncogenic potential of cyto-Met was further assessed in the context of c-Myc-induced hepatocarcinogenesis, using WHV/c-Myc transgenic mice. Co-expression of cyto-Met and c-Myc further enhanced hepatocyte proliferation and caused a dramatic acceleration of the Myc-induced tumorigenesis, leading to the emergence of hepatocarcinomas in 3-4-month-old animals. Importantly, the TGF-beta receptor type II expression was strongly downregulated in most tumours, indicating that impairment of TGF-beta1-mediated growth inhibition plays a major role in accelerated neoplastic development. The strong potential of cyto-Met for oncogenic cooperation without direct transforming activity designates cyto-Met mice as an ideal tool for studying the early steps of multistage hepatocarcinogenesis and for identification of prognostic markers of transformation.

Delayed liver regeneration with negative regulation of hepatocyte growth factor and positive regulation of transforming growth factor-beta1 mRNA after portal branch ligation in biliary obstructed rats

BACKGROUND

The influence of obstructive jaundice on liver regeneration is still controversial. The aim of this study was to investigate liver regeneration after portal branch ligation (PBL) in the jaundiced rat, focusing on hepatocyte growth factor (HGF) and transforming growth factor-beta1 (TGF-beta 1).

METHODS

Male Wistar rats underwent PBL or a sham operation 7 days after a common bile duct ligation. Liver wet weight, proliferating cell nuclear antigen labeling, HGF and TGF-beta 1 mRNA expression, and immunohistochemical staining with alpha-smooth muscle actin antibody were studied.

RESULTS

The rate of liver regeneration in jaundiced liver was decreased as compared to a non-jaundiced liver. DNA synthesis in the jaundiced non-ligated lobe was significantly lower than in the non-jaundiced liver as was the peak level of HGF mRNA expression after PBL. In contrast, the level of TGF-beta 1 mRNA expression was higher in the jaundiced liver, and alpha-smooth muscle actin staining showed that hepatic stellate cells were gradually activated into myofibroblast-like cells.

CONCLUSIONS

Obstructive jaundice decreased the expression of HGF mRNA and increased the expression of TGF-beta 1 mRNA, resulting in delayed liver regeneration after PBL. We suggest that hepatic stellate cells activated in obstructive jaundice may affect the expression of these growth factors.

Hepatocyte growth factor and c-Met inhibition by hepatic cell hypoxia: a potential mechanism for liver regeneration failure in experimental cirrhosis

Hepatic resection in cirrhotic patients is associated with impaired liver regeneration and poor clinical outcome. Because experimental cirrhosis is associated with hepatic cell hypoxia, we herein investigated whether hypoxia might alter the mechanisms of liver regeneration in the cirrhotic liver. Cirrhosis was induced by diethylnitrosamine in rats. Immunohistochemistry was performed to assess hepatocellular hypoxia and proliferation 24 hours after a two-thirds partial hepatectomy (PH) in cirrhotic and control rats. Cultured hepatocytes and myofibroblastic hepatic stellate cells were submitted to hypoxia using anaerobic jars. Hepatocyte growth factor (HGF) and c-Met expressions were determined by reverse transcriptase-polymerase chain reaction, Northern blot, and Western blot. In control rats, hypoxia was restricted to perivenular hepatocytes, and PH induced a marked increase in hepatocyte proliferation and in liver HGF expression, whereas c-Met expression remained unchanged. In cirrhotic rats, hypoxia was detected virtually in all of the hepatocytes, and PH induced no significant change in hepatocyte proliferation and in liver HGF expression, whereas c-Met expression was decreased as compared to normal livers. In vitro, the expression of HGF in myofibroblastic hepatic stellate cells and of c-Met in hepatocytes underwent a dramatic decrease under hypoxia. Our results suggest that hepatocellular hypoxia causes inhibition of HGF (and of c-Met)-mediated proliferation and thereby might contribute to liver regeneration failure in cirrhotic liver.

Systemic administration of naked plasmid encoding hepatocyte growth factor ameliorates chronic renal fibrosis in mice

The progression of chronic renal diseases is considered as an irreversible process that eventually leads to end-stage renal failure characterized by extensive tissue fibrosis. At present, chronic renal fibrosis is incurable and the incidence of affected patients is on the rise worldwide. In this study, we demonstrate that delivery of hepatocyte growth factor (HGF) gene via systemic administration of naked plasmid vector markedly ameliorated renal fibrosis in an animal model of chronic renal disease induced by unilateral ureteral obstruction. A high level of exogenous HGF protein was detected in the obstructed kidneys following intravenous injection of naked plasmid encoding human HGF. Delivery of human HGF gene induced a sustained activation of extracellular signal-regulated kinases-1 and -2 in the obstructed kidneys. Exogenous HGF expression dramatically inhibited alpha-smooth muscle actin expression, attenuated renal interstitial accumulation and deposition of collagen I and fibronectin. In addition, exogenous HGF suppressed renal expression of pro-fibrogenic cytokine TGF-beta1 and its type I receptor in vivo. These results suggest that systemic administration of naked plasmid vector introduces a high level of exogenous HGF to the diseased kidneys, and that HGF gene transfer may provide a novel therapeutic strategy for amelioration of chronic renal fibrosis in vivo.

Hepatocyte growth factor: renotropic role and potential therapeutics for renal diseases

Hepatocyte growth factor (HGF), a ligand for the c-Met receptor tyrosine kinase, has mitogenic, motogenic, anti-apoptotic, and morphogenic (for example, induction of branching tubulogenesis) activities for renal tubular cells, while it has angiogenic and angioprotective actions for endothelial cells. Stromal cells such as mesangial cells, endothelial cells, and macrophages are sources of renal HGF; thus, HGF mediates epithelial-stromal and endothelial-mesangial interactions in the kidney. In response to acute renal injury, the expression of HGF increases in the injured kidney and in distant intact organs such as the lung and spleen. Locally and systemically increased HGF supports renal regeneration, possibly not only by enhancing cell growth but also by promoting morphogenesis of renal tissue. During progression of chronic renal failure/renal fibrosis, the expression of HGF decreases in a manner reciprocal to the increase in expression of transforming growth factor-beta (TGF-beta), a key player in tissue fibrosis. A decrease in endogenous HGF, as well as increase in TGF-beta, augments susceptibility to the onset of chronic renal failure/renal fibrosis. On the other hand, supplements of exogenous HGF have preventive and therapeutic effects in cases of acute and chronic renal failure/renal fibrosis in laboratory animals. HGF prevents epithelial cell death and enhances regeneration and remodeling of renal tissue with injury or fibrosis. A renotropic system underlies the vital potential of the kidney to regenerate, while an impaired renotropic system may confer susceptibility to the onset of renal diseases. Thus, HGF supplementation may be one therapeutic strategy to treat subjects with renal diseases, as it enhances the intrinsic ability of the kidney to regenerate.