Hepatocyte Growth Factor Transgenic Mice Research Articles

Impact of Neuron-Derived HGF on c-Met and KAI-1 in CNS Glial Cells: Implications for Multiple Sclerosis Pathology.

Demyelination and axonal degeneration are fundamental pathological characteristics of multiple sclerosis (MS), an inflammatory disease of the central nervous system (CNS). Although the molecular mechanisms driving these processes are not fully understood, hepatocyte growth factor (HGF) has emerged as a potential regulator of neuroinflammation and tissue protection in MS. Elevated HGF levels have been reported in MS patients receiving immunomodulatory therapy, indicating its relevance in disease modulation. This study investigated HGF's neuroprotective effects using transgenic mice that overexpressed HGF. The experimental autoimmune encephalomyelitis (EAE) model, which mimics MS pathology, was employed to assess demyelination and axonal damage in the CNS. HGF transgenic mice showed delayed EAE progression, with reduced CNS inflammation, decreased demyelination, and limited axonal degeneration. Scanning electron microscopy confirmed the preservation of myelin and axonal integrity in these mice. In addition, we explored HGF's effects using a cuprizone-induced demyelination model, which operates independently of the immune system. HGF transgenic mice exhibited significant protection against demyelination in this model as well. We also investigated the expression of key HGF receptors, particularly c-Met and KAI-1. While c-Met, which is associated with increased inflammation, was upregulated in EAE, its expression was significantly reduced in HGF transgenic mice, correlating with decreased neuroinflammation. Conversely, KAI-1, which has been linked to axonal protection and stability, showed enhanced expression in HGF transgenic mice, suggesting a protective mechanism against axonal degeneration. These findings underscore HGF's potential in preserving CNS structure and function, suggesting it may be a promising therapeutic target for MS, offering new hope for mitigating disease progression and enhancing neuroprotection.

SO023HEPATOCYTE GROWTH FACTOR (HGF) PRECLUDE HIGH-FAT DIET-INDUCED OBESITY AND IMPROVED INSULIN RESISTANCE IN MICE

Abstract Background and Aims Obesity and its associated chronic inflammation in adipose tissue initiate insulin resistance, which is related to several pathologies including hypertension and atherosclerosis. Previous reports demonstrated that circulating hepatocyte growth factor (HGF) level was associated with obesity and type 2 diabetes. However, its precise role in obesity and related-pathology is unclear. Method In this experiment, cardiac-specific over-expression of human HGF in mice (HGF-Tg mice) which showed 4-5 times higher serum HGF levels than wild-type mice were used. We chose cardiac specific HGF overexpression, as other strain of HGF transgenic mice such as liver and kidney specific HGF overexpression mice develop cancer and cystic diseases, which are rare in the heart. In the present study, using HGF-Tg mice and anti-HGF neutralizing antibody (HGF-Ab), we explored the role of HGF in obese and insulin resistance induced by high fat diet (HFD) for 14 weeks (200 or 400ug/week). Results With normal chow diet (ND), there were no significant changes in body weight between WT and HGF-Tg mice. While body weight in wild-type mice fed with HFD for 14 weeks was significantly increased accompanied with insulin resistance, HGF-Tg mice prevented body weight gain and insulin resistance. Insulin resistance in obesity arises from the combination of altered functions of insulin target cells (e.g., liver, skeletal muscle, and adipose tissue) and the accumulation of macrophages that secrete pro-inflammatory mediators in adipose tissue. The accumulation of macrophages and elevated levels of inflammatory mediators in adipose tissue were significantly inhibited in HGF-Tg mice as compared to wild-type mice. In the gWAT, the mRNA levels of the mature macrophage marker F4/80, the chemoattractants, MCP-1 and CXCL2, and the inflammatory cytokines, such as TNF-α and iNOS, were significantly increased in WT mice fed with HFD. However, these levels were markedly reduced in HGF-Tg mice fed with HFD. Additionally, activation of Akt by insulin administration was significantly reduced in the gWAT SM, and liver by HFD; however, this activation was restored in HGF-Tg mice. Moreover, insulin-induced Akt signaling was decreased in HGF-Ab groups as compared to saline group under HFD condition. Importantly, HFD significantly increased the level of HGF mRNA by approximately 2 fold in gWAT, SM, and liver without changing cMet expression. All together, these data indicate that the HGF as one of the systemic gWAT, SM, and liver-derived growth factor plays a role in compensatory mechanism against insulin-resistance through the at least anti-inflammatory effect in adipose tissue. The HFD-induced obesity in wild-type mice treated with HGF-neutralizing antibody showed an exacerbated response to the glucose tolerance test. Conclusion HGF suppresses inflammation in adipose tissue induced by a high-fat diet, and as a result improves systemic insulin resistance. These gain-of-function and loss-of-function studies demonstrated that the elevated HGF level induced by HFD have protective role against obesity and insulin resistance.

Abstract 392: Combined targeting of MET and PI3K improves efficacy in breast cancer models with concurrent MET/PI3K aberrations

Abstract Introduction: Detailed understanding of the genetic abnormalities that drive subsets of cancer has led to the development of highly specific inhibitors targeting key oncogenic pathways. Growing evidence implicates aberrations of both mesenchymal epithelial transition receptor (MET) and its key downstream phosphatidylinositol 3-kinase (PI3K) signaling with poorer prognosis in breast cancer. Co-targeting MET/PI3K and identifying mechanisms of response and resistance could ultimately inform a novel therapeutic strategy for breast cancer treatment. Based on these finding, we hypothesized that concurrent aberrations in PI3K and MET will render breast cancers resistant to therapies targeting each pathway, and that combination therapy targeting the PI3K and MET pathway will improve the efficacy by preventing the acquisition of resistance. Methods: We established cell models that stably express human wild type (WT) MET or MET-T1010I, a functional germline single nucleotide polymorphism, or mutant PI3K-H1047R alone, or variable concurrent aberrations in PI3K and MET using MCF-10A, a non-transformed mammary epithelial cell line, and HCC1954, a breast cancer cell line with an endogenous PI3KCA-H1047R mutation. Cell behaviors, including survival, invasion and response to MET one arm monoclonal antibody onartuzumab (MetMAb, Genentech Inc) and/or pan class I PI3K inhibitor GDC 941 (pictilisib, Genentech Inc), were detected. HCC1954 expressing WT MET or MET-T1010I along with PI3K-H1047R were transplanted into the mammary fat pad of hepatocyte growth factor-transgenic mice on a severe combined immunodeficiency background. Statistical analyses were carried out using the ANOVA and the Student t test. Result: Expression WT MET or MET-T1010I act coordinately with PI3K-H1047R to increase colony formation (P < 0.01, respectively). Concurrent MET-T1010I, but not WT MET, acts coordinately with PI3K-H1047R to increase cell invasion (P < 0.0001). Expression MET-T1010I or WT MET induced cells resistance to GDC941, with MET-T1010I stronger than WT MET. Combined targeting MET with onartuzumab and targeting PI3K with GDC941 significantly inhibited cell growth in matrigel, dose dependently than each monotherapy (P < 0.0001, respectively). Invasion assay showed similar pattern. Combined onartuzumab and GDC941 significantly inhibited invasion, dose dependently (P < 0.001). The effects were confirmed using PI3K/mTOR inhibitor, GDC980. Consistently, combination of onartuzumab/GDC941 significantly inhibited tumor growth (P < 0.01 versus GDC941; P < 0.0001 versus onartuzumab alone). Conclusions: Concurrent aberrations of MET and PI3K render breast cancer cells resistant to therapies blocking either pathway. Targeting both MET and PI3K increases inhibitory efficacy. Citation Format: Shuying Liu, Naoto T. Ueno, Bailiang Wang, Mihai Gagea, Prahlad T. Ram, Mark Merchant, John Mendelsohn, Debasish Tripathy, Gordon B. Mills, Ana M. Gonzalez-Angulo. Combined targeting of MET and PI3K improves efficacy in breast cancer models with concurrent MET/PI3K aberrations. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 392.

Anti-inflammatory effects of hepatocyte growth factor on the vicious cycle of macrophages and adipocytes

The paracrine loop involving inflammatory cytokines between adipocytes and macrophages establishes a vicious cycle that aggravates pro-inflammatory changes in adipose tissue. The serum level of hepatocyte growth factor (HGF) is increased in metabolic syndrome, but whether HGF is beneficial or detrimental in inflammatory conditions is unclear. We previously reported that HGF has strong anti-inflammatory effects. We therefore hypothesized that HGF may inhibit chronic inflammation in adipose tissue by inhibiting the vicious cycle between adipocytes and macrophages. We stimulated the macrophage cell line RAW264 with HGF and evaluated pro-inflammatory cytokines. Coculturing differentiated 3T3-L1 adipocytes with RAW264 results in marked upregulation of pro-inflammatory cytokines. We examined whether HGF suppresses the upregulation of pro-inflammatory cytokines in this coculture system. Cardiac-specific HGF transgenic mice (HGF-Tg) were crossed with ApoE KO (knockout) mice, to yield ApoE KO/HGF-Tg mice, which were treated with a high-fat diet (HFD) and received angiotensin (Ang) II. The phenotypes of ApoE KO and ApoE KO/HGF-Tg mice were compared. Treatment with HGF reduced the expression of pro-inflammatory cytokine genes (Tumor necrosis factor-α, monocyte chemoattractant protein-1 and interleukin-6) in RAW264 and the coculture system. The anti-inflammatory effects of HGF were also confirmed in in vivo studies. Macrophage infiltration in epididymal adipose and fatty liver was reduced in ApoE KO/HGF-Tg. Adipocyte diameter was reduced in ApoE KO/HGF-Tg, and the serum adiponectin level was upregulated. These beneficial effects in ApoE KO/HGF-Tg mice under HFD and Ang II infusion were abrogated by an anti-HGF neutralizing antibody. These results suggest that HGF inhibits the vicious cycle of adipocytes and macrophages through the inhibition of macrophage-mediated pro-inflammatory cytokines and upregulation of adiponectin in adipocytes. These favorable effects may suppress chronic inflammation in adipose tissue.

Abstract 4085: Experimental metastasis by the prostate adenocarcinoma-derived cell line PC3M is driven by partial activation of the human Met pathway.

Abstract Interspecies cross-reactivity is an important consideration when interpreting the results of tissue xenograft studies. For many paracrine signaling pathways, murine growth factors may not activate their orthologous human receptors in tumor xenografts, thereby failing to recapitulate a potentially relevant human condition in the mouse model. Unrecognized or poorly defined species-specific differences of this type can seriously hinder basic research progress as well as the development of therapeutic or diagnostic agents. For example, the contributions of both tumor- and stromal-cell derived vascular endothelial growth factor (VEGF)-A to the vascularization of human tumor xenografts in immunodeficient mice prevented the direct comparison of anti-VEGF antibodies with different abilities to block host VEGF, and led to the production of mice expressing humanized VEGF with biological activity comparable to both human and mouse VEGF-A. Hepatocyte growth factor (HGF) and its receptor, Met, are also highly sought targets in cancer drug and diagnostic development. HGF/Met signaling drives tumor cell growth and motility, tumor invasiveness and metastasis. However, the failure of murine HGF to stimulate the growth of human tumor xenografts has restricted preclinical drug studies to a handful of human tumor cell lines that possess autocrine pathway activation or other more rare Met activation mechanisms, and ultimately forced the costly development of human HGF transgenic and knock-in mice so that preclinical studies could begin to encompass the known breadth of the pathway's involvement across human cancers. We report here that despite the failure of murine HGF to drive human tumor xenograft growth, mouse HGF potently stimulates human Met autophosphorylation, increased cell motility and matrix invasion, but not proliferation. As a result, the growth of xenografted PC3M human prostate adenocarcinoma cells as primary tumors in mice was not inhibited by a selective HGF antagonist, but spontaneous tumor metastasis was completely blocked. These results improve our understanding of the cross-reactivity between human and murine HGF/Met signaling pathways and suggest that the preclinical evaluation of agents for their ability to block HGF-driven tumor metastasis may incorporate cell lines expressing human Met but not HGF, i.e. a wide variety of human carcinoma-derived cell lines, without the need for using mice engineered to express human HGF. Citation Format: Fabiola Cecchi, Chih-Jian Lih, Young H. Lee, William D. Walsh, Michael P. Williams, Donald P. Bottaro. Experimental metastasis by the prostate adenocarcinoma-derived cell line PC3M is driven by partial activation of the human Met pathway. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4085. doi:10.1158/1538-7445.AM2013-4085

Hepatocyte Growth Factor Inhibits Lipopolysaccharide-Induced Oxidative Stress via Epithelial Growth Factor Receptor Degradation

Lipopolysaccharide (LPS) triggers sepsis and systemic inflammatory response syndrome, which results in multiple organ failure. Our recent reports demonstrated that hepatocyte growth factor (HGF) attenuated angiotensin II-induced oxidative stress via epithelial growth factor receptor (EGFR) degradation in vascular smooth muscle cells. Here, we examined whether HGF can protect against systemic inflammatory response syndrome induced by LPS and investigated the mechanism. HGF inhibited the increase in the expression of vascular cell adhesion molecule-1 and EGFR by LPS in vitro. HGF inhibited colocalization of EGFR and Src homology domain 2-containing inositol 5'-phosphatase 2. Furthermore, HGF inhibited reactive oxygen species production. We also injected LPS into HGF transgenic mice with increased HGF serum concentration and their littermates. HGF transgenic mice reduced LPS-induced vascular cell adhesion molecule-1 and reactive oxygen species compared with control, accompanied by significant EGFR degradation. Furthermore, HGF transgenic mice significantly improved survival in the LPS injection model. The present study revealed inhibition of LPS-induced vascular cell adhesion molecule-1 expression by HGF via the degradation of EGFR. We demonstrated that HGF regulated Src homology domain 2-containing inositol 5'-phosphatase 2 recruitment to EGFR and inhibited LPS-induced inflammation via EGFR degradation. This effect of HGF may be useful for the treatment of inflammatory disease.

Hepatocyte growth factor attenuates renal fibrosis through TGF-β1 suppression by apoptosis of myofibroblasts

The progression of chronic kidney disease (CKD) is characterized by the persistent accumulation of extracellular matrix. Especially, α-SMA-positive myofibroblasts producing large amounts of TGF-β1 are considered to play a key role in interstitial fibrosis. Although hepatocyte growth factor (HGF) improved renal fibrosis in various models, the molecular mechanisms involved are not yet fully understood. In this study, the molecular mechanisms of the inhibition of fibrosis by HGF was examined using HGF transgenic mice (HGF-Tg) with angiotensin II (Ang II) infusion in 4 weeks models. HGF-Tg mice showed significantly decreased Ang II-induced renal fibrosis and lesser numbers of interstitial myofibroblasts, whereas the antifibrotic effect of HGF was abrogated using HGF-neutralizing antibody. The antifibrotic action in HGF-Tg mice was concordant with a decrease in TGF- β1, collagen type I and IV mRNA expression and an increase in MMP-2 and MMP-9 expression. Furthermore, HGF-Tg mice treated with Ang II showed apoptosis of myofibroblasts. To further investigate the antifibrotic effect of HGF, cultured human mesangial cells were used. HGF induced apoptosis of myofibroblast. Inhibition of the FAK-ERK-MMP signaling cascade by specific inhibitor or siRNA significantly decreased HGF-induced myofibroblast apoptosis. The present study demonstrates that the increase in metalloproteinases through FAK-ERK signaling by HGF promotes myofibroblast apoptosis. Activation of metalloproteinases by HGF in the fibrotic kidney might be considered to attenuate the progression of CKD.

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

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. 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. 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. 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.

Novel Proapoptotic Effect of Hepatocyte Growth Factor: Synergy with Palmitate to Cause Pancreatic β-Cell Apoptosis

Increasing evidence suggests that elevation of plasma fatty acids that often accompanies insulin resistance contributes to beta-cell insufficiency in obesity-related type 2 diabetes. Circulating levels of hepatocyte growth factor (HGF) are increased in humans with metabolic syndrome and obesity. HGF is known to protect beta-cells against streptozotocin and during islet engraftment. However, whether HGF is a beta-cell prosurvival factor in situations of excessive lipid supply has not been deciphered. Mice overexpressing HGF in the beta-cell [rat insulin type II promoter (RIP)-HGF transgenic mice] fed with standard chow display improved glucose homeostasis and increased beta-cell mass and proliferation compared with normal littermates. However, after 15 wk of high-fat feeding, glucose homeostasis and beta-cell expansion and proliferation are indistinguishable between normal and transgenic mice. Interestingly, RIP-HGF transgenic mouse beta-cells and normal beta-cells treated with HGF display increased sensitivity to palmitate-mediated apoptosis in vitro. Palmitate completely eliminates Akt and Bad phosphorylation in RIP-HGF transgenic mouse islets. HGF-overexpressing islets also show significantly decreased AMP-activated protein kinase-alpha and acetyl-coenzyme A carboxylase phosphorylation, diminished fatty acid oxidation, increased serine palmitoyltransferase expression, and enhanced ceramide formation compared with normal islets. Importantly, human islets overexpressing HGF also display increased beta-cell apoptosis in the presence of palmitate. Treatment of both mouse and human islet cells with the de novo ceramide synthesis inhibitors myriocin and fumonisin B1 abrogates beta-cell apoptosis induced by HGF and palmitate. Collectively, these studies indicate that HGF can be detrimental for beta-cell survival in an environment with excessive fatty acid supply.

Hepatocyte Growth Factor, but not Vascular Endothelial Growth Factor, Attenuates Angiotensin II–Induced Endothelial Progenitor Cell Senescence

Although both hepatocyte growth factor (HGF) and vascular endothelial growth factor (VEGF) are potent angiogenic growth factors in animal models of ischemia, their characteristics are not the same in animal experiments and clinical trials. To elucidate the discrepancy between HGF and VEGF, we compared the effects of HGF and VEGF on endothelial progenitor cells under angiotensin II stimulation, which is a well-known risk factor for atherosclerosis. Here, we demonstrated that HGF, but not VEGF, attenuated angiotensin II-induced senescence of endothelial progenitor cells through a reduction of oxidative stress by inhibition of the phosphatidylinositol-3,4,5-triphosphate/rac1 pathway. Potent induction of neovascularization of endothelial progenitor cells by HGF, but not VEGF, under angiotensin II was also confirmed by in vivo experiments using several models, including HGF transgenic mice.

HGF ameliorates a high-fat diet-induced fatty liver

Hepatocyte growth factor (HGF) has various effects especially on epithelial cells. However, the precise role of HGF on lipogenesis is still not fully understood. A high-fat diet was administered to HGF transgenic mice and wild-type control mice in vivo. Furthermore, recombinant human HGF (rhHGF) was administered to HepG2 cell line in vitro. We performed an analysis regarding the factors relating to lipid metabolism. An overexpression of HGF dramatically ameliorates a high-fat diet-induced fatty liver. HGF transgenic mice showed an apparently reduced lipid accumulation in the liver. The activation of microsomal triglyceride transfer protein (MTP) and apolipoprotein B (ApoB) accompanying higher triglyceride levels in the serum were found in HGF transgenic mice on a normal diet. Interestingly, this upregulation of the MTP activation became more apparent in the high-fat diet. In addition, the administration of rhHGF stimulated MTP and ApoB expression while reducing reduced the intracellular lipid content in HepG2 cell line. However, this induction of MTP and ApoB by HGF was clearly inhibited by PD98059 (MAPK inhibitor). In conclusion, the data presented in this study indicated that HGF ameliorates a high-fat diet-induced fatty liver via the activation of MTP and ApoB.

Gene expression profiles of drug‐metabolizing enzymes and transporters with an overexpression of hepatocyte growth factor

It is important to elucidate the precise mechanism of drug metabolism during hepatic regeneration. Although cytochromes P450 (CYPs) are well known to be down-regulated in growth-stimulated cells, the overall gene expression profile of drug metabolizing enzymes are still not fully understood during hepatic regeneration. In this study, we investigated the gene expression profiles of such enzymes with an overexpression of hepatocyte growth factor (HGF). Gene expression profiles were obtained using the Affymetrix MOE430A GeneChip oligonucleotide microarray by comparing HGF transgenic mice and wild-type mice. HGF produced a general decrease in mice with the expression of CYP isoforms such as Cyp1a2, Cyp2b10, Cyp2c, Cyp2d9, Cyp3a11, Cyp4a10, and Cyp7a1. Some isoforms of alcohol dehydrogenase, aldehyde dehydrogenase, and carboxylesterase also decreased. In the phase II enzymes, some isoforms of glutathione S-transferase and UDP-glucuronosyl transferase showed a reduced expression, although the sulfotransferase did not. In phase III transporters, some organic anion transporter and organic cation transporters were down-regulated. Among the nuclear receptors that are known to regulate the drug-metabolizing enzymes, small heterodimer partner and constitutive androstane receptor were down-regulated with an HGF overexpression. The protein level and enzymatic activity of Cyp2c decreased with an HGF overexpression. We furthermore investigated the inducibility of Cyp2b10 with xenobiotic inducers. Although the basal expression of Cyp2b10 was repressed, the inducibility was not abolished with the HGF overexpression. HGF down-regulated not only CYPs but also some drug-metabolizing enzymes, transporters, and nuclear receptors. We thus have to take in our mind the low basal expression of drug metabolizing enzymes, when treating patients with a regenerative liver state.

Contribution of HGF to Liver Regeneration by Strong Mobilization of Bone Marrow Stem Cells.

Cell plasticity of bone marrow stem cells to hepatocytes is known, however, the details are still unclear. hepatocyte growth factor (HGF) promotes an increase in liver stem cells in severely injured liver, but intervention to bone marrow stem cell is unclear. We examined a role of HGF in bone marrow stem cell-mediated liver regeneration in order to obtain effective liver regeneration.First, we found that the phenotype of stem cells, which can differentiate into hepatocytes, is Lin−c-kit+Sca-1+CD34− in bone marrow or Lin−c-kit+Sca−1+CD34+ in peripheral blood mobilized by G-CSF. We transplanted single Lin−c-kit+Sca-1+CD34− bone marrow cell harvested from male EGFP mouse to female wild type mouse, and then, using this GFP-chimera-mouse, we found that bone marrow origin GFP+ and Y chromosome+ hepatic cells were present in liver after acute liver damage. Next, single Lin−c-kit+Sca-1+CD34+ peripheral blood cell, which was mobilized in peripheral blood by administration of G-CSF, was transplanted into the portal vein of the wild type mouse which was given hepatic damage. We found that the GFP-positive cells also expressed albumin.Second, we investigated whether the HGF can mobilize stem cells from bone marrow to peripheral blood. In peripheral blood of HGF transgenic mice, 1.1% developed CD34+ cells and 20±3 colony forming cells of 1X106 peripheral blood mononuclear cells were shown. Colony forming cells were found in the mouse into which an HGF-expressing adenovirus was administered. After injection of rHGF to mice, a significant time-dependent increase of percentage of CD34+ cells in the PB was noted at the first 3 hours and CD34+ cells were increased in dose-dependent manner of rHGF and reached plateau level at 100 m/kg. The mice having transplantation with PB cells from 100 mg HGF-treated mice for 4days showed engraftment 2 months after transplantation. Upon activation of rHGF in mouse MS-5 stromal cells, phosphorylation c-Met and SCF were up-regulated, while VCAM -1, MMP-9, SDF -1 or CXCR4 were not changed. SCF level in conditioned media was also increased after the HGF stimulation.Finally, we examined whether the bone marrow stem cells in PB mobilized by HGF transdifferentiate into hepatocytes. Using GFP-chimera-mice given acute liver injury after administration of retorolusine and CCl4, the levels of GFP+ cells in liver of GFP-chimera-mice 2 months after treatment by PBS and HGF were 2.2±1.4% and 12.7±3.6%, respectively (p<0.01). In conclusion, HGF can mobilize stem cells with long-term engraftment capabilities from bone marrow to peripheral blood, resulting in contribution to liver regeneration.

Transgenic mice overexpressing hepatocyte growth factor in the airways show increased susceptibility to lung cancer

Several studies have suggested a possible role of the hepatocyte growth factor (HGF)/c-Met system in lung tumor development and progression. Extent of expression of both HGF and c-Met have been shown to be negative prognostic indicators of survival and recurrence in non-small-cell lung cancer, especially adenocarcinoma. To further define a role for HGF in lung cancer development and growth, we have generated transgenic mice that overexpress HGF in the airway epithelium. HGF transgenic and wild-type mice were exposed to the tobacco carcinogen, nitrosamine 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK), or saline control and killed 10-38 weeks after exposure. Lungs were formalin inflated, paraffin embedded and sectioned. It was verified that the HGF transgene was expressed only in the lungs of transgenic mice. The transgenic mouse lung histology exhibited congestion in the alveolar spaces, excess production of blood vessels and a convoluted pattern of airways with wide bifurcations. The number of lung tumors from NNK-treated transgenic animals versus the number of lung tumors from NNK-treated wild-type animals was significantly higher (P = 0.0001, Poisson regression). The percentage of animals with tumors was 75% in the transgenic group compared with 48.8% in the wild-type group. The main effect was an increase in tumor multiplicity; average size of tumors was not different between the groups. Additionally, the tumors that arose in the transgenic mice contained increased HGF protein compared with tumors from the wild-type mice. These results indicate that lung carcinogenesis induced by a tobacco carcinogen is enhanced by expression of the HGF transgene. This model recapitulates the phenotype of aggressive lung adenocarcinoma that overexpresses HGF and will be useful in evaluating antitumor agents that target either the HGF/c-Met pathway or downstream effects such as angiogenesis or invasion.

HGF as a Strong Mobilizer of Hematopoietic Stem Cells to Peripheral Blood.

How hematopoietic stem cells (HSC) in bone marrow (BM) contribute to liver regeneration remains to be resolved. The mechanisms which mobilize HSC from BM to peripheral blood (PB) and govern their homing to the liver are unknown. Hepatocyte growth factor (HGF) is locally and generally increased following liver injury, suggesting that it promotes proliferation, adhesion, and survival of hepatocytes. PB stem cells mobilized by cytokines are widely used for clinical transplantation. However, it is not known if HGF can mobilize HSC to PB or if it has the capability to differentiate HSC into hepatocytes. In this study we examined whether HGF can mobilize HSC from BM to PB using the murine stem cell transplantation model.First, we found that HGF transgenic mice, which have high serum levels of HGF concentration, had many colony-forming cells in PB, suggesting HGF increases circulation of HSC and progenitor cells. After determining through RT-PCR analysis that lineage (Lin) − BM cells express the tyrosine kinase receptor c-MET, we speculated that the c-MET-HGF axis modulates the recruitment of HSC from BM to PB. We also examined the effects of exogenous HGF in mobilizing stem cells from BM to PB. To determine whether HGF can mobilize HSC to PB, we investigated the expression of CD34 using flow cytometric analysis. The CD34+ cells in PB mobilized by HGF increased in a dose-dependent pattern and reached a plateau at 0.1mg/kg of recombinant HGF administration. Significant increases in CD34+ cells in PB were noted at 3h after HGF infusion. The continual administration of HGF every 24h increased the CD34+ cells in PB to maximum levels at 4 days. Finally, the absolute number of CD34+ cells in PB after HGF administration was as much as the number of those cells after administration at 12-hour intervals subcutaneously with 0.125mg/kg of recombinant human granulocyte-colony stimulating factor (G-CSF) for 4 consecutive days. To investigate engraftment of the mobilized cells to BM, 0.1mg/kg HGF was injected into Ly-5.1 mice every 24h for 4 days. Lin− cells in PB were collected 3h after the last injection of HGF and then injected into lethally-irradiated Ly-5.2 C57BL/6 mice. Two months after transplantation, the level of engraftment was assessed by analysis of donor (Ly-5.1) cells in the nucleated cells of the PB of recipient mice. The mean percentage of donor cells of mice transplanted with Lin− cells from HGF-treated mice was 1.8%, whereas that of the mice transplanted with untreated PB cells was 0%. Multilineage engraftment was confirmed by the presence of the Thy-1+ cells, B220+ cells, and Mac-1/Gr-1+ cells. When we tested the CD34 expression of the stem cells transplanted, the majority of the cells expressed CD34. Then we tracked single Lin−, Sca-1+, c-kit+, CD34+ PB cells from G-CSF-treated transgenic-enhanced green fluorescent protein (EGFP) mice that were injected into spleen of the CCl4-induced liver-injured B6 mice along with 500 Lin−, Sca-1+, c-kit+, CD34+ PB cells from G-CSF-treated normal B6 mice. Two months later, donor-derived GFP+ cells were identified among recipient hepatocytes in liver-injured mice using immunohistochemistry for GFP.These findings demonstrate that stem cells with long-term engraftment capabilities can be mobilized by HGF, and that HSC in PB mobilized by HGF are capable of differentiating into hepatocytes, suggesting HGF contributes to liver regeneration partly by mobilizing HSC to PB.

Transgene-derived hepatocyte growth factor attenuates reactive renal fibrosis in aristolochic acid nephrotoxicity.

Hepatocyte growth factor (HGF) has been demonstrated to attenuate acute tubular necrosis and interstitial fibrosis in a variety of rodent models of kidney disease. We investigated how HGF could affect chronic toxic nephropathy/interstitial fibrosis caused by aristolochic acid (AA). Wild-type and HGF transgenic mice received daily intraperitoneal injections of AA for 14 days. At sacrifice, kidneys were removed and used for microscopy examination and in vitro studies. To determine the molecular mechanisms of anti-fibrotic effects of HGF, cultured murine tubular epithelial cells (mProx24) were employed. Significant tubular degeneration was observed in both the transgenic and the wild-type mice to the same degree after 2 weeks treatment with AA. Interstitial fibrosis subsequently developed in the wild-type mice 4 weeks after cessation of AA administration. However, the transgenic mice manifested less fibrotic changes. Decreased expression of tissue inhibitor of metalloproteinase-1 (TIMP-1) and increased matrix metalloproteinase-9 activity could partially account for the attenuation of fibrogenesis in the transgenic mouse kidney. HGF at 10 and 100 ng/ml could block TIMP-1 gene expression in mProx24 induced by epidermal growth factor, but a decrease in the number of mProx24 via apoptosis induced by AA was blocked only by HGF at 100 ng/ml. Circulating transgene-derived HGF (2-10 ng/ml) could not prevent tubular degeneration caused by AA, but attenuated interstitial fibrogenesis during tubular regeneration. These findings suggest a possible therapeutic efficacy for renal interstitial fibrosis following tubular degeneration even of low-dose HGF.

Hepatocyte growth factor in osteoarthritis: when bone and cartilage decide to have a chat

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 express the two truncated isoforms, namely HGF/NK1 and HGF/NK2. As 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. Because prostaglandin E2 and proinflammatorycytokines such as IL-1 and IL-6 were involved in OA progression, we investigated whether these factors impact HGF produced by normal osteoblasts. Prostaglandin E2 was the only factor able to stimulateHGF synthesis. However, the addition of NS398, a selective inhibitor of cyclooxygenase-2, had no effect on HGF produced by OA osteoblasts. When investigating signaling routes that might be implicated in OA osteoblast-produced HGF, we found that protein kinase A and protein kinase C were 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 progression of OA. Furthermore, we investigated joints in HGF transgenic mice. We found that the subchondral bone was remodeled and that cartilage matrix was qualitatively different from the control mice. These results reinforced the idea of a role played by HGF in the joint.

CCl4-induced acute liver injury in mice is inhibited by hepatocyte growth factor overexpression but stimulated by NK2 overexpression

Hepatocyte growth factor (HGF) inhibits acute liver injury. NK2 acts as an antagonist to HGF in vitro, but its in vivo function has reached no consensus conclusions. We have investigated in vivo effects of HGF and NK2 on CCl4-induced acute liver injury. Elevation of the serum alanine aminotransferase level and extension of centrilobular necrosis were inhibited in HGF transgenic mice but were promoted in NK2 transgenic mice. Hepatocyte proliferation after liver injury was not inhibited in NK2 transgenic mice. Thus, this study indicates that HGF inhibits liver injury, and NK2 antagonizes HGF on liver injury, however, NK2 may not antagonize HGF on hepatocyte proliferation.

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.

Review: ligands for receptor tyrosine kinases expressed in the skin as environmental factors for melanocyte development.

Skin is the major tissue where melanocytes develop, and skin keratinocytes provide the necessary micro-environment for melanocyte survival, proliferation, differentiation, and migration. In this paper, we will discuss the ligands for receptor tyrosine kinases produced as environmental cues to support melanocyte development in the skin.