Hepatocyte growth factor triggers signaling cascades mediating vascular smooth muscle cell migration

Therapeutic Angiogenesis by a "Dynamic Duo": Simultaneous Expression of HGF and VEGF165 by Novel Bicistronic Plasmid Restores Blood Flow in Ischemic Skeletal Muscle

Therapeutic angiogenesis is a promising strategy for relief of ischemic conditions, and gene delivery was used to stimulate blood vessels’ formation and growth. We have previously shown that intramuscular injection of a mixture containing plasmids encoding vascular endothelial growth factor (VEGF)165 and hepatocyte growth factor (HGF) leads to restoration of blood flow in mouse ischemic limb, and efficacy of combined delivery was superior to each plasmid administered alone. In this work, we evaluated different approaches for co-expression of HGF and VEGF165 genes in a panel of candidate plasmid DNAs (pDNAs) with internal ribosome entry sites (IRESs), a bidirectional promoter or two independent promoters for each gene of interest. Studies in HEK293T culture showed that all plasmids provided synthesis of HGF and VEGF165 proteins and stimulated capillary formation by human umbilical vein endothelial cells (HUVEC), indicating the biological potency of expressed factors. Tests in skeletal muscle explants showed a dramatic difference and most plasmids failed to express HGF and VEGF165 in a significant quantity. However, a bicistronic plasmid with two independent promoters (cytomegalovirus (CMV) for HGF and chicken b-actin (CAG) for VEGF165) provided expression of both grow factors in skeletal muscle at an equimolar ratio. Efficacy tests of bicistronic plasmid were performed in a mouse model of hind limb ischemia. Intramuscular administration of plasmid induced significant restoration of perfusion compared to an empty vector and saline. These findings were supported by increased CD31+ capillary density in animals that received pHGF/VEGF. Overall, our study reports a first-in-class candidate gene therapy drug to deliver two pivotal angiogenic growth factors (HGF and VEGF165) with properties that provide basis for future development of treatment for an unmet medical need—peripheral artery disease and associated limb ischemia.

The Function of the HGF/c-Met Axis in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignancies worldwide, leading to a large global cancer burden. Hepatocyte growth factor (HGF) and its high-affinity receptor, mesenchymal epithelial transition factor (c-Met), are closely related to the onset, progression, and metastasis of multiple tumors. The HGF/c-Met axis is involved in cell proliferation, movement, differentiation, invasion, angiogenesis, and apoptosis by activating multiple downstream signaling pathways. In this review, we focus on the function of the HGF/c-Met axis in HCC. The HGF/c-Met axis promotes the onset, proliferation, invasion, and metastasis of HCC. Moreover, it can serve as a biomarker for diagnosis and prognosis, as well as a therapeutic target for HCC. In addition, it is closely related to drug resistance during HCC treatment.

Achillea asiatica extract and its active compounds induce cutaneous wound healing

ETHNOPHARMACOLOGICAL RELEVANCE

Achillea asiatica Serg. is a perennial herb belonging to the Asteraceae family that has long been traditionally used to treat acute intestinal and stomach inflammation, persistent fever, ulcers, wounds, and rheumatism.

AIM OF THE STUDY

We investigated the effect of A. asiatica extract (AAE) on cutaneous wound healing.

MATERIALS AND METHODS

To assess the effect of AAE on wounds, an incisional Sprague-Dawley (SD) rat model was topically treated with AAE for 2 weeks. HaCaT keratinocytes, Hs68 dermal fibroblasts, and RAW 264.7 macrophages were used for in vitro experiments. After treatment with AAE, cell viability, cell migration, and production of nitric oxide (NO) and prostaglandin E₂ (PGE₂) were investigated. mRNA expression of collagen type I and III and inflammatory cytokines was measured by RT-PCR. The effect of AAE on activation of β-catenin and other markers was determined by Western blot analysis.

RESULTS

AAE treatment significantly increased epithelialization and accelerated wound healing in SD rats. Meanwhile, AAE and its active compounds reduced NO and PGE₂ release and mRNA expression of inflammatory cytokines in RAW 264.7 macrophages, reflecting anti-inflammatory activity. Furthermore, AAE and its constituents stimulated collagen expression in Hs68 fibroblasts by activating transforming growth factor-β and stimulated keratinocyte differentiation and motility by inducing β-catenin, Akt, and keratinocyte differentiation markers.

CONCLUSIONS

AAE improves skin wounds in SD rats and supports keratinocyte development.

Gene expression profiles and signaling mechanisms in α2B-adrenoceptor-evoked proliferation of vascular smooth muscle cells

BACKGROUND

α2-adrenoceptors are important regulators of vascular tone and blood pressure. Regulation of cell proliferation is a less well investigated consequence of α2-adrenoceptor activation. We have previously shown that α2B-adrenoceptor activation stimulates proliferation of vascular smooth muscle cells (VSMCs). This may be important for blood vessel development and plasticity and for the pathology and therapeutics of cardiovascular disorders. The underlying cellular mechanisms have remained mostly unknown. This study explored pathways of regulation of gene expression and intracellular signaling related to α2B-adrenoceptor-evoked VSMC proliferation.

RESULTS

The cellular mechanisms and signaling pathways of α2B-adrenoceptor-evoked proliferation of VSMCs are complex and include redundancy. Functional enrichment analysis and pathway analysis identified differentially expressed genes associated with α2B-adrenoceptor-regulated VSMC proliferation. They included the upregulated genes Egr1, F3, Ptgs2 and Serpine1 and the downregulated genes Cx3cl1, Cav1, Rhoa, Nppb and Prrx1. The most highly upregulated gene, Lypd8, represents a novel finding in the VSMC context. Inhibitor library screening and kinase activity profiling were applied to identify kinases in the involved signaling pathways. Putative upstream kinases identified by two different screens included PKC, Raf-1, Src, the MAP kinases p38 and JNK and the receptor tyrosine kinases EGFR and HGF/HGFR. As a novel finding, the Src family kinase Lyn was also identified as a putative upstream kinase.

CONCLUSIONS

α2B-adrenoceptors may mediate their pro-proliferative effects in VSMCs by promoting the activity of bFGF and PDGF and the growth factor receptors EGFR, HGFR and VEGFR-1/2. The Src family kinase Lyn was also identified as a putative upstream kinase. Lyn is known to be expressed in VSMCs and has been identified as an important regulator of GPCR trafficking and GPCR effects on cell proliferation. Identified Ser/Thr kinases included several PKC isoforms and the β-adrenoceptor kinases 1 and 2. Cross-talk between the signaling mechanisms involved in α2B-adrenoceptor-evoked VSMC proliferation thus appears to involve PKC activation, subsequent changes in gene expression, transactivation of EGFR, and modulation of kinase activities and growth factor-mediated signaling. While many of the identified individual signals were relatively small in terms of effect size, many of them were validated by combining pathway analysis and our integrated screening approach.

Cellular and molecular mechanisms of HGF/Met in the cardiovascular system

Met tyrosine kinase receptor, also known as c-Met, is the HGF (hepatocyte growth factor) receptor. The HGF/Met pathway has a prominent role in cardiovascular remodelling after tissue injury. The present review provides a synopsis of the cellular and molecular mechanisms underlying the effects of HGF/Met in the heart and blood vessels. In vivo, HGF/Met function is particularly important for the protection of the heart in response to both acute and chronic insults, including ischaemic injury and doxorubicin-induced cardiotoxicity. Accordingly, conditional deletion of Met in cardiomyocytes results in impaired organ defence against oxidative stress. After ischaemic injury, activation of Met provides strong anti-apoptotic stimuli for cardiomyocytes through PI3K (phosphoinositide 3-kinase)/Akt and MAPK (mitogen-activated protein kinase) cascades. Recently, we found that HGF/Met is also important for autophagy regulation in cardiomyocytes via the mTOR (mammalian target of rapamycin) pathway. HGF/Met induces proliferation and migration of endothelial cells through Rac1 (Ras-related C3 botulinum toxin substrate 1) activation. In fibroblasts, HGF/Met antagonizes the actions of TGFβ1 (transforming growth factor β1) and AngII (angiotensin II), thus preventing fibrosis. Moreover, HGF/Met influences the inflammatory response of macrophages and the immune response of dendritic cells, indicating its protective function against atherosclerotic and autoimmune diseases. The HGF/Met axis also plays an important role in regulating self-renewal and myocardial regeneration through the enhancement of cardiac progenitor cells. HGF/Met has beneficial effects against myocardial infarction and endothelial dysfunction: the cellular and molecular mechanisms underlying repair function in the heart and blood vessels are common and include pro-angiogenic, anti-inflammatory and anti-fibrotic actions. Thus administration of HGF or HGF mimetics may represent a promising therapeutic agent for the treatment of both coronary and peripheral artery disease.

Implication of anti-inflammatory macrophages in regenerative moto-neuritogenesis: promotion of myoblast migration and neural chemorepellent semaphorin 3A expression in injured muscle

Regenerative mechanisms that regulate intramuscular motor innervation are thought to reside in the spatiotemporal expression of axon-guidance molecules. Our previous studies proposed a heretofore unexplored role of resident myogenic stem cell (satellite cell)-derived myoblasts as a key presenter of a secreted neural chemorepellent semaphorin 3A (Sema3A); hepatocyte growth factor (HGF) triggered its expression exclusively at the early-differentiation phase. In order to verify this concept, the present study was designed to clarify a paracrine source of HGF release. In vitro experiments demonstrated that activated anti-inflammatory macrophages (CD206-positive M2) produce HGF and thereby promote myoblast chemoattraction and Sema3A expression. Media from pro-inflammatory macrophage cultures (M1) did not show any significant effect. M2 also enhanced the expression of myoblast-differentiation markers in culture, and infiltrated predominantly at the early-differentiation phase (3-5 days post-injury); M2 were confirmed to produce HGF as monitored by in vivo/ex vivo immunocytochemistry of CD11b/CD206/HGF-positive cells and by HGF in situ hybridization of cardiotoxin- or crush-injured tibialis anterior muscle, respectively. These studies advance our understanding of the stage-specific activation of Sema3A expression signaling. Findings, therefore, encourage the idea that M2 contribute to spatiotemporal up-regulation of extracellular Sema3A concentrations by producing HGF that, in turn, stimulates a burst of Sema3A secretion by myoblasts that are recruited to site of injury. This model may ensure a coordinated delay in re-attachment of motoneuron terminals onto damaged fibers early in muscle regeneration, and thus synchronize the recovery of muscle-fiber integrity and the early resolution of inflammation after injury.

Role of Akt signaling pathway in delayed cerebral vasospasm after subarachnoid hemorrhage in rats

BACKGROUND

Akt plays an important role in cell survival, proliferation, apoptosis and other activities. It also has been involved in maintaining smooth muscle cell contraction phenotypes in vitro and in vivo. Recent studies have focused on the inhibition of Akt in acute vasospasm and neuronal apoptosis after subarachnoid hemorrhage (SAH). However, its role in delayed cerebral vasospasm (DCVS) has not been reported.

METHODS

In this study, using a "two-hemorrhage" rat model of SAH, we examined the expression of p-Akt and the formation of vasospasm in the basilar arteries. To investigate the possible role of Akt in phenotypic switching, we performed immunohistochemical staining to examine expressions of SMα-actin and proliferating cell nuclear antigen (PCNA), markers of smooth muscle phenotypic switching.

RESULTS

We found that the basilar arteries exhibited vasospasm after SAH and that vasospasm became most severe on day 7 after SAH. Elevated protein expression of p-Akt was detected 4 days after SAH induction, peaked on day 7, and recovered on day 21, which was in a parallel time course to the development of DCVS. Moreover, results of immunohistochemical staining revealed enhanced expression of PCNA but gradual reduction in expression of SMα-actin from day 1 to day 7 after SAH; then, the expressions of PCNA and SMα-actin gradually recovered until day 21.

CONCLUSIONS

These results support a novel mechanism in which the Akt signaling pathway plays an important role in the proliferation of smooth muscle cells (SMCs) rather than inducing phenotype switching in basilar arteries, which promotes the development of DCVS after SAH.

Impact of tumor microenvironment and epithelial phenotypes on metabolism in breast cancer

PURPOSE

Cancer cells have altered metabolism, with increased glucose uptake, glycolysis, and biomass production. This study conducted genomic and metabolomic analyses to elucidate how tumor and stromal genomic characteristics influence tumor metabolism.

EXPERIMENTAL DESIGN

Thirty-three breast tumors and six normal breast tissues were analyzed by gene expression microarray and by mass spectrometry for metabolites. Gene expression data and clinical characteristics were evaluated in association with metabolic phenotype. To evaluate the role of stromal interactions in altered metabolism, cocultures were conducted using breast cancer cells and primary cancer-associated fibroblasts (CAF).

RESULTS

Across all metabolites, unsupervised clustering resulted in two main sample clusters. Normal breast tissue and a subset of tumors with less aggressive clinical characteristics had lower levels of nucleic and amino acids and glycolysis byproducts, whereas more aggressive tumors had higher levels of these Warburg-associated metabolites. While tumor-intrinsic subtype did not predict metabolic phenotype, metabolic cluster was significantly associated with expression of a wound response signature. In cocultures, CAFs from basal-like breast cancers increased glucose uptake and basal-like epithelial cells increased glucose oxidation and glycogen synthesis, suggesting interplay of stromal and epithelial phenotypes on metabolism. Cytokine arrays identified hepatocyte growth factor (HGF) as a potential mediator of stromal-epithelial interaction and antibody neutralization of HGF resulted in reduced expression of glucose transporter 1 (GLUT1) and decreased glucose uptake by epithelium.

CONCLUSIONS

Both tumor/epithelial and stromal characteristics play important roles in metabolism. Warburg-like metabolism is influenced by changes in stromal-epithelial interactions, including altered expression of HGF/Met pathway and GLUT1 expression.

Vascular anomalies: from genetics toward models for therapeutic trials

Vascular anomalies are localized abnormalities that occur during vascular development. Several causative genes have been identified not only for inherited but also for some sporadic forms, and the molecular pathways involved are becoming understood. This gives us the opportunity to generate animals carrying the causative genetic defects, which we hope model the phenotype seen in human patients. These models would enable us not only to test known antiangiogenic drugs, but also to develop novel approaches for treatment, directly targeting the mutated protein or molecules implicated in the pathophysiological signaling pathways.

α-Syntrophin is required for the hepatocyte growth factor-induced migration of cultured myoblasts

Syntrophins are adaptor proteins that link intracellular signaling molecules to the dystrophin based scaffold. In this study, we investigated the function of syntrophins in cell migration, one of the early steps in myogenic differentiation and in regeneration of adult muscle. Hepatocyte growth factor (HGF) stimulates migration and lamellipodia formation in cultured C2 myoblasts. In the migrating cells, syntrophin concentrated in the rear-lateral region of the cell, opposite of the lamellipodia, instead of being diffusely present throughout the cytoplasm of non-migrating cells. When the expression of α-syntrophin, the major syntrophin isoform of skeletal muscle, was reduced by transfection with the α-syntrophin-specific siRNA, HGF stimulation of lamellipodia formation was prevented. Likewise, migration of myoblasts from α-syntrophin knockout mice could not be stimulated by HGF. However, HGF-induced migration was restored in myoblasts isolated from a transgenic mouse expressing α-syntrophin only in muscle cells. Treatment of C2 myoblasts with inhibitors of PI3-kinase not only reduced the rate of cell migration, but also impaired the accumulation of syntrophins in the rear-lateral region of the migrating cells. Phosphorylation of Akt was reduced in the α-syntrophin siRNA-treated C2 cells. These results suggest that α-syntrophin is required for HGF-induced migration of myoblasts and for proper PI3-kinase/Akt signaling.

Molecular mechanisms underlying the activation of mammalian primordial follicles

In humans and other mammalian species, the pool of resting primordial follicles serves as the source of developing follicles and fertilizable ova for the entire length of female reproductive life. One question that has intrigued biologists is: what are the mechanisms controlling the activation of dormant primordial follicles. Studies from previous decades have laid a solid, but yet incomplete, foundation. In recent years, molecular mechanisms underlying follicular activation have become more evident, mainly through the use of genetically modified mouse models. As hypothesized in the 1990s, the pool of primordial follicles is now known to be maintained in a dormant state by various forms of inhibitory machinery, which are provided by several inhibitory signals and molecules. Several recently reported mutant mouse models have shown that a synergistic and coordinated suppression of follicular activation provided by multiple inhibitory molecules is necessary to preserve the dormant follicular pool. Loss of function of any of the inhibitory molecules for follicular activation, including PTEN (phosphatase and tensin homolog deleted on chromosome 10), Foxo3a, p27, and Foxl2, leads to premature and irreversible activation of the primordial follicle pool. Such global activation of the primordial follicle pool leads to the exhaustion of the resting follicle reserve, resulting in premature ovarian failure in mice. In this review, we summarize both historical and recent results on mammalian primordial follicular activation and focus on the up-to-date knowledge of molecular networks controlling this important physiological event. We believe that information obtained from mutant mouse models may also reflect the molecular machinery responsible for follicular activation in humans. These advances may provide a better understanding of human ovarian physiology and pathophysiology for future clinical applications.

Coordinated integrin and growth factor regulation of primary keratinocyte migration mediated through extracellular signal regulated kinase and phosphoinositide 3-kinase

We have examined coordinated integrin and growth factor regulation of primary keratinocyte migration mediated by phosphoinositide 3-kinase (PI3K) and mitogen-activated extracellular-regulated kinase (MEK)/extracellular signal-regulated kinase (ERK). On collagen I and fibronectin substrates, both epidermal growth factor (EGF) and hepatocyte growth factor (HGF) stimulated chemokinetic (random) and chemotactic (directional) migration. On provisional matrix, a combination of fibronectin and fibrin found in the early phase of wound healing, EGF and HGF-stimulated significant chemotactic but little or no chemokinetic cell movement. Blocking mAbs to integrin alpha2beta1 and alpha5beta1 effectively inhibited EGF- and HGF-stimulated chemokinetic and chemotactic cell movement on collagen I and fibronectin, respectively; however, HGF-stimulated chemotactic migration on collagen I was only partially inhibited by alpha2beta1 blocking mAb. Differentiated keratinocytes underwent reduced chemokinetic and chemotactic migration compared with undifferentiated keratinocytes; however, EGF-stimulated migration was reduced more than HGF-stimulated migration. When the migratory response on collagen I and fibronectin was assessed in the presence of the MEK-specific inhibitor PD98059, EGF- and HGF-stimulated chemotaxis was significantly reduced, whereas PD98059 had little effect on the stimulated chemokinesis. PI3K-specific inhibitor LY294002 reduced EGF- and HGF-stimulated chemokinesis and chemotaxis on collagen I and fibronectin. Thus beta1 integrins acted in concert with EGF and HGF to regulate migration of primary keratinocytes on extracellular matrix components via PI3K and MEK/ERK.

Tie2 in tumor endothelial signaling and survival: implications for antiangiogenic therapy

Signaling through the Tie2 receptor on endothelial cells has been shown to play an important role in normal and pathologic vascular development. We generated K1735 murine melanoma tumor cells that inducibly express soluble Tie2 receptor (Tie2Ex) to study the effects of inhibiting Tie2 signaling on tumor vasculature. Tie2Ex induction rapidly decreased AKT activation but not extracellular signal-regulated kinase (ERK) activation in tumor endothelial cells as detected by immunostaining. This was accompanied by an increase in endothelial cell TUNEL staining but no change in Ki-67 expression. Together with a decrease in the percentage of perfused vessels, this suggested that tumor vessel regression and impaired vascular function rather than angiogenesis inhibition was responsible for the delay in tumor growth following Tie2Ex treatment. However, Tie2Ex failed to inhibit the growth of larger, more established K1735 tumors. These tumors were additionally treated with sorafenib, a multikinase inhibitor that inhibits tumor endothelial cell ERK activation but not AKT activation. Combining Tie2Ex and sorafenib decreased both endothelial cell AKT and ERK activation, decreased endothelial cell survival and proliferation, and significantly inhibited growth of the more established tumors. These studies indicate that activity of specific signaling pathways and prosurvival effects are brought about by Tie2 activation in tumor endothelial cells, and knowledge of the effects of Tie2 inhibition can lead to development of more effective therapeutic regimens for inhibiting tumor neovascularization.

Over-expression of hepatocyte growth factor in smooth muscle cells regulates endothelial progenitor cells differentiation, migration and proliferation

BACKGROUND

Endothelial repair is one of key events after vascular injury. The mechanisms by which hepatocyte growth factor (HGF) and endothelial progenitor cells (EPCs) may be responsible for re-endothelialization of injured blood vessel wall are poorly understood.

METHODS

Primary culture SMCs were transfected with pcDNA3.0-HGF followed by G418 selection, one of G418-resistant colonies in well was picked, propagated and used as donor cells for further experiments. HGF and VEGF expression in SMCs were detected with western blot and enzyme linked immunosorbent assays (ELISA). Rat EPCs were cultured in untreated, pcDNA3.0 and pcDNA3.0-HGF transfected SMCs conditioned medium with or without anti-VEGF or exogenous recombinant HGF addition. eNOS, KDR and CD31 expression in EPCs was determined by real-time quantitative polymerase chain reaction (RT-qPCR) or flow cytometry; EPCs migration and proliferation were measured by using a modified Boyden chambers and MTT assay respectively.

RESULTS

Abundant and stable expression of HGF was found in G418-resistant colony-derived SMCs. VEGF expression significantly increased in HGF transfected SMCs. Exogenous recombinant HGF (rHGF) markedly up-regulated eNOS mRNA expression in EPCs and promoted EPCs migration and proliferation, but no significant changes were found in KDR and CD31 mRNA expression. HGF transfection in SMCs was more effective than exogenous HGF for EPCs differentiation, proliferation and migration.

CONCLUSIONS

Over-expression of HGF in SMCs can be helpful for promoting EPCs differentiation, increasing EPCs migration and proliferation. It may be responsible for angiogenesis of arteriosclerosis lesions and useful for blood vessel tissue engineering.

Hepatocyte growth factor and c-Met expression in pericytes: implications for atherosclerotic plaque development

Intraplaque neovascularization contributes to the progression of atherosclerosis. Our aim is to understand the mobilization of cells and factors involved in this process. We investigated the localization of hepatocyte growth factor (HGF) and its receptor, c-Met, in human atherosclerotic plaques, together with the effects of HGF on pericyte migration in vitro. Atherosclerotic femoral arterial segments were collected and analysed from 13 subjects who were undergoing lower limb amputation. Pericytes were identified in human lesions using a 3G5 antibody. Immunohistochemical analysis localized HGF mainly around microvessels, in association with some, but not all, CD31-positive endothelial cells. c-Met expression was mainly associated with smooth muscle cells and pericytes, around some, but not all, microvessels within the atherosclerotic lesions; no detection was apparent in normal internal mammary arteries. Using RT-PCR, we demonstrated expression of HGF and c-Met in a rat pericyte cell-line, TR-PCT1, and in primary pericytes. HGF treatment of TR-PCT1 cells induced their migration, but not their proliferation, in a dose-dependent manner (10-100 ng/ml, p<0.01), an effect mediated by activation of the serine/threonine kinase Akt, shown by western blot analysis. Treating the cells with the PI3K inhibitors Wortmannin (0.1 microM) or LY294002 (10 microM) abolished these effects. This work demonstrates the expression of c-Met and HGF in human atherosclerotic arteries, in association with SM-actin-positive cells and CD-31-positive cells, respectively. HGF induces pericyte migration via PI3-kinase and Akt activation in vitro. HGF and c-Met may be involved in neovascularization during plaque development, and may recruit pericytes to neovessels. Since pericytes are thought to mechanically stabilize new blood vessels, these factors may function to protect against haemorrhage.

Hepatocyte growth factor mediates angiopoietin-induced smooth muscle cell recruitment

Communication between endothelial cells (ECs) and mural cells is critical in vascular maturation. Genetic studies suggest that angiopoietin/Tie2 signaling may play a role in the recruitment of pericytes or smooth muscle cells (SMCs) during vascular maturation. However, the molecular mechanism is unclear. We used microarray technology to analyze genes regulated by angiopoietin-1 (Ang1), an agonist ligand for Tie2, in endothelial cells (ECs). We observed that hepatocyte growth factor (HGF), a mediator of mural cell motility, was up-regulated by Ang1 stimulation. We confirmed this finding by Northern blot and Western blot analyses in cultured vascular endothelial cells. Furthermore, stimulation of ECs with Ang1 increased SMC migration toward endothelial cells in a coculture assay. Addition of a neutralizing anti-HGF antibody inhibited Ang1-induced SMC recruitment, indicating that the induction of SMC migration by Ang1 was caused by the increase of HGF. Interestingly, Ang2, an antagonist ligand of Tie2, inhibited Ang1-induced HGF production and Ang1-induced SMC migration. Finally, we showed that deletion of Tie2 in transgenic mouse reduced HGF production. Collectively, our data reveal a novel mechanism of Ang/Tie2 signaling in regulating vascular maturation and suggest that a delicate balance between Ang1 and Ang2 is critical in this process.

Hepatocyte growth factor/scatter factor and MET are involved in arterial repair and atherogenesis

Several studies have shown that in the arterial wall hepatocyte growth factor/scatter factor (HGF/SF) is expressed by smooth muscle cells (SMCs) but acts on endothelial cells, not SMCs. Other studies, however, have indicated that SMCs can respond to HGF/SF. We have reinvestigated expression and activity of HGF/SF and its receptor MET in arterial SMC and endothelial cell cultures and in whole arteries after superficial or deep injury or atherogenesis. High-density cultures of SMCs produced HGF/SF but did not express MET, whereas SMCs, at the leading edge of injured cultures, expressed both ligand and receptor and showed a dramatic motility and growth response to HGF/SF. In line with these results, HGF/SF and MET expression was undetectable in the media of uninjured carotid arteries but was induced after deep arterial injury in areas of SMC migration in the neointima. Strong MET expression was also observed in the SMCs of the atherosclerotic lesions of homozygous apoE(-/-) mice, whereas HGF/SF was expressed by macrophage-derived foam cells. These results demonstrate that MET is induced in migrating and proliferating SMCs and that HGF/SF and MET are key mediators of the SMC response in atherogenesis.

Combined signaling through ERK, PI3K/AKT, and RAC1/p38 is required for met-triggered cortical neuron migration

Cell migration is a complex biological process playing a key role in physiological and pathological conditions. During central nervous system development, positioning and function of cortical neurons is tightly regulated by cell migration. Recently, signaling events involving the urokinase-type plasminogen activator receptor, which is a key regulator for the activation of hepatocyte growth factor (HGF), have been implicated in modulating cortical neuron migration. However, the intracellular pathways controlling neuronal migration triggered by the HGF receptor Met have not been elucidated. By combining pharmacological and genetic approaches, we show here that the Ras/ERK pathway and phosphatidylinositol 3-kinase (PI3K) are both required for cortical neuron migration. By dissecting the downstream signals necessary for this event, we found that Rac1/p38 and Akt are required, whereas the c-Jun N-terminal kinase (JNK) and mTOR/p70(s6k) pathways are dispensable. This study demonstrates that concomitant activation of the Ras/ERK, PI3K/Akt, and Rac1/p38 pathways is required to achieve full capacity of cortical neurons to migrate upon HGF stimulation.

Knockdown of c-Met by adenovirus-delivered small interfering RNA inhibits hepatocellular carcinoma growth in vitro and in vivo

c-Met is highly expressed and constitutively activated in various human tumors. We employed adenovirus-mediated RNA interference technique to knock down c-Met expression in hepatocellular carcinoma cells and observed its effects on hepatocellular carcinoma cell growth in vitro and in vivo. Among the five hepatocellular carcinoma and one normal human liver cell lines we analyzed, c-Met was highly expressed and constitutively tyrosine phosphorylated in only MHCC97-L and HCCLM3 hepatocellular carcinoma cells. Knockdown of c-Met could inhibit MHCC97-L cells proliferation by arresting cells at G0-G1 phase. Soft agar colony formation assay indicated that the colony forming ability of MHCC97-L cells decreased by approximately 70% after adenovirus AdH1-small interfering RNA (siRNA)/met infection. In vivo experiments showed that adenovirus AdH1-siRNA/met inhibited the tumorigenicity of MHCC97-L cells and significantly suppressed tumor growth when injected directly into tumors. These results suggest that knockdown of c-Met by adenovirus-delivered siRNA may be a potential therapeutic strategy for treatment of hepatocellular carcinoma in which c-Met is overexpressed.

Oxidized LDL inhibit hepatocyte growth factor synthesis in coronary smooth muscle cells

Hepatocyte growth factor (HGF) is a potent regeneration factor for endothelial and epithelial cells, and has also been shown to modulate extracellular matrix synthesis and matrix metalloproteinase activity in renal epithelial cells and tumor cells. Controversial results have been published concerning the possible role of HGF in the pathogenesis of coronary atherosclerosis. In this study, we have investigated the effect of oxidized low density lipoproteins (LDL) and elevated glucose concentrations on HGF synthesis in cultured human coronary artery smooth muscle cells. In addition, we have studied whether HGF modulates the release of extracellular matrix, extracellular matrix metalloproteinase inducer (EMMPRIN) and matrix metalloproteinases (MMP) by coronary artery smooth muscle cells. Oxidized LDL (1-10 microg/ml) induced a significant dose-dependent decrease of HGF release and a concomitant decrease of HGF mRNA expression, whereas native LDL and elevated glucose concentrations induced no significant changes of HGF synthesis. Incubation of cultured human coronary smooth muscle cells with human HGF (1-100 ng/ml) did not significantly alter cell migration and collagen I, fibronectin, EMMPRIN, MMP-1, MMP-2 and MMP-9 release. In summary, our results provide evidence that HGF does not promote coronary plaque growth or plaque destabilization. Regarding the fact that HGF is a potent endothelial cell regeneration factor, the observed downregulation of HGF synthesis by oxidized LDL supports the concept that HGF might be a protective factor in coronary atherosclerosis and that a decrease rather than an increase of HGF synthesis might promote coronary atherosclerosis.

Mechanical, biochemical, and extracellular matrix effects on vascular smooth muscle cell phenotype

The vascular smooth muscle cell (VSMC) is surrounded by a complex extracellular matrix that provides and modulates a variety of biochemical and mechanical cues that guide cell function. Conventional two-dimensional monolayer culture systems recreate only a portion of the cellular environment, and therefore there is increasing interest in developing more physiologically relevant three-dimensional culture systems. This review brings together recent studies on how mechanical, biochemical, and extracellular matrix stimulation can be applied to study VSMC function and how the combination of these factors leads to changes in phenotype. Particular emphasis is placed on in vitro experimental studies in which multiple stimuli are combined, especially in three-dimensional culture systems and in vascular tissue engineering applications. These studies have provided new insight into how VSMC phenotype is controlled, and they have underscored the interdependence of biochemical and mechanical signaling. Future improvements in creating more complex in vitro culture environments will lead to a better understanding of VSMC biology, new treatments for vascular disease, as well as improved blood vessel substitutes.

Hepatocyte growth factor effects on mesenchymal stem cells: proliferation, migration, and differentiation

Hepatocyte growth factor (HGF), a pleiotropic cytokine of mesenchymal origin promoting migration, proliferation, and survival in a wide spectrum of cells, can also modulate different biological responses in stem cells, but the mechanisms involved are not completely understood so far. In this context, we show that short-term exposure of mesenchymal stem cells (MSCs) to HGF can induce the activation of its cognate Met receptor and the downstream effectors ERK1/2, p38MAPK, and PI3K/Akt, while long-term exposure to HGF resulted in cytoskeletal rearrangement, cell migration, and marked inhibition of proliferation through the arrest in the G1-S checkpoint. When added to MSCs, the K252A tyrosine kinase inhibitor prevented HGF-induced responses. HGF's effect on MSC proliferation was reversed by p38 inhibitor SB203580, while the effects on cell migration were abrogated by PI3K inhibitor Wortmannin, suggesting that HGF acts through different pathways to determine its complex effects on MSCs. Prolonged treatment with HGF induced the expression of cardiac-specific markers (GATA-4, MEF2C, TEF1, desmin, alpha-MHC, beta-MHC, and nestin) with the concomitant loss of the stem cell markers nucleostemin, c-kit, and CD105.

Hepatocyte growth factor improved learning and memory dysfunction of microsphere-embolized rats

Hepatocyte growth factor (HGF), an organotropic factor for regeneration and protection in various organs, has the ability to attenuate cerebral ischemia-induced cell death. The effect of HGF on learning and memory function after cerebral ischemia, however, remains unknown. We have demonstrated that administration of human recombinant HGF (hrHGF) into the ventricle reduced prolongation of the escape latency in acquisition and retention tests of the water maze task on Days 12-28 after microsphere embolism-induced cerebral ischemia. Treatment with hrHGF also attenuated the decrease in viable area and the density and number of perfused cerebral vessels, particularly those with a diameter smaller than 10 microm, of the ipsilateral hemisphere on Day 28 after the cerebral ischemia. We observed that treatment with hrHGF reduced the number of TUNEL-positive cerebral endothelial cells at the early stage after the ischemia. These results suggest that hrHGF prevents learning and memory dysfunction seen after sustained cerebral ischemia by protecting against injury to the endothelial cells. HGF treatment may be a potent therapeutic strategy for cerebrovascular diseases, including cerebral infarct and vascular dementia.

Increased expression of hepatocyte growth factor in cerebrospinal fluid and intracranial artery in moyamoya disease

BACKGROUND AND PURPOSE

The etiology of moyamoya disease still remains unknown. This study was aimed to explore the role of hepatocyte growth factor (HGF), a strong inducer of angiogenesis, in development of moyamoya disease.

METHODS

We studied cerebrospinal fluid (CSF) from 39 patients with moyamoya disease (24 children and 15 adults), 6 control patients with cervical spondylosis, and 7 control patients with internal carotid artery occlusion. CSF level of HGF was determined by enzyme-linked immunosorbent assay technique. We also evaluated the distribution of HGF and its cellular receptor c-Met in the carotid fork obtained from 2 patients with moyamoya disease and 2 control patients.

RESULTS

CSF level of HGF was 408.2+/-201.6 pg/mL and 443.2+/-193.5 pg/mL in patients with cervical spondylosis and internal carotid artery occlusion, respectively (mean+/-SD). On the other hand, CSF level of HGF was 820.3+/-319.0 pg/mL in patients with moyamoya disease, being significantly higher than those in 2 control groups (P<0.01). Both HGF and c-Met were widely distributed in the media and thickened intima of the carotid fork in patients with moyamoya disease but not in control patients.

CONCLUSIONS

This study revealed that HGF is densely found in the carotid fork, and its CSF level is markedly elevated in moyamoya disease, suggesting that HGF may be a key protein for pathogenesis of moyamoya disease.

Influence of insulin-like growth factor-1 and hepatocyte growth factor on carotid atherosclerosis and cognitive function in the elderly

OBJECTIVE

This study investigated the relationship between serum levels of two neurotrophic factors, insulin-like growth factor-1 (IGF-1) and hepatocyte growth factor (HGF), and carotid atherosclerosis and cognitive function in the elderly.

METHODS

Serum levels of IGF-1 and HGF, carotid artery intima-media thickness (IMT), and Mini-Mental State Examination (MMSE) scores were determined in 60 subjects over 65 years old (35 patients with vascular dementia and 25 without dementia).

RESULTS

In all subjects IGF-1 levels showed a significant positive correlation with the MMSE score (r = 0.262, p = 0.0427) and a negative correlation with the IMT (r = -0.284, p = 0.0277) and the HGF level (r = -0.422, p = 0.0007). HGF levels were significantly correlated with IMT (r = 0.259, p = 0.0455) and lipoprotein(a) levels (r = 0.279, p = 0.0372). Mean MMSE scores and IGF-1 levels were significantly lower in patients with vascular dementia than in the non-demented controls. Mean IMT and the frequency of atherosclerotic plaque in the carotid arteries as well as the serum levels of HGF, LDL cholesterol, lipoprotein(a) and lipid peroxides were significantly increased in the demented patients compared with the non-demented controls.

CONCLUSION

A decrease of IGF-1 along with an increase of HGF may reflect an underlying biological process that influences cognitive decline as well as carotid atherosclerosis in the elderly.

Participation of PI3K and ERK1/2 pathways are required for human brain vascular smooth muscle cell migration

Human brain vascular smooth muscle cell (HBVSMC) migration contributes to angiogenesis and several pathological processes in the brain. However, the molecular mechanism of angiogenesis, in which smooth muscle cell contributes, remains unclear. Our study investigates the role of vascular endothelial growth factor (VEGF) in the HBVSMC migration and elucidates the chemotactic signaling pathway mediating this action. We used the in vitro 'scratch' wound method to detect the HBVSMC migration. VEGF(165) (1-40ng/ml) induced the HBVSMC migration in a dose-dependent manner (P<0.05). VEGF(165) does not induce HBVSMC proliferation. Wortmannin, a specific phosphatidylinositol 3-kinase (PI3K) inhibitor, significantly inhibited serine/threonine kinase Akt/protein kinase B (PKB) phosphorylation and reduced HBVSMC migration into the wound edge following VEGF(165) stimulation (P<0.05). PD98059, an extracellular signal-regulated kinase 1/2 (ERK1/2) inhibitor, also significantly inhibited ERK1/2 phosphorylation and reduced the numbers of SMC migration. Parallel distance measurement showed that VEGF(165) induced HBVSMC migration significantly reduced due to inhibition of PI3K or ERK1/2 phosphorylation (P<0.05). Our results demonstrate that VEGF(165) could induce HBVSMC migration but not proliferation in vitro. Inhibiting Akt/PKB or ERK1/2 phosphorylation could reduce VEGF(165) induced HBVSMC migration. We provide the first evidence that activation of PI3K or ERK1/2 pathways are a crucial event in VEGF(165) mediated signal transduction leading to HBVSMC migration.