Hepatocyte growth factor modulates migration and proliferation of human microvascular endothelial cells in culture

Hemodynamic effects of scatter factor in conscious rats

Scatter factor (SF), also known as hepatocyte growth factor, is a potent mitogen that has been suggested to exhibit greater efficacy than vascular endothelial growth factor (VEGF) in rabbits with hindlimb ischemia. Our study examined the effects of SF on cardiovascular hemodynamics and compared the responses to VEGF. Hemodynamic parameters were monitored before and after administration of SF or VEGF in conscious, instrumented rats. Intravenous injection of SF produced a dose-related reduction in mean arterial pressure (MAP) and increase in heart rate (HR). These responses were significantly attenuated by pretreatment with N omega-nitro-L-arginine methyl ester a nitric oxide (NO) synthase inhibitor, suggesting the depressor effect of SF may be mediated by NO. SF (250 micrograms/kg) reduced stroke volume and cardiac output, but did not affect the maximal first derivation of left ventricular pressure (dP/dt), suggesting that the reduction in cardiac output is caused by decreased stroke volume that probably results from a reduction in venous return. Compared with SF, VEGF produced greater hypotensive and tachycardic responses and greater reductions in stroke volume and cardiac output, indicating that SF has fewer side effects on hemodynamics. Although both growth factors might reduce venous return, SF decreased hematocrit presumably through venodilation, whereas VEGF increased hematocrit as a result of vascular hyperpermeability.

Immunolocalization of cytokines and their receptors in adhesive capsulitis of the shoulder

The purpose of this study was to test the hypothesis that specific cytokines are involved in the initiation and evolution of the fibrotic process in adhesive capsulitis of the shoulder. After approval from the Institutional Review Board, biopsies of shoulder capsule and synovium were collected during shoulder arthroscopy from 19 patients with adhesive capsulitis, 14 patients with nonspecific synovitis and no fibrosis or clinical evidence of adhesive capsulitis, and seven patients undergoing surgery for another pathology who had a normal capsule and synovium. Immunohistochemical localization with monoclonal antibodies to transforming growth factor-beta and its receptor, platelet-derived growth factor and its receptor, basic fibroblast growth factor, interleukin-1 beta, tumor necrosis factor-alpha, and hepatocyte growth factor was performed using standard immunoperoxidase techniques. The frequency of cytokine staining was correlated with the clinical diagnosis. Synovial cells, fibroblasts, T-cells, and B-cells were identified with specific antibodies, and newly synthesized matrix was examined for type-I and type-III collagen by immunohistochemical staining. The predominant cell types present were synovial cells and fibroblasts. Staining for type-III collagen in adhesive capsulitis tissues indicated new deposition of collagen in the capsule. There was staining for transforming growth factor-beta and its receptor, platelet-derived growth factor and its receptor, interleukin-1 beta, and tumor necrosis factor-alpha in adhesive capsulitis and nonspecific synovitis tissues, compared with minimal staining in normal capsule. Staining was more frequent in synovial cells than in capsular cells. The frequency of cell and matrix staining for transforming growth factor-beta, platelet-derived growth factor, and hepatocyte growth factor was greater in adhesive capsulitis tissues than in those from patients with nonspecific synovitis. No difference in the frequency of staining between primary (idiopathic) and secondary adhesive capsulitis was found. The results of this study indicate that adhesive capsulitis involves both synovial hyperplasia and capsular fibrosis. Cytokines such as transforming growth factor-beta and platelet-derived growth factor may be involved in the inflammatory and fibrotic processes in adhesive capsulitis. Matrix-bound transforming growth factor-beta may act as a persistent stimulus, resulting in capsular fibrosis. Understanding the basic pathophysiology of adhesive capsulitis is an important step in the development of clinically useful antifibrotic agents that may serve as novel treatments for patients with this conditions.

Enhancement of migration by protein kinase Calpha and inhibition of proliferation and cell cycle progression by protein kinase Cdelta in capillary endothelial cells

Activation of protein kinase C (PKC) induces angiogenesis, migration, and proliferation of endothelial cells (EC), but can also prevent growth factor-induced EC proliferation. To determine whether these disparate effects are mediated by substrates of individual PKC isoenzymes, PKCalpha and PKCdelta were overexpressed in rat microvascular EC. Basal and stimulated migration were enhanced in PKCalpha EC compared with either PKCdelta or control EC. Serum-induced growth of PKCdelta EC was decreased, while that of PKCalpha cells was similar to control EC. Phorbol ester markedly inhibited PKCdelta EC growth but enhanced growth of PKCalpha and control EC. To determine possible causes for this altered proliferation, the effect of PKCdelta on adhesion, mitogen-activated protein kinase activity, and cell cycle progression was measured. Adherence of PKCdelta EC to vitronectin was significantly enhanced. Serum-induced extracellular signal-regulated kinase-2 activity was increased equally in both PKCalpha and PKCdelta EC above that of control, while extracellular signal-regulated kinase-1 activity was similar in all EC. Cell cycle analysis suggested that PKCdelta EC entered S phase inappropriately and were delayed in passage through S phase. Thus, PKCalpha may mediate some proangiogenic effects of PKC activation; conversely, PKCdelta may direct antiangiogenic aspects of overall PKC activation, including slowing of the cell cycle progression.

Regulation of angiogenesis by scatter factor

Scatter factor (SF, hepatocyte growth factor) is a cytokine that stimulates motility, proliferation, and morphogenesis of epithelia. These responses are transduced through a tyrosine kinase receptor that is encoded by a proto-oncogene (c-met). SF is a potent angiogenic molecule, and its angiogenic activity is mediated, in part, through direct actions on endothelial cells. These include stimulation of cell motility, proliferation, protease production, invasion, and organization into capillary-like tubes. SF also stimulates the proliferation of smooth muscle cells and pericytes, cell types that also participate in the formation of capillaries and other microvessels. SF is chronically overexpressed in tumors, and it is postulated SF may function as a tumor angiogenesis factor. SF production in tumors may be due, in part, to an abnormal tumor: stroma interaction in which tumor cells secrete soluble proteins (SF-inducing factors) that stimulate stromal cell SF production and in part to autocrine production by the tumor cells themselves. Recent studies suggest a linkage between tumor suppressors (anti-oncogenes) and inhibition of angiogenesis. We hypothesize that tumor suppressor gene mutations may contribute to activation of an SF-->c-met signalling pathway, leading to an invasive and angiogenic tumor phenotype. Modulation of this pathway may provide clinically useful methods of enhancing or inhibiting angiogenesis.

Acquisition of invasive phenotype in gallbladder cancer cells via mutual interaction of stromal fibroblasts and cancer cells as mediated by hepatocyte growth factor

Growth and motility of carcinoma cells are regulated through their interactions with host stromal cells, i.e., tumor-stromal interactions. Hepatocyte growth factor (HGF), a ligand for c-Met tyrosine kinase, is a stromal-derived regulator of growth, motility, and morphogenesis. HGF stimulated proliferation and motility of GB-d1 gallbladder carcinoma cells from a patient with gallbladder cancer. HGF induced in vitro invasion of GB-d1 cells into a collagen gel matrix, and this potent, invasive effect was not seen with epidermal growth factor, transforming growth factor-beta 1, basic fibroblast growth factor, or platelet-derived growth factor. Although GB-d1 did not produce HGF, the cells did produce a factor which enhances HGF production in human skin fibroblasts, and this factor proved to be interleukin-1 beta (IL-1 beta). When GB-d1 cells were co-cultured with fibroblasts such that a collagen gel matrix was layered between the GB-d1 cells and fibroblasts, GB-d1 cells invaded the gel, but invasion of the cells in the co-culture system was inhibited by antibodies against HGF and partially inhibited by antibodies against IL-1 beta. Thus, GB-d1 cell-derived IL-1 beta stimulates HGF production in stromal fibroblasts and HGF up-regulated in the fibroblasts induces invasion of GB-d1 cells. The looped interaction of carcinoma cells and stromal fibroblasts mediated by HGF and a HGF-inducer such as IL-1 beta may be one mechanism which would explain the acquisition of malignant phenotype through tumor-stromal interactions.

Upregulation of molecular motor-encoding genes during hepatocyte growth factor- and epidermal growth factor-induced cell motility

Hepatocyte growth factor (HGF) and epidermal growth factor (EGF) are known to stimulate the locomotion of epithelial cells in culture. However, the molecular mechanisms which mediate these important changes are poorly understood. Here we have determined the effects of HGF and EGF on hepatocyte morphology, cytoskeletal organization, and the expression of molecular motor-encoding genes. Primary cultures of hepatocytes were treated with 10 ng/ml of HGF or EGF and observed with phase and fluorescence microscopy at 10, 24, and 48 h after treatment. We found that, over time, treated cells spread and became elongated after 24 h of treatment while forming long processes with dramatic alterations in the microtubule and actin cytoskeletons by 48 h. Quantitative Northern blot analysis was performed to measure expression of cytoskeletal-(beta-actin, alpha-tubulin) and molecular motor-(dynein, kinesin, and myosin I alpha and II) encoding genes which may contribute to this change in form. We observed the highest increase in levels of expression for myosin II (3.3-fold), kinesin (2.7-fold), myosin I alpha (2.2-fold), and alpha-tubulin (1.9-fold) after only 2 h of treatment with HGF. In contrast, EGF upregulated the expression of myosin I alpha (2.4-fold), kinesin (1.5-fold), and dynein (1.5-fold) at 10 h. The expression of the beta-actin gene remained constant in HGF-treated cells, while EGF induced a slight upregulation after 10 h of treatment. These results show for the first time that a selective upregulation of molecular motor-encoding genes correlates with alterations in cell shape and motility induced by HGF and EGF.

Plasma hepatocyte growth factor levels are increased in systemic inflammatory response syndrome

Interleukin-1 (IL-1), a cytokine released from macrophages by endotoxin stimulation, has been shown to upregulate the genetic expression of the hepatocyte growth factor (HGF). The present study was conducted to determine whether plasma HGF is increased in patients with systemic inflammatory response syndrome (SIRS). The plasma levels of HGF, endotoxin, and beta-glucan were measured in 41 surgical patients without hepatic diseases, 18 of whom had been diagnosed with sepsis, and 33, with nonseptic SIRS. The plasma HGF was found to be significantly increased in the 18 patients with sepsis, at 0.69 +/- 0.47 ng/ml (mean +/- SD), and in the 23 patients with nonseptic SIRS, at 0.49 +/- 0.37 ng/ml, compared to values in 40 normal controls, at 0.10 +/- 0.03 ng/ml (P < 0.001). No significant correlations were observed between the plasma levels of HGF and endotoxin (r = 0.02) or beta-glucan (r = -0.05) in any of the patients; however, plasma HGF was significantly correlated with the WBC count (r = 0.34, P < 0.05) and with total bilirubin (r = 0.45, P < 0.01). Plasma HGF was also strongly correlated with alanine transaminase (ALT) in 8 patients with ALT levels higher than 50 U/l (r = 0.70), but there was no such correlation in 33 patients with ALT levels of 50 U/l or less (r = 0.30). Thus, although the clinicopathologic significance of HGF is not well understood, the present findings indicate that plasma HGF increases in response to infection or inflammation.

Mediators, cytokines, and growth factors in liver-lung interactions

Multiple mediators have been implicated in the interactions between the liver and the lungs in various disease states. The best characterized mediator of liver-lung interaction is alpha 1-antitrypsin. Several cytokines and mediators may be involved in the pathogenesis of the hepatopulmonary syndrome and in the cytokine cascades that are activated in systemic inflammatory states such as acute respiratory distress syndrome. Hepatocyte growth factor or scatter factor is a recently described peptide with a broad range of biologic effects that may mediate lung-liver interactions.

Relationship of hepatocyte growth factor in human umbilical vein serum to gestational age in normal pregnancies

Hepatocyte growth factor (HGF) is expressed in placental syncitium and fetal organs and acts as a mitogen, motogen, and morphogen in vitro, suggesting a role in fetal growth and development. We aimed to examine the correlates of serum HGF in human cord blood. HGF was measured by ELISA using recombinant human HGF and mouse MAb to recombinant human HGF (Immunology Institute, Tokyo). Umbilical vein blood was collected prospectively at 148 deliveries including 94 normal pregnancies and 54 pregnancies complicated by medical conditions, primarily diabetes mellitus and pregnancy-induced hypertension. Growth parameters, gestation, pregnancy history, and perinatal events were recorded. Sera from 54 adolescents and 32 adult controls were also analyzed. Cord HGF [0.97 (0.66-1.33) ng/mL] [median (25-75 percentile)] was higher than HGF levels in adolescent sera [0.28 (0.21-0.35) ng/mL, p < 0.0001] and adult control sera [0.23 (0.14-0.31) ng/mL, p < 0.0001]. Cord HGF correlated with gestational age (r = 0.42, p = 0.0001) in normal pregnancies, with term babies (n = 69) having higher cord HGF than babies less than 37 wk of gestation (n = 25) [1.11 (0.78-1.45), 0.78 (0.46-1.03) ng/mL, p = 0.0007]. However, there was no relationship between gestation and cord HGF in complicated pregnancies. Cord HGF did not differ at term between appropriate for gestational age babies and small for gestational age babies. There were no independent correlations between cord HGF and birth weight, birth length and placental weight. We provide evidence for the first time that cord HGF levels are high and relate to gestation in normal pregnancies. HGF may have a significant role in fetal development during pregnancy.

The role of lipoprotein(a) in atherogenesis and thrombosis

Lipoprotein(a) [Lp(a)] represents an important independent risk factor for atherosclerotic cardiovascular disease. Lp(a) constitutes a class of low-density lipoprotein-like particles that are structurally heterogeneous due to variability within the distinguishing apoprotein, apolipoprotein(a) [Apo(a)]. Apo(a) bears a high degree of homology to the fibrinolytic zymogen, plasminogen, the parent molecule of the serine protease plasmin. Apo(a) contains a variable number of tandemly repeated triple-loop units called kringles, which appear to mediate Lp(a)'s interactions with fibrin and cell surface receptors. Although the mechanism of its atherogenicity is unknown, Lp(a) has been implicated in the delivery of cholesterol to the injured blood vessel, in blockade of plasmin generation on fibrin and cell surfaces, and as a stimulus for smooth muscle cell proliferation. In addition, new members of the plasminogen/Apo(a) gene family have been defined, creating a potential link between Lp(a) and the control of angiogenesis in both health and disease. Pharmacologic therapy of elevated Lp(a) levels has been only modestly successful; apheresis remains the most effective therapeutic modality.

Heparin-binding epidermal growth factor-like growth factor: p91 activation induction of plasminogen activator/inhibitor, and tubular morphogenesis in human microvascular endothelial cells

Epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) stimulates cell migration, proliferation and the formation of tube-like structures of human microvascular endothelial cells in culture. Heparin-binding EGF-like growth factor(HB-EGF), which shows 35% homology with EGF/TGF-alpha, is a member of the EGF family, and it is ubiquitous in many tissues and organs. We examined whether or not HB-EGF induced angiogenic responses in human microvascular endothelial cells. HB-EGF inhibited the binding of (125) I-EGF to the EGF receptor and induced autophosphorylation of the receptor on endothelial cells. Exogenous HB-EGF induced the loss of more than 70% of the EGF receptor from the cell surface within 30 min, with similar kinetics to that of EGF. The level of c-fos mRNA markedly increased at 30 min in response to HB-EGF as well as EGF. A gel shift assay demonstrated the activation of the transcription factor p91 by HB-EGF and EGF. This factor directly interacts with EGF receptor and mediates the activation of c-fos gene promoter. HB-EGF enhanced the mRNA expression of tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) mRNA. However, the enhancement of t-PA and PAI-1 by HB-EGF was less than that by EGF. Heparitinase/chlorate, which digests the heparan sulfate proteoglycan of the endothelial cell surface, restored both t-PA and PAI-1 mRNA levels in response to HB-EGF in a manner similar to that by EGF. HB-EGF at 10 ng/ml developed tube-like structures in type I collagen gel at similar levels to that of EGF at 10 ng/ml, suggesting that HB-EGF is also a potent angiogenic factor in the model system for angiogenesis. The tubulogenesis activity of HB-EGF is discussed in relation to the expression of the t-PA and PAI-1 genes.

Basic fibroblast growth factor stimulates hepatocyte growth factor/scatter factor secretion by human mesenchymal cells

Basic fibroblast growth factor (bFGF) together with other pleiotropic factors plays an important role in many complex physiological processes such as embryonic development, angiogenesis, and wound repair. Among these factors, hepatocyte growth factor/scatter factor (HGF/SF) which is secreted by cells of mesodermal origin exerts its mito- and motogenic activities on cells of epithelial and endothelial origin. Knowledge of the regulatory mechanisms of HGF/SF may contribute to the understanding of its role in physio-pathological processes. We observed that the secretion of HGF/SF by MRC-5 cells and by other fibroblast-derived cell cultures in conditioned media was enhanced by exposure to bFGF. HGF/SF was measured by the scatter assay, a bioassay for cell motility, and was further characterized by Western blot analysis with anti-HGF/SF antibodies. Exposure of MRC-5 cultures to 10 ng/ml of bFGF resulted already 6 h posttreatment in a threefold higher amount of scatter factor secreted into the medium as compared to untreated cultures. HGF/SF secretion was sustained after bFGF treatment for the following 72 h when increased amounts of HGF/SF were detected both in conditioned media as well as associated to the extracellular matrix. The secretion of HGF/SF in cell supernatants increased dose dependently upon treatment with bFGF starting from basal levels of 6 U/ml and reaching 27 U/ml at 30 ng/ml bFGF, plateauing thereafter. Upregulation of HGF/SF by IL-1, already described by others, was confirmed in this study. Based on our findings an articulated interaction can be speculated for bFGF, HGF/SF, and IL-1, e.g., in tissue regeneration during inflammatory processes or in wound healing.

Localisation of hepatocyte growth factor and its receptor (c-met) protein and mRNA in human term placenta

Successful pregnancy depends upon placental growth and development, which follows a specific spatial and temporal sequence. Hepatocyte Growth Factor (HGF) is a potent mitogen, morphogen and motogen to both endothelial and epithelial cell types and is linked to a tyrosine kinase, proto-oncogene, c-met receptor. In 'normal' third trimester placentae (n = 5) full thickness biopsies (obtained at Caesarean section), immunolocalisation and in situ hybridisation studies were performed for HGF and c-met., respectively. HGF immunoreactive protein was present in mesenchymal core, the vaculosyncytial membrane (syncytotrophoblast) and the vascular endothelial cells of villous trophoblast. The HGF mRNA was present particularly strongly in the perivascular stromal cells surrounding the villous vasculature and the amnion/chorionic membranes. Immunoreactive c-met protein was strongly localised to the endothelial cells lining the villous vasculature and the vasculosyncytial membrane. A relatively weak and diffuse hybridisation signal for c-met mRNA was present throughout the villous trophoblast, most pronounced in the vasculosyncytial membrane. These results indicate that HGF may serve as a paracrine mediator to control placental development and growth.

In vivo activation of met tyrosine kinase by heterodimeric hepatocyte growth factor molecule promotes angiogenesis

Hepatocyte growth factor (HGF) is a powerful motogen and mitogen for epithelial cells. The factor is a 90-kD heterodimer composed of an alpha chain containing four kringle motifs and a beta chain showing structural homologies with serine proteases. It is, however, devoid of enzymatic activity. Recently, it has been reported that HGF activates migration and proliferation of endothelial cells and is angiogenic. In this article we discuss (1) the molecular domains of HGF required to activate in vitro and in vivo endothelial cells, studied by use of molecular mutants, and (2) the characteristics of the angiogenic response to HGF in an experimental model system of implanted reconstituted basement membrane (Matrigel). Two groups of mutants were made and used in vitro and in vivo: one with deletions of kringle domains and one with substitution at the cleavage site of the HGF precursor. In vitro, HGF variants containing only the first two (HGF-NK2) or the first three kringles (HGF-NK3) of the alpha chain did not induce proliferation of endothelial cells even if used at concentration 160-fold higher than that optimal for HGF (0.05 nmol/L). High concentrations of these mutants (4 to 8 nmol/L) activated a little endothelial cell motogenic response that was 60% lower than that elicited by HGF. Substitution of Arg 489 with Gln 489 in the HGF precursor generated an uncleavable single-chain factor, unable to induce either endothelial cell migration or proliferation. In vivo, HGF induced a dose-dependent angiogenic response, which was enhanced by heparin.

Comparative study of hepatocyte growth factor/scatter factor and keratinocyte growth factor effects on human keratinocytes

Hepatocyte growth factor/scatter factor (HGF/SF) and keratinocyte growth factor (KGF, also designated FGF-7) are paracrine growth factors secreted by mesenchymal cells and active on a variety of epithelial cell types. In this study, the biologic responses of keratinocytes to these paracrine growth factors were compared. Stimulation of mitogenesis, migration, plasminogen activator (PA) activity, and fibronectin production were examined using human foreskin keratinocytes cultured in serum-free MCDB 153 medium. Although the two factors stimulated a similar level of proliferation when cells were maintained for 5 d in 1.8 mM Ca++, the peak effect of KGF, observed at 10 ng/ml, was approximately threefold higher than that of HGF/SF when cells were in medium containing 0.15 mM Ca++. Both agents promoted the migration of cells in low-calcium medium (0.08 mM Ca++). However, the magnitude of the response was approximately twofold greater for HGF/SF at 10 ng/ml than KGF at the same concentration. None of the matrix proteins such as type I collagen, type IV collagen, laminin, or fibronectin either stimulated or suppressed HGF/SF- or KGF-stimulated keratinocyte migration. Both factors stimulated PA activity of the cell extracts, especially urokinase-type, with similar potencies. Promoted PA activity was maximal with the addition of 10 ng/ml of either factor. Neither factor increased the production of fibronectin under conditions in which transforming growth factor-beta 1 was active. These results indicate that HGF/SF and KGF, both recognized as paracrine growth factors, elicit distinctive patterns of response by keratinocytes, implying that they have different roles in epidermal physiology.

Regulation of Wnt5a mRNA expression in human mammary epithelial cells by cell shape, confluence, and hepatocyte growth factor

The Wnts are a family of genes with a role in cell fate and morphological development in numerous embryonic and adult tissues. In mouse mammary tissue a subset of the Wnts have a function in the normal development of the gland, and aberrant expression of Wnts normally silent in this tissue causes mammary carcinomas. We have previously shown that Wnt5a expression is elevated in the epithelial component of proliferative lesions of human breast and have therefore examined the regulation of Wnt5a mRNA expression in the human mammary epithelial cell line HB2, which has a luminal phenotype and thus represents the most commonly transformed cell type in human breast cancer. Wnt5a was up-regulated 30-fold at confluence. This up-regulation was induced specifically by confluence and not by the growth arrest that accompanied it. In addition, Wnt5a was down-regulated 3-fold by changes in cell shape associated with the transition from growth on a two-dimensional surface (flat cell morphology) to growth in three-dimensional gels (spherical cell morphology). Cytoskeletal disruption with non-toxic doses of colchicine also induced a spherical morphology and brought about a dose-dependent down-regulation of Wnt5a. Wnt5a was also down-regulated 10-fold during the hepatocyte growth factor-induced branching of HB2 cell aggregates in collagen gels. The down-regulation of Wnt5a preceded the branching process. A similar result was obtained with primary human breast epithelial populations and the breast cancer cell line MDA468. We conclude that regulation of Wnt5a expression is a down-stream effect of signaling by hepatocyte growth factor. These results are consistent with a role for Wnt5a in mammary epithelial cell motility and are in accord with Xwnt5a's function in embryonal cell migration. If Wnt5a's function in human mammary epithelial cells is similar to that of Xwnt5a, its up-regulation at confluence may be a mechanism for inhibition of cell migration beyond confluence.

The biology of hepatocyte growth factor/scatter factor

Hepatocyte growth factor, a potent mitogen for epithelial and other cell types, and scatter factor, a stimulant of epithelial cell motility are identical. In addition to these mitogenic and motogenic functions, the factor has been shown to be an epithelial morphogen and also has antiproliferative effects in some cancer cell lines. The membrane receptor for hepatocyte growth factor/scatter factor has been identified as the c-met proto-oncogene product.

Expression of tissue-type plasminogen activator and its inhibitor couples with development of capillary network by human microvascular endothelial cells on Matrigel

Human omental microvascular endothelial (HOME) cells seeded on Matrigel begin to migrate within 1 h, forming honeycomb-like structures and capillary-like networks within 18 h. Cross-sections of the capillary networks show them to be tube-like structures. Northern blot analysis showed that tissue-type plasminogen activator (t-PA) mRNA synthesis increased from the initial state at 0 h after seeding on Matrigel, reaching a steady state after 4 h. This elevated cellular t-PA mRNA level decreased markedly at 24 h. In contrast, the cellular plasminogen activator inhibitor-1 (PAI-1) mRNA level demonstrated biphasic curves during the 24 h after seeding on Matrigel: the PAI-1 mRNA level was increased eightfold initially at 4 h over that at 0 h, then declined, and again secondarily increased to greater than tenfold at 18 h. Cellular levels of both 72 kD type IV collagenase and tissue inhibitor of metalloproteinase (TIMP-2) mRNA were increased only a slightly within 2-4 h. These elevated mRNA levels were maintained for 18 h, while the TIMP-1 mRNA level increased up to 18 h, reaching around three times the level at 0 h. However, on collagen-coated dishes, cellular levels of t-PA, PAI-1, 72 kD type IV collagenase, TIMP-1, and TIMP-2 mRNA were not greatly changed during incubation for 24 h. On Matrigel, the cellular t-PA mRNA level at 18 h after seeding was greatly increased when treated with specific anti-transforming growth factor-beta (TGF-beta) antibody. In contrast, both PAI-1 and TIMP-1 mRNA levels at 18 h were reduced in the presence of anti-TGF-beta antibody. Development of the capillary network on Matrigel was inhibited in the presence of anti-t-PA antibody. Epidermal growth factor (EGF) enhanced t-PA gene expression and TGF-beta inhibited its expression in HOME cells cultured on collagen-coated dishes. On the other hand, TGF-beta enhanced cellular expression of the PAI-1 gene. The formation of a capillary network by HOME cells on Matrigel appears to be balanced by angiogenic EGF and anti-angiogenic TGF-beta through modulation of PA activity.

Biological activation of pro-HGF (hepatocyte growth factor) by urokinase is controlled by a stoichiometric reaction

Hepatocyte growth factor (HGF) is a paracrine inducer of morphogenesis and invasive growth in epithelial and endothelial cells. HGF is secreted by mesenchymal cells as an inactive precursor (pro-HGF). The crucial step for HGF activation is the extracellular hydrolysis of the Arg494-Val495 bond, which converts pro-HGF into alpha beta-HGF, the high-affinity ligand for the Met receptor. We previously reported that the urokinase-type plasminogen activator (uPA) activates pro-HGF in vitro. We now show that this is a stoichiometric reaction, and provide evidence for its occurrence in tissue culture. Activation involves the formation of a stable complex between pro-HGF and uPA. This complex was isolated from the in vitro reaction of pure uPA with recombinant pro-HGF, as well as from the membrane of target cells, after sequential addition of uPA and pro-HGF. On the cell membrane, the uPA-HGF complex was bound to the Met receptor. Monocytic cell lines, and primary monocytes after adhesion, activated efficiently pro-HGF both on their surface and in the culture medium. This activation was inhibited by anti-catalytic anti-uPA antibodies, and occurred by a stoichiometric reaction. The stoichiometry of the activation reaction suggests that the biological effects of HGF can be titrated in vivo by the level of uPA activity. Adequate amounts of uPA can be locally provided by the macrophages, which would condition the tissue microenvironment by rendering HGF bioavailable to its target cells.

Scatter factor and angiogenesis

Scatter factor (hepatocyte growth factor) is a mesenchyme-derived cytokine that stimulates motility, proliferation, and morphogenesis of epithelia. These responses are transduced through the c-met protooncogene product, a transmembrane tyrosine kinase that functions as the SF receptor. SF is a potent angiogenic molecule, and its angiogenic activity is mediated primarily through direct actions on endothelial cells. These include stimulation of cell motility, proliferation, protease production, invasion, and organization into capillary-like tubes. SF is chronically overexpressed in tumors, suggesting that it may function as a tumor angiogenesis factor. SF production in tumors may be due, in part, to an abnormal tumor-stroma interaction, in which the tumor cells secrete factors (SF-IFs) that stimulate SF production by tumor-associated stromal cells. Studies suggest a link between tumor suppressors (antioncogenes) and inhibition of angiogenesis. We hypothesize that tumor suppressor gene mutations may contribute to the activation of an SF-IF-->SF-->c-met pathway, leading to an invasive and angiogenic tumor phenotype. Modulation of this pathway may, ultimately, provide clinically useful methods of enhancing or inhibiting angiogenesis.

Hepatocyte growth factor induces proliferation and differentiation of multipotent and erythroid hemopoietic progenitors

Hepatocyte growth factor (HGF) is a mesenchymal derived growth factor known to induce proliferation and "scattering" of epithelial and endothelial cells. Its receptor is the tyrosine kinase encoded by the c-MET protooncogene. Here we show that highly purified recombinant HGF stimulates hemopoietic progenitors to form colonies in vitro. In the presence of erythropoietin, picomolar concentrations of HGF induced the formation of erythroid burst-forming unit colonies from CD34-positive cells purified from human bone marrow, peripheral blood, or umbilical cord blood. The growth stimulatory activity was restricted to the erythroid lineage. HGF also stimulated the formation of multipotent CFU-GEMM colonies. This effect is synergized by stem cell factor, the ligand of the tyrosine kinase receptor encoded by the c-KIT protooncogene, which is active on early hemopoietic progenitors. By flow cytometry analysis, the receptor for HGF was found to be expressed on the cell surface in a fraction of CD34+ progenitors. Moreover, in situ hybridization experiments showed that HGF receptor mRNA is highly expressed in embryonic erythroid cells (megaloblasts). HGF mRNA was also found to be produced in the embryonal liver. These data show that HGF plays a direct role in the control of proliferation and differentiation of erythroid progenitors, and they suggest that it may be one of the long-sought mediators of paracrine interactions between stromal and hemopoietic cells within the hemopoietic microenvironment.

Hepatocyte growth factor/scatter factor stimulates hair growth of mouse vibrissae in organ culture

Hepatocyte growth factor/scatter factor (HGF/SF) is a multifunctional polypeptide that acts as a mitogen, motogen, or morphogen, depending on the biologic context. In this study, we examined the effect of HGF/SF on hair growth using a serum-free organ culture system. Vibrissal hair follicles isolated from newborn mice were cultured at 31 degrees C in 95% O2/5% CO2 for 72 h in the presence of various cytokines or growth factors, and elongation of hair shaft, DNA, and protein synthesis in hair follicles were measured. Among the agents tested, only HGF/SF significantly increased hair follicle length (p < 0.001), 3H-thymidine (p < 0.001), and 35S-cysteine (p < 0.05) incorporation. The effect of HGF/SF was dose dependent, with maximal stimulation obtained at 10 ng/ml. The increase in hair follicle length and thymidine incorporation were specifically inhibited by a neutralizing antibody against HGF/SF. These results indicate that HGF/SF can promote hair growth and may have clinical utility in this regard.

Expression of hepatocyte growth factor mRNA, and c-met mRNA (hepatocyte growth factor receptor) in human liver tumours

We have quantified mRNA for the hepatocyte growth factor and its putative receptor the c-met proto-oncogene protein product, in a series of human primary and secondary liver tumours and adjacent non-neoplastic liver. In all hepatocellular cancers, hepatocyte growth factor 6 kb mRNA expression was less (mean 23.93% +/- 6.33% S.E.M. n = 7) in the tumours than in the adjacent normal liver. Both relative over- and under-expression of c-met transcripts were found in tumour tissue compared to non-neoplastic liver. Thus hepatocellular cancer tissue does not over-express mRNA for hepatocyte growth factor, though this growth factor might play a role in hyperproliferative states leading to liver cancer.

The effect of various cytokines on hair growth of mouse vibrissae in organ culture

Hepatocyte growth factor/scatter factor (HGF) is a multifunctional polypeptide which acts as a mitogen, motogen or morphogen depending on the biological context. In this study, we examined the effect of HGF on hair growth using a serum-free organ culture system. Vibrissal hair follicles isolated from newborn mice were cultured at 31 degrees C in 95% O2-5%CO2 for 72 h in the presence of various cytokines or growth factors. DNA, protein synthesis and elongation of the hair shaft in the hair follicles were measured. Among the agents tested, only HGF significantly increased hair follicle length (P < 0.001) and 3H-thymidine (P < 0.001) incorporation. The effect of HGF was dose-dependent, with maximal stimulation obtained at 10 ng/ml. The increase in hair follicle length and thymidine incorporation were specifically inhibited by a neutralizing antibody against HGF. These results indicate that HGF is able to promote hair growth and may have clinical utility in this regard.

Cooperative roles of hepatocyte growth factor and plasminogen activator in tubular morphogenesis by human microvascular endothelial cells

Epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) stimulated cell migration, chemotaxis, and the expression of tissue-type plasminogen activator (t-PA) in human omental microvascular endothelial (HOME) cells. Hepatocyte growth factor (HGF) stimulated cell proliferation, but had a negligible stimulatory effect on cell migration, the expression of t-PA and tube-like formation into collagen gel in HOME cells. Basic fibroblast growth factor stimulated cell proliferation, cell migration, tubulogenesis and the expression of urokinase-type plasminogen activator (u-PA) in bovine aortic endothelial (BAE) cells. HOME and BAE cells had both high- and low-affinity receptors for HGF. In BAE cells, u-PA activity and tube-like structures in collagen gel were induced in the presence of HGF alone. In contrast, in HOME cells, t-PA activity and tube-like structures were induced in the presence of TGF-alpha alone, but not in the presence of HGF alone. However, we observed a marked induction of tube formation by HOME cells when both t-PA and HGF were added simultaneously. In the model system for tumor angiogenesis, when HOME cells were co-cultured with a renal cancer cell line, KPK13, tube-like structures were induced in the presence of HGF:KPK13 cells expressed large amounts of t-PA mRNA. Our present study suggested that HGF in concert with active t-PA could be angiogenic in HOME cells.

Cytokine control of cell motility: modulation and mediation by the extracellular matrix

Cytokines are multifunctional regulators of cell behaviour affecting such diverse activities as cell proliferation, gene expression and motility. Matrix macromolecules influence a similarly wide range of cell functions. A review of the available literature suggests that cytokines may affect cell motility by (a) directly influencing the motility apparatus, and (b) indirectly as a consequence of the altered expression of genes coding for matrix macromolecules, their respective cell surface receptors and matrix degrading enzymes and their inhibitors. Conversely, the composition and supramolecular organisation of the matrix plays a central role in defining cellular response to potentially multifunctional cytokines. Such complex and reciprocal interactions between cytokines and the matrix elicit both positive and negative reiterative feedback loops which must be taken into account when interpreting the results of migration assays in vitro and extrapolating them to in vivo processes.

Fibroblast migration and proliferation during in vitro wound healing. A quantitative comparison between various growth factors and a low molecular weight blood dialysate used in the clinic to normalize impaired wound healing

During the formation of granulation tissue in a dermal wound, platelets, monocytes and other cellular blood constituents release various peptide growth factors to stimulate fibroblasts to migrate into the wound site and proliferate, in order to reconstitute the various connective tissue components. The effect on fibroblast migration and proliferation of these growth factors, and of Solcoseryl (HD), a deproteinized fraction of calf blood used to normalize wound granulation and scar tissue formation, was quantified in vitro. The presence of basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF), transforming growth factor-beta (TGF-beta) and hemodialysate (HD) increased the number of cells in the denuded area, i.e., in the "wound space" of an artificially ruptured monolayer of LM-fibroblasts (mouse lung fibroblasts). When cell proliferation was blocked with Mitomycin C, in the first 24 h all factors, i.e., bFGF, PDGF, TGF-beta and HD, promoted cell migration, whereas after 48 h it became obvious that each factor stimulated both migration and proliferation, each in a characteristic way. The effects were significant and more distinct after 48 h, following the order: PDGF (46%) approximately bFGF (87%) > HD (45%) approximately TGF-beta (40%) > control (62%). The relative contributions of migration after inhibiting proliferation are given in brackets. The modulatory activity of HD was localized in its hydrophilic fraction. It was destroyed by acid hydrolysis. Furthermore, this activity could be blocked by protamine sulfate, an inhibitor blocking peptide growth factor receptor binding.

Hepatocyte growth factor/scatter factor, liver regeneration and cancer metastasis

Hepatocyte growth factor (HGF) is the most potent stimulator of hepatocyte growth and DNA synthesis identified; it is now known to be the same molecule as scatter factor, which increases the motility of a variety of cell types. HGF is becoming recognized as one of the most important factors in the regulation of liver regeneration after surgical resection or chemical damage. HGF is produced by several tissues, including neoplasms; it can therefore provide a stimulus for increased motility of malignant cells by both a paracrine and autocrine mechanism. The receptor for HGF has been identified as the product of the oncogene c-met, raising the possibility that this gene plays a key role in facilitating cellular invasion. HGF may therefore be important not only for liver cell growth but also in metastasis. This article summarizes the current position of research on HGF, and presents both clinical and scientific evidence that strongly implicates this factor in liver regeneration and cancer invasion and metastasis.

Anti-angiogenic activity of arachidonic acid metabolism inhibitors in angiogenesis model systems involving human microvascular endothelial cells and neovascularization in mice

We have established an in vitro angiogenesis model using human omental microvascular endothelial (HOME) cells, in which epidermal growth factor (EGF) or transforming growth factor-alpha (TGF-alpha) stimulated cell migration and tube formation. In this study, we examined whether alpha-guaiaconic acid (GR-12) and its synthetic 20 derivatives showed inhibition of cell migration and tubular formation of HOME cells. We found that GR-12 inhibits arachidonic acid metabolism, while GR-12 and one derivative, GS-01, inhibit tubular formation of endothelial cells in our model system. Confluent monolayers of HOME cells were damaged with a razor blade and incubated with or without TGF-alpha; HOME cell migration was stimulated about 1.5-fold over control values in the presence of TGF-alpha. Treatment of HOME cells with GR-12 or GS-01 inhibited both spontaneous and TGF-alpha-stimulated migration. GR-12 or GS-01 inhibited TGF-alpha-induced HOME-cell tube formation in type-1 collagen gels. We examined whether these compounds could modulate tubular formation of HOME cells induced by human cancer cells. Enhanced tube formation of HOME cells by co-cultured esophageal cancer cells was almost completely inhibited by co-administration of GR-12 or GS-01. Both compounds also inhibited formation of tubular networks of HOME cells on Matrigels. We also examined anti-angiogenic activity of these compounds in an in vivo model system of tumor angiogenesis in mice. In this system, GS-01 inhibited development of capillary networks at a rate comparable to that of a well-known anti-angiogenic compound, fumagillin, but GR-12 did not. The inhibitor of arachidonic acid metabolism is thus expected to modulate tumor angiogenesis.

Induction of vascular endothelial tubular morphogenesis by human glioma cells. A model system for tumor angiogenesis

We have developed two different models of tumor angiogenesis by human brain tumors: one being tube formation by bovine aortic endothelial (BAE) cells cocultured with tumor cells in vitro, and other being in vivo angiogenesis in mice when tumor cells are transplanted into the dorsal sac. We investigated whether tube formation could be induced in BAE cells in type I collagen gel when these cells were cocultured with seven human glioma cell lines. Four of the seven glioma cell lines, which had high levels of basic fibroblast growth factor (bFGF) mRNA, induced tube formation by BAE cells. The tube formation was blocked by coadministration of anti-bFGF antibody. In in vivo model system of tumor angiogenesis in mice, these four cell lines were highly angiogenic. In contrast, with the other three glioma cell lines, which had poor expression of bFGF, BAE cells showed no apparent tube formation. These three cell lines did not efficiently develop capillary networks in mice. The results demonstrated a correlative relationship in the tubulogenesis of BAE cells, bFGF mRNA levels and angiogenesis in mice. The present study with two model systems of tumor angiogenesis suggests that the angiogenesis of some human glioma cell lines is mediated by bFGF, possibly via paracrine control.

Irsogladine is a potent inhibitor of angiogenesis

We describe a novel inhibitor of angiogenesis, Irsogladine, an anti-ulcer drug. Irsogladine inhibited plasminogen activator synthesis of, and tube formation by, human microvascular endothelial cells in type 1 collagen gel treated with an angiogenic growth factor, EGF. Furthermore, Irsogladine administered orally significantly inhibited in vivo angiogenesis in mice. Irsogladine may be useful in the treatment of diseases associated with angiogenesis.

Regulation of spreading and growth of colon cancer cells by hepatocyte growth factor

Hepatocyte growth factor (HGF), also known as scatter factor, regulates both cell motility and the growth of some cell types. We have determined the effects of HGF on the motility and growth of human colon cancer cell lines (HT115, HT29, HRT18 and HT55). Cell motility, as measured by dissociation from carrier beads or by scattering of cell colonies, was greatly increased in all cell lines. The effects were completely blocked by anti-HGF antibody. In contrast, cell growth of HT115, HT29 and HRT18 cells was inhibited by a wide range of concentrations of HGF. HT55 cell growth was also inhibited but needed a prolonged culture period (> 5 days). The HGF receptor/Met protein is highly expressed in the membrane fraction of these cells as determined by Western blotting. It is concluded that HGF has an effect on both colon cancer cell motility and growth, which may be important in the control of the spread of colon cancer.

Cell-specific expression of hepatocyte growth factor in liver. Upregulation in sinusoidal endothelial cells after carbon tetrachloride

The cellular origin of hepatocyte growth factor (HGF), a polypeptide implicated in liver regeneration, was examined in normal liver and in hepatic regeneration induced by carbon tetrachloride. In normal liver, HGF and its mRNA were abundant in lipocytes, with smaller amounts present also in sinusoidal endothelial and Kupffer cells. In regenerating liver, HGF gene expression increased exclusively in endothelial cells. HGF mRNA levels rose sixfold in these cells, peaking at 6 h after toxin administration and returning to near normal by 24 h. The rise in HGF mRNA was accompanied by a 5.4-fold increase in HGF secretion. CCl4 did not alter HGF expression by either Kupffer cells or lipocytes; nor did it induce HGF expression by hepatocytes. Nonparenchymal liver cells contained two HGF transcripts: one predicting a full-length molecule of 728 amino acids; and the other encoding a functional five-amino acid deletion variant of HGF. The variant was less abundant than the full-length transcript, but increased in parallel with native HGF mRNA in response to CCl4. The response of nonparenchymal cells to HGF was examined by plating endothelial cells and lipocytes in the presence of recombinant human HGF. Under the conditions examined, the growth factor exerted neither mitogenic nor scatter factor activity on these cells.

Transfer of motogenic and invasive response to scatter factor/hepatocyte growth factor by transfection of human MET protooncogene

The MET protooncogene encodes p190MET, a tyrosine kinase which is the receptor for a molecule known as scatter factor or hepatocyte growth factor (SF/HGF). This molecule has different biological activities, including stimulation of cell motility, promotion of matrix invasion and, in some cells, mitogenesis. We have cloned the full-length MET cDNA and transfected it into NIH 3T3 fibroblasts. Stable transfectants expressed the p190MET receptor together with two previously described truncated forms of 140 and 130 kDa lacking the tyrosine kinase domain. All three forms bound radiolabeled SF/HGF. The factor stimulated tyrosine kinase activity of the transfected p190MET and induced changes in cell shape, migration in Boyden chambers, and invasion of collagen matrices in vitro. The motile and invasive phenotype was transient and strictly dependent on the presence of SF/HGF. The factor did not stimulate either cell growth or thymidine incorporation in transfected cells, while it promoted colony formation in soft agar in the presence of 5% fetal calf serum. These data show that, in the presence of its ligand, the MET receptor expressed in fibroblasts induces cells to pursue a motogenic-invasive rather than a proliferative program.

Induction of human microvascular endothelial tubular morphogenesis by human keratinocytes: involvement of transforming growth factor-alpha

Transforming growth factor-alpha(TGF-alpha), homologous to epidermal growth factor(EGF), is closely involved in hyperproliferation of human keratinocytes. Psoriasis is a common hyperproliferative skin disease characterized by hyperproliferation of keratinocytes and abnormal development of dermal capillary networks. In this study, we have examined whether keratinocytes could enhance angiogenesis. TGF-alpha or EGF efficiently stimulated formation of tubular-like structures of human omental microvascular endothelial(HOME) cells in type I collagen gels. Human keratinocytes produced TGF-alpha. To examine whether co-cultured keratinocytes could induce tubulogenesis of HOME cells in collagen gel, we have developed a co-culture system with human keratinocytes. Surprisingly, there appeared new development of many tubular-like structures of HOME cells in collagen gels when co-cultured with keratinocytes. This keratinocytes-dependent tubulogenesis was almost completely blocked when anti-TGF-alpha-antibody was present. The TGF-alpha molecules derived from keratinocytes appeared to enhance tubulogenesis of human microvascular endothelial cells. We propose the hypothesis that secretory TGF-alpha from human keratinocytes may promote an autocrine loop to proliferate the skin keratinocytes and also a paracrine loop to induce the skin angiogenesis.

Rapid and marked induction of hepatocyte growth factor during liver regeneration after ischemic or crush injury

Liver injuries induced by ischemia or physical trauma are characterized by noninflammatory damage frequently observed in a clinical setting. When the liver of rats was injured by ischemic treatment or physical crushing, necrotic tissue degeneration occurred in several sites of lobulus within 24 hr. Hepatocyte growth factor, a potent mitogen for adult rat hepatocytes in primary culture, was markedly induced in the livers of rats injured by ischemia or physical trauma. In both cases, the hepatocyte growth factor messenger RNA level in the injured liver reached about 10 to 20 times that of the normal level during 12 to 24 hr after liver injury. The increase in hepatocyte growth factor messenger RNA correlated well with the degree of liver damage as evaluated by serum ALT activity in the sera of rats. In situ hybridization showed that hepatocyte growth factor messenger RNA expression occurs in nonparenchymal liver cells, primarily in Kupffer cells of the ischemic liver. After the increase of hepatocyte growth factor messenger RNA in the injured liver, a marked compensatory hepatocyte DNA synthesis occurred 48 to 72 hr after these treatments. These results suggest that hepatocyte growth factor acts as a hepatotropic factor for liver regeneration after noninflammatory liver damage caused by ischemia and physical crush, probably through a paracrine mechanism.

Extracellular proteolytic cleavage by urokinase is required for activation of hepatocyte growth factor/scatter factor

The extracellular protease urokinase is known to be crucially involved in morphogenesis, tissue repair and tumor invasion by mediating matrix degradation and cell migration. Hepatocyte growth factor/scatter factor (HGF/SF) is a secretory product of stromal fibroblasts, sharing structural motifs with enzymes of the blood clotting cascade, including a zymogen cleavage site. HGF/SF promotes motility, invasion and growth of epithelial and endothelial cells. Here we show that HGF/SF is secreted as a single-chain biologically inactive precursor (pro-HGF/SF), mostly found in a matrix-associated form. Maturation of the precursor into the active alpha beta heterodimer takes place in the extracellular environment and results from a serum-dependent proteolytic cleavage. In vitro, pro-HGF/SF was cleaved at a single site by nanomolar concentrations of pure urokinase, generating the active mature HGF/SF heterodimer. This cleavage was prevented by specific urokinase inhibitors, such as plasminogen activator inhibitor type-1 and protease nexin-1, and by antibodies directed against the urokinase catalytic domain. Addition of these inhibitors to HGF/SF responsive cells prevented activation of the HGF/SF precursor. These data show that urokinase acts as a pro-HGF/SF convertase, and suggest that some of the growth and invasive cellular responses mediated by this enzyme may involve activation of HGF/SF.

Hepatocyte growth factor is a potent angiogenic factor which stimulates endothelial cell motility and growth

Hepatocyte Growth Factor (HGF, also known as Scatter Factor) is a powerful mitogen or motility factor in different cells, acting through the tyrosine kinase receptor encoded by the MET protooncogene. Endothelial cells express the MET gene and expose at the cell surface the mature protein (p190MET) made of a 50 kD (alpha) subunit disulfide linked to a 145-kD (beta) subunit. HGF binding to endothelial cells identifies two sites with different affinities. The higher affinity binding site (Kd = 0.35 nM) corresponds to the p190MET receptor. Sub-nanomolar concentrations of HGF, but not of a recombinant inactive precursor, stimulate the receptor kinase activity, cell proliferation and motility. HGF induces repairs of a wound in endothelial cell monolayer. HGF stimulates the scatter of endothelial cells grown on three-dimensional collagen gels, inducing an elongated phenotype. In the rabbit cornea, highly purified HGF promotes neovascularization at sub-nanomolar concentrations. HGF lacks activities related to hemostasis-thrombosis, inflammation and endothelial cells accessory functions. These data show that HGF is an in vivo potent angiogenic factor and in vitro induces endothelial cells to proliferate and migrate.

Up-regulation of hepatocyte growth factor gene expression by interleukin-1 in human skin fibroblasts

Hepatocyte growth factor (HGF) functions as a hepatotrophic and renotrophic factor for regeneration of the liver and kidney. When 1 ng/ml of interleukin-1 alpha (IL-1 alpha) or interleukin-1 beta (IL-1 beta) was added to cultures of human skin fibroblasts, the production of HGF was 5-6 fold higher than levels in the controls. HGF mRNA level in the cells was increased to 4-fold higher levels at 6 h after exposure to IL-1 alpha. Tumor necrosis factor-alpha and interferon-gamma but no other cytokine tested had slightly stimulatory effects on HGF production. The tumor promoter, tetradecanoylphorbol 13-acetate (TPA) markedly enhanced the stimulatory effect of IL-1 alpha and IL-1 beta on the production of HGF. The stimulatory effect of both IL-1 alpha and IL-1 beta and the synergistical stimulation with TPA were completely abrogated by 10 ng/ml TGF-beta 1 or 1 microM dexamethasone. These results suggest that IL-1 alpha and IL-1 beta are positive regulators for expression of the HGF gene and are likely have a role in regeneration of tissues following the occurrence of inflammatory diseases.

Processing of hepatocyte growth factor to the heterodimeric form is required for biological activity

Hepatocyte growth factor is a plasminogen-like molecule with diverse biological effects. Although it is synthesized as a single chain polypeptide, it was originally purified as a disulfide-linked heterodimer which was generated by an internal proteolytic event. Subsequent work indicated that preparations consisting largely of the monomeric form also exhibited potent activity. By using a combination of protease inhibition and site-directed mutagenesis, we established that conversion of the single chain polypeptide to the heterodimer occurred during the bioassay and was required for mitogenic and motogenic activity.

A model system for tumor angiogenesis: involvement of transforming growth factor-alpha in tube formation of human microvascular endothelial cells induced by esophageal cancer cells

Tumor growth is dependent on angiogenesis, which is thought to be mediated through growth factors, such as transforming growth factor-alpha (TGF-alpha) and -beta (TGF-beta), epidermal growth factor (EGF), and basic fibroblast growth factor (bFGF), produced by tumor cells. We have developed a model system for tumor angiogenesis in vitro: tube formation of human omentum microvascular endothelial (HOME) cells in type I collagen gels when these cells are co-cultured with tumor cells. Exogenously added TGF-alpha induced tube formation of HOME cells in collagen gel. In contrast, TGF-beta inhibited the TGF-alpha-induced tube formation of endothelial cells. We investigated whether tube formation could be induced in HOME cells in collagen gel when the HOME cells were co-cultured with three esophageal cancer cell lines, TE1, TE2, and TE5. TE1 and TE2 cells expressed both TGF-alpha and TGF-beta mRNA, but the level of TGF-alpha mRNA in TE2 was found to be much lower than in TE1 cells. TE5 did not express either TGF-alpha or TGF-beta. The tube formation of HOME cell was induced when they were co-cultured with TE1 cells, while both TE2 and TE5 cell lines induced tube formation at much lower rates than TE1. TE1-induced tube formation of HOME cells was specifically blocked by co-administration of anti-TGF-alpha-antibody, but not by anti-bFGF-antibody. The present study suggests that, in our model system, esophageal tumor angiogenesis is partly controlled by TGF-alpha, possibly through a paracrine pathway.

Marked induction of hepatocyte growth factor mRNA in intact kidney and spleen in response to injury of distant organs

Hepatocyte growth factor (HGF) is a potent mitogen for various epithelial cells, including mature hepatocytes and renal tubular cells. Here, HGF mRNA was found to be markedly increased in non-injured kidney and spleen, when the liver or kidney in rats was injured by 70% partial hepatectomy or unilateral nephrectomy. HGF mRNA increased to 3-4 fold higher level than the normal in the kidney and spleen as well as in the remnant liver after partial hepatectomy. Similarly, HGF mRNA markedly increased in the spleen as well as in the remnant kidney after unilateral nephrectomy. These results suggest that the onset of injury to the liver or kidney may be recognized by distal non-injured organs by the signalling of a humoral factor and that HGF derived from these organs may be involved in the regeneration of liver or kidney, through an endocrine mechanism.

Human enterocyte (Caco-2) migration is modulated in vitro by extracellular matrix composition and epidermal growth factor

The modulation of enterocyte sheet migration was studied using Caco-2 cells, a well-differentiated human colonic cell line. Although Caco-2 cells attached and spread equivalently over collagen types I, III, IV, and V and laminin, migration over laminin was significantly slower than migration over the collagen types. Fibronectin was a poor substrate for attachment, spreading, and migration. Epidermal growth factor (EGF) stimulated migration over laminin but did not alter Caco-2 migration over collagen or fibronectin. This effect was independent of cell proliferation, which was stimulated equivalently on both laminin and collagen I. Expression and organization of cell surface receptors for matrix (integrins) were studied using antibodies specific for beta and alpha integrin subunits. Integrin surface expression was assessed by immunoprecipitation of surface 125iodinated control and EGF-treated cells. Beta 1 surface pools did not change substantially in any condition studied. Alpha 1 subunit pools were decreased after EGF treatment on collagen I but alpha 1 pools increased after EGF treatment on laminin. Surface pools of alpha 2 subunits were increased following EGF treatment whether cells were cultured on laminin or collagen I. However, traditional immunofluorescent and laser confocal imaging demonstrated substantial differences in the character of alpha 2 subunit organization between collagen and laminin in the migrating cell front. Furthermore, a functional antibody to the alpha 2 subunit inhibited EGF stimulation of migration over laminin without substantial effects on basal migration over laminin or collagen I. Thus, EGF appears to exert a matrix-specific effect on enterocyte migration by modulation of integrin expression and organization.