Induced Hepatocyte Growth Factor Production Research Articles

Cyanidin 3-Glucoside Induces Hepatocyte Growth Factor in Normal Human Dermal Fibroblasts through the Activation of β2-Adrenergic Receptor.

Hepatocyte growth factor (HGF) is expressed in various organs and involved in the fundamental cellular functions such as mitogenic, motogenic, and morphogenic activities. Induction of HGF may be therapeutically useful for controlling organ regeneration, wound healing, and embryogenesis. In this study, we examined the stimulation effect of cyanidin 3-glucoside (C3G), an anthocyanidin derivative, on HGF production in normal human dermal fibroblasts (NHDFs) and the underlying mechanisms. C3G induced HGF production at both mRNA and protein levels in NHDF cells and enhanced the phosphorylation of cAMP-response element-binding protein. We also observed that treatment with C3G increased intracellular cAMP level and promoter activity of cAMP-response element in HEK293 cells expressing β2-adrenergic receptor (β2AR). In contrast, cyanidin, an aglycon of C3G, did not show the activation of β2AR signaling and HGF production. These results indicate that C3G behaves as an agonist for β2AR signaling to activate the protein kinase A pathway and induce the production of HGF.

Induction of Hepatocyte Growth Factor Production in Human Dermal Fibroblasts by Caffeic Acid Derivatives

Hepatocyte growth factor (HGF) has mitogenic, motogenic, and morphogenic activities in epithelial cells. Induction of HGF production may be involved in organ regeneration, wound healing and embryogenesis. In this study, we examined the effects of caffeic acid derivatives including 4,5-di-O-caffeoylquinic acid (1) and acteoside (2) on HGF production in Neonatal Normal Human Dermal Fibroblasts (NHDF). Both 4,5-di-O-caffeoylquinic acid (1) and acteoside (2) significantly induced HGF production dose-dependent manner. To know the important substructure for HGF production activity, we next investigated the effect of the partial structure of these caffeic acid derivatives. From the results, caffeic acid (3) showed strong activity on the promotion of HGF production, while hydroxytyrosol (4) and quinic acid (5) didn't show any activity. Our findings suggest that the caffeoyl moiety of caffeic acid derivatives is essential for accelerated production of HGF. The compound which has the caffeoyl moiety may be useful for the treatment of some intractable organ disease.

Mitogen-activated protein kinases-dependent induction of hepatocyte growth factor production in human dermal fibroblasts by the antibiotic polymyxin B

Hepatocyte growth factor (HGF) stimulates migration and proliferation of keratinocytes and has been suggested to be involved in wound healing. The cationic antibiotic polymyxin B (PMB) is commonly used as a topical antibiotic for wound care. If PMB possesses an HGF-inducing activity, the antibiotic is potentially beneficial for wound healing in addition to minimizing chances of infection. In this study, we found that PMB markedly induced HGF production from various types of cells including human dermal fibroblasts. Its effect was stronger than the effects of epidermal growth factor and cholera toxin and was comparable to the effect of 8-bromo-cAMP. Among the polymyxin family and polymyxin derivatives, colistin was also effective, whereas colistin methanesulfonate had only a marginal effect and PMB nonapeptide was ineffective. The stimulatory effect of PMB was accompanied by upregulation of HGF gene expression. Increase in phosphorylation of extracellular signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) was observed from 0.25h to 6h after the addition of PMB, while increase in phosphorylation of p38 mitogen-activated protein kinase (MAPK) was detected from 24h to 60h after PMB addition. The MAPK/ERK kinase inhibitor PD98059, the JNK inhibitor SP600125 and the p38 MAPK inhibitor SB203580 all potently inhibited PMB-induced HGF production. Lastly, proliferation of human dermal fibroblasts was significantly stimulated by PMB. These results indicate that PMB-induced HGF production and proliferation of human dermal fibroblasts and suggest that activation of MAPKs is involved in the induction of HGF production.

Abstract 1119: Interplay between EGFRvIII and c-Met in glioblastoma multiforme

Abstract Glioblastoma multiforme (GBM) is a highly invasive and lethal brain tumor which is associated with a high recurrence rate after surgery and an increased resistance to irradiation and chemotherapies. Consequently, patients suffering from GBM have a poor prognosis and a high mortality rate with an average life expectancy of less than 15 months. Key signaling components, especially receptor tyrosine kinases (RTKs), are aberrantly activated in GBM. The most frequent is the epidermal growth factor receptor (EGFR) and here the most commonly activated form, EGFRvIII, augments GBM invasiveness, promotes therapy resistance and connotes poor prognosis. There are five EGFR approved inhibitors and interestingly clinical studies have indicated that targeting the activity of the EGFR in association with conventional GBM therapies does little to inhibit tumor growth. The underlying mechanistic reasoning for this poor response are not understood and may reflect EGFR-induced trans-activation of other RTKs such as the hepatocyte growth factor receptor (c-Met), or uncoupling of EGFR signaling from its downstream mediators. Several studies have indicated that EGFR can trans-activate c-Met and consequently the dual targeting of both EGFR and c-Met significantly decreases the growth of EGFRvIII expressing tumor xenografts, indicating that inhibiting both EGFR and c-Met activity may prove beneficial in GBM therapy. Currently, the only known ligand for c-Met is the hepatocyte growth factor (HGF). Thus we hypothesize that EGFR induced HGF production is critical for the increased tumorgenicity observed in EGFRvIII expressing GBM cells. Using GBM cell lines we show that c-Met activation is increased in GBM cells that both stably and transiently express EGFRvIII. Furthermore, conditioned media taken from GBM cells expressing EGFRvIII can activate c-Met signaling in GBM cells that lack EGFRvIII. In both instances we see that the kinase activity of the EGFRvIII partially contributes to the production of HGF and the activation of c-Met in GBM cells. Aberrant c-Jun terminal kinase signaling (JNK) can be detected in the majority of patient GBMs. Using GBM cells stably lacking JNK2α2 we identify JNK2α2 signaling as a potential mechanism behind EGFRvIII activation of c-Met via the production of HGF in EGFRvIII GBM expressing cells. Taken together our data describes a novel role for JNK2α2 in mediating GBM tumorgenicity through the regulation of HGF production and the subsequent activation of c-Met signaling in GBM. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1119. doi:10.1158/1538-7445.AM2011-1119

Enhanced c-Met activity promotes G-CSF–induced mobilization of hematopoietic progenitor cells via ROS signaling

AbstractMechanisms governing stress-induced hematopoietic progenitor cell mobilization are not fully deciphered. We report that during granulocyte colony-stimulating factor–induced mobilization c-Met expression and signaling are up-regulated on immature bone marrow progenitors. Interestingly, stromal cell–derived factor 1/CXC chemokine receptor-4 signaling induced hepatocyte growth factor production and c-Met activation. We found that c-Met inhibition reduced mobilization of both immature progenitors and the more primitive Sca-1+/c-Kit+/Lin− cells and interfered with their enhanced chemotactic migration to stromal cell–derived factor 1. c-Met activation resulted in cellular accumulation of reactive oxygen species by mammalian target of rapamycin inhibition of Forkhead Box, subclass O3a. Blockage of mammalian target of rapamycin inhibition or reactive oxygen species signaling impaired c-Met–mediated mobilization. Our data show dynamic c-Met expression and function in the bone marrow and show that enhanced c-Met signaling is crucial to facilitate stress-induced mobilization of progenitor cells as part of host defense and repair mechanisms.

MCP-1 Antibody Treatment Enhances Damage and Impedes Repair of the Alveolar Epithelium in Influenza Pneumonitis

Recent studies have demonstrated an essential role of alveolar macrophages during influenza virus infection. Enhanced mortalities were observed in macrophage-depleted mice and pigs after influenza virus infection, but the basis for the enhanced pathogenesis is unclear. This study revealed that blocking macrophage recruitment into the lungs in a mouse model of influenza pneumonitis resulted in enhanced alveolar epithelial damage and apoptosis, as evaluated by histopathology, immunohistochemistry, Western blot, RT-PCR, and TUNEL assays. Abrogation of macrophage recruitment was achieved by treatment with monoclonal antibody against monocyte chemoattractant protein-1 (MCP-1) after sub-lethal challenge with mouse-adapted human influenza A/Aichi/2/68 virus. Interestingly, elevated levels of hepatocyte growth factor (HGF), a mitogen for alveolar epithelium, were detected in bronchoalveolar lavage samples and in lung homogenates of control untreated and nonimmune immunoglobulin (Ig)G-treated mice after infection compared with anti-MCP-1-treated infected mice. The lungs of control animals also displayed strongly positive HGF staining in alveolar macrophages as well as alveolar epithelial cell hyperplasia. Co-culture of influenza virus-infected alveolar epithelial cells with freshly isolated alveolar macrophages induced HGF production and phagocytic activity of macrophages. Recombinant HGF added to mouse lung explants after influenza virus infection resulted in enhanced BrdU labeling of alveolar type II epithelial cells, indicating their proliferation, in contrast with anti-HGF treatment showing significantly reduced epithelial regeneration. Our data indicate that inhibition of macrophage recruitment augmented alveolar epithelial damage and apoptosis during influenza pneumonitis, and that HGF produced by macrophages in response to influenza participates in the resolution of alveolar epithelium.

Induction of hepatocyte growth factor production in human dermal fibroblasts and their proliferation by the extract of bitter melon pulp

Hepatocyte growth factor (HGF) is useful as a potential therapeutic agent for hepatic and renal fibrosis and cardiovascular diseases through inducing proliferation of epithelial and endothelial cells. HGF inducers may also be useful as therapeutic agents for these diseases. However, there have been no reports on induction of HGF production by plant extracts or juices. An extract of bitter melon ( Momordica charantia L.) pulp markedly induced HGF production. There was a time lag of 72 h before induction of HGF production after the extract addition. Its stimulatory effect was accompanied by upregulation of HGF gene expression. Increases in mitogen-activated protein kinases (MAPKs) were observed from 72 h after the extract addition. Inhibitors of MAPKs suppressed the extract-induced HGF production. The extract also stimulated cell proliferation. Both activities for induction of HGF production and cell proliferation were eluted together in a single peak with 14,000 Da on gel filtration. The results indicate that bitter melon pulp extract induced HGF production and cell proliferation of human dermal fibroblasts and suggest that activation of MAPKs is involved in the HGF induction. Our findings suggest potential usefulness of the extract for tissue regeneration and provide an insight into the molecular mechanism underlying the wound-healing property of bitter melon.

Induction of hepatocyte growth factor expression by maleic acid in human fibroblasts through MAPK activation

Carboxylic acids have various biological activities and play critical roles in cellular metabolic pathways such as the tricarboxylic acid (TCA) cycle. It has been shown that some carboxylic acids induce cell proliferation and production of cytokines or growth factors. However, there have been no reports on effects of carboxylic acids on hepatocyte growth factor (HGF) expression. In this study, we found that only maleic acid among various carboxylic acids examined markedly induced HGF production from human dermal fibroblasts. Maleic acid also induced HGF production from human lung fibroblasts and neuroblastoma cells. The stimulatory effect was accompanied by upregulation of HGF gene expression. Increase in phosphorylation of extracellular signal-regulated protein kinase (ERK) and c-Jun N-terminal kinase (JNK) but not in phosphorylation of p38 was observed from 6 h and up to 24 h after maleic acid addition. The ERK kinase inhibitor PD98059 and the JNK inhibitor SP600125 potently inhibited maleic acid-induced HGF production, while the p38 inhibitor SB203580 did not significantly inhibit the production. The protein synthesis inhibitor cycloheximide completely inhibited upregulation of HGF mRNA induced by maleic acid but superinduced HGF mRNA expression upregulated by 12-O-tetradecanoylphorbol 13-acetate (TPA). These results suggest that maleic acid indirectly induced HGF expression from human dermal fibroblasts through activation of ERK and JNK and that de novo protein synthesis is required for maleic acid-induced upregulation of HGF mRNA.

Hepatocyte Growth Factor Establishes Autocrine and Paracrine Feedback Loops for the Protection of Skin Cells after UV Irradiation

Hepatocyte growth factor (HGF) is a multifunctional cytokine, which, among various other activities, acts as a growth factor for melanocytes and has recently been implicated in the pathogenesis of malignant melanoma. In the skin, the main source for HGF is dermal fibroblasts (FB). Here, we have investigated the regulation of HGF production and secretion by cytokines derived from UV-irradiated keratinocytes (KC) and by direct UV irradiation. We demonstrate that supernatants of ultraviolet (UV)B-irradiated KC strongly induce HGF production in FB, and that this effect was mediated primarily by IL-1alpha. Direct irradiation of FB with UVB had no effect on HGF expression. In contrast, irradiation with UVA1 strongly upregulated HGF mRNA production and secretion of the functional protein. Addition of neutralizing anti-HGF antibodies after UVA1 irradiation, as well as transfection of FB with HGF small-interfering RNA (siRNA); which completely abrogated HGF secretion led to a dramatic rise of FB apoptosis demonstrating that autocrine HGF efficiently protected FB from UVA1-induced apoptosis. Our data suggest that upregulation of HGF plays a role in skin homeostasis after UV irradiation. However, a negative side effect of UV-induced HGF secretion by dermal FB might represent a decisive factor for induction and/or progression of melanoma.

Platelet-released growth factors enhance the secretion of hyaluronic acid and induce hepatocyte growth factor production by synovial fibroblasts from arthritic patients

Autologous platelet-secreted growth factors (GFs) may have therapeutic effects in osteoarthritis (OA) capsular joints via multiple mechanisms. Our aim was to examine the effect of a platelet-derived preparation rich in growth factors (PRGFs) in OA synovial cell biology. Synovial cells were isolated from 10 osteoarthritic patients and cultured in serum-free media (basal conditions) and exposed to either a platelet-poor preparation or PRGF for 72 h. Cells activated with interleukin-1beta (IL-1beta) for 48 h were also exposed to PRGF. Changes in several events relevant to joint homeostasis including (i) hyaluronic acid (HA) secretion, (ii) the balance between metalloproteinase-1, -3 and -13 (MMP-1, MMP-3 and MMP-13) and tissue inhibitor-1 (TIMP-1) and (iii) the secretion of transforming growth factor-beta1(TGF-beta1), vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF), were all assessed. PRGF significantly enhanced HA secretion compared with platelet-poor preparations, P < 0.05; at the same time release of TIMP-1, MMP-1, MMP-3 and MMP-13 were not affected. An increased HGF production was observed (P < 0.05) but VEGF and TGF-beta1 levels remained unchanged. PRGF significantly enhanced the secretion of HA induced by IL-1beta activation, P < 0.05, but it did not modify the IL-1beta-induced rise in MMP-1, MMP-3 and VEGF. In contrast, PRGF-induced HGF production was abolished by the presence of IL-1beta during PRGF treatment, P < 0.05. Intra-articular administration of PRGF might be beneficial in restoring HA concentration and switching angiogenesis to a more balanced status but does not halt the effects of IL-1beta on synovial cells.

Inhibition of Hepatocyte Growth Factor Production in Human Fibroblasts by Ursodeoxycholic Acid

Hepatocyte growth factor (HGF) stimulates the proliferation of hepatocytes and biliary epithelial cells and protects hepatocytes from apoptosis induced by various stimuli. In view of HGF induction by interferons, substances used for the treatment of chronic hepatitis C, this study was conducted to determine whether ursodeoxycholic acid (UDCA), which is widely used for the treatment of cholestatic liver diseases, modulates HGF production. UDCA did not induce HGF production in human dermal fibroblasts, but it potently inhibited phorbol-12-myristate-13-acetate (PMA)- and cholera-toxin-induced HGF production without affecting cell viability. The inhibitory effects of UDCA were as potent as those of transforming growth factor-beta1 and dexamethasone. Up-regulations of HGF gene expression induced by PMA and cholera toxin were also inhibited by UDCA. Moreover, UDCA dose-dependently inhibited high constitutive HGF production by MRC-5 cells without decreasing cell viability. Deoxycholate, chenodeoxycholate, taurochenodeoxycholate and glycochenodeoxycholate also inhibited cholera-toxin-induced HGF production at non-cytotoxic doses. UDCA, however, had no apparent effect on PMA-induced phosphorylation of mitogen-activated protein kinase, which is crucial for HGF induction by PMA. These results indicate that non-cytotoxic doses of UDCA inhibited constitutive and induced HGF production and suggest that UDCA supplemented with HGF or HGF inducers could have a more potential therapeutic effect.

Synergistic induction of hepatocyte growth factor in human skin fibroblasts by the inflammatory cytokines interleukin-1 and interferon-γ

Hepatocyte growth factor (HGF) is one of the vital factors for wound healing. HGF expression markedly increases in wounded skin and is mainly localized in dermal fibroblasts. HGF expression level in human dermal fibroblasts in vitro, however, is low and thus may be stimulated by some factors in the process of wound healing. Candidates of the factors are inflammatory cytokines released by polymorphonuclear and mononuclear cells infiltrating the wounded area, but HGF production in human dermal fibroblasts is only slightly induced by interleukin (IL)-1, tumor necrosis factor (TNF)-α or interferon (IFN)-γ. We here report that a combination of IL-1β and IFN-γ or a combination of TNF-α and IFN-γ very markedly induced HGF production. The synergistic effect of the former was more marked than that of the latter. Synergistic effects of IL-1β and IFN-γ were observed at more than 10 pg/ml and 10 IU/ml, respectively, and were detectable as early as 12 h after addition. Neither IFN-α nor IFN-β was able to replace IFN-γ. HGF mRNA expression was also synergistically upregulated by IL-1β and IFN-γ. IL-1β plus IFN-γ-induced synergistic production of HGF was potently inhibited by treatment of cells with the extracellular signal-regulated kinase (ERK) kinase inhibitor PD98059 and the p38 inhibitor SB203580 but not by the c-Jun N-terminal kinase (JNK) inhibitor SP600125. Taken together, our results indicate that a combination of IL-1β and IFN-γ synergistically induced HGF production in human dermal fibroblasts and suggest that activation of ERK and p38 but not of JNK is involved in the synergistic effect.

Modulation of hepatocyte growth factor induction in human skin fibroblasts by retinoic acid

Topical treatment of skin with all- trans-retinoic acid (ATRA), the major biologically active form of vitamin A, results in hyperproliferation of basal keratinocytes, leading to an accelerated turnover of epidermis cells and thickening of the epidermis, probably via induction of production of paracrine growth factors for keratinocytes in epidermal suprabasal keratinocytes and/or dermal fibroblasts. Since hepatocyte growth factor (HGF) is a factor mitogenic to epidermal keratinocytes secreted from dermal fibroblasts, the effect of ATRA on basal and induced HGF production in human dermal fibroblasts in culture was examined. ATRA alone did not induce HGF production, but it significantly enhanced HGF production induced by the cAMP-elevating agent cholera toxin or the membrane-permeable cAMP analog 8-bromo-cAMP. Cholera toxin-induced activation of cAMP responsive element (CRE)-binding protein (CREB) was enhanced by pretreating cells with ATRA for 24 h. In contrast, HGF production induced by epidermal growth factor (EGF) or phorbol 12-myristate 13-acetate (PMA) was potently inhibited by ATRA. These modulatory effects of ATRA were different from the effects of transforming growth factor-β1 (TGF-β) and dexamethasone, both of which inhibited HGF production induced by all of the four inducers. Up-regulation of HGF gene expression by cholera toxin and EGF was also enhanced and inhibited, respectively, by ATRA. Both 9- cis-retinoic acid (9- cis-RA) and 13- cis-retinoic acid (13- cis-RA), which are stereo-isomers of ATRA, showed a modulatory effect on HGF induction similar to that of ATRA. These results suggest that ATRA augments the induction of HGF production caused by increased intracellular cAMP.

Expression of Hepatocyte Growth Factor Is Induced by the Interaction between Human Mesangial Cells and Monocytes

Background: In pathological states various cytokines are produced by mesangial cells (MC) and contribute to disease progression. It is likely that interactions between monocytes and MC partially regulate these cytokines, including hepatocyte growth factor (HGF). Because HGF might have a potent therapeutic effect on the kidney, it is believed to play a critical role in the pathogenesis and development of glomerulonephritis. However, there is little knowledge about HGF production by MC or infiltrated monocytes in glomerulonephritis. Methods: To investigate HGF expression in pathological states, we cultured human MC (hMC) with a human monocytoid cell line and assessed HGF mRNA expression and protein production. Next, we performed immunohistochemical staining to explore which types of cell in the co-culture system expressed HGF. Because several humoral factors that can induce HGF production have been reported, we also performed noncontact co-culture to explore the contribution of humoral factors. Results: The HGF concentration of the co-culture system showed a time-dependent increase, and was fourfold greater than that of hMC alone. Expression of HGF mRNA was also increased. Both THP-1 cells and hMC in the co-culture demonstrated staining of HGF. The HGF concentration in the noncontact co-cultures was smaller than in the ordinary ones, but was greater than hMC alone. Conclusion: Direct cell-to-cell interaction between hMC and monocytes induced HGF production of both types of cells, indicating that local HGF production induced by cell-to-cell interaction plays an important role in the pathogenesis of glomerulonephritis. While direct cell-to-cell contact was important for HGF production, it is considered that some humoral factors might contribute.

Induction of Hepatocyte Growth Factor in Stromal Cells by Tumor-Derived Basic Fibroblast Growth Factor Enhances Growth and Invasion of Endometrial Cancer

Tumor progression is often regulated through interactions between carcinoma cells and host stromal cells. In this study of endometrial cancer, we investigated one mechanism potentially involved in hepatocyte growth factor (HGF)-mediated cancer-stromal interactions. Endometrial cancer cells (HEC-1 and ISHIKAWA) expressed the c-met receptor, but HGF did not. HGF, however, did stimulate the proliferation and invasion of these cells. The HGF gene was expressed in stromal cells, which had been separated from primary cultures of endometrial cancers, 6.4 times more than in isolated normal endometrial stromal cells. Immunohistochemical staining revealed immunoreactive HGF in cancer stromal cells, the staining intensity being more pronounced in cancer tissue than in normal endometrium. The conditioned medium from normal epithelial cells and cancer cell lines induced HGF production in normal stromal cells. We identified basic fibroblast growth factor as an HGF inducer derived from endometrial cancer cell lines. Basic fibroblast growth factor derived from tumor cells may induce HGF in endometrial stromal cells, whereas stromal cell-derived HGF leads to the invasive growth of carcinoma cells. These interactions, mediated by HGF and HGF inducers, may play a significant role in the progression of endometrial cancer.

Induction of hepatocyte growth factor in stromal cells by tumor-derived basic fibroblast growth factor enhances growth and invasion of endometrial cancer.

Tumor progression is often regulated through interactions between carcinoma cells and host stromal cells. In this study of endometrial cancer, we investigated one mechanism potentially involved in hepatocyte growth factor (HGF)-mediated cancer-stromal interactions. Endometrial cancer cells (HEC-1 and ISHIKAWA) expressed the c-met receptor, but HGF did not. HGF, however, did stimulate the proliferation and invasion of these cells. The HGF gene was expressed in stromal cells, which had been separated from primary cultures of endometrial cancers, 6.4 times more than in isolated normal endometrial stromal cells. Immunohistochemical staining revealed immunoreactive HGF in cancer stromal cells, the staining intensity being more pronounced in cancer tissue than in normal endometrium. The conditioned medium from normal epithelial cells and cancer cell lines induced HGF production in normal stromal cells. We identified basic fibroblast growth factor as an HGF inducer derived from endometrial cancer cell lines. Basic fibroblast growth factor derived from tumor cells may induce HGF in endometrial stromal cells, whereas stromal cell-derived HGF leads to the invasive growth of carcinoma cells. These interactions, mediated by HGF and HGF inducers, may play a significant role in the progression of endometrial cancer.

Induction of hepatocyte growth factor (HGF) in rat microglial cells by prostaglandin E(2).

Hepatocyte growth factor (HGF) is a multifunctional protein that exerts trophic effects on neural cells. HGF is expressed in normal brains and increased after brain injury. Recent studies suggest that neurons and astrocytes are the main producers of HGF in the brain. Here we report that microglia also produce HGF both in vitro and in vivo. Treatment of cultured microglia with prostaglandin E(2) (PGE(2)), one of the major inflammatory mediators in the brain, induced significant production of HGF, and this induction was suppressed by pretreatment with the adenylate cyclase inhibitor SQ22536, suggesting that the induction of HGF by PGE(2) in microglia proceeds via a cAMP-mediated pathway. We further investigated whether microglia also produce HGF in vivo under the pathological condition of cerebral ischemia. We found that HGF expression was increased after permanent occlusion of the middle cerebral artery (MCA), and double immunohistochemical staining revealed that the most of HGF-positive cells were microglia. PGE(2) level was increased 8 hr after start of MCA occlusion, and this enhancement is in parallel with the increase in HGF expression, suggesting that PGE(2) not only may induce HGF production in microglia in vitro but may also be an inducer in vivo.