Human serum does contain a high molecular weight hepatocyte growth factor: studies pre- and post-hepatic resection

Prediction of Recurrence after HCC Resection

In trying to clarify the high recurrence rate after removal of small hepatocellular carcinoma (HCC), we assessed the postoperative evolution of minute hepatic Lipiodol deposits which had been diagnosed as artifacts on the preoperative Lipiodol-CT. Of 27 patients with solitary HCC less than 5 cm in diameter, 14 had such Lipiodol deposits in the preoperative CT and 9 of them (64%) developed recurrent tumors. On the other hand, 6 of the 13 patients without deposits (46%) suffered recurrence, but in 5 of these 6 patients the HCC was metachronous multicentric. The cumulative survival rate of the non-deposit group was better than that of the deposit group (p < 0.1). The present study suggested that, even in patients with small HCC, minute concomitant tumors invisible by conventional imaging techniques may exist at the time of surgery. Some of these lesions without sufficient tumor vasculature showing a hypervascular blush on angiography appear to retain small, vague Lipiodol deposits.

Significance of serum hepatocyte growth factor levels in patients with hepatocellular carcinoma undergoing hepatic resection

BACKGROUND

Hepatocyte growth factor (HGF) is a potent hepatocyte mitogen and may stimulate the proliferation and invasiveness of human hepatocellular carcinoma (HCC) cells through the c-met receptor. This study evaluates the significance of serum HGF levels in patients undergoing HCC resection.

STUDY DESIGN

The peripheral and portal sera and HCC and non-tumorous tissues of 40 HCC patients, with tumor TNM stage I (n=12), II (n=17), and III (n=11) diseases, who underwent hepatic resection were prospectively collected. Serum HGF levels were determined by enzyme-linked immunosorbent assay. The c-met protein expressions were examined by immunohistochemistry. Median follow-up time was 69 months.

RESULTS

The prehepatectomy portal HGF levels (median, 622pg/mL) were significantly higher than peripheral HGF levels (564pg/mL) (P=0.026). The posthepatectomy portal HGF levels (699pg/mL) were significantly higher than prehepatectomy portal HGF levels (P<0.001). C-met expression was detected in 87.5% HCC and in 85.0% non-tumorous liver tissues. By Cox multivariate analysis, posthepatectomy portal HGF level >699pg/mL (P<0.001), multiple tumors (P=0.042), and TNM stages II (P=0.019) and III (P=0.009) were independent factors related with survival. Patients with a posthepatectomy portal HCG level >699pg/mL and with a positive c-met expression in HCC tissue have the worst survival.

CONCLUSIONS

In HCC patients, high peripheral and portal HGF serum levels related with poor prognosis after hepatic resection. Hepatocyte growth factor and c-met receptor can be targets of future HCC postoperative treatment.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

Growth factors in inflammatory bowel disease

The pathogenesis of both ulcerative colitis and Crohn's disease is unknown but these forms of inflammatory bowel disease (IBD) may be associated with an inability of the intestinal mucosa to protect itself from luminal challenges and/or inappropriate repair following intestinal injury. Numerous cell populations regulate these broad processes through the expression of a complex array of peptides and other agents. Growth factors can be distinguished by their actions regulating cell proliferation. These factors also mediate processes such as extracellular matrix formation, cell migration and differentiation, immune regulation, and tissue remodeling. Several families of growth factors may play an important role in IBD including: epidermal growth factor family (EGF) [transforming growth factor alpha (TGF alpha), EGF itself, and others], the transforming growth factor beta (TGF beta) super family, insulin-like growth factors (IGF), fibroblast growth factors (FGF), hepatocyte growth factor (HGF), trefoil factors, platelet-derived growth factor (PDGF), vascular endothelial growth factor (VEGF) and others. Collectively these families may determine susceptibility of IBD mucosa to injury and facilitate tissue repair.

Active form of human hepatocyte growth factor is excreted into bile after hepatobiliary resection

BACKGROUND/AIMS

We have shown that hepatocyte growth factor is excreted into bile after hepatectomy in patients with biliary tract carcinoma. However, it is not certain whether hepatocyte growth factor in bile is an active molecule or degradation products.

METHODS

Bile was obtained from five patients after hepatobiliary resection. Bile hepatocyte growth factor was purified on a heparin-Sepharose column and subjected to Western blotting. It was also tested for growth-stimulating activity with rat primary cultured hepatocytes. Biles from 50 patients who underwent various types of hepatobiliary resections were examined with respect to hepatocyte growth factor by an enzyme-linked immunosorbent assay.

RESULTS

Upon Western blotting following nonreducing electrophoresis, the purified bile hepatocyte growth factor showed an 85 kDa peptide corresponding to native hepatocyte growth factor. Under reducing conditions, it showed bands of a-subunit at 69 kDa and beta-subunit at 34 kDa with corresponding monoclonal antibodies. The purified bile hepatocyte growth factor stimulated the [3H]thymidine incorporation into primary cultured hepatocytes with a specific activity comparable to recombinant human hepatocyte growth factor. It was observed that the levels of bile hepatocyte growth factor increased after the various types of hepatobiliary resections, including bile duct resection without hepatectomy.

CONCLUSIONS

The human bile obtained after hepatobiliary resection contains active hepatocyte growth factor that can stimulate hepatocyte growth. Bile hepatocyte growth factor increased not only in hepatectomy but in bile duct resection. These results suggest that the biliary tract system may play an important role in the production of bile hepatocyte growth factor.

Treatment with a novel lipid A analogue, FS-112, and partial hepatectomy causes submassive liver necrosis and impaired liver regeneration in mice

A novel experimental model of submassive liver necrosis with impaired regeneration has been established. A novel lipid A analogue, FS-112, was injected intravenously into male BALB/c mice, followed 2 days later by a 70% partial hepatectomy. Over the next 9 days, mice became severely jaundiced, with a peak total bilirubin (TBil) concentration of (mean +/- s.d.) 12.9 +/- 2.1 mg/dL 7 days postoperatively. In contrast, the TBil concentration in vehicle-treated mice remained less than 2 mg/dL. Significant elevations of L-alanine:2-oxoglutarate aminotransferase (ALT) were also observed 3-7 days after the operation in mice pretreated with FS-112, compared with mice pretreated with the vehicle. Submassive liver necrosis was observed with extensive mononuclear cell infiltration in mice treated with FS-112 and subjected to partial hepatectomy. Furthermore, both the BrdU and the proliferating cell nuclear antigen (PCNA) labelling index (LI) 1 day following partial hepatectomy in mice pretreated with FS-112 (8.6 +/- 4.3 and 7.9 +/- 4.2%, respectively) were significantly lower than levels in vehicle-treated mice (25.8 +/- 3.8 and 26.5 +/- 10.5%, respectively). The time course of changes in the BrdU LI in liver specimens from mice treated with both FS-112 and partial hepatectomy did not increase, even 3, 5, and 7 days postoperatively. Excellent liver regeneration with a PCNA LI 10-fold higher than the resting level was observed in mice treated with D-galactosamine hydrochloride. These results strongly suggest that this animal model of submassive liver necrosis may be suitable for clarifying the mechanisms of impaired liver cell regeneration often seen in fulminant hepatitis.

Expression of immunoreactive human hepatocyte growth factor in human esophageal squamous cell carcinomas

Hepatocyte growth factor (HGF) is a potent mitogen for epithelial cells that promotes cell motility and invasiveness. In this study, we report that the human esophageal squamous cell carcinoma (SCC) shows a significant elevation of HGF concentration (600 +/- 416 ng/100 mg protein), compared to normal mucosa (80 +/- 183 ng/100 mg protein) (P < 0.01). An association could be established between levels of HGF and decreasing differentiation of 37 SCCs. The 2-year crude survival rates were 51.1% and 68.4% at high and low HGF concentrations, respectively. The results indicate that HGF is significantly increased in human esophageal SCCs, especially of poorly differentiated type. HGF might thus be useful as a biological biomarker for characterization of human esophageal SCCs.

Effects of albumin-bilirubin complexes with syngeneic or allogeneic albumin on DNA and protein synthesis in liver and spleen of partially hepatectomized rats

The effects of non-covalently bound complexes of allogeneic or syngeneic albumin with bilirubin and of albumin alone on DNA and protein synthesis in rat liver and spleen cells after partial hepatectomy were studied. The assay procedure was based on different intravenous doses of these compounds in rats after partial hepatectomy. The allogeneic albumin-bilirubin complex (at protein doses of 0.9 and 90 micrograms/100 g body weight) stimulated DNA and protein synthesis in liver cells irrespective of the dose. At a dose of 0.9 micrograms the syngeneic albumin-bilirubin complex enhanced DNA synthesis insignificantly and produced no effect on protein synthesis, while at a dose of 90 micrograms, both DNA and protein synthesis were considerably increased. Allogeneic or syngeneic albumin at the above doses stimulated only protein, not DNA, synthesis in the liver, while the highest stimulation was at 90 micrograms allogeneic albumin. It was found also that partial hepatectomy decreased DNA and protein synthesis in spleen cells. Albumin-bilirubin complex with allogeneic or syngeneic albumin and albumin alone either significantly enhanced DNA and protein synthesis in the spleen, compared to controls, or only restored synthesis to control levels. Thus DNA and protein synthesis in the regenerating liver and spleen was significantly enhanced after the injection of small doses of the albumin-bilirubin complex, indicating the existence of small amounts of a similar endogenous complex in the blood stream.

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.

Immunohistochemical detection of hepatocyte growth factor/scatter factor in human cancerous and inflammatory lesions of various organs

Hepatocyte growth factor (HGF)/scatter factor (SF) is a multifunctional factor considered to be potentially involved in tissue regeneration, wound healing, embryogenesis, angiogenesis and cancer invasion. Here we examined immunohistochemically the distribution of HGF/SF in human tissues, including cancerous and inflammatory tissues, using anti-HGF antibody. HGF/SF accumulation was clearly detected in the extracellular matrix, particularly along the basement membrane, in cancerous and inflammatory tissues, but only a little was detected in normal tissues. HGF/SF is well known to have a strong affinity for heparin in vitro, and from the results of our immunohistochemical assay, we considered that HGF/SF was bound to heparin or heparan sulfate of the extracellular matrix and basement membrane. HGF/SF was well localized in cancerous and inflammatory lesions of human lung, liver and pancreas, and in apparently normal tissues of kidney, adrenal gland and pancreas obtained at autopsy. In lung, HGF/SF was localized along the basement membranes of cancer cell nests, in the extracellular matrix of the cancer cell surface, cancer stroma and tissues invaded by cancer, and the basement membranes of bronchial epithelium and capillary vessels in inflammatory stroma. Since HGF/SF makes some cancer cells more invasive in vitro, the accumulation of HGF/SF in cancerous tissue suggests that the invasiveness of some cancer cells may be increased by HGF/SF in vivo.

Intrahepatic distant metastasis and metachronous multicentric occurrence in solitary hepatocellular carcinoma of less than five centimeters in diameter

During the 7 years from 1984 to 1990, 36 patients underwent liver resection for solitary hepatocellular carcinoma (HCC) measuring less than 5 cm in diameter, with no intrahepatic vascular invasion on imaging diagnoses and no macroscopic infiltration into the tumor capsule or surrounding tissues. Although HCC is less likely to cause intrahepatic adjacent metastasis to the cut liver surface, an analysis revealed the possibility of intrahepatic distant metastasis and metachronous multicentric occurrences, even after complete removal of the primary tumor. The 5-year cumulative survival rate was 53%, while the 5-year cumulative recurrence-free survival rate was 19%. Of the 36 patients, 18 (50%) had suffered a recurrence by April, 1992, one with extrahepatic metastasis. Recurrence of intrahepatic metastasis was multifocal in 5 patients, single and adjacent in 1, and single (or a few) and distant in 11. Multifocal recurrence was observed within 1 year after liver resection. The sole single and adjacent metastatic case occurred in one of eight patients in the recurrent group in whom distance of the surgical margin was less than 1 cm [TW(+)]. Multicentric occurrence was found in 6 of 13 patients (46%) whose recurrent tumors were examined histologically, and all belonged to the "single (or a few) and distant" type of recurrence. In this report, we also present two typical cases of metastasis, one being multifocal metastasis occurring within 3 months after liver resection and the other being intrahepatic metastasis occurring after a 4-year-dormant state, to demonstrate the complicated nature of the intrahepatic metastatic pattern.

A possible prototype of multifocal recurrence after liver resection of hepatocellular carcinoma: report of a case

The clinical course of a 68-year-old male with HCC is herein reported. In addition to two tumor nodules detected preoperatively, the resected surgical specimen disclosed macroscopically invisible tumor-cell clusters as well as intrahepatic metastatic foci. These clusters had no clear border and were more basophilic with small-sized cells, high cellularity, and a higher nuclear/cytoplasm ratio, which was suggestive of early HCC with a form of de novo occurrence. The postoperative course, characterized by an early recurrence of small nodules in the remnant liver suggested the presence of a similar invisible tumor mixture at the time of operation. This case can thus be regarded as a prototype of the multifocal recurrence type.

Hepatocyte growth factor stimulates phosphoinositide hydrolysis and mitogenesis in cultured renal epithelial cells

Hepatocyte growth factor (HGF), a novel heparin-binding peptide growth factor of MW 97-kDa, is a potent mitogen for parenchymal hepatocytes. HGF is present in normal serum and increases following liver injury or partial hepatectomy. In addition to liver, HGF mRNA has been detected in kidney. In cultured rabbit proximal tubule cells, recombinant human HGF (10(-10) M) increased DNA synthesis, measured as [3H] thymidine incorporation, from 1345 +/- 213 to 2931 +/- 636 cpm/10(6) cells; n = 9; p < 0.005). HGF was found to exert mitogenic effects at lower concentrations than epidermal growth factor (EGF), with half maximal effects seen at 6 x 10(-11) M compared to 7 x 10(-10) M for EGF. HGF was additive with EGF in stimulating [3H] thymidine incorporation. In addition to rabbit proximal tubule cells, HGF increased proliferation in a cultured mouse proximal tubule cell line, MCT, and in rat glomerular epithelial cells. In contrast, HGF did not stimulate proliferation of either rat mesangial cells or a rat aortic smooth muscle cell line, A7r5. The HGF receptor is the product of the c-met proto-oncogene. C-met mRNA was detected in total kidney and in cultured proximal tubule cells but was not detected in cultured mesangial cells. In contrast, HGF mRNA was detected in mesangial cells but not in cultured proximal tubule cells. Preincubation of rabbit proximal tubule cells with the tyrosine kinase inhibitor, genistein (50 microM), prevented HGF-stimulation of [3H] thymidine incorporation. In LiCl pretreated rabbit proximal tubule cells loaded with [3H] myoinositol, HGF increased total inositol phosphate release, measured by anion exchange chromatography (control: 2181 +/- 414 vs HGF: 2609 +/- 478 cpm/10(6) cells; n = 6; p < 0.05). Although genistein did not affect baseline phosphoinositide hydrolysis, it inhibited the HGF stimulation. Thus, HGF is mitogenic for cultured proximal tubule cells as well as glomerular epithelial cells. Inhibition of proliferation and PI turnover by genistein suggests that HGF's actions are mediated in part by tyrosine kinase activity. In mammalian kidney, HGF released from mesangial cells may serve as a paracrine activator of the adjacent epithelial cells.

Effect of in vivo administration of an antibody to epidermal growth factor on the rapid increase in DNA synthesis induced by partial hepatectomy in the rat

Recent reports indicate that transforming growth factor alpha (TGF-alpha) is produced within the liver and acts as the natural ligand of the epidermal growth factor (EGF) receptor causing the EGF receptor down regulation and the hepatocyte proliferation observed after partial hepatectomy. The reported phenomenon that an antibody to EGF inhibits the regenerative response to partial hepatectomy was therefore re-investigated. The IgG fraction of an anti-rat EGF antibody was injected intravenously at the time of partial hepatectomy, and its effects on regenerative DNA synthesis were compared with those of non-immune IgG. Injection of IgG reduced the DNA synthetic response to partial hepatectomy, assessed 24 hours after resection by 3H-thymidine incorporation, but the effects of normal and anti-EGF IgG were not statistically different, despite the presence of excess anti-EGF IgG in the circulation throughout the experimental period. However, anti-EGF IgG could completely block the proliferative response of hepatocytes in culture to EGF. These results support the suggestion that EGF is not the major mediator of hepatocyte DNA synthesis in the early stages of liver regeneration (less than 24 hours).

Comparative effects of epidermal growth factor, an insulin-glucagon combination, and a hepatocyte growth factor preparation on epidermal growth factor receptors

We investigated the changes in cell surface epidermal growth factor (EGF) receptors in the liver after partial hepatectomy, and in primary adult rat hepatocyte cultures following stimulation with either EGF, or a preparation of hepatocyte growth factor, or an insulin-glucagon combination. We confirmed a reduction in EGF receptors on hepatocytes after partial hepatectomy and a rapid down-regulation of EGF receptors on normal hepatocytes in vitro following exposure to EGF. Insulin and glucagon and hepatocyte growth factor, whilst initiating hepatocyte DNA synthesis, had only slight effects on their EGF binding capacity and EGF-receptor affinity. These results indicate that changes in cell membranes early in proliferation have only non-specific effects on EGF receptors, and, therefore, support the role of ligand binding to the EGF receptor as an important component of hepatocyte proliferation in vivo.

Hepatocyte growth factor: molecular structure and implications for a central role in liver regeneration

Hepatocyte growth factor (HGF) is a most potent factor for mature parenchymal hepatocytes in primary culture and may act as a trigger for liver regeneration. We purified HGF from rat platelets to homogeneity and cloned both human and rat HGF cDNA. HGF is a heterodimer molecule composed of the 69 kDa alpha-subunit and the 34 kDa beta-subunit. HGF has no amino acid sequence homology with other known peptide growth factors and possesses the highest potential among known growth factors to stimulate proliferation of hepatocytes in primary culture. HGF is derived from a single chain precursor of 728 amino acid residues and the precursor is proteolytically processed to form a two-chain mature HGF. The alpha-subunit of HGF contains 4 kringle structures and HGF has a homology (38%) with plasmin. Biologically active recombinant human HGF could be expressed from COS-1 cells and CHO cells transfected with cloned cDNA. HGF activity and the HGF mRNA level are markedly increased in the liver following insult such as hepatitis, by the administration of hepatotoxins, ischaemia, physical damage and partial hepatectomy. Moreover, HGF mRNA is induced in the lung and kidney, in the presence of liver injury. In situ hybridization revealed that HGF-producing cells in liver are non-parenchymal liver cells, presumably Kupffer and sinusoidal endothelial cells. Therefore, HGF from neighbouring cells (Kupffer and sinsuoidal endothelial cells) and distal organs (lung and kidney) may function as a trigger for liver regeneration by both a paracrine mechanism and an endocrine mechanism. HGF has mitogenic activity for renal tubular epithelial cells, epidermal melanocytes and keratinocytes as well as mature hepatocytes, and has the potential to promote cell migration for some epithelial cells, including normal human keratinocytes. Since cell growth and cell motility are relevant to tissue repair and embryogenesis, HGF may well have important roles in tissue repair and embryogenesis as well as in liver regeneration.

Localization of hepatocyte growth factor in human and rat tissues: an immunohistochemical study

Hepatocyte growth factor is a protein growth factor with a strong mitogenic effect on hepatocytes. Recently, hepatocyte growth factor and hepatocyte growth factor messenger RNA have been extracted from several organs of humans, rats and rabbits. This study was undertaken to comprehensively define and compare the cellular localization of hepatocyte growth factor in human and rat tissues in detail. Paraffin-embedded sections and frozen sections were examined by immunohistochemistry using a polyclonal antiserum to hepatocyte growth factor. The distribution of hepatocyte growth factor was almost identical in humans and rats. Strong or moderate cytoplasmic immunoreactivity for hepatocyte growth factor was present in most surface epithelia, distal tubules and collecting ducts of the kidneys, large neurons, megakaryocytes, granulocytes, exocrine pancreas, salivary glands, prostate, epididymis and trophoblast. Varying degrees of immunoreactivity were observed in endothelial cells, chondrocytes and macrophages. We conclude that hepatocyte growth factor is widely distributed in numerous tissues and cell types independent of their regenerative activity. This suggests that hepatocyte growth factor may have mitogenic and/or trophic effects on multiple cell types in addition to hepatocytes.

Significance of tumor necrosis factor (TNF) and interleukin-1 (IL-1) in the pathogenesis of fulminant hepatitis: possible involvement of serine protease in TNF-mediated liver injury

The effect of tumor necrosis factor (TNF)-alpha and interleukin-1 (IL-1) alpha, which are thought to be principal mediators inducing homeostatic abnormalities during endotoxemia, were investigated on cultured hepatocytes in an attempt to understand their role in the pathogenesis of fulminant hepatitis. Both TNF and IL-1 had no direct cytotoxicity on cultured adult rat hepatocytes as assessed by their effects on protein synthesis and also cytosolic enzyme activity released into the culture medium in the presence of 5 mM D-galactosamine (Ga1N). However, IL-1 caused a dose-dependent inhibition of DNA synthesis in cultured adult rat hepatocytes. Moreover, the serum from TNF-treated rats, prepared after intravenous administration of TNF (5 X 10(4) U per rat), caused a significant increase of enzyme release into culture medium in contrast to control rat serum. The cytotoxicity disappeared when the serum from TNF-treated rats was pretreated by heating at 56 degrees C for 30 min, and was decreased by the addition of the protease inhibitor, aprotinin. In vivo, gabexate mesilate, a serine-type protease inhibitor, prevented GalN/TNF-induced fulminant hepatitis, whereas MX-1, an anti-complement agent, had no such effect. These results strongly suggest that IL-1 has a inhibitory effect on hepatocytes in terms of DNA synthesis and that TNF indirectly induces hepatocellular damage through the serine proteases which are possibly activated by the cytokine in vivo.

Assignment of the hepatocyte growth factor (HGF) to chromosome 7q22-qter

The hepatocyte growth factor (HGF) is thought to be important in the growth of hepatocytes during normal foetal liver growth and following liver damage. The human gene encoding HGF has been mapped to chromosome 7 and shown to be localized in the region q22-qter.

Inhibitors of hepatic DNA synthesis in fulminant hepatic failure

In certain etiological groups of patients with fulminant hepatic failure, poor survival may be due to lack of liver regeneration. In vitro experiments have shown that fulminant hepatic failure serum is cytotoxic to rabbit hepatocytes and inhibits DNA synthesis on short-term incubation with isolated regenerating rat hepatocytes. When fulminant hepatic failure serum is injected into partially hepatectomized rats at the time of maximal DNA synthesis, [3H]thymidine incorporation into hepatic DNA is reduced significantly. The effect is greater with sera obtained from patients with fulminant hepatic failure due to non-A, non-B hepatitis or an adverse drug reaction and is associated with a less than 10,000-dalton fraction. No stimulation of DNA synthesis is observed with injection of the greater than 10,000-dalton serum fraction into normal rats. In preliminary experiments, no increase in epidermal growth factor production has been found in liver failure. Overall, the substances present in fulminant hepatic failure serum appear to be inhibitory rather than stimulatory for liver cell regeneration.

Human hepatocyte growth factor in blood of patients with fulminant hepatic failure. I. Clinical aspects

The levels of human hepatocyte growth factor (hHGF) in sera obtained from patients with various liver diseases were determined using adult rat hepatocytes maintained in primary culture. The mean hHGF activity for 22 patients with fulminant hepatic failure was about nine times greater than that found in normal human serum. The increase in serum hHGF activity seen in two patients with "acute-on-chronic" hepatitis was similar to that found in patients with fulminant hepatic failure. The serum level of hHGF from patients with acute hepatitis is related to the stage of their illness. The average value for 31 patients was about three times that of normal human serum. In some patients, the time course for the increase in serum hHGF activity was similar to that demonstrated for alpha-fetoprotein. The mean hHGF activity in serum for the 33 patients with chronic hepatitis and from 25 patients with liver cirrhosis was increased also compared with that of normal human serum. In addition, serum hHGF activity in three of seven patients studied after partial hepatectomy for a space-occupying lesion of the liver was increased. These data suggest that the increase in serum hHGF activity present in patients with various liver diseases reflects a self-defense mechanism that is involved in the process of liver cell regeneration.

Possible endocrine control by hepatocyte growth factor of liver regeneration after partial hepatectomy

Hepatocyte Growth Factor (HGF), which is a most potent growth factor for primary cultured hepatocytes, may act as a trigger for liver regeneration. After 70% of the rat liver was removed, HGF activity in the remnant liver began to increase within 24 h. In parallel with the activity, the HGF mRNA level in the remnant liver increased at 12 h after the operation and reached a maximum at 24 h. Increases in HGF activity and in the mRNA level were much lower and later than those in the liver of rats with hepatitis induced with CCl4. However, the first increase in HGF activity in the plasma of hepatectomized rats was noted 3 h after the resection, that is much earlier than the initial DNA synthesis in the remnant liver. Thus, while HGF production was induced in the remnant liver during regeneration after partial hepatectomy, the initial trigger may not be the liver-derived HGF, rather, it may be HGF derived from extrahepatic organs, via blood circulation.

The immediate-early growth response in regenerating liver and insulin-stimulated H-35 cells: comparison with serum-stimulated 3T3 cells and identification of 41 novel immediate-early genes

Liver regeneration provides a unique system for analysis of mitogenesis in intact, fully developed animals. Cellular immediate-early genes likely play an important role in cell cycle regulation and have been extensively studied in mitogen-stimulated fibroblasts lymphocytes but not in liver. We have begun to characterize the immediate-early growth response genes of mitogen-stimulated liver cells, specifically, regenerating liver and insulin-stimulated Reuber H-35 hepatoma cells, and to address differences in growth response between different cell types. Through subtraction and differential screening of cDNA libraries from regenerating liver and insulin-treated H-35 cells, we have extensively characterized 341 differentially expressed clones and identified 52 immediate-early genes. These genes have been partially sequenced and subjected to Northern (RNA) blot analysis, and 41 appear to be novel. Surprisingly, two-thirds of these genes are also expressed in BALB/c 3T3 cells, but only 10 were identified in previous studies of 3T3 cells, and of these, 6 include well-known genes like jun and fos, and only 4 are novel. Approximately one-third of the immediate-early genes identified in mitogen-stimulated liver cells or serum-stimulated NIH 3T3 cells are expressed in a tissue-specific fashion, indicating that cell type-specific regulation of the proliferative response occurs during the immediate-early period. Our findings indicate that the immediate-early response is unusually complex for the first step in a regulatory cascade, suggesting that multiple pathways must be activated. The abundance of immediate-early genes and the highly varied pattern of their expression in different cell types suggest that the tissue specificity of the proliferative response arises from the particular set of these genes expressed in a given tissue.

The immediate-early growth response in regenerating liver and insulin-stimulated H-35 cells: comparison with serum-stimulated 3T3 cells and identification of 41 novel immediate-early genes

Liver regeneration provides a unique system for analysis of mitogenesis in intact, fully developed animals. Cellular immediate-early genes likely play an important role in cell cycle regulation and have been extensively studied in mitogen-stimulated fibroblasts lymphocytes but not in liver. We have begun to characterize the immediate-early growth response genes of mitogen-stimulated liver cells, specifically, regenerating liver and insulin-stimulated Reuber H-35 hepatoma cells, and to address differences in growth response between different cell types. Through subtraction and differential screening of cDNA libraries from regenerating liver and insulin-treated H-35 cells, we have extensively characterized 341 differentially expressed clones and identified 52 immediate-early genes. These genes have been partially sequenced and subjected to Northern (RNA) blot analysis, and 41 appear to be novel. Surprisingly, two-thirds of these genes are also expressed in BALB/c 3T3 cells, but only 10 were identified in previous studies of 3T3 cells, and of these, 6 include well-known genes like jun and fos, and only 4 are novel. Approximately one-third of the immediate-early genes identified in mitogen-stimulated liver cells or serum-stimulated NIH 3T3 cells are expressed in a tissue-specific fashion, indicating that cell type-specific regulation of the proliferative response occurs during the immediate-early period. Our findings indicate that the immediate-early response is unusually complex for the first step in a regulatory cascade, suggesting that multiple pathways must be activated. The abundance of immediate-early genes and the highly varied pattern of their expression in different cell types suggest that the tissue specificity of the proliferative response arises from the particular set of these genes expressed in a given tissue.

Structure and function of hepatocyte growth factor

Hepatocyte growth factor (HGF), a potent mitogen for mature hepatocytes in primary culture, was first found in sera of partial hepatectomized rats and seems to be a hepatotrophic factor for liver regeneration which has not been purified over the past 30 years. HGF is composed of the 69 kDa alpha-subunit and the 34 kDa beta-subunit. Molecular cloning reveals that HGF is derived from a single chain precursor of 728 amino acid residues and it contains 4 kringle domains in the alpha-subunit. HGF gene spans about 70kb and consists of 18 exons and 17 introns. HGF is now thought to be a pleiotropic factor influencing a cell growth and cell motility for various epithelial cells. HGF receptor with Kd = 20-30pm is widely distributed in various epithelial cells including hepatocytes. HGF mRNA and HGF activity increase markedly in liver after various liver injuries and in kidney following unilateral nephrectomy or acute renal injury. Moreover, HGF mRNA is induced even in the intact lung in response to liver and kidney injury. In situ hybridization reveals that HGF-producing cells are mesenchymal cells such as Kupffer cells and sinusoidal endothelial cells in liver, fenestrated endothelial cells in kidney, and macrophages and endothelial cells in lung. Thus, HGF may play an important role as a paracrine or endocrine mediator through an epithelial-mesenchymal interaction in wound-healing, tissue or organ regeneration, morphogenesis and carcinogenesis.

Physicochemical characteristics of hepatic stimulatory factor prepared from cell free supernatant of hepatocyte cultures

We previously reported that the cell free supernatant of hepatocyte cultures contained a hepatic stimulatory factor, which increases survival time and stimulates liver regeneration in the galactosamine induced fulminant hepatic failure animal model. When hepatocytes were microencapsulated in an alginate matrix, the cell free supernatant outside the microcapsuled lacked the above stimulatory effects. However, the cell free content of microcapsules was able to increase both survival time and incorporation of 3H-thymidine in our animal model. This hepatic stimulatory factor has a molecular weight greater than albumin because alginate microcapsules allow the penetration of albumin but not the hepatic stimulatory factor. In this paper we report the molecular weight study and some other physiochemical characteristics of this factor. Using Sephacryl gel chromatography we showed that this factor has a molecular weight of over 110,000 D. This factor loses its hepatic stimulatory effect after heat or trypsin treatment. Although its elution profile on Sephacryl gel does not change after such treatments.

Effects of hepatic stimulatory factor released from free or microencapsulated hepatocytes on galactosamine induced fulminant hepatic failure animal model

This paper describes the presence of a cell free hepatocyte stimulating factor secreted by hepatocyte cultures. Hepatocytes were isolated from 70-90 grams Wistar-Lewis rats. Free or microencapsulated hepatocytes in alginate matrix were cultured separately. Cell free supernatant was collected from the culture medium in which was cultured free hepatocytes; microencapsulated hepatocytes or control microcapsules containing no microcapsules. This was tested in the galactosamine rats. A galactosamine dose of 2.7 g/Kg of body weight given intraperitoneally to Wistar-Lewis rats resulted in reproducible hepatic necrosis with 90% mortality. Cell free supernatant from one day old free hepatocyte cultures was able to increase survival time and incorporation of 3H-thymidine in liver of galactosamine induced fulminant hepatic failure rats at the time of maximal liver damage. The cell free supernatant of one day old microencapsulated hepatocyte cultures did not have the same stimulatory effect either on survival time or incorporation of thymidine. Another study was carried out as follows. The microcapsules containing hepatocytes were ruptured. The supernatant of the microcapsule contents was collected. This was found to have hepatic stimulatory effect as shown by survival time and incorporation of thymidine. This suggests that hepatocytes are a source of a factor(s) which is capable of stimulating liver regeneration in the galactosamine induced fulminant hepatic failure rats at the time of maximal liver damage. Since the molecular weight cut off of this particular preparation of microcapsule is molecular larger than albumin, this suggests that the molecular weight of this factor is in the macromolecular range.

Expression of hepatocyte growth factor gene in endothelial and Kupffer cells of damaged rat livers, as revealed by in situ hybridization

Hepatocyte growth factor (HGF) has been demonstrated to be synthesized and secreted by non-parenchymal liver cells for liver regeneration after hepatic injury. We performed in situ hybridization to identify HGF-producing cell types in rat liver hepatitis induced by administrating carbon tetrachloride as a hepatotoxin. We found that transcripts of the HGF gene are localized in the Kupffer and endothelial cells in normal livers and increased remarkably in the Kupffer cells of the damaged livers. Thus, HGF is concluded to be synthesized in the Kupffer and endothelial cells to repair the liver tissue in paracrine fashion. No significant increase in the transcripts of the HGF gene was observed in livers after partial hepatectomy, indicating that a mechanism on liver regeneration after the hepatectomy differs from that on liver repairs. Since the HGF gene expression was also found in lung and kidney, HGF may be a ubiquitous factor for tissue repairs.

Primary structure of rat hepatocyte growth factor and induction of its mRNA during liver regeneration following hepatic injury

Overlapping cDNA clones for rat hepatocyte growth factor (rHGF) were isolated by cross-hybridization with the cloned cDNA for human hepatocyte growth factor (hHGF) and the nucleotide sequence of the cDNA was determined. The entire primary structure of rHGF was deduced from the sequence. Comparison of the amino acid sequences between rat and human HGFs revealed that the two sequences are highly conserved throughout the protein structures, suggesting that rat and human HGFs may be functionally similar. Responses of the rHGF mRNA during liver regeneration in rats were examined by Northern blot hybridization analysis with the aid of the cDNA probe for rHGF. The mRNA levels increased in the liver and spleen but not in the kidney after administration of carbon tetrachloride. At the maximum level of induction, the rHGF mRNA increased in the liver about 4.5-fold over its normal level. The mRNA levels also increased in the liver and spleen after administration of D-galactosamine. On the other hand, no obvious increase of the mRNA was observed in the liver and spleen after partial hepatectomy. These observations suggest that HGF may function as a regulator of liver regeneration following hepatic injury caused by hepatotoxins.

Hepatotropin mRNA expression in human foetal liver development and in liver regeneration

A 569 bp probe against the beta-chain of hepatotropin was used to examine expression of RNA for this growth factor in human adult and foetal liver, foetal kidney and pancreas, and rat liver after partial hepatectomy. Low level expression of a 6 kb RNA occurred in human adult and normal rat liver. 70% hepatectomy increased expression, peaking at 10 h and returning to near normal levels 24 h after resection. The 6 kb band was strongly expressed in human foetal liver, as compared with adult, but not in foetal kidney or pancreas, suggesting a major role for hepatotropin in both foetal development and regeneration of the liver.

Failure of insulin and glucagon infusion to stimulate liver regeneration in fulminant hepatic failure

A randomised controlled trial of insulin and glucagon infusion was carried out in 18 patients in grade III or IV coma from fulminant hepatic failure due to viral or drug-induced hepatic necrosis to see whether mortality could be reduced by stimulating hepatic regeneration. Nine patients received a continuous infusion of insulin 3 U/h and glucagon 200 micrograms/h made up in 5% dextrose containing 1% human albumin solution (HAS) while controls received 5% dextrose and HAS alone. Baseline plasma insulin and glucagon levels were comparably raised in both groups and, on infusion, rose significantly higher in the insulin- and glucagon-treated patients compared to controls. Two control and one treated patient recovered. Median survival time from enrolment to death was similar for insulin- and glucagon-treated patients and controls--2 and 3 days, respectively. Insulin and glucagon therapy did not enhance hepatic synthetic function, as measured by a fall in prothrombin time or a rise in alpha-fetoprotein; nor did it stimulate hepatic regeneration, only one patient in each group showed histological evidence of hepatic regeneration at post-mortem.

Deduced primary structure of rat hepatocyte growth factor and expression of the mRNA in rat tissues

The primary structure of rat hepatocyte growth factor (HGF) was elucidated by determining the base sequence of the complementary DNA (cDNA) of HGF. The cDNA for rat HGF was isolated by screening a liver cDNA library with oligonucleotides based on the partial N-terminal amino acid sequence of the beta subunit of purified rat HGF. HGF is encoded in an mRNA of about 6 kilobases. Both alpha and beta subunits of HGF are specified in a single open reading frame for a 728-amino acid protein with a calculated molecular weight of 82,904. The N-terminal part of HGF has a signal sequence and a prosequence with 30 and 25 amino acid residues, respectively. The mature heterodimer structure is derived proteolytically from this single pre-pro precursor polypeptide. The calculated molecular weights of the alpha and beta subunits are 50,664 and 25,883, respectively, and each subunit has two potential N-linked glycosylation sites. The amino acid sequence of HGF is 38% identical with that of plasminogen. The alpha subunit of HGF contains four "kringle" structures, and the beta subunit has 37% amino acid identity with the serine protease domain of plasmin. Northern blot analysis revealed that HGF mRNA was expressed in rat various tissues, including the liver, kidney, lung, and brain.

Tissue distribution of hepatopoietin-A: a heparin-binding polypeptide growth factor for hepatocytes

Hepatopoietin-A (HPTA) is a heparin-binding polypeptide growth factor which consists of a heavy and a light polypeptide chain with molecular weights of 70,000 and 35,000, respectively. It stimulates DNA synthesis in primary cultures of normal rat hepatocytes in serum-free medium. The complete purification and characterization of HPTA from rabbit serum were reported by us elsewhere. Recently we have determined the amino-terminal amino acid sequence of the rabbit HPTA light chain up to 24 residues and have shown that the sequence is not homologous with other known sequences. [N.B. Human hepatocyte growth factor, recently sequenced by two other groups, is the same molecular species as HPTA.] In the present paper we report the production of a neutralizing polyclonal antiserum raised in chicken against purified rabbit HPTA. This antiserum does not inhibit the mitogenic effect of other potent inducers of hepatocyte DNA synthesis (epidermal growth factor or acidic fibroblast growth factor), nor does it interact with these growth factors in an enzyme-linked immunosorbent assay (ELISA). The antibody recognizes HPTA, as was determined by Western immunoblotting. Since the tissue origin of HPTA is not known, this anti-HPTA antiserum was used to investigate the tissue distribution of HPTA in rabbits by immunohistostaining methods. Acinar cells of the pancreas, neurons of the brain, C cells of the thyroid, ductal cells of the salivary glands, and Brunners glands of the duodenum stained with anti-HPTA antibody. Liver, spleen, thymus, and kidney do not seem to contain appreciable amounts of HPTA. We confirmed these findings by extracting and purifying active HPTA from the stained tissues listed above. The anti-HPTA antibody recognizes HPTA purified from different tissues, as was determined by ELISA, Western immunoblotting, and immunoneutralization experiments.

Marked increase of HGF mRNA in non-parenchymal liver cells of rats treated with hepatotoxins

When experimental hepatitis was induced by administrating rats with hepatotoxins such as CCl4 and D-galactosamine, HGF mRNA increased dramatically in the injured liver. The increase of HGF mRNA was time- and dose-dependent. At 5 hr after CCl4-treatment, HGF mRNA was remarkably increased; it reached the maximum level at 10 hr and maintained at this level for 40 hr. On the contrary, in D-galactosamine-induced hepatitis, HGF mRNA started to increase from 24 hr after a long lag time. Moreover, HGF mRNA was expressed transiently, decreasing rapidly to the basal level after reaching the maximum level at 36 hr. The degree of induction of HGF mRNA correlates well to the degree of liver damage. In the liver, HGF mRNA could be detected in only non-parenchymal cells, not in parenchymal hepatocytes. These findings suggest that liver is a main producing organ of HGF for liver regeneration after hepatic injury, and HGF is synthesized and secreted by non-parenchymal liver cells so that it stimulates the growth of parenchymal hepatocytes to repair liver tissue in paracrine fashion.

Further characterisation of 'hepatotropin', a high molecular weight hepatotrophic factor in rat serum

We report further characterisation of the hepatocyte growth factor 'hepatotropin' which is found in rat serum 24 h after partial hepatectomy. Hepatotropin enhances DNA synthesis in primary cultures of adult rat hepatocytes, and is of high molecular weight. Serum fractions were separated by gel filtration, heparin-sepharose affinity chromatography and ion-exchange chromatography. Sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) identified a band of apparent subunit relative molecular weight (Mr) 100,000 associated with biological activity, although purification to homogeneity has not been achieved. The activity is heat-labile, trypsin-sensitive, and stable to lyophilisation, but loses activity after dilution and reconcentration. In combination with known peptide hepatocyte growth modulators, hepatotropin acted synergistically with insulin and epidermal growth factor (EGF) but its action was not enhanced by glucagon. Studies on isolated rat hepatocyte membranes showed no evidence of enhanced phosphorylation of the EGF receptor by hepatotropin. The relationship of hepatotropin to previously described serum and platelet-derived growth factors is discussed.

Release of hepatic stimulatory substance from cultures of free and microencapsulated hepatocytes: preliminary report

The galactosamine induced liver failure animal model was used to study the release of hepatic stimulatory substance (HSS) from free and microencapsulated hepatocytes in culture. Free hepatocyte cultures released HSS which significantly increased DNA synthesis in hepatocyte and the survival time of this animal model. The release HSS was not observed when hepatocytes were microencapsulated in an alginate matrix. The alginate matrix has a pore size which does not allow molecules larger than albumin (64,000 M.W.) to pass through the matrix. This suggests that of the two different ranges of molecular weights suggested for the hepatic stimulatory substance, those in the higher molecular range are important for liver regeneration.

Purification and subunit structure of hepatocyte growth factor from rat platelets

A hepatocyte growth factor (HGF) that stimulates DNA synthesis of adult rat hepatocytes in primary culture was purified as a homogeneous material from platelets of 1000 rats by a four-step procedure: stimulation of its release from platelets by thrombin, cation-exchanger fast protein liquid chromatography (FPLC) on a Mono S column, heparin-Sepharose CL-6B chromatography, and reverse-phase HPLC on a C4 column. The purified HGF stimulated DNA synthesis of adult rat hepatocytes in primary culture at 1 ng/ml and was maximally effective at 5 ng/ml, being about twice as potent as EGF at this concentration. HGF did not stimulate DNA synthesis of Swiss 3T3 cells. It was found to be a heat- and acid-labile protein that was inactivated by reduction with dithiothreitol. The purified HGF had a molecular mass of 82 kDa, as estimated by SDS-PAGE, and was found to be a heterodimer which dissociated into a large subunit of 69 kDa and a small one of 34 kDa by SDS-PAGE under reducing conditions. These biological and chemical properties showed that HGF was not identical with any known growth factors, including platelet-derived growth factor (PDGF).