Tadashi Hishida

Native and recombinant human hepatocyte growth factors are highly potent promoters of DNA synthesis in both human and rat hepatocytes.

Human hepatocyte growth factor (hHGF) has recently been expressed as a recombinant polypeptide from Chinese hampster ovary cell transfectants. Using a primary rat hepatocyte bioassay, we have tested the biological activity of recombinant hHGF and compared it with native hHGF. Dose-response curves were almost identical, with half-maximal stimulation of DNA synthesis at 1-2 ng/ml (equivalent to approximately 10 pM). S-phase labeling index was similarly enhanced and numerous mitotic cells were observed. Recombinant and native hHGF also stimulated DNA synthesis and S-phase labeling index in primary adult human hepatocytes. Human cells were more responsive than rat hepatocytes, with recombinant hHGF slightly more potent than native hHGF (half-maximal stimulation 0.3 and 0.6 ng/ml, respectively). Since HGF levels rise in patients with fulminant hepatic failure and in animals after partial hepatectomy or administration of hepatotoxins, situations where liver regeneration occurs, HGF is suggested to play a key role in regulation of hepatic growth. The high potency of the factor on human hepatocytes reinforces its candidacy as a critical mitogen in human liver growth. The availability of a recombinant hHGF opens the way for in vivo experimental studies and to the possibility of using hHGF as a clinical therapeutic agent, either alone or in combination with other factors.

Human intrahepatic biliary epithelial cells proliferate in vitro in response to human hepatocyte growth factor.

In previous studies, intrahepatic human biliary epithelial cells (BEC) were isolated in high purity. However, these cells demonstrated only limited growth responses. Here we report that human BEC proliferate in response to human hepatocyte growth factor (hHGF), retain BEC-specific phenotype, and can be serially passaged. BEC showed dose-dependent growth in response to 0.01-100 ng/ml hHGF. The maximum S-phase labeling index reached 40% with half-maximal stimulation at 1 ng/ml. The response of cells from normal and primary biliary cirrhotic liver to hHGF was similar. Cultures were immunostained with specific antibodies and then processed for [3H]thymidine autoradiography. Proliferating cells expressed BEC-specific markers (HEA125 and CK-19), but were negative for desmin and factor VIII-related antigen. Occasional vimentin-positive cells were observed, but these were nonproliferative. In conclusion, cells responding to hHGF were clearly BEC in origin. The observation that HGF is mitogenic for BEC as well as hepatocytes has important implications. First, greater yields of intrahepatic BEC are available for subsequent studies of the pathogenesis and etiology of diseases of the biliary epithelium. Secondly, some means of regulating the cellular response to HGF in vivo must operate, in that HGF levels rise early after partial hepatectomy and yet BEC proliferate 24 h later than hepatocytes.

Identification of the N-terminal residue of the heavy chain of both native and recombinant human hepatocyte growth factor.

The N-terminal amino acid of the heavy chain of native (purified from human plasma) and recombinant human hepatocyte growth factor (hHGF) was determined by analyses of amino acid composition and sequence of peptide fragments derived by enzymatic cleavage, peptide mapping, and fast atom bombardment mass spectrometry. Our results indicate that the N-terminal amino acid of the heavy chain of hHGF, both native and recombinant, is pyroglutamate, derived from glutamine at the 32nd residue from the initiation methionine.

Isolation of several cDNAs encoding yeast peroxisomal enzymes

Several candidate clones carrying partial cDNAs for yeast peroxisomal enzymes, such as catalase, carnitine acetyltransferase, isocitrate lyase, malate synthase and acyl‐CoA oxidase, were efficiently isolated at a single plating from a phage λgt11 recombinant cDNA library prepared with poly(A)‐rich RNA from an n‐alkane‐grown yeast, Candida tropicalis, with a mixture of antibodies against the respective purified enzymes. Among them, one candidate clone carrying partial cDNA for catalase was subcloned and subjected to nucleotide sequence analysis. We succeeded in determining that the amino acid sequence deduced from the nucleotide analysis included the sequences derived from the two peptide fragments obtained from the purified enzyme.

Immortalization of human endothelial cells by origin-defective simian virus 40 DNA

Human endothelial cells isolated from an umbilical cord vein were transfected with origin-defective simian virus 40 (SV40) DNA. Among several of the SV40 transfected clones isolated, cell lines SV-2 and SV-3 showed a normal endothelial cell morphology and extended life span, and could survive almost 100 generations. Just before crisis, the morphology of SV-3 changed. SV-3T cell line was isolated from this SV-3 culture, which acquired an almost infinite life span, rapid growth rate and the ability to grow in soft agar. At the same time, the SV-3T cell line lost the factor VIII-related antigen and normal endothelial cell morphology, and showed an abnormal chromosome number. Further characterization showed the ability of SV-2 and SV-3T to produce increasing amounts of tissue plasminogen activator and a similar level of a plasminogen activator inhibitor compared with normal human endothelial cells. These results indicate that the SV-3T cell line was transformed and acquired an infinite life span while still r...

High-level Production of Human β-Endorphin in Escherichia coli

A human opioid peptide hormone, β-endorphin, was expressed in Escherichia coli as the C-terminal portion of a fused protein. The fused protein consisting of the N-terminal 62% of E. coli anthranilate synthetase (323 amino acids), a peptide corresponding to the linker DNA (7 amino acids), and the precursor form of β-endorphin (47 amino acids), was highly expressed under the control of a tryptophan promoter. The level of expression of β-endorphin was estimated to be 17 mg/liter broth by radioimmunoassay, and 51 mg/liter broth by SDS polyacrylamide gel electrophoresis followed by a densitometric analysis. β-Endorphin was cleaved from the fused protein and purified by HPLC, and is presumed to be identical with human β-endorphin because of its amino acid composition and amino acid sequence.