Development of a core descriptor set for Crohn's anal fistula

AIM

Crohn's anal fistula (CAF) is a complex condition, with no agreement on which patient characteristics should be routinely reported in studies. The aim of this study was to develop a core descriptor set of key patient characteristics for reporting in all CAF research.

METHOD

Candidate descriptors were generated from published literature and stakeholder suggestions. Colorectal surgeons, gastroenterologists and specialist nurses in inflammatory bowel disease took part in three rounds of an international modified Delphi process using nine-point Likert scales to rank the importance of descriptors. Feedback was provided between rounds to allow refinement of the next ratings. Patterns in descriptor voting were assessed using principal component analysis (PCA). Resulting PCA groups were used to organize items in rounds two and three. Consensus descriptors were submitted to a patient panel for feedback. Items meeting predetermined thresholds were included in the final set and ratified at the consensus meeting.

RESULTS

One hundred and thirty three respondents from 22 countries completed round one, of whom 67.0% completed round three. Ninety seven descriptors were rated across three rounds in 11 PCA-based groups. Forty descriptors were shortlisted. The consensus meeting ratified a core descriptor set of 37 descriptors within six domains: fistula anatomy, current disease activity and phenotype, risk factors, medical interventions for CAF, surgical interventions for CAF, and patient symptoms and impact on quality of life.

CONCLUSION

The core descriptor set proposed for all future CAF research reflects characteristics important to gastroenterologists and surgeons. This might aid transparent reporting in future studies.

Post-inflammatory polyps burden as a prognostic marker of disease-outcome in patients with inflammatory bowel disease

INTRODUCTION AND AIM

Post-inflammatory polyps (PIPs) are considered as indicators of previous episodes of severe inflammation and mucosal ulceration. Inflammatory bowel disease (IBD), namely Crohn's disease (CD) and ulcerative colitis (UC), exhibit a perpetuating, relapsing, and remitting pattern and PIPs is a frequent sequela of chronicity. The aim of this study was to determine whether a high PIPs burden is associated with a more severe disease course in patients with IBD.

METHODS

This was a multinational, multicentre, retrospective study. IBD patients previously diagnosed with PIPs were retrieved from the endoscopic database of each centre. PIPs burden was evaluated and associated with demographic and clinical data as well as factors indicating a more unfavorable disease course.

RESULTS

A total of 504 IBD patients with PIPs were recruited (male: 61.9%). The mean age at IBD diagnosis was 36.9 (±16.8) years. Most patients (74.8%) were diagnosed with UC. A high PIPs burden was present in 53.4% of patients. On multivariable Cox regression analysis, high PIPs burden was independently associated with treatment escalation (HR 1.35, 95% CI 1.04-1.75; P=0.024), hospitalization (HR 1.90; 95% CI 1.24 - 2.90; P=0.003), need for surgery (HR 2.28; 95% CI 1.17-4.44, P=0.02) and younger age at diagnosis (HR 0.99, 95% CI 0.98-0,99; p=0.003).

CONCLUSION

PIPs burden was associated with a more severe outcome. Future prospective studies should focus on the characterisation of PIPs burden as to further risk stratify this patient cohort.

Liver preservation with machine perfusion and a newly developed cell-free oxygen carrier solution under subnormothermic conditions

We describe a new preservation modality combining machine perfusion (MP) at subnormothermic conditions(21 °C) with a new hemoglobin-based oxygen carrier (HBOC) solution. MP (n=6) was compared to cold static preservation (CSP; n=6) in porcine orthotopic liver transplants after 9 h of cold ischemia and 5-day follow-up. Recipients' peripheral blood, serial liver biopsies, preservation solutions and bile specimens were collected before, during and after liver preservation. Clinical laboratorial and histological analyses were performed in addition to mitochondrial functional assays, transcriptomic, metabolomic and inflammatory inflammatory mediator analyses. Compared with CSP, MP animals had: (1) significantly higher survival (100%vs. 33%; p<0.05); (2) superior graft function (p<0.05);(3) eight times higher hepatic O2 delivery than O2 consumption (0.78 mL O2/g/h vs. 0.096 mL O2/g/h) during MP; and (4) significantly greater bile production (MP=378.5 ± 179.7; CS=151.6 ± 116.85). MP downregulated interferon (IFN)-α and IFN-γ in liver tissue. MP allografts cleared lactate, produced urea, sustained gluconeogenesis and produced hydrophilic bile after reperfusion. Enhanced oxygenation under subnormothermic conditions triggers regenerative and cell protective responses resulting in improved allograft function. MP at 21 °C with the HBOC solution significantly improves liver preservation compared to CSP.

MCM7 amplification and overexpression are associated with prostate cancer progression

The genomic DNA profiles of prostate cancers with aggressive features were compared to the profiles of matched normal DNA to identify genes that are selectively amplified in the cancer cells. One of the identified genes, MCM7, which is a component of the DNA replication licensing complex, has been studied extensively both at the DNA and protein levels in human prostate tissues. Approximately half of the prostate cancer specimens studied showed MCM7 gene amplification, and 60% of the aggressive prostate cancer specimens had increased MCM7 protein expression. Amplification or overexpression of MCM7 was significantly associated with relapse, local invasion and a worse tumor grade. Constitutive expression of MCM7 in a human prostate cancer cell line, DU145, resulted in markedly increased DNA synthesis and cell proliferation compared to vector-only controls, and an increased cell invasion in vitro. Indeed, MCM7 overexpression produced primary tumors 12 times larger than vector-only controls and resulted in a rapid demise of mice bearing those tumors. These studies implicate MCM7, and the DNA replication licensing gene family, in prostate cancer progression, growth and invasion.

Myopodin, a synaptopodin homologue, is frequently deleted in invasive prostate cancers

Prostate cancer is one of the leading causes of cancer-related deaths for men in the United States. Like other malignancies, prostate cancer is underscored by a variety of aberrant genetic alterations during its development. Although loss of heterozygosity or allelic loss is frequently identified among prostate cancers, few genes have been identified thus far as critical to the development of invasive prostate cancers. In this report, we used the recently developed technology, the "differential subtraction chain," to perform a genome-wide search for sequences that are deleted in an aggressive prostate cancer. Among the deleted sequences, we found that one sequence was deleted in >50% of prostate cancers we tested. We mapped this sequence to chromosome 4q25 by screening the Genebridge 4 hamster radiation panel with primers specific to this probe, and subsequently identify a 54-kb minimal common deletion region that contains the sequence encoding myopodin. Sequence analysis indicates that myopodin shares significant homology with synaptopodin, a protein closely associated with podocyte and neuron differentiation. Further study shows that frequent complete or partial deletions of the myopodin gene occurred among invasive prostate cancer cases (25 of 31 cases, or 80%). Statistical analysis indicates that deletion of myopodin is highly correlated with the invasiveness of prostate cancers, and thus may hold promise as an important prognostic marker for prostate cancers.

Hepatocellular carcinomas in native livers from patients treated with orthotopic liver transplantation: biologic and therapeutic implications

The gross and histopathologic characteristics of 212 nonfibrolamellar hepatocellular carcinomas (HCCs) discovered in native livers removed at the time of liver transplantation were correlated with features of invasive growth and tumor-free survival. The results show that most HCCs begin as small well-differentiated tumors that have an increased proliferation rate and induce neovascularization, compared with the surrounding liver. But at this stage, they maintain a near-normal apoptosis/mitosis ratio and uncommonly show vascular invasion. As tumors enlarge, foci of dedifferentiation appear within the neoplastic nodules, which have a higher proliferation rate and show more pleomorphism than surrounding better-differentiated areas. Vascular invasion, which is the strongest predictor of disease recurrence, correlates significantly with tumor number and size, tumor giant cells and necrosis, the predominant and worst degree of differentiation, and the apoptosis/mitosis ratio. In the absence of macroscopic or large vessel invasion, largest tumor size (P <.006), apoptosis/mitosis ratio (P <.03), and number of tumors (P <.04) were independent predictors of tumor-free survival and none of 24 patients with tumors having an apoptosis/mitosis ratio greater than 7.2 had recurrence. A minority of HCCs (<15%) quickly develop aggressive features (moderate or poor differentiation, low apoptosis/mitosis ratio, and vascular invasion) while still small, similar to flat carcinomas of the bladder and colon. In conclusion, hepatic carcinogenesis in humans is a multistep and multifocal process. As in experimental animal studies, aggressive biologic behavior (vascular invasion and recurrence) correlates significantly with profound alterations in the apoptosis/mitosis ratio and with architectural and cytologic alterations that suggest a progressive accumulation of multiple genetic abnormalities.

Adrenergic stimulation of hepatocyte growth factor expression

Hepatocyte growth factor (HGF), a potent mitogen, is released into plasma at increased levels following injury to certain tissues, including the liver. Early increases in plasma HGF are not due to a release from the injured liver, but rather from distal organs, particularly the lung. We have investigated the ability of norepinephrine (NE), which rises rapidly in plasma after liver resection, to trigger elevated production of HGF in MRC-5 human embryonic lung fibroblasts. Levels of HGF released to culture media and of HGF mRNA increased when cultures were exposed to NE, or to other adrenergic agonists. While stimulation of either beta- or alpha(1)-adrenergic receptors increased HGF expression, responses to NE appear to be mediated primarily via beta receptors. Since NE has already been shown to act as a comitogen with HGF, our findings suggest that adrenergic hormones may act both to induce production of HGF at distal sites, and to enhance the response to HGF at target tissues.

Bcl-2 protein expression in acute and chronic hepatitis, cirrhosis and hepatocellular carcinoma

Bcl-2 protein blocks apoptosis and is involved in human intrahepatic bile-duct development. Formalin-fixed, paraffin-embedded archival tissue from 42 HBV and HCV hepatitis [20 acute AH, 22 chronic hepatitis (CH)], 12 active cirrhosis (CR) and 20 hepatocellular carcinoma (HCC) was immunostained for bcl-2 protein. In all cases, bcl-2 protein was detected in portal and intralobular lymphocytes but not in hepatocytes or Kupffer cells. Bcl-2 was positive in the cytoplasm of small portal bile ducts of chronic hepatitis, while it was strongly expressed in newly formed bile-ductules of the limiting plate, mainly in CH with marked activity and CR. Bcl-2 was detected in small bile ducts in only one case of acute hepatitis and was not detected in any case of HCC. Bcl-2 seems to be involved in the regulation of growth and apoptosis of cholangiolar cells. Its expression in small bile ducts and in newly-formed ductules especially in CH with marked activity and CR, implies that the embryonic model of intrahepatic bile duct development may be recapitulated in chronic hepatic disease. Moreover, it supports evidence for the existence of the controversial long-lived stem population in the liver. Bcl-2 does not seem to be involved in hepatocarcinogenesis.

Interleukin-6, hepatocyte growth factor, and their receptors in biliary epithelial cells during a type I ductular reaction in mice: interactions between the periductal inflammatory and stromal cells and the biliary epithelium

The interleukin-6 (IL-6)/gp-80 and hepatocyte growth factor (HGF)/met ligand/receptor systems have been shown to stimulate biliary epithelial cell (BEC) DNA synthesis in vitro. The mRNA and protein production of these two in vitro mitogens were mapped in vivo during the first week after bile duct ligation (BDL) when peak BEC DNA synthesis is seen. Changes around the biliary tree were compared with those seen in the peripheral liver using a combination of Northern blotting and a unique biliary tree isolation technique, in which the bile ducts and the surrounding portal stroma and inflammatory cells are separated from the hepatocytes by perfusion digestion. Further localization was performed with in situ hybridization and immunohistochemistry. In the normal liver, there is low-level expression of HGF mRNA by periportal stellate cells, and HGF protein localizes to these cells and to neutrophils; extracellular HGF protein is present in the bile. There is no detectable IL-6 mRNA by Northern analysis or IL-6 protein expression in the normal liver, but both met and IL-6 receptor (IL-6R) mRNA are detectable; met mRNA is expressed strongly in the biliary tree, and met protein is expressed weakly on hepatocytes and strongly on BEC. IL-6R mRNA is weakly expressed in the biliary tree, and IL-6R protein is detectable on hepatocytes, with a periportal-to-perivenular gradient, but not on BEC. During the first 3 days after BDL, HGF mRNA expression is increased in both the biliary tree and in the peripheral liver, and production is localized to stellate cells, periductal neutrophils, and stromal cells, which typically accompany the proliferating ductules. IL-6 mRNA and protein were detected only near the biliary tree after BDL, and not in the peripheral liver, and the production was localized to periductal hematolymphoid cells, which had the morphological appearance of macrophages and/or dendritic cells. There is also a distinct up-regulation of met and gp-80 mRNA and protein in the biliary tree, which is stronger than that seen in the peripheral liver. Met protein expression is increased, and IL-6R(gp-80) protein is induced on the proliferating BEC, consistent with the participation of both the HGF/met and IL-6/gp-80 systems in the early phases of type I ductular reactions. These observations show that periductal hematolymphoid and stromal cells are the source of BEC growth factors, and receptors for these factors are up-regulated on BEC during active ductular proliferation. Complex interactions between the inflammatory, stromal, and BEC results in a dysmorphogenic repair response that eventually leads to cirrhosis.

Immunodetection of c-met-oncogene's protein product in renal cell neoplasia

The proto-oncogene c-met encodes a transmembrane tyrosine kinase receptor for hepatocyte growth factor and is expressed in normal kidney tissue. This receptor may be involved in the carcinogenesis of various organs. The aim of this study was to investigate the relationship between c-met immunohistochemical expression and pathological tumor variables in human renal cell carcinomas (RCCs) and adenomas (RAs). Formalin fixed, paraffin embedded tissues from 35 RCCs, 16 RAs and 17 normal kidneys were immunostained (Strept. ABC/HRP) with a polyclonal antibody against c-met protein (Santa Cruz, Clone C-12). The statistical analysis was performed using the linear trend in proportions and Fisher's exact test. C-met protein was detected in the cytoplasm and the plasma membranes of neoplastic cells in 19/35 RCCs (54%), 10/16 adenomas (63%) (p = 0.41) and in 17/17 controls in the epithelial cells of distal renal tubules and collecting ducts. C-met protein expression was not related with gender (p = 0.45), age (p = 0.18), tumor size (p = 0.99), cell type (p = 0.26), grade (p = 0.86) and stage (p = 0.33). Moreover, c-met immunopositive tumor cell percentage and intensity were increased in stage [RCCs, but these results were not statistically significant. Apart from glandular differentiation, c-met protein expression was not related to other histopathological features (i.e. to the type of cells or to any selective overexpression in tumor cells). C-met product may be involved in the malignant transformation of tubular epithelial cells as an early event in RCC carcinogenesis. C-met expression does not seem to have any prognostic significance for RCCs, as it was not associated with any pathological prognosticator.

Keratinocyte growth factor and embryonic rat lung morphogenesis

We examined possible roles of keratinocyte growth factor (KGF) and hepatocyte growth factor (HGF) in lung morphogenesis. By polymerase chain reaction, transcripts for both KGF and its receptor were detected early (rat gestational days 16 and 14, respectively) and their abundance increased during lung morphogenesis. To evaluate possible role of KGF in lung morphogenesis, day 14 lung explants were cultured in Dulbecco's modified Eagle medium + 10% fetal calf serum for 1 to 4 days in the presence (5-50 ng/ml) or absence of KGF (control). KGF (at 25 and 50 ng/ml) induced a marked reduction in the number of terminal branches and destination of the distal epithelium into cyst-like structures. These effects of exogenous KGF were progressively diminished by increasing concentrations of anti-KGF (2-16 micrograms/ml). Electron microscopic examination revealed that the epithelial cells of the cystic structures contained lamellar bodies, and were therefore type II cells and/or their progenitors. Northern blot analysis showed higher expression of surfactant protein C (SP-C) mRNA (a marker for alveolar epithelial type II cells) in KGF-treated fetal lungs. In situ hybridization of the KGF-treated lungs revealed that the SP-C mRNA-expressing cells were arranged distally in the form of linear arrays, a pattern distinctly different from that in control lungs. Acidic fibroblast growth factor, which also binds KGF receptors, in the presence of heparin mimicked the effect of KGF on branching. Transforming growth factor-beta(1) (TGF-beta 1) inhibited branching of fetal lungs in culture, and this effect dominated over that induced by KGF. Blocking of endogenous HGF with antibodies or addition of HGF to cultures of fetal lung explants had no significant effect on branching or growth. In conclusion, KGF markedly influences branching, and epithelial growth, differentiation, and patterning during lung morphogenesis.

Effects of hepatocellular mitogens on cytokine-induced nitric oxide synthesis in human hepatocytes

The synthesis of induced nitric oxide (NO) is regulated by several cytokines, including growth factors produced following hepatic injury and inflammation. However, little information is available on the role of growth factors in regulating the inducible NO synthase in human hepatocytes. The capacity of hepatocellular mitogens (HGF, EGF, and TGF-alpha) to regulate the inducible NO synthase (iNOS) was studied in human hepatocytes incubated with inflammatory cytokines and lipopolysaccharide (LPS). Furthermore, the effects of hepatic mitogens on NO-induced changes in DNA and protein synthesis was studied. It was found that NO-mediated decrease of protein and DNA synthesis were partially reversed by the mitogens. This was associated with a down-regulation in cytokine-mediated hepatocyte NO formation, iNOS mRNA expression, and NOS enzyme activity. Cytokine-induced NO formation or SNAP, an NO donor, added with cytokines increased hepatocyte chromatin condensation but no DNA fragmentation was observed. The increase in chromatin condensation was partially reversed by hepatic mitogens and corresponded with the inhibition of NO production. Thus, the hepatic mitogens, HGF, EGF, and TGF-alpha, all suppress iNOS expression and it is the suppression of iNOS that appears to be responsible for the mitogen-reduced preservation of DNA and protein synthesis and prevention of chromatin condensation.

Ductular reaction after submassive necrosis in humans. Special emphasis on analysis of ductular hepatocytes

The ductular reaction to acute submassive necrosis was studied in human livers removed at the time of orthotopic liver transplantation. Single, double, and triple immunohistochemical labeling in combination with morphometry was used to analyze the phenotype and proliferative and apoptotic rates of various epithelial cell compartments. These were divided on the basis of immunohistochemistry and morphology into three subtypes: 1) CK19+/AE1+ mature bile duct epithelium, 2) HEP-PAR+ mature hepatocytes (HEPs), and 3) CK19+/AE1+ ductular hepatocyte (DH) cells lying at the interface between the portal tract connective tissue and the hepatic lobules. Cycling cells were defined as those showing Ki-67+ (MIB-1) nuclear labeling. Apoptotic cells were identified with in situ labeling using the terminal deoxynucleotidyl transferase-mediated dUTP-digoxigenin nick end labeling assay. Special emphasis was placed on DHs that appeared at the interface between the portal tracts and hepatic lobules. During the recovery phase from submassive hepatic necrosis, subtraction of the rate of cell death from the proliferative index shows that all of the epithelial compartments experience a net increase in the number of cells. The highest proliferation rate occurs in the DHs, which is significantly (P < 0.0001) higher than the proliferation rate seen in either the HEP or bile duct epithelium compartments. Immunohistochemical analysis of the highly proliferative DH compartment shows it to be a heterogeneous population with unique phenotypic features. Like epithelial cells in the ductal plate of fetal liver and cholangiocarcinomas, DHs are positioned on a laminin-rich matrix and focally express vimentin and Lewis(x) and show up-regulation of bcl-2 and type IV collagenase. However, unlike ductal plate cells, DHs are CD34 and alpha-fetoprotein negative. Although a subpopulation of DHs share phenotypic features with mature bile duct epithelium (AE1/cytokeratin 19 and type IV collagenase positive) or HEP (HEP-PAR, albumin, and alpha-1-antitrypsin positive), they are also clearly separate from both populations; DHs are negative or only weakly stain for glutathione-S-transferase-pi and are type IV collagenase positive. Moreover, occasional DHs also co-expressed HEP-PAR or alpha-1-antitrypsin and AE1, indicative of both hepatocyte and ductular differentiation. These findings suggest that DHs seen in human livers after submassive necrosis may represent a transient amplifying population arising from a progenitor population located in or near the canals of Herring. In addition, injured hepatocytes can express cytokeratin 19 and AE1, which normally are biliary intermediate filaments.

Mitogenic effect of basic fibroblast growth factor and estradiol on cultured human myometrial and leiomyoma cells

OBJECTIVE

We compared the mitogenic effect of basic fibroblast growth factor with and without estradiol on myometrial and leiomyometrial cells.

STUDY DESIGN

The mitogenic effect of basic fibroblast growth factor on myometrial cells was measured by thymidine incorporation and cell count. The mitogenic effect of basic fibroblast growth factor with and without estradiol as measured by thymidine incorporation was compared between myometrial and leiomyometrial cells.

RESULTS

Both human myometrial and leiomyometrial cells showed significant (p = 0.004 and p = 0.001, respectively), dose-dependent incorporation of thymidine in response to basic fibroblast growth factor. Leiomyometrial cells showed significantly (p = 0.04) less thymidine incorporation compared with matched normal myometrial cells. The addition of estradiol with basic fibroblast growth factor did not result in a further increase in thymidine incorporation.

CONCLUSIONS

Both myometrial and leiomyometrial cells respond to basic fibroblast growth factor with increased thymidine incorporation; however leiomyometrial cells are less responsive than are matched normal myometrial cells. The addition of estradiol is not synergistic with basic fibroblast growth factor.

Different proliferative responses of periportal and pericentral rat hepatocytes to hepatocyte growth factor

Stimulation of DNA-synthesis by HGF was compared in cultured periportal and pericentral hepatocyte populations. Periportal hepatocytes showed a higher maximal stimulation of the BrdU labeling index than pericentral hepatocytes (7-fold vs 4-fold), while the stimulation for total hepatocytes was in between (5-fold). The glutamine synthetase-positive hepatocytes adjacent to the central veins responded much less to HGF than did the pericentral cells in general. These inherent differences in the growth potential of hepatocytes from different lobular localizations may contribute to the enhanced growth of hepatocytes in the periportal zone in normal and regenerating liver.

Hepatocyte growth factor stimulates DNA synthesis in alveolar epithelial type II cells in vitro

Hepatocyte growth factor (HGF) and its receptor, the product of c-MET proto-oncogene, are highly expressed in both fetal and adult lung, though their physiologic functions in the lung are largely unknown. In the present study, we examined whether alveolar type II cells in the lung are the target of HGF and whether HGF has any effects on growth of these cells. The alveolar epithelial type II cells were isolated from the lungs of adult male Sprague-Dawley rats by elastase digestion, and the cells were used to determine whether they express HGF and c-MET mRNAs and whether recombinant HGF has any effect on their DNA synthesis in primary culture. The effects were further compared with those induced by epidermal growth factor (EGF), acidic fibroblast growth factor (aFGF), transforming growth factor-alpha (TGF-alpha), and transforming growth factor-beta 1 (TGF-beta 1). Northern blot analysis and in situ hybridization revealed that type II cells express c-MET mRNA but not HGF mRNA. HGF stimulated [3H]thymidine incorporation into type II cells in primary cultures. An increase was also seen in labeling index as determined by nuclear immunostaining of bromodeoxyuridine-incorporated DNA. While aFGF (200 ng/ml) exerted an effect comparable to HGF (25 ng/ml) on DNA synthesis in type II cells, EGF (20 ng/ml) and TGF-alpha (100 ng/ml) had lesser effects. TGF-beta 1, a potent inhibitor of epithelial cell proliferation, at 0.25 to 2 ng/ml, did not inhibit HGF-induced [3H]thymidine incorporation into type II cells. The results indicate that HGF exerts its effects on type II cells as a potent mitogen by a paracrine mode of action.

Human biliary epithelial cells secrete and respond to cytokines and hepatocyte growth factors in vitro: interleukin-6, hepatocyte growth factor and epidermal growth factor promote DNA synthesis in vitro

Recombinant growth factors and proinflammatory cytokines were added to primary cultures of human intrahepatic biliary duct epithelia to test for their ability to stimulate DNA synthesis and elicit cytokine production. Interleukin-6 and hepatocyte and epidermal growth factors were found to increase the DNA labeling index of biliary duct epithelium from fourfold to sixfold 24 hr after their addition to primary biliary duct epithelium cultures maintained in serum-free medium. The proliferative responses to all three biliary duct epithelium mitogens peaked within 24 hr, and hepatocyte growth factor was effective over a concentration range of 1.0 to 50 ng/ml, whereas interleukin-6 was effective from 1 to 1,000 U/ml. Insulin-like growth factor, phorbol myristate acetate, interleukin-1 beta and platelet-derived growth factor BB showed mild stimulatory effects, whereas interleukin-4, gamma-interferon, phytohemagglutinin and platelet-derived growth factors AA and AB did not increase DNA synthesis in biliary duct epithelium. Interleukin-1 beta and phorbol myristate acetate were also shown to induce in a dose-dependent fashion a threefold to fivefold increase of interleukin-6 production as measured by enzyme-linked immunosorbent assay in human primary biliary duct epithelium cultures, when compared with hepatocyte growth factor, epidermal growth factor, insulin-like growth factor, phytohemagglutinin, tumor necrosis factor-alpha or platelet-derived growth factor. These results show that interleukin-6 participates in growth regulation of human biliary duct epithelium. This could be exerted in a paracrine or autocrine manner.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of octreotide on hepatic regeneration in rats

The effect of the long-acting somatostatin analog octreotide on liver regeneration was studied in rats in vitro and in vivo. The effect of continuous subcutaneous octreotide infusion on regenerative liver weight and relative DNA synthesis was examined in rats that had undergone 70% hepatectomy. Administration of octreotide resulted in a 33% reduction of regenerating liver weight at 72 hours and a 67% reduction of regenerative hepatocellular hyperplasia at 24 hours. This effect was reversed within 12 hours after withdrawal of the drug. The mechanism for the inhibitory effect of octreotide appears to be indirect, because experiments in hepatocyte cultures did not demonstrate a direct inhibitory effect on serum-free or epidermal growth factor-induced regenerative hepatocyte proliferation. Because insulin levels were suppressed by octreotide in the in vivo experiments, suppression of hepatotrophs may be the mechanism by which octreotide inhibits liver regeneration.

Orotic acid, nucleotide-pool imbalance, and liver-tumor promotion: a possible mechanism for the mitoinhibitory effects of orotic acid in isolated rat hepatocytes

This study was designed to determine the possible mechanism by which orotic acid exerts its mitoinhibitory effect on rat hepatocytes in primary culture. Orotic acid inhibited, dose-dependently DNA synthesis in hepatocytes induced by epidermal growth factor, transforming growth factor alpha, hepatocyte growth factor, acidic fibroblast growth factor, or plasma from rats exposed to various liver cell-proliferative stimuli, such as two-thirds partial hepatectomy, lead nitrate, cyproterone acetate, ethylene dibromide, or a diet deficient in choline. Further, orotic acid inhibited DNA synthesis even when added 24 h after the hepatocytes were primed with transforming growth factor alpha. Taken together, these results suggested that the target site may not be at the level of the growth-factor receptor and receptor-mediated early events. In a preliminary experiment, orotic acid inhibited the expression of the ribonucleoside diphosphate reductase gene. Exposure to orotic acid results in an imbalance in nucleotide pools characterized by an increase in uridine nucleotides and a decrease in adenosine nucleotides. It is hypothesized that this imbalance in nucleotide pools inhibits the expression of the ribonucleoside diphosphate reductase gene and, therefore, is a likely target for the mitoinhibitory effect of orotic acid.

Localization of hepatocyte growth factor (HGF) gene on human chromosome 7

Hepatocyte growth factor (HGF) is a potent mitogen for hepatocytes and a variety of epithelial cells in culture. The cDNAs for human and rat HGF have been cloned by different researchers, including ourselves; however, no information on the genomic structure and chromosome localization of the HGF gene is yet available. To investigate HGF's chromosomal localization, DNA from a battery of human-hamster somatic cell hybrids was digested with BglII and analyzed by Southern blot using a 2.3-kb human HGF cDNA as a hybridization probe. The gene encoding the human HGF was assigned to human chromosome 7. Restriction enzyme and Southern blot analyses using the HGF cDNA and HGF-specific oligonucleotides as probes suggest that the human HGF gene exists as a single-copy gene and is composed of several exons.

Hepatocyte growth factor/hepatopoietin A stimulates the growth of rat kidney proximal tubule epithelial cells (RPTE), rat nonparenchymal liver cells, human melanoma cells, mouse keratinocytes and stimulates anchorage-independent growth of SV-40 transformed RPTE

Hepatocyte growth factor/hepatopoietin A is a mitogen for primary hepatocytes and may mediate regeneration after liver damage. To date, the activity of this novel factor has been restricted to hepatocytes. We now show that the factor is also a mitogen for a number of primary epithelial cells but is inactive with human foreskin fibroblasts, human endothelial cells and HEP3B cells. The factor also substitutes for HBGF-2 (basic FGF) in stimulating the anchorage-independent growth of SV-40 transformed rat kidney epithelial cells. Therefore, hepatocyte growth factor/hepatopoietin A appears to act on a variety of epithelial, but not mesenchymal, cells which respond to HBGFs.

Identification and partial characterization of receptor binding sites for HGF on rat hepatocytes

Hepatocyte Growth Factor (HGF) (also known as Hepatopoietin A [HPTA] (1-9) is a heterodimeric heparin-binding polypeptide mitogen for hepatocytes distinct from other well-known growth factors. In this study, biologically active radioiodinated HGF was used to identify binding sites on intact hepatocytes in culture. The results show the presence of relatively low affinity binding sites due to the presence of heparin or heparin-like molecules and high affinity specific receptor binding sites on the cell surface of intact hepatocytes. Scatchard analysis of binding data indicates an apparent dissociation constant (Kd) of 3.5 nM with 120,000 sites per hepatocyte for the cell-surface receptor. Analysis of affinity cross-linked 125I-HGF-receptor complex by SDS-PAGE under non-reducing conditions reveals the presence of a distinct band with apparent Mr of 230,000. These data show that HGF exerts its biological effect on hepatocytes (stimulation of DNA synthesis) through a specific and unique cell-surface receptor.

Induction of cytochrome P(1)450 RNA and benzo[a]pyrene metabolism in primary human hepatocyte cultures with benzanthracene

Exposure of cells to microsomal enzyme inducers can modify the potency of many carcinogens. We have examined the steady-state level of RNA from the P(1)450 gene and the metabolism of benzo[a]pyrene (BP) in primary cultures of human hepatocytes exposed for up to 4 days to 12.5 microM benzanthracene (BA), and in uninduced control cultures. While the steady-state levels of RNA from the P(1)450 gene were nondetectable in uninduced (DMSO only) human hepatocytes, 12.5 microM BA-induced AHH activity, BP metabolism, and/or P(1)450-specific RNA in hepatocytes from seven human cases were investigated. RNA levels specific for the P(1)450 gene appeared maximal at 24 hr following exposure to BA, whereas, the protein, as determined by AHH enzyme activity from BA-induced hepatocytes, continued to increase up to the last time point examined, 72 hr. BA induction for 96 hr increased metabolism of BP (initial concentration of BP, 10 microM) over a time course of 3, 6, 12, and 24 hr of incubation with BP compared with that of controls. The major metabolites of BP produced by human hepatocytes in culture were the unidentified polar BP metabolite(s), possibly polyhydroxylated. BA induction caused approximately a twofold increase in these metabolites. BA-induced cultures showed an increase in glutathione conjugation compared to that in controls. The percentage of glucuronide and sulfate conjugates remains similar in all cultures. Total binding of tritium label BP to DNA was 1.3-fold to fivefold greater in induced cultures, and related more to total metabolism than to production of a specific metabolite. Exposure of human hepatocytes in vitro to BA leads to a large increase in the steady-state level of the RNA specific for the P(1)450 gene and an increase metabolism of BP.

Conjugation of chemical carcinogens by primary cultures of human hepatocytes

1. The conjugation of benzo[a]pyrene (BP) and 2-acetylaminofluorene (AAF) was investigated in primary cultures of human hepatocytes. Human hepatocytes conjugated 12.5-63% of the BP and 1.7-52% of the AAF to sulphates and glucuronides over a thousand-fold concentration range. 2. BP is conjugated to glucuronides from non-detectable levels to 50%, and to sulphates from non-detectable levels to 30%. The major conjugated metabolites are the highly polar metabolites. 3. AAF is conjugated to glucuronides from 1.5 to 51% and to sulphates from 0.2 to 12%. The C-hydroxylated AAF metabolites were conjugated to glucuronides more than N-hydroxy AAF and aminofluorene metabolites.

Exocrine pancreatic tissue in human liver: a metaplastic process?

Numerous microscopic foci of exocrine pancreatic tissue consisting of acini and small ductules were distributed throughout the liver of a 41-year-old patient with severe posthepatitic cirrhosis. The acinar cells were characterized by abundant zymogen granules on electron microscopic examination and a strong reaction with antibodies to alpha-amylase on immunoperoxidase staining. The pancreatic tissue was associated with proliferations of bile ductules within areas of fibrosis. No relationship with hepatocytes was observed. A metaplastic origin of the pancreatic tissue from the intrahepatic biliary epithelium is suggested.

Characterization of ductular hepatocytes in end-stage cirrhosis

The existence of facultative stem cells in the liver has been advocated based on observations from models of carcinogenesis in rat liver. Observations of human liver material from cases of fulminant hepatitis have shown the presence of ductular hepatocytes expressing markers of both hepatocytes and bile duct cells. We describe the morphologic features and antigenic expression of a population of ductular hepatocytes identified in a patient with end-stage cirrhosis resulting from hepatitis B infection and secondary biliary cirrhosis. By conventional light microscopy and electron microscopy, ductular hepatocytes were seen to form pseudoductules within periportal areas. Using immunohistochemical methods, these ductular hepatocytes were found to be positive for both the hepatitis B surface antigen and bile duct epithelial cytokeratin, phenotypic markers classically restricted to expression on hepatocytes and bile duct epithelium, respectively. These findings show definitively that ductular hepatocytes are intermediate cells bearing morphologic and phenotypic characteristics of both hepatocytes and bile duct epithelium. The presence of these cells indicates the existence of facultative stem cells in the adult mammalian liver.

Neutral glycolipids of migrating and nonmigrating rabbit corneal epithelium in organ and cell culture

It is generally believed that plasma membrane glycoconjugates influence corneal epithelial cell migration after wounding. Previous studies have focused on the role of glycoproteins in this event. The present study was designed to determine whether migration-specific glycolipids are synthesized by epithelium of healing rabbit corneas. Migrating and nonmigrating rabbit corneal epithelia were incubated with [3H]-galactose in an organ culture system for 48 hr. At the end of the labeling period, a neutral glycosphingolipid (NGSL) fraction was isolated from each radiolabeled epithelium and was analyzed by thin-layer chromatography. Three radiolabeled NGSL components, M1, M2 and M3 (M1-M3), were present in significantly higher amounts in the extracts of migrating as compared to nonmigrating epithelium. Chromatographic mobility of M3 was similar to that of a standard glucosylceramide; M1 and M2 migrated more slowly than M3. For characterization of the migration-related NGSL, a large amount of the starting material is required. Experiments, therefore, were conducted using cell cultures of rabbit corneal epithelium. Confluent (nonmigrating) cell cultures of rabbit corneal epithelium were found to synthesize either minimal or undetectable amounts of NGSL M1-M3. In contrast, we found that the NGSL M1-M3 are synthesized as major components by sparse (migrating) corneal epithelial cell cultures. Components M1-M3 were synthesized as major components by sparse cultures even in the absence of cell mitosis. This suggests that the increased synthesis of components M1-M3 by sparse cell cultures may be related to cell migration rather than cell mitosis.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Multiple sequential periods of DNA synthesis and quiescence in primary hepatocyte cultures maintained on the DMSO-EGF on/off protocol

Repeated periods of DNA synthesis activity (each period consisting of two to three cycles) separated by intervals of quiescence in primary rat hepatocytes can be stimulated by sequential addition and removal of 2% dimethyl sulfoxide (DMSO) in the presence of epidermal growth factor (EGF). Hepatocytes can be kept in nonproliferating cultures for 7 days in media supplemented with 2% DMSO and EGF. If DMSO is removed while EGF is maintained, rat and human hepatocytes enter a 3 to 4 day period of DNA synthesis that declines rapidly by days 4 and 5. If DMSO is reintroduced into cultures at that point, kept on for 3 more days and removed again, hepatocytes reenter into proliferation with another self-limited response of 3 to 4 days. Similar phenomena can seen with hepatocytes maintained in the presence of 3 mM phenobarbital. These protocols demonstrate that loss of responsiveness to mitogens in primary hepatocyte cultures is not an irreversible process. They also raise the possibility that signals for termination of DNA synthesis in hepatocytes emanate from hepatocytes themselves. These studies also suggest for the first time the possibility of designing in vitro systems that will allow clonal expansion of differential hepatocytes.

NH2-terminal amino acid sequence of rabbit hepatopoietin A, a heparin-binding polypeptide growth factor for hepatocytes

Hepatopoietin A (HPTA) is an acidic heparin-binding polypeptide growth factor for hepatocytes with properties distinct from other known heparin-binding growth factors. HPTA is a heterodimer consisting of a heavy and a light polypeptide chain with Mr of 70,000 and 35,000 respectively. HPTA is a complete mitogen for hepatocytes in that it stimulates DNA synthesis in hepatocytes maintained in serum-free medium. Its complete purification from rabbit serum or human plasma was reported by us elsewhere (R. Zarnegar and G. Michalopoulos, 1989). In the present communication we report the N-terminal amino acid sequence of the HPTA light chain up to 24 residues (VVNGKPTRTNVGRMVSLKYRNKHI) and show that this sequence is unique and not related to any other proteins or growth factors based on computer search analysis. We have also raised antiserum against a synthetic peptide corresponding to the sequence of N-terminal amino acids residues 1 to 24, which recognizes the whole HPTA molecule. This antiserum as well as oligonucleotide probes corresponding to the N-terminal amino acid sequence of HPTA can be used as probes to identify tissue(s) of origin of this growth factor and assist in molecular cloning of its gene.

Purification and biological characterization of human hepatopoietin A, a polypeptide growth factor for hepatocytes

We have previously reported the presence of a high molecular weight polypeptide growth factor in the plasma of normal human or rat serum which stimulates DNA synthesis in primary cultures of normal rat hepatocytes. We referred to this activity as hepatopoietin A (HPTA) (Michalopoulos, G., Houck, K. A., Dolan, M. L., and Luetteke, N. C. Control of hepatocytes replication by two serum factors. Cancer Res., 44: 4414-4419, 1984; Thaler, J., and Michalopoulos, G. Hepatopoietin A. Partial characterization and trypsin activation of a hepatocyte growth factor. Cancer Res., 45: 2545-2549, 1985). At that time, however, complete purification of this growth factor had not been achieved. In the present report we describe the steps required for complete purification of HPTA from human plasma or rabbit serum. The purification involved sequential ammonium sulfate precipitation, heparin-affinity chromatography, anion-exchange high-performance liquid chromatography (HPLC), and reversed phase HPLC. The final purified product is a heterodimer consisting of a heavy and a light polypeptide chain with molecular weights of 70,000 and 35,000, respectively, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis under reducing conditions. Under nonreducing conditions, however, the purified HPTA migrated as a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis corresponding to a molecular weight of 69,000. The mitogenic activity of HPTA was associated with this band when it was eluted from unstained sodium dodecyl sulfate-polyacrylamide gels. Gel filtration HPLC under neutral isotonic conditions indicated that HPTA tends to form aggregates with molecular weights of greater than 300,000. Chromatofocusing indicated that HPTA is an acidic protein with an isoelectric point value of about 5.5. The mitogenic activity of HPTA was sensitive to heat, trypsin, and 2-mercaptoethanol, but relatively resistant to exposure to 1 N acetic acid, 2 M guanidine-HCl, and 0.1% sodium dodecyl sulfate. The stimulation of DNA synthesis induced by HPTA was totally abrogated by transforming growth factor-beta and markedly reduced in the presence of heparin. We present biochemical as well as biological evidence that HPTA is a hepatocyte growth factor distinct from other known polypeptide mitogens such as epidermal growth factor, transforming growth factor-alpha, platelet-derived growth factor, fibroblast growth factor, and thrombin.

Use of primary cultures of human hepatocytes in toxicology studies

Often results from toxicological studies using rodent models cannot be directly extrapolated to probable effects in human beings. In order to examine the genotoxic potential of chemicals in human liver cells, a human hepatocyte DNA repair assay has been defined. Procedures were optimized to prepare primary cultures of human hepatocytes from discarded surgical material. On eight different occasions human hepatocyte cultures of sufficient viability to measure DNA repair were successfully prepared by collagenase perfusion techniques. The cells were allowed to attach to plastic or collagen substrata for periods of 1.5 to 24 h and subsequently incubated with [3H]thymidine and test chemicals for periods of 18 to 24 h. Chemically induced DNA repair, measured as unscheduled DNA synthesis, was quantitated autoradiographically. The following compounds were tested: 2-acetylaminofluorene, aflatoxin B1, 2-aminobenzyl alcohol, aniline, benzo(a)pyrene, carbon tetrachloride, chloroform, 2,4-diaminotoluene, 2,6-diaminotoluene, di(2-ethylhexyl)phthalate, dimethylnitrosamine, 1,6-dinitropyrene, 2,4-dinitrotoluene, 2,6-dinitrotoluene, methyl chloride, 5-methylchrysene, mono(2-ethylhexyl)phthalate, 2-methyl-2-P-(1,2,3,4-tetrahydro-1-naphthyl)phenoxypropionic acid (nafenopin), beta-naphthylamine, nitrobenzene, 2-nitrobenzyl alcohol, 2-nitrotoluene, 2,3,7,8-tetrachlorodibenzo-p-dioxin, unleaded gasoline, and 4-chloro-6-(2,3-xylidino)-2-pyrimidinylthioacetic acid (Wy-14,643). In only one of eight cases did some of the chemicals generally regarded as genotoxic fail to give a positive response. For purposes of comparison, all test chemicals were evaluated in the in vitro rat hepatocyte DNA repair assay. Individual-to-individual variation in the DNA repair response was far greater for the human cultures than for cultures derived from rats. For only three chemicals was there a qualitative difference in the response between the rodent and the human cells; beta-naphthylamine was positive in the rat but in none of the human cultures examined, whereas the opposite was seen for 2,6-diaminotoluene and 5-methylchrysene. Clofibric acid, mono(2-ethylhexyl)phthalate, and Wy-14,643 induced enzymes indicative of peroxisomal proliferation in primary rat hepatocyte cultures, but not in two human hepatocyte cultures. These results indicate that, in general, the in vitro rat hepatocyte DNA repair assay is a valid model for predicting potential genotoxic effects in human beings. However, rodent hepatocytes may not be appropriate for assessing the potential of chemicals to elicit nongenotoxic effects in human beings such as the induction of hepatocyte peroxisomal proliferation.

Induction of glutamine synthetase and transient co-expression with carbamoylphosphate synthetase in hepatocytes transplanted into fat pads of syngeneic hosts

Isolated rat hepatocytes were transplanted into the interscapular and both anterior lateral fat pads of hepatectomized syngeneic rats. At various time points following transplantation, the fat pads were removed, fixed and embedded in paraffin. Serial sections were stained for glutamine synthetase (GS) and carbamoylphosphate synthetase (CPS) using specific antisera and the PAP technique. The initially low fraction of GS+-heptatocytes remained low up to the fourth day, then increased strikingly up to almost 100% and declined gradually after the 14th day. In contrast, the number of CPS+-cells declined continuously to about 30% after 28 days. If the animals were exposed to CCl4 prior to the isolation of the hepatocytes in order to reduce the number of GS+-cells in the initial cell suspension similar results were obtained and no difference in the probability of the colony formation was noted between this and the normal hepatocyte suspensions indicating that the appearance of the GS+-phenotype was not due to a selective survival of these cells. Analysis of the staining intensity of the transplanted hepatocytes revealed the appearance of two populations of GS+-hepatocytes, one with a strong and one with a weak staining, during the course of formation of larger nodules, while only a single weakly stained population could be discerned with respect to the staining for CPS. These results demonstrate that all hepatocytes or at least their descendents can be induced to express GS by the environmental conditions of the fat pads, and that GS and CPS can be co-expressed with an apparently reciprocal relationship.

Metabolism of acetylaminofluorene in primary cultures of human hepatocytes: dose-response over a four-log range

The metabolism of acetylaminofluorene (AAF) in human hepatocyte cultures from different donors was investigated for a four-log concentration range (500, 50, 5.0 and 0.5 microM) or at 3, 8 and 24 h at 500 microM. The metabolite profile was dependent on the concentration to which the cells were exposed. The hepatocyte cultures varied in the degree to which they metabolized AAF predominantly because of different levels of deacetylation. Ring-hydroxylation was the predominant pathway for AAF metabolism at low concentrations (5.0 and 0.5 microM) but saturated in three of four human cases at high concentrations of AAF; N-hydroxylation did not appear to become saturated. Human hepatocytes catalyzed the covalent binding of AAF metabolites to their DNA. A linear increase in DNA binding was observed when increasing concentrations of AAF were added to hepatocyte cultures; however, the increase in AAF metabolites binding to DNA was not proportional to the dose. While the concentration of AAF in the media was increased over a four-log range, both the production of N-hydroxy AAF and binding of metabolites to hepatocellular DNA increased over approximately a three-log range. These results with cultured human hepatocytes indicate that the pathways of AAF metabolism are qualitatively similar to those identified in experiments with rat hepatocytes as well as experiments conducted in vivo with human subjects. These studies confirm that the cultured human hepatocyte is a useful model for the investigation of human xenobiotic metabolism and indicate that the concentration of the xenobiotic used in the experiments is an important determinant of the metabolitic profile produced.

Norepinephrine modulates the growth-inhibitory effect of transforming growth factor-beta in primary rat hepatocyte cultures

TGF-beta is a potent inhibitor of EGF-induced DNA synthesis in primary rat hepatocyte cultures. Norepinephrine (NE) was shown to modulate this inhibition of DNA synthesis. It produced a five-fold increase, from 2.8 pM to 14.4 pM, in the ID50 for TGF-beta. The effect was dose-dependent and was significant at concentrations of 10(-6)M NE and greater. The modulation by NE was mediated by the alpha 1-adrenergic receptor as shown by the ability of the alpha 1 antagonist prazosin to block the activity. This effect might be important during liver regeneration in allowing escape of hepatocytes from negative growth control exerted by TGF-beta.

Early events in the regulation of hepatocyte DNA synthesis: the role of alpha-adrenergic stimulation

The role of adrenergic agents in DNA synthesis was investigated in two models of stimulated hepatocyte growth: in vitro primary serum-free cultures of adult parenchymal hepatocytes, and in vivo liver regeneration after two-thirds partial hepatectomy. In both systems the alpha 1-adrenergic receptor appeared to be involved in mediating stimulatory effects. In primary hepatocyte cultures norepinephrine acted via this receptor to enhance the DNA synthesis stimulated by epidermal growth factor (EGF), and heterologously downregulated EGF receptors. In liver regeneration the administration of an alpha 1 blocking agent interfered with the first wave of regenerative DNA synthesis, and this effect was preceded by an elevation in EGF receptor number. Measurements of plasma catcholamines demonstrated that elevated levels of norepinephrine and epinephrine were in circulation within 2 h after partial hepatectomy. Surgical hepatic sympathectomy also interfered with early liver regeneration, suggesting that locally delivered adrenergic agents are important to initiation of DNA synthesis. These data suggest that stimulation at the alpha 1-adrenergic receptor is among the early signals for liver regeneration and that heterologous regulation of EGF receptors, similar to that observed in vitro, may be a part of the regenerative response.

Alpha 1-adrenergic effects and liver regeneration

The effects of several treatments involving alpha-adrenergic mechanisms upon the early stages of rat liver regeneration were examined. Catecholamine concentrations in rat plasma were measured at various times after hepatectomy and were found to be elevated relative to those in plasma from sham-operated rats. Surgical hepatic denervation or injection of an alpha 1-adrenergic receptor antagonist (prazosin) reduced incorporation of [3H]thymidine into liver DNA during the first 24 hr after partial hepatectomy. Chronic guanethidine injections (3 to 6 weeks) reduced liver catecholamine levels, but did not affect its ability to regenerate. The inhibition of regenerative DNA synthesis by prazosin was preceded by an alteration in the binding of epidermal growth factor to regenerating liver, which was apparently the result of an increased number of epidermal growth factor receptors. Thus, alpha 1-adrenergic blockade, which affects both epidermal growth factor receptor binding and subsequent DNA synthesis in hepatocyte primary cultures, can also modulate these processes during liver regeneration in vivo.

Induction of sister chromatid exchanges in cultured adult rat hepatocytes by directly and indirectly acting mutagens/carcinogens

Primary cultures of adult rat hepatocytes were tested for their suitability to assess sister chromatid exchange (SCE)-inducing DNA damage produced by both directly and indirectly acting mutagens/carcinogens. Compared to other genotoxicity assay systems which utilize the metabolizing activity of liver microsomes, this system is at least 1-2 orders of magnitude more sensitive. The approximate drug concentrations leading to a doubling of control SCE levels were 2.5 X 10(-4) M for cyclophosphamide, 4.5 X 10(-5) M for dimethylnitrosamine, 2.5 X 10(-6) M for N-methyl-N-nitro-N-nitrosoguanidine, 2 X 10(-10) M for aflatoxin B1 (AFB1) and 30 mJ for u.v. The most potent inducer of SCE proved to be AFB1, leading to a significantly elevated level of exchanges at a concentration of 10(-12) M. The increased background SCE levels observed (0.75 SCE/chromosome) appears to reflect the sensitivity of hepatocytes to SCE-inducing DNA damage resulting from the dietary intake of mutagenic/carcinogenic compounds. In view of the high sensitivity and versatility of this genotoxicity assay system, it will be of use for the detection of the low levels of mutagenic/carcinogenic compounds found in the environment.

Effects of EGF and calcium on adult parenchymal hepatocyte proliferation

Adult rat hepatocytes were grown in serum-free medium containing 0.05-4 mM Ca++ and 40 ng/ml EGF. After 48 hours of cultivation the mitotic index and the percentage of second division metaphases were determined. The results demonstrated a maximum proliferation response to EGF at a Ca++ concentration of 0.4 mM. With lower and higher external Ca++ concentrations the fraction of cells undergoing more than one cell division decreased. At lower Ca++ concentrations this decrease appears to result from a reduced viability. In contrast, the low response to EGF at higher Ca++ concentrations--especially in the physiological range--may reflect the influence of Ca++ on the state of hepatocyte differentiation.

Metabolism of benzo[a]pyrene in primary cultures of human hepatocytes: dose-response over a four-log range

Cultures of isolated human hepatocytes from three different human liver specimens were exposed for 24 h to media containing [3H]benzo[a]pyrene (BP) (0.1, 1.0, 10, 100 microM). The cells and media were harvested and extracted. Subsequent incubations of the aqueous phase with beta-glucuronidase and aryl sulfatase, followed by acetone/ethyl acetate extraction, were utilized to determine specific conjugation. Separation of the BP and its metabolites in the residues of the extracts was achieved by h.p.l.c. The capacity of human hepatocytes to metabolize BP was not saturated at up to 100 microM of BP, and the predominant metabolites produced were eluted in the void volume and were a mixture of highly polar BP forms. The next four most prevalent forms of BP metabolites were the 3-hydroxy BP, BP-4,5-dihydrodiol, BP-9,10-dihydrodiol, and BP-7,8-dihydrodiol. These metabolites all increased nearly linearly with dose. Conjugation varied for each different case, ranging from 31 to 91%, but a general trend clearly appeared; if beta-glucuronidation decreased, then sulfation increased and vice versa. BP metabolite binding to DNA was associated with the amount of unconjugated BP-7,8-dihydrodiol metabolite. BP metabolite binding to DNA was nearly linear from 0.1 to 10 microM BP; however, binding to DNA at 100 microM increased 64- to 844-fold over the binding occurring at 10 microM. Thus, human hepatocytes have a strong tendency to form highly polar BP metabolites, and total binding of BP to DNA over a four-log dose range is much less at 0.1-10 microM than one would predict from extrapolation from the high concentration (100 microM).

Kidney proximal tubular cells isolated by collagenase perfusion grow in defined media in the absence of growth factors

Cells from kidney proximal tubules have been successfully isolated, characterized, and cultured from male Fischer 344 rats between 150-400 g using a two-step collagenase perfusion. The cells undergo high levels of DNA synthesis and mitosis in both serum free media (with an without hormone supplementation) and media containing 10% fetal bovine serum. Confluent monolayers were observed between 5 to 7 days after seeding 2 X 10(5) cell/35 mm collagen-coated plate. Approximately 50% of the total kidney and 70% of the cortex was isolated using this technique. The viability of the isolated tubules was 75 +/- 8% and the estimated number of viable cells was 12 +/- 3 X 10(6) cells. At the time of isolation greater than 90% of the isolated tubules and cells were positive for gamma glutamyltransferase (GGT), periodic acid-schiff (PAS), and glucose-6-phosphatase (G-6-Pase). Both GGT and G-6-Pase decreased rapidly during the first 3 days in primary culture as assessed by histochemistry. Ultrastructurally the isolates consisted of cells with numerous microvilli and mitochondria. The size and number of microvilli decrease rapidly in primary culture. The morphologic and biochemical evidence suggests that the primary isolates and cultures are proximal tubular in origin.

Changes in the pattern of aldehyde dehydrogenase activity in primary and metastatic adenocarcinomas of the human colon

The activity of aldehyde dehydrogenase (ALDH) was measured in primary and metastatic human colonic adenocarcinomas. The enzyme was determined with either propionaldehyde and NAD (P-NAD) or with benzaldehyde and NADP(B-NADP). Primary colonic adenocarcinomas had levels of P-NAD activity similar to those of the adjacent normal mucosa, but relatively higher B-NADP activity. Also the metastatic colonic adenocarcinomas of the liver had lower P-NAD and higher B-NADP activity than the normal hepatic parenchyma. The level of ALDH was in general lower in the normal colonic mucosa, when compared to the liver. Histochemical staining of cryostat tissue sections revealed that the enzyme is exclusively confined to the epithelial cells of the glandular ducts of the colonic mucosa. This may explain, along with the significant anaplastic changes of the mucosa, the variation of ALDH activity detected in the homogenates of the primary and metastatic adenocarcinomas. However, the ratio of B-NADP activity in the adenocarcinomas versus the adjacent normal tissues was constantly and significantly high.

Effect of phenobarbital and 3-methylcholanthrene on aldehyde dehydrogenase activity in cultures of HepG2 cells and normal human hepatocytes

Aldehyde dehydrogenase (ALDH) activity was measured in primary cultures of normal human hepatocytes and of the human hepatoma cell line HepG2 after application of phenobarbital (PB) or 3-methylcholanthrene (MC) for 5 days. Treatment with PB alone resulted in a significant increase in both protein and DNA content at concentrations of 2 and 3 mM. Treatment with MC at a concentration as low as 5 microM led to a significant loss of cells when it lasted more than 5 days. Concentrations of 3-5 mM of PB in the media of HepG2 cell cultures caused a 2-fold enhancement of the activity of ALDH, as measured with NAD and propionaldehyde (P/NAD) or benzaldehyde (B/NAD). On the other hand, MC-treated cultures (5 microM) showed a 20-fold increase in enzyme activity measured with NADP and benzaldehyde (B/NADP), and a 2-fold increase in B/NAD activity. Combined treatment with both PB and MC led to an effect of dynamic synergism as far as B/NAD and B/NADP activities are concerned, suggesting a metabolite of MC as the mediator for the increase of ALDH activity. Normal human hepatocytes in primary cultures responded to PB (3 mM) in a similar way as HepG2 cells as far as DNA and protein content and ALDH activity are concerned. It is concluded, that HepG2 hepatoma cells behave similar to the normal hepatocytes in terms of ALDH regulation and can be used for studies on the activity of ALDH as modified by added xenobiotics.

Phenobarbital enhances the aldehyde dehydrogenase activity of rat hepatocytes in vitro and in vivo

Aldehyde dehydrogenase (ALDH) was measured in primary cultures of hepatocytes obtained with collagenase perfusion from livers of Long-Evans rats. After seven days in culture, basal ALDH activity, protein content and DNA content are significantly decreased. Exposure of the cultures to phenobarbital (PB, 3 mM in the media) does not prevent the decrease of DNA content, although it keeps protein at relatively higher levels. The activity of ALDH is not only preserved, but also significantly enhanced, when propionaldehyde, phenylacetaldehyde, benzaldehyde and D-glucuronolactone are used as substrates and NAD as the coenzyme. A relative increase of activity is also noted when ALDH is measured with benzaldehyde and NADP. Treatment of Long-Evans animals with PB (1 mg/ml, in drinking water for 2 weeks) leads to similar relative increases of the ALDH activity. In absolute values, however, enzyme activities found after in vivo treatment with PB are higher, compared to those obtained after in vitro exposure. These results show that ALDH activity can be greatly enhanced by PB in primary hepatocyte cultures, free from any indirect endogenous influences.

Enhancement of the clonability of adult parenchymal hepatocytes with the liver tumor promoter phenobarbital

An in vivo clonogenic assay system was utilized to investigate the effect of the tumor promoter, phenobarbital (PB), on adult parenchymal hepatocyte proliferation. Enzymatically dispersed hepatocytes from female Fischer 344 rats were injected into the interscapular and mammary fat pads of isogeneic recipient animals where they proliferate to form hepatocyte colonies within 3 weeks. The number of hepatocytes required to form a colony in 50% of the transplantation sites (LND50) was 23 700 cells and 520 cells when normal adult liver cells were injected into non-hepatectomized and 2/3 hepatectomized normal recipient animals, respectively. Thus, a partial hepatectomy increased the hepatocyte clonogenicity by a factor of 40. A 2-week pre-treatment of both the donor and recipient animals with PB (0.1% in the drinking water) significantly increased the clonogenicity of the liver cells when transplanted into non-hepatectomized (15-fold) and 2/3 hepatectomized (2-fold) animals. However, PB treatment of the recipient animals was not required for the majority of this mitogenic effect since the clonability of PB-treated donor cells was increased (92% of the maximum stimulation observed) even when they were transplanted into untreated control animals. Furthermore, the PB-induced effect on hepatocyte clonability was reversible since the removal of PB from the donor animals 2 weeks prior to their use reduced the clonability of the hepatocytes (LND50 = 20,500 cells) to that observed for cells which were never exposed to PB. These results are consistent with the postulate that rather than PB being directly mitogenic, it primarily increases the clonability of adult parenchymal hepatocytes by inducing a reversible cellular alteration which enhances their responsiveness to endogenous growth stimuli.