Cell types in rat liver cultures: their identification and isolation

Cell-specific elevation of Runx2 promotes hepatic infiltration of macrophages by upregulating MCP-1 in high-fat diet-induced mice NAFLD

OBJECTIVE

We have demonstrated runt-related transcription factor 2 (Runx2) plays important role in atherosclerosis. It has been indicated that atherosclerosis shares the similar histopathology with nonalcoholic steatohepatitis (NASH), a progressive stage of nonalcoholic fatty liver disease (NAFLD), on macrophages infiltration. However, the function of Runx2 in NAFLD is completely unknown. Here, we investigated the underlying mechanism of Runx2 triggering macrophages infiltration in the development of NAFLD.

METHODS

Mice were fed with high-fat diet (HFD) for a long time. Histopathologic features, macrophages infiltration, expression of monocyte chemotactic protein 1 (MCP-1), and Runx2 were, respectively, analyzed in vivo. Lentivirus or short interfering RNA were transfected in murine hepatic stellate cells (HSCs) and the transwell assay was performed to verify the contribution of Runx2 for macrophages migration in vitro.

RESULTS

Long-term treatment with HFD induced the progression of NAFLD, and NASH was initiated from 8 months on diet. HFD increased the expression of F4/80 upon HFD feeding, indicated HFD promotes hepatic infiltration of macrophages in NAFLD. In addition, HFD upregulated the expression of MCP-1 and Runx2 during NAFLD development. Unexpectedly, Runx2 upregulation is cell-type depended in NAFLD, and only abundantly elevated in activated HSCs. Furthermore, we found that Runx2 could increase or decrease the expression of MCP-1 in HSCs, and regulate macrophages migration by influencing MCP-1 production in vitro.

CONCLUSIONS

Our results give evidence that the upregulation of Runx2 specific in activated HSCs promotes hepatic infiltration of macrophages by increasing MCP-1 expression in NAFLD, which reveals a novel mechanism and provides a cell-specific therapeutic target for NAFLD.

Hepatic Cells via Cava Vein Can Influence Allogenic Islet Rat Transplantation

We have reported, previously, some effect of allogenic hepatic cells for islet tolerance when they are injected mixed (hepatic cells and islets) in different proportions via portal vein, in diabetic Wistar rats. Now we have studied the role of allogenic hepatic cells injected sequentially 15 min before islets, comparing via the portal vein (A and B groups) and via the cava vein (C and D groups) with a control group of islets alone. The allogenic islets were always injected via portal vein, in similar conditions, while the ratio of hepatic cells/islets was 100:1 (A, C groups) or 200:1 (B, D groups). Islets and hepatic cells were obtained from several different rats. The transplanted rats were observed during 30 days and results compared among the different rat groups: porta-porta (P/P), cava-porta (C/P), and control group. Statistically, a significant interaction between type of transplant and proportion of hepatic cells was observed. Also, C plus D groups showed statistical difference with the control group (p < 0.017) and also all the groups together (p < 0.047). These results suggest that hepatic cells can induce, in some cases, islet graft prolongation in Wistar rats. Better results were obtained when hepatic cells were injected via the cava vein than via the portal vein. Because we used a liver cell suspension integrated for several kinds of cells, the study does not clarify if this effect can be related to some specific hepatic cell subpopulation. To confirm the results and to determine if the hypothetical mechanism can be attributed to a block of the immune system or to some factor secreted by hepatic cells, more studies must be performed.

Novel aspects of the liver microenvironment in hepatocellular carcinoma pathogenesis and development

Hepatocellular carcinoma (HCC) is a prevalent primary liver cancer that is derived from hepatocytes and is characterised by high mortality rate and poor prognosis. While HCC is driven by cumulative changes in the hepatocyte genome, it is increasingly recognised that the liver microenvironment plays a pivotal role in HCC propensity, progression and treatment response. The microenvironmental stimuli that have been recognised as being involved in HCC pathogenesis are diverse and include intrahepatic cell subpopulations, such as immune and stellate cells, pathogens, such as hepatitis viruses, and non-cellular factors, such as abnormal extracellular matrix (ECM) and tissue hypoxia. Recently, a number of novel environmental influences have been shown to have an equally dramatic, but previously unrecognized, role in HCC progression. Novel aspects, including diet, gastrointestinal tract (GIT) microflora and circulating microvesicles, are now being recognized as increasingly important in HCC pathogenesis. This review will outline aspects of the HCC microenvironment, including the potential role of GIT microflora and microvesicles, in providing new insights into tumourigenesis and identifying potential novel targets in the treatment of HCC.

Involvement of ERK1/2 signaling in proliferation of eight liver cell types during hepatic regeneration in rats

It has been well established that ERK1/2 signaling, often subdivided into nine types of pathways, can regulate the hepatocyte proliferative response during liver regeneration. However, the effect of ERK1/2 signaling on the proliferation of other hepatic cell types remains unclear. We isolated and purified 8 liver cell types at 10 time points after 2/3 hepatectomy in adult rats. For each cell type, mRNA expression changes for ERK1/2 signaling-involved genes were monitored up to 168 h, using microarrays. Real-time PCR assays were performed for array data verification. The expression levels of these genes varied considerably between different cell types. Integrating microarray results with gene synergical analysis, at the priming phase, activation of integrin/Grb2/Ras pathway in hepatocytes apparently contributed to G0/G1 transition. Two other pathways, G-protein/EPAC/Rap1 and G-protein/PKA/Rap1, were stimulated in hepatic stellate cells, while RTK/PKC/Ras and RTK/Grb2/Ras were stimulated in Kupffer cells. At the progressive phase, the ERK1/2 pathway is involved in hepatocyte replication; three pathways, namely Ca(2+)/PKC/Ras, RTK/Grb2/Ras and G-protein/EPAC/Rap1, were found to play roles in biliary epithelial cell proliferation, while RTK/PKC/Ras and RTK/Grb2/Ras were involved in Kupffer cell proliferation, and G-protein/PKC/Ras in pit cell proliferation. At the terminal phase, the promotive effect of the ERK1/2 pathway on replication of hepatocytes, biliary epithelial cells, oval cells, hepatic stellate cells, Kupffer cells, and dendritic cells was considerably reduced, possibly due to their differentiation at the end of regeneration. G-protein/PKC/Ras, integrin/Grb2/Ras and G-protein/ PKA/Rap1 pathways were active in sinusoidal endothelial cells, perhaps to aid in their proliferation. We conclude that ERK1/2 has a signaling role in the regulation of proliferation of 8 cell types during liver regeneration process.

The role of Kupffer cells in rat liver regeneration revealed by cell-specific microarray analysis

Liver regeneration after partial hepatectomy is a process with various types of cells involved. The role of Kupffer cells (KCs) in liver regeneration is still controversial. In this study we isolated KCs from regenerating liver and conducted cell-specific microarray analysis. The results demonstrated that the controversial role of KCs in liver regeneration could be explained with the expression patterns of TGF-α, IL-6, TNF, and possibly IL-18 during liver regeneration. IL-18 may play an important role in negative regulation of liver regeneration. The functional profiles of gene expression in KCs also indicated that KC signaling might play a negative role in cell proliferation: signaling genes were down regulated before cell division. Immune response genes in KCs were also down regulated during liver regeneration, demonstrating similar expression profiles to that of hepatocytes. The expression patterns of key genes in these functional categories were consistent with the temporal functional profiles.

Microarray approach reveals the relevance of interferon signaling pathways with rat liver restoration post 2/3 hepatectomy at cellular level

The immunomodulator interferons are assumed not only to fight tumor progress but also to inhibit liver regeneration by inactivating Kupffer cells. The potential mechanism is still poorly characterized. In particular, the relevance of interferon signaling to liver regeneration at cellular level still remains unknown. In this study, 8 types of rat liver cells from the regenerating liver at 10 recovery time points were separately isolated by percoll density gradient centrifugation and immunomagnetic bead. Transcription profiles of interferon-signaling pathway genes in each cell type along the time course of liver restoration were detected using Rat Genome 230 2.0 Array covering about 12,727 known genes. The chip data demonstrated that hepatocyte mainly up-regulated the IFN-alpha1-mediated JAK/STAT pathway genes; biliary epithelial cell mostly expressed the IFN-beta1-mediated p38 MAPK pathway genes; while the IFN-gamma-activated JAK/STAT pathway genes were down-regulated particularly in HSC, KC, and DC during liver regeneration. It is inferred that STAT3, in contrast to STAT1, seemingly takes a more active role in IFN-alpha1-mediated JAK/STAT pathway in hepatocyte; IFN-beta1-mediated p38 MAPK pathway possibly to some extent affects inflammation and apoptosis of biliary epithelial cell during liver regeneration; IFN-gamma-induced JAK/STAT pathway may be associated with the attenuated apoptosis induction in HSC, KC, and DC. Our data suggested that a better understanding about how interferon signals at liver cell level might be helpful in developing an effective approach to protecting against the inhibition of regeneration.

Cholangiocyte anion exchange and biliary bicarbonate excretion

Primary canalicular bile undergoes a process of fluidization and alkalinization along the biliary tract that is influenced by several factors including hormones, innervation/neuropeptides, and biliary constituents. The excretion of bicarbonate at both the canaliculi and the bile ducts is an important contributor to the generation of the so-called bile-salt independent flow. Bicarbonate is secreted from hepatocytes and cholangiocytes through parallel mechanisms which involve chloride efflux through activation of Cl^- channels, and further bicarbonate secretion via AE2/SLC4A2-mediated Cl^-/HCO₃^- exchange. Glucagon and secretin are two relevant hormones which seem to act very similarly in their target cells (hepatocytes for the former and cholangiocytes for the latter). These hormones interact with their specific G protein-coupled receptors, causing increases in intracellular levels of cAMP and activation of cAMP-dependent Cl^- and HCO₃^- secretory mechanisms. Both hepatocytes and cholangiocytes appear to have cAMP-responsive intracellular vesicles in which AE2/SLC4A2 colocalizes with cell specific Cl^- channels (CFTR in cholangiocytes and not yet determined in hepatocytes) and aquaporins (AQP8 in hepatocytes and AQP1 in cholangiocytes). cAMP-induced coordinated trafficking of these vesicles to either canalicular or cholangiocyte lumenal membranes and further exocytosis results in increased osmotic forces and passive movement of water with net bicarbonate-rich hydrocholeresis.

Long-term culture of cholangiocytes from liver fibro-granulomatous lesions

BACKGROUND

Extensive bile duct proliferation is a key feature of the tissue reaction to clinical and experimental forms of liver injury. Experimental infection of mice by Schistosoma mansoni is a well-studied model of liver fibrosis with bile duct hyperplasia. However, the regulatory mechanisms of bile duct changes are not well understood. In this study we report the reproducible isolation of long-term cultures of cholangiocytes from mice livers with schistosomal fibrosis.

METHODS

We have isolated a cholangiocyte cell line from Schistosoma-induced liver granulomas using a combination of methods including selective adhesion and isopyknic centrifugation in Percoll.

RESULTS

The cell line was characterized by morphological criteria in optical and transmission electron microscopy, ability to form well differentiated ductular structures in collagen gels and by a positive staining for cytokeratin 18 and cytokeratin 19. To our knowledge, this is the first murine cholangiocyte cell line isolated from schistosomal fibrosis reported in the literature.

CONCLUSION

After 9 months and 16 passages this diploid cell line maintained differentiated characteristics and a high proliferative capacity. We believe the method described here may be a valuable tool to study bile duct changes during hepatic injury.

The in vitro differentiating capacity of nonparenchymal epithelial cells derived from adult porcine livers

Specific nonparenchymal epithelial cell (NPEC) clusters derived from normal adult porcine livers demonstrate a characteristic developmental pattern in the presence of other types of nonparenchymal cells in vitro. This pattern includes scattering, colonial growth, and an emergence of duct-like structures (DLSs) in the colonies. It has been confirmed that 96% of the scattered cell clusters in these cultures develop into colonies containing DLSs. In this study, we examine the differentiation of NPEC clusters using the scattered formation as a marker of the DLS-emerged colonies. We report that the NPECs expressed albumin, alpha-fetoprotein, transferrin, cytokeratin (CK) 18, CK7, and c-met, but not alpha-1-antitrypsin (AAT), at the scattering stage. In addition, at the same stage, NPECs expressed oval-cell-related markers such as OV6, but not biliary epithelial cell (BEC) markers such as gamma-glutamyltransferase, CK19, and CK14. At the DLS emerging stage, hepatocyte markers, including AAT, were detectable in the cells either at the periphery of colonies or in the cells surrounded by the DLSs. On the other hand, the cells constituting DLSs expressed BEC markers, suggesting a bile duct nature of the DLSs. Furthermore, the cells in the colonies possessed an ultrastructural appearance of differentiated hepatocytes and BECs. These results suggest that certain NPECs are bipotent, and that, in culture, they mimic hepatoblast development in vivo.

Maturation-dependent gene expression in a conditionally transformed liver progenitor cell line

We have isolated a conditionally transformed liver progenitor cell line with phenotypic similarities to both hepatoblasts (bipotent embryonic liver cells that give rise to hepatocytes and intrahepatic biliary epithelial cells) and liver epithelial cells (primitive hepatic cells isolated from adult livers capable of generating both hepatocytic and biliary lineages). Cell line L2039 was derived from E14 fetal mouse liver after transformation with temperature-sensitive SV-40 large T antigen. At 33 degrees C, these cells have an epithelial morphology with a high nucleocytoplasmic ratio and express both hepatocytic and biliary genes, including albumin, alpha-fetoprotein, glutamine synthetase, insulinlike growth factor II receptor, fibronectin and laminin, and cytokeratins 8 and 19, a set of markers characteristic for hepatoblasts. The presence of cytokeratin 14, vimentin, and several oval-cell antigens link cell line L2039 to nonparenchymal liver epithelial cell populations thought to contain progenitor cells. Serum-free, hormonally defined media conditions and extracellular matrix requirements were determined for growth and differentiation of this cell line. During culture on type IV collagen at 39 degrees C, L2039 cells cease dividing and demonstrate hepatocytic differentiation with the assumption of a hepatocytelike morphology and glucocorticoid-dependent regulation of liver-specific genes, including albumin, alpha-fetoprotein, phosphoenolpyruvate carboxykinase, and liver-enriched transcription factors. The number of albumin-positive cells increases during culture at 39 degrees C, indicating that L2039 cells convert from a prehepatocytic to a hepatocytic phenotype. Under conditions specific for hepatocytic differentiation, C/EBPs were expressed and differentially regulated, with C/EBPbeta and C/EBPdelta upregulated early and C/EBPalpha only slightly expressed after 7 d, indicating that C/EBPalpha may not be a crucial factor in commitment to the hepatocytic phenotype.

Development of dexamethasone-inducible tyrosine aminotransferase activity in WB-F344 rat liver epithelial stemlike cells cultured in the presence of sodium butyrate

Sodium butyrate acts as a differentiation-promoting agent for a wide variety of cell types, including some tumor cell lines. In this study, we examined the effects of sodium butyrate (SB) on the functional differentiation of cultured WB-F344 rat liver epithelial stemlike cells. Treatment of WB-F344 cells with 3.75 mM SB resulted in an inhibition of cellular proliferation, alterations to normal cellular morphology (increased cell size and decreased nuclear/cytoplasmic ratio), and significant increases in cellular protein synthesis. The SB-mediated changes in cell morphology, proliferative status, and protein catabolism were accompanied by development of dexamethasone-inducible tyrosine aminotransferase (TAT) enzyme activity. Culture of WB-F344 cells in growth medium containing SB and dexamethasone (DEX; 1 x 10(-6) M) resulted in greater than sevenfold increase in the basal TAT activity compared with control cultures. An additional sixfold increase in TAT activity was observed when cells cultured in medium containing SB and DEX were exposed to 1 x 10(-7) M DEX during the last 24 hours of culture. The DEX-inducible TAT activity developed by SB-treated WB-F344 cells responded to the modulating effects of insulin and L-tyrosine in a manner that closely resembled that reported for cultured hepatocytes and hepatoma cell lines. These studies show that treatment of WB-F344 rat liver epithelial stemlike cells with the differentiation-promoting agent SB in vitro leads to expression of the differentiation-specific hepatocyte enzyme TAT.

Liver cells can spontaneously resume proliferation in long-term quiescent primary cultures

We report here data on the spontaneous resumption of proliferation in long-term primary cultures and we show that the proliferating areas are neoplastic. Normal rat hepatocytes were explanted in serum-supplemented Ham F12 medium and maintained over 8 months without transfer. The cells remained quiescent for the first 10 weeks and they were not tumorigenic when injected into nude mice. Later, without any modification of the culture conditions or transfer, progressive changes spontaneously occurred. Foci of dividing cells were detected, some displaying gamma-glutamyl-transpeptidase (gamma-GT) activity and F-actin fragmentation. These proliferating foci overcame the quiescent population. When injected into nude mice, the 15-week-old primary cultures were highly tumorigenic, with a 3-6 week latency for tumour formation. Furthermore, a cell line was derived from a primary culture started with a liver carcinogen promoter (biliverdin-enriched medium). This cell line proliferated rapidly and differed from a liver epithelial line, also established from our primary cultures, in its 1 karyotype (hyperploidy and translocation on chromosome 3), 2 requirement for arginine to proliferate, 3 gamma-GT positive reaction correlated to changes in actin fibre pattern, 4 sensitivity to protease inhibitors (i.e. alpha2 macroglobulin, PMSF) and 5 tumorigenicity. Long-term primary cultures and the karyotypically defined cell line are useful tools for further studies on in vitro genetic deviations.

Cytokeratin 14 expression in rat liver cells in culture and localization in vivo

Rat liver epithelial cells (LECs) are non-parenchymal proliferating cells that readily emerge in primary culture and can be established as cell lines, but their in vivo cell(s) of origin is unclear. We reported recently some evidence indicating that the LEC line, T51B, contains two cytokeratins (CKs) equivalent to human CK8 and CK14 respectively. T51B cells also contain vimentin assembled as a network of intermediate filaments distinct from that of the CKs. In the present study, we examined the expression of CK14 gene in various LEC preparations and a Triton-resistant rat skin cytoskeletal fraction, and then assessed its usefulness as an LEC specific marker in the liver. Northern and Western blot analyses with cDNAs and antibodies for CK8, CK14, CK18 and vimentin confirmed that rat hepatocytes express CK8 and CK18 genes only, whereas T51B cells express CK8, CK14 and vimentin genes in the absence of CK18. CK14 was also present in LECs derived as primary from embryonic-day 12 rat liver and secondary cultures from 4-day-old rat liver. Primary cultures of oval cells isolated from 3'-methyl-4-dimethylaminoazobenzene (3'-Me-DAB) treated rat liver (an enriched source of biliary epithelial cells) contained CK14 mRNAs which were slightly shorter than those in LECs. The analyses of CK5 (the usual partner of CK14) gene expression using specific cDNA and antibody clearly demonstrated its absence in LECs. In situ double immunolocalization analyses by laser scanning confocal microscopy showed that CK14 was not present in hepatocytes (HES6+ cells) and was expressed in some biliary epithelial (BDS7+ cells). CK14-positive cells were also found in the Glisson's capsule. However, CK14-positive cells of the portal region were vimentin negative, whereas those of the Glisson's capsule were vimentin positive. Our results suggest that CK14 gene expression is part of the differentiation program of two types of LECs and that this differential CK14 gene expression can be used as a new means to type LECs in culture and in vivo.

Incorporation and metabolic conversion of saturated and unsaturated fatty acids in SK-Hep1 human hepatoma cells in culture

We report here a study of the incorporation and metabolism of various long chain fatty acids in SK-Hep-1 cultured hepatoma cells. Medium supplementation with radiolabelled palmitic, stearic, linoleic, alpha-linolenic and eicosa-8,11,14-trienoic acids (1 microM, 24 H) resulted in an active uptake of each of these precursors by the cultures. Subsequent analysis of the cellular lipids indicated that they exhibit almost all the enzymic activities of polyunsaturated fatty acid metabolism that are characteristic of normal hepatic cells. With respect to the desaturation capacities of this cell line, although alpha-linolenic acid reacted more extensively than did linoleic acid and the conversion of 8,11,14-eicosatrienoic acid by the delta 5 specific enzyme was more avid than had been previously seen in normal rat or human liver: the saturated fatty acids constituted relatively poor substrates, being preferentially chain-elongated rather than (mono) desaturated at the delta 9 position. Analysis of the fatty acid profiles of total cellular lipids and of various lipid subclasses, however, revealed a relative paucity of essential fatty acids when compared with the abundance of endogenous monoenoic acids (particularly oleic). Of the total cellular fatty acids, 58% were present in the form of phospholipids; with 33% of the remaining 42% (i.e., the neutral lipids) being associated with triacylglycerol fraction. Within the total lipids, phosphatidyl-choline and phosphatidyl-ethanolamine were the major sites for the incorporation of all metabolic products derived from the incubated radiolabelled 16- and 18-carbon fatty acid precursors, whereas the phosphatidyl-inositol fraction was the predominant recipient of nascent arachidonic acid when the eicosatrienoate was the substrate. The express purpose of this investigation was to characterize the biochemical routes involved in the anabolism of various essential fatty acids in the human hepatocyte, through the use of cultured human hepatoma cells as an experimental model system. In view of the similarities between certain aspects of the polyunsaturated fatty acid metabolism of these cells and the corresponding properties of other mammalian hepatic or liver-derived tissues, the data presented here would thus constitute a significant beginning alone those lines. Moreover, considering the extreme difficulty in obtaining for such investigation relevant tissue samples from normal human sources, we regard these results- and the availability for use of this particular human hepatoma cell line-as important new developments in the effort to characterize a useful experimental model both for gaining immediate information and for designing future experiments.

Maintenance of liver function in long term culture of hepatocytes following in vitro or in vivo Ha-rasEJ transfection

Collagenase isolated rat hepatocytes were transfected with liposome encapsulated pEJ (LE-pEJ), a plasmid carrying the human cellular activated Ha-rasEJ oncogene. A proliferative cell line was cloned from these cells transfected in vitro. It secreted per day 0.87 micrograms albumin and 0.32 microgram transferrin per 10(6) cells, and 11.06 nmol free and conjugated bile acids (BA) per mg protein. Also, it metabolized 2-acetylaminofluorene (2-AAF) into N- and ring-hydroxylated metabolites and 2-aminofluorene at rates of 1.50, 9.73, and 1.98 nmol/mg cell protein/24 hr, respectively. Rats were i.v. injected with both LE-pEJ and LE-p17hGHneo carrying the hGH cDNA gene, and secreted hGH in the plasma which induced the synthesis of anti-hGH antibodies. A cell line was cloned from cultures of primary hepatocytes isolated from the liver of transfected rats. After 2 to 3 months in culture, this cell line secreted per day 18.9 micrograms albumin and 11.0 micrograms transferrin per 10(6) cells, 38.75 nmol total BA per mg cell protein, and up to 31 ng hGH per 10(6) cells without cloning hGH recombinant cells. A 24 hr control culture of primary hepatocytes isolated from non transfected rats secreted 25.5 micrograms albumin and 11.7 micrograms transferrin per 10(6) cells, and produced 21.64 nmol total BA and 2.13 nmol N-OH-2-AAF per mg cell protein. Hence, Ha-rasEJ transfection of either hepatocytes in vitro or liver cells in vivo, initiated cell cycles leading to presumptive proliferating hepatocytes which express liver function.

Isoenzymes of pyruvate kinase, lactate dehydrogenase and alkaline phosphatase in epithelial cell lines of rat liver

In cultured epithelial cells of rat liver the isoenzyme patterns of pyruvate kinase, lactate dehydrogenase and alkaline phosphatase were studied and compared with those of freshly isolated parenchymal and non-parenchymal liver cells. In all epithelial cell lines pyruvate kinase was not activated by fructose 1,6-bisphosphate, suggesting the absence of the L-isoenzyme. Cell lines derived from livers of newborn rats expressed LDH-4 and -5, whereas cell lines developed from fetal rat livers contained all 5 lactate dehydrogenase isoenzymes. In the latter case the pattern was found to depend on the state of confluence. All cell lines exhibited only a single alkaline phosphatase form, however, differences were found with respect to electrophoretic mobility.

Toxic effects of 7 beta-hydroxycholesterol on rat liver primary cultures, epithelial lines and co-cultures

The toxic effects of 7 beta-hydroxycholesterol (7 beta-OHC) on cultures and co-cultures of rat hepatocytes, rat liver epithelial cell lines, and rat liver fibroblast lines were investigated. Hepatocytes in primary culture or co-cultured with proliferative epithelial cells, were not affected by the presence of 7 beta-OHC at a concentration of 400 microM over a period of 72 hours. In contrast, proliferative cultures of liver epithelial cell lines and liver fibroblast lines were killed by 50 microM 7 beta-OHC within the first 24 hours. Established liver epithelial cells (hyperploid) were more sensitive to 7 beta-OHC than the same line at early passages (diploid). When hepatocytes and liver epithelial cells were co-cultured and treated with 100 microM 7 beta-OHC, only epithelial cells were lysed. A concentration of 50 microM 7 beta-OHC was toxic to co-cultures of liver epithelial cell and fibroblasts together. In a serum-free medium, the cytotoxic concentration of 7 beta-OHC was lower than that in the serum-supplemented medium. Thus, liver epithelial cells cultured alone or co-cultured with hepatocytes were killed at 12.5 microM and 50 microM 7 beta-OHC, respectively. Finally, cholesterol concentrations four-fold that of 7 beta-OHC antagonized the lethal effects of 7 beta-OHC in the serum-free medium.

Enzyme profile of rat bile ductular epithelial cells in reference to the resistance phenotype in hepatocarcinogenesis

An extensive bile ductular cell hyperplasia with the formation of well-differentiated bile ductules is the most prominent feature of rat liver at 6 to 15 weeks after bile duct ligation. We have improved our previous cell isolation procedure and are now routinely able to obtain from such livers high yields of viable bile ductular epithelial cells. These cells were characterized with respect to their specific activities of gamma-glutamyl transpeptidase and beta-glucuronidase and of select Phase I and Phase II enzymes of biotransformation. At the time of their isolation, only a very small number of the bile ductular epithelial cells were observed to be in DNA synthesis. In addition, in histological sections prepared from intact hyperplastic bile ductular tissue isolates, only the bile ductular epithelial cells exhibited histochemical staining for gamma-glutamyl transpeptidase activity. Typically, greater than 95% of the cells isolated from this tissue were also found to be histochemically positive for gamma-glutamyl transpeptidase activity, and no hepatocytes were seen contaminating this cell population. Biochemically, the isolated bile ductular cells exhibited a gamma-glutamyl transpeptidase specific activity that was 100 times higher than that of hepatocytes isolated at the same time from the bile duct-ligated rats and more than 300 times higher than the specific activity of the enzyme of freshly isolated normal rat hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Cellular events during hepatocarcinogenesis in rats and the question of premalignancy

The cellular, biochemical, and genetic changes that occur in the liver of rats exposed to chemical hepatocarcinogens are reviewed. Multiple new cell types appear in the liver of carcinogen-treated rats including foci, nodules, ducts, oval cells, and atypical hyperplastic areas. The application of phenotypic markers for these cell types suggests that hepatocellular carcinomas may arise from more than one cell type, including a putative liver stem cell that proliferates following carcinogen exposure. Study of DNA, RNA, and proteins produced by hepatocellular carcinomas and putative premalignant cells has so far failed to identify a gene or gene product clearly associated with the malignant or premalignant phenotype. Understanding the cellular lineage from normal cell through putative premalignant cell to cancer is critical to understanding the process of carcinogenesis. Application of new immunological (monoclonal antibody, transplantation) and molecular biological (gene cloning, oncogene identification) approaches to this problem holds promise that the process of hepatocarcinogenesis will be better known in the near future.

Isolation and culture of biliary epithelial cells from the biliary tract fraction of normal rats

A method has been developed for the isolation of a population of cells enriched in epithelial lining cells from the bile ducts of normal rats. The procedure utilized digestion by pronase of the white strands of biliary and connective tissue which remained after hepatocytes had been mechanically removed from collagenase-perfused liver. The resulting cell population was enriched in cells whose ultrastructure resembled that of the epithelial cells of intrahepatic bile ducts. Contamination with hepatocytes, hepatocyte nuclei and erythrocytes was less than 2%. The cells have been maintained in short-term culture. The major morphological change during the first 2 days of culture was proliferation of microvilli, but cell protein composition was unchanged when analysed by polyacrylamide gel electrophoresis. A rabbit antiserum against bovine hoof prekeratin was used to immunohistochemically stain the intermediate filaments of biliary epithelium and was shown to stain more than 90% of the cells in the isolated cell population.

Long-term maintenance of hepatocyte functional activity in co-culture: requirements for sinusoidal endothelial cells and dexamethasone

Sinusoidal cells isolated from adult rat liver have been established in primary culture and in cell line. The presence of factor VIII R:Ag and peroxidatic/phagocytosis activities were the criteria used to distinguish in freshly isolated cells the endothelial cells from the Kupffer cells and suggested the endothelial origin of the cell line. Using a co-culture system, the effect of sinusoidal liver cells on hepatocyte functional activity was characterized. A plateau in which the state of differentiation was stabilized could be generated for co-cultured hepatocytes isolated from adult rat and a disappearance of the initial expression of alpha 1-fetoprotein (AFP) and the increase and/or maintenance of albumin secretion were measured with co-cultured hepatocytes isolated from suckling rat. The presence of dexamethasone was required for such beneficial effect. The hepatocyte-stabilizing activity was also produced by a pulmonary endothelial cell line.

Long-term culture and passage of human fetal liver cells that synthesize albumin

Long-term cultures of hepatocytes were established from livers of human fetuses obtained by abortion at 18 to 23 wk of gestation. Cells obtained by collagenase dissociation of liver were maintained in defined serum-free medium on a substratum of positively charged plastic. Under these conditions, the cells divide and form a confluent monolayer. After multiple passages over a period of 3 mo., the cells retained an epithelioid morphology and continued to synthesize and secrete albumin.