Development and characterization of polarized primary cultures of rat intrahepatic bile duct epithelial cells

The study of intrahepatic bile duct epithelial cells (i.e., cholangiocytes) has been limited by the lack of a polarized in vitro model that allows easy access to both apical and basolateral cell surfaces. Therefore, we developed a cell line of polarized normal rat cholangiocytes (NRCs) and established conditions that produced a confluent monolayer of cells grown on collagen-coated filters of tissue culture inserts. We passaged NRCs at high density to collagen-coated, tissue-culture inserts and measured transepithelial electrical resistance. We evaluated ultrastructural features by transmission and scanning electron microscopy. gamma-glutamyl-transpeptidase (gamma GT) was visualized in cultured cells by enzyme histochemistry, and cytokeratin (CK)-7, CK-19, vimentin, and desmin staining was done by immunohistochemistry. We studied the biologic responsiveness and functional polarity of NRCs by measuring their levels of cyclic AMP after addition of forskolin with or without somatostatin to either the apical or basolateral chambers. When seeded with approximately 1 x 10(5) cells/cm2, the NRCs formed a confluent monolayer in 72 hr. Transepithelial electrical resistance increased over time, achieving a maximum of 625 (+- 25) ohms.cm2 by 1 week after confluence. Transmission and electron microscopy scanning showed the apical cell surface to be tightly packed with microvilli with a heterogeneous display of cilia ranging from none to 20 to 30 cilia/cell. On transmission, apically positioned tight junctions and vesicles were apparent; nuclei were oriented basally and the basolateral surface was characterized by membrane interdigitations. NRCs stained positively for the cholangiocyte marker proteins, gamma-glutamyl-transpeptidase, CK-7, and CK-19, and negative for the mesenchymal markers, vimentin, and desmin. Exposure of the basolateral (but not the apical) cell surface to somatostatin caused a 60% inhibition of forskolin-induced increases in intracellular levels of cyclic AMP, suggesting the presence of somatostatin receptors exclusively on the basolateral plasma membrane domain. We have developed a unique model of primary cultures of normal rat cholangiocytes in which the apical and basolateral surfaces are easily accessible; the cells develop intermediate-strength tight junctions, retain their cholangiocyte phenotype, display morphologic and functional polarity, and are responsive to hormones. This model should be useful for the assessment of vectorial transport of solutes and other constituents of blood and bile, as well as for studying growth regulation of cholangiocytes.

Subcellular localization of pyruvate dehydrogenase dihydrolipoamide acetyltransferase in human intrahepatic biliary epithelial cells

In previous histological studies, biliary epithelial cells (BEC) in the liver of patients with primary biliary cirrhosis (PBC), but not controls, reacted strongly with antibodies specific for the major autoantigen associated with PBC, the E2 component of pyruvate dehydrogenase complex (PDC-E2). In this study we have used transmission electron microscopy (TEM) to document the precise subcellular localization of PDC-E2 in BEC. Two antibodies which recognize PDC-E2 were used: affinity-purified anti-PDC-E2 raised in rabbits; and human antibody from the serum of patients with PBC, affinity-purified against human heart PDC. The intracellular localization of antibody binding was determined by laser scanning confocal microscopy and TEM. Both antibodies bound to the inner membrane of mitochondria in BEC isolated from both patients with PBC and controls, but binding to the external aspect of the plasma membrane was observed only in BEC from patients with PBC. Surface antigen expression in PBC may make BEC immunological targets.

Ductular hepatocytes

Ductular hepatocytes are observed in the livers of both experimental animals and man under various conditions of severe toxin-, carcinogen- or viral-induced hepatic injury with prominent loss of parenchymal hepatocytes. These unique hepatic epithelial cells are characterized by phenotypic traits that are intermediate between those of hepatocytes and intrahepatic biliary epithelium. The origin of ductular hepatocytes is controversial, but it has been hypothesized that they may represent a transitional cell stage associated with either (1) a ductular metaplasia of parenchymal hepatocytes into intrahepatic biliary epithelium, (2) a metaplastic conversion of intrahepatic bile duct or ductular epithelium into hepatocytes, or (3) differentiation of a putative liver stem cell along the hepatocyte lineage. Depending on the liver disease state being investigated, evidence is presented to support all three of these possibilities. Of particular interest is the increasing evidence supporting the existence of a facultative pluripotent stem-like cell associated with the intrahepatic biliary tract, which appears capable of differentiating into various gut endoderm-derived cell types, including hepatocytes, small intestinal mucosal cells, and pancreatic acinar cells. Ductular cells of pancreas have also been demonstrated to alter their differentiation commitment under various induced conditions of pancreatic injury and regeneration, so as to give rise to pancreatic hepatocytes. The presence of a putative stem-like cell in liver together with the plasticity exhibited by some hepatocytes and biliary epithelial cells in various forms of severe hepatic and biliary tract injury can have important implications for carcinogenesis and aberrant regenerative responses in liver. In addition, novel in vivo and cell culture models have been developed, which are serving as potentially powerful tools for investigating the effects of specific growth factors, extracellular matrix components, hormones and other agents on the ability of nonparenchymal epithelial liver cell types to differentiate into hepatocyte-like cells.

Degeneration of intrahepatic bile duct with lymphocyte infiltration into biliary epithelial cells in biliary atresia

Degenerative changes of intrahepatic bile ducts with lymphocytic infiltration into portal areas have been recognized as the characteristic histopathologic features in the liver with biliary atresia (BA). Occasionally, lymphocytic infiltration into biliary ductal epithelium was noted and has been thought to be mostly the result of nonspecific chronic inflammation. However, this histological presentation looks quite similar to that of acute graft-versus-host disease (GVHD) after bone marrow transplantation (BMT) or acute cellular rejection (ACR) after orthotopic liver transplantation (OLTx). According to this histological similarity, we presumed that the degeneration of intrahepatic bile ducts (DIBD) might have developed with lymphocytic infiltration into biliary epithelial cells (LIBE) as some part of an immunologic reaction, and focused on the DIBD with LIBE in the patients with BA. Liver specimens obtained from 31 patients with BA at the time of primary Kasai operation and 3 patients at the time of reoperation were reviewed histologically, and investigated DIBD with LIBE. Nine patients with choledochal cyst (CBD) and 5 patients with neonatal hepatitis (NH) were added to this study as a control population. All patients with BA presented with DIBD with LIBE. On the other hand, only 2 patients with CBD presented with DIBD with LIBE, and no patients with NH presented with DIBD with LIBE. The DIBD with LIBE is not limited to patients with BA, but it seems to be much more serious in this group. These findings may suggest that some sort of immunologic factors contribute to the persistent DIBD in the patients with BA.(ABSTRACT TRUNCATED AT 250 WORDS)

Regulation of bicarbonate-dependent ductular bile secretion assessed by lumenal micropuncture of isolated rodent intrahepatic bile ducts

While intrahepatic bile duct epithelial cells secrete bile through transport of ions and water, the physiological mechanisms regulating ductular bile secretion are obscure, in part because of the lack of suitable experimental models. We report here the successful micropuncture of the lumen of isolated intrahepatic bile ducts and direct measurements of ductular ion secretion. Intact, polarized bile duct units (BDUs) were isolated from livers of normal rats by enzymatic digestion and microdissection. BDUs were cultured and mounted on a microscope in bicarbonate-containing buffer, and the lumens were microinjected with 2',7'-bis(2-carboxyethyl)-5-(and -6)carboxyfluorescein (BCECF)-dextran. Lumenal pH was measured by ratio imaging of BCECF fluorescence using digitized video fluorescent microscopy. After 36 hr in culture, the ends of BDUs sealed, forming closed compartments. After lumenal microinjection of BCECF-dextran, fluorescence was stable at the pH-insensitive wavelength, indicating no dye leakage. Serial changes in pH of extralumenal buffers containing pH-gradient collapsing ionophores allowed us to establish reliable standard curves relating fluorescence ratio to lumenal pH (r = 0.99; P < 0.001). By this approach, the basal pH inside the lumen of BDUs was 7.87 +/- 0.08 units (n = 9), 0.47 unit higher (P < 0.001) than the bathing buffer pH. Addition of 100 microM forskolin increased (P = 0.02) the lumenal pH from 7.78 +/- 0.06 to 7.97 +/- 0.06 units (n = 5); the forskolin effect was completely abolished by incubation of BDUs in HCO3-/CO2-free buffer. Moreover, forskolin caused a 50-fold increase in cAMP levels in BDUs. The observations are consistent with cAMP-dependent, active lumenal HCO3- secretion by BDUs. Furthermore, they demonstrate the suitability of the BDU model for studying regulatory and mechanistic aspects of ductular bile secretion.

Establishment of a transplantable carcinoma arising from the intrahepatic bile duct in Syrian golden hamsters

A subcutaneously transplantable cancer line from the intrahepatic bile duct (IHBD) induced by N-nitrosobis(2-oxopropyl) amine was established in Syrian golden hamsters. The doubling time of this tumour was 2.6 days when 2 x 10(5) tumour cells were inoculated subcutaneously (take-up rate was 100%). Growth of the tumour was significantly faster in male hamsters but neither oestrogen nor androgen receptors were detected in the tumour. The primary and all allograft tumours were tubular adenocarcinomas with fibrosis and a scirrhous pattern resembling human IHBD carcinoma of the peripheral type. Transmission electron microscopic findings showed irregular glands covered with numerous microvilli. Blood-group-related antigens including A, B and H were positive. P-Glycoprotein, which is an indicator of multidrug resistance, was also positive. Carcinoembryonic antigen and CA19-9 as general tumour markers of the biliary tract were negative. The deoxyribonucleic acid (DNA) pattern of this transplantable carcinoma was diploid. This newly established animal model of a transplantable IHBD carcinoma can be used to examine the mechanisms of synthesis and secretion of tumour-associated antigens and to study potential therapeutic agents.

Long-term culture and characteristics of normal rat liver bile duct epithelial cells

BACKGROUND

A method was established for isolation and long-term culture of bile duct epithelial cells (BDEC) of normal adult rat liver that does not require the preparation of highly purified BDEC.

METHODS

After dissociation of the liver parenchyma by collagenase perfusion, the liver remnant containing the intact biliary tree was minced into small fragments, embedded in a rat tail collagen gel, and cultured for 6 days in hormonally defined serum-free Dulbecco's Modified Eagle Medium/F12 medium (SFDM). BDEC cultures were subsequently subcultured and maintained on rat tail collagen gels in SFDM medium containing 5 mumol/L forskolin and 5%-10% Nu Serum IV (Collaborative Research, Bedford, MA).

RESULTS

Established BDEC lines continued to express ductal specific markers including gamma-glutamyl transpeptidase, cytokeratins 7 and 19, and a number of monoclonal antibody-defined bile duct antigens, such as OC.2, OC.3, and OV6.

CONCLUSIONS

The availability of a method to establish normal BDEC lines will allow further investigation of the function of bile duct cells and their role in normal liver differentiation and carcinogenesis.

Appearance of hepatocytelike cells in the interlobular bile ducts of human liver in various liver disease states

Among 1,098 liver biopsy specimens obtained from patients with various liver diseases characterized by liver injury, 58 epithelial cells whose cytoplasms stained positively by the periodic acid-Schiff stain (digested with diastase) were recognized in the interlobular bile ducts of 37 specimens from 36 patients. Light microscopic study revealed that the cytoplasms of these cells were clear or stained weakly eosinophilic on hematoxylin and eosin staining and that the cell limits were distinct. From their reaction with periodic acid-Schiff stain and from electron microscopic observation it was clear that these cells contained an abundance of glycogen and were located among the normal bile duct cells surrounded by basement membrane. On electron microscopy, these cells had microvilli of equal sizes on their luminal surfaces and many irregularly sized microvilluslike cell membrane projections on their basal surfaces. They rested on basement membrane with basal spaces. These cells varied in size from 25.0 to 452.2 microns 2 (mean = 212.2 microns 2). In contrast, the sizes of normal bile duct cells and hepatocytes ranged from 20.0 to 69.3 microns 2 (mean = 34.2 microns 2) and from 113.0 to 860.3 microns 2 (mean = 447.0 microns 2), respectively. Immunohistochemical study with antiserum to cytokeratin 19, albumin and alpha 1-antitrypsin on serially cut frozen sections showed that some of these cells expressed markers of bile duct cells and hepatocytes. Some cells expressed only the markers of hepatocytes. Computer graphic three-dimensional reconstruction clearly demonstrated that these cells were located sparsely (but sometimes in groups) among normal interlobular bile duct cells, without any connection to the surrounding parenchymal hepatocytes.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunohistochemical and immunoelectron microscopic analyses of alpha-amylase isozymes in human intrahepatic biliary epithelium and hepatocytes

The expression and localization of the pancreatic and salivary isozymes of alpha-amylase in the intrahepatic biliary epithelium and hepatocytes were examined by the immunohistochemical method with polyclonal and monoclonal antibodies in 45 normal autopsied human livers. Immunoelectron microscopic studies with the protein A-gold method were performed with the monoclonal antibodies (MAb) on seven of the livers. The intrahepatic biliary system was divided into large ducts, septal ducts, interlobular ducts, bile ductules, and peribiliary glands. Immunohistochemically, pancreatic isozyme was observed in the supranuclear cytoplasm of the epithelium of large ducts, septal ducts, and peribiliary glands in almost all livers. Interlobular ducts expressed pancreatic isozyme in only four (9%) livers. Bile ductules and hepatocytes were negative for pancreatic isozyme in all cases. Expression of salivary isozyme was observed in the supranuclear cytoplasm of the epithelium of large ducts, septal ducts, interlobular ducts, bile ductules, and peribiliary glands in almost all livers, although the expression in interlobular ducts and bile ductules was weak. Hepatocytes were weakly positive for salivary isozyme. Immunoelectron microscopy revealed that both pancreatic and salivary isozymes were located in the supranuclear cytoplasm of the epithelium of large ducts, septal ducts, and peribiliary glands, and that hepatocytes had no pancreatic isozyme but contained salivary isozyme. These data suggest that pancreatic and salivary isozymes of alpha-amylase are produced by the intrahepatic biliary epithelium and secreted into intrahepatic biliary lumens, and that they may play an important role in the physiology of the intrahepatic biliary tree and hepatic bile. It is also suggested that hepatocytes produce a small amount of salivary alpha-amylase that may be secreted into the biliary tree.

Histological features and interphase nucleolar organizer regions in hyperplastic, dysplastic and neoplastic epithelium of intrahepatic bile ducts in hepatolithiasis

Neoplastic transformation occurs in the intrahepatic biliary tree in hepatolithiasis. The present study aimed to clarify the neoplastic processes by correlating the histological features of the bile duct lesions with counts of interphase argyrophilic nucleolar organizer regions (AgNORs), which reflect cell proliferative activity. We studied 55 cases of hepatolithiasis and 25 normal autopsy livers. The biliary epithelial lesions in hepatolithiasis were divisible into hyperplasia, dysplasia and neoplasia. These lesions were found in bile ducts containing calculi. All cases of hepatolithiasis showed a varied degree of hyperplasia. Additionally, eight cases showed dysplasia, five non-invasive intraductal adenocarcinoma and 10 invasive adenocarcinoma. Cases of non-invasive and invasive carcinoma frequently harboured areas of dysplasia, and areas of dysplasia and non-invasive carcinoma, respectively. The mean and standard deviation of the number of interphase AgNORs in the normal and abnormal biliary epithelium showed a step-wise increase in the following order: normal (1.32 +/- 0.36), hyperplasia (1.52 +/- 0.37), dysplasia (2.28 +/- 0.56), non-invasive carcinoma (3.23 +/- 1.00), and invasive carcinoma (3.72 +/- 0.77). These histological and cell kinetic observations suggest that, in hepatolithiasis, carcinogenesis in bile duct epithelial cells progresses in a multi-step manner, through hyperplasia, dysplasia, non-invasive adenocarcinoma and invasive adenocarcinoma.

Ultrastructural aspects of liver injury with special reference to small bile ducts in patients with ulcerative colitis

Liver tissue specimens taken at colectomy from 29 patients with chronic ulcerative colitis were studied by electron microscope. The fine-structural alterations were correlated with light microscopy and with biochemical liver function tests. The purpose was to identify ultrastructural features which could explain the pathogenesis of sclerosing cholangitis. Severely injured bile-duct epithelial cells were seen in three out of the eight light-microscopically diagnosed cholangitis cases, in the two cases of non-specific reactive hepatitis, and in the two fatty livers. Four cholangitis cases had, in heavily thickened bile-duct basement membranes, translucent areas containing bile-like material. Bile-duct microvilli were often blunted, and reduced in number. Intracanalicular bile thrombi and bile inclusions in hepatocytes were seldom seen, mostly but not exclusively in cholangitis. The fine-structural alterations apparently represent various stages of liver injury. These findings do not appear to be specific, but their prominence seems to correlate with the progression of the disease, at least in the case of histological parameters, but also in serum enzyme activities indicative of cholestasis. The bile-like electron-dense material found in proliferating basement membranes, very possibly regurgitated into the injured bile-duct wall after epithelial injury, could enhance the development of periductal fibrosis, leading to progression of sclerosing cholangitis.

[The formation of oval-cell ducts during hepatic carcinogenesis in mice. Its relationship to the pre-existing canals of Hering]

It has been shown that a population of the oval cells is formed in mouse liver during the dipin-induced carcinogenesis (Radaeva, Factor, 1990b). This paper deals with the origin of the oval cells and their proliferation potential depending on localization in the liver lobule. Series of semithin liver sections were studied under the light microscope and detected labeled cells analyzed under electron microscope on serial ultrathin sections. We found that proliferation of cells of terminal bile ductules (Hering [correction of Gering] canals) takes place at the early stages of liver carcinogenesis. These cells and first labeled oval cells had similar size and morphology and jointly formed the ducts. Oval cell population was heterogeneous in terms of proliferative potential. Proportion of proliferating cells (38-45%) in the oval cells of Hering [correction of Gering] canals and small ducts surrounding portal tracts remained similar throughout the period of formation of the oval cell population. In the oval cells infiltrating the parenchyma, the proportion of proliferating cells appeared to depend on the intensity of the oval cell response: it attained the maximum (62%) on intermediate stage and decreased to the minimum (22%) at the peak of the reaction. These data suggest that Hering [correction of Gering] canals probably give origin to the ducts formed by oval cells.

Histological changes in the liver in experimental graft-versus-host disease across minor histocompatibility barriers. VI. A light and electron microscopic study of the periportal changes

Periportal changes of the liver in experimental graft-versus-host disease (GVHD) across minor histocompatibility barriers were investigated electron-microscopically for up to 14 months after bone marrow transplantation (BMT). In GVHD mice, periportal changes affecting the limiting plate of hepatocytes were relatively mild and, in general, classical piecemeal necrosis was rarely observed. However, around 2 weeks after transplantation disruption of the limiting plate of hepatocytes was transiently observed. At that time, lymphocytes invaded directly into the hepatic parenchyma and were in close contact with hepatocytes mainly through a number of point-contacts of cell membranes. Hepatocytes in close contact with lymphocytes showed minor degenerative changes under electron microscopy. On the other hand, periportal bile ductules and canals of Hering were constantly injured by inflammatory cells during the entire observation period up to 14 months after BMT. They were abutted by lymphocytes, together with other inflammatory cells including eosinophils, neutrophils, plasma cells and monocytes. Infiltration of inflammatory cells into the epithelial layer of the bile ductules and canals of Hering through the basement membrane was frequently found. Inflammatory cells were in contact with duct epithelial cells mainly through a number of point-contacts of cell membranes. Epithelial cells in contact with inflammatory cells exhibited a number of degenerative changes, including condensation of cytoplasm, irregular contour of nucleus, dilatation of endoplasmic reticulum, formation of cytoplasmic vesicles, focal cytoplasmic degeneration, and so on.(ABSTRACT TRUNCATED AT 250 WORDS)

A scanning electron microscopic study of the intercalated portion of the biliary system in the rat liver

The intercalated portion of the rat liver was studied by scanning electron microscopy (SEM) after removal of interlobular connective tissue by acid or alkaline hydrolysis. Biliary intercalated portions have generally been regarded as short straight links lying between the bile capillary network and the interlobular duct. The biliary system as observed by SEM lacked such specialized segments for linking. Instead, it contained long intercalated ductules taking winding and branching courses. The ductular branches frequently anastomosed with each other to form an extensive plexus along the limiting plate. The ductules repeatedly connected with the plate on their courses as well as at their terminals. This disposition of the ductules probably potentiates their tolerance to luminal obstruction. At the junction between the ductule and the limiting plate, ductular cells and hepatocytes shared the biliary lumen. The lumen sometimes approached the base of the ductule, providing a possible route for bile leakage. The intercalated ductule was composed of low fusiform epithelial cells throughout its length, meeting its classical criteria by light microscopy. Its basal surface was furrowed with narrow grooves along cell boundaries. The ductular cells extended numerous microplicae in the basal grooves and on their lateral surfaces, suggesting their secretory function.

Glutamate uptake in primary cultures of biliary epithelial cells from normal rat liver

Biliary epithelial cells (BEC) were isolated from normal rat liver with high purity (greater than 95%) as revealed by morphological criteria as well as staining for gamma-glutamyl transferase and cytokeratin 19. During cultivation for 96 hr flattening of the cells and a loss of microvilli was apparent, while the cytokeratin 19-positive phenotype was maintained. The BEC contained a sodium-dependent as well as a sodium-independent uptake system for glutamate with high capacity. Both activities increased transiently during cultivation peaking after 72 and 48 hr, respectively. After 72 hr, apparent kinetic constants could be calculated for the sodium dependent (Km = 13.6 mM; Vmax = 388 nmoles/min/mg protein) and for the sodium-independent system. (Km = 10.8 mM; Vmax = 132 nmoles/min/mg protein). The transient increase of both transport systems was suppressed by dexamethasone. The sodium-dependence showed a threshold concentration of about 35 mM sodium. Inhibition by kainate was much less potent for BEC than for hepatocytes. These data indicate that BEC contain transport systems for glutamate different from those in hepatocytes and which may be involved in the intrahepatic reabsorption of glutamate from bile.

Cellular sources of matrix proteins in experimentally induced cholestatic rat liver

Collagens (I, III, and IV), fibronectin, and laminin were localized using the indirect immunoperoxidase technique 14 days after bile duct ligation, i.e., when extensive fibrosis and numerous neoformed bile ducts were observed. Extensive fibrous septa in enlarged portal spaces were stained for collagens I, III and IV, fibronectin, and laminin. Collagen IV and laminin were abundant around proliferative bile ducts. In addition, collagen IV was nearly continuous in the sinusoids. At the ultrastructural level, antigens were localized in the endoplasmic reticulum of several liver cell types. In portal spaces, bile duct cells and cells that form the transitional canal of Hering were strongly labelled for basement membrane components, particularly laminin, but not for collagens I and III and fibronectin, which were abundant in fibroblast-like cells. Inside the lobule, only Ito cells and, to a lesser extent, endothelial cells contained collagens, fibronectin, and laminin. Ito cells were found to be heavily stained for collagens III and IV, and laminin. Except for fibronectin, which was always abundant, precursors of extracellular matrix proteins were only slightly detectable in the endoplasmic reticulum of some hepatocytes, particularly those located close to altered areas. This study demonstrates that experimental extrahepatic cholestasis in the rat induces periportal fibrosis and continuous deposition of collagen IV in the sinusoids. Several cell types participate in the formation of extracellular matrix components, particularly bile duct cells and Ito cells, with a possible involvement of hepatocytes, thus suggesting that cholestasis provokes changes in the pattern of matrix protein production in liver cells.

Demonstration of nucleolar organizer regions in intrahepatic bile duct carcinoma by the silver-staining technique

A silver colloid technique to identify argyrophilic nucleolar organizer region associated protein (AgNOR) was applied to 43 cases of intrahepatic bile duct carcinoma (cholangiocarcinoma, CC), 2 with bile duct adenoma (BDA), 5 with focal duct epithelial hyperplasia (FEH) associated with hepatolithiasis, 15 with posthepatitic ductular proliferation (PHDP) associated with massive or submassive hepatic necrosis and 20 of normal liver. In the present study, only discrete, easily counted black dots within nuclei and silver-stained nucleolus were counted under a magnification of x 400 without oil-immersion objectives. The mean AgNOR count of CC was significantly higher than those of BDA, FEH, PHDP and normal controls (P less than 0.05, P less than 0.001, P less than 0.01, and P less than 0.001, respectively). Among CCs the mean AgNOR numbers of papillary adenocarcinoma (pap), moderately (tub2) and poorly differentiated (por) adenocarcinoma, and adenosquamous carcinoma (as) were significantly higher than that of normal controls (P less than 0.01, P less than 0.001, P less than 0.001 and P less than 0.001, respectively), and those of tub2, por and as were also significantly higher than those of BDA, FEH and PHDP, whereas that of well differentiated tubular adenocarcinoma (tub1) was not different from those of BDA, FEH, PHDP and normal controls, and that of pap was not different from those of BDA, FEH and PHDP. The mean numbers of AgNORs of BDA and FEH were not different from that of normal controls, whereas that of PHDP was significantly higher than that of normal controls (P less than 0.01). Interestingly, the mean AgNOR counts of tubular adenocarcinoma were increased with histologic tumor grades.(ABSTRACT TRUNCATED AT 250 WORDS)

Taurocholate stimulates transcytotic vesicular pathways labeled by horseradish peroxidase in the isolated perfused rat liver

The effect of taurocholate on transcytotic vesicular pathways labeled with horseradish peroxidase was assessed in isolated perfused rat liver preparations. Forty-five minutes after a horseradish peroxidase load in a recirculating system, continuous infusion of taurocholate but not taurodehydrocholate significantly increased horseradish peroxidase excretion in bile by 50% compared with controls. When horseradish peroxidase (25 mg) was pulse loaded for 1 minute in control perfusions, it appeared in bile in early (4-6 minutes) and late (20-25 minutes) peaks, the latter accounting for 90% of total horseradish peroxidase output. Taurocholate infusion significantly increased horseradish peroxidase output in both early and late peaks, whereas only a small increase in the early peak was observed with taurodehydrocholate. Colchicine pretreatment increased the early peak in bile but abolished the second peak. Electron micrographs from control livers revealed the accumulation of horseradish peroxidase-containing vesicles in pericanalicular regions at early (2 minutes) as well as late (18 minutes) periods. When a morphometric analysis of electron micrographs was performed from pericanalicular regions 2 minutes after a 1-minute pulse of horseradish peroxidase (500 mg), taurocholate but not taurodehydrocholate increased both the density and percent area of horseradish peroxidase-containing vesicles compared with controls. In contrast, colchicine pretreatment had no effect on the density of the early-appearing vesicles, although their individual sizes were reduced. Taurocholate but not taurodehydrocholate also increased the percent of tubular structures in the pericanalicular region. These findings indicate that taurocholate stimulates both early and late transcytotic vesicle pathways and therefore probably microtubule-independent vesicle pathway is present in hepatocytes that must be distinguished from paracellular routes.

Morphologic demonstration of receptor-mediated endocytosis of epidermal growth factor by isolated bile duct epithelial cells

It was recently shown that intrahepatic bile duct epithelial cells in situ or after isolation from rat liver have coated pits and vesicles, suggesting that they participate in receptor-mediated endocytosis. Therefore, using a morphologic approach and epidermal growth factor coupled to horseradish peroxidase or colloidal gold as probes, we studied freshly isolated or short-term cultured intrahepatic bile duct epithelial cells prepared from normal rat liver to determine if they participate in receptor-mediated endocytosis. Immunoelectron microscopy using a monoclonal antibody against the epidermal growth factor receptor was also used to examine for the presence of the growth factor receptor on the cells. Immediately after isolation, the cells did not internalize either epidermal growth factor-horseradish peroxidase or epidermal growth factor-colloidal gold; no growth factor receptor could be shown on these cells by immunocytochemistry, either. In contrast, cells cultured for 24 h bound and internalized both epidermal growth factor-horseradish peroxidase and epidermal growth factor-colloidal gold at 37 degrees C and showed growth factor receptors diffusely distributed on the plasma membrane. When cultured cells exposed to epidermal growth factor-colloidal gold were fixed with glutaraldehyde containing saponin and tannic acid, colloidal gold particles were observed in coated pits and in coated and uncoated vesicles. Preincubation of cultured cells with native epidermal growth factor completely blocked the internalization of both epidermal growth factor-horseradish peroxidase and epidermal growth factor-colloidal gold. When rat liver was stained in situ for epidermal growth factor receptor, reaction product was observed by immunoelectron microscopy exclusively on the basal surface of the plasma membrane of the intrahepatic bile duct epithelial cells. These results indicate that bile duct epithelial cells internalize epidermal growth factor by endocytosis via coated pits containing receptors localized in situ exclusively to the basal domain of their plasma membranes. The data demonstrate for the first time that intrahepatic bile duct epithelial cells participate in receptor-mediated endocytosis and raise the possibility that they are a target for epidermal growth factor.

Fluid-phase endocytosis by intrahepatic bile duct epithelial cells isolated from normal rat liver

Although recent data from our laboratory have established the occurrence of receptor-mediated endocytosis in intrahepatic bile duct epithelial cells (IBDEC) isolated from normal rat liver, no studies have assessed the role of isolated IBDEC in fluid-phase endocytosis. Therefore, to determine if IBDEC participate in fluid-phase endocytosis, we incubated morphologically polar doublets of IBDEC isolated from normal rat liver with horseradish peroxidase (HRP, 5 mg/ml), a protein internalized by fluid-phase endocytosis, and determined its intracellular distribution by electron microscopic cytochemistry. Pulse-chase studies using quantitative morphometry were also performed to assess the fate of HRP after internalization. After incubation at 37 degrees C, IBDEC internalized HRP exclusively at the apical (i.e., luminal) domain of their plasma membrane; internalization was completely blocked at 4 degrees C. After internalization, HRP was seen in acid phosphatase-negative vesicles and in acid phosphatase-positive multivesicular bodies (i.e., secondary lysosomes). Small acid phosphatase-negative vesicles containing HRP moved progressively from the apical to the basal domain of IBDEC. Pulse-chase studies showed that HRP was then discharged by exocytosis at the basolateral cell surface. These results demonstrate that IBDEC prepared from normal rat liver participate in fluid-phase endocytosis. After internalization, HRP either is routed to secondary lysosomes or undergoes exocytosis after transcytosis from the luminal to the basolateral cell surface. Our results suggest that IBDEC modify the composition of bile by internalizing both biliary proteins and fluid via endocytic mechanisms.

Isolated trout liver cells: establishing short-term primary cultures exhibiting cell-to-cell interactions

Composition and interactions of cell types in rainbow trout (Oncorhynchus mykiss) liver digested with collagenase and cultured in serum-free media were investigated. Suspensions obtained after digesting trout liver with collagenase contained all the cell types present in the liver, including liver parenchymal cells (hepatocytes), biliary epithelial cells, sinusoidal endothelium, fat-storing cells of Ito, and macrophages. A major cell pellet, mainly hepatocytes but containing significant numbers of biliary epithelial cells, was obtained by centrifuging the cell suspension at 120 X g for 1 min. Cells present in this pellet quantitatively attached to culture plates coated with a trout skin extract and remain attached for 4 to 6 d with good retention of intracellular enzymes and DNA. When in culture, significant changes in and among the cells were observed. Initial preparations were rounded, single cells. Within several hours, however, cellular interactions leading to aggregation became evident and aggregates increased in size for 2 to 3 d. Scanning electron microscopy (EM) showed frequent shaftlike projections from margins of the aggregates. Transmission EM indicated that these projections represent biliary ductules forming in vitro. Adjacent hepatocytes also showed plasma membrane specializations forming junctional complexes and canaliculi characteristics of normal trout liver. After 5 to 6 d in culture, significant numbers of the cell aggregates dislodged from the plate. Analysis showed the dislodged cells were viable but vacuolated. The reestablishment in vitro of morphologic relationships resembling in situ tissue components suggest these culture preparations may have significant utility in cooperative metabolic studies of cell interactions in trout liver.

The microanatomy of the intrahepatic bile duct in polycystic disease: comparison of the cpk mouse and human

The cpk mutation in mice produces a lethal recessive form of polycystic kidney disease (PKD) that, like human forms of the condition, is associated with an age-related incidence of hepatic cysts. Injection of plastic into the biliary tree of affected animals revealed that these cysts arise from focal dilatations of the epithelial lining that may enlarge to the point that they obstruct the bile ducts. This concept was supported by histological and scanning and electron microscopic studies. No evidence could be found of primary obstruction of the biliary tree. The same techniques were then employed in specimens of human liver from patients with both recessive (ARPKD) and dominantly inherited PKD (ADPKD). Similar abnormalities of the biliary tree were identified. These abnormalities were not found in control liver samples from patients without PKD. The liver of the patient with ADPKD also demonstrated many von Meyenburg complexes. These were related to some cyst development, but these complexes freely communicated with bile ducts, contrary to currently held opinion. We conclude that hepatic abnormalities in the cpk mouse and human PKD arise from changes in bile ducts that are analogous to the renal lesions.

[Structure of the excretory ducts, intraorganic lymphatic vessels, tissue canals and intercellular space of various organs (data of scanning electron microscopy injection replicas)]

Architectonics of the biliary canaliculi and intrahepatic ducts systems, as well as intraorganic urinary pathways in white rats have been investigated by means of scanning electron microscopy of injection replica. Acinar structure of the intralobular part of the biliary bed has been proved. Anastomoses between the biliary canaliculi of the neighbouring lobules have been demonstrated. A useful method for obtaining injection replica of the intraorganic lymphatic vessels is filling of the ductal system of the parenchymatous organs with solid resins (methylmethacrylate+) under a high (nonphysiological) pressure. Casts of periportal and paravenous hepatic lymphatic vessels have been obtained. An ability of methylmethacrylate to replicate intercellular and connective tissue spaces is verified. Casts of the perisinusoid spaces (Disse) are obtained for the first time.

Histologic studies on the hepatic lesions induced by graft-versus-host reaction in MHC class II disparate hosts compared with primary biliary cirrhosis

By light and electron microscopic examinations, histologic changes in the liver of mice with graft-versus-host reaction (GVHR) were analyzed. To induce GVHR, C57BL/6 (B6) spleen cells were injected into (B6Xbm1)F1, (B6Xbm12)F1, and (bm1Xbm12)F1 mice. In (B6Xbm12)F1 recipient mice, bile duct changes resembling chronic non-suppurative destructive cholangitis (CNSDC) and a formation of epithelioid granulomas were observed during the course of GVHR. An epithelioid granuloma in the liver of (B6Xbm1)F1 or (bm1.Xbm12)F1 recipients was not detected. By electron microscopy, the bile duct epithelia were seen to be in close contact with infiltrating cells, and marked alterations of their cytoplasm and microvilli were demonstrated; ie, vacuolation of the cytoplasm, deterioration of microvilli, and bleb formation were frequently observed in the liver of class II-disparate hosts. Concerning the basement membrane, no marked changes characteristic of primary biliary cirrhosis (PBC), such as many-layered basement membranes containing osmium positive substance, were detected. Because the major histocompatibility complex (MHC) class II-disparate system was used in our experimental system in the GVHR, the antigen expressed on the bile duct might be a target and be associated with the formation of the initial hepatic lesions in PBC such as CNSDC and epithelioid granuloma formation. Thus, GVHR across the MHC class II antigen is believed to play an important role in the development of PBC.