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Mature hepatocytes are suggested to possess a capacity for bile ductular transdifferentiation, but whether and how hepatocytes contribute to ductular reaction in chronic liver diseases has not been elucidated. We examined whether mouse hepatocytes can transdifferentiate into bile ductular cells in vitro, using a three-dimensional collagen gel culture method, and in vivo, using a liver repopulation model in which β-galactosidase–positive hepatocytes from Alb-Cre × ROSA26R mice were transplanted into the liver of wild-type mice. We further examined the relative contribution of intrinsic hepatocytes in ductular reaction in a hepatocyte lineage–tracing model using Mx1-Cre × ROSA26R mice treated with polyinosinic–polycytidylic acid. Within collagen gels, hepatocytes exhibited branching morphogenesis associated with the emergence of bile duct–like phenotype. In the liver repopulation model, many β-galactosidase–positive, hepatocyte-derived bile ductular structures were identified; these markedly increased after liver injury. In Mx1-Cre × ROSA26R mice, relatively minor but significant contributions of hepatocyte-derived bile ductules were observed in both periportal and centrilobular ductular reaction. As the centrilobular ductular reaction progressed, the portal ducts or ductules migrated toward the injured area and joined with hepatocyte-derived ductules, leaving the portal tract without biliary structures. We conclude that hepatocytes and bile ducts or ductules are important sources of ductular reaction and that the intrahepatic biliary system undergoes remarkable remodeling in response to chronic liver injury.

We previously demonstrated that mature rat hepatocytes transdifferentiate to bile ductular cells when cultured in a three-dimensional collagen-rich matrix. Here, we show that the phenotype of transdifferentiated hepatocytes can be reversed by modulating culture conditions. Spheroidal aggregates of hepatocytes were cultured within a collagen gel matrix in the presence of serum and tumor necrosis factor-α. Spheroids transformed into ductular structures composed of small cuboidal cells, lost the expression of hepatocytic markers, whereas aberrantly expressed bile ductular markers. The transdifferentiated cells were then retrieved from the gels, plated on surfaces coated with a basement membrane-like material, and cultured in serum-free media. Cells spontaneously formed spheroidal aggregates and recovered hepatocytic phenotype. Dexamethasone (Dex), which suppressed the phosphorylation of ERK and Jun N-terminal kinase, facilitated the recovery, and the combination with interleukin-6 or oncostatin M resulted in the recovery of hepatocyte nuclear factor 4 α protein expression and the typical hepatocytic morphology, and a decrease in the expression of bile ductular markers. A cDNA microarray analysis revealed that the hepatocyte-specific mRNA expression profile was recovered in these cells. Our results demonstrate that hepatocytes are able to recover their phenotypes following bile ductular transdifferentiation, suggesting that hepatocytic and bile ductular phenotypes may be mutually reversible.

Orthovanadate (OV), an inhibitor of protein tyrosine phosphatases, affects various biological processes in a cell-type-specific manner. In this study, we investigated the effect of OV on hepatic stellate cells (HSCs). When primary rat HSCs were cultured in the presence of 10% serum, they spontaneously lost characteristic stellate morphology, proliferated, and were transformed into an activated state with the formation of abundant stress fibers and increased expression of both α-smooth muscle actin and collagen type I mRNA. OV treatment inhibited proliferation and activation of HSCs and partially reversed the phenotype of activated HSCs. Among the signaling molecules investigated, phosphorylation of the Src protein at tyrosine 416 was the most striking in OV-treated HSCs. Treatment of cells with Src family inhibitors partially abrogated the effects of OV. Furthermore, transfection of v-Src into activated HSCs induced a stellate morphology similar to that in the quiescent state. We then examined whether OV could effectively suppress HSC activation in vivoafter liver injury induced by either carbon tetrachloride or dimethylnitrosamine. OV significantly reduced the appearance of α-smooth muscle actin-positive cells and decreased collagen deposition, concomitant with an improvement in liver function. Our study showed for the first time that OV was able to suppress the activation of HSCs, possibly through the modulation of Src activity, and attenuated fibrosis after chronic liver injury.

To elucidate the mechanism of apoptosis of liver sinusoidal endothelial cells (SECs), we examined the phosphorylation status of Bad and its upstream signaling molecules during apoptosis in culture and after ischemia-reperfusion injury. Rat SECs were isolated by the immunomagnetic method, and 2 days after culture, most SECs underwent apoptosis, which was associated with decreased tyrosine phosphorylation of cellular proteins. Addition of orthovanadate (OV), a protein tyrosine phosphatase inhibitor, sustained cellular protein phosphorylation and strongly inhibited apoptosis. Bad was dephosphorylated at Ser-112 and Ser-136 during apoptosis, but the phosphorylation status of Bad was maintained in the presence of OV. OV activated the Akt, extracellular signal-regulated protein kinase, and p38 mitogen-activated protein kinase pathways, which are involved in Bad phosphorylation. In the absence of OV, depletion of Bad by RNA interference conferred resistance to apoptosis. Hepatic injury after ischemia-reperfusion was alleviated by OV treatment, with significant inhibition of SEC apoptosis. SEC apoptosis in vivowas associated with dephosphorylation of Bad, Akt, and extracellular signal-regulated protein kinase, which was blocked by OV treatment. Our data suggest that maintenance of Bad phosphorylation is important in the prevention of SEC apoptosis and that the anti-apoptotic property of OV might have therapeutic utility.

We investigated the mechanism of phenotypic plasticity of hepatocytes in a three-dimensional organoid culture system, in which hepatocytic spheroids were embedded within a collagen gel matrix. Hepatocytes expressed several bile duct markers including cytokeratin (CK) 19 soon after culture and underwent branching morphogenesis within the matrix in the presence of insulin and epidermal growth factor. Cultured hepatocytes did not express Delta-like, a specific marker for oval cells and hepatoblasts. Furthermore, hepatocytes isolated from c-kit mutant rats (Ws/Ws), which are defective in proliferation of oval cells, showed essentially the same phenotypic changes as those isolated from control rats. The bile duct-like differentiation of hepatocytes was associated with increased expression of Jagged1, Jagged2, Notch1, and several Notch target genes. CK19 expression and branching morphogenesis were inhibited by dexamethasone, a mitogen-activated protein kinase kinase 1 (MEK1) inhibitor (PD98059), and a phosphatidyl inositol 3-kinase inhibitor (LY294002). After being cultured for more than 3 weeks within the gels, hepatocytes transformed into ductular structures surrounded by basement membranes. Our results suggest that hepatocytes might have the potential to transdifferentiate into bile duct-like cells without acquiring a stem-like phenotype and that this is mediated through specific protein tyrosine phosphorylation pathways.

A growing body of evidence indicates that the gap junction (GJ) plays a pivotal role in tumor suppression by exerting cell‐cell communication. It has, however, been reported that expression of connexin26 (Cx26) protein is induced in human ductal carcinomas of the breast and that its amount increases in proportion to the grade of malignancy. We thus examined the effects of over‐expressed Cx26 on growth characteristics in GJ‐deficient human MCF‐7 breast cancer cells that maintain the phenotype of early‐stage cancers. MCF‐7 cells were transfected with Cx26 cDNA, and several clones of stable transformants exhibiting a high level of cell‐cell communication were established. When they were examined in terms of various growth characteristics in vitro, the proliferation rate and the saturation density were drastically reduced in Cx26‐transfected clones compared with the mock‐transfectant. The anchorage‐independent growth capacity was also decreased by 50–75% after transfection of Cx26. Furthermore, the cell migration toward growth factors and cell invasion into Matrigel in a Boyden chamber were suppressed to 5–10% and 20–60%, respectively, of the control in Cx26‐transfected clones. When implanted into the mammary fat pads of nude mice in the presence of an excess of 17β‐estradiol, Cx26‐transfected clones tended to show slower tumor growth than the mock‐transfectant, although the difference was not statistically significant. Our results strongly suggest that the induction of Cx26 protein observed in human breast cancers, reported previously, may not be very relevant to the development of breast cancers, and that Cx26 can function as a tumor suppressor in breast cancer cells.

ABSTRACTThe virulence traits of the Escherichia colistrain associated with a waterborne diarrhea outbreak were examined. Forty-one of 75 students (ages 12 to 15) in Akita Prefecture, Japan, showed clinical symptoms. Seven E. coliOuk:K-:H45 isolates were isolated from the patients as the causative agent of this outbreak. One isolate (EC-3605) showed the presence of E. coliattaching-and-effacing (eaeA) and enteroaggregative E. coliheat-stable enterotoxin-1 (astA) genes and the absence of Shiga toxin (stx1and stx2) genes. A polymorphic enteropathogenic E. coli(EPEC) adherence factor plasmid was detected in EC-3605 with a major structural gene deletion and a regulatory gene frameshift mutation, revealing that EC-3605 represents an atypical EPEC strain harboring the astAgene. The role that atypical EPEC strains harboring the astAgene play in human disease is unclear. Our results, along with those of others, present a possibility that these strains comprise a distinct category of diarrheagenic E. coliand that astAaffects the age distribution of atypical-EPEC infection.

ABSTRACTVirulence characteristics of diarrheal outbreak-associated Escherichia coliO55:NM, O126:NM, and O111:NM were examined. The E. coliO55:NM strains were atypical enteropathogenic E. coli(EPEC), while the E. coliO126:NM and O111:NM strains should be classified as enteroaggregative E. coli(EAggEC). The contributions of EPEC and EAggEC to the human disease burden in Japan might be significantly greater than is currently appreciated.

t(11;18) is a recurrent chromosomal abnormality observed in mucosa-associated lymphoid tissue (MALT)-type lymphoma. API2 and MLT genes have been implicated. The authors devised a dual-color interphase fluorescence in situ hybridization (FISH) system to detect splitting of 11q22 and its fusion with 18q21. Subjects were 44 cases of extranodal lymphoma and cases of primary macroglobulinemia. Whenever RNA was available, reverse transcriptase–polymerase chain reaction followed by sequence analysis was performed. Positive cases by dual-color FISH analysis were restricted to MALT-type lymphoma and one case of primary macroglobulinemia. Among 24 cases of MALT-type lymphoma, 14 (58) (4 gastric, 5 pulmonary, 3 orbital, 1 salivary, and 1 thyroid lymphomas) had splitting of the 11q22 region probes and fusion of signals suggesting the translocation of chromosome 11 and 18. Reverse transcriptase–polymerase chain reaction analysis showed the API2/MLT gene fusion in 9 of 10 cases. Sequence analyses showed three different modes of involvement of the MLT gene, whereas the breakpoint at API2 was the same. Monoclonal component of serum immunoglobulin M was observed in 3 of 14 positive cases for the translocation. Direct visualization using dual-color FISH on samples serves as a molecular tool for management of MALT-type lymphoma with API2/MLT gene fusion.

Changes in expression of the two tight junction-associated proteins, barmotin/7H6 and ZO-1, as well as the adherence junction-associated protein, E-cadherin, were followed during hepatocyte growth factor/scatter factor (HGF/SC)-induced migration process of MDCK cells. Modulation of the HGF/SF-induced migration process by staurosporine, an inhibitor of protein kinase C (PKC), was also examined. Cell migration induced by HGF/SF consisted of two distinct phases, initial cell spreading between 2 and 9h after the start of treatment, and the scattering phase which started ∼12h after treatment. Both ZO-1 and E-cadherin were expressed at the cell–cell border of adherent cells in the scattering phase, whereas barmotin/7H6, a barrier function-related tight junction protein, was not seen during the early spreading phase. Confluent cultures of MDCK cells, which did not spread after HGF/SF treatment, were positive for barmotin/7H6 expression at cell–cell borders. Blocking PKC activation during HGF/SF treatment with staurosporine inhibited cell spreading, and the cells retained barmotin/7H6 expression until at 6h after HGF/SF treatment. The results indicate that disappearance of the tight junction protein, barmotin/7H6, is closely associated with cell spreading, with both barmotin/7H6 expression and cell spreading seemingly being regulated by PKC-mediated signaling.

LEC rats spontaneously develop hepatocellular carcinoma with cholangiofibrosis after chronic hepatitis, but the mechanism of development of the hepatic injury is not clear. To investigate the role of hepatic stellate cells in induction or suppression of hepatic fibrosis, we morphologically examined the liver of LEC rats. Accumulation of copper was analyzed by the Danscher‐Timm's sulfide‐silver method. Histopathological changes were evaluated by hematoxylin and eosin staining, and by Masson's trichrome method. Activated stellate cells were identified by immunostaining method for α‐smooth muscle actin. Cytological alterations of the stellate cells were investigated by transmission electron microscopy. To evaluate the lipid content in the stellate cells, we analyzed the area of lipid droplets of the cells by morphometric analysis. Also for evaluation of the changes in the number of stellate cells, the numbers of nucleated stellate cells and parenchymal cells were counted and statistically analyzed. Hepatic parenchymal cells showed excessive accumulation of copper at 5 weeks of age. Submassive necrosis was observed at 19 weeks of age. The liver of LEC rats 1.5 years of age showed cholangiofibrosis and subcellular injury of hepatic parenchymal cells. However, no diffuse hepatic fibrosis was observed in the liver, and hepatic stellate cells around the regions of cholangiofibrosis were negative for α‐smooth muscle actin. The area of lipid droplets of a stellate cell in the liver of LEC rats was 1.6 to 1.8 times as large as that of normal Wistar rats. The hepatic stellate cells did not participate in the accumulation of collagen fibers around themselves when the cells contained a large amount of vitamin A‐lipid droplets, even though the development of hepatic lesions was in progress. Our present data are consistent with our previous hypothesis that there is an antagonistic relationship between the storage of vitamin A and the production of collagen in stellate cells. Anat Rec 258:338–348, 2000. © 2000 Wiley‐Liss, Inc.

LEC rats spontaneously develop hepatocellular carcinoma with cholangiofibrosis after chronic hepatitis, but the mechanism of development of the hepatic injury is not clear. To investigate the role of hepatic stellate cells in induction or suppression of hepatic fibrosis, we morphologically examined the liver of LEC rats. Accumulation of copper was analyzed by the Danscher-Timm's sulfide-silver method. Histopathological changes were evaluated by hematoxylin and eosin staining, and by Masson's trichrome method. Activated stellate cells were identified by immunostaining method for α-smooth muscle actin. Cytological alterations of the stellate cells were investigated by transmission electron microscopy. To evaluate the lipid content in the stellate cells, we analyzed the area of lipid droplets of the cells by morphometric analysis. Also for evaluation of the changes in the number of stellate cells, the numbers of nucleated stellate cells and parenchymal cells were counted and statistically analyzed. Hepatic parenchymal cells showed excessive accumulation of copper at 5 weeks of age. Submassive necrosis was observed at 19 weeks of age. The liver of LEC rats 1.5 years of age showed cholangiofibrosis and subcellular injury of hepatic parenchymal cells. However, no diffuse hepatic fibrosis was observed in the liver, and hepatic stellate cells around the regions of cholangiofibrosis were negative for α-smooth muscle actin. The area of lipid droplets of a stellate cell in the liver of LEC rats was 1.6 to 1.8 times as large as that of normal Wistar rats. The hepatic stellate cells did not participate in the accumulation of collagen fibers around themselves when the cells contained a large amount of vitamin A-lipid droplets, even though the development of hepatic lesions was in progress. Our present data are consistent with our previous hypothesis that there is an antagonistic relationship between the storage of vitamin A and the production of collagen in stellate cells. Anat Rec 258:338–348, 2000. © 2000 Wiley-Liss, Inc.

By employing the cationic colloidal silica membrane density perturbation technique, we examined growth factor receptor and extracellular matrix (ECM) changes at the sinusoidal surface during rat liver regeneration 72 hours after 70% partial hepatectomy (PHx). At this time after PHx, hepatocyte division has mostly subsided, while sinusoidal endothelial cell (SEC) proliferation is initiating, resulting in avascular hepatocyte islands. Because of the discontinuous nature of the surface of liver SEC, ECM proteins underlying the SEC, as well as SEC luminal membrane proteins, are available to absorption to the charged silica beads when the liver is perfused with the colloid. Subsequent liver homogenization and density centrifugation yield two separate fractions, enriched in SECs as well as hepatocyte basolateral membrane-specific proteins up to 50-fold over whole liver lysates. This technique facilitates examination of changes in protein composition that influence or occur as a result of SEC mitogenesis and migration during regeneration of the liver. When ECM and receptor proteins from SEC-enriched fractions were examined by Western immunoblotting, urokinase plasminogen activator receptor, fibronectin, and plasmin increased at the SEC surface 72 hours after PHx. Epidermal growth factor receptor, plasminogen, SPARC (secreted protein, acidic and rich in cysteine, also called osteonectin or BM40), and collagen IV decreased, and fibrinogen subunits and c-Met expression remained constant 72 hours after PHx when compared to control liver. These results display the usefulness of the cationic colloidal silica membrane isolation protocol. They also show considerable modulation of surface components that may regulate angiogenic processes at the end stage of liver regeneration during the reformation of sinusoids.

The induction of a novel Ca2+-dependent protease in rat liver treated with various liver promoters, as well as its increase in preneoplastic lesions during liver carcinogenesis, was demonstrated. Six groups of male Fischer 344 rats (150 g body weight) were fed separately diets containing one of the following promoters: 0.05% phenobarbital (PB), 0.05% dichlorodiphenyltrichloroethane (DDT), 0.25% ethyl-α-chlorophenoxyisobutyrate (CPIB), 0.5% butylated hydroxytoluene (BHT), 10 ppm 17-α-ethynylestradiol (EE), and 0.05% of the non-promoter diphenylhydantoin (DH). After feeding the indicated diets for 1 week, rats were killed and protease activity in the microsomal fraction of liver tissue was determined using N-benzoyl-L-tyrosine ethyl ester as substrate. The activity of protease increased 3- to 5-fold after treatment with the promoters and compared with normal liver; the non-promoter (DH) induced a slight increase in activity. Hyperplastic nodules were induced according to the method of Solt and Farber. The activity of protease was significantly high in these preneoplastic lesions compared with the surrounding liver tissue. Biochemical characterization of this protease revealed the following properties: 1) high Ca2+dependency, 2) different molecular weight and optimum pH from previously reported proteases, and 3) preferential distribution in the SER fraction. These results suggest that a novel type of protease is induced specifically in the liver by promoters of liver carcinogenesis. The possible importance of this protease in the carcinogenic process is discussed.

An important function of the tight junction is to act as a selective barrier to ions and small molecules, although no molecule responsible for the barrier function has been identified. Here we report evidence that the localization of the 7H6 tight junction-associated antigen identified in our laboratory at tight junctions correlates with the barrier function of MDCK cells. MDCK cells in a confluent monolayer possessed a polarized morphology, having an apical plasma membrane and a basolateral membrane, which is separated from the former by tight junctions. MDCK cells expressed both ZO-1 and 7H6 antigen at tight junctions, which maintain a tight barrier as determined by resistance to lanthanum permeation and high transepithelial electrical resistance (TER, 1500 ohm-cm²). The 7H6 antigen disappeared as tight junctions became permeable to lanthanum with a decrease in TER (below 100 ohm-cm²) due to treatment with metabolic inhibitors (10 μm antimycin A and 10 mM 2-deoxyglucose) for 30 min, while leaving ZO-1 at the cell border. The 7H6 antigen appeared at tight junctions again as TER recovered to a high level (1500 ohm-cm²) within 3 h after withdrawal of metabolic inhibitors. In addition, we found that 7H6 antigen is a phosphorylated protein and that phosphorylation is closely related to the localization of 7H6 antigen in the area of tight junctions. Copyright 1994, 1999 Academic Press

We present a case of gestational choriocarcinoma that developed in a pregnant woman with metastases to her baby. In this case, severe anemia and hepatomegaly of the baby were noticed after delivery. Despite intensive treatments, the tumor progressed rapidly, and the baby died at the age of 38 days. Accurate diagnosis was made after autopsy. When the baby's mother visited our hospital again at 4 months postpartum, there were widespread multiple metastases to her lungs and liver. We want to emphasize that if a neonate or infant has anemia and/or hepatomegaly, it is necessary to be aware of the possibility of infantile choriocarcinoma with the presence of an occult tumor in the mother and to examine the mother's and infant's hCG levels immediately.

To study the regulation of the endothelial barrier, we examined the relationship between the paracellular barrier function and the expression of 7H6 antigen localized at tight junctions of endothelial cells by using transendothelial electrical resistance (TER), fluxes of albumin and dextran, transmigration of rat mammary cancer (SST-2) cells across rat lung endothelial (RLE) cells, and immunocytochemical expression of 7H6 antigen as parameters. RLE cells cultured at a confluent cell density did not express immunohistochemically demonstrable 7H6 antigen and had low paracellular barrier functions. However, treatment of the endothelial cells with 0.5 mMdibutyryl–cAMP or 10−6Mall-trans-retinoic acid for 4 days induced 7H6 antigen preferentially at the cell border and simultaneously enhanced the barrier function twofold, in terms of TER and fluxes of albumin and dextran. Furthermore, RA-treated RLE cell monolayers with the enhanced barrier function significantly inhibited the transmigration of SST-2 cells. These results together with those of our previous study indicate that 7H6 antigen has a crucial role in the regulation of paracellular barrier function not only in epithelial cells but also in vascular endothelial cells. The present study also suggests that tight junctions of vascular endotheliumin vivofunction as a barrier between blood and tissues against metastatic cancer cells.

Abstract: We report a rare case of alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), and carbohydrate antigen (CA) 19-9-producing gallbladder cancer with high levels of CA125 and protein induced by vitamin K absence or antagonist II (PIVKA II). A 63-year-old man was diagnosed with gallbladder cancer with metastases to the liver, based on ultrasonography and computed tomography of the abdomen showing multiple tumorous lesions in the liver and a thickened gallbladder wall. Laboratory data showed high levels of tumor markers: 4647.4 ng/ml AFP, 9987.1 ng/ml CEA, 11704.0 U/ml CA19-9, 847.6 U/ml CA125, and 0.2 AU/ml PIVKA II. AFP in the present case showed an increase in Concanavalin A-nonbinding fraction and an increase inLens culinaris lectin-binding fraction by affinity column chromatography. The patient died of hepatic failure. Autopsy revealed gallbladder cancer consisting of papillary adenocarcinoma and moderately differentiated tubular adenocarcinoma. By immunohistochemical staining, AFP was detected in the papillary adenocarcinoma portion of the primary focus and metastatic tumor cells in the liver, but was not detected in noncancerous liver tissue. CEA and CA19-9 were detected mainly in the tubular adenocarcinoma portion.

ABSTRACTFour blaVIM-2gene-harboring Pseudomonas aeruginosastrains were identified. These strains possessed a class 1 integron harboring ORF1, blaVIM-2, and aacA4gene cassettes. The transposon-mediated horizontal spread of the blaVIM-2gene among these strains was suggested, which increases the threat that the blaVIM-2gene will disseminate among diverse genera of bacteria.