Isolation, culture and characterization of biliary epithelial cells from different anatomical levels of the intrahepatic and extrahepatic biliary tree from a mouse

Three-dimensional human bile duct formation from chemically induced human liver progenitor cells

Background: The intrahepatic bile ducts (BDs) play an important role in the modification and transport of bile, and the integration between the BD and hepatocytes is the basis of the liver function. However, the lack of a source of cholangiocytes limits in vitro research. The aim of the present study was to establish three-dimensional BDs combined with human mature hepatocytes (hMHs) in vitro using chemically induced human liver progenitor cells (hCLiPs) derived from hMHs. Methods: In this study, we formed functional BDs from hCLiPs using hepatocyte growth factor and extracellular matrix. BDs expressed the typical biliary markers CK-7, GGT1, CFTR and EpCAM and were able to transport the bile-like substance rhodamine 123 into the lumen. The established three-dimensional BDs were cocultured with hMHs. These cells were able to bind to the BDs, and the bile acid analog CLF was transported from the culture medium through the hMHs and accumulated in the lumen of the BDs. The BDs generated from the hCLiPs showed a BD function and a physiological system (e.g., the transport of bile within the liver) when they were connected to the hMHs. Conclusion: We present a novel in vitro three-dimensional BD combined with hMHs for study, drug screening and the therapeutic modulation of the cholangiocyte function.

A postnatal network of co-hepato/pancreatic stem/progenitors in the biliary trees of pigs and humans

A network of co-hepato/pancreatic stem/progenitors exists in pigs and humans in Brunner's Glands in the submucosa of the duodenum, in peribiliary glands (PBGs) of intrahepatic and extrahepatic biliary trees, and in pancreatic duct glands (PDGs) of intrapancreatic biliary trees, collectively supporting hepatic and pancreatic regeneration postnatally. The network is found in humans postnatally throughout life and, so far, has been demonstrated in pigs postnatally at least through to young adulthood. These stem/progenitors in vivo in pigs are in highest numbers in Brunner's Glands and in PDGs nearest the duodenum, and in humans are in Brunner's Glands and in PBGs in the hepato/pancreatic common duct, a duct missing postnatally in pigs. Elsewhere in PDGs in pigs and in all PDGs in humans are only committed unipotent or bipotent progenitors. Stem/progenitors have genetic signatures in liver/pancreas-related RNA-seq data based on correlation, hierarchical clustering, differential gene expression and principal component analyses (PCA). Gene expression includes representative traits of pluripotency genes (SOX2, OCT4), endodermal transcription factors (e.g. SOX9, SOX17, PDX1), other stem cell traits (e.g. NCAM, CD44, sodium iodide symporter or NIS), and proliferation biomarkers (Ki67). Hepato/pancreatic multipotentiality was demonstrated by the stem/progenitors' responses under distinct ex vivo conditions or in vivo when patch grafted as organoids onto the liver versus the pancreas. Therefore, pigs are logical hosts for translational/preclinical studies for cell therapies with these stem/progenitors for hepatic and pancreatic dysfunctions.

An involvement of Hippo-yes-associated protein pathway in biliary epithelial senescence in primary biliary cholangitis

BACKGROUND & AIMS

Accumulating evidence suggest that Hippo-yes-associated protein (YAP) pathway plays important roles in development and repair after injuries in biliary system. We disclosed that senescent biliary epithelial cells (BECs) participate in the pathogenesis of primary biliary cholangitis (PBC). We hypothesized that dysregulation of Hippo-YAP pathway may be associated with biliary epithelial senescence in pathogenesis of PBC.

APPROACH & RESULTS

Cellular senescence was induced in cultured BECs by treatment with serum depletion or glycochenodeoxycholic acid. The expression and activity of YAP1 were significantly decreased in senescent BECs (p<0.01). Cellular senescence and apoptosis were significantly increased (p<0.01) and a proliferation activity and a 3D-cyst formation activity were significantly decreased (p<0.01) by a knockdown of YAP1 in BECs. The expression of YAP1 were immunohistochemically determined in livers taken from the patients with PBC (n = 79) and 79 control diseased and normal livers and its association with senescent markers p16^INK4a and p21^WAF1/Cip1 was analyzed. The nuclear expression of YAP1, which indicates activation of YAP1, was significantly decreased in BECs in small bile ducts involved in cholangitis and ductular reactions in PBC, compared to control livers (p<0.01). The decreased expression of YAP1 was seen in senescent BECs showing expression of p16^INK4a and p21^WAF1/Cip1 in bile duct lesions.

CONCLUSION

Dysregulation of Hippo-YAP1 pathway may be involved in the pathogenesis of PBC in association with biliary epithelial senescence.

Interferon-induced protein with tetratricopeptide repeats 3 may be a key factor in primary biliary cholangitis

Accumulating studies suggest that senescent biliary epithelial cells (BECs) produce senescence-associated secretory phenotypes (SASPs) and play various roles in the pathogenesis of primary biliary cholangitis (PBC) and other cholangiopathies. We examined comprehensive profiles of senescent BECs and its contribution to the pathogenesis of PBC taking advantage of microarray analysis. cDNA microarray analysis revealed that 1841 genes including CCL2, IFIT3, CPQ were commonly up-regulated in senescent BECs cultured in serum depleted media or media with glycochenodeoxycholic acid. Knockdown of IFIT3 significantly suppressed cellular senescence (p < 0.01) and significantly increased apoptosis (p < 0.01) in BECs treated with serum depletion or glycochenodeoxycholic acid. Significantly increased expression of IFIT3 was seen in senescent BECs in small bile ducts showing cholangitis and in ductular reactions in PBC, compared to control livers (p < 0.01). An inadequate response to UDCA was inversely correlated to the increased expression of IFIT3 in small bile duct in PBC (p < 0.05). In conclusion, the expression of various genes related to immunity and inflammation including SASPs were increased in senescent BECs. Upregulated IFIT3 in senescent BECs may be associated with the pathogenesis of PBC and may be a possible therapeutic target in PBC.

Increased p16INK4a-expressing senescent bile ductular cells are associated with inadequate response to ursodeoxycholic acid in primary biliary cholangitis

BACKGROUND & AIMS

Senescent biliary epithelial cells (BECs) may be involved in the pathophysiology of primary biliary cholangitis (PBC) by secreting senescence-associated secretory phenotypes. We examined an association of the extent of cellular senescence in BECs with clinicopathological features including response to ursodeoxycholic acid (UDCA) and a possibility of senolytic therapy in PBC.

METHODS

The expression of senescent markers (p21^WAF1/Cip1, p16^INK4a) and B-cell lymphoma-extra large (Bcl-xL), a key regulator of senescent cell anti-apoptotic pathway, was immunohistochemically examined in livers from patients with PBC (n = 145) and 103 control livers. Senolytic effect of Bcl-xL inhibitors (A-1331852 and Navitoclax) was examined in senescent murine BECs.

RESULTS

Senescent BECs were increased in small bile ducts in PBC, compared with control livers (p < 0.01). Senescent BECs were increased in ductular reactions in PBC, stage 3-4, compared with PBC, stage 1-2 and control livers (p < 0.01). The extent of senescent BECs in bile ductules was significantly correlated with stage and hepatitis activity (p < 0.01) and the expression of p16^INK4a in bile ductules was significantly correlated to inadequate response to UDCA in PBC (p < 0.01). Double immunofluorescence revealed an increased expression of Bcl-xL in p16^INK4a-positive senescent BECs in PBC. Bcl-xL inhibitors selectively induced apoptosis in senescent murine BECs (p < 0.01).

CONCLUSION

The extent of senescent BECs in small bile ducts and bile ductules was closely related to stage and activity of PBC and the increased expression of p16 ^INK4a in bile ductules was correlated with inadequate response to UDCA.

Kras-driven heterotopic tumor development from hepatobiliary organoids

Cancers arising from the biliary tract are refractory to conventional therapies, requiring the development of novel therapeutics. However, only a limited number of genetically engineered mouse models have been created, partly because of time-consuming work required. Besides, liver-specific gene manipulation mostly resulted in concurrent development of hepatocellular carcinoma, another type of liver cancer, and gallbladder-restricted gene targeting is still not feasible. Consequently, establishment of cancer type-specific disease modeling remains a technical challenge. To address this issue, we took an alternative cell-based approach to quickly induce tumorigenesis ex vivo. Specifically, murine primary organoids from liver and gallbladder were transduced with lentiviral vectors to reconstitute genetic alterations common in biliary tract cancers, followed by inoculation in immunodeficient mice. Although any single genetic alteration did not induce tumors, mutant Kras and repression of major tumor suppressors cooperated for tumor development within 2 months. Induced lesions varied among normal, dysplastic and papillary lesions to adenocarcinoma, recapitulating multistep tumorigenesis even in a heterotopic situation. We further demonstrated that two putative oncogenes in intrahepatic cholangiocellular carcinoma, mutant Pik3ca and FGFR2-AHCYL1 fusion, were rather modest drivers for liver-derived organoids, probably requiring additional mutations or hepatic niche to robustly induce full-blown tumors. Thus, we showed that cancer cells could be readily generated from primary cells in the biliary tract, at least in cases where genetic factors play dominant roles. Collectively, this study will likely contribute to gaining mechanistic insights into biliary carcinogenesis and providing valuable resources for drug discovery.

An impaired biliary bicarbonate umbrella may be involved in dysregulated autophagy in primary biliary cholangitis

Dysregulated autophagy may be a central player in trehe pathogenesis of primary biliary cholangitis (PBC) by inducing autoimmune processes via abnormal expression of mitochondrial antigens such as pyruvate dehydrogenase complex, E2 component (PDC-E2) and also by inducing cellular senescence in biliary epithelial cells (BECs) in bile duct lesions in PBC. We examined the association of an impaired "biliary bicarbonate umbrella" due to dysfunction of anion exchanger 2 (AE2) with dysregulated autophagy and cellular senescence in PBC. The expression of AE2 was examined in cultured BECs treated with bile acids such as glycochenodeoxycholic acid (GCDC) and tauro-ursodeoxycholic acid (TUDCA), various cytokines (IL-4, IL-13, IFNγ, TNFα, TGFβ), and serum deprivation. The effect of AE2 knockdown using siRNA on autophagy, cell surface expression of PDC-E2, and cellular senescence was also examined. The expression of AE2 and its association with autophagy-related markers and senescent markers p16^INK4a and p21^WAF1/Cip1 were immunohistochemically determined in livers taken from the patients with PBC (n = 50) and 69 control diseased and normal livers. The expression of AE2 was significantly induced in the cultured BECs shortly treated with GCDC and other stresses, whereas it was significantly decreased in senescent BECs induced by GCDC and other stresses (p < 0.05). Dysregulated autophagy, cell surface expression of PDC-E2, and cellular senescence were significantly increased by knockdown of AE2 (p < 0.05). The expression of AE2 was significantly decreased in cholangitis in PBC, compared to control livers (p < 0.05). The decreased expression of AE2 was correlated with dysregulated autophagy, abnormal expression of PDC-E2, and cellular senescence in bile duct lesions in PBC. In conclusion, an impaired biliary bicarbonate umbrella may be involved in the pathogenesis of PBC by inducing dysregulated autophagy.

Expression and localization of sterile alpha motif domain containing 5 is associated with cell type and malignancy of biliary tree

Cholangiocarcinoma (CC) is a type of relatively rare neoplasm in adenocarcinoma. The characteristics of CCs as well as biliary epithelial cells are heterogeneous at the different portion of the biliary tree. There are two candidate stem/progenitor cells of the biliary tree, i.e., biliary tree stem/progenitor cell (BTSC) at the peribiliary gland (PBG) of large bile ducts and liver stem/progenitor cell (LPC) at the canals of Hering of peripheral small bile duct. Although previous reports suggest that intrahepatic CC (ICC) can arise from such stem/progenitor cells, the characteristic difference between BTSC and LPC in pathological process needs further investigation, and the etiology of CC remains poorly understood. Here we show that Sterile alpha motif domain containing 5 (SAMD5) is exclusively expressed in PBGs of large bile ducts in normal mice. Using a mouse model of cholestatic liver disease, we demonstrated that SAMD5 expression was upregulated in the large bile duct at the hepatic hilum, the extrahepatic bile duct and PBGs, but not in proliferating intrahepatic ductules, suggesting that SAMD5 is expressed in BTSC but not LPC. Intriguingly, human ICCs and extrahepatic CCs exhibited striking nuclear localization of SAMD5 while the normal hilar large bile duct displayed slight-to-moderate expression in cytoplasm. In vitro experiments using siRNA for SAMD5 revealed that SAMD5 expression was associated with the cell cycle regulation of CC cell lines. Conclusion: SAMD5 is a novel marker for PBG but not LPC in mice. In humans, the expression and location of SAMD5 could become a promising diagnostic marker for the cell type as well as malignancy of bile ducts and CCs.

A Modified Method for Purifying Gallbladder Epithelial Cells Using Fluorescence-activated Cell Sorting

BACKGROUND

We have previously reported a procedure for isolating and culturing biliary epithelial cells (BECs). The aim of this study was to reconsider the method for obtaining pure BECs using the mouse gallbladder.

MATERIALS AND METHODS

Cells that were obtained from the gallbladder alone were sorted by fluorescence-activated cell sorting (FACS) for purifying based on the expression of the epithelial cell adhesion molecule (EpCAM). The viability rate was measured based on the negative expression of 7-aminoactinomycin D (7-AAD).

RESULTS

More than 75% of cells from the gallbladder were determined to be pure BECs. An analysis of the EpCAM revealed that 73.3% of the cells were 7-AAD-negative. Finally, the 0.82×10⁶ pure BECs that survived were obtained and seeded on a collagen gel plate. However, these pure BECs showed almost no proliferation.

CONCLUSION

Pure BECs could be accumulated using FACS. However, the number of BECs was insufficient for the culturing process.

Development and functional characterization of extrahepatic cholangiocyte lines from normal rats

BACKGROUND

Since limited in vitro tools exist for evaluating the pathophysiology of extrahepatic bile ducts, we aim to develop an extrahepatic cholangiocyte culture system from normal rats.

METHODS

Extrahepatic ducts were dissected from rats, cut in half length-wise and cultured on collagen-I coated plates. Transepithelial electrical resistance was measured. At ∼85% confluence, in extrahepatic cholangiocytes we measured: (i) cell size and distribution, and expression for cytokeratin-19, secretin, secretin receptor and somatostatin receptor type II (SSTR2), cystic fibrosis transmembrane conductance regulator (CFTR), chloride bicarbonate anion exchanger 2 (AE2), vascular endothelial growth factor-A (VEGF-A) and nerve growth factor (NGF); and (ii) the effect of secretin and/or somatostatin on 3'-5'-cyclic adenosine monophosphate (cAMP) levels and proliferation.

RESULTS

Cytokeratin-positive extrahepatic cholangiocytes were cultured for 6 passages to form a cell monolayer. Cholangiocytes proliferated to confluence over a 2-week period. The size of extrahepatic cholangiocytes averaged ∼16 μm. Extrahepatic ducts and cholangiocytes were positive for secretin, secretin receptor and SSTR2, CFTR, AE2, VEGF-A and NGF. In extrahepatic cholangiocyte cultures, secretin increased cAMP (prevented by somatostatin), chloride efflux and proliferation.

CONCLUSIONS

Extrahepatic cholangiocyte cultures may be important for studying diseases targeting extrahepatic cholangiocytes such as biliary atresia.

Clonorchis sinensis excretory/secretory products promote the secretion of TNF-alpha in the mouse intrahepatic biliary epithelial cells via Toll-like receptor 4

Background

Toll-like receptor 4 (TLR4), as one of the most important pathogen pattern recognitions (PPRs) plays a central role in elicitation of innate immunity and mediation of adaptive responses against foreign antigens. However, little is known of the roles of TLR4 in the immune responses of biliary epithelial cells (BECs) induced by Clonorchis sinensis, a parasite of significance in human health.

Methods

In the present study, the primary mouse intrahepatic biliary epithelial cells (MIBECs) were pre-treated with TLR4 inhibitor peptide or control peptide and then stimulated by excretory/secretory products (ESP) of C. sinensis, respectively. The expressions of TLR4 and relative cytokines were determined using western blot and a bead-based analytic detection system, respectively.

Results

The results showed that ESP of C. sinensis significantly increased the expression of TLR4 which promoted the expression of MyD88 and NF-κB in BECs; the levels of TNF-α but not IL-6 from MIBECs stimulated by ESP alone were also considerably increased, compared with the group of the medium stimulated. However, the concentration of TNF-α was significantly decreased when MIBECs were pre-treated with TLR4 inhibitor. In addition, ESP could depress the level of IL-6 in MIBECs which was elevated by LPS.

Conclusions

Our data for the first time demonstrate that ESP of C. sinensis can potently induce secretion of pro-inflammatory cytokines via TLR4 in MIBECs, which suggests that TLR4 plays an important role in host defenses against C. sinensis and the pathogenesis of clonorchiasis.

A possible involvement of endoplasmic reticulum stress in biliary epithelial autophagy and senescence in primary biliary cirrhosis

BACKGROUND

Deregulated autophagy followed by cellular senescence in biliary epithelial cells (BECs) may be closely related to the abnormal expression of mitochondrial antigens and following autoimmune pathogenesis in primary biliary cirrhosis (PBC). We examined an involvement of endoplasmic reticulum (ER) stress in the deregulated autophagy and cellular senescence in PBC.

METHODS

We examined the degree of ER stress using markers; glucose-regulated protein 78 (GRP78) and protein disulfide isomerases (PDI), autophagy and cellular senescence in cultured BECs treated with an ER stress inducer, tunicamycin (TM), glycochenodeoxycholic acid (GCDC), and palmitic acid (PA), and the effect of pretreatment with tauroursodeoxycholic acid (TUDCA). We examined the expression of PDI and GRP78 in livers taken from the patients with PBC (n = 43) and 75 control livers.

RESULTS

The expression of ER stress markers was significantly increased in cultured BECs treated with TM, GCDC or PA in BECs (p < 0.05), and pretreatment with TUDCA significantly suppressed the induced ER stress (p < 0.05). Autophagy, deregulated autophagy, and cellular senescence were induced in BECs treated with TM, GCDC, or PA. Pretreatment with TUDCA further increased autophagy in BECs treated with PA and suppressed cellular senescence caused by treatments with TM, GCDC, or PA (p < 0.05). A granular expression of PDI and GRP78 was significantly more extensive in small bile ducts in PBC, compared with control livers (p < 0.05). The expression of GRP78 was seen in senescent BECs in PBC.

CONCLUSIONS

ER stress may play a role in the pathogenesis of deregulated autophagy and cellular senescence in biliary epithelial lesions in PBC.

Human parenchymal and non-parenchymal liver cell isolation, culture and characterization

Many reports describing parenchymal liver cell isolation have been published so far. However, recent evidence has clearly demonstrated that non-parenchymal liver cells play an important role in many pathophysiologies of the liver, such as drug-induced liver diseases, inflammation, and the development of liver fibrosis and cirrhosis. In this study, we present an overview of the current methods for isolating and characterizing parenchymal and non-parenchymal liver cells.

Increased expression of mitochondrial proteins associated with autophagy in biliary epithelial lesions in primary biliary cirrhosis

BACKGROUND/AIMS

We have reported the involvement of deregulated autophagy and subsequent cellular senescence in biliary epithelial lesions in primary biliary cirrhosis (PBC). Given that mitochondria are a major target of autophagy, we hypothesized that deregulated autophagy of mitochondria may be involved in autoimmune pathogenesis in PBC.

METHODS

We examined immunohistochemically the expression of pyruvate dehydrogenase complex-E2 component (PDC-E2) and cytochrome c oxidase, subunit I (CCO), in livers taken from patients with PBC (n = 42) and control livers (n = 76). The colocalization of mitochondrial antigens with an autophagy marker microtubule-associated protein-light chain 3β (LC3), a deregulated autophagy marker p62/sequestosome-1 (p62) and a lysosomal marker LAMP-1 was examined by double immunofluorescence. We examined the colocalization of mitochondrial antigens with LC3, p62 and LAMP-1 and the cell-surface expression of PDC-E2 in cultured biliary epithelial cells (BECs) treated with various stresses.

RESULTS

Intense granular expression of PDC-E2 and CCO was seen in the damaged small bile ducts (SBDs) in PBC and the expression was significantly more frequent in PBC than in control livers (P < 0.01). The granular expression of mitochondrial antigens was colocalized with LC3 in damaged SBDs in PBC. The accumulation of LC3-expressing punctae colocalized with PDC-E2 and CCO was significantly more increased in cultured BECs treated with various stresses. The cell-surface expression of PDC-E2 was induced by various stresses in BECs.

CONCLUSION

Deregulated autophagy may contribute to the abnormal expression of mitochondrial antigens and may be involved in the autoimmune pathogenesis of bile duct lesions in PBC.

Tissue culture correlational study of genetic cholangiopathy of autosomal recessive polycystic kidney disease

Cholangiocytes are epithelial cells that line the biliary tract and are also known as biliary epithelial cells (BECs). In vitro culture studies of BECs in correlation with tissue section examination may give us a comprehensive analysis of biliary tract diseases. Herein, we discuss genetic cholangiopathy of autosomal recessive polycystic kidney disease (ARPKD), mainly using a polycystic kidney (PCK) rat, an animal model of ARPKD. The hepatobiliary lesions in ARPKD patients (Caroli's disease and congenital hepatic fibrosis) and in PCK rats are speculated to be related to mutations to polycystic kidney and hepatic disease 1 (PKHD1) which have been recently demonstrated, though the exact causal relation between these mutations and hepatobiliary pathology remain to be clarified. Recently we clarified that BECs of PCK rat showed increased cell proliferation followed by irregular dilatation of intrahepatic bile ducts. We also identified the essential involvement of the MEK5-ERK5 pathway in the abnormal proliferation of BECs in the PCK rat. The degradation of laminin and type IV collagen (basal membrane components of bile ducts) was closely related to the biliary dysgenesis and cystogenesis in the PCK rats. BECs also showed mesenchymal phenotype followed by progressive portal tract fibrosis, indicating TGF-β1 may be involved in this acquisition of mesenchymal phenotype. Detailed tissue culture correlation studies of ARPKD and PCK rats are mandatory to evaluate the pathogenesis of this genetic cholangiopathy.

A possible involvement of p62/sequestosome-1 in the process of biliary epithelial autophagy and senescence in primary biliary cirrhosis

BACKGROUND AND AIMS

Given autophagy is involved in the pathogenesis in primary biliary cirrhosis (PBC), we examined an involvement of p62 sequestosome-1 (p62), a specific cargo for autophagy, in the process of autophagy and cellular senescence in PBC.

METHODS

We examined immunohistochemically the expression of p62 in livers taken from patients with PBC (n = 46) and control livers (n = 78) and its colocalization with microtubule-associated proteins-light chain 3β (LC3), lysosome-associated membrane protein-1 (LAMP-1) and senescent markers (p16(INK) (4a) and p21(WAF) (1/Cip1) ). We examined the expression of p62 and LC3 in cultured biliary epithelial cells (BECs) treated with various stress. The effect of p62 knockdown with siRNA on stress-induced autophagy and cellular senescence was also assessed.

RESULTS

The expression of p62 was specifically seen in cytoplasmic aggregates in BECs in the inflamed and damaged small bile ducts (SBDs) in PBC, when compared with non-inflamed ones in PBC and in control livers (P < 0.01). The co-expression of p62 with LC3, LAMP-1 and senescent markers was seen in the inflamed SBDs in PBC, but the intracytoplasmic localization was different. The expression of p62 and LC3 was significantly upregulated in BECs treated with various stress (P < 0.01) and pretreatment with bafilomycin A1 enhanced the accumulation of p62-positive aggregates in BECs with serum deprivation. The knockdown of p62 decreased stress-induced autophagy and cellular senescence.

CONCLUSION

The aggregation of p62 is specifically increased in the damage bile ducts in PBC and may reflect dysfunctional autophagy, followed by cellular senescence in the pathogenesis of bile duct lesions in PBC.

The biliary tree--a reservoir of multipotent stem cells

The biliary tree is composed of intrahepatic and extrahepatic bile ducts, lined by mature epithelial cells called cholangiocytes, and contains peribiliary glands deep within the duct walls. Branch points, such as the cystic duct, perihilar and periampullar regions, contain high numbers of these glands. Peribiliary glands contain multipotent stem cells, which self-replicate and can differentiate into hepatocytes, cholangiocytes or pancreatic islets, depending on the microenvironment. Similar cells-presumably committed progenitor cells-are found in the gallbladder (which lacks peribiliary glands). The stem and progenitor cell characteristics indicate a common embryological origin for the liver, biliary tree and pancreas, which has implications for regenerative medicine as well as the pathophysiology and oncogenesis of midgut organs. This Perspectives article describes a hypothetical model of cell lineages starting in the duodenum and extending to the liver and pancreas, and thought to contribute to ongoing organogenesis throughout life.

A novel method for establishment and characterization of extrahepatic bile duct epithelial cells from mice

Culture of extrahepatic bile duct epithelial cells is a useful model to investigate physiology of extrahepatic bile duct epithelia and hepatobiliary disease mechanisms. The aim of this work was to establish and characterize a primary murine extrahepatic bile duct epithelial cell culture. Epithelial cells were isolated from extrahepatic bile ducts of BALB/c mice that were intraperitoneally injected with newborn bovine serum to induce the proliferation of extrahepatic bile ducts' epithelial cells and cultured on rat tail type I collagen-coated plastic culture flask containing DMEM/HamF12 with 10% FBS and 10 ng/ml epidermal growth factor at 37°C in an incubator with 5% humidified CO(2). The cells showed typical morphologic characteristics of epithelial phenotypes with cobblestone appearance in monolayer within 5-6 d after culture; they were positive against anticytokeratin-19 immunostaining. Transmission electron microscopy showed typical bile duct epithelia with microvilli on the cytomembrane, Golgi complex, massive mitochondria, and rough endoplasmic reticulum in the cytoplasmic. The growth curve of the epithelial cells was determined by a MTT assay which showed a normal sigmoidal growth curve. This culture technique might be a reliable method for isolation, purification, and primary culture of extrahepatic bile duct epithelial cells that can serve as a model for in vitro studies on the pathophysiology of hepatobiliary diseases as well as pharmacological and toxicological targets relevant to hepatobiliary diseases.

Autophagy mediates the process of cellular senescence characterizing bile duct damages in primary biliary cirrhosis

Recent studies disclosed that autophagy is induced during and facilitates the process of senescence. Given that biliary epithelial cells (BECs) in damaged small bile ducts in primary biliary cirrhosis (PBC) show senescent features, we examined an involvement of autophagy in the process of biliary epithelial senescence in PBC. We examined immunohistochemically the expression of microtubule-associated proteins-light chain 3beta (LC3), a marker of autophagy, in livers taken from the patients with PBC (n=37) and control livers (n=75). We also examined the co-localization of LC3 with autophagy-related cathepsin D, lysosome-associated membrane protein-1 (LAMP-1), and senescent markers, p16(INK4a) and p21(WAF1/Cip1). We examined the effect of autophagy inhibitor (3-methyladenine) on the induction of cellular senescence and senescence-associated secretion (CCL2 and CX3CL1) in cultured murine BECs. The expression of LC3 was specifically seen in vesicles in BECs in the inflamed and damaged small bile ducts in PBC, when compared with non-inflamed small bile ducts in PBC and in control livers (P<0.01). The expression of LC3 was closely related to the expression of cathepsin D, LAMP-1, and senescent markers. In cultured BECs, oxidative stress, DNA damage, and serum deprivation induced cellular senescence, when compared with control and the inhibition of autophagy significantly decreased the stress-induced cellular senescence (P<0.01). Furthermore, the secretion level of CCL2 and CX3CL1 increased significantly by various stress and suppressed by the inhibition of autophagy (P<0.01). In conclusion, autophagy is specifically seen in the damaged small bile ducts along with cellular senescence in PBC. The inhibition of autophagy suppressed cellular senescence in cultured cells. These findings suggest that autophagy may mediate the process of biliary epithelial senescence and involve in the pathogenesis of bile duct lesions in PBC.

SNP analysis of genes implicated in T cell proliferation in primary biliary cirrhosis

Previous studies on primary biliary cirrhosis (PBC) have focused on the role of T lymphocytes as potential effectors of tissue injury. We hypothesized that single nucleotide polymorphisms (SNPs) of genes involved in lymphocyte proliferation would be responsible for uncontrolled expansion of T cells and autoreactivity. To address this, we genotyped DNA from 154 patients with PBC and 166 ethnically matched healthy controls for SNPs of five candidate genes (60G/A CTLA-4, 1858 C/T LYP, -IVS9 C/T foxp3, p1323 C/G ICOS and -9606 T/C CD25) using a TaqMan assay.

We report herein a statistically significant decrease in homozygosity rate for the 60A⋆CTLA-4 allele in patients with PBC compared to controls (p = 0.0411). Moreover, we found a significant association of the same allele and of the LYP⋆T allele with anti-mitochondrial antibody (AMA) serum negativity (p = 0.0304 and 0.0094, respectively). No association between any of the other studied SNPs and PBC susceptibility, progression, or AMA status was observed. In conclusion, given the high prevalence of SNPs in CTLA-4 detected in numerous autoimmune diseases, we encourage a more detailed genetic analysis of this candidate gene. Further, although obtained from a limited number of AMA-negative subjects, our data suggest a potential genetic heterogeneity for this specific subgroup of patients with PBC.

Death receptor 5 mediated-apoptosis contributes to cholestatic liver disease

Chronic cholestasis often results in premature death from liver failure with fibrosis; however, the molecular mechanisms contributing to biliary cirrhosis are not demonstrated. In this article, we show that the death signal mediated by TNF-related apoptosis-inducing ligand (TRAIL) receptor 2/death receptor 5 (DR5) may be a key regulator of cholestatic liver injury. Agonistic anti-DR5 monoclonal antibody treatment triggered cholangiocyte apoptosis, and subsequently induced cholangitis and cholestatic liver injury in a mouse strain-specific manner. TRAIL- or DR5-deficient mice were relatively resistant to common bile duct ligation-induced cholestasis, and common bile duct ligation augmented DR5 expression on cholangiocytes, sensitizing mice to DR5-mediated cholangitis. Notably, anti-DR5 monoclonal antibody-induced cholangitis exhibited the typical histological appearance, reminiscent of human primary sclerosing cholangitis. Human cholangiocytes constitutively expressed DR5, and TRAIL expression and apoptosis were significantly elevated in cholangiocytes of human primary sclerosing cholangitis and primary biliary cirrhosis patients. Thus, TRAIL/DR5-mediated apoptosis may substantially contribute to chronic cholestatic disease, particularly primary sclerosing cholangitis.

Proinflammatory cytokine-induced cellular senescence of biliary epithelial cells is mediated via oxidative stress and activation of ATM pathway: a culture study

Cellular senescence is reportedly involved in cholangiopathy in primary biliary cirrhosis and oxidative stress is proposed as a pathogenetic factor in biliary epithelial cells (BECs). This study investigated the involvement of proinflammatory cytokines (IFN-beta, IFN-gamma and TNF-alpha) and ataxia telangiectasia-mutated (ATM)/p53/ p21(WAF1/Cip1) pathway with respect to oxidative stress in cellular senescence of BECs. H(2)O(2) treatment (oxidative stress) induced phosphorylation (activation) of ATM and p53 and also p21(WAF1/Cip1) expression in BECs. Treatment with inflammatory cytokines generated reactive oxygen species (ROS) in cultured BECs followed by activation of the ATM/p53/p21(WAF1/Cip1) pathway and the induction of cellular senescence. Pre-treatment with ATM inhibitor (2-aminopurine) and antioxidant (N-acetylcysteine) significantly blocked the cellular senescence of BECs induced by oxidative stress or inflammatory cytokines. In conclusion, proinflammatory cytokines induce ROS generation and activate the ATM/p53/p21(WAF1/Cip1) pathway, followed by biliary epithelial senescence. This senescent process may be involved in the development of destructive cholangiopathy in humans.

Involvement of Escherichia coli in pathogenesis of xanthogranulomatous cholecystitis with scavenger receptor class A and CXCL16-CXCR6 interaction

Xanthogranulomatous cholecystitis (XGC) is characterized by the infiltration of numerous foamy macrophages. Bacterial infection is thought to be involved in the pathogenesis of XGC. Using XGC and cultured murine biliary epithelial cells (BEC), the participation of E. coli and the role of the scavenger receptor class A (SCARA), as well as chemokine(C-X-C motif) ligand 16 (CXCL16) and its receptor chemokine(C-X-C motif) receptor 6 (CXCR6), were examined in the pathogenesis of XGC. E. coli components and genes were detected in XGC on immunohistochemistry and polymerase chain reaction (PCR), respectively. SCARA-recognizing E. coli was found in foamy macrophages aggregated in xanthogranulomatous lesions. CXCL16, which functions as a membrane-bound molecule and soluble chemokine to induce adhesion and migration of CXCR6(+) cells, was detected on gallbladder epithelia, and CXCR6(+)/CD8(+) T cells and CXCR6(+)/CD68(+) macrophages were also accumulated. In cultured BEC, CXCL16 mRNA and secreted soluble CXCL16 were constantly detected and upregulated by treatment with E. coli and lipopolysaccharide through Toll-like receptor 4. These suggest that SCARA in macrophages is involved in the phagocytosis of E. coli followed by foamy changes and that bacterial infection causes the upregulation of CXCL16 in gallbladder epithelia, leading to the chemoattraction of macrophages via CXCL16-CXCR6 interaction and formation of the characteristic histology of XGC.

Decreased expression of Bmi1 is closely associated with cellular senescence in small bile ducts in primary biliary cirrhosis

Cellular senescence of biliary epithelial cells with p16INK4a and p21WAF1/Cip expression in damaged small bile ducts may be critical for progressive bile duct loss in primary biliary cirrhosis. We investigated the involvement of bmi1, a polycomb group gene repressing p16INK4a expression, in the pathogenesis of biliary cellular senescence. Bmi1 expression was examined immunohistochemically in livers taken from the patients with primary biliary cirrhosis (n=18) and other diseased (n=19) and normal livers (n=16). We examined the effect of oxidative stress and a short interference RNA (siRNA) targeting bmi1 on cellular senescence in cultured mouse biliary epithelial cells. Bmi1 was widely expressed in the nuclei of biliary epithelial cells in the control livers. In contrast, bmi1 expression was significantly decreased in damaged small bile ducts in 43% of livers with primary biliary cirrhosis of stage 1/2, coordinating with the increased p16INK4a expression. In cultured biliary epithelial cells, oxidative stress by H2O2 treatment significantly decreased bmi1 expression, followed by increased P16INK4a expression. A knockdown of bmi1 induced increased p16INK4a expression, decreased cell proliferation, and increased cellular senescence. In conclusion, the decreased bmi1 expression caused by oxidative stress may be involved in the pathogenesis of cellular senescence of biliary epithelial cells in primary biliary cirrhosis.

Development and characterization of a cholangiocyte cell line from the PCK rat, an animal model of Autosomal Recessive Polycystic Kidney Disease

In the PCK rat, a rodent model of Autosomal Recessive Polycystic Kidney Disease (ARPKD), a spontaneous splicing mutation of Pkhd1 initiates hepatic cyst development. Cystic cholangiocytes possess short and malformed cilia that do not express fibrocystin, the Pkhd1 protein. During the disease course, cysts continue to grow; however, the mechanisms underlying cyst progression are unclear due in part to the lack of suitable cell lines to study cystogenesis. Here, we describe the development of a PCK-derived cholangiocyte cell line (PCK-CCL). Normal rat cholangiocytes (NRCs) were used as a control. The PCK-CCL maintained a cholangiocyte phenotype as assessed by the expression of the CK-19, CK-7 and GGT. PCK-CCL grown on collagen formed a polarized monolayer with well-developed junctional complexes, and distinct apical and basolateral membranes. Compared to NRCs, cilia in the PCK-CCL were short and malformed and did not express fibrocystin. The PCK-CCL exhibited a higher rate of proliferation (P<0.05) with a doubling time approximately half that of NRCs. By RT-PCR analysis of exons 33-37, an approximately 800 bp product of Pkhd1 was amplified in NRCs. In contrast and as expected, in the PCK-CCL, the Pkhd1 amplicon was smaller ( approximately 630 bp) reflecting the IVS35-2A --> T mutation. PCK-CCL and NRCs seeded in 3-D cultures formed cystic structures; however, the PCK cysts expanded progressively up to day 21 while cysts formed by NRCs remained the same size after day 9. In summary, we have developed a cholangiocyte cell line from the PCK rat that retains properties of the cholangiocytes lining hepatic cysts in vivo. The cells have been grown continuously for approximately 18 month and 45 passages without crisis or senescence. The morphology and growth characteristics of the PCK-CCL are consistent with those seen in vivo in the PCK rat, suggesting that this cell line will be useful in dissecting the mechanisms of hepatic cyst formation.

Augmented expression of hepatocytes growth factor activator inhibitor type 1 (HAI-1) in intrahepatic small bile ducts in primary biliary cirrhosis

The repair system of damaged biliary mucosa was not fully clarified so far in primary biliary cirrhosis (PBC). Given that related factors of the hepatocyte growth factor (HGF) such as HGF activator (HGFA) and HGFA inhibitor type 1 (HAI-1) participate in the repair of injured gastrointestinal mucosa, we investigated the involvement of the HGF/HGFA/HAI-1 system in PBC and control livers. The expression of HGFA, HAI-1, and c-Met was examined in PBC livers (n=24), diseased livers (control, n=30), and normal livers (n=15) by immunohistochemistry and semiquantitative reverse transcriptase-polymerase chain reaction. We examined the expression of HGFA, HAI-1, and c-Met, and the effect of HGF administration on cell proliferation and wound healing, and HAI expression in cultured mouse biliary epithelial cells (BECs). HAI-1 expression was faint in control livers, whereas it was significantly augmented in damaged small bile ducts, bile ductules, and periportal hepatocytes in PBC (p<0.05). HGFA and c-Met were homogeneously expressed in BECs in PBC and control livers. HAI-1 expression was increased at the front of wound healing and the treatment with HGF-enhanced HAI-1 expression, cell proliferation, and wound healing in cultured BECs. HGF/HGFA/HAI-1 system may participate in biliary mucosal repair as reported in gastrointestinal mucosal repair.

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.

Genes and (auto)immunity in primary biliary cirrhosis

Primary biliary cirrhosis (PBC) is a chronic autoimmune cholestatic liver disease most commonly encountered in postmenopausal women; it is characterized by high-titer serum autoantibodies to mitochondrial antigens, elevated serum IgM, progressive destruction of intrahepatic bile ducts, and ultimately liver cirrhosis and failure. The cytopathic mechanisms leading to the selective destruction of intrahepatic cholangiocytes are still largely unknown. The current theory on the pathogenesis of PBC indicated that environmental factors might trigger autoimmunity in genetically susceptible individuals. In fact, genetic predisposition is critical to disease onset and progression, yet peculiar among autoimmune diseases, as indicated by the lack of a strong association with major histocompatibility complex haplotypes. Further, the recently reported concordance rate among monozygotic twins strengthens the importance of genetic factors, while also indicating that additional factors, possibly infectious agents or xenobiotics, intervene to trigger the disease. In this review, the available data regarding the genetic factors associated with PBC susceptibility and progression, as well as the available evidence regarding the immunomediated pathogenesis of PBC, will be critically illustrated and discussed.

Frequent cellular senescence in small bile ducts in primary biliary cirrhosis: a possible role in bile duct loss

The pathogenesis of progressive bile duct loss in primary biliary cirrhosis remains unclear. In this study, the involvement of cellular senescence of biliary epithelial cells was examined in liver tissue samples from patients with primary biliary cirrhosis (n = 33), and compared with control diseased and normal livers (n = 83). In addition, cellular senescence was induced by oxidative stress in cultured mouse biliary epithelial cells. Biliary epithelial cells in small bile ducts in primary biliary cirrhosis, especially those in patients presenting with chronic non-suppurative cholangitis, frequently expressed senescence-associated beta-galactosidase, and senescence-associated p16(INK4) and p21(WAF1/CIP). In contrast, senescence-associated markers were rarely expressed in small bile ducts in control livers. The infiltration of myeloperoxidase-positive inflammatory cells into biliary epithelial cell layers was closely associated with the cellular senescence of biliary epithelial cells in early-stage PBC. Cellular senescence of cultured mouse biliary epithelial cells was induced by treatment with H2O2 via the p38MAPK-dependent pathway and nitric oxide-augmented H2O2-induced cellular senescence. Oxidative stress- and nitric oxide-mediated cellular senescence may be involved in bile duct lesions, which are followed by progressive bile duct loss in primary biliary cirrhosis.

Intrahepatic cholangiocarcinoma escapes from growth inhibitory effect of transforming growth factor-beta1 by overexpression of cyclin D1

Transforming growth factor-beta1 (TGF-beta1) is involved in tumor progression by promoting angiogenesis or suppressing the immune system; yet TGF-beta1 also has a growth-inhibitory effect on epithelial cells including carcinoma cells. Several mechanisms of impaired TGF-beta1 responsiveness of carcinoma cells have been reported. In this study, we examined how TGF-beta1 participates in the development and progression of intrahepatic cholangiocarcinoma (ICC) associated with hepatolithiasis, and how ICC cells escape from growth inhibitory effect of TGF-beta1. A total of 40 cases of hepatolithiasis were studied, including 16 cases of ICC, and in vitro studies were conducted with cultured murine non-neoplastic biliary epithelial cells (MBEC) and three ICC cell lines. Immunohistochemically, TGF-beta1 was expressed in mononuclear cells and mesenchymal cells around the stone-containing bile ducts and invasive ICC, and also in biliary epithelial cells (hyperplastic and precursor lesions, and ICC). TGF-beta type II receptor (TbetaR-II) was constantly expressed on biliary epithelial cells irrespective of biliary lesions. In cell culture studies, TGF-beta1 significantly inhibited proliferation of MBEC via downregulation of cyclin D1, cdk4, and cdk6, while TGF-beta1 did not influence the proliferation of ICC cells. After suppression of cyclin D1 expression in one ICC cell line using cyclin D1 small interfering RNA, TGF-beta1 significantly inhibited the proliferation of ICC cells. In conclusion, high levels of TGF-beta1 around ICC or its precursors may be involved in development and progression of ICC in hepatolithiasis. ICC cells could escape the growth inhibitory effect of TGF-beta1 by overexpression of cyclin D1.

Activation of the MEK5/ERK5 cascade is responsible for biliary dysgenesis in a rat model of Caroli's disease

Polycystic kidney (PCK) rats exhibit a multiorgan cyst pathology similar to human autosomal recessive polycystic kidney disease, and are proposed as an animal model of Caroli's disease with congenital hepatic fibrosis (CHF). This study investigated the expression and function of selected components of the mitogen activated protein kinase (MAPK) pathway in cultured intrahepatic biliary epithelial cells (BECs) of PCK rats. Compared to the proliferative activity of cultured BECs of control rats, those of the PCK rats were hyperresponsive to epidermal growth factor (EGF). The increase in BEC proliferation was accompanied by overexpression of MAPK/extracellular signal-regulated protein kinase (ERK) kinase 5 (MEK5), and subsequent phosphorylation of ERK5 in vitro. The increased proliferative activity was significantly inhibited by the transfection of short interfering RNA against MEK5 mRNA. An EGF receptor tyrosine kinase inhibitor, gefitinib ("Iressa", ZD1839), also significantly inhibited the abnormal growth of cultured BECs of PCK rats. By contrast, treatment with PD98059 and U0126, inhibitors for MEK1/2, was less effective. These results suggest that the activation of the MEK5-ERK5 cascade plays a pivotal role in the biliary dysgenesis of PCK rats, and also provide insights into the pathogenesis of Caroli's disease with CHF. As the MEK5-ERK5 interaction is highly specific, it may represent a potential target of therapy.

Keratin-8 null mice have different gallbladder and liver susceptibility to lithogenic diet-induced injury

Keratin transgenic mouse models and the association of human keratin mutations with liver disease highlight the importance of keratins in protecting the liver from environmental insults, but little is known regarding keratins and their function in the gallbladder. We characterized keratin expression pattern and filament organization in normal and keratin polypeptide-8 (K8)-null, K18-null and K19-null gallbladders, and examined susceptibility to liver and gallbladder injury induced by a high-fat lithogenic diet (LD) in K8-null mice. The major keratins of normal mouse gallbladder are K8>K19>K18 which become markedly depleted in K8-null mice with minor K18/K19 remnants and limited K7 over-expression. Compensatory K18/K20 protein and RNA overexpression occur in K19-null but not in K18-null gallbladders, probably because of the higher levels of K19 than K18 in normal gallbladder. LD challenge causes more severe liver injury in K8-null than wild-type mice without altering keratin protein levels. In contrast, wild-type and K8-null gallbladders are equally susceptible to LD-induced injury and stone formation, but wild-type gallbladders do overexpress keratins upon LD challenge. LD-induced injury triggers keratin hyperphosphorylation in wild-type livers and gallbladders. Hence, mouse gallbladder K8/K18/K19 expression is induced in response to cholelithiasis injury. A high-fat LD increases the susceptibility of K8-null mice to liver but not gallbladder injury, which suggests that keratin mutations may increase the risk of liver damage in patients with steatohepatitis. Differences between K8-null mouse gallbladder and hepatocyte susceptibility to injury may be related to their minimal versus absent keratin expression, respectively.

Lipopolysaccharide activates nuclear factor-kappaB through toll-like receptors and related molecules in cultured biliary epithelial cells

To clarify the innate immunity of the intrahepatic biliary tree, we examined expression of Toll-like receptors and intracellular signalings in biliary epithelial cells in response to bacterial components by using cultured biliary epithelial cells (murine biliary cells and human cholangiocarcinoma cell lines). The expression of Toll-like receptors in cultured cells was examined by reverse transcription and PCR and immunohistochemistry. Intracellular signalings after Toll-like receptors activation by lipopolysaccharide was examined by analysis of nuclear factor (NF)-kappaB activation and inhibition studies using inhibitors for NF-kappaB and mitogen-activated protein kinase and blocking antibody. The mRNAs of Toll-like receptors 2, 3, 4, and 5, and related molecules (MD-2, MyD88, and CD14) were detected, and their proteins were expressed in cultured cells. Lipopolysaccharide was shown to bind to the cell surface of cultured cells. Lipopolysaccharide treatment induced the production of TNF-alpha, and nuclear translocation of NF-kappaB and increased NF-kappaB-DNA binding in cultured cells. This induction of TNF-alpha was partially inhibited by anti-Toll-like receptor 4 antibody. The nuclear translocation and increased binding of NF-kappaB by lipopolysaccharide were blocked by addition of MG132, an inhibitor of NF-kappaB. In conclusion, lipopolysaccharide appears to form a receptor complex of CD14, Toll-like receptor 4, MD-2, and MyD88 in cultured biliary epithelial cells and seems to regulate activation of NF-kappaB and synthesis of TNF-alpha. The recognition of pathogen-associated molecular patterns using Toll-like receptors and related molecules in biliary epithelial cells, which is demonstrated in this in vitro study, may participate in an immunopathology of the intrahepatic biliary tree in vivo.

Lipopolysaccharide induces overexpression of MUC2 and MUC5AC in cultured biliary epithelial cells: possible key phenomenon of hepatolithiasis

Bacterial infection, bile stasis, mucin hypersecretion, and an alteration of the mucin profile such as an aberrant expression of gel-forming apomucin (MUC2 and MUC5AC) in the intrahepatic biliary tree are thought to be important in the lithogenesis of hepatolithiasis. So far, there have been no detailed studies linking bacterial infection to altered mucus secretion of biliary epithelium. In this study, the influence of lipopolysaccharide (LPS), a bacterial component, on apomucin expression in cultured murine biliary epithelial cells was examined with emphasis on the participation of tumor necrosis factor (TNF)-alpha. It was found that LPS up-regulated the expression of MUC2 and MUC5AC in cultured murine biliary epithelial cells. LPS also induced the expression of TNF-alpha in biliary epithelial cells and its secretion into the culture medium. The up-regulation of these apomucins was inhibited by pretreatment with TNF-alpha antibody. TNF-alpha alone also induced the overexpression of MUC2 and MUC5AC in cultured biliary epithelial cells. This overexpression was inhibited by pretreatment with calphostin C, an inhibitor of protein kinase C. These findings suggest that LPS can induce overexpression of MUC2 and MUC5AC in biliary epithelial cells via synthesis of TNF-alpha and activation of protein kinase C. This mechanism might be involved in the lithogenesis of hepatolithiasis.

Cytomegalovirus infection and proinflammatory cytokine activation modulate the surface immune determinant expression and immunogenicity of cultured murine extrahepatic bile duct epithelial cells

Murine extrahepatic bile duct epithelial cells (MEBEC) were isolated from extrahepatic bile ducts of BALB/c mice and established in primary culture. The epithelial origin was confirmed by positive cytokeratin 19 staining for these cells and the presence of microvilli and tight junctions under electron microscopy. By immunofluorescent staining with monoclonal antibodies and flow-cytometric analysis, MEBEC in culture constitutively express low levels of intercellular adhesion molecule (ICAM)-1, class I and class II major histocompatibility (MHC) antigens. The expression of ICAM-1 was significantly increased by interferon gamma (INF-gamma) or tumour necrosis factor alpha (TNF-alpha) stimulation. Class I and class II antigen expression were significantly enhanced by INF-gamma and in vitro murine cytomegalovirus (MCMV) infection. MEBEC infected with MCMV revealed a progressive cytopathic effect. MEBEC activated by INF-gamma or infected by MCMV induced a low but significant proliferation of allogeneic T cells and displayed a significant decrease in the absorbance at O.D. 550 nm in a microtitre tetrazolium assay after these treated cells were co-cultured with allogeneic T cells. These results suggest that following the up-regulation of surface MHC antigen and adhesion molecule expression with cytokines or MCMV, the MEBEC can function as antigen-presenting cells and initiate T-cell proliferation, which in turn trigger the recognition of MEBEC by effector T-cell-mediated cytotoxic responses. These findings may be implicated in the pathogenesis of virally induced, immune-mediated extrahepatic bile duct damage disorders.

Duck hepatitis B virus replication in primary bile duct epithelial cells

Primary cultures of intrahepatic bile duct epithelial (IBDE) cells isolated from duckling livers were successfully grown for studies of duck hepatitis B virus (DHBV). The primary IBDE cells were characterized by immunohistochemistry using CAM 5.2, a cytokeratin marker which was shown to react specifically to IBDE cells in duck liver tissue sections and in primary cultures of total duck liver cells. Immunofluorescence assay using anti-duck albumin, a marker for hepatocytes, revealed that these IBDE cultures did not appear to contain hepatocytes. A striking feature of these cultures was the duct-like structures present within each cell colony of multilayered IBDE cells. Normal duck serum in the growth medium was found to be essential for the development of these cells into duct-like structures. When the primary cultures of duck IBDE cells were acutely infected with DHBV, dual-labeled confocal microscopy using a combination of anti-DHBV core proteins and CAM 5.2 or a combination of anti-pre-S1 proteins and CAM 5.2 revealed that the IBDE cell colonies contained DHBV proteins. Immunoblot analysis of these cells showed that the DHBV pre-S1 and core proteins were similar to their counterparts in infected primary duck hepatocyte cultures. Southern blot analysis of infected IBDE preparations using a digoxigenin-labeled positive-sense DHBV riboprobe revealed the presence of hepadnavirus covalently closed circular (CCC) DNA, minus-sense single-stranded (SS) DNA, double-stranded linear DNA, and relaxed circular DNA. The presence of minus-sense SS DNA in the acutely infected IBDE cultures is indicative of DHBV reverse transcriptase activity, while the establishment of a pool of viral CCC DNA reveals the ability of these cells to maintain persistent infection. Taken collectively, the results from this study demonstrated that primary duck IBDE cells supported hepadnavirus replication as shown by the de novo synthesis of DHBV proteins and DNA replicative intermediates.

Pathology of the liver

Among the topics of recent investigation in liver pathology were an examination of normal portal tract structures in needle liver biopsies, computer reconstructions of the intrahepatic biliary tree, identification of oval cells (presumed progeny of hepatic stem cells) in a variety of biliary and nonbiliary diseases and tumors, the features and pathogenesis of nonalcoholic steatohepatitis, and further characterization of proliferating bile ductules. A morphometric study of portal structures in normal needle liver biopsies found that approximately one third in a given specimen may not show a portal vein and that a bile duct may not be seen in 7%. Apoptosis is a critical mechanism for the death of hepatocytes in viral hepatitis and also in endothelial injury in the cold perfusion-warm reperfusion sequence in liver transplantation. The results of two studies examining the relationship of steatosis to chronic hepatitis C virus infection in native and transplanted livers suggest that fatty change is a specific virus-mediated lesion. In the field of hepatic neoplasia, liver cell dysplasia (large cell change), long thought to be a premalignant lesion, was hypothesized to represent abnormal hepatocyte polyploidization.

Generation of monoclonal antibodies to murine bile duct epithelial cells: identification of annexin V as a new marker of small intrahepatic bile ducts

Biliary epithelial cells (BECs) are distributed along the length of both the extrahepatic and intrahepatic biliary tree, but have distinctly different phenotypes and functions according to their anatomical location. It has been reasoned that the distinct appearance of pathogenic lesions in different biliary diseases may be associated with the expression of distinct proteins. These data prompted us to immunize rats with cultured murine BECs with the objective of determining if there are unique antigens on BECs. Of the 45 monoclonal antibodies (mAbs) produced, 12 mAbs (MBEC 1-12) were selected for detailed study based on their classification into three major groups. These groups included four antibodies (MBEC 1-4) that reacted in a staining pattern typical of mucin. A second group of mAbs, MBECs 5 to 8, reacted strongly along the biliary tract and by immunoblot analysis, reacted with several bands ranging from 44 kd to 64 kd. These antibodies were considered as markers of pan BECs and their staining pattern proved similar to that of a control polyclonal pan-cytokeratin. The final group of mAbs, MBECs 9 to 12, recognized a 36-kd antigen using lysates of murine BECs. These antibodies also predominantly stained small peripheral bile ducts. The reactive antigen was purified by immunoprecipitation and microsequenced; the peptides sequenced showed 100% homology with murine annexin V. The identification of annexin V with predominantly intrahepatic bile ducts, is of significant interest because of the multiple roles of annexin V, including that of membrane cytoskeletal interactions during transport and apoptosis.