Pancreatic enzymes in the epithelium of intrahepatic large bile ducts and in hepatic bile in patients with extrahepatic bile duct obstruction

Antimicrobial glycoprotein 2 (GP2) in gallstones, bile fluid and peribiliary glands of patients with primary sclerosing cholangitis

BACKGROUND

Glycoprotein-2 (GP2) IgA is a predictor of disease severity in primary sclerosing cholangitis (PSC). We examined GP2's occurrence in the biliary tract, the site of inflammation.

METHODS

GP2 was analyzed using ELISA, immunoblotting, mass spectrometry, and immunohistochemistry. The samples included: 20 bile and 30 serum samples from PSC patients, 23 bile and 11 serum samples from patients with gallstone disease (GD), 15 bile samples from healthy individuals undergoing liver-donation surgery (HILD), 20 extracts of gallstones (GE) obtained during cholecystectomy, and 101 blood-donor sera.

RESULTS

Biliary GP2 concentrations were significantly higher in patients with PSC and GD than in HILD (p < 0.0001). Serum GP2 levels were similar in PSC and GD patients, and controls, but lower than in bile (p < 0.0001). GP2 was detected in all 20 GEs. Mass spectrometry identified GP2 in the bile of 2 randomly selected GD and 2 PSC patients, and in none of 2 HILD samples. GP2 was found in peribiliary glands in 8 out of 12 PSC patients, showing morphological changes in acinar cells, but not in GD-gallbladders.

CONCLUSIONS

GP2 is present in bile of PSC and GD patients. It is synthesized in the peribiliary glands of PSC patients, supporting a pathogenic role for biliary GP2 in PSC.

Stem/Progenitor Cell Niches Involved in Hepatic and Biliary Regeneration

Niches containing stem/progenitor cells are present in different anatomical locations along the human biliary tree and within liver acini. The most primitive stem/progenitors, biliary tree stem/progenitor cells (BTSCs), reside within peribiliary glands located throughout large extrahepatic and intrahepatic bile ducts. BTSCs are multipotent and can differentiate towards hepatic and pancreatic cell fates. These niches' matrix chemistry and other characteristics are undefined. Canals of Hering (bile ductules) are found periportally and contain hepatic stem/progenitor cells (HpSCs), participating in the renewal of small intrahepatic bile ducts and being precursors to hepatocytes and cholangiocytes. The niches also contain precursors to hepatic stellate cells and endothelia, macrophages, and have a matrix chemistry rich in hyaluronans, minimally sulfated proteoglycans, fetal collagens, and laminin. The microenvironment furnishes key signals driving HpSC activation and differentiation. Newly discovered third niches are pericentral within hepatic acini, contain Axin2+ unipotent hepatocytic progenitors linked on their lateral borders to endothelia forming the central vein, and contribute to normal turnover of mature hepatocytes. Their relationship to the other stem/progenitors is undefined. Stem/progenitor niches have important implications in regenerative medicine for the liver and biliary tree and in pathogenic processes leading to diseases of these tissues.

Monitoring changes in plasma levels of pancreatic and intestinal enzymes in a model of pancreatic exocrine insufficiency--induced by pancreatic duct-ligation--in young pigs

PURPOSE

Plasma levels of pancreatic and intestinal enzymes were measured after pancreatic duct ligation (PDL) to monitor pancreatic exocrine insufficiency (PEI) in a model using young pigs.

MATERIAL/METHODS

Five, 6 week-old pigs (10.9±0.2kg), underwent PDL while age-matched, un-operated pigs were used as controls. Plasma levels of immunoreactive cationic trypsinogen (IRCT), amylase, lipase, and diamine oxidase (DAO) activities were analyzed for 48 days after PDL, including 1 week of oral pancreatic enzyme supplementation (PES) with Creon(®).

RESULTS

PDL resulted in an arrested body growth and a rapid surge of pancreatic enzymes (IRCT, amylase and lipase) into the plasma. Nine days after PDL, the plasma levels of these pancreatic enzymes had decreased. IRCT then remained below the level in un-operated pigs while amylase only fell below control at 25 days. The intestinally derived marker DAO and plasma protein levels were unaffected by PDL but DAO decreased slightly with time in PEI pigs. One-week of oral PES restored body growth, but had little effect on pancreatic enzyme plasma levels, except for a tendency towards increased DAO.

CONCLUSIONS

The study showed that PEI developed within 1-2 weeks after PDL and that only IRCT is a reliable plasma enzyme marker for this. The reduced plasma DAO indicated that PEI also affected the intestines, while PES therapy restored growth of the PDL pigs and slightly increased plasma DAO, suggesting an improved intestinal function.

Physiology of cholangiocytes

Cholangiocytes are epithelial cells that line the intra- and extrahepatic ducts of the biliary tree. The main physiologic function of cholangiocytes is modification of hepatocyte-derived bile, an intricate process regulated by hormones, peptides, nucleotides, neurotransmitters, and other molecules through intracellular signaling pathways and cascades. The mechanisms and regulation of bile modification are reviewed herein.

Recent advances in the morphological and functional heterogeneity of the biliary epithelium

This review focuses on the recent advances related to the heterogeneity of different-sized bile ducts with regard to the morphological and phenotypical characteristics, and the differential secretory, apoptotic and proliferative responses of small and large cholangiocytes to gastrointestinal hormones/peptides, neuropeptides and toxins. We describe several in vivo and in vitro models used for evaluating biliary heterogeneity. Subsequently, we discuss the heterogeneous proliferative and apoptotic responses of small and large cholangiocytes to liver injury and the mechanisms regulating the differentiation of small into large (more differentiated) cholangiocytes. Following a discussion on the heterogeneity of stem/progenitor cells in the biliary epithelium, we outline the heterogeneity of bile ducts in human cholangiopathies. After a summary section, we discuss the future perspectives that will further advance the field of the functional heterogeneity of the biliary epithelium.

Malignant intraductal oncocytic papillary neoplasm of the common bile duct

Recently, several cases of intraductal oncocytic papillary neoplasm (IOPN) of the liver and hepatic bile ducts have been reported. The author herein reports the first case of IOPN of the common bile duct (CBD). A 78-year-old man was admitted to our hospital because of jaundice. Imaging modalities including US, CT, MRI revealed an intraductal tumor of the middle CBD and biliary dilation distal to the tumor. A partial resection of the CBD was performed. Grossly, a papillary tumor measuring 20 × 15 mm was found within the CBD. Mucus is absent. Histologically, the papillary tumor was composed of atypical oncocytes. The atypia was enough to be diagnosed as adenocarcinoma. No invasive features were noted. Immunohistochemically, the tumor cells were positive for pancytokeratins (CK), CK 7, CK 18, CK19, EMA, CA19-9, CEA, mitochondria, p53 protein, C-erbB2, Ki-67 (labeling = 80%), MUC2, MUC5AC and MUC-6,. The tumor cells were negative for CK8, CK20, chromogranin, synaptophysin, neuron-specific enolase, S100 protein, CD56, MUC1, CD10 and CDX2. These immunohistochemical findings were compatible with IOPN. The patient died of other non-tumorous disease 7 year after the operation. In summary, the author presented the first case of IOPN of the CBD.

Biliary tree stem/progenitor cells in glands of extrahepatic and intraheptic bile ducts: an anatomical in situ study yielding evidence of maturational lineages

Stem/progenitors have been identified intrahepatically in the canals of Hering and extrahepatically in glands of the biliary tree. Glands of the biliary tree (peribiliary glands) are tubulo-alveolar glands with mucinous and serous acini, located deep within intrahepatic and extrahepatic bile ducts. We have shown that biliary tree stem/progenitors (BTSCs) are multipotent, giving rise in vitro and in vivo to hepatocytes, cholangiocytes or pancreatic islets. Cells with the phenotype of BTSCs are located at the bottom of the peribiliary glands near the fibromuscular layer. They are phenotypically heterogeneous, expressing transcription factors as well as surface and cytoplasmic markers for stem/progenitors of liver (e.g. SOX9/17), pancreas (e.g. PDX1) and endoderm (e.g. SOX17, EpCAM, NCAM, CXCR4, Lgr5, OCT4) but not for mature markers (e.g. albumin, secretin receptor or insulin). Subpopulations co-expressing liver and pancreatic markers (e.g. PDX1(+)/SOX17(+)) are EpCAM(+/-), and are assumed to be the most primitive of the BTSC subpopulations. Their descendants undergo a maturational lineage process from the interior to the surface of ducts and vary in the mature cells generated: pancreatic cells in hepatopancreatic ducts, liver cells in large intrahepatic bile ducts, and bile duct cells along most of the biliary tree. We hypothesize that there is ongoing organogenesis throughout life, with BTSCs giving rise to hepatic stem cells in the canals of Hering and to committed progenitors within the pancreas. The BTSCs are likely to be central to normal tissue turnover and injury repair and to be key elements in the pathophysiology of liver, pancreas and biliary tree diseases, including oncogenesis.

Heterogeneity of the intrahepatic biliary epithelium

The objectives of this review are to outline the recent findings related to the morphological heterogeneity of the biliary epithelium and the heterogeneous pathophysiological responses of different sized bile ducts to liver gastrointestinal hormones and peptides and liver injury/toxins with changes in apoptotic, proliferative and secretory activities. The knowledge of biliary function is rapidly increasing because of the recognition that biliary epithelial cells (cholangiocytes) are the targets of human cholangiopathies, which are characterized by proliferation/damage of bile ducts within a small range of sizes. The unique anatomy, morphology, innervation and vascularization of the biliary epithelium are consistent with function of cholangiocytes within different regions of the biliary tree. The in vivo models [e.g., bile duct ligation (BDL), partial hepatectomy, feeding of bile acids, carbon tetrachloride (CCl₄) or α-naphthylisothiocyanate (ANIT)] and the in vivo experimental tools [e.g., freshly isolated small and large cholangiocytes or intrahepatic bile duct units (IBDU) and primary cultures of small and large murine cholangiocytes] have allowed us to demonstrate the morphological and functional heterogeneity of the intrahepatic biliary epithelium. These models demonstrated the differential secretory activities and the heterogeneous apoptotic and proliferative responses of different sized ducts. Similar to animal models of cholangiocyte proliferation/injury restricted to specific sized ducts, in human liver diseases bile duct damage predominates specific sized bile ducts. Future studies related to the functional heterogeneity of the intrahepatic biliary epithelium may disclose new pathophysiological treatments for patients with cholangiopathies.

The enzyme levels in blood are not affected by oral administration of a pancreatic enzyme preparation (Creon 10,000) in pancreas-insufficient pigs

After oral intake, small amounts of intact protein may be absorbed into the blood circulation. The current study investigated whether orally administered pancreatic enzymes were absorbed from the intestine. The study included 28 pigs; 3 control pigs with intact pancreatic function and 25 pigs that were made exocrine pancreas insufficient by duct ligation (20 pigs) or total pancreatectomy (5 pigs). The pigs received a pancreatic enzyme preparation (0, 2, 4, or 8 g of Creon 10,000) together with the feed. The blood plasma was analyzed for pancreatic lipase activity with a [3H]-triolein substrate assay, while (pro)colipase and cationic trypsin(ogen) levels were measured with enzyme-linked immunosorbent assay (ELISA). Administration of Creon (0-8 g) caused no significant changes in plasma (pro)colipase or cationic trypsin(ogen) levels. Lipase activity peaks in plasma samples were found, but they did not correspond to the administration of Creon. The potential source of these plasma lipase activity peaks is discussed. The results showed no absorption into blood of pancreatic enzymes after oral administration (0, 2, 4, or 8 g of Creon mixed with 100 g of feed) to pancreas-insufficient pigs.

Expression of pancreatic alpha-amylase protein and messenger RNA in hilar primitive bile ducts and hepatocytes during human fetal liver organogenesis: an immunohistochemical and in situ hybridization study

AIMS/BACKGROUND

This study was conducted to evaluate the expression of pancreatic digestive enzymes in hilar bile ducts and hepatocytes during human fetal liver organogenesis.

METHODS

We investigated the expression of pancreatic alpha-amylase protein and messenger RNA (mRNA) in hilar primitive bile ducts and hepatocytes by immunohistochemistry and in situ hybridization techniques, using 11 human fetal livers of various gestational ages. The specificity of the immunohistochemistry and in situ hybridization procedures was confirmed by Western blot analysis and in situ hybridization using sense probes, respectively.

RESULTS

Immunoreactivity of pancreatic alpha-amylase protein and expression of pancreatic alpha-amylase mRNA were present not only in the primitive ductal cells of the hilar region including the ductal plate, remodelling bile ducts and remodeled bile ducts but also in primitive hepatocytes of the hilar region, though the immunoreactivity and mRNA signals in the primitive hepatocytes disappeared in the third trimester. There was perfect correlation between immunohistochemistry and in situ hybridization.

CONCLUSIONS

These results suggest that primitive biliary cells and hepatocytes of the hilar region in the human fetus do express pancreatic alpha-amylase protein and mRNA, and that the primitive biliary epithelial cells and hepatocytes in the hilar region share a common cell lineage with exocrine pancreatic cells.

Normal and abnormal development of the human intrahepatic biliary system: a review

Morphology and immunohistochemical features of the developmental process of the human intrahepatic biliary system (IBS) are reviewed. Human IBS arises from the ductal plate, a double-layered cylindrical structure located at the interface between portal mesenchyme and primitive hepatocytes. The ductal plate first appears from primitive hepatocytes (hepatoblasts) around 8 gestational weeks (GW), and its formation proceeds from the hepatic hilum to the periphery. The ductal plate gradually undergoes remodeling from 12 GW; some parts of the ductal plate disappear and other parts migrate into the portal mesenchyme. Around 20 GW, the migrated duct cells transform into immature bile ducts and peribiliary glands. Some immature peribiliary glands transform into pancreatic acinar cells around postnatal 3 months. The immature biliary elements express cytokeratins no. 7, 8, 18 and 19. Several growth factors (TGF-alpha, HGF) and their receptors (EGFR, MET, ERBB2) were expressed in the primitive IBS cells. Some extracellular matrix proteins including type IV collagen, laminin and tenascin are expressed in the mesenchyme around the primitive IBS. During IBS remodeling, apoptosis and cell proliferation occur with appropriate expression of apoptosis-related proteins (bcl-2, Fas, c-myc, Lewis(y)). Some pancreatic digestive enzymes (alpha-amylase, trypsinogen, lipase), cathepsin B, and matrix metalloproteinases (MMP-1, 2, 3, 9) and their inhibitors (TIMP-1, 2) are expressed in the remodeling IBS cells. Glycoconjugate residues of glycoproteins gradually appear during IBS development. The appropriate expression of these immunophenotypes may play an important role in the normal development of IBS.

Expression of matrix proteinases during human intrahepatic bile duct development. A possible role in biliary cell migration

Primitive biliary cells are known to migrate from the ductal plate into the mesenchyme during human intrahepatic bile duct development, and this migration process is essential for normal development of intrahepatic bile ducts. However, its molecular mechanism is unknown. Matrix proteinases play an important role in cell migration during cancer invasion and organ development. In this study, we therefore investigated in situ expression of matrix metalloproteinases (MMP) and tissue inhibitors of MMP (TIMP) during human intrahepatic bile duct development, using 32 human fetal livers. We also examined in situ expression of trypsinogen/trypsin, chymotrypsinogen/chymotrypsin, and cathepsin B, which are matrix proteinases and activators of MMP. MMP-1 expression was noted in the ductal plate and migrating primitive biliary cells. MMP-2, MMP-3, and MMP-9 were expressed in the ductal plate. TIMP-1 and TIMP-2 were expressed in the ductal plate and migrating primitive biliary cells. Trypsinogen/trypsin, chymotrypsinogen/chymotrypsin, and cathepsin B were also expressed in primitive biliary cells. These data suggest that MMP, trypsinogen/trypsin, chymotrypsinogen/chymotrypsin, and cathepsin B play a critical role in biliary cell migration during human intrahepatic bile duct development by degrading extracellular matrix proteins. The data also suggest that MMP inhibitors (TIMP-1 and TIMP-2) and MMP activators (trypsin, chymotrypsin, and cathepsin B) play an important role in biliary cell migration. The coordinated expression of MMP, MMP inhibitors, and MMP activators may be necessary for the normal development of human intrahepatic bile ducts.

Expression of pancreatic enzymes (alpha-amylase, trypsinogen, and lipase) during human liver development and maturation

BACKGROUND/AIMS

Although pancreatic enzymes have been found in hilar intrahepatic bile ducts in adult humans, their expression during human liver development is unclear. The aim of this study was to clarify the temporal expression of pancreatic enzymes at various stages of human liver development.

METHODS

We immunohistochemically investigated pancreatic alpha-amylase, trypsinogen, and lipase expression in fetal, neonatal, juvenile, and adult human livers.

RESULTS

In hilar duct development, alpha-amylase but not trypsinogen or lipase was expressed in the ductal plate. These three enzymes were expressed in biliary cells migrating into the mesenchyma, in immature ducts in fetal livers, and in maturing and mature ducts in postnatal livers. Their expression was weak and diffusely cytoplasmic in fetal livers, whereas in postnatal livers their expression was strong, granular, and located in the supranuclear cytoplasm. Expression was not found in developing peripheral ducts. These enzymes were expressed in immature hepatocytes (9-25 weeks' gestation) but disappeared thereafter. Enzyme expression was mild in fetal pancreata and strong in adult pancreata.

CONCLUSIONS

Pancreatic enzymes may be present in primitive hilar bile ducts and hepatocytes in fetal livers; hilar ducts, hepatocytes, and pancreas may have similar fetal enzymatic profiles. Intrahepatic hilar bile ducts, hepatocytes, and exocrine pancreas may have a common cell lineage.