Luca Fabris

Genome-wide meta-analyses identify three loci associated with primary biliary cirrhosis

A genome-wide association screen for primary biliary cirrhosis risk alleles was performed in an Italian cohort. The results from the Italian cohort replicated IL12A and IL12RB associations, and a combined meta-analysis using a Canadian dataset identified newly associated loci at SPIB (P = 7.9 × 10−11, odds ratio (OR) = 1.46), IRF5-TNPO3 (P = 2.8 × 10−10, OR = 1.63) and 17q12-21 (P = 1.7 × 10−10, OR = 1.38).

Effects of angiogenic factor overexpression by human and rodent cholangiocytes in polycystic liver diseases.

Liver involvement in autosomal dominant polycystic kidney disease (ADPKD) is characterized by altered remodeling of the embryonic ductal plate (DP) with presence of biliary cysts and aberrant portal vasculature. The genetic defect causing ADPKD has been identified, but mechanisms of liver cyst growth remain uncertain. To investigate the possible role of angiogenic mechanisms, we have studied the immunohistochemical expression of vascular endothelial growth factor (VEGF), angiopoietin–1 (Ang‐1), angiopoietin‐2 (Ang‐2) and their receptors (VEGFR‐1, VEGFR‐2, Tie‐2) in ADPKD, Carolis disease, normal and fetal livers. In ADPKD and control livers Ang‐1 and Ang‐2 gene expression was studied by real‐time‐PCR. Effects of VEGF on cholangiocyte proliferation were studied by PCNA Western Blot in isolated rat cholangiocytes and by MTS assay in cultured cholangiocytes isolated from ADPKD patients and from an ADPKD mouse model (Pkd2WS25/−). Cholangiocytes were strongly positive for VEGF, VEGFR‐1, VEGFR‐2 and Ang‐2 in ADPKD and Caroli, and also for Ang‐1 and Tie‐2 in ADPKD, similar to fetal ductal plate cells. VEGF stimulated proliferation in both normal and ADPKD cholangiocytes, but the effect was particularly evident in the latter. Ang‐1 alone had no effect, but was synergic to VEGF. VEGF expression on cholangiocytes positively correlated with microvascular density. In conclusion, consistent with the immature phenotype of the cystic epithelium, expression of VEGF, VEGFRs, Ang‐1 and Tie‐2 is strongly upregulated in cholangiocytes from polycystic liver diseases. VEGF and Ang‐1 have autocrine proliferative effect on cholangiocyte growth and paracrine effect on portal vasculature, thus promoting the growth of the cysts and their vascular supply. (HEPATOLOGY 2006;43:1001–1012.)

Changing trends in acute upper-GI bleeding: a population-based study.

BACKGROUND Advances in medical practice in recent decades have influenced the etiology and management of acute upper-GI bleeding (UGIB), but their impact on the incidence and mortality is unclear. OBJECTIVE To analyze the time trends of UGIB in 2 different management eras. DESIGN Prospective observational study. SETTING General university-affiliated hospital. PATIENTS AND INTERVENTIONS A total of 587 patients who presented with UGIB during the 1983-to-1985 period were compared with 539 patient in the 2002-to-2004 period. RESULTS The overall incidence of UGIB decreased from 112.5 to 89.8 per 100,000/y, which corresponds to a 35.5% decrease after adjustment for age (95% CI, 24.2%-46.8%). The age standardized incidence of ulcer bleeding decreased by 41.6% (95% CI, 27.2%-56%); the decrease occurred only in people younger than 70 years of age. The rate of history of peptic ulcer disease decreased from 32.7% in the 1983-to-1985 period versus 19.5% in the 2002-to-2004 period (P < .001). The mean age increased from 61.0 to 68.7 years (P < .001), and the male:female ratio decreased from 2.7 to 1.8 (P = .002). The comorbidities increased from 69% to 75% (P = .01), the use of nonsteroidal anti-inflammatory drugs from 40.0% to 46.4% (P = .03), and the cases of bleeding occurring during hospitalization from 10.4% to 17.1% (P < .001). In the 1983-to-1985 cohort, the endoscopy was solely diagnostic, and antisecretory therapy consisted of H2-antagonists drugs. In the second period, 39.3% of patients underwent endoscopic therapy, whereas proton pump inhibitors were administered in 47%. Rebleeding rates decreased from 32.5% to 7.4% (P < .001) and surgery from 10.2% to 2.0% (P < .001). Overall mortality decreased from 17.1 to 8.2 per 100,000/y, which corresponded to a 60.8% decrease after adjustment for age (95% CI, 46.5%-75.1%). The age standardized mortality rate for ulcer bleeding decreased by 56.5% (95% CI, 41.9%-71.1%). LIMITATIONS A single-center study and a potential lack of generalizability. CONCLUSIONS From the 1983-to-1985 period to the 2002-to-2004 period, major changes occurred in the incidence of UGIB, features of patients, management, and outcomes. The incidence and mortality of UGIB overall and ulcer bleeding decreased significantly, and the decline of incidence occurred only in patients younger than 70 years old.

Characterization and Isolation of Ductular Cells Coexpressing Neural Cell Adhesion Molecule and Bcl-2 from Primary Cholangiopathies and Ductal Plate Malformations

It has recently been shown that reactive bile ductules display neuroendocrine features, including immunoreactivity for the neural cell adhesion molecule (NCAM). In this study we have compared the immunohistochemical expression of NCAM with that of HEA-125 (biliary specific) and LKM-1 (hepatocyte specific) and other markers relevant to morphogenesis (Bcl-2, EMA) and cell proliferation (Ki-67) in cryostat sections from different chronic liver diseases and from fetal livers at different gestational ages. In parallel, viable NCAM-positive ductular cells were purified from collagenase digests of cirrhotic livers by immunomagnetic separation and characterized by immunocytochemistry and transmission electron microscopy. We demonstrated that reactive ductules with atypical morphology coexpressed NCAM and Bcl-2 and were found mainly in congenital diseases associated with ductal plate malformation and in primary cholangiopathies. On the contrary, reactive ductules with typical morphology were negative for NCAM/Bcl-2 and positive for EMA. Reactive ductules coexpressing NCAM/Bcl-2 were negative for the proliferation marker Ki-67 and appeared to be directly connected with periportal hepatocytes. In fetal livers NCAM/Bcl-2 was transiently expressed during the early developmental stages of ductal plate (10-16 weeks) and started to disappear as the ductal plate began duplicating. NCAM-positive ductal plate cells were Ki-67 negative, becoming positive in duplicated segments. Thus the histogenesis of ductular reactive cells seems to recapitulate the early stages of biliary ontogenesis. In primary cholangiopathies and ductal plate malformations, these cells do not appear to maturate further, and thus abundant ductular structures coexist with vanishing mature ducts. These NCAM-positive ductular cells were immunopurified from patients with chronic cholestatic liver diseases and showed ultrastructural features consistent with a less differentiated phenotype than mature cholangiocytes. These isolated cells represent a useful model for in vitro studies.

Human leukocyte antigen polymorphisms in Italian primary biliary cirrhosis: a multicenter study of 664 patients and 1992 healthy controls

Genetic factors are critical in determining susceptibility to primary biliary cirrhosis (PBC), but there has not been a clear association with human leukocyte antigen (HLA) genes. We performed a multicenter case‐control study and analyzed HLA class II DRB1 associations using a large cohort of 664 well‐defined cases of PBC and 1992 controls of Italian ancestry. Importantly, healthy controls were rigorously matched not only by age and sex, but also for the geographical origin of the proband four grandparents (Northern, Central, and Southern Italy). After correction for multiple testing, DRB1*08 [odds ratio (OR), 3.3; 95% confidence interval (CI), 2.4‐4.5] and DRB1*02 (OR 0.9; 95% CI 0.8‐1.2) were significantly associated with PBC, whereas alleles DRB1*11 (OR 0.4; 95% CI 0.3‐0.4) and DRB1*13 (OR 0.7; 95% CI 0.6‐0.9) were protective. When subjects were stratified according to their grandparental geographical origin, only the associations with DRB1*08 and DRB1*11 were common to all three areas. Associated DRB1 alleles were found only in a minority of patients, whereas an additive genetic model is supported by the gene dosage effect for DRB1*11 allele and the interaction of DRB1*11,*13, and *08. Lastly, no significant associations were detected between specific DRB1 alleles and relevant clinical features represented by the presence of cirrhosis or serum autoantibodies. In conclusion, we confirm the role for HLA to determine PBC susceptibility and suggest that the effect of HLA is limited to patient subgroups. We suggest that a large whole‐genome approach is required to identify further genetic elements contributing to the loss of tolerance in this disease. (HEPATOLOGY 2008;48:1906‐1912.)

Development of the bile ducts: Essentials for the clinical hepatologist

Several cholangiopathies result from a perturbation of developmental processes. Most of these cholangiopathies are characterised by the persistence of biliary structures with foetal configuration. Developmental processes are also relevant in acquired liver diseases, as liver repair mechanisms exploit a range of autocrine and paracrine signals transiently expressed in embryonic life. We briefly review the ontogenesis of the intra- and extrahepatic biliary tree, highlighting the morphogens, growth factors, and transcription factors that regulate biliary development, and the relationships between developing bile ducts and other branching biliary structures. Then, we discuss the ontogenetic mechanisms involved in liver repair, and how these mechanisms are recapitulated in ductular reaction, a common reparative response to many forms of biliary and hepatocellular damage. Finally, we discuss the pathogenic aspects of the most important primary cholangiopathies related to altered biliary development, i.e. polycystic and fibropolycystic liver diseases, Alagille syndrome.

Functional Anatomy of Normal Bile Ducts

The biliary tree is a complex network of conduits that begins with the canals of Hering and progressively merges into a system of interlobular, septal, and major ducts which then coalesce to form the extrahepatic bile ducts, which finally deliver bile to the gallbladder and to the intestine. The biliary epithelium shows a morphological heterogeneity that is strictly associated with a variety of functions performed at the different levels of the biliary tree. In addition to funneling bile into the intestine, cholangiocytes (the epithelial cells lining the bile ducts) are actively involved in bile production by performing both absorbitive and secretory functions. More recently, other important biological properties restricted to cholangiocytes lining the smaller bile ducts have been outlined, with regard to their plasticity (i.e., the ability to undergo limited phenotypic changes), reactivity (i.e., the ability to participate in the inflammatory reaction to liver damage), and ability to behave as liver progenitor cells. Functional interactions with other branching systems, such as nerve and vascular structures, are crucial in the modulation of the different cholangiocyte functions. Anat Rec, 291:653–660, 2008.

ERK1/2-Dependent Vascular Endothelial Growth Factor Signaling Sustains Cyst Growth in Polycystin-2 Defective Mice

BACKGROUND & AIMS Severe polycystic liver disease can complicate adult dominant polycystic kidney disease, a genetic disease caused by defects in polycystin-1 (Pkd1) or polycystin-2 (Pkd2). Liver cyst epithelial cells (LCECs) express vascular endothelial growth factor (VEGF) and its receptor, VEGFR-2. We investigated the effects of VEGF on liver cyst growth and autocrine VEGF signaling in mice with Pkd1 and Pkd2 conditional knockouts. METHODS We studied mice in which Pkd1 or Pkd2 were conditionally inactivated following exposure to tamoxifen; these mice were called Pkd1(flox/-):pCxCreER (Pkd1KO) and Pkd2(flox/-):pCxCreER (Pkd2KO). RESULTS Pkd1KO and Pkd2KO mice developed liver defects; their LCECs expressed VEGF, VEGFR-2, hypoxia-inducible factor (HIF)-1alpha, phosphorylated extracellular signal-regulated kinase 1/2 (pERK1/2), and proliferating cell nuclear antigen (PCNA). In Pkd2KO but not Pkd1KO mice, exposure to the VEGFR-2 inhibitor SU5416 significantly reduced liver cyst development, liver/body weight ratio, and expression of pERK and PCNA. VEGF secretion and phosphorylation of ERK1/2 and VEGFR-2 were significantly increased in cultured LCECs from Pkd2KO compared with Pkd1KO mice. Inhibition of protein kinase A (PKA) reduced VEGF secretion and pERK1/2 expression. Addition of VEGF to LCECs from Pkd2KO mice increased phosphorylated VEGFR-2 and phosphorylated mitogen signal-regulated kinase (MEK) expression and induced phosphorylation of ERK1/2; this was inhibited by SU5416. Expression of HIF-1alpha increased in parallel with secretion of VEGF following LCEC stimulation. VEGF-induced cell proliferation was inhibited by the MEK inhibitor U1026 and by ERK1/2 small interfering RNA. CONCLUSIONS The PKA-ERK1/2-VEGF signaling pathway promotes growth of liver cysts in mice. In Pkd2-defective LCECs, PKA-dependent ERK1/2 signaling controls HIF-1alpha-dependent VEGF secretion and VEGFR-2 signaling. Autocrine and paracrine VEGF signaling promotes the growth of liver cysts in Pkd2KO mice. VEGF inhibitors might be used to treat patients with polycystic liver disease.

Loss of CFTR Affects Biliary Epithelium Innate Immunity and Causes TLR4–NF-κB—Mediated Inflammatory Response in Mice

BACKGROUND & AIMS Loss of function of the cystic fibrosis transmembrane conductance regulator (CFTR) in the biliary epithelium reduces bile flow and alkalinization in patients with cystic fibrosis (CF). Liver damage is believed to result from ductal cholestasis, but only 30% of patients with CF develop liver defects, indicating that another factor is involved. We studied the effects of CFTR deficiency on Toll-like receptor 4 (TLR4)-mediated responses of the biliary epithelium to endotoxins. METHODS Dextran sodium sulfate (DSS) was used to induce colitis in C57BL/6J-Cftrtm1Unc (Cftr-KO) mice and their wild-type littermates. Ductular reaction and portal inflammation were quantified by keratin-19 and CD45 immunolabeling. Cholangiocytes isolated from wild-type and Cftr-KO mice were challenged with lipopolysaccharide (LPS); cytokine secretion was quantified. Activation of nuclear factor κB (NF-κB), phosphorylation of TLR4, and activity of Src were determined. HEK-293 that expressed the secreted alkaline phosphatase reporter and human TLR4 were transfected with CFTR complementary DNAs. RESULTS DSS-induced colitis caused biliary damage and portal inflammation only in Cftr-KO mice. Biliary damage and inflammation were not attenuated by restoring biliary secretion with 24-nor-ursodeoxycholic acid but were significantly reduced by oral neomycin and polymyxin B, indicating a pathogenetic role of gut-derived bacterial products. Cftr-KO cholangiocytes incubated with LPS secreted significantly higher levels of cytokines regulated by TLR4 and NF-κB. LPS-mediated activation of NF-κB was blocked by the TLR4 inhibitor TAK-242. TLR4 phosphorylation by Src was significantly increased in Cftr-KO cholangiocytes. Expression of wild-type CFTR in the HEK293 cells stimulated with LPS reduced activation of NF-κB. CONCLUSIONS CFTR deficiency alters the innate immunity of the biliary epithelium and reduces its tolerance to endotoxin, resulting in an Src-dependent inflammatory response mediated by TLR4 and NF-κB. These findings might be used to develop therapies for CF-associated cholangiopathy.

Mammalian target of rapamycin regulates vascular endothelial growth factor-dependent liver cyst growth in polycystin-2-defective mice.

Polycystic liver disease may complicate autosomal dominant polycystic kidney disease (ADPKD), a disease caused by mutations in polycystins, which are proteins that regulate signaling, morphogenesis, and differentiation in epithelial cells. The cystic biliary epithelium [liver cystic epithelium (LCE)] secretes vascular endothelial growth factor (VEGF), which promotes liver cyst growth via autocrine and paracrine mechanisms. The expression of insulin‐like growth factor 1 (IGF1), insulin‐like growth factor 1 receptor (IGF1R), and phosphorylated mammalian target of rapamycin (p‐mTOR) and the protein kinase A (PKA)–dependent phosphorylation of extracellular signal‐regulated kinase 1/2 (ERK1/2) are also up‐regulated in LCE. We have hypothesized that mammalian target of rapamycin (mTOR) represents a common pathway for the regulation of hypoxia‐inducible factor 1 alpha (HIF1α)–dependent VEGF secretion by IGF1 and ERK1/2. Conditional polycystin‐2–knockout (Pkd2KO) mice were used for in vivo studies and to isolate cystic cholangiocytes [liver cystic epithelial cells (LCECs)]. The expression of p‐mTOR, VEGF, cleaved caspase 3 (CC3), proliferating cell nuclear antigen (PCNA), IGF1, IGF1R, phosphorylated extracellular signal‐regulated kinase, p‐P70S6K, HIF1α, and VEGF in LCE, LCECs, and wild‐type cholangiocytes was studied with immunohistochemistry, western blotting, or enzyme‐linked immunosorbent assays. The cystic area was measured by computer‐assisted morphometry of pancytokeratin‐stained sections. Cell proliferation in vitro was studied with 3‐(4,5‐dimethylthiazol‐2‐yl)‐5‐(3‐carboxymethoxyphenyl)‐2‐(4‐sulfophenyl)‐2H‐tetrazolium and bromodeoxyuridine assays. The treatment of Pkd2KO mice with the mTOR inhibitor rapamycin significantly reduced the liver cyst area, liver/body weight ratio, pericystic microvascular density, and PCNA expression while increasing expression of CC3. Rapamycin inhibited IGF1‐stimulated HIF1α accumulation and VEGF secretion in LCECs. IGF1‐stimulated LCEC proliferation was inhibited by rapamycin and SU5416 (a vascular endothelial growth factor receptor 2 inhibitor). Phosphorylation of the mTOR‐dependent kinase P70S6K was significantly reduced by PKA inhibitor 14‐22 amide and by the mitogen signal‐regulated kinase inhibitor U1026. Conclusion: These data demonstrate that PKA‐dependent up‐regulation of mTOR has a central role in the proliferative, antiapoptotic, and pro‐angiogenic effects of IGF1 and VEGF in polycystin‐2–defective mice. This study also highlights a mechanistic link between PKA, ERK, mTOR, and HIF1α‐mediated VEGF secretion and provides a proof of concept for the potential use of mTOR inhibitors in ADPKD and conditions with aberrant cholangiocyte proliferation. (HEPATOLOGY 2010.)