Strazzabosco, Mario

Abstract The extracellular matrix is a highly reactive scaffold formed by a wide array of multifunctional molecules, encompassing collagens and noncollagenous glycoproteins, proteoglycans, glycosaminoglycans, and polysaccharides. Besides outlining the tissue borders, the extracellular matrix profoundly regulates the behavior of resident cells by transducing mechanical signals, and by integrating multiple cues derived from the microenvironment. Evidence is mounting that changes in the biostructure of the extracellular matrix are instrumental for biliary repair. Following biliary damage and eventually, malignant transformation, the extracellular matrix undergoes several quantitative and qualitative modifications, which direct interactions among hepatic progenitor cells, reactive ductular cells, activated myofibroblasts and macrophages, to generate the ductular reaction. Herein, we will give an overview of the main molecular factors contributing to extracellular matrix remodeling in cholangiopathies. Then, we will discuss the structural alterations in terms of biochemical composition and physical stiffness featuring the “desmoplastic matrix” of cholangiocarcinoma along with their pro-oncogenic effects.

Intrahepatic cholangiocarcinoma (iCCA) has over the last 10‐20 years become the focus of increasing concern, largely due to its rising incidence and high mortality rates worldwide. The significant increase in mortality rates from this primary hepatobiliary cancer, particularly over the past decade, has coincided with a rapidly growing interest among clinicians, investigators, and patient advocates to seek greater mechanistic insights and more effective biomarker‐driven targeted approaches for managing and/or preventing this challenging liver cancer. In addition to discussing challenges posed by this aggressive cancer, this review will emphasize recent epidemiological, basic, and translational research findings for iCCA. In particular, we will highlight emerging demographic changes and evolving risk factors, the critical role of the tumor microenvironment, extracellular vesicle biomarkers and therapeutics, intertumoral and intratumoral heterogeneity, and current and emerging targeted therapies regarding iCCA. Specifically, recent evidence linking non–bile duct medical conditions, such as nonalcoholic fatty liver disease and nonspecific cirrhosis, to intrahepatic cholangiocarcinogenesis together with geographic and ethnic variation will be assessed. Recent developments concerning the roles played by transforming growth factor‐β and platelet‐derived growth factor D in driving the recruitment and expansion of cancer‐associated myofibroblasts within cholangiocarcinoma (CCA) stroma as well as their therapeutic implications will also be discussed. In addition, the potential significance of extracellular vesicles as bile and serum biomarkers and therapeutic delivery systems for iCCA will be described. An integrated systems approach to classifying heterogeneous iCCA subtypes will be further highlighted, and recent clinical trials and emerging targeted therapies will be reviewed, along with recommendations for future translational research opportunities. Established international CCA networks are now facilitating collaborations aimed at advancing iCCA translational and clinical research.

Intrahepatic bile duct cells (cholangiocytes) play an important role in the secretion and alkalinization of bile. Both Na+/H+exchange (NHE) and Cl−/[Formula: see text]exchange (AE) contribute to these functions, but their functional distribution between the apical and basolateral membrane domains remains speculative. We have addressed this issue in a normal rat cholangiocyte cell line (NRC-1), which maintains a polarized distribution of membrane markers. Gene expression of AE and NHE isoforms was studied by RT-PCR. For functional studies, cells were placed in a chamber that allowed separate perfusion of the apical and basolateral aspect of the epithelial sheet; intracellular pH (pHi) was measured by 2′,7′-bis(2-carboxyethyl)-5(6)-carboxyfluorescein microfluorometry. In[Formula: see text]-CO2free medium and in the presence of apical amiloride, pHirecovery from an acid load was Na+dependent and was inhibited by basolateral amiloride and by HOE-642 (10 μM), consistent with basolateral localization of the NHE1 isoform, which had clearly expressed mRNA. Apical Na+readmission induced a slow pHirecovery that was inhibited by apical administration of 1 mM HOE-642 or amiloride. Among the apical NHE isoforms, NHE2 but not NHE3 gene expression was detected. The AE1 gene was not expressed, but two different variants of AE2 mRNAs (AE2a and AE2b) were detected; pHiexperiments disclosed AE activities at both sides of the membrane, but only apical AE was activated by cAMP. In conclusion, these studies provide the first functional description of acid-base transporters in a polarized cholangiocyte cell line. NHE1, NHE2, AE2a, and AE2b isoforms are expressed and show different membrane polarity, functional properties, and sensitivity to inhibitors. These observations add a considerable level of complexity to current models of electrolyte transport in cholangiocytes.

In the liver, the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) regulates bile secretion and other functions at the apical membrane of biliary epithelial cells (i.e., cholangiocytes). CF‐related liver disease is a major cause of death in patients with CF. CFTR dysfunction affects innate immune pathways, generating a para‐inflammatory status in the liver and other epithelia. This study investigates the mechanisms linking CFTR to toll‐like receptor 4 activity. We found that CFTR is associated with a multiprotein complex at the apical membrane of normal mouse cholangiocytes, with proteins that negatively control Rous sarcoma oncogene cellular homolog (Src) activity. In CFTR‐defective cholangiocytes, Src tyrosine kinase self‐activates and phosphorylates toll‐like receptor 4, resulting in activation of nuclear factor kappa‐light‐chain‐enhancer of activated B cells and increased proinflammatory cytokine production in response to endotoxins. This Src/nuclear factor kappa‐light‐chain‐enhancer of activated B cells‐dependent inflammatory process attracts inflammatory cells but also generates changes in the apical junctional complex and loss of epithelial barrier function. Inhibition of Src decreased the inflammatory response of CF cholangiocytes to lipopolysaccharide, rescued the junctional defect in vitro, and significantly attenuated endotoxin‐induced biliary damage and inflammation in vivo (Cftr knockout mice). Conclusion: These findings reveal a novel function of CFTR as a regulator of toll‐like receptor 4 responses and cell polarity in biliary epithelial cells; this mechanism is pathogenetic, as shown by the protective effects of Src inhibition in vivo, and may be a novel therapeutic target in CF‐related liver disease and other inflammatory cholangiopathies. (Hepatology 2016;64:2118‐2134).