Hyperproliferation of bile duct epithelial cells due to cell-cycle dysregulation is a key feature of cystogenesis in polycystic liver diseases (PCLDs). Recent evidence suggests a regulatory role for microRNAs (miRNAs) in a variety of biological processes, including cell proliferation. We therefore hypothesized that miRNAs may be involved in the regulation of selected components of the cell cycle and might contribute to hepatic cystogenesis. We found that the cholangiocyte cell line PCK-CCL, which is derived from the PCK rat, a model of autosomal recessive polycystic kidney disease (ARPKD), displayed global changes in miRNA expression compared with normal rat cholangiocytes (NRCs). More specific analysis revealed decreased levels of 1 miRNA, miR15a, both in PCK-CCL cells and in liver tissue from PCK rats and patients with a PCLD. The decrease in miR15a expression was associated with upregulation of its target, the cell-cycle regulator cell division cycle 25A (Cdc25A). Overexpression of miR15a in PCK-CCL cells decreased Cdc25A levels, inhibited cell proliferation, and reduced cyst growth. In contrast, suppression of miR15a in NRCs accelerated cell proliferation, increased Cdc25A expression, and promoted cyst growth. Taken together, these results suggest that suppression of miR15a contributes to hepatic cystogenesis through dysregulation of Cdc25A.

Masyuk AI, Gradilone SA, Banales JM, Huang BQ, Masyuk TV, Lee S-O, Splinter PL, Stroope AJ, LaRusso NF. Cholangiocyte primary cilia are chemosensory organelles that detect biliary nucleotides via P2Y 12 purinergic receptors. Am J Physiol Gastrointest Liver Physiol 295: G725-G734, 2008. First published August 7, 2008 doi:10.1152/ajpgi.90265.2008.-Cholangiocytes, the epithelial cells lining intrahepatic bile ducts, contain primary cilia, which are mechano-and osmosensory organelles detecting changes in bile flow and osmolality and transducing them into intracellular signals. Here, we asked whether cholangiocyte cilia are chemosensory organelles by testing the expression of P2Y purinergic receptors and components of the cAMP signaling cascade in cilia and their involvement in nucleotide-induced cAMP signaling in the cells. We found that P2Y 12 purinergic receptor, adenylyl cyclases (i.e., AC4, AC6, and AC8), and protein kinase A (i.e., PKA RI-␤ and PKA RII-␣ regulatory subunits), exchange protein directly activated by cAMP (EPAC) isoform 2, and A-kinase anchoring proteins (i.e., AKAP150) are expressed in cholangiocyte cilia. ADP, an endogenous agonist of P2Y 12 receptors, perfused through the lumen of isolated rat intrahepatic bile ducts or applied to the ciliated apical surface of normal rat cholangiocytes (NRCs) in culture induced a 1.9-and 1.5-fold decrease of forskolininduced cAMP levels, respectively. In NRCs, the forskolin-induced cAMP increase was also lowered by 1.3-fold in response to ATP-␥S, a nonhydrolyzed analog of ATP but was not affected by UTP. The ADP-induced changes in cAMP levels in cholangiocytes were abolished by chloral hydrate (a reagent that removes cilia) and by P2Y 12 siRNAs, suggesting that cilia and ciliary P2Y12 are involved in nucleotide-induced cAMP signaling. In conclusion, cholangiocyte cilia are chemosensory organelles that detect biliary nucleotides through ciliary P2Y 12 receptors and transduce corresponding signals into a cAMP response. liver; ADP; adenylyl cyclases; cAMP; protein kinase A; exchange protein directly activated by cAMP; A-kinase anchoring protein 150 CHOLANGIOCYTES, the epithelial cells lining intrahepatic bile ducts (IBDs), contain primary cilia, nonmotile, solitary organelles extending from the apical plasma membrane into the ductal lumen (21,28,29). In many cell types, including cholangiocytes, primary cilia function as sensory organelles detecting multiple (i.e., mechano-, osmo-, chemo-) stimuli and transducing them into intracellular signaling (12,16,27,40,46). However, although increasing evidence suggests the ability of primary cilia to act as mechano-and osmosensors (16, 24, 28, 34 -37, 40 -42, 49, 50, 55), less data support their chemosensory functions. To function as chemosensory organelles, primary cilia should possess receptors and associated signaling cascades through which signals induced by specific ligands are transmitted into the cell. Such mechanism exists in Caenorhabditis elegans neuronal primary cilia, which express specific G protein-coupled...

Polyp size, endoscopist's experience, and right hemi-colon location were identified as potential risk factors for DPPB development.

Polycystic kidney (PCK) rats are a spontaneous model of autosomal recessive polycystic kidney disease that exhibit cholangiocyte-derived liver cysts. We have previously reported that in normal cholangiocytes a subset of vesicles contain three proteins (ie, the water channel AQP1, the chloride channel CFTR, and the anion exchanger AE2) that account for ion-driven water transport. Thus, we hypothesized that altered expression and location of these functionally related proteins contribute to hepatic cystogenesis. We show here that under basal conditions and in response to secretin and hypotonicity, cysts from PCK rats expanded to a greater degree than cysts formed by normal bile ducts. Quantitative reverse transcriptasepolymerase chain reaction, immunoblot analysis, and confocal and immunoelectron microscopy all indicated increased expression of these three proteins in PCK cholangiocytes versus normal cholangiocytes. AQP1, CFTR, and AE2 were localized preferentially to the apical membrane in normal rats while overexpressed at the basolateral membrane in PCK rats. Exposure of the cholangiocyte basolateral membrane to CFTR inhibitors ͓5-nitro-2-(3-phenylpropylamino)-benzoic acid and CFTRinh172͔, or Cl ؊ /HCO 3 ؊ exchange inhibitors (4,4-diisothiocyanatostilbene-2,2-disulfonic acid disodium salt hydrate and 4-acetamido-4-isothiocyanato-2,2-stilbenedisulfonic acid disodium salt hydrate) blocked secretin-stimulated fluid accumulation in PCK but not in normal cysts. Our data suggest that hepatic cystogenesis in autosomal recessive polycystic kidney disease may involve increased fluid accumulation because of overexpression and abnormal location of AQP1 , CFTR , and AE2 in cystic cholangiocytes. Therapeutic interventions that block the activation of these proteins might inhibit cyst expansion in polycystic liver disease. (Am J Pathol