We have produced continuous cell lines using retroviral transduction of SV40 large T antigen into human intrahepatic biliary epithelial (IBE) cells from three different normal individuals. These IBE cell lines grow in a hormone-supplemented medium in the presence of NIH/3T3 fibroblast coculture. These cells maintain their epithelial appearance and are positive for the biliary-specific markers cytokeratins 7 and 19 and gamma-glutamyl transpeptidase while being negative for the hepatocyte markers albumin and asialoglycoprotein receptor. To evaluate ion transport pathways in IBE cell lines, we utilized intracellular pH (pHi) measurements obtained using the intracellular fluorescent indicator 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein. In the absence of HCO3(-)-CO2, an amiloride-sensitive Na(+)-H+ exchanger participated in the regulation of basal pHi. In the presence of HCO3(-)-CO2, a 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-sensitive, Na-, Cl-, and HCO3(-)-dependent acid extrusion mechanism accounted for approximately 60% of pHi recovery from acidic pHi; this mechanism is most consistent with the presence of a Na-dependent Cl-HCO3- exchanger (Na+HCO3(-)-Cl-H+). Under basal conditions, Cl- depletion revealed a DIDS-sensitive alkalinization consistent with a Na-independent Cl(-)-HCO3- exchanger. These model systems will allow the opportunity to study the normal mechanisms of IBE function and to study the pathobiology of IBE processes in disease states.

BackgroundThe PROPKD score has been proposed to stratify the risk of progression to end-stage renal disease in autosomal dominant polycystic kidney disease (ADPKD) subjects. We aimed to assess its prognostic value in a genotyped subgroup of subjects from the Tolvaptan Phase 3 Efficacy and Safety Study in Autosomal Dominant Polycystic Kidney Disease (TEMPO3/4) trial.MethodsIn the post hoc analysis, PKD1 and PKD2 were screened in 770 subjects and the PROPKD score was calculated in mutation-positive subjects (male: 1 point; hypertension <35 years: 2 points; first urologic event <35 years: 2 points; nontruncating PKD1 mutation: 2 points; truncating PKD1 mutation: 4 points). Subjects were classified into low-risk (LR; 0–3 points), intermediate-risk (IR; 4–6 points) and high-risk (HR; 7–9 points) groups.ResultsThe PROPKD score was calculated in 749 subjects (LR = 132, IR = 344 and HR = 273); age was inversely related to risk (LR = 43.6 years, IR = 39.5 years, HR = 36.2 years; P < 0.001). Subjects from the HR group had significantly higher height-adjusted total kidney volume (TKV) and rates of TKV growth. While baseline renal function was similar across all risk groups, the rate of estimated glomerular filtration rate (eGFR) decline significantly increased from LR to HR in the placebo group. Tolvaptan treatment effectiveness to reduce TKV growth was similar in all three risk categories. While tolvaptan significantly slowed eGFR decline in the IR (tolvaptan = −2.34 versus placebo = −3.33 mL/min/1.73 m2/year; P = 0.008) and HR groups (tolvaptan = −2.74 versus placebo = −3.94 mL/min/1.73 m2/year; P = 0.002), there was no difference in the LR group (tolvaptan = −2.35 versus placebo = −2.50 mL/min/1.73 m2/year; P = 0.72). Excluding the LR subjects from the analysis improved the apparent treatment effect of tolvaptan on eGFR decline.ConclusionThis study confirms the prognostic value of the PROPKD score and suggests that it could reduce costs and enhance endpoint sensitivity by enriching future study populations for rapidly progressing ADPKD subjects.

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We have produced a continuous cell line using retroviral transduction of simian virus 40 (SV40) large T antigen into epithelial cells grown from a cystoscopic bladder biopsy from a female patient with interstitial cystitis. Immortalized urothelial cells are grown in a hormonally supplemented medium in the presence of lethally irradiated NIH-3T3 fibroblast coculture. They maintain their epithelial appearance and are positive for cytokeratins. SV40 large T antigen is localized to the cell nucleus. When grown on Anocell permeable supports, the cells form a complex epithelium with scalloped luminal membranes, apical junctional complexes containing tight junctions, stratification, transepithelial resistance of 500-1,000 omega.cm2, amiloride-sensitive short-circuit current indicative of active transepithelial Na+ absorption, and functional evidence for basolateral Na-K-adenosinetriphosphatase. This immortalized bladder cell line will facilitate the study of human bladder epithelial function and the response to diverse physiological and pathophysiological stimuli.

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