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Background & Aims: Although regeneration of intrahepatic bile ducts has been extensively studied and intrahepatic progenitor cells have been identified, few studies have focussed on the extrahepatic bile duct (EHBD). We hypothesized that local progenitor cells are present within the EHBD of humans. Human EHBD specimens (n = 17) were included in this study., Methods: Specimens of normal EHBD tissue were obtained from healthy donor livers (n = 6), mildly injured EHBD from patients with cholangitis (n = 6) and severely injured EHBD from patients with ischaemic type biliary lesions (n = 5). Double immunostaining for K19 and the proliferation marker Ki-67 was performed to identify and localize proliferating cells. In addition, immunofluorescent doublestaining using antibodies against K19 and c-Kit was performed to identify and localize cholangiocytes co-expressing putative progenitor cell markers., Results: In normal EHBD, few Ki-67(+) cells were detected, whereas large numbers of Ki-67(+) were found in the diseased EHBD. In EHBD affected by cholangitis, Ki-67(+) cells were mainly located in the basal layer of the lumen. EHBD specimens from patients with ischaemic type biliary lesions displayed histological signs of epithelial cell loss and large numbers of Ki-67(+) cells were observed in the peribiliary glands. C-Kit expression was localized throughout the EHBD wall and immunofluorescent doublestaining identified a few K19(+) /c-Kit(+) cells in the luminal epithelium of the EHBD as well as in the peribiliary glands., Conclusions: These findings support the hypothesis that progenitor cells exist in the EHBD and that the peribiliary glands can be considered a local progenitor cell niche in the human EHBD., (© 2011 John Wiley & Sons A/S.)

Background: Nonanastomotic biliary strictures (NAS) are a serious complication after orthotopic liver transplantation (OLT). Matrix metalloproteinases (MMPs) are involved in connective tissue remodelling in chronic liver disease and complications after OLT., Aim: To evaluate the relationship between MMP-2 and MMP-9 gene polymorphisms and NAS., Methods: MMP-2 (-1306 C/T) and MMP-9 (-1562 C/T) gene promoter polymorphisms were analysed in 314 recipient-donor combinations. Serum levels of these MMPs were determined in subgroups of patients as well. NAS were identified with various radiological imaging studies performed within 4 years after OLT and defined as any stricture, dilation or irregularity of the intra- or extrahepatic bile ducts of the liver graft followed by an intervention, after exclusion of hepatic artery thrombosis and anastomotic strictures., Results: The average incidence of NAS was 15%. The major clinical risk factor for the development of NAS was PSC in the recipient. The presence of the MMP-2 CT genotype in donor and/or recipient was associated with a significantly higher incidence of NAS, up to 29% when both donor and recipient had the MMP-2 CT genotype (P=0.003). In the multivariate analyses, pre-OLT PSC (hazard ratio 2.1, P=0.02) and MMP-2 CT genotype (hazard ratio 3.5, P=0.003) were found to be independent risk factors for the development of NAS after OLT. No obvious association was found between NAS and the MMP-9 genotype and serum levels of the MMPs., Conclusion: MMP-2 CT genotype of donor and recipient is an independent risk factor, in addition to PSC, for the development of NAS after OLT., (© 2011 John Wiley & Sons A/S.)

Background: The role of the immune system in the pathogenesis of nonanastomotic biliary strictures (NAS) after orthotopic liver transplantation (OLT) is unclear. A loss-of-function mutation in the CC chemokine receptor 5 (CCR5-Δ32) leads to changes in the immune system, including impaired chemotaxis of regulatory T cells., Aim: To investigate the impact of the CCR5-Δ32 mutation on the development of NAS., Methods: In 384 OLTs, we assessed the CCR5 genotype in donors and recipients and correlated this with the occurrence of NAS., Results: The CCR5-Δ32 allele was found in 65 (16.9%) recipients. The cumulative incidence of NAS at 5 years was 6.5% in wild-type (Wt) recipients vs 17.2% for carriers of the CCR5-Δ32 allele (P<0.01). In recipients with CCR5-Δ32, 50% of all NAS occurred >2 years after OLT, compared with 10% in the Wt group. In multivariate regression analysis, the adjusted risk of developing NAS was four-fold higher in recipients with CCR5-Δ32 (P<0.01). The highest risk of NAS was seen in patients transplanted for primary sclerosing cholangitis (PSC), who also carried CCR5-Δ32 (relative risk 5.4, 95% confidence interval 2.2-12.9; P<0.01). Donor CCR5 genotype had no impact on the occurrence of NAS., Conclusions: Patients with the CCR5-Δ32 mutation have a four-fold higher risk of developing NAS, compared with Wt recipients. This risk is even higher in patients with CCR5-Δ32 transplanted for PSC. Late development of NAS is significantly more present in patients with CCR5-Δ32. These data suggest that the immune system plays a critical role in the development of NAS after OLT., (© 2010 John Wiley & Sons A/S.)