Cholangiocyte cilia are abnormal in syndromic and non-syndromic biliary atresia

Abstract

Biliary atresia is a neonatal disorder characterized by aggressive fibroinflammatory obliteration of the biliary tract. Approximately 20 percent of biliary atresia patients demonstrate left-right laterality defects (syndromic biliary atresia). Cilia participate in important physiologic functions in cholangiocytes, and since some ciliopathies have been associated with both laterality defects and hepatic fibrosis, we hypothesized that patients with syndromic biliary atresia exhibit abnormalities of cholangiocyte cilia that disrupt cholangiocyte homeostasis. Nine biliary atresia specimens were studied, including pre-Kasai diagnostic biopsies (n=7) and liver explants (n=2). Five specimens were from patients with laterality defects. These were compared to normal pediatric livers as well as livers affected by primary sclerosing cholangitis, Wilson’s disease, and cardiac cirrhosis. Biopsy sections were stained with antibodies against keratin 19 (a cholangiocyte marker) and acetylated α-tubulin (a cilia marker) and were visualized by confocal microscopy. Computer-assisted relative quantification was used to compare staining of cilia within bile ducts among samples. Surprisingly, cilia in biliary atresia specimens were significantly shorter, abnormal in their orientation, and less abundant compared to normal liver and disease controls regardless of the presence of a laterality defect.ConclusionThere are significant abnormalities of cholangiocyte cilia in both syndromic and non-syndromic biliary atresia livers compared to normal livers and livers affected by other cholestatic diseases. While this may result from severe cholestasis or inflammation, it may also reflect common mechanistic pathways in different forms of biliary atresia and may have important implications for understanding the progression of the disease.

Sox17 haploinsufficiency results in perinatal biliary atresia and hepatitis in C57BL/6 background mice

“…As for the left-right laterality and cilia formation [which were speculated to be closely associated with congenital biliary atresia in humans (Nakanuma et al, 2010;Chu et al, 2012)], no appreciable defects in both laterality (data not shown) and cilia formation in gallbladder/bile ducts (supplementary material Fig. S7) were observed in Sox17 +/− embryos at 15.5-16.5 dpc.…”

“…In infants and children with biliary atresia, 10~20% of the fetal/embryonic type demonstrate left-right laterality defects, and some patients with the mutation in PKHD1, encoding the ciliary protein fibrocystin, are closely correlated with a ciliopathy with clinical features that resemble biliary atresia (Nakamura et al, 2010;Hartley et al, 2011). Moreover, cilia structure and distribution within bile ducts were previously shown to be affected in the specimens of human biliary atresia: shorter, abnormal orientation, and less abundant cilia in the biliary atresia specimens (Chu et al, 2012). These findings raise a possible association of the reduced Sox17 activity in the gallbladder primordium with the ciliopathy associated with congenital biliary atresia.…”

Identification of a plant isoflavonoid that causes biliary atresia

“…We previously demonstrated that extrahepatic cholangiocyte primary cilia are decreased in both human BA and the mouse RRV BA model (43, 44). For this reason, we examined cilia in primary neonatal mouse extrahepatic cholangiocytes treated with either biliatresone or the nontoxic isoflavanone-3 that copurifies with biliatresone.…”

Genetic Contributors and Modifiers of Biliary Atresia

“…Below the diaphragm, in addition to biliary tract anomalies, patients may present with midline or left-sided liver, polysplenia or asplenia, and interrupted inferior vena cava [40]. The laterality defects exhibited in biliary atresia splenic malformation syndrome are phenotypically similar to those observed in the ciliopathies, a heterogenous group of diseases caused by functional and structural defects in genes that encode cilia proteins [41,42,43,44,45,46,47,48]. Cilia are evolutionarily conserved, aid in establishing the left-right axis in vertebrates, and are present on many cell types, including the apical surface of cholangiocytes, where cilium function is integral to bile flow and bile ductular formation [49].…”