Familial biliary atresia in three siblings including twins

Investigating the genetic profile of familial atypical cystic fibrosis patients (DeltaF508-CFTR) with neonatal biliary atresia

Biliary atresia (BA) is a progressive inflammatory process of the biliary tree resulting in biliary obstruction. No single known genetic or environmental factor has been established to cause BA. Cystic fibrosis (CF) is a rare cause of neonatal cholestasis, and it has never been described in familial BA cases. Here, we investigate two siblings of first-degree consanguineous parents presenting with neonatal BA. Shortly after the Kasai operation, the proband developed severe respiratory symptoms attributable to a missed CF diagnosis. This was discovered after re-investigating the family history, which revealed a first-degree cousin with CF who did not manifest BA. Afterwards, we identified a pathogenic variant (DeltaF508) in CFTR in both BA-affected siblings along with their cousin. This intrigued us to study the molecular etiology behind the familial BA presentations, which exclusively contributed to BA-pathogenesis in BA-CF-affected siblings and not in their CF-only affected cousin. We applied a multistep approach to investigate the variant profile of both siblings' and their cousin's exomes. We curated the genes whose variants were shared by the BA-CF siblings but absent or heterozygous in their CF-only-affected cousin. Consequently, we identified three candidate genes (SNAPC4, UCK1, and ZHX2) besides CFTR. We propose that these genes act cumulatively or individually in inducing BA-pathogenesis-either by aggravating the biliary damage in the context of CF or increasing the susceptibility of BA as a separate CF-comorbidity. To our knowledge, this is the first report of DeltaF508 in CFTR with familial neonatal BA cases.

Novel findings from family-based exome sequencing for children with biliary atresia

Biliary atresia (BA) is a progressive inflammation and fibrosis of the biliary tree characterized by the obstruction of bile flow, which results in liver failure, scarring and cirrhosis. This study aimed to explore the elusive aetiology of BA by conducting whole exome sequencing for 41 children with BA and their parents (35 trios, including 1 family with 2 BA-diagnosed children and 5 child-mother cases). We exclusively identified and validated a total of 28 variants (17 X-linked, 6 de novo and 5 homozygous) in 25 candidate genes from our BA cohort. These variants were among the 10% most deleterious and had a low minor allele frequency against the employed databases: Kinh Vietnamese (KHV), GnomAD and 1000 Genome Project. Interestingly, AMER1, INVS and OCRL variants were found in unrelated probands and were first reported in a BA cohort. Liver specimens and blood samples showed identical variants, suggesting that somatic variants were unlikely to occur during morphogenesis. Consistent with earlier attempts, this study implicated genetic heterogeneity and non-Mendelian inheritance of BA.

Identification of a wide spectrum of ciliary gene mutations in nonsyndromic biliary atresia patients implicates ciliary dysfunction as a novel disease mechanism

Background

Biliary atresia (BA) is the most common obstructive cholangiopathy in neonates, often progressing to end-stage cirrhosis. BA pathogenesis is believed to be multifactorial, but the genetic contribution, especially for nonsyndromic BA (common form: > 85%) remains poorly defined.

Methods

We conducted whole exome sequencing on 89 nonsyndromic BA trios to identify rare variants contributing to BA etiology. Functional evaluation using patients’ liver biopsies, human cell and zebrafish models were performed. Clinical impact on respiratory system was assessed with clinical evaluation, nasal nitric oxide (nNO), high speed video analysis and transmission electron microscopy.

Findings

We detected rare, deleterious de novo or biallelic variants in liver-expressed ciliary genes in 31.5% (28/89) of the BA patients. Burden test revealed 2.6-fold (odds ratio (OR) [95% confidence intervals (CI)]= 2.58 [1.15–6.07], adjusted p = 0.034) over-representation of rare, deleterious mutations in liver-expressed ciliary gene set in patients compared to controls. Functional analyses further demonstrated absence of cilia in the BA livers with KIF3B and TTC17 mutations, and knockdown of PCNT, KIF3B and TTC17 in human control fibroblasts and cholangiocytes resulted in reduced number of cilia. Additionally, CRISPR/Cas9-engineered zebrafish knockouts of KIF3B, PCNT and TTC17 displayed reduced biliary flow. Abnormally low level of nNO was detected in 80% (8/10) of BA patients carrying deleterious ciliary mutations, implicating the intrinsic ciliary defects.

Interpretation

Our findings support strong genetic susceptibility for nonsyndromic BA. Ciliary gene mutations leading to cholangiocyte cilia malformation and dysfunction could be a key biological mechanism in BA pathogenesis.

Funding

The study is supported by General Research Fund, HMRF Commissioned Paediatric Research at HKCH and Li Ka Shing Faculty of Medicine Enhanced New Staff Start-up Fund.

Biliary atresia in twins: a systematic review and meta-analysis

PURPOSE

Biliary atresia (BA) in twins is extremely rare reported in the literature, but twin studies are useful methods of examining the associated factors of a complex disease. The objective of this study was to analyze the characteristics and patterns of biliary atresia in twins from reviewing available articles.

METHODS

PubMed and EMBASE databases were reviewed for related articles using the keywords ''biliary atresia'', ''twins'', ''monozygotic (MZ)'', and ''dizygotic (DZ)'', including relevant papers in the reference lists.

RESULTS

This analysis was extracted from 12 articles, with a total of 35 twin pairs included. BA was found in 36 out of 70 twin subjects (51.4%), of which had an even gender split. 97.1% twins were discordant, among 55.9% of which were monozygotic twin sets, indicating that BA may be related to genetic phenotype or penetrance. Isolated BA was the largest group with 27 (75%) affected twins. Only one pair of dizygotic twins (2.9%) demonstrate concordance for BA, and have one affected family member.

CONCLUSION

BA was found in nearly half of twin subjects with an even gender split. Isolated BA was the largest group, in which the number of monozygotic twins was similar with dizygotic twins, so the onset of the disease may not associate with the zygosity of twins. Most of twin sets had discordant disease presentation, especially monozygotic twins therein, emphasizing the role of epigenetic factor in the pathogenesis of BA. Future studies should take genetic testing among any twin sets in BA, especially the disease-associated mutations, thus be useful to investigate the etiology of disease.

Biliary atresia in twins'population: a retrospective multicenter study in mainland China

AIM

We evaluated the demographic of biliary atresia (BA) children from twins family and aimed to investigated what it can add to the twins' literature and our understanding of the disease.

METHODS

This study contains 11 medical centers in mainland China and the medical record of twins with BA was retrospectively analyzed from January 2012 to December 2018. Follow-up was carried out by out-patient review and questionnaire.

RESULTS

The study included 19 twin pairs in whom there was discordance for BA. Sixteen (84.2%) affected twin underwent Kasai Procedure (KP); median age at KP was 78 (49-168) days. There were ten affected twins that became jaundice-free at 3 months post-KP, and eight occurred with different degrees of cholangitis post-KP. Six affected twins received Liver Transplantation (LT) successfully. The 2 year native liver survival rate and the 2 year overall survival rate of affected twins were 61.1 and 94.4%, respectively. There were three affected monozygotic (MZ) twins and one healthy co-twin with BA-associated congenital malformations, all of which were cardiac malformations. The number of virus infection of affected MZ twins was significantly more (p = 0.04) than affected dizygotic (DZ) twin.

CONCLUSIONS

Discordance for BA in 19 pairs of twins supported that BA may be related to genetic phenotype or penetrance. The difference in genetic background between MZ and DZ affects the susceptibility of the host to virus infection. High acceptance of KP (84.2%) in our study implied a high motivation for treatment for twins with BA. Delays of KP (78 days) in affected twin may be related to the postnatal gradual onset and the late diagnosis.

Biliary atresia: pathology, etiology and pathogenesis

Biliary atresia is a progressive fibrosing obstructive cholangiopathy of the intrahepatic and extrahepatic biliary system, resulting in obstruction of bile flow and neonatal jaundice. Histopathological findings in liver biopsies include the expansion of the portal tracts, with edematous fibroplasia and bile ductular proliferation, with bile plugs in duct lumen. Lobular morphological features may include variable multinucleate giant cells, bilirubinostasis and hemopoiesis. The etiopathogenesis of biliary atresia is multifactorial and multiple pathomechanisms have been proposed. Experimental and clinical studies have suggested that viral infection initiates biliary epithelium destruction and release of antigens that trigger a Th1 immune response, which leads to further injury of the bile duct, resulting in inflammation and obstructive scarring of the biliary tree. It has also been postulated that biliary atresia is caused by a defect in the normal remodelling process. Genetic predisposition has also been proposed as a factor for the development of biliary atresia.

Identification of Polycystic Kidney Disease 1 Like 1 Gene Variants in Children With Biliary Atresia Splenic Malformation Syndrome

Biliary atresia (BA) is the most common cause of end-stage liver disease in children and the primary indication for pediatric liver transplantation, yet underlying etiologies remain unknown. Approximately 10% of infants affected by BA exhibit various laterality defects (heterotaxy) including splenic abnormalities and complex cardiac malformations-a distinctive subgroup commonly referred to as the biliary atresia splenic malformation (BASM) syndrome. We hypothesized that genetic factors linking laterality features with the etiopathogenesis of BA in BASM patients could be identified through whole-exome sequencing (WES) of an affected cohort. DNA specimens from 67 BASM subjects, including 58 patient-parent trios, from the National Institute of Diabetes and Digestive and Kidney Diseases-supported Childhood Liver Disease Research Network (ChiLDReN) underwent WES. Candidate gene variants derived from a prespecified set of 2,016 genes associated with ciliary dysgenesis and/or dysfunction or cholestasis were prioritized according to pathogenicity, population frequency, and mode of inheritance. Five BASM subjects harbored rare and potentially deleterious biallelic variants in polycystic kidney disease 1 like 1 (PKD1L1), a gene associated with ciliary calcium signaling and embryonic laterality determination in fish, mice, and humans. Heterozygous PKD1L1 variants were found in 3 additional subjects. Immunohistochemical analysis of liver from the one BASM subject available revealed decreased PKD1L1 expression in bile duct epithelium when compared to normal livers and livers affected by other noncholestatic diseases. Conclusion: WES identified biallelic and heterozygous PKD1L1 variants of interest in 8 BASM subjects from the ChiLDReN data set; the dual roles for PKD1L1 in laterality determination and ciliary function suggest that PKD1L1 is a biologically plausible, cholangiocyte-expressed candidate gene for the BASM syndrome.

Prematurity and biliary atresia: a 30-year observational study

AIM OF STUDY

The diagnosis of biliary atresia (BA) remains challenging and delay can lead to significant morbidity with time to surgery a key factor in determining outcome. Prematurity may impact on outcome potentially delaying diagnosis. We sought to assess whether the premature BA infants (PBA) have a delayed time to surgery and as such, worse outcomes?

METHODS

Review of a single-centre prospectively maintained database. Prematurity was defined as delivery < 37/40 gestation. PBA was compared with date-matched term biliary atresia controls on a 2:1 basis. Primary outcomes were clearance of jaundice (< 20 μmol/L) and native liver survival. A retrospective assessment of liver fibrosis was made on biopsies at diagnosis and at Kasai portoenterostomy (KPE) in both premature and term cohorts. Data are quoted as median (range) unless indicated. A P value of ≤ 0.05 was considered statistically significant.

RESULTS

21 (female n = 14, 67%) premature infants with BA were treated in the period Jan. 1988-Dec. 2016 and compared with 41 contemporaneous term BA controls. Median gestation was 33 (29-36) weeks and birth weight 1930 (948-4230)g. Twin pregnancy (n = 10) was the leading cause for prematurity and significantly higher than the controls (48 vs. 0%; P < 0.0001). Maternal co-morbidity was high (n = 10, 48%) including pre-eclampsia (19%) and diabetes (14%). Liver biopsy was performed in 19 (90%) patients (all diagnostic) at a median of 57 (4-266) days. Delayed diagnosis (> 50 days) was seen in n = 13 but not associated with parenteral nutrition use (46 vs. 33%, P = 0.59) or phototherapy (50 vs. 83%, P = 0.19). Both BASM (33 vs. 7.5%; P = 0.01) and duodenal atresia (19 vs. 0%; P = 0.01) were seen more frequently in the PBA cohort. Mean fibrosis scores (Ishak) from diagnostic biopsies were lower in the premature group than the control group (2.71 vs. 3.53, P = 0.043) indicating less fibrosis but this equalized by time of subsequent KPE (P = 0.17). Primary surgery was Kasai portoenterostomy (n = 20) at an older median age than controls (65 vs. 56 days; P = 0.06). Liver transplantation was the primary procedure in one late-presenting child. There was an increased but non-significant clearance of jaundice in the PBA group [n = 12/20 (60%) vs 20/41 (48%); P = 0.23] post-KPE. Native liver survival and true survival were not different (P = 0.58 and 0.23).

CONCLUSIONS

PBA infants have similar outcomes to term infants, despite delayed diagnosis and higher frequency of the syndromic form. The high incidence of discordant twins supports the theory that epigenetic modifications could contribute to the pathogenesis of BA.

LEVEL OF EVIDENCE

IIIc Retrospective Matched Cohort Study.

Epidemiology of Biliary Atresia in Korea

Biliary atresia (BA) is the major cause of cholestasis and the leading indication for liver transplantation (LT). However, the incidence of BA in Korea has not been reported. The aim of this study was to investigate the incidence and clinical outcomes of BA in Korea. We used the Korean universal health insurance database and extracted data regarding BA patients younger than 18 years of age admitted between 2011 and 2015. The incidence of BA was calculated by dividing the number of BA patients by the number of live births. Two hundred forty infants were newly diagnosed with BA. A total of 963 BA patients younger than 18 years of age were followed up for 5 years. The overall incidence of BA was 1.06 cases per 10,000 live births. The incidence of BA was 1.4 times higher for female patients than for male patients. Additionally, significant seasonal variation was observed; in particular, the incidence of BA was 2 times higher from June through August than from December through February. Congenital anomalies were found in 38 of 240 patients (15.8%). Congenital heart diseases were major associated congenital anomalies (6.3%). Several complications developed during the study period, including cholangitis (24.0%), varix (6.2%), and gastrointestinal bleeding (4.4%). Three hundred and one of the 963 BA patients under 18 years of age (31.3%) received LT for BA. The incidence of BA is higher in Korea than that in Western countries. We also report significant gender-associated differences and seasonal variation with respect to the incidence of BA.

Association between rs17095355 polymorphism on 10q24 and susceptibility to biliary atresia: a meta-analysis

OBJECTIVE

Recent studies have identified 10q24-rs17095355 as a susceptibility locus for biliary atresia (BA). To more precisely estimate the association between the rs17095355 polymorphism and BA risk, a meta-analysis was performed.

METHODS

A comprehensive search was conducted to examine all the eligible studies by electronic databases including Elsevier Science Direct, Pubmed, Google Scholar, China National Knowledge Infrastructure (CNKI) and Chinese Biomedical Literature (CBM) up to December 2015. Odds ratios (ORs) and 95% confidence intervals (CIs) were calculated to assess the strength of the association.

RESULTS

A total of 6 comparisons from 5 relevant studies involving 1000 patients and 3257 controls were included to analyze the association between rs17095355 and BA risk. The pooled OR for T allele of rs17095355 was 1.72 (95%CI 1.53-1.92, p < 0.01) in BA. Stratification by ethnicity indicated the degree of risk of rs17095355 with BA susceptibility was similar in populations of Asian origin. The pooled OR was 1.81 (95%CI 1.60-2.06, p < 0.01).

CONCLUSIONS

This meta-analysis confirms the association of rs17095355 polymorphism and BA development, especially in Asians. More original studies with large sample are needed to replicate this genetic association in different ethnic groups.

Pathogenesis of biliary atresia: defining biology to understand clinical phenotypes

Biliary atresia is a severe cholangiopathy of early infancy that destroys extrahepatic bile ducts and disrupts bile flow. With a poorly defined disease pathogenesis, treatment consists of the surgical removal of duct remnants followed by hepatoportoenterostomy. Although this approach can improve the short-term outcome, the liver disease progresses to end-stage cirrhosis in most children. Further improvement in outcome will require a greater understanding of the mechanisms of biliary injury and fibrosis. Here, we review progress in the field, which has been fuelled by collaborative studies in larger patient cohorts and the development of cell culture and animal model systems to directly test hypotheses. Advances include the identification of phenotypic subgroups and stages of disease based on clinical, pathological and molecular features. Stronger evidence exists for viruses, toxins and gene sequence variations in the aetiology of biliary atresia, triggering a proinflammatory response that injures the duct epithelium and produces a rapidly progressive cholangiopathy. The immune response also activates the expression of type 2 cytokines that promote epithelial cell proliferation and extracellular matrix production by nonparenchymal cells. These advances provide insight into phenotype variability and might be relevant to the design of personalized trials to block progression of liver disease.

Laparoscopic portoenterostomy versus open portoenterostomy for the treatment of biliary atresia: a systematic review and meta-analysis of comparative studies

BACKGROUND

Open portoenterostomy (OPE) remains the mainstay in treatment of biliary atresia, while during the past several years, the laparoscopic portoenterostomy (LPE) has been widely introduced. However, safety of LPE remains a major concern. Thus, we conducted a systematic review and meta-analysis to review the currently available data comparing LPE and OPE.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

Medline, Ovid, Elsevier, Google Scholar Embase, Cohrane library.

STUDY SELECTION

Comparative cohort studies.

DATA EXTRACTION

Two investigators independently assessed selected studies and extracted the following information: study characteristics, quality, outcomes data, etc.

RESULTS

Eleven studies about the effectiveness of LPE compared with OPE were performed by meta-analysis. Meta-analysis found no significant difference between the two groups in operative time, hospital stay, intraoperative blood loss, early clearance of jaundice, cholangitis and variceal bleeding. In addition, the rate of 2-year survival with native liver was significantly high in OPE group than in LPE group.

CONCLUSION

Laparoscopic portoenterostomy could not replace open portoenterostomy and open Kasai portoenterostomy remains the gold standard in the treatment of biliary atresia.

Association between single nucleotide polymorphisms in the ADD3 gene and susceptibility to biliary atresia

Background and Objectives

Based on the results of previous studies, the ADD3 gene, located in the 10q24.2 region, may be a susceptibility gene of biliary atresia (BA). In this study, two single nucleotide polymorphisms (SNPs) in the ADD3 gene, rs17095355 C/T and rs10509906 G/C, were selected to investigate whether there is an association between these SNPs and susceptibility to BA in a Chinese population.

Methods

A total of 752 Han Chinese (134 BA cases and 618 ethnically matched healthy controls) were included in the present study. The ADD3 gene polymorphisms were genotyped using a TaqMan genotyping assay.

Results

Positive associations were found for the SNP rs17095355 in the codominant model; specifically, the frequencies of the CT and TT genotypes and the T allele were higher in the cases than the controls, demonstrating a significant risk for BA (odds ratio [OR] = 1.62, 95% confidence interval [CI] = 1.02–2.58; OR = 2.89, 95% CI = 1.72–4.86; and OR = 1.75, 95% CI = 1.34–2.29, respectively). Regarding rs10509906, the per-C-allele conferred an OR of 0.70 (95% CI = 0.49–1.00) under the additive model. A greater risk of BA was associated with the T_a-G_b (a for rs17095355 and b for rs10509906) haplotype (OR = 1.82, 95% CI = 1.27–2.61) compared with the C_a-C_b haplotype.

Conclusion

This study suggests that the ADD3 gene plays an important role in BA pathogenesis and reveals a significant association between two SNPs, rs17095355 and rs10509906, and BA.

Maternal microchimerism in biliary atresia: are maternal cells effector cells, targets, or just bystanders?

The etiology of biliary atresia (BA) is unknown; however, the liver histology is similar to that observed in immune-mediated hepatic disorders. Liver fibrosis in BA progresses even after bile drainage has been achieved by the Kasai operation. Maternal microchimerism has been purported to play a part in the pathogenesis of BA as well as certain autoimmune diseases. However, the role of maternal cells has not yet been determined in BA. Specifically, it is unknown whether these maternal cells function as maternal effector T lymphocytes, or targets or bystanders. We currently hypothesize that the first hit is due to GvHD interaction by engrafted maternal effector T lymphocytes. Furthermore, we suggest that the secondary effects that are manifested by progressive cirrhosis are caused either by maternal chimeric effector T lymphocytes (e.g., GvHD interaction) or targets (e.g., HvGD interaction). Based on our hypothesis, mixed lymphocyte reactions between patients and their mothers might shed light on the etiopathogenesis and prognostic indicators.

Etiology of biliary atresia as a developmental anomaly: recent advances

Biliary atresia (BA) is a progressive fibro-obliterative cholangiopathy affecting the extra- and intrahepatic biliary tree to various degrees and resulting in obstructive bile flow, cholestasis and icterus in neonates. It is the most common cause of pediatric liver transplantation. The etiology of BA is still unclear, although there is some evidence pointing to viral, toxic, and multiple genetic factors. For new therapeutic options other than liver transplantation to be developed, a greater understanding of the pathogenesis of BA is indispensable. The fact that the pathology of BA develops during a period of biliary growth and remodeling suggests an involvement of developmental anomalies. Recent studies indicate an association of the etiology of BA with some genetic factors such as laterality genes, epigenetic regulation and/or microRNA function. In this paper, we present an overview of recent advances in the understanding of the disease focusing on bile duct developmental anomaly.

Common genetic variants regulating ADD3 gene expression alter biliary atresia risk

BACKGROUND & AIMS

Biliary atresia (BA) is a rare and most severe cholestatic disease in neonates, but the pathogenic mechanisms are unknown. Through a previous genome wide association study (GWAS) on Han Chinese, we discovered association of the 10q24.2 region encompassing ADD3 and XPNPEP1 genes, which was replicated in Chinese and Thai populations. This study aims to fully characterize the genetic architecture at 10q24.2 and to reveal the link between the genetic variants and BA.

METHODS

We genotyped 107 single nucleotide polymorphisms (SNPs) in 10q24.2 in 339 Han Chinese patients and 401 matched controls using Sequenom. Exhaustive follow-up studies of the association signals were performed.

RESULTS

The combined BA-association p-value of the GWAS SNP (rs17095355) achieved 6.06×10(-10). Further, we revealed the common risk haplotype encompassing 5 tagging-SNPs, capturing the risk-predisposing alleles in 10q24.2 [p=5.32×10(-11); odds ratio, OR: 2.38; confidence interval, CI: (2.14-2.62)]. Through Sanger sequencing, no deleterious rare variants (RVs) residing in the risk haplotype were found, dismissing the theory of "synthetic" association. Moreover, in bioinformatics and in vivo genotype-expression investigations, the BA-associated potentially regulatory SNPs correlated with ADD3 gene expression (n=36; p=0.0030). Remarkably, the risk haplotype frequency coincides with BA incidences in the population, and, positive selection (favoring the derived alleles that arose from mutations) was evident at the ADD3 locus, suggesting a possible role for the BA-associated common variants in shaping the general population diversity.

CONCLUSIONS

Common genetic variants in 10q24.2 can alter BA risk by regulating ADD3 expression levels in the liver, and may exert an effect on disease epidemiology and on the general population.

Evidence from human and zebrafish that GPC1 is a biliary atresia susceptibility gene

BACKGROUND & AIMS

Biliary atresia (BA) is a progressive fibroinflammatory disorder of infants involving the extrahepatic and intrahepatic biliary tree. Its etiology is unclear but is believed to involve exposure of a genetically susceptible individual to certain environmental factors. BA occurs exclusively in the neonatal liver, so variants of genes expressed during hepatobiliary development could affect susceptibility. Genome-wide association studies previously identified a potential region of interest at 2q37. We continued these studies to narrow the region and identify BA susceptibility genes.

METHODS

We searched for copy number variants that were increased among patients with BA (n = 61) compared with healthy individuals (controls; n = 5088). After identifying a candidate gene, we investigated expression patterns of orthologues in zebrafish liver and the effects of reducing expression, with morpholino antisense oligonucleotides, on biliary development, gene expression, and signal transduction.

RESULTS

We observed a statistically significant increase in deletions at 2q37.3 in patients with BA that resulted in deletion of one copy of GPC1, which encodes glypican 1, a heparan sulfate proteoglycan that regulates Hedgehog signaling and inflammation. Knockdown of gpc1 in zebrafish led to developmental biliary defects. Exposure of the gpc1 morphants to cyclopamine, a Hedgehog antagonist, partially rescued the gpc1-knockdown phenotype. Injection of zebrafish with recombinant Sonic Hedgehog led to biliary defects similar to those of the gpc1 morphants. Liver samples from patients with BA had reduced levels of apical GPC1 in cholangiocytes compared with samples from controls.

CONCLUSIONS

Based on genetic analysis of patients with BA and zebrafish, GPC1 appears to be a BA susceptibility gene. These findings also support a role for Hedgehog signaling in the pathogenesis of BA.

Changes in epigenetic regulation of CD4+ T lymphocytesin biliary atresia

Biliary atresia (BA) is a virus-induced autoimmune disease associated with abnormal DNA methylation patterns that contribute to disease presentation. This study examined DNA methylation patterns, changes to genes associated with methylation regulation, and changes to the autoimmune-related gene interferon gamma (IFN-γ) in CD4+ T cells from BA patients. We demonstrated that genomic DNA isolated from CD4+ T cells harvested from infants presenting with BA were hypomethylated relative to healthy controls. In addition, DNA methyltransferase (DNMT1) and DNMT3a mRNA levels were significantly lower in BA CD4+ T cells compared with controls and methyl-DNA-binding domain proteins (MBD1) mRNA expression (but not MBD4 detected at higher levels in BA patients), which was significantly lower in CD4+ T cells from BA infants than in controls. DNMT1 expression positively correlated with global DNA methylation in BA CD4+ T cells. IFN-γ mRNA expression levels in BA patients were also significantly increased, and the IFN-γ gene promoter region was hypomethylated in BA CD4+ T cells compared with controls and negatively correlated with DNA methylation. These data suggest that methylation changes in CD4+ cells may contribute to BA disease presentation and progression by affecting the expression of genes associated with autoimmunity.

Patients with biliary atresia have elevated direct/conjugated bilirubin levels shortly after birth

OBJECTIVES

Healthy infants are thought to acquire biliary atresia (BA) in the first weeks of life. Because those diagnosed earlier have better outcomes, we were interested in determining the earliest time BA could be detected. We started by examining the immediate postnatal period, hypothesizing that newborns would not yet have acquired disease and still have normal direct/conjugated bilirubin (DB/CB) levels.

PATIENTS AND METHODS

Newborn DB/CB levels were obtained retrospectively from birth hospitals. Subjects with BA were born between 2007 and 2010 and cared for at Texas Children's Hospital. Those with BA splenic malformation syndrome or born prematurely were excluded. Control subjects were term newborns who later never developed neonatal liver disease.

RESULTS

Of the 61 subjects with BA, 56% had newborn DB/CB levels measured. All DB/CB levels exceeded laboratory norms and rose over time. At 24 to 48 hours of life, subjects with BA had mean DB levels significantly higher than those of controls (1.4 ± 0.43 vs. 0.19 ± 0.075 mg/dL, P < .0001), even while their mean total bilirubin (TB) levels remained below phototherapy limits. Finally, despite the elevated DB/CB levels, the majority of patients (79%) had normal DB:TB ratios ≤ 0.2.

CONCLUSIONS

Patients with BA have elevated DB/CB levels shortly after birth. To detect affected infants earlier and improve outcomes, the results suggest two possibilities: (1) screen all newborns for elevated DB/CB levels, rather than just those who appear jaundiced; and then (2) follow all newborns with elevated DB/CB levels, rather than just those with DB:TB ratios >0.2.

Biliary atresia

Biliary atresia (BA) is a cholangiodestructive disease affecting biliary tract, which ultimately leads to cirrhosis, liver failure and death if not treated. The incidence is higher in Asian countries than in Europe. Up to 10% of cases have other congenital anomalies, such as polysplenia, asplenia, situs inversus, absence of inferior vena cava and pre-duodenal portal vein, for which we have coined the term Biliary Atresia Splenic Malformation (BASM) syndrome. For these infants the aetiology lies within the first trimester of gestation. For others affected with BA, aetiology is more obscure and perinatal destruction of fully-formed ducts perhaps by the action of hepatotropic viruses has been suggested. Whatever the cause, the lumen of the extrahepatic duct is obliterated at a variable level and this forms the basis for the commonest classification (Types I, II, III). All patients with BA present with varying degree of conjugated jaundice, pale non-pigmented stools and dark urine. Key diagnostic tests include ultrasonography, biochemical liver function tests, viral serology, and (in our centre) a percutaneous liver biopsy. In some centres, duodenal intubation and measurement of intralumenal bile is the norm. Currently BA is being managed in two stages. The first stage involves the Kasai operation, which essentially excises all extrahepatic biliary remnants leaving a transected portal plate, followed by biliary reconstruction using a Roux loop onto that plate as a portoenterostomy. If bile flow is not restored by Kasai procedure or life-threatening complications of cirrhosis ensue then consideration should be given to liver transplantation as a second stage. The outcome following the Kasai operation can be assessed in two ways: clearance of jaundice to normal values and the proportion who survive with their native liver. Clearance of jaundice (<2 mg/dL or <34 µmol/L) after Kasai has been reported to be around 60%, whereas five years survival with native liver ranges from 40% to 65%.

DNA hypomethylation causes bile duct defects in zebrafish and is a distinguishing feature of infantile biliary atresia

Infantile cholestatic disorders arise in the context of progressively developing intrahepatic bile ducts. Biliary atresia (BA), a progressive fibroinflammatory disorder of extra- and intrahepatic bile ducts, is the most common identifiable cause of infantile cholestasis and the leading indication for liver transplantation in children. The etiology of BA is unclear, and although there is some evidence for viral, toxic, and complex genetic causes, the exclusive occurrence of BA during a period of biliary growth and remodeling suggests an importance of developmental factors. Interestingly, interferon-γ (IFN-γ) signaling is activated in patients and in the frequently utilized rhesus rotavirus mouse model of BA, and is thought to play a key mechanistic role. Here we demonstrate intrahepatic biliary defects and up-regulated hepatic expression of IFN-γ pathway genes caused by genetic or pharmacological inhibition of DNA methylation in zebrafish larvae. Biliary defects elicited by inhibition of DNA methylation were reversed by treatment with glucocorticoid, suggesting that the activation of inflammatory pathways was critical. DNA methylation was significantly reduced in bile duct cells from BA patients compared to patients with other infantile cholestatic disorders, thereby establishing a possible etiologic link between decreased DNA methylation, activation of IFN-γ signaling, and biliary defects in patients.

CONCLUSION

Inhibition of DNA methylation leads to biliary defects and activation of IFN-γ-responsive genes, thus sharing features with BA, which we determine to be associated with DNA hypomethylation. We propose epigenetic activation of IFN-γ signaling as a common etiologic mechanism of intrahepatic bile duct defects in BA.

Genomic alterations in biliary atresia suggest region of potential disease susceptibility in 2q37.3

Biliary atresia (BA) is a progressive, idiopathic obliteration of the extrahepatic biliary system occurring exclusively in the neonatal period. It is the most common disease leading to liver transplantation in children. The etiology of BA is unknown, although infectious, immune and genetic causes have been suggested. Although the recurrence of BA in families is not common, there are more than 30 multiplex families reported and an underlying genetic susceptibility has been hypothesized. We screened a cohort of 35 BA patients for genomic alterations that might confer susceptibility to BA. DNA was genotyped on the Illumina Human Hap 550 Beadchip platform, which analyzes over 550,000 single nucleotide polymorphisms (SNPs) for genomic deletions and duplications. Areas of increased and decreased copy number were compared to those found in control populations. To identify regions that could serve as susceptibility factors for BA, we searched for regions that were found in BA patients, but not in controls. We identified two unrelated BA patients with overlapping heterozygous deletions of 2q37.3. Patient 1 had a 1.76 Mb (280 SNP), heterozygous deletion containing 30 genes. Patient 2 had a 5.87 Mb (1,346 SNP) heterozygous deletion containing 55 genes. The overlapping 1.76 Mb deletion on chromosome 2q37.3 from 240,936,900 to 242,692,820 constitutes the critical region and the genes within this region could be candidates for susceptibility to BA.

Genome-wide association study identifies a susceptibility locus for biliary atresia on 10q24.2

Biliary atresia (BA) is characterized by the progressive fibrosclerosing obliteration of the extrahepatic biliary system during the first few weeks of life. Despite early diagnosis and prompt surgical intervention, the disease progresses to cirrhosis in many patients. The current theory for the pathogenesis of BA proposes that during the perinatal period, a still unknown exogenous factor meets the innate immune system of a genetically predisposed individual and induces an uncontrollable and potentially self-limiting immune response, which becomes manifest in liver fibrosis and atresia of the extrahepatic bile ducts. Genetic factors that could account for the disease, let alone for its high incidence in Chinese, are to be investigated. To identify BA susceptibility loci, we carried out a genome-wide association study (GWAS) using the Affymetrix 5.0 and 500 K marker sets. We genotyped nearly 500 000 single-nucleotide polymorphisms (SNPs) in 200 Chinese BA patients and 481 ethnically matched control subjects. The 10 most BA-associated SNPs from the GWAS were genotyped in an independent set of 124 BA and 90 control subjects. The strongest overall association was found for rs17095355 on 10q24, downstream XPNPEP1, a gene involved in the metabolism of inflammatory mediators. Allelic chi-square test P-value for the meta-analysis of the GWAS and replication results was 6.94 x 10(-9). The identification of putative BA susceptibility loci not only opens new fields of investigation into the mechanisms underlying BA but may also provide new clues for the development of preventive and curative strategies.

Biliary atresia

Biliary atresia is a rare disease of infancy, which has changed within 30 years from being fatal to being a disorder for which effective palliative surgery or curative liver transplantation, or both, are available. Good outcomes for infants depend on early referral and timely Kasai portoenterostomy, and thus a high index of suspicion is needed for investigation of infants with persistent jaundice. In centres with much experience of treating this disorder, up to 60% of children will achieve biliary drainage after Kasai portoenterostomy and will have serum bilirubin within the normal range within 6 months. 80% of children who attain satisfactory biliary drainage will reach adolescence with a good quality of life without undergoing liver transplantation. Although much is known about management of biliary atresia, many aspects are poorly understood, including its pathogenesis. Several hypotheses exist, implicating genetic predisposition and dysregulation of immunity, but the cause is probably multifactorial, with obliterative extrahepatic cholangiopathy as the common endpoint. Researchers are focused on identification of relevant genetic and immune factors and understanding serum and hepatic factors that drive liver fibrosis after Kasai portoenterostomy. These factors might become therapeutic targets to halt the inevitable development of cirrhosis and need for liver transplantation.

Maternal HLA class I compatibility in patients with biliary atresia

Biliary atresia (BA) is an inflammatory cholangiopathy of unknown etiology. Maternal microchimerism has been identified in the livers of patients with BA. We analyzed the human leukocyte antigen (HLA) compatibility between 57 BA patient-mother pairs and 50 control-mother pairs. The HLA class I matching was significantly more frequent in BA pairs (odds ratio [OR]=2.46) than controls. Similar results were also found in child-to-mother HLA compatibility (OR=2.16). Our results indicate that patients with BA have an immunogenetic histocompatible relationship with their mothers, which may result in an increase in maternal microchimerism found in BA.

Mother-to-daughter occurrence of biliary atresia: a case report

We herein report a case of mother-to-daughter occurrence of biliary atresia (BA). The mother underwent a Kasai hepatic portoenterostomy at the age of 64 days with a diagnosis of type III BA. Her postoperative course was uneventful, with a good bile discharge, and she became pregnant at the age of 20 years. At 21 weeks of gestational age, fetal ultrasonographic examination of the baby revealed a cystic mass at the hepatic hilum. The baby was born via vaginal delivery at 41 weeks of gestation with a birth weight of 3269 g. Because of an increasing direct bilirubin level and the absence of bile excretion, a laparotomy was performed at the age of 29 days. Intraoperative cholangiography revealed the diagnosis of BA I-cyst, and a hepaticojejunostomy was performed with a good bile discharge. To our knowledge, these patients are the first occurrence of BA in a transmission pattern of mother to daughter.

Biliary atresia: recent progress

Extrahepatic biliary atresia (EHBA), an inflammatory sclerosing cholangiopathy, is the leading indication for liver transplantation in children. The cause is still unknown, although possible infectious, genetic, and immunologic etiologies have received much recent focus. These theories are often dependent on each other for secondary or coexisting mechanisms. Concern for EHBA is raised by a cholestatic infant, but the differential diagnosis is large and the path to diagnosis remains varied. Current treatment is surgical with an overall survival rate of approximately 90%. The goals of this article are to review the important clinical aspects of EHBA and to highlight some of the more recent scientific and clinical developments contributing to our understanding of this condition.

The biliary atresia splenic malformation syndrome: a 28-year single-center retrospective study

We carried out a retrospective review of infants with biliary atresia splenic malformation (BASM). We found that 56 infants (10.2%) met the criteria for inclusion from a series of 548 infants (from January 1977 to December 2004). Syndromic infants were more likely to be female (P = .04) and to have a higher incidence of antenatal pathology (specifically maternal diabetes; 12.5% vs 1.2%; P < .0001). Situs inversus was noted in 21 (37%) and cardiac abnormalities in 25 (45%) infants. There were no differences in liver histology (eg, degree of liver fibrosis) or in the HLA genotype between BASM and nonsyndromic infants. Five-year and 10-year estimated native liver survival were 46% and 32%, respectively. There were 7 long-term survivors with their native liver and a follow-up of more than 10 years; all were anicteric. BASM is a distinct subgroup, with an implied onset during the embryological phase of organ development.

Biliary atresia

Biliary atresia (BA) is a rare disease characterised by a biliary obstruction of unknown origin that presents in the neonatal period. It is the most frequent surgical cause of cholestatic jaundice in this age group. BA occurs in approximately 1/18,000 live births in Western Europe. In the world, the reported incidence varies from 5/100,000 to 32/100,000 live births, and is highest in Asia and the Pacific region. Females are affected slightly more often than males. The common histopathological picture is one of inflammatory damage to the intra- and extrahepatic bile ducts with sclerosis and narrowing or even obliteration of the biliary tree. Untreated, this condition leads to cirrhosis and death within the first years of life. BA is not known to be a hereditary condition. No primary medical treatment is relevant for the management of BA. Once BA suspected, surgical intervention (Kasai portoenterostomy) should be performed as soon as possible as operations performed early in life is more likely to be successful. Liver transplantation may be needed later if the Kasai operation fails to restore the biliary flow or if cirrhotic complications occur. At present, approximately 90% of BA patients survive and the majority have normal quality of life.

Biliary tract malformations

The biliary tree extends from the canals of Hering at the margin of the most peripheral portal tracts to the ampulla of Vater. Malformations occur at every level of this structure. Phenotypic features dominate present understanding of these malformations and of the disorders with which they are associated. Classifications of disease will likely shift from a phenotypic basis to a genotypic basis as genes implicated in biliary tree development and function are identified. Involvement of such genes in biliary tree disorders now considered inflammatory, such as extrahepatic biliary atresia, awaits study. The concept of "feeble cholangiocytes" postnatally susceptible to the effects of "toxic bile" is presented.

Biliary atresia revisited

Extrahepatic biliary atresia (EHBA) is an inflammatory fibrosing process affecting the extrahepatic and intrahepatic biliary tree resulting in fibrous obliteration of the extrahepatic biliary tract, ductopenia of intrahepatic bile ducts, and biliary cirrhosis. EHBA is divided into a correctable and a noncorrectable type with focal patency of the otherwise atretic biliary tree in the former and no patency of the biliary tree in the noncorrectable type. EHBA is divided in a fetal, prenatal or embryonic, and a more common, perinatal, acquired form. The symptoms of the former start shortly after birth and there is frequently an association with a variety of congenital anomalies. Children with the perinatal form become jaundiced several weeks after birth; no associated congenital anomalies are present. Morphologically, an inflammatory and fibrosing process of the extrahepatic biliary tree leads to complete lumenal obliteration. The liver is characterized by a nonspecific giant cell transformation, and portal expansion by fibrous connective tissue with marked ductular proliferation. With time, ductopenia and biliary cirrhosis develop. The diffential diagnosis with other conditions with similar microscopic patterns such as as alpha-1 antitrypsin deficiency, total parental nutrition, obstruction by a choledochal cyst, arteriohepatic dysplasia, familial progressive intrahepatic cholestasis, and alteration of the bile acid metabolism is discussed. In the fetal group, abnormalities in different genes seem to play a role; ductal plate malformation is another possibility. Different etiologies have been postulated in the perinatal form of EHBA: genetic susceptibility, vascular factors, toxins, and infections mainly by rotavirus and reovirus. The pathogenesis is complex. EHBA is a heterogenous disease, resulting from a combination of genetic factors, insults, and activation of different genetic and immunologic pathways. The treatment of EHBA is surgical, with anastomosis between the biliary tree and the intestine in the correctable type and a hepatic portoenterostomy (HPE) for the noncorrectable group. HPE is a temporizing treatment allowing the infant to develop and grow, followed in the majority of the patients by liver transplantation.

Biliary atresia

BA is a rare disease of unclear etiology; nevertheless, its impact in the field of pediatric hepatology is significant. It is the most common surgically correctable cause of neonatal cholestasis and is the most common pediatric disease referred for liver transplantation. Little progress has been made with regard to improving outcome or understanding its pathogenesis in the past decade. Fortunately, however, a national, government-sponsored collaborative endeavor has begun that will hopefully make a significant impact upon the progress of designing new treatments for BA and develop a better understanding of its pathogenesis.

North American Indian cirrhosis in children: a review of 30 cases

BACKGROUND

North American Indian childhood cirrhosis (NAIC) is a distinct, rapidly evolving form of familial cholestasis found in aboriginal children from northwestern Quebec. This is a retrospective review of the 30 patients treated in Quebec since the discovery of NAIC in 1970.

METHODS

The clinical records and histologic samples from 30 patients were reviewed. Extensive metabolic, biochemical, viral, genetic, and radiologic studies were performed in most patients.

RESULTS

Genetic analysis suggests autosomal recessive inheritance and a carrier frequency of 10% in this population. Gene mapping studies showed that the NAIC gene is located on chromosome 16q22. Typically, patients have neonatal cholestatic jaundice (70%) or hepatosplenomegaly (20%) with resolution of clinical jaundice by age 1 year but persistent direct hyperbilirubinemia. Portal hypertension was documented in 29 patients (91%). Variceal bleeding (15 patients, 50%) occurred as early as age 10 months. Surgical portosystemic shunting was performed in 13 of these 15 patients (87%); 4 (31%) rebled after 1 to 5 years. Fourteen patients died (47%). In 10 (71%), liver disease was the cause. Four children died of liver failure before liver transplantation became available. In transplanted livers, no recurrence of NAIC was observed after 1 to 10 years. Recognized infectious, metabolic, toxic, autoimmune, and obstructive causes of cirrhosis have been eliminated. The histologic features of NAIC show early bile duct proliferation and rapid development of portal fibrosis and biliary cirrhosis, suggesting a cholangiopathic phenomenon.

CONCLUSION

Together with gene mapping studies showing that the NAIC gene is different from those of other familial cholestases, these observations suggest that NAIC is a distinct entity that could be classified as "progressive familial cholangiopathy."

Epidemiology of biliary atresia in France: a national study 1986-96

BACKGROUND/AIMS

The reported incidence of biliary atresia varies from 5 to 32/100000 live births. The existence of seasonality and/or clustering is controversial. Based on a large population analysis, we examined the incidence of biliary atresia in France, and the space-time distribution of cases.

METHODS

All patients with biliary atresia living in France and born in the years 1986-96 were recorded. Geographic distribution, seasonality, time clustering and space-time clustering were analysed. Statistical analysis used the Chi square test, the Spearman nonparametric correlation test, the Walter and Elwood test for seasonality of events and Knox analysis for time and space-time clustering.

RESULTS

We identified 461 patients: 421 born in metropolitan France (incidence 5.12 [4.63-5.61]/100000 live births), and 40 born in overseas territories. No significant regional variation in incidence was found in metropolitan France, while the incidence was higher in French Polynesia (incidence 29.4 [15.4-43.3]/100000 live births) (p<0.001). Seasonality, time-clustering and time-space clustering could not be demonstrated.

CONCLUSIONS

1) The incidence of BA was 5.7-fold higher in Polynesia than in metropolitan France. 2) Neither seasonal variation in incidence nor clustering was identified.

Epidemiology of biliary atresia: a population-based study

OBJECTIVE

Biliary atresia is the leading cause of extrahepatic obstructive jaundice in the newborn and is the single most frequent indication for liver transplantation in children. The cause of biliary atresia is unknown, although several mechanisms have been postulated to explain the inflammatory process that obliterates the bile ducts. Most interest has been directed toward viral infections. Information about the epidemiologic characteristics of biliary atresia in well-defined populations is lacking but is essential for developing and addressing hypotheses of causation for the disease.

METHODS

Infants with biliary atresia were identified in metropolitan Atlanta from 1968 through 1993 by a population-based birth defects surveillance system that ascertains infants with serious birth defects in the first year of life using active case ascertainment. Birth prevalence rates were analyzed for spatial and temporal clustering and effects attributable to county of residence, sex, race, maternal age, parity, and birth weight. Logistic regression was used to study the independent effects of the risk factors and to look for interactions.

RESULTS

Fifty-seven infants with biliary atresia were identified, for a rate of 0.73 per 10,000 live births. There was significant seasonal clustering of the disease, with rates three times higher from December through March compared with rates from April through July. Rates were significantly higher among nonwhite infants compared with white infants (0.96 vs 0.44 per 10,000 live births) and infants born at term with low birth weights (<2500 g) compared with infants born at term with normal birth weights (> or = 2500 g) (2.62 vs 0.75 per 10,000 live births).

CONCLUSIONS

Our study is the first in the United States to describe the epidemiologic characteristics of biliary atresia using a population-based approach. The demonstration of significant seasonal clustering provides support for theories that biliary atresia may be caused by environmental exposure (consistent with a viral cause) during the perinatal period.

Electron microscopic study of the liver with biliary atresia and neonatal hepatitis

Eleven cases of biliary atresia (BA) and eight of neonatal hepatitis (NH) were studied, using transmission electron microscopy, to document their different ultrastructural characteristics and to elucidate the possible pathogenesis of biliary atresia. Among 30 consecutive liver biopsies obtained from 19 infants with BA or NH, 21 specimens composed (13 BA, 8 NH) were examined ultrastructurally. The electron microscopic features of NH (patients' age range, 35 to 60 days) were (1) giant hepatocytic transformation with scattered areas of dilated endoplasmic reticulum, indicative of intracytoplasmic degeneration, (2) frequent cytoplasmic biliary necrosis, and (3) relatively intact microvilli in most bile canaliculi, which contained some hepatocytic cytoplasmic fragments. These features strongly suggest that the main pathological process in NH is hepatocellular injury rather than bile duct damage. In contrast, all cases with BA (age range, 27 to 130 days) demonstrated (1) marked hepatocellular cholestasis associated with many lysosomes and myelin figures, (2) marked loss of bile canalicular microvilli, (3) degenerated bile ductular cells containing bile pigments, and (4) periductal inflammatory fibrosis. These features suggest that the main pathological process in BA involves the biliary system. A few viral inclusions were observed in two cases with BA, which suggests that viral infection is a potential cause. In two BA cases (aged 40 and 43 days at the time of first biopsy), the ultrastructural findings essentially were the same as those of NH, and follow-up biopsy specimens (at 48 and 94 days) showed findings consistent with BA. Such results support Landing's hypothesis that BA and NH are different manifestations of a single pathological process.

Biliary tract disease in children

This article discusses congenital and acquired disorders of the bile ducts and gallbladder in infants and children. Problems, such as extrahepatic biliary atresia, that are unique to infants are covered as well as distinctive aspects of hepatobiliary disease in older children. Biliary tract disease in the fetus and neonate presents an important challenge in that not only is hepatic structure and function disturbed but also the process of normal development may be retarded or altered by the disease process.