Biliary atresia: does ethnicity matter?

Congenital aflatoxicosis, mal-detoxification genomics & ontogeny trigger immune-mediated Kotb disease biliary atresia variant: SANRA compliant review

Biliary atresia (BA) is the most common indication for pediatric liver transplantation. We describe The BA variant: Kotb disease. Liver tissue in the Kotb disease BA is massively damaged by congenital aflatoxicosis resulting in inflammation, adhesions, fibrosis, bile duct proliferation, scarring, cholestasis, focal syncytial giant cell transformation, and typical immune response involving infiltration by CD4+, CD8+, CD68+, CD14+, neutrophil infiltration, neutrophil elastase spill, heavy loads of aflatoxin B1, accelerated cirrhosis, disruption of p53 and GSTPi, and have null glutathione S transferase M1 (GSTM1). All their mothers are heterozygous for GSTM1. This inability to detoxify aflatoxicosis results in progressive inflammatory adhesions and obliterative cholangiopathy early in life. The typical disruption of both p53 and GSTPi causes loss of fidelity of hepatic regeneration. Hence, regeneration in Kotb disease BA typically promotes accelerated cirrhosis. The immune response in Kotb disease BA is for damage control and initiation of regeneration, yet, this friendly fire incurs massive structural collateral damage. The Kotb disease BA is about actual ongoing hepatic entrapment of aflatoxins with lack of ability of safe disposal due to child detoxification-genomics disarray. The Kotb disease BA is a product of the interaction of persistent congenital aflatoxicosis, genetic lack of GSTM1 detoxification, ontogenically impaired activity of other hepatic detoxification, massive neutrophil-elastase, immune-induced damage, and disturbed regeneration. Ante-natal and neonatal screening for aflatoxicosis, avoiding cord milking, and stringent control of aflatoxicosis content of human, poultry and live-stock feeds might prove effective for prevention, prompt diagnosis and management based on our recent understanding of its patho-genomics.

High Mobility Group Box 1 Release by Cholangiocytes Governs Biliary Atresia Pathogenesis and Correlates With Increases in Afflicted Infants

BACKGROUND AND AIMS

Biliary atresia (BA) is a devastating cholangiopathy of infancy. Upon diagnosis, surgical reconstruction by Kasai hepatoportoenterostomy (HPE) restores biliary drainage in a subset of patients, but most patients develop fibrosis and progress to end-stage liver disease requiring liver transplantation for survival. In the murine model of BA, rhesus rotavirus (RRV) infection of newborn pups results in a cholangiopathy paralleling that of human BA. High-mobility group box 1 (HMGB1) is an important member of the danger-associated molecular patterns capable of mediating inflammation during infection-associated responses. In this study, we investigated the role of HMGB1 in BA pathogenesis.

APPROACH AND RESULTS

In cholangiocytes, RRV induced the expression and release of HMGB1 through the p38 mitogen-activated protein kinase signaling pathway, and inhibition of p38 blocked HMGB1 release. Treatment of cholangiocytes with ethyl pyruvate suppressed the release of HMGB1. Administration of glycyrrhizin in vivo decreased symptoms and increased survival in the murine model of BA. HMGB1 levels were measured in serum obtained from infants with BA enrolled in the PROBE and START studies conducted by the Childhood Liver Disease Research Network. High HMGB1 levels were found in a subset of patients at the time of HPE. These patients had higher bilirubin levels 3 months post-HPE and a lower survival of their native liver at 2 years.

CONCLUSIONS

These results suggest that HMGB1 plays a role in virus induced BA pathogenesis and could be a target for therapeutic interventions in a subset of patients with BA and high HMGB1.

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.

Innate Immunity and Pathogenesis of Biliary Atresia

Biliary atresia (BA) is a devastating fibro-inflammatory disease characterized by the obstruction of extrahepatic and intrahepatic bile ducts in infants that can have fatal consequences, when not treated in a timely manner. It is the most common indication of pediatric liver transplantation worldwide and the development of new therapies, to alleviate the need of surgical intervention, has been hindered due to its complexity and lack of understanding of the disease pathogenesis. For that reason, significant efforts have been made toward the development of experimental models and strategies to understand the etiology and disease mechanisms and to identify novel therapeutic targets. The only characterized model of BA, using a Rhesus Rotavirus Type A infection of newborn BALB/c mice, has enabled the identification of key cellular and molecular targets involved in epithelial injury and duct obstruction. However, the establishment of an unleashed chronic inflammation followed by a progressive pathological wound healing process remains poorly understood. Like T cells, macrophages can adopt different functional programs [pro-inflammatory (M1) and resolutive (M2) macrophages] and influence the surrounding cytokine environment and the cell response to injury. In this review, we provide an overview of the immunopathogenesis of BA, discuss the implication of innate immunity in the disease pathogenesis and highlight their suitability as therapeutic targets.

Genetics in biliary atresia

PURPOSE OF REVIEW

Biliary atresia is a poorly understood deadly disease. Genetic predisposition factors are suspected albeit not firmly established. This review summarizes recent evidence of genetic alterations in biliary atresia.

RECENT FINDINGS

Whole-genome association studies in biliary atresia patients identified four distinct predisposition loci with four different genes potentially involved in the disease occurrence. Variations in these genes were searched for, but none were found in patients with biliary atresia suggesting complex mechanisms.

SUMMARY

Despite decades since its description and decades of intensive researches, cause of biliary atresia disease remains enigmatic. The inheritance of biliary atresia is not Mendelian. Genetic predisposition factor is one of the explored fields to explain biliary atresia pathogenicity. Biliary atresia has been associated with several inborn syndromes, chromosome anomalies, and gene polymorphisms in specific populations. Four predisposition loci encompassing genes relevant to the disease have been identified, but no pathogenic variations were found in biliary atresia patients. Few reported cases of isolated biliary atresia manifestation in the context of known genetic diseases suggest coincidental findings. Alternatives to classic genetic alterations are proposed to explain genetic predisposition in biliary atresia including noncoding and epigenetic factors. Biliary atresia is most likely related to complex traits making its genetic exploration challenging.

Genetic investigation into an increased susceptibility to biliary atresia in an extended New Zealand Māori family

Background

Biliary atresia (BA), a fibrosing disorder of the developing biliary tract leading to liver failure in infancy, has an elevated incidence in indigenous New Zealand (NZ) Māori. We investigated a high rate of BA in a group of children (n = 12) belonging to a single Māori iwi (or ‘tribe’, related through a remote ancestor).

Methods

Population and geographical data was used to estimate the rate of BA in Māori sub-groups, and a pedigree linking most of the affected children was constructed from oral and documented history. Array genotyping was used to examine hypotheses about the inheritance of a possible genetic risk factor, and the history of the affected population, and Exome Sequencing to search for candidate genes.

Results

Most of these affected children (n = 7) link to a self-reported pedigree and carry a 50-fold increase in BA risk over unrelated Māori (χ² = 296P < 0.001, 95% CI 23–111). Genetic analysis using FEstim and SNP array genotypes revealed no evidence for elevated consanguinity between parents of affected children (FEstim: F (2,21) = 0.469, P > 0.63). Genome-wide quantitation of intervals of contiguous, homozygous-by-state markers reached a similar conclusion (F (2,399) = 1.99, P = 0.138). Principal component analysis and investigation with STRUCTURE found no evidence of increased allele frequency of either a recessive variant, or additive, low-risk variants due to reproductive isolation. To identify candidate causal factors, Exome Sequencing datasets were scrutinised for shared rare coding variants across 8 affected individuals. No rare, non-synonymous, phylogenetically conserved variants were common to 6 or more affected children.

Conclusion

The substantially elevated risk for development of BA in this subgroup could be mediated by genetic factors, but the iwi exhibits no properties indicative of recent or remote reproductive isolation. Resolution of any risk loci may rely on extensive genomic sequencing studies in this iwi or investigation of other mechnaisms such as copy number variation.

Electronic supplementary material

The online version of this article (10.1186/s12920-018-0440-0) contains supplementary material, which is available to authorized users.

Ethnic variation in the incidence of biliary atresia correlates with the frequency of the most prevalent haplotype in its population

The cause of biliary atresia (BA) remains an enigma. However, an ethnic diversity in the incidence of BA is so unique that anthropological approach may provide some etiopathogenetic implications in the disease mechanism. We previously reported that an association of maternal microchimerism (MMc) in BA and a significant compatibility of HLA-A between the patient with BA and their mother. Across the 10 countries (Japan, South Korea, Taiwan, Philippines, New Zealand (Maori population), UK, France, Germany, Norway, and Sweden), we determined the frequency of the most prevalent HLA haplotypes of each country from Allele Frequency Database and found that it was significantly correlated with the incidence of BA of the respective country (p = 0.0126). This observation better fits the MMc theory as an etiopathogenesis, that is, maternal effector cells are likely to migrate into the fetus in a relatively homogenous population and may damage the developing bile duct structure and portal vein endothelium, depending on materno-fetal tolerance and immunity.

Risk Estimation for Biliary Atresia in Patients with Neonatal Cholestasis: Development and Validation of a Risk Score

Purpose To develop and validate a scoring system based on clinical and imaging features to predict the risk for biliary atresia in patients with neonatal cholestasis. Materials and Methods Patients with neonatal cholestasis who underwent both ultrasonography (US) and hepatobiliary scintigraphy (n = 480) were retrospectively identified from two tertiary referral hospitals from January 2000 to February 2017. Patients from one hospital were classified as the derivation cohort (n = 371), and those from the other hospital were classified as the validation cohort (n = 109). Clinical and imaging features associated with biliary atresia were assessed. Histopathologic or intraoperative cholangiographic findings served as the reference standard for biliary atresia. A prediction model was developed by using logistic regression and was then transformed into a scoring system. The scoring system was internally and externally validated. Results Among the 371 patients in the derivation cohort, 97 (26.15%) had biliary atresia. A scoring system was constructed with the following variables: full-term birth, presence of the triangular cord sign at US, abnormal gallbladder morphology at US, and failure of radioisotope excretion to the small bowel at hepatobiliary scintigraphy. The maximum possible score with this system is 7 points. This system enabled differentiation of biliary atresia in the derivation cohort (C statistic, 0.981; 95% confidence interval [CI]: 0.970, 0.992) and the validation cohort (C statistic, 0.995; 95% CI: 0.987, 1.000). The risk score also showed good calibration in both the derivation and the validation cohorts (P = .328 and P = .281, respectively). Conclusion A simple scoring system combining clinical and imaging features can help accurately estimate the risk for biliary atresia in patients with neonatal cholestasis.

Biliary atresia: Clinical advances and perspectives

Biliary atresia (BA) is a rare and severe inflammatory and obliterative cholangiopathy that affects both extra- and intrahepatic bile ducts. BA symptoms occur shortly after birth with jaundice, pale stools and dark urines. The prognosis of BA has dramatically changed in the last decades: before the Kasai operation most BA patients died, while nowadays with the sequential treatment with Kasai operation±liver transplantation BA patient survival is close to 90%. Early diagnosis is very important since the chances of success of the Kasai procedure decrease with time. The causes of BA remain actually unknown but several mechanisms including genetic and immune dysregulation may probably lead to the obliterative cholangiopathy. Current research focuses on the identification of blood or liver factors linked to the pathogenesis of BA that could become therapeutic targets and avoid the need for liver transplantation. No similar disease leading to total obstruction of the biliary tree exists in older children or adults. But understanding the physiopathology of BA may highlight the mechanisms of other destructive cholangiopathies, such as sclerosing cholangitis.

Reduction of the ages at diagnosis and operation of biliary atresia in Taiwan: A 15-year population-based cohort study

AIM: To describe the ages at diagnosis and operation of biliary atresia (BA) and its incidence over a 15-year period in Taiwan.

METHODS: This was a population-based cohort study. BA cases were identified from the Taiwan National Health Insurance Research Database based on the International Classification of Diseases, Ninth Revision (ICD-9) code of BA 751.61 plus Kasai operation (ICD-9 procedure code 51.37) or liver transplantation (LT, ICD-9 procedure code 50.5). The patients’ characteristics including sex, age at diagnosis, age at receiving Kasai operation and age at receiving LT were compared among three birth cohorts: (1) 1997 to 2001; (2) 2002 to 2006; and (3) 2007 to 2011.

RESULTS: There were a total of 540 BA cases (275 females) with an incidence of 1.62 per 10000 live births. No seasonality of BA was noted. The mean ages at diagnosis of three cohorts were 57.9, 55.6 and 52.6 d. A linear regression model demonstrated a decreasing trend of the mean age at diagnosis (1.27 d per year). The proportion of BA cases that received the Kasai operation within 60 d of age increased from 76% to 81%. A total of 189 (35%) BA patients underwent LT. The mean age at LT was reduced from 3-year-old to 1-year-old. The rates of LT were 25.6% and 32.3% in patients who received the Kasai operation within 60 d or after 60 d of age, respectively. All patients who did not undergo a Kasai operation eventually required LT.

CONCLUSION: The ages at diagnosis and operation in BA cases have decreased over time. Kasai operation performed at younger age reduces the need for LT. The incidence of BA in Taiwan fluctuates, but without certain trend.