Update on investigations pertaining to the pathogenesis of biliary atresia

Diseases of bile duct in children

Several diseases originate from bile duct pathology. Despite studies on these diseases, certain etiologies of some of them still cannot be concluded. The most common disease of the bile duct in newborns is biliary atresia, whose prognosis varies according to the age of surgical correction. Other diseases such as Alagille syndrome, inspissated bile duct syndrome, and choledochal cysts are also time-sensitive because they can cause severe liver damage due to obstruction. The majority of these diseases present with cholestatic jaundice in the newborn or infant period, which is quite difficult to differentiate regarding clinical acumen and initial investigations. Intraoperative cholangiography is potentially necessary to make an accurate diagnosis, and further treatment will be performed synchronously or planned as findings suggest. This article provides a concise review of bile duct diseases, with interesting cases.

Toxins and Biliary Atresia: Is Karenia Brevis (Red Tide) The Culprit?

OBJECTIVE

The study objective was to evaluate the association between Karenia brevis (K. brevis) exposure during pregnancy and the prevalence of biliary atresia (BA) in offspring.

STUDY DESIGN

This was a hospital-based, case-control study in which cases were infants diagnosed with BA at Johns Hopkins All Children's Hospital from October 2001 to December 2019. Cases were matched 1:4 by age to controls who were randomly selected from a pool of healthy infants hospitalized during the study period for common pediatric diagnoses. Infants were excluded if they had congenital anomalies and/or were non-Florida residents. Gestational K. brevis exposure levels (cells/liter) were determined from Florida Fish and Wildlife Conservation Commission exposure data at 10- and 50 mile radii from the mother's zip code of residence. Multivariable conditional logistic regression determined odds of BA in offspring in relation to maternal gestational K. brevis exposure adjusted for infant sex, race/ethnicity, coastal residence, and seasonality.

RESULTS

Of 38 cases and 152 controls, no significant inter-group differences were observed for infant race/ethnicity, season of birth, or coastal residence. Median gestational exposure at the 10 mile radius was 0 cells/liter in both groups. A greater proportion of cases had no gestational K. brevis exposure (63.2 %, n = 24) in comparison to controls (37.5 %, n = 57; p = .04) at a 10 mile radius. At a 50 mile radius, cases had a peak median exposure at 6 months of gestation compared to controls' peak at 9 months. After adjustment for sex, seasonality, race/ethnicity, and coastal residence, there was no significant association between BA and maximum K. brevis exposure per trimester of pregnancy observed at a 10- or 50 mile radius.

CONCLUSION

In this matched case-control study, we observed no association between gestational K. brevis (cells/liter) exposure at a 10- or 50 mile radius from maternal zip code of residence and BA in offspring.

Pediatric Cholestatic Diseases: Common and Unique Pathogenic Mechanisms

Cholestasis is the predominate feature of many pediatric hepatobiliary diseases. The physiologic flow of bile requires multiple complex processes working in concert. Bile acid (BA) synthesis and excretion, the formation and flow of bile, and the enterohepatic reuptake of BAs all function to maintain the circulation of BAs, a key molecule in lipid digestion, metabolic and cellular signaling, and, as discussed in the review, a crucial mediator in the pathogenesis of cholestasis. Disruption of one or several of these steps can result in the accumulation of toxic BAs in bile ducts and hepatocytes leading to inflammation, fibrosis, and, over time, biliary and hepatic cirrhosis. Biliary atresia, progressive familial intrahepatic cholestasis, primary sclerosing cholangitis, and Alagille syndrome are four of the most common pediatric cholestatic conditions. Through understanding the commonalities and differences in these diseases, the important cellular mechanistic underpinnings of cholestasis can be greater appreciated.

Cytomegalovirus in biliary atresia is associated with increased pretransplant death, but not decreased native liver survival

BACKGROUND

Biliary atresia (BA) is likely caused by a common phenotypic response to various triggers; one proposed trigger, cytomegalovirus (CMV), may lead to worse outcomes. The aim of this study was to determine the severity of disease and pretransplant outcomes of infants with BA, who have evidence of CMV (CMV+) at diagnosis compared with CMV-negative (CMV-) infants.

METHODS

The study used data and biospecimens from the Childhood Liver Disease Research Network PROBE study of cholestatic infants. Plasma obtained at the time of hepatic portoenterostomy (HPE) of 249 infants with BA was tested for CMV by DNA-PCR and CMV-IgM. Comparisons between CMV+ and CMV- infants were made using Wilcoxon rank sum, Student t test, chi-square, or Fisher exact test. Native liver survival (NLS) outcomes were analyzed using Kaplan-Meier and Cox regression adjusting for age at HPE; pretransplant patient survival outcomes were analyzed using a competing risk model and adjusting for age at HPE.

RESULTS

CMV+ infants (n = 29, 12%) underwent HPE later (67.8±13.6 d vs. 55.1±18.5 d, p = 0.0005) and had higher baseline alkaline phosphatase and aminotransferases. There was no difference between groups in jaundice clearance or NLS. The subdistribution HR of pretransplant death for CMV+ infants adjusted for age at HPE was 3.8 (p = 0.034).

CONCLUSIONS

CMV infection at the time of HPE in infants with BA is not associated with worse NLS despite the association with worse liver injury, older age at HPE, and increased risk of pretransplant death adjusted for age at HPE. Continued evaluation of the consequences of CMV infection and the effects of antiviral treatment should be explored.

Incidence of Isolated Biliary Atresia during the COVID Lockdown in Europe: Results from a Collaborative Project by RARE-Liver

BACKGROUND

Biliary atresia (BA) is a rare cholangiopathy where one of the proposed aetiological mechanisms is an infectious viral trigger. Coronavirus disease-19 (COVID) lockdown restrictions were implemented to reduce the transmission of infections. Strictness of lockdown varied across European countries. This study aimed to investigate if there was an association between strictness of lockdown and change in isolated BA (IBA) incidence in Europe.

METHODS

We approached European centres involved in the European Reference Network RARE-LIVER. We included IBA patients born between 2015 and June 2020. We calculated the number of IBA patients born per centre per month. The Stringency Index (SI) was used as lockdown strictness indicator. The association between percentage change of mean number of IBA patients born per month and the SI was assessed.

RESULTS

We included 412 IBA patients from thirteen different centres. The median number of patients per month did not change: 6 (1-15) pre-lockdown and 7 (6-9) during lockdown (p = 0.34). There was an inverse association between SI and percentage change in IBA (B = -0.73, p = 0.03). Median age at Kasai portoenterostomy (days) did not differ between time periods (51 (9-179) vs. 53 (19-126), p = 0.73).

CONCLUSION

In this European study, a stricter COVID-lockdown was seemingly accompanied by a simultaneous larger decrease in the number of IBA patients born per month in the lockdown. Results should be interpreted with caution due to the assumptions and limitations of the analysis.

Identifying and validating molecular subtypes of biliary atresia using multiple high-throughput data integration analysis

Background

Biliary atresia (BA) is the most common form of severe neonatal obstructive jaundice. The etiology and pathogenesis of BA are multifactorial, and different factors may interact to produce heterogeneous pathological features and clinical outcomes. Despite different pathological features, all patients received the same treatment strategy. This study performed integrative clustering analysis based on multiple high-throughput datasets to identify the molecular subtypes of BA and provide a new treatment strategy for personalized treatment of the different subtypes of BA.

Methods

The RNA sequence dataset GSE122340 in the Gene Expression Omnibus (GEO) database was downloaded; 31 BA and 20 control normal liver tissues were collected at our center for transcriptome sequencing, and clinical and follow-up data of BA patients were available. Molecular subtypes were identified using integrated unsupervised cluster analysis involving gene expression, biliary fibrosis, and immune enrichment scores based on the transcriptome dataset, and the results were validated using independent datasets.

Results

Based on the results of the integrated unsupervised clustering analysis, four molecular subtypes were identified: autoimmune, inflammatory, virus infection-related, and oxidative stress. The autoimmune subtype with a moderate prognosis was dominated by autoimmune responses and morphogenesis, such as the Fc-gamma receptor and Wnt signaling pathway. The biological process of the inflammatory subtype was mainly the inflammatory response, with the best prognosis, youngest age at surgery, and lowest liver stiffness. The virus infection-related subtype had the worst prognosis and was enriched for a variety of biological processes such as viral infection, immunity, anatomical morphogenesis, and epithelial mesenchymal transition. The oxidative stress subtype was characterized by the activation of oxidative stress and various metabolic pathways and had a poor prognosis. The above results were verified independently in the validation sets.

Conclusions

This study identified four molecular subtypes of BA with distinct prognosis and biological processes. According to the pathological characteristics of the different subtypes, individualized perioperative and preoperative treatment may be a new strategy to improve the prognosis of BA.

mRNA and lncRNA expression profiles of liver tissues in children with biliary atresia

Progressive liver fibrosis is the most common phenotype in biliary atresia (BA). A number of pathways contribute to the fibrosis process so comprehensive understanding the mechanisms of liver fibrosis in BA will pave the way to improve patient's outcome after operation. In this study, the differentially expressed profiles of mRNAs and long non-coding RNAs from BA and choledochal cyst (CC) liver tissues were investigated and analyzed, which may provide potential clues to clarify hepatofibrosis mechanism in BA. A total of two BA and two CC liver tissue specimens were collected, the expression level of mRNAs and lncRNAs was detected by RNA sequencing. Differentially expressed mRNAs (DEmRNAs) were functionally annotated and protein-protein interaction networks (PPI) was established to predict the biological roles and interactive relationships. Differentially expressed lncRNAs (DElncRNAs) nearby targeted DEmRNA network and DElncRNA-DEmRNA co-expression network were constructed to further explore the roles of DElncRNAs in BA pathogenesis. The expression profiles of significant DEmRNAs were validated in Gene Expression Omnibus database. A total of 2,086 DEmRNAs and 184 DElncRNAs between BA and CC liver tissues were obtained. DEmRNAs were enriched in 521 Gene Ontology terms and 71 Kyoto Encyclopedia of Genes and Genomes terms which were mainly biological processes and metabolic pathways related to immune response and inflammatory response. A total of five hub proteins (TYRO protein tyrosine kinase binding protein, C-X-C motif chemokine ligand 8, pleckstrin, Toll-like receptor 8 and C-C motif chemokine receptor 5) were found in the PPI networks. A total of 31 DElncRNA-nearby-targeted DEmRNA pairs and 2,337 DElncRNA-DEmRNA co-expression pairs were obtained. The expression of DEmRNAs obtained from RNA sequencing were verified in GSE46960 dataset, generally. The present study identified key genes and lncRNAs participated in BA associated liver fibrosis, which may present a new avenue for understanding the patho-mechanism for hepatic fibrosis in BA.

Biliary Atresia in Children: Update on Disease Mechanism, Therapies, and Patient Outcomes

Biliary atresia is a rare disease but remains the most common indication for pediatric liver transplantation as there are no effective medical therapies to slow progression after diagnosis. Variable contribution of genetic, immune, and environmental factors contributes to disease heterogeneity among patients with biliary atresia. Developing a deeper understanding of the disease mechanism will help to develop targeted medical therapies and improve patient outcomes.

The Bioinformatic Study Uncovers Probable Critical Genes Involved in the Pathophysiology of Biliary Atresia

Background

Biliary atresia (BA) is an uncommon illness that causes the bile ducts outside and within the liver to become clogged in babies. If left untreated, the cholestasis causes increasing conjugated hyperbilirubinemia, cirrhosis, and hepatic failure. BA has a complicated aetiology, and the mechanisms that drive its development are unknown. The objective of this study was to show the role of probable critical genes involved in the pathophysiology of biliary atresia.

Methods

We utilised the public Gene Expression Omnibus (GEO) microarray expression profiling dataset GSE46960 to find differentially expressed genes (DEGs) in 64 biliary atresia newborns, 14 infants with various causes of intrahepatic cholestasis, and 7 deceased-donor children as control subjects in our study. The relevant information was looked into. The important modules were identified after functional enrichment, GO and KEGG pathway analyses, protein-protein interaction (PPI) network analyses, and GSEA analysis.

Results

The differential expression analysis revealed a total of 22 elevated genes. To further understand the biological activities of the DEGs, we run functional enrichment analyses on them. Meanwhile, KEGG analysis has revealed significant enrichment of pathways involved in activating cross-talking with inflammation and fibrosis in BA. SERPINE1, THBS1, CCL2, MMP7, CXCL8, EPCAM, VCAN, ITGA2, AREG, and HAS2, which may play a significant regulatory role in the pathogenesis of BA, were identified by PPI studies.

Conclusion

Our findings suggested 10 hub genes and probable mechanisms of BA in the current study through bioinformatic analysis.

Ultrasound elastography in the diagnosis of biliary atresia in pediatric surgery: a systematic review and meta-analysis of diagnostic test

BACKGROUND

Biliary atresia (BA) is one of the most fatal hepatobiliary diseases in infants and young children, and is easy to cause obstructive jaundice in infants and children, and liver transplantation in children. BA and infantile hepatitis syndrome are the main causes of cholestatic jaundice. The early clinical manifestations are extremely similar, and timely identification is difficult. Therefore, early and differential diagnosis of BA is crucial. At present, there are many imaging diagnosis methods for BA, such as ultrasound examination and nuclear magnetic resonance. Ultrasound elastography (USE) is the most popular method. However, the application of USE in BA is still in the exploratory stage.

METHODS

PubMed, Web of Science, Embase, Cochrane Library, and other databases were searched for articles on USE diagnosis of pediatric surgical BA. Later, the articles were screened, and the included articles should meet the following requirements: the research objects were children with BA; the intervention measures were USE diagnosis; the control group was diagnosed by other methods than USE. RevMan5.3 was adopted for quality assessment, and forest maps and summary receiver operating characteristic (SROC) curves were constructed.

RESULTS

Finally, seven articles covering 490 patients were included. There were 120 patients in the control group. The included articles showed good quality and there was no obvious bias. The area under the SROC curve (AUC) for USE diagnosis of BA was 0.93, the sensitivity was 0.93 (95% CI: 0.72-1.00), and the specificity was 0.95 (95% CI: 0.74-1.00).

DISCUSSION

USE showed high diagnostic value for pediatric surgical biliary tract closure.

Update on Etiology and Pathogenesis of Biliary Atresia

Biliary atresia is a rare inflammatory sclerosing obstructive cholangiopathy that initiates in infancy as complete choledochal blockage and progresses to the involvement of intrahepatic biliary epithelium. Growing evidence shows that biliary atresia is not a single entity with a single etiology but a phenotype resulting from multifactorial events whose common path is obliterative cholangiopathy. The etiology of biliary atresia has been explained as resulting from genetic variants, toxins, viral infection, chronic inflammation or bile duct lesions mediated by autoimmunity, abnormalities in the development of the bile ducts, and defects in embryogenesis, abnormal fetal or prenatal circulation and susceptibility factors. It is increasingly evident that the genetic and epigenetic predisposition combined with the environmental factors to which the mother is exposed are potential triggers for biliary atresia. There is also an indication that a progressive thickening of the arterial middle layer occurs in this disease, suggestive of vascular remodeling and disappearance of the interlobular bile ducts. It is suggested that the hypoxia/ischemia process can affect portal structures in biliary atresia and is associated with both the extent of biliary proliferation and the thickening of the medial layer.

Efficacy and tolerance of enteral nutrition in children with biliary atresia awaiting liver transplantation

OBJECTIVES

Malnutrition is common in children with biliary atresia (BA) awaiting liver transplantation (LT). Few studies have evaluated the effectiveness of enteral nutrition (EN) in these patients. The objective of this work was to assess the efficacy and tolerance of EN in children with BA awaiting LT.

METHODS

A total of 31 patients with BA followed between 1995 and 2018 were retrospectively included. Anthropometric indicators (weight, length, and head circumference) and adverse effects of EN were noted at the start (T0) and the end (T1) of EN. The z-scores for anthropometric indicators were compared between T0 and T1.

RESULTS

The median age at T0 was 7 months (interquartile range [IQR] 5-9), and the median duration of EN was 9 months (IQR 3-17). The z-scores for anthropometric variables improved from T0 to T1: -1.6 (IQR -2.5 to -1.0) to -0.5 (IQR -1.8 to 0.3) for median weight for age; -1.3 (IQR -2.4 to 0) to -0.4 (IQR -2.0 to 0.7) for length for age; -0.9 (IQR -2.3 to -0.3) to -0.3 (IQR -1.2 to 0.1) for weight for length; and -1.2 (IQR -2.1 to -0.6) to -0.2 (IQR -1.6 to 0.4) for body mass index (p < 0.05 for all comparisons). Nearly all (94%) of the patients had a weight-for-length z-score > -2 at the end of EN; 23% had adverse effects and 10% had complications leading to the cessation of EN.

CONCLUSION

EN is effective and well tolerated in infants with BA awaiting LT.

A joint transcriptional regulatory network and protein activity inference analysis identifies clinically associated master regulators for biliary atresia

Biliary atresia (BA) is a devastating cholangiopathy in neonate. Transcription factors (TFs), a type of master regulators in biological processes and diseases, have been implicated in pathogenesis of BA. However, a global view of TFs and how they link to clinical presentations remain explored. Here, we perform a joint transcriptional regulatory network and protein activity inference analysis in order to investigate transcription factor activity in BA. By integration of three independent human BA liver transcriptome datasets, we identify 22 common master regulators, with 14 activated- and 8 repressed TFs. Gene targets of activated TFs are enriched in biological processes of SMAD, NF-kappaB and TGF-beta, while those of repressed TFs are related to lipid metabolism. Mining the clinical association of TFs, we identify inflammation-, fibrosis- and survival associated TFs. In particular, ZNF14 is predictive of poor survival and advanced live fibrosis. Supporting this observation, ZNF14 is positively correlated with T helper cells, cholangiocytes and hepatic stellate cells. In sum, our analysis reveals key clinically associated master regulators for BA.

Epidemiological characteristics and risk factors of biliary atresia: a case-control study

OBJECTIVES

Biliary atresia (BA) is regarded as a serious neonatal hepatobiliary disease, and its aetiology and pathogenesis remain unclear. Epidemiological studies are limited, especially for the data from China. This study aims to explore risk factors of BA and provide new evidence to improve understanding of its aetiology.

DESIGN

This is a case-control study from 1 January 2015 to 31 December 2016.

SETTING

Cases were consecutively recruited from an urban tertiary care academic children's hospital in Shanghai, China, while the controls were recruited from a community hospital in Shanghai through a random sampling system.

PARTICIPANTS

721 patients suspected for BA who planned to take the diagnostic surgery were enrolled preoperatively. 613 were diagnosed with BA and recruited into the case group. Meanwhile, 688 infants without any observed major congenital anomalies or jaundice were enrolled. Finally, 594 valid questionnaires from the case group and 681 from the control group were obtained.

PRIMARY AND SECONDARY OUTCOME MEASURES

Standardised questionnaires were used for data collection. Multivariate logistic regression analysis was performed to evaluate associations reported as ORs and precision, by adjusting covariates.

RESULTS

Anxiety or stress during pregnancy was strongly associated with increased risk of BA (OR 8.36 (95% CI: 4.08 to 17.15); p<0.001), respectively. Lower birth weight, fathers from ethnic minorities of China, older age of fathers, lower income of parents, and exposure to infection, diseases and medication during pregnancy all made differences.

CONCLUSIONS

Social factors including the educational and economic background and its related anxiety and stress during pregnancy might be noticed in the occurrence of BA. Maternal infections during pregnancy in the prevalence of BA were demonstrated.

TRIAL REGISTRATION NUMBER

ChiCTR-IPR-15005885.

Adjuvant Therapy with Budesonide Post-Kasai Reduces the Need for Liver Transplantation in Biliary Atresia

Based on the hypothesis that autoimmunological factors coregulate the pathomechanism in biliary atresia (BA), adjuvant therapy with steroids has become routine, although its efficacy has never been proven. In 2010, a study on the advantages of budesonide compared to prednisolone in autoimmune hepatitis gave rise to experimental therapy using budesonide as an adjuvant BA treatment. Ninety-five BA patients prospectively received a budesonide 2 mg/dose rectal foam daily for three months (SG). A case-matched control group (CG: 81) was retrospectively recruited. The outcome measures were survival with native liver (SNL), determined at six months and two years after the Kasai procedure. The follow-up rate was 100%. At six months, SNL was statistically not different but became so after two years (SG: 54%; CG: 32%; p < 0.001). No steroid-related side effects were observed, except for eight patients with finally caught-up growth retardation. This study demonstrates for the first time a significantly longer survival with native liver in patients with BA after adjuvant therapy. However, indication, dosage, and duration of any budesonide application is not given in neonates with BA. Hence, we suggest extending the postoperative use of budesonide in a multicenter observational study with a clearly defined follow-up protocol, particularly in terms of potentially underestimated side effects.

Biliary Atresia: Clinical Phenotypes and Aetiological Heterogeneity

Biliary atresia (BA) is an obliterative condition of the biliary tract that presents with persistent jaundice and pale stools typically in the first few weeks of life. While this phenotypic signature may be broadly similar by the time of presentation, it is likely that this is only the final common pathway with a number of possible preceding causative factors and disparate pathogenic mechanisms-i.e., aetiological heterogeneity. Certainly, there are distinguishable variants which suggest a higher degree of aetiological homogeneity such as the syndromic variants of biliary atresia splenic malformation or cat-eye syndrome, which implicate an early developmental mechanism. In others, the presence of synchronous viral infection also make this plausible as an aetiological agent though it is likely that disease onset is from the perinatal period. In the majority of cases, currently termed isolated BA, there are still too few clues as to aetiology or indeed pathogenesis.

Environmental exposure as a risk-modifying factor in liver diseases: Knowns and unknowns

Liver diseases are considered to predominantly possess an inherited or xenobiotic etiology. However, inheritance drives the ability to appropriately adapt to environmental stressors, and disease is the culmination of a maladaptive response. Thus “pure” genetic and “pure” xenobiotic liver diseases are modified by each other and other factors, identified or unknown. The purpose of this review is to highlight the knowledgebase of environmental exposure as a potential risk modifying agent for the development of liver disease by other causes. This exercise is not to argue that all liver diseases have an environmental component, but to challenge the assumption that the current state of our knowledge is sufficient in all cases to conclusively dismiss this as a possibility. This review also discusses key new tools and approaches that will likely be critical to address this question in the future. Taken together, identifying the key gaps in our understanding is critical for the field to move forward, or at the very least to “know what we don't know.”

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.

Unique Cholangiocyte-Targeted IgM Autoantibodies Correlate With Poor Outcome in Biliary Atresia

BACKGROUND AND AIMS

The etiology of biliary atresia (BA) is not known and is likely multifactorial, including a genetic predisposition, a viral or environmental trigger, an aberrant autoimmune response targeting cholangiocytes, and unique susceptibilities of the neonatal bile ducts to injury. Damaged cholangiocytes may express neo self-antigens and elicit autoreactive T-cell-mediated inflammation and B-cell production of autoantibodies. The aim of this study was to discover autoantibodies in BA that correlated with outcomes.

APPROACH AND RESULTS

An autoantigen microarray encompassing approximately 9,500 autoantigens was used to screen for serum immunoglobulin M (IgM) and immunoglobulin G (IgG) autoantibodies in patients with BA or other liver disease controls. Validation of candidate autoantibodies by enzyme-linked immunosorbent assay on a second cohort of subjects (6-12 months following Kasai portoenterostomy) and correlations of autoantibodies with outcomes were performed (serum bilirubin levels and need for liver transplant in first 2 years of life). Mean anti-chitinase 3-like 1 (CHI3L1), anti-delta-like ligand (DLL-4), and antisurfactant protein D (SFTPD) IgM autoantibodies in BA were significantly higher compared with controls, and IgM autoantibody levels positively correlated with worse outcomes. Immunofluorescence revealed cholangiocyte-predominant expression of CHI3L1, DLL-4, and SFTPD. The humoral autoantibody response was associated with C3d complement activation and T-cell autoimmunity, based on detection of cholangiocyte-predominant C3d co-staining and peripheral blood autoreactive T cells specific to CHI3L1, DLL-4 and SFTPD, respectively.

CONCLUSIONS

BA is associated with cholangiocyte-predominant IgM autoantibodies in the first year after Kasai portoenterostomy. Anti-CHI3L1, anti-DLL-4, and anti-SFTPD IgM autoantibody correlations with worse outcomes and the detection of C3d on cholangioctyes and antigen-specific autoreactive T cells suggest that autoimmunity plays a role in the ongoing bile duct injury and progression of disease.

Study Protocol: Design and Implementation of the Pediatric Liver Transplantation Biobank

Background: Early treatment of neonatal biliary atresia (BA) and other end-stage liver diseases can delay or prevent the necessity of liver transplantation (LT). The establishment of a standardized clinical pediatric liver transplantation (PLT) biobank is the prerequisite for scientific research, which helps to provide a qualified sample resource platform for research. Methods: Following standardized procedures to establish biobanks, the operational processes and quality control system were formulated. Liver tissue, blood, and stool samples undergoing LT were regularly collected, managed, and stored. Systematic management was conducted in collected specimens and corresponding clinical information. Results: Since implementation in August 2018, we have enrolled 49 unique subjects (0-18 years of age); the biobank contains nearly 3000 biospecimen aliquots. The most common LT diagnosis is BA (61.23%). Conclusion: The establishment of this biobank is a valuable resource that incorporates detailed clinical and biological information. It will help accelerate the pace of PLT discovery research. ClinicalTrials.gov ID: NCT04477967.

Transcriptional profiling of pediatric cholestatic livers identifies three distinct macrophage populations

Background & aims

Limited understanding of the role for specific macrophage subsets in the pathogenesis of cholestatic liver injury is a barrier to advancing medical therapy. Macrophages have previously been implicated in both the mal-adaptive and protective responses in obstructive cholestasis. Recently two macrophage subsets were identified in non-diseased human liver; however, no studies to date fully define the heterogeneous macrophage subsets during the pathogenesis of cholestasis. Here, we aim to further characterize the transcriptional profile of macrophages in pediatric cholestatic liver disease.

Methods

We isolated live hepatic immune cells from patients with biliary atresia (BA), Alagille syndrome (ALGS), and non-cholestatic pediatric liver by fluorescence activated cell sorting. Through single-cell RNA sequencing analysis and immunofluorescence, we characterized cholestatic macrophages. We next compared the transcriptional profile of pediatric cholestatic and non-cholestatic macrophage populations to previously published data on normal adult hepatic macrophages.

Results

We identified 3 distinct macrophage populations across cholestatic liver samples and annotated them as lipid-associated macrophages, monocyte-like macrophages, and adaptive macrophages based on their transcriptional profile. Immunofluorescence of liver tissue using markers for each subset confirmed their presence across BA (n = 6) and ALGS (n = 6) patients. Cholestatic macrophages demonstrated reduced expression of immune regulatory genes as compared to normal hepatic macrophages and were distinct from macrophage populations defined in either healthy adult or pediatric non-cholestatic liver.

Conclusions

We are the first to perform single-cell RNA sequencing on human pediatric cholestatic liver and identified three macrophage subsets with distinct transcriptional signatures from healthy liver macrophages. Further analyses will identify similarities and differences in these macrophage sub-populations across etiologies of cholestatic liver disease. Taken together, these findings may allow for future development of targeted therapeutic strategies to reprogram macrophages to an immune regulatory phenotype and reduce cholestatic liver injury.

The Utility of Gallbladder Absence on Ultrasound for Children With Biliary Atresia

Background: Biliary Atresia (BA) is congenital condition, where infant intra- and extrahepatic bile ducts become obliterated, leading to cholestasis, and cirrhosis if untreated. This study aims to assess the predictive measure of absent gallbladder on ultrasounds (US) performed in infants with cholestasis for diagnosing BA. Method: After Institutional Review Board approval, retrospective chart reviews of 61 infants with cholestasis found 43 (70.5%) were diagnosed with BA. A pediatric radiologist provided interpretations of all ultrasounds in a blinded fashion. Statistical analysis was used to assess the utility of absence of gallbladder on US in predicting BA, confirmed intraoperatively. Results: Absent gallbladder on US predicts absent gallbladder with 77% accuracy, 92% sensitivity, 73% specificity, PPV 43%, and NPV 97% (P < 0.001, Fisher exact test). To diagnose BA, absent gallbladder on US has 66% accuracy, 53% sensitivity, 94% specificity, 96% PPV, and 46% NPV (P < 0.001, Fisher exact test). Conclusion: Sonographic gallbladder absence has high specificity and PPV, indicating utility for BA diagnosis; however, it is not useful for ruling out BA given its low sensitivity.

Recent developments in etiology and disease modeling of biliary atresia: a narrative review

Biliary atresia (BA) is a rare but severe fibroinflammatory disease of the extrahepatic and the intrahepatic bile ducts. Without prompt interventions, BA has fatal outcomes and is the most common indicator for pediatric liver transplantation (LTx). While the mainstay of treatment involves surgically correcting the extrahepatic biliary obstruction via Kasai hepato-portoenterostomy (KHPE), activation of a multitude of biological pathways and yet-to-be-determined etiology in BA continue to foster liver inflammation, cirrhosis and need for LTx. However, important caveats still exist in our understandings of the biliary pathophysiology, the rapidity of liver fibrosis and progression to liver failure, largely due to limited knowledge of the triggers of biliary injury and the inability to accurately model human BA. Although inconclusive, a large body of existing literature points to a potential viral infection in the early peri- or postnatal period as triggers of epithelial injury that perpetuates the downstream biliary disease. Further confounding this issue, are the lack of in-vivo and in-vitro models to efficiently recapitulate the cardinal features of BA, primarily liver fibrosis. To overcome these barriers in BA research, new directions in recent years have enabled (I) identification of additional triggers of biliary injury linked mostly to environmental toxins, (II) development of models to investigate liver fibrogenesis, and (III) translational research using patient-derived organoids. Here, we discuss recent advances that undoubtedly will stimulate future efforts investigating these new and exciting avenues towards mechanistic and drug discovery efforts and disease-preventive measures. The implications of these emerging scientific investigations and disease modeling in severe fibrosing cholangiopathies like BA are enormous and contribute substantially in our understandings of this rare but deadly disease. These findings are also expected to facilitate expeditious identification of translationally targetable pathways and bring us one step closer in treating an infant with BA, a population highly vulnerable to life-long liver related complications.

Can Free Carnitine or Bilirubin in Blood Be Used in Neonatal Screening for Biliary Atresia?

OBJECTIVE

 To investigate the efficiency of free carnitine, unconjugated bilirubin (UBIL), bilirubin monoglucuronide (BMG), and bilirubin diglucuronide (BDG) in dry blood spots (DBSs) measured using tandem mass spectrometry (MS/MS) for screening biliary atresia (BA).

MATERIALS AND METHODS

 All the patients with BA, residing in Shanghai, were collected from four different children's hospitals in Shanghai from January 1, 2015, to June 30, 2017. UBIL_MS, BMG, BDG, and free carnitine were measured in the DBS samples of 48 patients with BA, 10,008 pediatric patients, and 52,862 newborns using MS/MS. Conjugated bilirubin was measured by MS/MS (CB_MS) = BMG + BDG, and total bilirubin was measured by MS/MS (TB_MS) = UBIL_MS + CB_MS. Four hundred pediatric patients' direct bilirubin (DB) and total bilirubin (TB), measured by the clinical laboratory and MS/MS, were used as a control.

RESULTS

 The total number of births at the registered permanent residences in Shanghai was 233,000; among them, the occurrence of BA was in 33 patients in 2 years. Therefore, the incidence of BA in Shanghai was 1:7,060. The ratio of DB/TB and CB_MS/TB_MS of most patients with BA was elevated gradually in the neonatal period and higher than the normal range after 1 month after birth. The area under the receiver operating characteristic curve of DB, DB/TB, CB_MS/TB_MS, CB_MS, and free carnitine for predicting BA was 0.98, 0.95, 0.73, 0.57, and 0.92, respectively. Using the 95% percentile as a cutoff, the sensitivity of DB and free carnitine to predict BA was 100 and 85%, respectively, and the specificity was 52 and 85%, respectively.

CONCLUSION

 In free carnitine, DB, and CB_MS/TB_MS tests, blood concentrations are elevated in all infants with BA. However, they may not be elevated while they are newborns. These tests will result in high false negatives or positives. Thus, they should not be used as newborn screening tests for BA due to their lower sensitivity and specificity.

MicroRNA-499 rs3746444 polymorphism in Egyptian children with biliary atresia

Aim of the study

We aimed to evaluate the association of microRNA-499 rs3746444 polymorphism and biliary atresia (BA) risk and its correlation with clinic-pathologic features of BA.

Material and methods

This study was performed on 300 Egyptian children (100 BA cases, 100 cases with cholestatic liver diseases other than BA and 100 healthy controls). Routine laboratory investigations, clinical examination and abdominal ultrasound were done. All infants were genotyped for miR-499 single nucleotide polymorphisms (SNPs) (rs3746444 A>G) by real-time polymerase chain reaction (PCR) fluorescence detection on a Rotor Gene Real Time PCR System (QIAGEN, GmbH) using fluorescent labeled probes.

Results

The AG genotype was the most prevalent genotype of miR-499 rs3746444 among the studied groups. A significantly higher frequency of the rs3746444 G allele was found in the BA cases than the other groups (odds ratio = 1.62). This polymorphism was also correlated with the degree of fibrosis in BA cases (p < 0.05). The miR-499 rs3746444 polymorphism (GG genotype) was significantly associated with severe form of BA and bad prognosis after the Kasai operation (p < 0.05). miR-499 rs3746444 polymorphism had no effect on the clinic-pathological features or the liver function status in the non-BA group.

Conclusions

There is an association between the miR-499 SNP genotypes and the occurrence of BA. The variant allele G is the predominant allele in the BA group and is associated with severe liver inflammation and bad prognosis after the Kasai operation.

Impaired Redox and Protein Homeostasis as Risk Factors and Therapeutic Targets in Toxin-Induced Biliary Atresia

BACKGROUND & AIMS

Extrahepatic biliary atresia (BA) is a pediatric liver disease with no approved medical therapy. Recent studies using human samples and experimental modeling suggest that glutathione redox metabolism and heterogeneity play a role in disease pathogenesis. We sought to dissect the mechanistic basis of liver redox variation and explore how other stress responses affect cholangiocyte injury in BA.

METHODS

We performed quantitative in situ hepatic glutathione redox mapping in zebrafish larvae carrying targeted mutations in glutathione metabolism genes and correlated these findings with sensitivity to the plant-derived BA-linked toxin biliatresone. We also determined whether genetic disruption of HSP90 protein quality control pathway genes implicated in human BA altered biliatresone toxicity in zebrafish and human cholangiocytes. An in vivo screening of a known drug library was performed to identify novel modifiers of cholangiocyte injury in the zebrafish experimental BA model, with subsequent validation.

RESULTS

Glutathione metabolism gene mutations caused regionally distinct changes in the redox potential of cholangiocytes that differentially sensitized them to biliatresone. Disruption of human BA-implicated HSP90 pathway genes sensitized zebrafish and human cholangiocytes to biliatresone-induced injury independent of glutathione. Phosphodiesterase-5 inhibitors and other cyclic guanosine monophosphate signaling activators worked synergistically with the glutathione precursor N-acetylcysteine in preventing biliatresone-induced injury in zebrafish and human cholangiocytes. Phosphodiesterase-5 inhibitors enhanced proteasomal degradation and required intact HSP90 chaperone.

CONCLUSION

Regional variation in glutathione metabolism underlies sensitivity to the biliary toxin biliatresone and may account for the reported association between BA transplant-free survival and glutathione metabolism gene expression. Human BA can be causatively linked to genetic modulation of protein quality control. Combined treatment with N-acetylcysteine and cyclic guanosine monophosphate signaling enhancers warrants further investigation as therapy for BA.

Biliary Atresia Patients With Successful Kasai Portoenterostomy Can Present With Features of Obliterative Portal Venopathy

OBJECTIVE

Study of liver explants of biliary atresia (BA) patients with successful Kasai portoenterostomy (KP).

METHODS

Pathology and medical records of BA liver explants from January 2009 to June 2018 with successful KP were reviewed along with appropriate controls.

RESULTS

Fourteen out of 68 (20.6%) BA patients with LT had a successful KP. Median age at BA diagnosis, KP and LT was 60.5 days, 61 days, and 10 years, respectively, with conjugated bilirubin (c-bil) normalizing at 12.5 weeks after KP. Advanced fibrosis was diffuse in 2/14 (14.3%) explants, limited to periphery in 11/14 (78.6%) and absent in 1. Hilar partial nodular transformation (PNT) was seen in 11 explants (78.6%) and diffuse nodular regenerative hyperplasia (NRH) in 2 (14.3%). Areas of PNT and NRH showed diffuse portal sclerosis (100%), complete and incomplete portal vein (PV) stenosis (100%), PV herniation (100%), hypervascular portal tracts (20%), periportal abnormal vessels (100%), abundant lymphatic collaterals (100%), mild medial hepatic arterial hypertrophy (100%), and delicate fibrous septae (100%). Extrahepatic PVs showed variable luminal occlusion with mean PV intima to full thickness ratio of 0.6 +/- 0.11; significantly higher than age-matched noncirrhotic (n = 27, 0.08 +/- 0.09; P < 0.0001) and cirrhotic controls (n = 19, 0.34 +/- 0.2; P = 0.0015); and comparable to BA patients with failed KP (P = 0.82) and without KP (P = 0.04).

CONCLUSIONS

BA patients with successful KP can present with obliterative portal venopathy (OPV). In the context of optimal bile drainage, portal hypertension may not be because of advanced parenchymal fibrosis but possibly because of OPV. Vascular abnormalities of the PV system should be investigated in BA patients.

Serum MMP-7 in the Diagnosis of Biliary Atresia

BACKGROUND

The overlapping features of biliary atresia (BA) and other neonatal cholestasis with alternative causes (non-BA) have posed challenges for diagnosis. Matrix metalloproteinase-7 (MMP-7) has been reported to be promising in diagnosing BA. We aimed to validate the diagnostic accuracy of MMP-7 for BA in a large population sample.

METHODS

We enrolled 288 patients with neonatal obstructive jaundice from March 2017 to October 2018. Serum MMP-7 levels were measured by using an enzyme-linked immunosorbent assay. Receiver operating characteristic curves were constructed, and decision curve analysis was done. A Pearson correlation coefficient test was conducted to assess the correlation between MMP-7 levels and other characteristics.

RESULTS

The median serum MMP-7 levels were 38.89 ng/mL (interquartile range: 22.96-56.46) for the BA group and 4.4 ng/mL (interquartile range: 2.73-6.56) for the non-BA group (P < .001). The area under the receiver operating characteristic curve value was 0.9829 for MMP-7, and the sensitivity, specificity, positive predictive value, and negative predictive value were 95.19%, 93.07%, 97.27%, and 91.43%, respectively, at a cutoff value of 10.37 ng/mL. When MMP-7 was combined with γ glutamyl transferase, the diagnostic accuracy was slightly improved without significance when compared with MMP-7 alone and had an area under the curve of 0.9880 (P = .08). Decision curve analysis also showed potential for MMP-7 to be used for clinical applications. A significant correlation was found with fibrosis stage from liver biopsy (R = 0.47; P < .001).

CONCLUSIONS

MMP-7 demonstrated good accuracy in diagnosing BA and holds promise for future clinical application. Furthermore, its correlation with liver fibrosis indicated its potential use as a therapeutic target or prognostic biomarker.

Gene Expression Signatures Associated With Survival Times of Pediatric Patients With Biliary Atresia Identify Potential Therapeutic Agents

BACKGROUND & AIMS

Little is known about the factors that affect outcomes of patients with biliary atresia and there are no medical therapies that increase biliary drainage.

METHODS

Liver biopsies and clinical data were obtained from infants with cholestasis and from children without liver disease (controls); messenger RNA (mRNA) was isolated, randomly assigned to discovery (n = 121) and validation sets (n = 50), and analyzed by RNA sequencing. Using the Superpc R package followed by Cox regression analysis, we sought to identify gene expression profiles that correlated with survival without liver transplantation at 24 months of age. We also searched for combinations of gene expression patterns, clinical factors, and laboratory results obtained at diagnosis and at 1 and 3 months after surgery that associated with transplant-free survival for 24 months of age. We induced biliary atresia in BALB/c mice by intraperitoneal administration of Rhesus rotavirus type A. Mice were given injections of the antioxidants N-acetyl-cysteine (NAC) or manganese (III) tetrakis-(4-benzoic acid)porphyrin. Blood and liver tissues were collected and analyzed by histology and immunohistochemistry.

RESULTS

We identified a gene expression pattern of 14 mRNAs associated with shorter vs longer survival times in the discovery and validation sets (P < .001). This gene expression signature, combined with level of bilirubin 3 months after hepatoportoenterostomy, identified children who survived for 24 months with an area under the curve value of 0.948 in the discovery set and 0.813 in the validation set (P < .001). Computer models correlated a cirrhosis-associated transcriptome with decreased times of transplant-free survival; this transcriptome included activation of genes that regulate the extracellular matrix and numbers of activated stellate cells and portal fibroblasts. Many mRNAs expressed at high levels in liver tissues from patients with 2-year transplant-free survival had enriched scores for glutathione metabolism. Among mice with biliary atresia given injections of antioxidants, only NAC reduced histologic features of liver damage and serum levels of aminotransferase, gamma-glutamyl transferase, and bilirubin. NAC also reduced bile duct obstruction and liver fibrosis and increased survival times.

CONCLUSIONS

In studies of liver tissues from infants with cholestasis, we identified a 14-gene expression pattern that associated with transplant-free survival for 2 years. mRNAs encoding proteins that regulate fibrosis genes were increased in liver tissues from infants who did not survive for 2 years, whereas mRNAs that encoded proteins that regulate glutathione metabolism were increased in infants who survived for 2 years. NAC reduced liver injury and fibrosis in mice with biliary atresia, and increased survival times. Agents such as NAC that promote glutathione metabolism might be developed for treatment 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.

A retrospective study of the ideal operation time for preterm biliary atresia patients

OBJECTIVE

To study the ideal Kasai portoenterostomy (KPE) time for preterm infants with biliary atresia (BA) through evaluation of the postoperative effects.

METHODS

Retrospectively, 34 preterm infants with BA from 2012 to 2016 were recruited in the present study. The following three groups were established according to their chronological and corrected age at the time of KPE operation: chronological age ≤ 90 days, chronological age > 90 days and corrected age ≤ 90 days, and corrected age > 90 days. For chronological age ≤ 90 days at operation, patients were further divided into another three groups: chronological age ≤ 60 days, chronological age > 60 days and corrected age ≤ 60 days, and corrected age > 60 days. Postoperative effects were then followed up and recorded.

RESULTS

First, of those patients divided according to 90-day chronological and corrected age, postoperative total bilirubin levels (TBL), direct bilirubin levels (DBL), alanine aminotransferase (ALT), and aspartate aminotransferase (AST) of the group whose chronological age was ≤ 90 days were lower than the levels of the group whose chronological age was > 90 days and corrected age ≤ 90 days (P = 0.0472, P = 0.0358, P = 0.0083, and P = 0.0491), and the group whose corrected age was > 90 days (P = 0.0383, P = 0.0392, P = 0.0043, and P = 0.0107). Second, for those patients whose chronological age was ≤ 90 days, the group whose corrected age was > 60 days showed a higher ALT level than the other two groups with chronological age ≤ 60 days (P = 0.0472) and chronological age > 60 days and corrected age ≤ 60 days (P = 0.0258).

CONCLUSION

According to the present study, the ideal KPE time for preterm BA infants should meet two conditions: chronological age ≤ 90 days and corrected age ≤ 60 days. The groups with a chronological age ≤ 60 days, and chronological age > 60 days and corrected age ≤ 60 days show similar postoperative effects.

Recent advances in understanding biliary atresia

Biliary atresia (BA) is a neonatal liver disease characterized by progressive obstruction and fibrosis of the extrahepatic biliary tree as well as fibrosis and inflammation of the liver parenchyma. Recent studies found that infants who will go on to develop BA have elevated direct bilirubin levels in the first few days of life, suggesting that the disease starts in utero. The etiology and pathogenesis of BA, however, remain unknown. Here, we discuss recent studies examining potential pathogenetic mechanisms of BA, including genetic susceptibility, involvement of the immune system, and environmental insults such as viruses and toxins, although it is possible that there is not a single etiological agent but rather a large group of injurious insults that result in a final common pathway of extrahepatic bile duct obstruction and liver fibrosis. The management and diagnosis of BA have not advanced significantly in the past decade, but given recent advances in understanding the timing and potential pathogenesis of BA, we are hopeful that the next decade will bring early diagnostics and novel therapeutics.

Evidence for Viral Induction of Biliary Atresia: A Review

Biliary atresia (BA) is a childhood disease which manifests with abnormal narrowing, blockage or complete absence of bile ducts within the liver. Many possible etiologies have been reported for the development of BA, including congenital, perinatal and acquired conditions. Since the 1970's, there has been increasing evidence linking BA development to viral perinatal infections. The viral vectors most commonly implicated include members of the herpesviridae family (cytomegalovirus and Epstein-Barr virus) as well as those of the reoviridae family (reovirus and rotavirus). While extensive work has been done on a murine model of disease, the current review focuses primarily on evidence from human studies of viral vectors in children afflicted with BA.