Current Understanding in the Clinical Characteristics and Molecular Mechanisms in Different Subtypes of Biliary Atresia

Primary Cilia, Hypoxia, and Liver Dysfunction: A New Perspective on Biliary Atresia

Ciliopathies are disorders that affect primary or secondary cellular cilia or structures associated with ciliary function. Primary cilia (PC) are essential for metabolic regulation and embryonic development, and pathogenic variants in cilia-related genes are linked to several pediatric conditions, including renal-hepatic diseases and congenital defects. Biliary atresia (BA) is a progressive infantile cholangiopathy and the leading cause of pediatric liver transplantation. Although the exact etiology of BA remains unclear, evidence suggests a multifactorial pathogenesis influenced by both genetic and environmental factors. Patients with BA and laterality defects exhibit genetic variants associated with ciliopathies. Interestingly, even isolated BA without extrahepatic anomalies presents morphological and functional ciliary abnormalities, suggesting that environmental triggers may disrupt the ciliary function. Among these factors, hypoxia has emerged as a potential modulator of this dysfunction. Hypoxia-inducible factor 1-alpha (HIF-1α) plays a central role in hepatic responses to oxygen deprivation, influencing bile duct remodeling and fibrosis, which are key processes in BA progression. This review explores the crosstalk between hypoxia and hepatic ciliopathies, with a focus on BA. It discusses the molecular mechanisms through which hypoxia may drive disease progression and examines the therapeutic potential of targeting hypoxia-related pathways. Understanding how oxygen deprivation influences ciliary function may open new avenues for treating biliary ciliopathies and improving patient outcomes.

Evolving Concepts in Etiology of Biliary Atresia: Insights and Perspectives from India

Introduction: Biliary atresia (BA) is a potentially fatal newborn cholestatic disease. It is a rapidly advancing fibro-obliterative cholangiopathy that leads to liver failure and death if not treated early. The well-known multihit hypothesis proposes that viral or chemical disruption to the biliary epithelium triggers an immune-mediated inflammatory response, resulting in fibrosis and blockage of the intra and extrahepatic biliary systems. Methods: In recent years, several papers have noticed an upsurge in many aspects of BA, particularly its etiopathogenesis, which has opened a vista of various probable mechanisms currently being examined. This review brings them together with an emphasis on reflecting current scientific views for those interested in this illness. Conclusions: Among the different etiological factors proposed for BA, viruses and immune-mediated injury are the strongest contenders as contributors to the disease onset and pathogenesis.

Immunology of Biliary Atresia

Biliary atresia is a progressive neonatal cholangiopathy that leads to liver failure. Characterized by inflammation-mediated liver injury, the immune system plays a critical role in the pathogenesis of this disease. Though several types of immune cells and mediators have been implicated in animal models of biliary atresia, emerging literature reflects the complex interplay of components of the immune response that contributes to disease progression in humans. Novel therapies targeting the immune system are needed to mitigate the devastating effects of biliary atresia. This review highlights the current literature on the components of the immune system that have been in implicated in biliary atresia and the rich interplay between the major arms of the immune system- innate and adaptive immunity- to cause the highly morbid consequences of this disease.

Kasai Portoenterostomy, Successful Liver Transplantation, and Immunosuppressive Therapy for Biliary Atresia in a Female Baby: A Case Report

Background

Biliary atresia (BA) is a severe neonatal progressive cholangiopathy of unknown etiology. A timely Kasai portoenterostomy (KPE) improves survival of the native liver in patients with BA, although liver transplantation remains the ultimate treatment for most (60%-80%) patients. However, postoperative adverse effects of liver transplantation may be significant. In addition, patients require lifelong immunosuppressive therapy after liver transplantation.

Case Summary

Here, we report a case of a newborn female baby (birthday: 10-03-2018) with congenital BA (confirmed at 76 days of life) who survived KPE (first surgery at 85 days of life) and underwent successful living-related liver transplantation (LRLT) (second surgery at 194 days of life). Additionally, we reviewed the existing literature on BA. After KPE (at 85 days of life), the liver function of the baby did not improve, and the indicators of liver and kidney function showed a trend of aggravation, indicating that the liver function had been seriously damaged before KPE (at 85 days of life), demonstrating the urgent need for liver transplantation surgery. The female baby survived after part of her father's liver was successfully transplanted into her body (at 194 days of life). The patient recovered successfully. No other diseases were found at the 4-year follow-up, and all indices of liver and kidney functions tended to be normal.

Conclusion

This case highlights the following. Postoperative alkaline phosphatase was consistently above the normal range, although the reason for this was unclear; neither tacrolimus nor cyclosporine A has formulations designed specifically for infants, which does not meet the needs of clinical individualized medication, suggesting that these anti-rejection drugs are future development directions. Only one case of congenital BA has been found thus far in Hefei, and this case has extremely important reference significance for the prevention, treatment, and diagnosis of BA in Hefei, Anhui province.

Biliary atresia: the development, pathological features, and classification of the bile duct

Biliary atresia is an occlusive biliary disease involving intrahepatic and extrahepatic bile ducts. Its etiology and pathogenesis are unclear. There are many manifestations of bile duct involvement in biliary atresia, but little is known about its occurrence and development. In addition, different classification methods have been proposed in different periods of biliary atresia, each with its advantages and disadvantages. The combined application of biliary atresia classification will help to improve the survival rate of patients with native liver. Therefore, this article reviews the development, pathological features, and classification of intrahepatic and extrahepatic bile ducts in biliary atresia, to provide a reference for the study of the pathogenesis and the choice of treatment methods.

Chronic Liver Disease: Latest Research in Pathogenesis, Detection and Treatment

Chronic liver disease (CLD) is a major global health threat and has emerged as a leading cause of human death [...].

The influence of liver transplantation on the interplay between gut microbiome and bile acid homeostasis in children with biliary atresia

BACKGROUND

Biliary atresia (BA) causes neonatal cholestasis and rapidly progresses into cirrhosis if left untreated. Kasai portoenterostomy may delay cirrhosis. BA remains among the most common indications for liver transplantation (LT) during childhood. Liver function and gut microbiome are interconnected. Disturbed liver function and enterohepatic signaling influence microbial diversity. We, herein, investigate the impact of LT and reestablishment of bile flow on gut microbiome-bile acid homeostasis in children with BA before (pre, n = 10), 3 months (post3m, n = 12), 12 months (post12m, n = 9), and more than 24 months (post24 + m, n = 12) after LT.

METHODS

We analyzed the intestinal microbiome of BA patients before and after LT by 16S-rRNA-sequencing and bioinformatics analyses, and serum primary and secondary bile acid levels.

RESULTS

The gut microbiome in BA patients exhibits a markedly reduced alpha diversity in pre (p = 0.015) and post3m group (p = 0.044), and approximated healthy control groups at later timepoints post12m (p = 1.0) and post24 + m (p = 0.74). Beta diversity analysis showed overall community structure similarities of pre and post3m (p = 0.675), but both differed from the post24 + m (p < 0.001). Longitudinal analysis of the composition of the gut microbiome revealed the Klebsiella genus to show increased abundance in the post24 + m group compared with an age-matched control (p = 0.029). Secondary bile acid production increased 2+ years after LT (p = 0.03). Multivariable associations of microbial communities and clinical metadata reveal several significant associations of microbial genera with tacrolimus and mycophenolate mofetil-based immunosuppressive regimens.

CONCLUSIONS

In children with BA, the gut microbiome shows strongly reduced diversity before and shortly after LT, and approximates healthy controls at later timepoints. Changes in diversity correlate with altered secondary bile acid synthesis at 2+ years and with the selection of different immunosuppressants.

Genetic alterations and molecular mechanisms underlying hereditary intrahepatic cholestasis

Hereditary cholestatic liver disease caused by a class of autosomal gene mutations results in jaundice, which involves the abnormality of the synthesis, secretion, and other disorders of bile acids metabolism. Due to the existence of a variety of gene mutations, the clinical manifestations of children are also diverse. There is no unified standard for diagnosis and single detection method, which seriously hinders the development of clinical treatment. Therefore, the mutated genes of hereditary intrahepatic cholestasis were systematically described in this review.

Subclinical cardiac abnormalities in children with biliary atresia correlate with outcomes after liver transplantation

Objective

There are subclinical cardiac abnormalities (SCA) in children with biliary atresia (BA). However, data on the consequences of these cardiac changes after liver transplantation (LT) remain controversial in the pediatric field. We aimed to determine the relationship between outcomes and the subclinical cardiac abnormalities in pediatric patients with BA based on two-dimensional echocardiography (2DE) parameters.

Methods

A total of 205 children with BA were enrolled in this study. The relationship between 2DE parameters and outcomes, including death and serious adverse events (SAE) after LT, was analyzed by regression analysis. Using receiver operator characteristic (ROC) curves to determine the optimal cut-off values of 2DE parameters for outcomes. Differences in the AUCs were compared using DeLong's test. The Kaplan -Meier method with log-rank testing was used to evaluate survival outcomes between groups.

Results

Left ventricular mass index (LVMI) and relative wall thickness (RWT) were found to be independently associated with SAE (OR: 1.112, 95% CI: 1.061 - 1.165, P < 0.001 and OR: 1.193, 95% CI: 1.078 - 1.320, P = 0.001, respectively). The cutoff value of LVMI for predicting the SAE was 68 g/m2.7 (AUC = 0.833, 95% CI 0.727-0.940, P < 0.001), and the cutoff value of RWT for predicting the SAE was 0.41 (AUC = 0.732, 95% CI 0.641-0.823, P < 0.001). The presence of subclinical cardiac abnormalities (LVMI > 68 g/m2.7, and/or RWT > 0.41) was associated with lower patient survival (1-year, 90.5% vs 100.0%; 3-year, 89.7% vs 100.0, log-rank P = 0.001). and higher incidence of SAE events.

Conclusions

Subclinical cardiac abnormalities were correlated with post-LT mortality and morbidity in children with BA. LVMI can predict the occurrence of death and serious adverse events after liver transplantation.

[New advances in the diagnosis and treatment of biliary atresia]

The diagnosis of biliary atresia (BA) is mainly based on clinical manifestations, screening, and related biochemistry tests. In recent years, the development of blood biomarkers and the improvement in ultrasound examination have made it possible for BA to be diagnosed at a younger age. In particular, matrix metalloproteinase-7 shows high sensitivity and specificity and has a higher diagnostic efficiency than existing biochemical parameters, thereby holding a promise for clinical application. Sound touch elastography can increase the diagnostic efficiency for BA in terms of diagnosis and prognostic evaluation. Surgery is still the only method for the treatment of BA at present, with the preferred surgical treatment regimen of Kasai portoenterostomy combined with pharmacotherapies for alleviating infection and inflammation, and the patients who fail Kasai portoenterostomy or have liver dysfunction may require liver transplantation to save their lives. Therefore, the current research on BA should focus on the biomarkers for early diagnosis, specifically targeted drugs, and drugs for preventing progressive liver fibrosis. This article reviews the current diagnosis and treatment methods for BA and discusses the potential research directions.