Bile Canaliculi Research Articles

Activation of S1PR2 on macrophages and the hepatocyte S1PR2/RhoA/ROCK1/MLC2 pathway in vanishing bile duct syndrome.

Immunologic bile duct destruction is a pathogenic condition associated with vanishing bile duct syndrome (VBDS) after liver transplantation and hematopoietic stem-cell transplantation. As the bile acid receptor sphingosine 1-phosphate receptor 2 (S1PR2) plays a critical role in recruitment of bone marrow-derived monocytes/macrophages to sites of cholestatic liver injury, S1PR2 expression was examined using cultured macrophages and patient tissues. Bile canaliculi destruction precedes intrahepatic ductopenia; therefore, we focused on hepatocyte S1PR2 and the downstream RhoA/Rho kinase 1 (ROCK1) signaling pathway and bile canaliculi alterations using three-dimensional hepatocyte culture models that form obvious bile canaliculus-like networks. Multiplex immunohistochemistry revealed increased numbers of S1PR2+CD45+CD68+FCN1+ inflammatory macrophages and S1PR2+CD45+CD68+MARCO+ Kupffer cells in liver tissues showing ductopenia due to graft-versus-host disease and rejection post-liver transplant compared with normal liver. Macrophage expression of proinflammatory cytokines, including MCP1, was reduced following S1PR2 inhibition. Taurocholic acid and S1P2 agonist induced hepatocyte S1PR2 and reduced RhoA/ROCK1 expression, resulting in bile canaliculi dilatation. S1PR2 inhibition reversed the effect on RhoA/ROCK1 expression, resulting in maintenance of bile canaliculi through myosin light chain 2 (MLC2) phosphorylation. Activation of S1PR2 on macrophages and S1PR2 on hepatocytes may disrupt bile canaliculi dynamics in VBDS under regulation by RhoA/ROCK1 through MLC2 phosphorylation.

The Impact of Methamphetamine on Liver Injury in Iraqi Male Addicts

Methamphetamine (METH) is a powerful stimulant that affects neurochemical processes controlling heart rate, appetite, blood pressure, body temperature, and wakefulness, making it highly susceptible to abuse. Liver enzymes such as ALT, AST, ALP, and GGT are crucial for liver function. Albumin, a protein synthesized by healthy liver cells, serves as an indicator of chronic liver disease. Additionally, hepatocytes produce bile acids, which are essential for the secretion of bile salts into the bile canaliculi. Disruption in this secretion results in the accumulation of bile salts in the canaliculi, leading to intrahepatic cholestasis. METH-induced liver toxicity involves disruptions in hepatic metabolism, oxidative stress, and increased body temperature, affecting cellular processes such as cell division and the cell cycle and potentially accelerating liver cell apoptosis. The study explores the link between liver toxicity and hepatocyte damage in Iraqi males suffering from addiction. This is a case-control study, conducted at Ibn-Rushed Psychiatric Hospital in Baghdad from July 2023 to February 2024, involved 196 males, with addiction durations exceeding 24 months with varying degrees of methamphetamine (METH) addiction. The study included 187 healthy male controls with no history of drug addiction. Participants were aged 18 to 40 years. Diagnosis was confirmed using a drug test screening card administered by a specialist. The study included liver function tests (ALT, AST, ALP, and GGT), total bilirubin, and albumin concentration assessments. Significant differences were observed between the addicts and controls, particularly a marked decrease in serum albumin concentration in the addicted males. The ROC curve classification model at various thresholds demonstrated that liver enzymes, especially ALT, ALP, and GGT, exhibited increased sensitivity to METH addiction. A histopathological examination was conducted on a deceased 38-year-old male who had a six-year history of chronic amphetamine addiction to confirm liver injury and the resulting elevation of liver enzymes. The findings of this study indicate that METH greatly affects liver function, suggested to the importance of following a preventative measures and effective treatment approaches for monitoring METH addiction progress.

Hepatocyte differentiation requires anisotropic expansion of bile canaliculi.

During liver development, bipotential progenitor cells called hepatoblasts differentiate into hepatocytes or cholangiocytes. Hepatocyte differentiation is uniquely associated with multi-axial polarity, enabling the anisotropic expansion of apical lumina between adjacent cells and formation of a three-dimensional network of bile canaliculi. Cholangiocytes, the cells forming the bile ducts, exhibit the vectorial polarity characteristic of epithelial cells. Whether cell polarization feeds back on the gene regulatory pathways governing hepatoblast differentiation is unknown. Here, we used primary mouse hepatoblasts to investigate the contribution of anisotropic apical expansion to hepatocyte differentiation. Silencing of the small GTPase Rab35 caused isotropic lumen expansion and formation of multicellular cysts with the vectorial polarity of cholangiocytes. Gene expression profiling revealed that these cells express reduced levels of hepatocyte markers and upregulate genes associated with cholangiocyte identity. Timecourse RNA sequencing demonstrated that loss of lumen anisotropy precedes these transcriptional changes. Independent alterations in apical lumen morphology induced either by modulation of the subapical actomyosin cortex or by increased intraluminal pressure caused similar transcriptional changes. These findings suggest that cell polarity and lumen morphogenesis feed back to hepatoblast-to-hepatocyte differentiation.

Neonatal Hemochromatosis Secondary to an Inborn Error of Metabolism (Mitochondrial Disorder): Post- mortem Diagnosis in the Fetus of a Young Primipara

Abstract Introduction/Objective Neonatal hemochromatosis (NH), an extremely rare congenital phenotype of acute hepatic failure with hepatic and extrahepatic siderosis, is primarily (98%) caused by gestational alloimmune liver disease (GALD) and, rarely (2%), by infection, metabolic disorders, bile acid defects, and mitochondrial hepatopathy. This report presents an extremely rare case of NH caused by an inborn error of metabolism (suspected mitochondrial dysfunction). This low-birth-weight female was born with acute liver failure, metabolic acidosis, multisystem failure, and progressive lactate acidosis, and expired on day 7. On autopsy, liver was less than 50% of normal size and without nodularity. Microscopic architecture was preserved with erythropoiesis, canalicular bile plugs, microvesicular steatosis (oil red O stain) and abundant coarsely granular siderosis (iron stain). GALD was unlikely because of the absence of the typical hepatocytic injury, fibrosis or biliary destruction, and the negative immunohistochemistry for MAC (C5b-C9). Extrahepatic siderosis was demonstrated in thyroid follicles, thymic Hassall corpuscles, myocardium, and adenohypophysis. Sanger sequencing and deletion testing of mitochondrial genome on a maternal buccal biopsy identified a homoplasmic variant (m.15482 T>C p.(S246P) in maternal MT-CYB gene but without molecular diagnosis of a mitochondrial DNA disorder. Infant plasma had increased C6DC, C5, C12-OH acylcarnitine, alanine, and proline. Urine contained elevated organic acids (lactate/pyruvate, 2-ketoacids, 3-methylglutarate, 3-methylglutaconate), concerning acute mitochondrial respiratory chain dysfunction. Methods/Case Report: Case Study Results (if a Case Study enter NA) NA Conclusion Diagnosis of NH warrants exclusion of the most common etiology, GALD. Mitochondrial genetic mutations are the most difficult to diagnosis because of heterogeneity and typically undiagnosed maternal defects. This is the first report of NH with a homoplasmic maternal variant of uncertain significance. Neonatal lactic acidosis is the strongest clinical clue for mitochondrial dysfunction and should trigger phenotyping, maternal mitochondrial genetic variants (mtDNA, nuDNA), functional, biochemical, and genetic studies.

Comparative analysis of bile acid composition and metabolism in the liver of Bufo gargarizans aquatic larvae and terrestrial adults

Bile acids are crucial for lipid metabolism and their composition and metabolism differ among species. However, there have been no data on the differences in the composition and metabolism of bile acids between aquatic larvae and terrestrial adults of amphibians. This study explored the differences in composition and metabolism of bile acid between Bufo gargarizans larvae and adults. The results demonstrated that adult liver had a lower total bile acid level and a higher conjugated/total bile acid ratio than larval liver. Meanwhile, histological analysis revealed that the larvae showed a larger cross-sectional area of bile canaliculi lumen compared with the adults. The transcriptomic analysis showed that B. gargarizans larvae synthesized bile acids through both the alternative and the 24-hydroxylase pathway, while adults only synthesized bile acids through the 24-hydroxylase pathway. Moreover, bile acid regulator-related genes FXR and RXRα were highly expressed in adult, whereas genes involved in bile acid synthesis (CYP27A1 and CYP46A1) were highly expressed in larvae. The present study will provide valuable insights into understanding metabolic disorders and exploring novel bile acid-based therapeutics.

P01-54 New fluorescent probes for quick assessment of drug induced liver injury effects on bile canaliculi dynamism and albumin expression

P01-54 New fluorescent probes for quick assessment of drug induced liver injury effects on bile canaliculi dynamism and albumin expression

Generation of human hepatobiliary organoids with a functional bile duct from chemically induced liver progenitor cells

BackgroundLiver disease imposes a significant medical burden that persists due to a shortage of liver donors and an incomplete understanding of liver disease progression. Hepatobiliary organoids (HBOs) could provide an in vitro mini-organ model to increase the understanding of the liver and may benefit the development of regenerative medicine.MethodsIn this study, we aimed to establish HBOs with bile duct (BD) structures and mature hepatocytes (MHs) using human chemically induced liver progenitor cells (hCLiPs). hCLiPs were induced in mature cryo-hepatocytes using a small-molecule cocktail of TGF-β inhibitor (A-83-01, A), GSK3 inhibitor (CHIR99021, C), and 10% FBS (FAC). HBOs were then formed by seeding hCLiPs into ultralow attachment plates and culturing them with a combination of small molecules of Rock-inhibitor (Y-27632) and AC (YAC).ResultsThese HBOs exhibited bile canaliculi of MHs connected to BD structures, mimicking bile secretion and transportation functions of the liver. The organoids showed gene expression patterns consistent with both MHs and BD structures, and functional assays confirmed their ability to transport the bile analogs of rhodamine-123 and CLF. Functional patient-specific HBOs were also successfully created from hCLiPs sourced from cirrhotic liver tissues.ConclusionsThis study demonstrated the potential of human HBOs as an efficient model for studying hepatobiliary diseases, drug discovery, and personalized medicine.

Microplastic-induced hepatic adverse effects evaluated in advanced quadruple cell human primary models following three weeks of repeated exposure

Nano and microplastics are defined as particles smaller than 100 nm and 5 mm respectively. The widespread production and use of plastics in everyday life has resulted in significant accumulation of plastic debris in the environment. Over the last two decades there are increased concerns regarding the potential entry and accumulation of plastics in the human body with ingestion being one of the most important routes of exposure. However, the magnitude and nature of potential toxic effects of plastic exposure to human health is not yet fully understood. The liver is the body's principal detoxification organ and critically to this study recognized as the main accumulation site for particulates. In this study as the first of its kind the health impacts of long term low repeated polystyrene microplastics (1 and 5 μm) exposure was investigated in a functionally active 3D liver microtissue model, composed of primary human hepatocytes, Kupffer cells, sinusoidal endothelial cells and hepatic stellate cells. The highlight from the data includes microplastic-induced dose (3.125–25 μg/ml) and time dependent (up to 504 h) increase in cell death and inflammation manifested by enhanced release of IL6, IL8 and TNF-α. The exposure to repeated dosing of the plastics also resulted in notable pathology manifested as aberrant tissue architecture, such as dilated bile canaliculi and large lipid droplets inside the hepatic cells. This toxicity matched extremely well to the accumulation of the materials with the cells of microtissue predominately in the organ macrophages. This study highlights the real issue and danger of microplastic exposure with potential for long-term accumulation and adverse effects of non-biodegradable plastics within the liver.

Non-invasive Visualization and Characterization of Bile Canaliculus Formation Using Refractive Index Tomography

The vital role of bile canaliculus (BC) in liver function is closely related to its morphology. Electron microscopy has contributed to understanding BC morphology; however, its invasiveness limits its use in living specimens. Here, we report non-invasive characterization of BC formation using refractive index (RI) tomography. First, we investigated and characterized the RI distribution of BCs in two-dimensional (2D) cultured HepG2 cells. BCs were identified based on their distinct morphology and functionality, as confirmed using a fluorescence-labeled bile acid analog. The RI distribution of BCs exhibited three common features: (1) luminal spaces with a low RI between adjacent hepatocytes; (2) luminal spaces surrounded by a membranous structure with a high RI; and (3) multiple microvillus structures with a high RI within the lumen. Second, we demonstrated the characterization of BC structures in a three-dimensional (3D) culture model, which is more relevant to the in vivo environment but more difficult to evaluate than 2D cultures. Various BC structures were identified inside HepG2 spheroids with the three features of RI distribution. Third, we conducted comparative analyses and found that the BC lumina of spheroids had higher circularity and lower RI standard deviation than 2D cultures. We also addressed comparison of BC and intracellular lumen-like structures within a HepG2 spheroid, and found that the BC lumina had higher RI and longer perimeter than intracellular lumen-like structures. Our demonstration of the non-destructive, label-free visualization and quantitative characterization of living BC structures will be a basis for various hepatological and pharmaceutical applications.

Establishment of human induced pluripotent stem cell-derived hepatobiliary organoid with bile duct for pharmaceutical research use

In vitro models of the human liver are promising alternatives to animal tests for drug development. Currently, primary human hepatocytes (PHHs) are preferred for pharmacokinetic and cytotoxicity tests. However, they are unable to recapitulate the flow of bile in hepatobiliary clearance owing to the lack of bile ducts, leading to the limitation of bile analysis. To address the issue, a liver organoid culture system that has a functional bile duct network is desired. In this study, we aimed to generate human iPSC-derived hepatobiliary organoids (hHBOs) consisting of hepatocytes and bile ducts. The two-step differentiation process under 2D and semi-3D culture conditions promoted the maturation of hHBOs on culture plates, in which hepatocyte clusters were covered with monolayered biliary tubes. We demonstrated that the hHBOs reproduced the flow of bile containing a fluorescent bile acid analog or medicinal drugs from hepatocytes into bile ducts via bile canaliculi. Furthermore, the hHBOs exhibited pathophysiological responses to troglitazone, such as cholestasis and cytotoxicity. Because the hHBOs can recapitulate the function of bile ducts in hepatobiliary clearance, they are suitable as a liver disease model and would be a novel in vitro platform system for pharmaceutical research use.

Formation of functional, extended bile canaliculi, and increased bile acid production in sandwich-cultured human cryopreserved hepatocytes using commercially available culture medium

Drug-induced cholestasis results in drug discontinuation and market withdrawal, and the prediction of cholestasis risk is critical in the early stages of drug development. Animal tests and membrane vesicle assay are currently being conducted to assess the risk of cholestasis in the preclinical stage. However, these methods have drawbacks, such as species differences with humans and difficulties in evaluating the effects of drug metabolism and other transporters, implying the need for a cholestasis risk assessment system using human hepatocytes. However, human hepatocytes hardly form functional, extended bile canaliculi, a requirement for cholestasis risk assessment. We previously established a culture protocol for functional, extended bile canaliculi formation in human iPSC-derived hepatocytes. In this study, we modified this culture protocol to support the formation of functional, extended bile canaliculi in human cryopreserved hepatocytes (cryoheps). The production of bile acids, which induces bile canaliculi extension, increased time-dependently during bile canaliculi formation using this protocol, suggesting that increased bile acid production may be involved in the extended bile canaliculi formation. We have also shown that our culture protocol can be applied to cryoheps from multiple donors and that bile canaliculi can be formed stably among different culture batches. Furthermore, this protocol enables long-term maintenance of bile canaliculi and scaling down to culture in 96-well plates. We expect our culture protocol to be a breakthrough for in vitro cholestasis risk assessment.

ICAM-1 nanoclusters regulate hepatic epithelial cell polarity by leukocyte adhesion-independent control of apical actomyosin.

Epithelial intercellular adhesion molecule (ICAM)-1 is apically polarized, interacts with, and guides leukocytes across epithelial barriers. Polarized hepatic epithelia organize their apical membrane domain into bile canaliculi and ducts, which are not accessible to circulating immune cells but that nevertheless confine most of ICAM-1. Here, by analyzing ICAM-1_KO human hepatic cells, liver organoids from ICAM-1_KO mice and rescue-of-function experiments, we show that ICAM-1 regulates epithelial apicobasal polarity in a leukocyte adhesion-independent manner. ICAM-1 signals to an actomyosin network at the base of canalicular microvilli, thereby controlling the dynamics and size of bile canalicular-like structures. We identified the scaffolding protein EBP50/NHERF1/SLC9A3R1, which connects membrane proteins with the underlying actin cytoskeleton, in the proximity interactome of ICAM-1. EBP50 and ICAM-1 form nano-scale domains that overlap in microvilli, from which ICAM-1 regulates EBP50 nano-organization. Indeed, EBP50 expression is required for ICAM-1-mediated control of BC morphogenesis and actomyosin. Our findings indicate that ICAM-1 regulates the dynamics of epithelial apical membrane domains beyond its role as a heterotypic cell-cell adhesion molecule and reveal potential therapeutic strategies for preserving epithelial architecture during inflammatory stress.

ICAM-1 nanoclusters regulate hepatic epithelial cell polarity by leukocyte adhesion-independent control of apical actomyosin

Epithelial intercellular adhesion molecule (ICAM)-1 is apically polarized, interacts with, and guides leukocytes across epithelial barriers. Polarized hepatic epithelia organize their apical membrane domain into bile canaliculi and ducts, which are not accessible to circulating immune cells but that nevertheless confine most of ICAM-1. Here, by analyzing ICAM-1_KO human hepatic cells, liver organoids from ICAM-1_KO mice and rescue-of-function experiments, we show that ICAM-1 regulates epithelial apicobasal polarity in a leukocyte adhesion-independent manner. ICAM-1 signals to an actomyosin network at the base of canalicular microvilli, thereby controlling the dynamics and size of bile canalicular-like structures. We identified the scaffolding protein EBP50/NHERF1/SLC9A3R1, which connects membrane proteins with the underlying actin cytoskeleton, in the proximity interactome of ICAM-1. EBP50 and ICAM-1 form nano-scale domains that overlap in microvilli, from which ICAM-1 regulates EBP50 nano-organization. Indeed, EBP50 expression is required for ICAM-1-mediated control of BC morphogenesis and actomyosin. Our findings indicate that ICAM-1 regulates the dynamics of epithelial apical membrane domains beyond its role as a heterotypic cell–cell adhesion molecule and reveal potential therapeutic strategies for preserving epithelial architecture during inflammatory stress.

On‐Chip Differentiation of Hepatic Cords with Radial Flow

Due to a more physiological reproduction of the in vivo situation, liver‐on‐a‐chip devices in recent studies have shown higher sensitivity and accuracy for hepatotoxicity testing compared to traditional in vitro liver models. In this context, this work presents an original microfluidic device mimicking 3D hepatic cords organized radially, like in the liver lobule. Ten cell‐culture chambers seeded at a high density are disposed with a parallelized flow that emulates blood flow from the portal triad to the central vein in the liver lobule. Using this device, on‐chip differentiation of human HepaRG‐Hepatoblast (HepaRG‐HB) to HepaRG‐Hepatocytes (HepaRG‐HC) has been studied in terms of self‐organization capabilities, bile canaliculi formation and albumin expression. Our results indicate that due to the design of the cell culture chamber, which mechanically constrains tissue proliferation, and the physiologically relevant microfluidic flow condition used during tissue development, the HepaRG‐HBs in the device can proliferate, self‐organize, and spontaneously differentiate in a DMSO free medium forming long, directional bile canaliculi. On the contrary, under the same conditions, differentiated HepaRG‐HC is observed to aggregate without long bile canaliculi and form tissues resembling traditional HepaRG‐HC cultures. © 2024 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Acetaminophen overdose causes a breach of the blood-bile barrier in mice but not in rats.

Acetaminophen (APAP) is known to cause a breach of the blood-bile barrier in mice that, via a mechanism called futile bile acid (BA) cycling, increases BA concentrations in hepatocytes above cytotoxic thresholds. Here, we compared this mechanism in mice and rats, because both species differ massively in their susceptibility to APAP and compared the results to available human data. Dose and time-dependent APAP experiments were performed in male C57BL6/N mice and Wistar rats. The time course of BA concentrations in liver tissue and in blood was analyzed by MALDI-MSI and LC-MS/MS. APAP and its derivatives were measured in the blood by LC-MS. APAP-induced liver damage was analyzed by histopathology, immunohistochemistry, and by clinical chemistry. In mice, a transient increase of BA in blood and in peri-central hepatocytes preceded hepatocyte death. The BA increase coincided with oxidative stress in liver tissue and a compromised morphology of bile canaliculi and immunohistochemically visualized tight junction proteins. Rats showed a reduced metabolic activation of APAP compared to mice. However, even at very high doses that caused cell death of hepatocytes, no increase of BA concentrations was observed neither in liver tissue nor in the blood. Correspondingly, no oxidative stress was detectable, and the morphology of bile canaliculi and tight junction proteins remained unaltered. In conclusion, different mechanisms cause cell death in rats and mice, whereby oxidative stress and a breach of the blood-bile barrier are seen only in mice. Since transient cholestasis also occurs in human patients with APAP overdose, mice are a clinically relevant species to study APAP hepatotoxicity but not rats.

Comparative transcriptomic and phenotypic analysis of induced pluripotent stem cell hepatocyte-like cells and primary human hepatocytes.

Primary human hepatocytes (PHHs) are used extensively for in vitro liver cultures to study hepatic functions. However, limited availability and invasive retrieval prevent their widespread use. Induced pluripotent stem cells exhibit significant potential since they can be obtained non-invasively and differentiated into hepatic lineages, such as hepatocyte-like cells (iHLCs). However, there are concerns about their fetal phenotypic characteristics and their hepatic functions compared to PHHs in culture. Therefore, we performed an RNA-sequencing (RNA-seq) analysis to understand pathways that are either up- or downregulated in each cell type. Analysis of the RNA-seq data showed an upregulation in the bile secretion pathway where genes such as AQP9 and UGT1A1 were higher expressed in PHHs compared to iHLCs by 455- and 15-fold, respectively. Upon immunostaining, bile canaliculi were shown to be present in PHHs. The TCA cycle in PHHs was upregulated compared to iHLCs. Cellular analysis showed a 2-2.5-fold increase in normalized urea production in PHHs compared to iHLCs. In addition, drug metabolism pathways, including cytochrome P450(CYP450) and UDP-glucuronosyltransferase enzymes, were upregulated in PHHs compared to iHLCs. Of note, CYP2E1 gene expression was significantly higher (21,810-fold) in PHHs. Acetaminophen and ethanol were administered to PHH and iHLC cultures to investigate differences in biotransformation. CYP450 activity of baseline and toxicant-treated samples was significantly higher in PHHs compared to iHLCs. Our analysis revealed that iHLCs have substantial differences from PHHs in critical hepatic functions. These results have highlighted the differences in gene expression and hepatic functions between PHHs and iHLCs to motivate future investigation.

Novel approach for reconstruction of the three-dimensional biliary system in decellularized liver scaffold using hepatocyte progenitors.

Reconstruction of the biliary system is indispensable for the regeneration of transplantable liver grafts. Here, we report the establishment of the first continuous three-dimensional biliary system scaffold for bile acid excretion using a novel method. We confirmed the preservation of the liver-derived extracellular matrix distribution in the scaffold. In addition, hepatocyte progenitors decellularized via the bile duct by slow-speed perfusion differentiated into hepatocyte- and cholangiocyte-like cells, mimicking hepatic cords and bile ducts, respectively. Furthermore, qRT-PCR demonstrated increased ALB, BSEP, and AQP8 expression, revealing bile canaliculi- and bile duct-specific genetic patterns. Therefore, we concluded that locally preserved extracellular matrices in the scaffold stimulated hepatic progenitors and provided efficient differentiation, as well as regeneration of a three-dimensional continuous biliary system from hepatic cords through bile ducts. These findings suggest that organ-derived scaffolds can be utilized for the efficient reconstruction of functional biliary systems.

A286 MYO5B MUTATIONS AS A CAUSE OF CHOLESTASIS IN A CHILD WITHOUT MICROVILLOUS INCLUSION DISEASE

Abstract Background Biallelic Myosin Vb (MYO5B) mutations are identified in the majority of patients with microvillus inclusion disease (MVID) that requires life-long parenteral nutrition and eventually cholestatic liver disease. Biallelic MYO5B mutations have also been reported in a few children with predominant early-onset cholestatic liver disease. Aims To report on a patient with MYO5B mutations and progressive familial intrahepatic cholestasis PFIC-like phenotype and normal serum GGT without intestinal disease. Methods We describe a 2-year and 8-month-old girl, who is the first child of healthy non- consanguineous parents from the Phillipines with no family history of liver disease. She presented at the age of 10 months for evaluation of mild jaundice, which was noticed at the age of 6 months. Other symptoms included pruritus, slowly weight gain, intermittent pale stools and dark urine. Laboratory investigations revealed AST 99, ALT 87, GGT 27, conjugated bilirubin 13 and INR 0.8. Fasting abdominal ultrasound was normal apart from a possibly hypoplastic gallbladder and mild splenomegaly. Additional investigations revealed normal thyroid-stimulating hormone, cortisol, galactosemia screening and sweat chloride, but bile acids were elevated 391.6 umol/L. A liver biopsy was performed and a cholestasis genetic panel sent. The patient was started on ursodiol, hydroxyzine, rifampicin and vitamin D. Results Liver biopsy revealed moderate hepato-canalicular cholestasis, bile duct injury without prominent ductopenia, small caliber bile ducts with no features of obstructive cholangiopathy, mild periportal and pericentral fibrosis stage 1-2/ 4. Electron microscopy demonstrated cytoplasmic and canalicular bile accumulation. The bile canaliculi were variably distended by coarse granular bile. Immunohistochemical staining for BSEP and MDR3, showed canalicular staining in zones 1 and absence of staining in zones 2 and 3. Genetic analysis revealed one pathogenic variant and one variant of uncertain significance in MYO5B. No mutations in ABCB11 or ATP8B1 genes were identified. On follow-up, the jaundice improved, pruritus was managed with the medications described above. Her growth has improved and she is growing on the 25th centiles. She has not developed any gastrointestinal symptoms. Conclusions We present a patient with MYO5B mutations who presented with normal GGT cholestasis and a liver biopsy consistent with PFIC, without any evidence of intestinal disease. Because MYO5B mutations disrupt the intracellular trafficking of brush border proteins in the intestine, it has been assumed that it similarly disrupts the trafficking of the canalicular bile acid transporting and bilirubin transporting proteins in the liver. This case highlights the broad phenotype associated with MYO5B variants. Funding Agencies None

Development of a human liver microphysiological coculture system for higher throughput chemical safety assessment.

Chemicals in the systemic circulation can undergo hepatic xenobiotic metabolism, generate metabolites, and exhibit altered toxicity compared with their parent compounds. This article describes a 2-chamber liver-organ coculture model in a higher-throughput 96-well format for the determination of toxicity on target tissues in the presence of physiologically relevant human liver metabolism. This 2-chamber system is a hydrogel formed within each well consisting of a central well (target tissue) and an outer ring-shaped trough (human liver tissue). The target tissue chamber can be configured to accommodate a three-dimensional (3D) spheroid-shaped microtissue, or a 2-dimensional (2D) cell monolayer. Culture medium and compounds freely diffuse between the 2 chambers. Human-differentiated HepaRG liver cells are used to form the 3D human liver microtissues, which displayed robust protein expression of liver biomarkers (albumin, asialoglycoprotein receptor, Phase I cytochrome P450 [CYP3A4] enzyme, multidrug resistance-associated protein 2 transporter, and glycogen), and exhibited Phase I/II enzyme activities over the course of 17 days. Histological and ultrastructural analyses confirmed that the HepaRG microtissues presented a differentiated hepatocyte phenotype, including abundant mitochondria, endoplasmic reticulum, and bile canaliculi. Liver microtissue zonation characteristics could be easily modulated by maturation in different media supplements. Furthermore, our proof-of-concept study demonstrated the efficacy of this coculture model in evaluating testosterone-mediated androgen receptor responses in the presence of human liver metabolism. This liver-organ coculture system provides a practical, higher-throughput testing platform for metabolism-dependent bioactivity assessment of drugs/chemicals to better recapitulate the biological effects and potential toxicity of human exposures.

The noncanonical nucleotide binding site 1 of the bile salt export pump is optimized for proper function of the transporter.

The bile salt export pump (ABCB11/BSEP) is a hepatocyte plasma membrane-resident protein translocating bile salts into bile canaliculi. The sequence alignment of the four full-length transporters of the ABCB subfamily (ABCB1, ABCB4, ABCB5 and ABCB11) indicates that the NBD-NBD contact interface of ABCB11 differs from that of other members in only four residues. Notably, these are all located in the noncanonical nucleotide binding site 1 (NBS1). Substitution of all four deviant residues with canonical ones (quadruple mutant) significantly decreased the transport activity of the protein. In this study, we mutated two deviant residues in the signature sequence to generate a double mutant (R1221G/E1223Q). Furthermore, a triple mutant (E502S/R1221G/E1223Q) was generated, in which the deviant residues of the signature sequence and Q-loop were mutated concurrently to canonical residues. The double and triple mutants showed 80% and 60%, respectively, of the activity of wild-type BSEP. As expected, an increasing number of mutations gradually impair transport as an intricate network of interactions within the ABC proteins ensures proper functioning.