Novel therapeutics for primary biliary cholangitis: Toward a disease-stage-based approach

Dual B-cell targeting therapy ameliorates autoimmune cholangitis

OBJECTIVE

The ability to regulate B cell development has long been recognized to have therapeutic potential in a variety of autoimmune diseases. However, despite the presence of a classic autoantibody in primary biliary cholangitis (PBC), B cell depleting therapy and indeed therapy with other biologic agents has been disappointing. Unsuccessful treatment using Rituximab is associated with elevation of B-cell activating factor (BAFF) level. Indeed, therapies for PBC remain directed at modulating bile salt biology, rather than targeting effector pathways. With these data in mind, we proposed that targeting two major stages of B cell development, namely long-lived memory B cells and short-lived peripheral autoreactive plasma cells would have therapeutic potential.

METHODS

To address this thesis, we administrated anti-BAFF and anti-CD20 monoclonal antibody to ARE-Del mice, a well-characterized murine model of human PBC. We evaluated and compared the therapeutic efficacy of the two agents individually and the combination of anti-BAFF and anti-CD20 in female mice with well-established disease.

RESULTS

Our data demonstrate that there was an increased level of B cell depletion that resulted in a significantly more effective clinical and serologic response using the combination of agents as compared with the use of the individual agents. The combination of anti-BAFF and anti-CD20 treatment was more effective in reducing serum levels of antimitochondrial antibody (AMA), total IgM and IgG compared to mice treated with the 2 individual agents. Combination treatment efficiently depleted B cells in the peripheral blood, peritoneal cavity and spleen. Importantly, we identified a unique IgM+ FCRL5+ B cell subset which was sensitive to dual B-cell targeting therapy and depletion of this unique population was associated with reduced portal infiltration and bile duct damage. Taken together, our data indicate that dual B cell targeting therapy with anti-BAFF and anti-CD20 not only led to the efficient depletion of B cells both in the peripheral blood and tissues, but also led to significant clinical improvement. These findings highlight the potential application of combination of anti-BAFF and anti-CD20 in treating patients with PBC. However, additional studies in other animal models of PBC should be undertaken before considering human trials in those PBC patients who have incomplete responses to conventional therapy.

Mitigation of portal fibrosis and cholestatic liver disease in ANKS6-deficient livers by macrophage depletion

Congenital hepatic fibrosis (CHF) is a developmental liver disease that is caused by mutations in genes that encode ciliary proteins and is characterized by bile duct dysplasia and portal fibrosis. Recent work has demonstrated that mutations in ANKS6 can cause CHF due to its role in bile duct development. Here, we report a novel ANKS6 mutation, which was identified in an infant presenting with neonatal jaundice due to underlying biliary abnormalities and liver fibrosis. Molecular analysis revealed that ANKS6 liver pathology is associated with the infiltration of inflammatory macrophages to the periportal fibrotic tissue and ductal epithelium. To further investigate the role of macrophages in CHF pathophysiology, we generated a novel liver-specific Anks6 knockout mouse model. The mutant mice develop biliary abnormalities and rapidly progressing periportal fibrosis reminiscent of human CHF. The development of portal fibrosis in Anks6 KO mice coincided with the accumulation of inflammatory monocytes and macrophages in the mutant liver. Gene expression and flow cytometric analysis demonstrated the preponderance of M1- over M2-like macrophages at the onset of fibrosis. A critical role for macrophages in promoting peribiliary fibrosis was demonstrated by depleting the macrophages with clodronate liposomes which effectively reduced inflammatory gene expression and fibrosis, and ameliorated tissue histology and biliary function in Anks6 KO livers. Together, this study demonstrates that macrophages play an important role in the initiation of liver fibrosis in ANKS6-deficient livers and their therapeutic elimination may provide an avenue to mitigate CHF in patients.

Characteristics and Inpatient Outcomes of Primary Biliary Cholangitis and Autoimmune Hepatitis Overlap Syndrome

BACKGROUND AND AIMS

Primary biliary cholangitis (PBC) and autoimmune hepatitis (AIH) are hepatobiliary diseases of presumed immune-mediated origin that have been shown to overlap. The aim of this retrospective trial was to use national data to examine the characteristics and outcomes of patients hospitalized with overlapping PBC and AIH (PBC/AIH).

METHODS

The National Inpatient Sample was used to identify hospitalized adult patients with PBC, AIH, and PBC/AIH from 2010 to 2014 by International Classification of Diseases-Ninth Edition Revision codes; patients with hepatitis B virus and hepatitis C virus infection were excluded. Primary outcomes measures were in-hospital outcomes that included mortality, respiratory failure, septic shock, length of stay, and total hospital charges. Secondary outcomes were the clinical characteristics of PBC/AIH, including the comorbid extrahepatic autoimmune disease pattern and complications of cirrhosis.

RESULTS

A total of 3,478 patients with PBC/AIH were included in the study. PBC/AIH was associated with higher rates of Sjögren's syndrome (p<0.001; p<0.001), lower rates of Crohn's disease (p<0.05; p<0.05), and higher rates of cirrhosis-related complications when compared to PBC or AIH alone. There were similar rates of mortality between the PBC/AIH, PBC, and AIH groups. The PBC/AIH group had higher rates of septic shock when compared to the PBC group (p<0.05) and AIH group (p<0.05) after adjusting for possible confounders.

CONCLUSIONS

PBC/AIH is associated with a lower rate of Crohn's disease, a higher rate of Sjögren's syndrome, higher rates of cirrhosis-related complications, and significantly increased risk of septic shock compared to PBC and AIH individually.

Clinical Management of Primary Biliary Cholangitis-Strategies and Evolving Trends

PBC is a chronic progressive autoimmune disorder involving the destruction of intrahepatic small bile ducts, cholestasis, fibrosis, and ultimately cirrhosis if left untreated. It is largely driven by the autoimmune response, but bile acids and the intestinal microbiota are implicated in disease progression as well. The only drugs licensed for PBC are UDCA and OCA. UDCA as a first-line and OCA as a second-line therapy are safe and effective, but the lack of response in a significant portion of patients and inadequate control of symptoms such as fatigue and pruritus remain as concerns. Liver transplantation is an end-stage therapy for many patients refractory to UDCA, which gives excellent survival rates but also moderate to high recurrence rates. The limited options for FDA-approved PBC therapies necessitate the development of alternative approaches. Currently, a wide variety of experimental drugs exist targeting immunological and physiological aspects of PBC to suppress inflammation. Immunological therapies include drugs targeting immune molecules in the B cell and T cell response, and specific cytokines and chemokines implicated in inflammation. Drugs targeting bile acids are also noteworthy as bile acids can perpetuate hepatic inflammation and lead to fibrosis over time. These include FXR agonists, ASBT inhibitors, and PPAR agonists such as bezafibrate and fenofibrate. Nonetheless, many of these drugs can only delay disease progression and fail to enhance patients' quality of life. Nanomedicine shows great potential for treatment of autoimmune diseases, as it provides a new approach that focuses on tolerance induction rather than immunosuppression. Tolerogenic nanoparticles carrying immune-modifying agents can be engineered to safely and effectively target the antigen-specific immune response in autoimmune diseases. These may work well with PBC especially, given the anatomical features and immunological specificity of the disease. Nanobiological therapy is thus an area of highly promising research for future treatment of PBC.

The pathogenesis, models and therapeutic advances of primary biliary cholangitis

Primary biliary cholangitis (PBC) is an autoimmune disease characterized by the destruction of intrahepatic small bile ducts and the presence of antimitochondrial antibody (AMA), eventually progresses to liver fibrosis and cirrhosis. Genetic predisposition and environmental factors are involved in the occurrence of PBC, and the epitopes exposure and the imbalance of autoimmune tolerance are the last straw. The apoptosis of biliary epithelial cell (BEC) leads to the release of autoantigen epitopes, which activate the immune system, and the disorder of innate and adaptive immunity eventually leads to the start of disease. Animal models have unique advantages in investigating the pathogenesis and drug exploitation of PBC. Multiple models have been reported, and spontaneous model and induced model have been widely used in relevant research of PBC in recent years. Currently, the only drugs licensed for PBC are ursodesoxycholic acid (UDCA) and obeticholic acid (OCA). In the last few years, as the learned more about the pathogenesis of PBC, more and more targets have been discovered, and multiple targeted drugs are being in developed. In this review, the pathogenesis, murine models and treatment strategies of PBC were summarized, and the current research status was discussed to provide insights for the further study of PBC.

Insights Into the Involvement of Circular RNAs in Autoimmune Diseases

Circular RNAs (circRNAs) are single-stranded, endogenous, non-coding RNA (ncRNA) molecules formed by the backsplicing of messenger RNA (mRNA) precursors and have covalently closed circular structures without 5′-end caps and 3′-end polyadenylation [poly(A)] tails. CircRNAs are characterized by abundant species, stable structures, conserved sequences, cell- or tissue-specific expression, and widespread and stable presence in many organisms. Therefore, circRNAs can be used as biomarkers for the prediction, diagnosis, and treatment of a variety of diseases. Autoimmune diseases (AIDs) are caused by defects in immune tolerance or abnormal immune regulation, which leads to damage to host organs. Due to the complexity of the pathophysiological processes of AIDs, clinical therapeutics have been suboptimal. The emergence of circRNAs sheds new light on the treatment of AIDs. In particular, circRNAs mainly participate in the occurrence and development of AIDs by sponging targets. This review systematically explains the formation, function, mechanism, and characteristics of circRNAs in the context of AIDs. With a deeper understanding of the pathophysiological functions of circRNAs in the pathogenesis of AIDs, circRNAs may become reasonable, accurate, and effective biomarkers for the diagnosis and treatment of AIDs in the future.

Drug targeting CYP2E1 for the treatment of early-stage alcoholic steatohepatitis

Background and aims

Alcoholic steatohepatitis (ASH)—the inflammation of fatty liver—is caused by chronic alcohol consumption and represents one of the leading chronic liver diseases in Western Countries. ASH can lead to organ dysfunction or progress to hepatocellular carcinoma (HCC). Long-term alcohol abstinence reduces this probability and is the prerequisite for liver transplantation—the only effective therapy option at present. Elevated enzymatic activity of cytochrome P450 2E1 (CYP2E1) is known to be critically responsible for the development of ASH due to excessively high levels of reactive oxygen species (ROS) during metabolization of ethanol. Up to now, no rational drug discovery process was successfully initiated to target CYP2E1 for the treatment of ASH.

Methods

In this study, we applied a rational drug design concept to develop drug candidates (NCE) including preclinical studies.

Results

A new class of drug candidates was generated successfully. Two of the most promising small compounds named 12-Imidazolyl-1-dodecanol (abbr.: I-ol) and 1-Imidazolyldodecane (abbr.: I-an) were selected at the end of this process of drug discovery and developability. These new ω-imidazolyl-alkyl derivatives act as strong chimeric CYP2E1 inhibitors at a nanomolar range. They restore redox balance, reduce inflammation process as well as the fat content in the liver and rescue the physiological liver architecture of rats consuming continuously a high amount of alcohol.

Conclusions

Due to its oral application and therapeutic superiority over an off-label use of the hepatoprotector ursodeoxycholic acid (UDCA), this new class of inhibitors marks the first rational, pharmaceutical concept in long-term treatment of ASH.

Treatment response in primary biliary cholangitis: The role of autoimmune hepatitis features

INTRODUCTION AND AIM

Primary biliary cholangitis is a rare disease with scarce epidemiological data in Southern Europe. The authors aimed to evaluate treatment response in a cohort of patients.

MATERIALS AND METHODS

This retrospective observational single-centre study included patients with diagnostic criteria of primary biliary cholangitis. Data on disease presentation, laboratory results, treatment and clinical endpoints were collected and analyzed.

RESULTS

Fifty-three patients were included, 89% women, with mean age of 62±15 years at diagnosis. The majority was asymptomatic (49%), tested positive for antimitochondrial antibodies (96%) and had increased alkaline phosphatase (median=214U/L). 75% of the patients had liver histology and the majority were in Ludwig's stage I (42%). Autoimmune hepatitis (AIH) features were found in seven patients (13%). All were treated with ursodeoxycholic acid (UDCA) and 56% achieved biochemical response at one year; patients with AIH features exhibited steeper decreases in alkaline phosphatase (p=0.007) and reached the endpoint of 40% decrease in alkaline phosphatase more frequently (p=0.017).

CONCLUSION

In conclusion a significant proportion of patients failed to achieve an adequate response to UDCA treatment. The response rate of patients with AIH features was better, which could be related to a different phenotype or to the potential impact of immunosuppressive agents.

Regenerative Medicine of the Bile Duct: Beyond the Myth

Cholangiopathies are rare diseases of the bile duct with high mortality rates. The current treatment for cholangiopathies is liver transplantation, but there are significant obstacles including a shortage of donors and a high risk of complications. Currently, there is only one available medicine on the market targeting cholangiopathies, and the results have been inadequate in clinical therapy. To overcome these obstacles, many researchers have used human induced pluripotent stem cells (hPSC) as a source for cholangiocyte-like cell generation and have incorporated advances in bioprinting to create artificial bile ducts for implantation and transplantation. This has allowed the field to move dramatically forward in studies of biliary regenerative medicine. In this review, the authors provide an overview of cholangiocytes, the organogenesis of the bile duct, cholangiopathies, and the current treatment and advances that have been made that are opening new doors to the study of cholangiopathies.

Roles of circular RNAs in immune regulation and autoimmune diseases

Circular RNAs (circRNAs), as a novel class of endogenously expressed non-coding RNAs (ncRNAs), have a high stability and often present tissue-specific expression and evolutionary conservation. Emerging evidence has suggested that circRNAs play an essential role in complex human pathologies. Notably, circRNAs, important gene modulators in the immune system, are strongly associated with the occurrence and development of autoimmune diseases. Here, we focus on the roles of circRNAs in immune cells and immune regulation, highlighting their potential as biomarkers and biological functions in autoimmune diseases, such as systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), multiple sclerosis (MS), primary biliary cholangitis (PBC), and psoriasis, aiming at providing new insights into the diagnosis and therapy of these diseases.

Mesenchymal stem cells alleviate experimental autoimmune cholangitis through immunosuppression and cytoprotective function mediated by galectin-9

Background

Mesenchymal stem cells (MSCs) play an anti-inflammatory role by secreting certain bioactive molecules to exert their therapeutic effects for disease treatment. However, the underlying mechanism of MSCs in chronic autoimmune liver diseases—primary biliary cholangitis (PBC), for example—remains to be elucidated.

Methods

Human umbilical cord–derived MSCs (UC-MSCs) were injected intravenously into 2-octynoic acid coupled to bovine serum albumin (2OA-BSA)-induced autoimmune cholangitis mice. Serum levels of biomarkers and autoantibodies, histologic changes in the liver, diverse CD4⁺ T-cell subsets in different tissues, and chemokine activities were analyzed. Moreover, we investigated galectin-9 (Gal-9) expression and its function in UC-MSCs.

Results

In this study, UC-MSC transplantation (UC-MSCT) significantly ameliorated liver inflammation, primarily by diminishing T helper 1 (Th1) and Th17 responses as well as modifying liver chemokine activities in experimental autoimmune cholangitis mice. Mechanistically, UC-MSCs significantly repressed the proliferation of CD4⁺ T cells and suppressed the differentiation of Th1 and Th17 cells, which was likely dependent on Gal-9. Furthermore, the signal transducer and activator of transcription (STAT) and c-Jun N-terminal kinase (JNK) signaling pathways were involved in the production of Gal-9 in UC-MSCs.

Conclusions

These results suggest that Gal-9 contributes significantly to UC-MSC–mediated therapeutic effects and improve our understanding of the immunomodulatory mechanisms of MSCs in the treatment of PBC.

Electronic supplementary material

The online version of this article (10.1186/s13287-018-0979-x) contains supplementary material, which is available to authorized users.

The Genetics and Epigenetics of Primary Biliary Cholangitis

Both genetic background and environmental factors contribute to primary biliary cholangitis (PBC). Recent innovative technologies, such as genome-wide association studies, identified a remarkable number of susceptible nonhuman leukocyte antigen genes contributing to the development of PBC; however, they are primarily indicators of active immunologic responses commonly involved in autoimmune reactions. Thus, recent studies have focused on epigenetic mechanisms that would link genetic predisposition and environmental triggering factors. In PBC, methylation profiling and altered X chromosome architecture have been intensively explored in conjunction with a striking female predominance. Further, microRNAs have been found to be associated with the etiology of PBC.

Patterns of disease progression and incidence of complications in primary biliary cholangitis (PBC)

Clinical outcome for patients with primary biliary cholangitis (PBC) is dictated by development of cirrhosis, portal hypertension and its associated complications; including for some, a predisposition toward hepatocellular carcinoma. However rates of clinical progression vary, and accurately identifying disease course is of critical importance to patients, clinicians, as well as industry, who are committed to developing new effective and life-prolonging therapy as well as treating symptoms that appear disproportionate to underlying disease severity. Patients seek reassurance and guidance as to their own prognosis, and clinicians wish to confidently recognise those at highest risk of poor outcomes as equally as they strive to reassure individuals with a more favourable disease trajectory. International registries have facilitated a much greater knowledge of disease incidence and heterogeneity of presenting phenotypes. In so doing they highlight the opportunity to provide a more individualized estimate of the clinical course that patients experience, and have led to a renewed approach to risk stratification; both in terms of 'hard outcomes' and also disease-associated complications in PBC specifically.

Environmental basis of primary biliary cholangitis

Autoimmunity is a consequence of both genetic and environmental factors, occurring in genetically susceptible hosts with environmental triggers. While genome-wide association studies have revealed a number of susceptible genes contributing to etiology, the environmental triggers remain poorly understood. Primary biliary cholangitis, formally known as primary biliary cirrhosis, is considered a model autoimmune disease for which our group has extensively evaluated environmental factors involved in its etiology. Bacterial infection and xenobiotics have been proposed as candidate environmental factors that may explain tolerance breakdown and production of primary biliary cholangitis-specific antimitochondrial autoantibodies. Large-scale case-control studies have consistently detected an association of primary biliary cholangitis with urinary tract infections caused by Escherichia coli, as E. coli PDC-E2 is molecularly similar to human PDC-E2, the immunodominant target of AMAs. Another bacterium of interest is Novosphingobium aromaticivorans, a ubiquitous xenobiotic-metabolizing bacterium that produces lipoylated proteins, which are highly reactive with sera from primary biliary cholangitis patients. Regarding xenobiotics, case-control studies have suggested that frequent use of nail polish is associated with an increased susceptibility to primary biliary cholangitis. We found that 2-octynamide, the conjugate derived from 2-octynoic acid present in cosmetics, lipsticks, and some chewing gums, was unique in both its quantitative structure-activity relationship analysis and reactivity with primary biliary cholangitis sera. 2-nonyamide is another xenobiotic that also has the optimal chemical structure for xenobiotic modification of the PDC-E2 epitope, as demonstrated by the enhanced epitope recognition with AMA-positive PBC sera. Moreover, we found that C57BL/6 mice immunized with 2-octynoic acid-BSA possess many of the features characteristic to primary biliary cholangitis. Impact statement Autoimmunity is believed to develop in genetically susceptible hosts with triggers from the environment. Researchers have recently demonstrated that bacteria and xenobiotics commonly present in our environment are potential triggers of tolerance breakdown against autoantigens and autoimmunity, particularly in primary biliary cholangitis (PBC). The link between xenobiotics and PBC has been further confirmed with the establishment of PBC model mice by immunizing mice with xenobiotics.

Chronic Autoimmune Epithelitis in Sjögren's Syndrome and Primary Biliary Cholangitis: A Comprehensive Review

Within the spectrum of autoimmune diseases, Sjögren's syndrome and primary biliary cholangitis are exemplary and can be coined as chronic epithelitis based on their frequent coexistence in clinical practice and the highly specific immune-mediated injury of the small bile ducts and the exocrine glands. The pathogenic mechanisms underlying the diseases are similar, with apoptosis being the key element leading to organ-specific immune-mediated injury directed against the small bile ducts and salivary gland epithelia, respectively along with similar epidemiological features, such as female predominance and the age of onset in the fifth decade of life. Indeed, novel insights into the pathogenesis of the diseases have been obtained in recent years, including a better definition of the role of B and T cells, particularly Th17 cells, and the mechanisms of autoantibody-mediated tissue injury, with anti-mitochondrial antibodies and SS-A/SS-B being identified as specific for primary biliary cholangitis and Sjögren's syndrome, respectively. These findings have opened the possibility to new targeted therapies, but most clinical needs remain unmet, particularly from a therapeutic standpoint where options diverge, with bile acids being the predominant treatment strategy in primary biliary cholangitis and immunomodulators being used to treat Sjögren's syndrome. Here we provide a comprehensive review of the most recent findings on the pathogenesis, clinical manifestations and therapeutic options for Sjögren's syndrome and primary biliary cholangitis, respectively, while stressing the common traits between these conditions. Our cumulative hypothesis is that similarities outnumber differences and that this may prove advantageous towards a better management of patients.

Bile acids and intestinal microbiota in autoimmune cholestatic liver diseases

Autoimmune cholestatic liver diseases, including primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), are manifested as an impairment of normal bile flow and excessive accumulation of potentially toxic bile acids. Endogenous bile acids are involved in the pathogenesis and progression of cholestasis. Consequently, chronic cholestasis affects the expression of bile acid transporters and nuclear receptors, and results in liver injury. Several lines of evidence suggest that intestinal microbiota plays an important role in the etiopathogenesis of cholestatic liver diseases by regulating metabolism and immune responses. However, progression of the disease may also affect the composition of gut microbiota, which in turn exacerbates the progression of cholestasis. In addition, the interaction between intestinal microbiota and bile acids is not unidirectional. Bile acids can shape the gut microbiota community, and in turn, intestinal microbes are able to alter bile acid pool. In general, gut microbiota actively communicates with bile acids, and together play an important role in the pathogenesis of PBC and PSC. Targeting the link between bile acids and intestinal microbiota offers exciting new perspectives for the treatment of those cholestatic liver diseases. This review highlights current understanding of the interactions between bile acids and intestinal microbiota and their roles in autoimmune cholestatic liver diseases. Further, we postulate a bile acids-intestinal microbiota-cholestasis triangle in the pathogenesis of autoimmune cholestatic liver diseases and potential therapeutic strategies by targeting this triangle.

Seasonality and autoimmune diseases: The contribution of the four seasons to the mosaic of autoimmunity

Autoimmune diseases (ADs) are a heterogeneous groups of diseases that occur as a results of loss of tolerance to self antigens. While the etiopathogeneis remain obscure, different environmental factors were suggested to have a role in the development of autoimmunity, including infections, low vitamin D levels, UV radiation, and melatonin. Interestingly, such factors possess seasonal variation patterns that could influence disease development, severity and progression. Vitamin D levels which reach a nadir during late winter and early spring is correlated with increased disease activity, clinical severity as well as relapse rates in several disease entities including multiple sclerosis (MS), non-cutaneous flares of systemic lupus erythematosus (SLE), psoriasis, and rheumatoid arthritis (RA). Additionally, immunomodulatory actions of melatonin secretion ameliorate the severity of several ADs including MS and SLE. Melatonin levels are lowest during spring, a finding that correlates with the highest exacerbation rates of MS. Further, melatonin is postulated to be involved in the etiopathogenesis of inflammatory bowel diseases (IBD) through it influence on adhesion molecule and therefore transcription factor expression. Moreover, infections can mount to ADs through pro-inflammatory cytokine release and human antigen mimicry. Seasonal patterns of infectious diseases are correlated with the onset and exacerbation of ADs. During the winter, increased incidence of Epstein-Barr virus (EBV) infectious are associated with MS and SLE flares/onset respectively. In addition, higher Rotavirus infections during the winter precedes type 1 diabetes mellitus onset (T1DM). Moreover, Escherichia coli (E. coli) infection prior to primary biliary cirrhosis (PBC) and T1DM disease onset subsequent to Coxachievirus infections are seen to occur during late summer, a finding that correlate with infectious agents' pattern of seasonality. In this review, the effects of seasonality on the onset, relapses and activity of various ADs were discussed. Consideration of seasonal variation patterns of ADs can possibly provide clues to diseases pathogenesis and lead to development of new approaches in treatment and preventative care.

Toward solving the etiological mystery of primary biliary cholangitis

Primary biliary cholangitis (PBC) is considered a model autoimmune disease due to its signature anti‐mitochondrial antibody (AMA) autoantibody, female predominance, and relatively specific portal infiltration and cholestasis. The identification and cloning of the major mitochondrial autoantigens recognized by AMA have served as an immunologic platform to identify the earliest events involved in loss of tolerance. Despite the relatively high concordance rate in identical twins, genome‐wide association studies have not proven clinically useful and have led to suggestions of epigenetic events. To understand the natural history and etiology of PBC, several murine models have been developed, including spontaneous models, models induced by chemical xenobiotic immunization, and by “designer” mice with altered interferon metabolism. Herein, we describe five such models, including 1) NOD.c3c4 mice, 2) dominant negative form of transforming growth factor receptor type II mice, 3) interleukin‐2R α^−/− mice, 4) adenylate‐uridylate‐rich element Del^−/− mice, and 5) 2‐octynoic acid‐conjugated bovine serum albumin immunized mice. Individually there is no perfect murine model, but collectively the models point to loss of tolerance to PDC‐E2, the major mitochondrial autoantigen, as the earliest event that occurs before clinical disease is manifest. Although there is no direct association of AMA titer and PBC disease progression, it is noteworthy that the triad of PBC monocytes, biliary apotopes, and AMA leads to an intense proinflammatory cytokine burst. Further, the recurrence of PBC after liver transplantation indicates that, due to major histocompatibility complex restriction, disease activity must include not only adaptive immunity but also innate immune mechanisms. We postulate that successful treatment of PBC may require a personalized approach with therapies designed for different stages of disease. (Hepatology Communications 2017;1:275–287)

Why Doesn't Primary Biliary Cholangitis Respond to Immunosuppressive Medications?

Purpose of Review

The purpose of this review is to discuss reasons why immunosuppressive therapy so far failed in Primary Biliry Cholangitis.

Recent Findings

Even targeted immunosuppressive therapy seems ineffective or potentially harmful.

Summary

Bile acid-mediated cholangiocyte damage, facilitated by insufficient bicarbonate secretion, seems to attenuate the anti-inflammatory and anti-fibrotic actions of immunosuppressant and immunomodulatory drugs in a clinically significant way.

Treatment of PBC-A step forward

Recent years have seen a growing interest in PBC within the scientific community, healthcare providers and industries, coupled with great advances in the understanding of the molecular and genetic basis and the natural history of the disease. Several disease-modifying agents targeting the immune-mediated response and bile-acid therapies are at different stages of development, some with promising results. A new drug, obeticholic acid, has been recently registered in the US and Europe as a second-line treatment in refractory PBC. International cohort studies have highlighted a disease heterogeneity, and so the need to provide patients with a more personalised management based on their risk of disease progression. Major challenges remain the development of surrogate endpoints in clinical trials acceptable to regulatory authorities, in a disease with a relatively low rate of events; and the development of clinical tools for patient's risk stratification and selection of those with greatest potential benefit from second-line therapies.

Old and new treatments for primary biliary cholangitis

Primary biliary cholangitis (formerly primary biliary cirrhosis) is a rare progressive cholestatic liver disease, whose hallmark features include a persistently elevated alkaline phosphatase level, presence of anti-mitochondrial antibodies and characteristic histology. Since 1998, ursodeoxycholic acid (UDCA), a bile acid, has been the only available therapeutic agent. Primary biliary cholangitis is associated with the development of end-stage liver disease, increased morbidity and mortality. UDCA has been shown to improve serum biochemistries, histology and delay the need for liver transplantation. The clinical issue is that approximately 25%-40% of patients do not respond to this standard therapy. In recent years, many trials have investigated alternative and adjunctive treatments, leading to the recent approval of obeticholic acid, an analogue of chenodeoxycholic acid, which has shown significant and sustained reductions in alkaline phosphatase levels in combination with UDCA. Obeticholic acid has rapidly been embraced as a new agent to improve the biochemical profile in refractory patients, in addition to being approved for use as monotherapy in patients who cannot tolerate UDCA. There are several other studies and targets which are being investigated. This review is intended to highlight the benefits of UDCA, educate the reader on the newly available obeticholic acid, and to summarize the many ongoing trials and therapeutic targets being investigated in attempts to control and cure primary biliary cholangitis.

Regenerative Medicine and the Biliary Tree

Despite decades of basic research, biliary diseases remain prevalent, highly morbid, and notoriously difficult to treat. We have, however, dramatically increased our understanding of biliary developmental biology, cholangiocyte pathophysiology, and the endogenous mechanisms of biliary regeneration and repair. All of this complex and rapidly evolving knowledge coincides with an explosion of new technological advances in the area of regenerative medicine. New breakthroughs such as induced pluripotent stem cells and organoid culture are increasingly being applied to the biliary system; it is only a matter of time until new regenerative therapeutics for the cholangiopathies are unveiled. In this review, the authors integrate what is known about biliary development, regeneration, and repair, and link these conceptual advances to the technological breakthroughs that are collectively driving the emergence of a new global field in biliary regenerative medicine.

Macrophage Depletion Attenuates Extracellular Matrix Deposition and Ductular Reaction in a Mouse Model of Chronic Cholangiopathies

Chronic cholangiopathies, such as primary and secondary sclerosing cholangitis, are progressive disease entities, associated with periportal accumulation of inflammatory cells, encompassing monocytes and macrophages, peribiliary extracellular matrix (ECM) deposition and ductular reaction (DR). This study aimed to elucidate the relevance of macrophages in the progression of chronic cholangiopathies through macrophage depletion in a 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) mouse model. One group of mice received a single i.p. injection of Clodronate encapsulated liposomes (CLOLipo) at day 7 of a 14 day DDC treatment, while control animals were co-treated with PBSLipo instead. Mice were sacrificed after 7 or respectively 14 days of treatment for immunohistochemical assessment of macrophage recruitment (F4/80), ECM deposition (Sirius Red, Laminin) and DR (CK19). Macrophage depletion during a 14 day DDC treatment resulted in a significant inhibition of ECM deposition. Porto-lobular migration patterns of laminin-rich ECM and ductular structures were significantly attenuated and a progression of DR was effectively inhibited by macrophage depletion. CLOLipo co-treatment resulted in a confined DR to portal regions without amorphous cell clusters. This study suggests that therapeutic options selectively directed towards macrophages might represent a feasible treatment for chronic cholestatic liver diseases.