A global proteomic study identifies distinct pathological features of IgG4-related and primary sclerosing cholangitis

Regulatory T cells-related gene in primary sclerosing cholangitis: evidence from Mendelian randomization and transcriptome data

The present study utilized large-scale genome-wide association studies (GWAS) summary data (731 immune cell subtypes and three primary sclerosing cholangitis (PSC) GWAS datasets), meta-analysis, and two PSC transcriptome data to elucidate the pivotal role of Tregs proportion imbalance in the occurrence of PSC. Then, we employed weighted gene co-expression network analysis (WGCNA), differential analysis, and 107 combinations of 12 machine-learning algorithms to construct and validate an artificial intelligence-derived diagnostic model (Tregs classifier) according to the average area under curve (AUC) (0.959) in two cohorts. Quantitative real-time polymerase chain reaction (qRT-PCR) verified that compared to control, Akap10, Basp1, Dennd3, Plxnc1, and Tmco3 were significantly up-regulated in the PSC mice model yet the expression level of Klf13, and Scap was significantly lower. Furthermore, immune cell infiltration and functional enrichment analysis revealed significant associations of the hub Tregs-related gene with M2 macrophage, neutrophils, megakaryocyte-erythroid progenitor (MEP), natural killer T cell (NKT), and enrichment scores of the autophagic cell death, complement and coagulation cascades, metabolic disturbance, Fc gamma R-mediated phagocytosis, mitochondrial dysfunction, potentially mediating PSC onset. XGBoost algorithm and SHapley Additive exPlanations (SHAP) identified AKAP10 and KLF13 as optimal genes, which may be an important target for PSC.

Omics in IgG4-related disease

ABSTRACT

Research on IgG4-related disease (IgG4-RD), an autoimmune condition recognized to be a unique disease entity only two decades ago, has processed from describing patients' symptoms and signs to summarizing its critical pathological features, and further to investigating key pathogenic mechanisms. Challenges in gaining a better understanding of the disease, however, stem from its relative rarity-potentially attributed to underrecognition - and the absence of ideal experimental animal models. Recently, with the development of various high-throughput techniques, "omics" studies at different levels (particularly the single-cell omics) have shown promise in providing detailed molecular features of IgG4-RD. While, the application of omics approaches in IgG4-RD is still at an early stage. In this paper, we review the current progress of omics research in IgG4-RD and discuss the value of machine learning methods in analyzing the data with high dimensionality.

Fibrotic phenotype of IgG4-related disease

A prompt response to glucocorticoids is a clinical hallmark of IgG4-related disease. However, manifestations characterised by prominent tissue fibrosis on histological examination can be less responsive to glucocorticoid therapy than other types of IgG4-related disease. These manifestations include retroperitoneal fibrosis, fibrosing mediastinitis, Riedel thyroiditis, orbital pseudotumor, and hypertrophic pachymeningitis, among others. To explain this discrepancy, a preliminary distinction into proliferative and fibrotic phenotypes of IgG4-related disease has been proposed on the basis of clinical presentation, pathological features, and response to immunosuppressive therapy. Implications of this classification for patient management remain an important area of investigation. In this Series paper, we aim to dissect the pathophysiology of tissue fibrosis in IgG4-related disease and discuss how clinicians should approach the management of fibrotic manifestations of IgG4-related disease based on the most recent diagnostic and therapeutic developments.

Unraveling the actin cytoskeleton in the malignant transformation of cholangiocyte biology

Correct actin cytoskeleton organization is vital in the liver organ homeostasis and disease control. Rearrangements of the actin cytoskeleton may play a vital role in the bile duct cells cholangiocytes. An abnormal actin network leads to aberrant cell morphology, deregulated signaling networks and ultimately triggering the development of cholangiocarcinoma (CCA) and paving the route for cancer cell dissemination (metastasis). In this review, we will outline alterations of the actin cytoskeleton and the potential role of this dynamic network in initiating CCA, as well as regulating the course of this malignancy. Actin rearrangements not only occur because of signaling pathways, but also regulate and modify cellular signaling. This emphasizes the importance of the actin cytoskeleton itself as cause for aberrant signaling and in promoting tumorigenic phenotypes. We will highlight the impact of aberrant signaling networks on the actin cytoskeleton and its rearrangement as potential cause for CCA. Often, these exact mechanisms in CCA are limited understood and still must be elucidated. Indeed, focusing future research on how actin affects and regulates other signaling pathways may provide more insights into the mechanisms of CCA development, progression, and metastasis. Moreover, manipulation of the actin cytoskeleton organization highlights the potential for a novel therapeutic area.

The Role of B Cells in Adult and Paediatric Liver Injury

B lymphocytes are multitasking cells that direct the immune response by producing pro- or anti-inflammatory cytokines, by presenting processed antigen for T cell activation and co-stimulation, and by turning into antibody-secreting cells. These functions are important to control infection in the liver but can also exacerbate tissue damage and fibrosis as part of persistent inflammation that can lead to end stage disease requiring a transplant. In transplantation, immunosuppression increases the incidence of lymphoma and often this is of B cell origin. In this review we bring together information on liver B cell biology from different liver diseases, including alcohol-related and metabolic fatty liver disease, autoimmune hepatitis, primary biliary and primary sclerosing cholangitis, viral hepatitis and, in infants, biliary atresia. We also discuss the impact of B cell depletion therapy in the liver setting. Taken together, our analysis shows that B cells are important in the pathogenesis of liver diseases and that further research is necessary to fully characterise the human liver B cell compartment.

Steroid-responsive pancreatitides

Autoimmune pancreatitis has received considerable attention, especially due to the marked effect of corticosteroid therapy on its clinical course. Knowledge, especially regarding type 1 autoimmune pancreatitis, has significantly increased over the last decades, and despite significant differences in pathophysiology and outcomes, both type 1 and 2 autoimmune pancreatitis are still considered different types of the same disease. Some have proposed a different nomenclature reflecting these differences. Although the term steroid-responsive pancreatitides may be interpreted as synonymous to type 1 and 2 autoimmune pancreatitis, these are not the only pancreatic conditions that show a response to steroid therapy. Acute pancreatitis caused by vasculitis and connective tissue diseases and acute pancreatitis secondary to checkpoint inhibitors or programmed cell death receptor antibody-mediated blockage cancer therapy may also benefit from steroid treatment. This review presents current concepts on these disorders, aiming to increase awareness, analyze similarities and differences, and propose a new nomenclature that reflects their specific particularities, clustering them under the term “steroid-responsive pancreatitides”.

Pathological characteristics and diagnosis of IgG4-related disease

IgG4-related disease (IgG4-RD) has been accepted as a distinct entity in various fields. It is being increasingly diagnosed and treated in routine practice. However, difficulties are still associated with the diagnostic process. Serum IgG4 elevations and imaging studies are useful, but not entirely diagnostic for this condition. Therefore, a pathological examination still plays an important role. Three characteristic microscopic changes are dense lymphoplasmacytic infiltration, storiform fibrosis, and obliterative phlebitis. IgG4 immunostaining reveals many IgG4-positive plasma cells and an IgG4/IgG-positive cell ratio of more than 40%. In addition to the number and ratio of IgG4-positive plasma cells, the diffuse distribution of positive plasma cells needs to be confirmed because IgG4-positive plasma cells may focally aggregate in many other conditions. In small biopsy samples, it is important to recognize not only characteristic findings, but also microscopic changes that are unlikely to occur in IgG4-RD because the identification of the latter findings leads to the exclusion of this condition. Another challenging field regards the diagnosis of long-standing disease. Along with disease progression, inflammatory infiltrate decreases, while storiform fibrosis and obliterative phlebitis are suspected to persistently exist. Therefore, the recognition of the latter two findings will be a diagnostic clue. Given the general suspicion that IgG4-RD has recently been over-diagnosed, precise tissue examinations based on the proposed standards and close clinicopathological correlations are crucial.

Tumefactive Inflammatory Diseases of the Pancreas

Advances in the past two decades have resulted in the recognition of several tumefactive pancreatic lesions that, on histologic evaluation, show a varying combination of inflammation and fibrosis. Autoimmune pancreatitis, the prototypic tumefactive pancreatic fibroinflammatory lesion, is composed of two distinct diseases, type 1 autoimmune pancreatitis and the less common type 2 autoimmune pancreatitis. Although designated as autoimmune pancreatitis, the two diseases show little morphologic or pathogenic overlap. In type 1 disease, subsets of T lymphocytes (type 2 helper T cells, regulatory T cells, and T follicular helper 2 cells) are hypothesized to drive the inflammatory reaction. The B-cell response is characterized by an oligoclonal expansion of plasmablasts, with dominant clones that vary among patients and distinct clones that emerge at the time of relapse. Although the precise role of IgG4 in this condition remains uncertain, recent studies suggest that other IgG subclasses (eg, IgG1) may mediate the immune reactions, whereas IgG4 represents a response to dampen excessive inflammation. A recent study of type 2 autoimmune pancreatitis highlights the role of CXCL8 (alias IL-8), with duct epithelium and infiltrating T lymphocytes expressing this chemokine; the latter may contribute to the distinct form of neutrophilic inflammation in this disease. The review also highlights other forms of mass-forming chronic pancreatitis: follicular pancreatitis, groove pancreatitis, and those associated with rheumatologic diseases.

Advances in IgG4-related pancreatobiliary diseases

Autoimmune pancreatitis is an unusual form of pancreatitis that is histologically characterised by a massive infiltration of lymphocytes and IgG4-positive plasma cells and storiform fibrosis. The disease is recognised as a pancreatic manifestation of IgG4-related disease. IgG4-related sclerosing cholangitis is a biliary counterpart that is typically associated with autoimmune pancreatitis. Two parallel immunological responses are thought to underlie the pathophysiology of these diseases: a pro-inflammatory, tissue-destructive process and an anti-inflammatory feedback response, which probably relates to IgG4 production. These diseases should be differentiated from conditions with a similar presentation (eg, pancreatobiliary malignancy, primary sclerosing cholangitis) by comparison of serum IgG4 concentration, imaging features, other organ involvement, histology, and steroid responsiveness. Corticosteroids are first-line drugs, although rituximab has been shown to effectively deplete B cells in IgG4-related disease. Although the risk of relapse is high, no standardised treatment protocol exists for relapsed cases.

Gastrointestinal and Extra-Intestinal Manifestations of IgG4-Related Disease

IgG4-related disease (IgG4-RD) is a chronic relapsing multi-organ fibro-inflammatory syndrome of presumed autoimmune etiology. It is characterized by increased serum levels of IgG4 and tissue infiltration by IgG4⁺ cells. Increased titers of autoantibodies against a spectrum of self-antigens and response to steroids have led to its characterization as an autoimmune disease. However, the pathognomonic antigens probably differ among manifestations, and different antigens or autoantibodies produce similar immune reactions in different organs. Little is known about the pathogenic effects, if any, of serum IgG4 or IgG4⁺ plasma cells in tissues. Despite several animal models of the disease, none truly recapitulates human IgG4-RD. Histologic analyses of tissues from patients with IgG4-RD reveal a dense lymphoplasmacytic infiltrate rich in IgG4⁺ plasma cells, storiform fibrosis, and obliterative phlebitis, although these features vary among organs. Typical presentation and imaging findings include mass-forming synchronous or metachronous lesions in almost any organ, but most commonly in the pancreas, bile duct, retroperitoneum, kidneys, lungs, salivary and lacrimal glands, orbit, and lymph nodes. In all organs, inflammation can be reduced by corticosteroids and drugs that deplete B cells, such as rituximab. Patients with IgG4-RD have relapses that respond to primary therapy. Intense fibrosis accompanies the inflammatory response, leading to permanent organ damage and insufficiency. Death from IgG4-RD is rare. IgG4-RD is a multi-organ disease with predominant pancreatico-biliary involvement. Despite its relapsing-remitting course, patients have an excellent prognosis.

Modern work-up and extended resection in perihilar cholangiocarcinoma: the AMC experience

AIM

Perihilar cholangiocarcinoma (PHC) is a challenging disease and requires aggressive surgical treatment in order to achieve curation. The assessment and work-up of patients with presumed PHC is multidisciplinary, complex and requires extensive experience. The aim of this paper is to review current aspects of diagnosis, preoperative work-up and extended resection in patients with PHC from the perspective of our own institutional experience with this complex tumor.

METHODS

We provided a review of applied modalities in the diagnosis and work-up of PHC according to current literature. All patients with presumed PHC in our center between 2000 and 2016 were identified and described. The types of resection, surgical techniques and outcomes were analyzed.

RESULTS AND CONCLUSION

Upcoming diagnostic modalities such as Spyglass and combinations of serum biomarkers and molecular markers have potential to decrease the rate of misdiagnosis of benign, inflammatory disease. Assessment of liver function with hepatobiliary scintigraphy provides better information on the future remnant liver (FRL) than volume alone. The selective use of staging laparoscopy is advisable to avoid futile laparotomies. In patients requiring extended resection, selective preoperative biliary drainage is mandatory in cholangitis and when FRL is small (< 50%). Preoperative portal vein embolization (PVE) is used when FRL volume is less than 40% and optionally includes the left portal vein branches to segment 4. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) as alternative to PVE is not recommended in PHC. N2 positive lymph nodes preclude long-term survival. The benefit of unconditional en bloc resection of the portal vein bifurcation is uncertain. Along these lines, an aggressive surgical approach encompassing extended liver resection including segment 1, regional lymphadenectomy and conditional portal venous resection translates into favorable long-term survival.

IgG4-related sclerosing cholangitis: all we need to know

Our knowledge and experience of IgG4-related sclerosing cholangitis (ISC) have expanded in the last decade. ISC is one of the common organ manifestations of IgG4-related disease (IgG4-RD); approximately 60 % of patients with this systemic condition have ISC in the proximal and/or distal bile ducts. ISC needs to be discriminated from primary sclerosing cholangitis, cholangiocarcinoma, and other rare forms of lymphoplasmacytic cholangiopathy (e.g., follicular cholangitis and sclerosing cholangitis with granulocytic epithelial lesions). Its diagnosis requires a multidisciplinary approach, in which serology, histology, and imaging play crucial roles. Treatments with high-dose corticosteroids typically lead to the rapid and consistent induction of disease remission. Another promising therapeutic approach is B-cell depletion with rituximab. Although disease relapse is relatively common, provided that appropriate treatments are administered, ISC is considered a "benign" disease with a low risk of liver failure and biliary malignancy. Its molecular pathology is characterized by Th2-dominant immune reactions, regulatory T-cell activation, and CCL1-CCR8 interactions. Particular subsets of B cells such as plasmablasts and regulatory B cells also expand. A recent global proteomic study demonstrated that three significantly activated immunological cascades in ISC were all B-cell- or immunoglobulin-related (Fc-gamma receptor-mediated phagocytosis, B-cell receptor signaling pathway, and Fc-epsilon receptor I signaling pathway), suggesting the crucial roles of B cells in the underlying immune reactions. Despite the expansion of our knowledge of the pathophysiology of ISC, the exact role of IgG4 remains unclear. A better understanding of its immunopathology will offer some potential drug targets for this emerging biliary disease.

The Histopathology of IgG4-Related Disease

IgG4-related disease is a multi-organ immune-mediated chronic fibroinflammatory condition characterized by elevated serum IgG4 concentrations, tumefaction, and tissue infiltration by IgG4-positive plasma cells. The exact etiology of IgG4-related disease remains unclear with no known role of the IgG4 molecule itself being identified. Although the pancreas and salivary glands are the main organs affected, the involvement of other organs has also been reported. This multi-organ disease mimics a large number of malignant, infectious, and inflammatory disorders; therefore, a prompt differential diagnosis is important for selecting the right therapeutic strategy. Early steroid therapy assists in preventing tissue fibrosis, parenchymal extinction, and severe functional impairments in the affected organs. The definitive and prompt diagnosis of IgG4-related disease requires both histopathological confirmation and clinicopathological correlations. A histopathological examination is mandatory to exclude neoplastic or inflammatory conditions that mimic IgG4-related disease. The histological changes that occur are basically similar in any organ manifestation, with several site-specific findings being recognized. This chapter summarizes general rules for the pathological examination of IgG4-related disease, as well as the histopathological features and differential diagnoses of major organ manifestations.