The biliary tree--a reservoir of multipotent stem cells

ER stress signaling at the interphase between MASH and HCC

HCC is the most frequent primary liver cancer with an extremely poor prognosis and often develops on preset of chronic liver diseases. Major risk factors for HCC include metabolic dysfunction-associated steatohepatitis, a complex multifactorial condition associated with abnormal endoplasmic reticulum (ER) proteostasis. To cope with ER stress, the unfolded protein response engages adaptive reactions to restore the secretory capacity of the cell. Recent advances revealed that ER stress signaling plays a critical role in HCC progression. Here, we propose that chronic ER stress is a common transversal factor contributing to the transition from liver disease (risk factor) to HCC. Interventional strategies to target the unfolded protein response in HCC, such as cancer therapy, are also discussed.

Mechanism and endoscopic-treatment-induced evolution of biliary non-anastomotic stricture after liver transplantation revealed by single-cell RNA sequencing

BACKGROUND

Biliary complications, especially non-anastomotic stricture (NAS), are the main complications after liver transplantation. Insufficient sampling and no recognized animal models obstruct the investigation. Thus, the mechanisms and alterations that occur during endoscopic treatment (ET) of NAS remain unclear.

METHODS

Samples were obtained with endoscopic forceps from the hilar bile ducts of NAS patients receiving continuous biliary stent implantation after diagnosis. Retrospective analysis of multiple studies indicated that the duration of ET for NAS was approximately 1-2 years. Thus, we divided the patients into short-term treatment (STT) and long-term treatment (LTT) groups based on durations of less or more than 1 year. Samples were subjected to single-cell RNA sequencing. Transcriptomic differences between STT and normal groups were defined as the NAS mechanism. Similarly, alterations from STT to LTT groups were regarded as endoscopic-treatment-induced evolution.

RESULTS

In NAS, inflammation and immune-related pathways were upregulated in different cell types, with nonimmune cells showing hypoxia pathway upregulation and immune cells showing ATP metabolism pathway upregulation, indicating heterogeneity. We confirmed a reduction in bile acid metabolism-related SPP1+ epithelial cells in NAS. Increases in proinflammatory and profibrotic fibroblast subclusters indicated fibrotic progression in NAS. Furthermore, immune disorders in NAS were exacerbated by an increase in plasma cells and dysfunction of NK and NKT cells. ET downregulated multicellular immune and inflammatory responses and restored epithelial and endothelial cell proportions.

CONCLUSIONS

This study reveals the pathophysiological and genetic mechanisms and evolution of NAS induced by ET, thereby providing preventive and therapeutic insights into NAS.

HIGHLIGHTS

For the first time, single-cell transcriptome sequencing was performed on the bile ducts of patients with biliary complications. scRNA-seq analysis revealed distinct changes in the proportion and phenotype of multiple cell types during Nonanastomotic stricture (NAS) and endoscopic treatment. A reduction in bile acid metabolism-related SPP1+ epithelial cells and VEGFA+ endothelial cells, along with explosive infiltration of plasma cells and dysfunction of T and NK cells in NAS patients. SPP1+ macrophages and BST2+ T cells might serve as a surrogate marker for predicting endoscopic treatment.

Biliary stem cells in health and cholangiopathies and cholangiocarcinoma

PURPOSE OF REVIEW

This review discusses evidence regarding progenitor populations of the biliary tree in the tissue regeneration and homeostasis, and the pathobiology of cholangiopathies and malignancies.

RECENT FINDINGS

In embryogenesis biliary multipotent progenitor subpopulation contributes cells not only to the pancreas and gall bladder but also to the liver. Cells equipped with a constellation of markers suggestive of the primitive endodermal phenotype exist in the peribiliary glands, the bile duct glands, of the intra- and extrahepatic bile ducts. These cells are able to be isolated and cultured easily, which demonstrates the persistence of a stable phenotype during in vitro expansion, the ability to self-renew in vitro, and the ability to differentiate between hepatocyte and biliary and pancreatic islet fates.

SUMMARY

In normal human livers, stem/progenitors cells are mostly restricted in two distinct niches, which are the bile ductules/canals of Hering and the peribiliary glands (PBGs) present inside the wall of large intrahepatic bile ducts. The existence of a network of stem/progenitor cell niches within the liver and along the entire biliary tree inform a patho-biological-based translational approach to biliary diseases and cholangiocarcinoma since it poses the basis to understand biliary regeneration after extensive or chronic injuries and progression to fibrosis and cancer.

Heterogeneous murine peribiliary glands orchestrate compartmentalized epithelial renewal

The extrahepatic branches of the biliary tree have glands that connect to the surface epithelium through narrow pits. The duct epithelia undergo homeostatic renewal, yet the identity and multiplicity of cells that maintain this tissue is unknown. Using marker-free and targeted clonal fate mapping in mice, we provide evidence that the extrahepatic bile duct is compartmentalized. Pit cholangiocytes of extramural glands renewed the surface epithelium, whereas basally oriented cholangiocytes maintained the gland itself. In contrast, basally positioned cholangiocytes replenished the surface epithelium in mural glands. Single-cell sequencing identified genes enriched in the base and surface epithelial populations, with trajectory analysis showing graded gene expression between these compartments. Epithelia were plastic, changing cellular identity upon fasting and refeeding. Gain of canonical Wnt signaling caused basal cell expansion, gastric chief cell marker expression, and a decrease in surface epithelial markers. Our results identify the cellular hierarchy governing extrahepatic biliary epithelial renewal.

Hedgehog Signaling: Implications in Liver Pathophysiology

The purpose of this review is to summarize current knowledge about the role of the Hedgehog signaling pathway in liver homeostasis and disease. Hedgehog is a morphogenic signaling pathway that is active in development. In most healthy tissues, pathway activity is restricted to stem and/or stromal cell compartments, where it enables stem cell self-renewal and tissue homeostasis. Aberrant over-activation of Hedgehog signaling occurs in many cancers, including hepatocellular and cholangio-carcinoma. The pathway is also activated transiently in stromal cells of injured tissues and orchestrates normal wound healing responses, including inflammation, vascular remodeling, and fibrogenesis. In liver, sustained Hedgehog signaling in stromal cells plays a major role in the pathogenesis of cirrhosis. Hedgehog signaling was thought to be silenced in healthy hepatocytes. However, recent studies show that targeted disruption of the pathway in hepatocytes dysregulates lipid, cholesterol, and bile acid metabolism, and promotes hepatic lipotoxicity, insulin resistance, and senescence. Hepatocytes that lack Hedgehog activity also produce a secretome that activates Hedgehog signaling in cholangiocytes and neighboring stromal cells to induce inflammatory and fibrogenic wound healing responses that drive progressive fibrosis. In conclusion, Hedgehog signaling must be precisely controlled in adult liver cells to maintain liver health.

Fibrolamellar carcinomas-growth arrested by paracrine signals complexed with synthesized 3-O sulfated heparan sulfate oligosaccharides

Fibrolamellar carcinomas (FLCs), lethal tumors occurring in children to young adults, have genetic signatures implicating derivation from biliary tree stem cell (BTSC) subpopulations, co-hepato/pancreatic stem cells, involved in hepatic and pancreatic regeneration. FLCs and BTSCs express pluripotency genes, endodermal transcription factors, and stem cell surface, cytoplasmic and proliferation biomarkers. The FLC-PDX model, FLC-TD-2010, is driven ex vivo to express pancreatic acinar traits, hypothesized responsible for this model's propensity for enzymatic degradation of cultures. A stable ex vivo model of FLC-TD-2010 was achieved using organoids in serum-free Kubota's Medium (KM) supplemented with 0.1% hyaluronans (KM/HA). Heparins (10 ng/ml) caused slow expansion of organoids with doubling times of ∼7-9 days. Spheroids, organoids depleted of mesenchymal cells, survived indefinitely in KM/HA in a state of growth arrest for more than 2 months. Expansion was restored with FLCs co-cultured with mesenchymal cell precursors in a ratio of 3:7, implicating paracrine signaling. Signals identified included FGFs, VEGFs, EGFs, Wnts, and others, produced by associated stellate and endothelial cell precursors. Fifty-three, unique heparan sulfate (HS) oligosaccharides were synthesized, assessed for formation of high affinity complexes with paracrine signals, and each complex screened for biological activity(ies) on organoids. Ten distinct HS-oligosaccharides, all 10-12 mers or larger, and in specific paracrine signal complexes elicited particular biological responses. Of note, complexes of paracrine signals and 3-O sulfated HS-oligosaccharides elicited slowed growth, and with Wnt3a, elicited growth arrest of organoids for months. If future efforts are used to prepare HS-oligosaccharides resistant to breakdown in vivo, then [paracrine signal-HS-oligosaccharide] complexes are potential therapeutic agents for clinical treatments of FLCs, an exciting prospect for a deadly disease.

Differential risk of 23 site-specific incident cancers and cancer-related mortality among patients with metabolic dysfunction-associated fatty liver disease: a population-based cohort study with 9.7 million Korean subjects

INTRODUCTION

Although an association between metabolic dysfunction-associated fatty liver disease (MAFLD) and cardiovascular disease or overall mortality has been reported, it is unclear whether there is an association between MAFLD and cancer incidence or mortality. We aimed to investigate the differential risk of all- and site-specific cancer incidence and mortality according to MAFLD subgroups categorized by additional etiologies of liver disease.

METHODS

Using the Korean National Health Insurance Service database, we stratified the participants into three groups: (1) single-etiology MAFLD (S-MAFLD) or MAFLD of pure metabolic origin; (2) mixed-etiology MAFLD (M-MAFLD) or MAFLD with additional etiological factor(s) (i.e., concomitant liver diseases and/or heavy alcohol consumption); and (3) non-MAFLD. Hepatic steatosis and fibrosis were defined using the fatty liver index and the BARD score, respectively. Cox proportional hazards regression was performed to estimate the risk of cancer events.

RESULTS

Among the 9,718,182 participants, the prevalence of S-MAFLD and M-MAFLD was 29.2% and 6.7%, respectively. During the median 8.3 years of follow-up, 510,330 (5.3%) individuals were newly diagnosed with cancer, and 122,774 (1.3%) cancer-related deaths occurred among the entire cohort. Compared with the non-MAFLD group, the risk of all-cancer incidence and mortality was slightly higher among patients in the S-MAFLD group (incidence, adjusted hazard ratio [aHR] = 1.03; 95% confidence interval [CI]: 1.02-1.04; mortality, aHR = 1.06; 95% CI: 1.04-1.08) and highest among patients with M-MAFLD group (incidence, aHR = 1.31; 95% CI: 1.29-1.32; mortality, aHR = 1.45; 95% CI: 1.42-1.48, respectively). The M-MAFLD with fibrosis group (BARD score ≥ 2) showed the highest relative risk of all-cancer incidence (aHR = 1.38, 95% CI = 1.36-1.39), followed by the M-MAFLD without fibrosis group (aHR = 1.09, 95% CI = 1.06-1.11). Similar trends were observed for cancer-related mortality.

CONCLUSIONS

MAFLD classification, by applying additional etiologies other than pure metabolic origin, can be used to identify a subgroup of patients with poor cancer-related outcomes.

A postnatal network of co-hepato/pancreatic stem/progenitors in the biliary trees of pigs and humans

A network of co-hepato/pancreatic stem/progenitors exists in pigs and humans in Brunner's Glands in the submucosa of the duodenum, in peribiliary glands (PBGs) of intrahepatic and extrahepatic biliary trees, and in pancreatic duct glands (PDGs) of intrapancreatic biliary trees, collectively supporting hepatic and pancreatic regeneration postnatally. The network is found in humans postnatally throughout life and, so far, has been demonstrated in pigs postnatally at least through to young adulthood. These stem/progenitors in vivo in pigs are in highest numbers in Brunner's Glands and in PDGs nearest the duodenum, and in humans are in Brunner's Glands and in PBGs in the hepato/pancreatic common duct, a duct missing postnatally in pigs. Elsewhere in PDGs in pigs and in all PDGs in humans are only committed unipotent or bipotent progenitors. Stem/progenitors have genetic signatures in liver/pancreas-related RNA-seq data based on correlation, hierarchical clustering, differential gene expression and principal component analyses (PCA). Gene expression includes representative traits of pluripotency genes (SOX2, OCT4), endodermal transcription factors (e.g. SOX9, SOX17, PDX1), other stem cell traits (e.g. NCAM, CD44, sodium iodide symporter or NIS), and proliferation biomarkers (Ki67). Hepato/pancreatic multipotentiality was demonstrated by the stem/progenitors' responses under distinct ex vivo conditions or in vivo when patch grafted as organoids onto the liver versus the pancreas. Therefore, pigs are logical hosts for translational/preclinical studies for cell therapies with these stem/progenitors for hepatic and pancreatic dysfunctions.

Promising Highly Targeted Therapies for Cholangiocarcinoma: A Review and Future Perspectives

To overcome the poor prognosis of cholangiocarcinoma (CCA), highly targeted therapies, such as antibody-drug conjugates (ADCs), photodynamic therapy (PDT) with/without systemic chemotherapy, and experimental photoimmunotherapy (PIT), have been developed. Three preclinical trials have investigated the use of ADCs targeting specific antigens, namely HER2, MUC1, and glypican-1 (GPC1), for CCA. Trastuzumab emtansine demonstrated higher antiproliferative activity in CCA cells expressing higher levels of HER2. Similarly, "staphylococcal enterotoxin A-MUC1 antibody" and "anti-GPC1 antibody-monomethyl auristatin F" conjugates showed anticancer activity. PDT is effective in areas where appropriate photosensitizers and light coexist. Its mechanism involves photosensitizer excitation and subsequent reactive oxygen species production in cancer cells upon irradiation. Hematoporphyrin derivatives, temoporfin, phthalocyanine-4, talaporfin, and chlorine e6 derivatives have mainly been used clinically and preclinically in bile duct cancer. Currently, new forms of photosensitizers with nanotechnology and novel irradiation catheters are being developed. PIT is the most novel anti-cancer therapy developed in 2011 that selectively kills targeted cancer cells using a unique photosensitizer called "IR700" conjugated with an antibody specific for cancer cells. PIT is currently in the early stages of development for identifying appropriate CCA cell targets and irradiation devices. Future human and artificial intelligence collaboration has potential for overcoming challenges related to identifying universal CCA cell targets. This could pave the way for highly targeted therapies for CCA, such as ADC, PDT, and PIT.

Liver cell therapies: cellular sources and grafting strategies

The liver has a complex cellular composition and a remarkable regenerative capacity. The primary cell types in the liver are two parenchymal cell populations, hepatocytes and cholangiocytes, that perform most of the functions of the liver and that are helped through interactions with non-parenchymal cell types comprising stellate cells, endothelia and various hemopoietic cell populations. The regulation of the cells in the liver is mediated by an insoluble complex of proteins and carbohydrates, the extracellular matrix, working synergistically with soluble paracrine and systemic signals. In recent years, with the rapid development of genetic sequencing technologies, research on the liver's cellular composition and its regulatory mechanisms during various conditions has been extensively explored. Meanwhile breakthroughs in strategies for cell transplantation are enabling a future in which there can be a rescue of patients with end-stage liver diseases, offering potential solutions to the chronic shortage of livers and alternatives to liver transplantation. This review will focus on the cellular mechanisms of liver homeostasis and how to select ideal sources of cells to be transplanted to achieve liver regeneration and repair. Recent advances are summarized for promoting the treatment of end-stage liver diseases by forms of cell transplantation that now include grafting strategies.

β-adrenergic receptor agonist promotes ductular expansion during 3,5-diethoxycarbonyl-1,4-dihydrocollidine-induced chronic liver injury

Intrahepatic nerves are involved in the regulation of metabolic reactions and hepatocyte-based regeneration after surgical resection, although their contribution to chronic liver injury remains unknown. Given that intrahepatic nerves are abundant in the periportal tissue, they may be correlated also with cholangiocyte-based regeneration. Here we demonstrate that isoproterenol (ISO), a β-adrenergic receptor agonist, promoted ductular expansion induced by 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) in vivo. Immunofluorescence analysis shows that nerve fibers positive for tyrosine hydroxylase form synaptophysin-positive nerve endings on epithelial cell adhesion molecule-positive (EpCAM⁺) cholangiocytes as well as on Thy1⁺ periportal mesenchymal cells (PMCs) that surround bile ducts, suggesting that the intrahepatic biliary tissue are targeted by sympathetic nerves. In vitro analyses indicate that ISO directly increases cAMP levels in cholangiocytes and PMCs. Mechanistically, ISO expands the lumen of cholangiocyte organoids, resulting in promotion of cholangiocyte proliferation, whereas it increases expression of fibroblast growth factor 7, a growth factor for cholangiocytes, in PMCs. Taken together, the results indicate that intrahepatic sympathetic nerves regulate remodeling of bile ducts during DDC-injury by the activation of β-adrenergic receptors on cholangiocytes and PMCs.

Role of the Gut–Liver Axis in the Pathobiology of Cholangiopathies: Basic and Clinical Evidence

The “Gut–Liver Axis” refers to the physiological bidirectional interplay between the gut and its microbiota and the liver which, in health, occurs thanks to a condition of immune tolerance. In recent years, several studies have shown that, in case of a change in gut bacterial homeostasis or impairment of intestinal barrier functions, cholangiocytes, which are the epithelial cells lining the bile ducts, activate innate immune responses against gut-derived microorganisms or bacterial products that reach the liver via enterohepatic circulation. Intestinal dysbiosis or impaired intestinal barrier functions cause cholangiocytes to be exposed to an increasing amount of microorganisms that can reactivate inflammatory responses, thus inducing the onset of liver fibrosis. The present review focuses on the role of the gut–liver axis in the pathogenesis of cholangiopathies.

Poor-prognosis molecular subtypes in adenocarcinomas of pancreato-biliary and gynecological origin: A systematic review

Pancreato-biliary and gynecological adenocarcinomas need better tools to predict clinical outcome. Potential prognostic mesenchymal(-like) transcriptome-based subtypes have been identified in these cancers. In this systematic review, we include studies into molecular subtyping and summarize biological and clinical features of the subtypes within and across sites of origin, searching for suggestions to improve classification and prognostication. PubMed and Embase were searched for original research articles describing potential mesenchymal(-like) mRNA-based subtypes in pancreato-biliary or gynecological adenocarcinomas. Studies limited to supervised clustering were excluded. Fourty-four studies, discussing cholangiocarcinomas, gallbladder, ampullary, pancreatic, ovarian, and endometrial adenocarcinomas were included. There was overlap in molecular and clinical features in mesenchymal(-like) subtypes across all adenocarcinomas. Approaches including microdissection were more likely to identify prognosis-associating subtypes. To conclude, molecular subtypes in pancreato-biliary and gynecological adenocarcinomas share biological and clinical characteristics. Furthermore, separation of stromal and epithelial signals should be applied in future studies into biliary and gynecological adenocarcinomas.

Development of extrahepatic bile ducts and mechanisms of tumorigenesis: Lessons from mouse models

The biliary system is a highly branched tubular network consisting of intrahepatic bile ducts (IHBDs) and extrahepatic bile ducts (EHBDs). IHBDs are derived from hepatic progenitor cells, while EHBDs originate directly from the endoderm through a separate branching morphogenetic process. Traits that are important for cancer are often found to overlap in developmental and other processes. Therefore, it has been suggested that intrahepatic cholangiocarcinomas (iCCAs) and extrahepatic cholangiocarcinomas (eCCAs) have different developmental mechanisms. While much evidence is being gathered on the mechanism of iCCAs, the evidence for eCCA is still very limited. The main reason for this is that there are very few appropriate animal models for eCCA. We can gain important insights from these animal models, particularly genetically engineered mouse models (GEMMs). GEMMs are immunocompetent and mimic human CCA subtypes with a specific mutational pattern, allowing the development of precancerous lesions, that is, biliary intraepithelial neoplasia (BilIN) and intraductal papillary neoplasm of the bile duct (IPNB). This review provides a summary of the pathogenesis and mechanisms of eCCA that can be revealed by GEMMs. Furthermore, we discuss several clinical questions, such as whether BilIN and IPNB really become malignant, whether the peribiliary gland is the origin of eCCAs, and others.

Pitfalls and promises of bile duct alternatives: A narrative review

Biliodigestive anastomosis between the extrahepatic bile duct and the intestine for bile duct disease is a gastrointestinal reconstruction that abolishes duodenal papilla function and frequently causes retrograde cholangitis. This chronic inflammation can cause liver dysfunction, liver abscess, and even bile duct cancer. Although research has been conducted for over 100 years to directly repair bile duct defects with alternatives, no bile duct substitute (BDS) has been developed. This narrative review confirms our understanding of why bile duct alternatives have not been developed and explains the clinical applicability of BDSs in the near future. We searched the PubMed electronic database to identify studies conducted to develop BDSs until December 2021 and identified studies in English. Two independent reviewers reviewed studies on large animals with 8 or more cases. Four types of BDSs prevail: Autologous tissue, non-bioabsorbable material, bioabsorbable material, and others (decellularized tissue, 3D-printed structures, etc.). In most studies, BDSs failed due to obstruction of the lumen or stenosis of the anastomosis with the native bile duct. BDS has not been developed primarily because control of bile duct wound healing and regeneration has not been elucidated. A BDS expected to be clinically applied in the near future incorporates a bioabsorbable material that allows for regeneration of the bile duct outside the BDS.

Patch grafting of organoids of stem/progenitors into solid organs can correct genetic-based disease states

Patch grafting, a novel strategy for transplantation of stem/progenitor organoids into porcine livers, has been found successful also for organoid transplantation into other normal or diseased solid organs in pigs and mice. Each organoid contained ∼100 cells comprised of biliary tree stem cells (BTSCs), co-hepato/pancreatic stem/progenitors, and partnered with early lineage stage mesenchymal cells (ELSMCs), angioblasts and precursors to endothelia and stellate cells. Patch grafting enabled transplantation into livers or pancreases of ≥108th (pigs) or ≥106th-7th (mice) organoids/patch. Graft conditions fostered expression of multiple matrix-metalloproteinases (MMPs), especially secretory isoforms, resulting in transient loss of the organ's matrix-dictated histological features, including organ capsules, and correlated with rapid integration within a week of organoids throughout the organs and without emboli or ectopic cell distribution. Secondarily, within another week, there was clearance of graft biomaterials, followed by muted expression of MMPs, restoration of matrix-dictated histology, and maturation of donor cells to functional adult fates. The ability of patch grafts of organoids to rescue hosts from genetic-based disease states was demonstrated with grafts of BTSC/ELSMC organoids on livers, able to rescue NRG/FAH-KO mice from type I tyrosinemia, a disease caused by absence of fumaryl acetoacetate hydrolase. With the same grafts, if on pancreas, they were able to rescue NRG/Akita mice from type I diabetes, caused by a mutation in the insulin 2 gene. The potential of patch grafting for cell therapies for solid organs now requires translational studies to enable its adaptation and uses for clinical programs.

Cellular Homeostasis and Repair in the Biliary Tree

During biliary tree homeostasis, BECs are largely in a quiescent state and their turnover is slow for maintaining normal tissue homeostasis. BTSCs continually replenish new BECs in the luminal surface of EHBDs. In response to various types of biliary injuries, distinct cellular sources, including HPCs, BTSCs, hepatocytes, and BECs, repair or regenerate the injured bile duct. BEC, biliary epithelial cell; BTSC, biliary tree stem/progenitor cell; EHBD, extrahepatic bile ducts; HPC, hepatic progenitor cell.The biliary tree comprises intrahepatic bile ducts and extrahepatic bile ducts lined with epithelial cells known as biliary epithelial cells (BECs). BECs are a common target of various cholangiopathies for which there is an unmet therapeutic need in clinical hepatology. The repair and regeneration of biliary tissue may potentially restore the normal architecture and function of the biliary tree. Hence, the repair and regeneration process in detail, including the replication of existing BECs, expansion and differentiation of the hepatic progenitor cells and biliary tree stem/progenitor cells, and transdifferentiation of the hepatocytes, should be understood. In this paper, we review biliary tree homeostasis, repair, and regeneration and discuss the feasibility of regenerative therapy strategies for cholangiopathy treatment.

A framework for fibrolamellar carcinoma research and clinical trials

Fibrolamellar carcinoma (FLC), a rare, lethal hepatic cancer, occurs primarily in adolescents and young adults. Unlike hepatocellular carcinoma, FLC has no known association with viral, metabolic or chemical agents that cause cirrhosis. Currently, surgical resection is the only treatment demonstrated to achieve cure, and no standard of care exists for systemic therapy. Progress in FLC research illuminates a transition from an obscure cancer to one for which an interactive community seems poised to uncover fundamental mechanisms and initiate translation towards novel therapies. In this Roadmap, we review advances since the seminal discovery in 2014 that nearly all FLC tumours express a signature oncogene (DNAJB1-PRKACA) encoding a fusion protein (DNAJ-PKAc) in which the J-domain of a heat shock protein 40 (HSP40) co-chaperone replaces an amino-terminal segment of the catalytic subunit of the cyclic AMP-dependent protein kinase (PKA). Important gains include increased understanding of oncogenic pathways driven by DNAJ-PKAc; identification of potential therapeutic targets; development of research models; elucidation of immune mechanisms with potential for the development of immunotherapies; and completion of the first multicentre clinical trials of targeted therapy for FLC. In each of these key areas we propose a Roadmap for future progress.

Role of Immune Cells in Biliary Repair

The biliary system is comprised of cholangiocytes and plays an important role in maintaining liver function. Under normal conditions, cholangiocytes remain in the stationary phase and maintain a very low turnover rate. However, the robust biliary repair is initiated in disease conditions, and different repair mechanisms can be activated depending on the pathological changes. During biliary disease, immune cells including monocytes, lymphocytes, neutrophils, and mast cells are recruited to the liver. The cellular interactions between cholangiocytes and these recruited immune cells as well as hepatic resident immune cells, including Kupffer cells, determine disease outcomes. However, the role of immune cells in the initiation, regulation, and suspension of biliary repair remains elusive. The cellular processes of cholangiocyte proliferation, progenitor cell differentiation, and hepatocyte-cholangiocyte transdifferentiation during biliary diseases are reviewed to manifest the underlying mechanism of biliary repair. Furthermore, the potential role of immune cells in crucial biliary repair mechanisms is highlighted. The mechanisms of biliary repair in immune-mediated cholangiopathies, inherited cholangiopathies, obstructive cholangiopathies, and cholangiocarcinoma are also summarized. Additionally, novel techniques that could clarify the underlying mechanisms of biliary repair are displayed. Collectively, this review aims to deepen the understanding of the mechanisms of biliary repair and contributes potential novel therapeutic methods for treating biliary diseases.

Pathological, molecular, and clinical characteristics of cholangiocarcinoma: A comprehensive review

Cholangiocarcinomas are a heterogeneous group of highly aggressive cancers that may arise anywhere within the biliary tree. There is a wide geographical variation with regards to its incidence, and risk-factor associations which may include liver fluke infection, primary sclerosing cholangitis, and hepatolithiasis amongst others. These tumours are classified into intrahepatic, perihilar and distal based on their anatomical location. Morphologically, intrahepatic cholangiocarcinomas are further sub-classified into small and large duct variants. Perihilar and distal cholangiocarcinomas are usually mucin-producing tubular adenocarcinomas. Cholangiocarcinomas develop through a multistep carcinogenesis and are preceded by dysplastic and in situ lesions. While clinical characteristics and management of these tumours have been extensively elucidated in literature, their ultra-structure and tumour biology remain relatively unknown. This review focuses on the current knowledge of pathological characteristics, molecular alterations of cholangiocarcinoma, and its precursor lesions (including biliary intraepithelial neoplasia, intraductal papillary neoplasms of the bile duct, intraductal tubulopapillary neoplasms and mucinous cystic neoplasm).

Clinicopathological characteristics and prognostic factors of patients with primary gallbladder neuroendocrine carcinomas

OBJECTIVES

Primary gallbladder neuroendocrine carcinomas (GB-NEC) are malignant neoplasms that remained to be studied. In this study we aimed to summarize their clinicopathological characteristics, effective treatment and prognostic factors for patients with GB-NEC.

METHODS

Patients with GB-NEC admitted to Shanghai Jiao Tong University Affiliated Sixth People's Hospital and Renji Hospital, School of Medicine, Shanghai Jiao Tong University from October 2012 to August 2020 were enrolled. Clinicopathological characteristics of our patients and those reported in previous studies were recorded. The Kaplan-Meier method and univariate and multivariate Cox regression analyses were used for survival analysis.

RESULTS

Altogether 15 patients from our hospitals and 47 patients from previous studies were included. A total of 55 patients who underwent surgical resection, including R₀ and non-R₀ resection, had significantly longer overall survival compared with the other seven patients. A univariate analysis indicated that patients aged 60 years or older, with jaundice, carcinoid syndrome, non-R₀ resection, and advanced stage were associated with worse survival. A multivariate analysis showed that patients aged 60 years or older, carcinoid syndrome and non-R₀ resection, but not lymphadenectomy and adjuvant chemotherapy, were independently related to reduced survival.

CONCLUSIONS

R₀ resection should be the first-line treatment for GB-NEC. Older age, carcinoid syndrome and non-R₀ resection are independently associated with reduced survival after surgical resection.

Islet Regeneration and Pancreatic Duct Glands in Human and Experimental Diabetes

Contrasting evidence is present regarding the contribution of stem/progenitor cell populations to pancreatic regeneration in diabetes. Interestingly, a cell compartment with stem/progenitor cell features has been identified in the pancreatic duct glands (PDGs). The aims of the present study were to evaluate pancreatic islet injury and regeneration, and the participation of the PDG compartment in type 2 diabetic mellitus (T2DM) and in an experimental model of diabetes. Human pancreata were obtained from normal (N = 5) or T2DM (N = 10) cadaveric organ donors. Experimental diabetes was generated in mice by intraperitoneal injection of 150 mg/kg of streptozotocin (STZ, N = 10); N = 10 STZ mice also received daily intraperitoneal injections of 100 µg of human recombinant PDX1 peptide (STZ + PDX1). Samples were examined by immunohistochemistry/immunofluorescence or RT-qPCR. Serum glucose and c-peptide levels were measured in mice. Islets in T2DM patients showed β-cell loss, signs of injury and proliferation, and a higher proportion of central islets. PDGs in T2DM patients had a higher percentage of proliferating and insulin⁺ or glucagon⁺ cells compared to controls; pancreatic islets could be observed within pancreatic duct walls of T2DM patients. STZ mice were characterized by reduced islet area compared to controls. PDX1 treatment increased islet area and the percentage of central islets compared to untreated STZ mice but did not revert diabetes. In conclusion, T2DM patients show signs of pancreatic islet regeneration and involvement of the PDG niche. PDX1 administration could support increased endocrine pancreatic regeneration in STZ. These findings contribute to defining the role and participation of stem/progenitor cell compartments within the pancreas.

Metabolic dysfunction-associated fatty liver disease and the risk of 24 specific cancers

BACKGROUND

Metabolic dysfunction-associated fatty liver disease (MAFLD) is a significant health issue closely associated with multiple metabolic dysfunctions. The association between MAFLD and cancer risk is yet unknown.

METHODS

UK Biobank study participants were diagnosed for the presence of MAFLD at baseline. A multivariable Cox regression model was performed to examine the associations of MAFLD with incident events in 24 specific cancers.

RESULTS

We included 352,911 individuals (37.2% with MAFLD), among whom 23,345 developed cancers. Compared with non-MAFLD, MAFLD was significantly associated with 10 of the 24 examined cancers, including corpus uteri (hazard ratio [HR] = 2.36, 95% CI 1.99-2.80), gallbladder (2.20, 1.14-4.23), liver (1.81, 1.43-2.28), kidney (1.77, 1.49-2.11), thyroid (1.69, 1.20-2.38), esophagus (1.48, 1.25-1.76), pancreas (1.31, 1.10-1.56), bladder (1.26, 1.11-1.43), breast (1.19, 1.11-1.27), and colorectal and anus cancers (1.14, 1.06-1.23). The associations of MAFLD with liver, esophageal, pancreatic, colorectal and anal and bladder cancers and malignant melanoma were strengthened in males, and associations with kidney, thyroid, and lung cancers were increased in females. The associations of MAFLD with the risk of liver, kidney, and thyroid cancers remained significant after further adjusting for the waist circumference or body mass index and the number of metabolic syndrome components based on the main models. The risk-increasing allele of PNPLA3 rs738409 significantly amplified the association of MAFLD with the risk of liver and kidney cancers.

CONCLUSION

MAFLD is associated with an increased risk of a set of cancers, but the effect substantially varies by site. MAFLD deserves higher priority in the current scheme of cancer prevention.

The neonatal liver: Normal development and response to injury and disease

The liver emerges from the ventral foregut endoderm around 3 weeks in human and 1 week in mice after fertilization. The fetal liver works as a hematopoietic organ and then develops functions required for performing various metabolic reactions in late fetal and neonatal periods. In parallel with functional differentiation, the liver establishes three dimensional tissue structures. In particular, establishment of the bile excretion system consisting of bile canaliculi of hepatocytes and bile ducts of cholangiocytes is critical to maintain healthy tissue status. This is because hepatocytes produce bile as they functionally mature, and if allowed to remain within the liver tissue can lead to cytotoxicity. In this review, we focus on epithelial tissue morphogenesis in the perinatal period and cholestatic liver diseases caused by abnormal development of the biliary system.

Patch grafting, strategies for transplantation of organoids into solid organs such as liver

Epithelial cell therapies have been at an impasse because of inefficient methods of transplantation to solid organs. Patch grafting strategies were established enabling transplantation of ≥10^7th organoids/patch of porcine GFP+ biliary tree stem/progenitors into livers of wild type hosts. Grafts consisted of organoids embedded in soft (~100 Pa) hyaluronan hydrogels, both prepared in serum-free Kubota's Medium; placed against target sites; covered with a silk backing impregnated with more rigid hyaluronan hydrogels (~700 Pa); and use of the backing to tether grafts with sutures or glue to target sites. Hyaluronan coatings (~200-300 Pa) onto the serosal surface of the graft served to minimize adhesions with neighboring organs. The organ's clearance of hyaluronans enabled restoration of tissue-specific paracrine and systemic signaling, resulting in return of normal hepatic histology, with donor parenchymal cells uniformly integrated amidst host cells and that had differentiated to mature hepatocytes and cholangiocytes. Grafts containing donor mature hepatocytes, partnered with endothelia, and in the same graft biomaterials as for stem/progenitor organoids, did not engraft. Engraftment occurred if porcine liver-derived mesenchymal stem cells (MSCs) were co-transplanted with donor mature cells. RNA-seq analyses revealed that engraftment correlated with expression of matrix-metalloproteinases (MMPs), especially secreted isoforms that were found expressed strongly by organoids, less so by MSCs, and minimally, if at all, by adult cells. Engraftment with patch grafting strategies occurred without evidence of emboli or ectopic cell distribution. It was successful with stem/progenitor organoids or with cells with a source(s) of secreted MMP isoforms and offers significant potential for enabling cell therapies for solid organs.

Generation of Hepatobiliary Cell Lineages from Human Induced Pluripotent Stem Cells: Applications in Disease Modeling and Drug Screening

The possibility to reproduce key tissue functions in vitro from induced pluripotent stem cells (iPSCs) is offering an incredible opportunity to gain better insight into biological mechanisms underlying development and disease, and a tool for the rapid screening of drug candidates. This review attempts to summarize recent strategies for specification of iPSCs towards hepatobiliary lineages -hepatocytes and cholangiocytes-and their use as platforms for disease modeling and drug testing. The application of different tissue-engineering methods to promote accurate and reliable readouts is discussed. Space is given to open questions, including to what extent these novel systems can be informative. Potential pathways for improvement are finally suggested.

A single-cell-resolution fate map of endoderm reveals demarcation of pancreatic progenitors by cell cycle

A progenitor cell could generate a certain type or multiple types of descendant cells during embryonic development. To make all the descendant cell types and developmental trajectories of every single progenitor cell clear remains an ultimate goal in developmental biology. Characterizations of descendant cells produced by each uncommitted progenitor for a full germ layer represent a big step toward the goal. Here, we focus on early foregut endoderm, which generates foregut digestive organs, including the pancreas, liver, foregut, and ductal system, through distinct lineages. Using unbiased single-cell labeling techniques, we label every individual zebrafish foregut endodermal progenitor cell out of 216 cells to visibly trace the distribution and number of their descendant cells. Hence, single-cell-resolution fate and proliferation maps of early foregut endoderm are established, in which progenitor regions of each foregut digestive organ are precisely demarcated. The maps indicate that the pancreatic endocrine progenitors are featured by a cell cycle state with a long G1 phase. Manipulating durations of the G1 phase modulates pancreatic progenitor populations. This study illustrates foregut endodermal progenitor cell fate at single-cell resolution, precisely demarcates different progenitor populations, and sheds light on mechanistic insights into pancreatic fate determination.

Neonatal hyperinsulinism in transient and classical forms of tyrosinemia

BACKGROUND

The spectrum of disorders associated with hyperinsulinemic hypoglycemia (HHI) has vastly increased over the past 20 years with identification of molecular, metabolic and cellular pathways involved in the regulation of insulin secretion and its actions. Hereditary tyrosinemia (HT1) is a rare metabolic disorder associated with accumulation of toxic metabolites of the tyrosine pathway due to a genetically mediated enzyme defect of fumarylacetoacetate hydrolase. Transient tyrosinemia of the newborn (TTN) is a benign condition with a maturational defect of the enzymes associated with tyrosine metabolism without any genetic abnormalities.

RESULTS

We describe two rare cases of HHI, one in a patient with HT1 and for the first time, in a patient with TTN. Each of our patients presented in the neonatal period with persistent hypoglycemia that on biochemical evaluation was consistent with HHI. Each patient received diazoxide therapy for 3.5 months and 17 months of life, respectively and HHI resolved thereafter.

CONCLUSION

Despite the fact that HHI has been described in HT1 for several decades, no specific mechanism has been delineated. Although we considered the common embryonal origin of the liver and pancreas with the hepatotoxic effect in HT1 also impacting the latter, this was not a possible explanation for TTN. The commonality between our two patients is the accumulation of certain amino acids which are known to be insulinotropic. We therefore hypothesize that the excess of amino acids such as leucine, lysine, valine and isoleucine in our patients resulted in HHI, which was transient. Both patients responded to diazoxide. This novel presentation in TTN and the reassuring response in both HT1 and TTN to diazoxide will be useful to inform physicians about managing HHI in these patients. Further studies are required to delineate the mechanism of HHI in these infants.

Variant anatomy of the biliary system as a cause of pancreatic and peri-ampullary cancers

BACKGROUND

The cause of most pancreatic and periampullary cancers (PAC) is unknown. Recently, anatomic variations such as pancreatobiliary maljunction have been recognized as risk factors, similar to Barrett-related gastro-esophageal cancers.

METHODS

Pre-operative MRI from 860 pancreatic/biliary resections, including 322 PACs, were evaluated for low-union (cystic duct joining the common hepatic duct inside of the pancreas or within 5 mm of the pancreatic border) RESULTS: Low-union, seen <10% of the population, was present in 44% of PACs (73% distal bile duct/cholangiocarcinoma, 42% pancreatic head, and 34% ampullary). It was significantly lower(11%) in conditions without connection to the ductal system (thus not exposed to the ductal/biliary tract contents), namely mucinous cystic neoplasms and intrahepatic cholangiocarcinomas(p < 0.0001). Intra-pancreatic type low-union was seen in 16% of PACs versus 2% of controls(p < 0.0001).

DISCUSSION

This study establishes an association between low-union and PACs, and points to an anatomy-induced chemical/bilious carcinogenesis. This may explain why most pancreas cancers are in the head. It is possible that the same chemical milieu, caused by conditions other than low-union/insertion, may also play a role in the remaining half of PACs. This opens various treatment opportunities including milieu modifications (chemoprevention), focused screening of at-risk patients, and early detection with possible corrective actions.

Distinct EpCAM-Positive Stem Cell Niches Are Engaged in Chronic and Neoplastic Liver Diseases

In normal human livers, EpCAM^pos cells are mostly restricted in two distinct niches, which are (i) the bile ductules and (ii) the mucous glands present inside the wall of large intrahepatic bile ducts (the so-called peribiliary glands). These EpCAM^pos cell niches have been proven to harbor stem/progenitor cells with great importance in liver and biliary tree regeneration and in the pathophysiology of human diseases. The EpCAM^pos progenitor cells within bile ductules are engaged in driving regenerative processes in chronic diseases affecting hepatocytes or interlobular bile ducts. The EpCAM^pos population within peribiliary glands is activated when regenerative needs are finalized to repair large intra- or extra-hepatic bile ducts affected by chronic pathologies, including primary sclerosing cholangitis and ischemia-induced cholangiopathies after orthotopic liver transplantation. Finally, the presence of distinct EpCAM^pos cell populations may explain the histological and molecular heterogeneity characterizing cholangiocarcinoma, based on the concept of multiple candidate cells of origin. This review aimed to describe the precise anatomical distribution of EpCAM^pos populations within the liver and the biliary tree and to discuss their contribution in the pathophysiology of human liver diseases, as well as their potential role in regenerative medicine of the liver.

Anatomical and histological characteristics of the hepatobiliary system in adult Sox17 heterozygote mice

Biliary atresia (BA) is a rare neonatal disease characterized by inflammation and obstruction of the extrahepatic bile ducts (EHBDs). The Sox17-haploinsufficient (Sox17^+/- ) mouse is an animal model of BA that encompasses bile duct injury and subsequent BA-like inflammation by the neonatal stage. Most Sox17^+/- neonates die soon after birth, but some Sox17^+/- pups reach adulthood and have a normal life span, unlike human BA. However, the phenotype and BA-derived scars in the hepatobiliary organs of surviving Sox17^+/- mice are unknown. Here, we examined the phenotypes of the hepatobiliary organs in post-weaning and young adult Sox17^+/- mice. The results confirmed the significant reduction in liver weight, together with peripheral calcinosis and aberrant vasculature in the hepatic lobule, in surviving Sox17^+/- mice as compared with their wild-type (WT) littermates. Such hepatic phenotypes may be sequelae of hepatobiliary damage at the fetal and neonatal stages, a notion supported by the slight, but significant, increases in the levels of serum markers of liver damage in adult Sox17^+/- mice. The surviving Sox17^+/- mice had a shorter gallbladder in which ectopic hepatic ducts were more frequent compared to WT mice. Also, the surviving Sox17^+/- mice showed neither obstruction of the EHBDs nor atrophy or inflammation of hepatocytes or the intrahepatic ducts. These data suggest that some Sox17^+/- pups with BA naturally escape lethality and recover from fetal hepatobiliary damages during the perinatal period, highlighting the usefulness of the in vivo model in understanding the hepatobiliary healing processes after surgical restoration of bile flow in human BA.

Peribiliary glands pathology in a large series of end-stage alcohol-related liver disease

The peribiliary glands are intramural or extramural structures with multiple functions related to bile secretion. The peribiliary glands can develop cystic alterations in several conditions, such as alcohol addiction. Peribiliary cysts can enlarge till being radiologically visible and mimic cancer. We studied 217 consecutive explanted livers for end-stage alcohol-related liver disease from the Pathology Unit of the Liver Unit at the King's College Hospital in Denmark Hill, with particular focus on peribiliary glands. Our cohort consisted of 31 females and 186 males, with a median age of 51 and of 56 years respectively. 92,2% had established cirrhosis, 73,3% had only alcohol-induced liver disease, whilst 26,7% had other co-morbidities. We found a mild ectasia of the peribiliary glands (<2 mm) in 37,8% and peribiliary cysts (> = 2 mm) in 22,6% of cases. The diameter of the peribiliary glands varied from 1 mm to 8 mm. Inflammation of the peribiliary glands was found in the majority of cases with dilatation (p value = 0,000). 4,6% of the peribiliary cysts had low-grade intraductal papillary neoplasm of the bile ducts confined to the peribiliary glands. Pancreatic heterotopia was found in 10,6% and associated with the presence of ectasia. Our findings fit with what is reported in literature, such as the alcohol-induced damage at the peribiliary glands. Moreover these results underline the possible role of peribiliary glands in the development of the intraductal papillary neoplasm of the bile ducts, the biliary counterpart of the branch type intraductal mucinous neoplasm of the pancreas.

Pluripotent stem cell-derived cholangiocytes and cholangiocyte organoids

The development of protocols for pluripotent stem cell (PSC) differentiation into cholangiocytes and cholangiocyte organoids in three-dimensional structures represent a huge advance in both research and medical fields because of the limited access to primary human cholangiocytes and the potential bias induced by animal models used to study cholangiopathies in vivo. PSC-derived cholangiocyte organoids consisting of either cysts with luminal space or branching tubular structures are composed of cells with apico-basal polarity that can fulfill cholangiocyte functions like the transport of bile salts. Several protocols of PSC differentiation have already been published but we added to the detailed protocol we describe here some notes or advice to facilitate its handling by new users. We also propose detailed protocols to carry out some of the characterization analyses using immunofluorescence to study the expression of specific markers and a functionality test to visualize bile acid transport using cholyl-lysyl-fluorescein (CLF).

Gallbladder wall abnormality in biliary atresia of mouse Sox17+/- neonates and human infants

Biliary atresia (BA) is characterized by the inflammation and obstruction of the extrahepatic bile ducts (EHBDs) in newborn infants. SOX17 is a master regulator of fetal EHBD formation. In mouse Sox17+/- BA models, SOX17 reduction causes cell-autonomous epithelial shedding together with the ectopic appearance of SOX9-positive cystic duct-like epithelia in the gallbladder walls, resulting in BA-like symptoms during the perinatal period. However, the similarities with human BA gallbladders are still unclear. In the present study, we conducted phenotypic analysis of Sox17+/- BA neonate mice, in order to compare with the gallbladder wall phenotype of human BA infants. The most characteristic phenotype of the Sox17+/- BA gallbladders is the ectopic appearance of SOX9-positive peribiliary glands (PBGs), so-called pseudopyloric glands (PPGs). Next, we examined SOX17/SOX9 expression profiles of human gallbladders in 13 BA infants. Among them, five BA cases showed a loss or drastic reduction of SOX17-positive signals throughout the whole region of gallbladder epithelia (SOX17-low group). Even in the remaining eight gallbladders (SOX17-high group), the epithelial cells near the decidual sites were frequently reduced in the SOX17-positive signal intensity. Most interestingly, the most characteristic phenotype of human BA gallbladders is the increased density of PBG/PPG-like glands in the gallbladder body, especially near the epithelial decidual site, indicating that PBG/PPG formation is a common phenotype between human BA and mouse Sox17+/- BA gallbladders. These findings provide the first evidence of the potential contribution of SOX17 reduction and PBG/PPG formation to the early pathogenesis of human BA gallbladders.This article has an associated First Person interview with the joint first authors of the paper.

Tubular bile duct structure mimicking bile duct morphogenesis for prospective in vitro liver metabolite recovery

Background

Liver metabolites are used to diagnose disease and examine drugs in clinical pharmacokinetics. Therefore, development of an in vitro assay system that reproduces liver metabolite recovery would provide important benefits to pharmaceutical research. However, liver models have proven challenging to develop because of the lack of an appropriate bile duct structure for the accumulation and transport of metabolites from the liver parenchyma. Currently available bile duct models, such as the bile duct cyst-embedded extracellular matrix (ECM), lack any morphological resemblance to the tubular morphology of the living bile duct. Moreover, these systems cannot overcome metabolite recovery issues because they are established in isolated culture systems. Here, we successfully established a non-continuous tubular bile duct structure model in an open-culture system, which closely resembled an in vivo structure. This system was utilized to effectively collect liver metabolites separately from liver parenchymal cells.

Results

Triple-cell co-culture of primary rat hepatoblasts, rat biliary epithelial cells, and mouse embryonic fibroblasts was grown to mimic the morphogenesis of the bile duct during liver development. Overlaying the cells with ECM containing a Matrigel and collagen type I gel mixture promoted the development of a tubular bile duct structure. In this culture system, the expression of specific markers and signaling molecules related to biliary epithelial cell differentiation was highly upregulated during the ductal formation process. This bile duct structure also enabled the separate accumulation of metabolite analogs from liver parenchymal cells.

Conclusions

A morphogenesis-based culture system effectively establishes an advanced bile duct structure and improves the plasticity of liver models feasible for autologous in vitro metabolite-bile collection, which may enhance the performance of high-throughput liver models in cell-based assays.

Expression of fatty-acid-binding protein 5 in intrahepatic and extrahepatic cholangiocarcinoma: the possibility of different energy metabolisms in anatomical location

The biliary tract cancer (BTC) covers a range of carcinomas, including intrahepatic cholangiocarcinoma (ICC), cholangiolocellular carcinoma (CoCC), perihilar cholangiocarcinoma (perihilar CC), extrahepatic cholangiocarcinoma (ECC), and gallbladder cancer (GBC), defined according to the anatomical location. These adenocarcinomas mostly comprise biliary epithelial cell-derived malignant cells. In addition to anatomical differences, there are morphological and biological differences in BTC starting from embryonic development of the tissues extending to physiological differences. Fatty acid-binding proteins (FABPs) are closely associated with the energy metabolism. Using surgical specimens from 74 BTCs, we performed immunohistochemistry for FABP5 and its associated molecules, including peroxisome proliferator-activated receptor γ (PPARγ), PPARγ coactivator 1 (PGC-1), and estrogen-related receptor α (ERRα). We found that the expression patterns of small BTCs (ICC and CoCC) considerably differed from those of large BTCs (perihilar CC, ECC, and GBC). Expression of FABP5 and PGC-1 in large BTCs was high compared with those of small BTCs, but no difference in the expression of PPARγ and ERRα was observed. FABP5 appears to play a role in malignant progression in large BTCs. Small and large BTCs possess different energy metabolism systems owing to their different anatomical locations and course of carcinogenesis, although all BTCs originate from biliary epithelial cells.

Peribiliary Gland Niche Participates in Biliary Tree Regeneration in Mouse and in Human Primary Sclerosing Cholangitis

BACKGROUND AND AIMS

Mechanisms underlying the repair of extrahepatic biliary tree (EHBT) after injury have been scarcely explored. The aims of this study were to evaluate, by using a lineage tracing approach, the contribution of peribiliary gland (PBG) niche in the regeneration of EHBT after damage and to evaluate, in vivo and in vitro, the signaling pathways involved.

APPROACH AND RESULTS

Bile duct injury was induced by the administration of 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC) diet for 14 days to Krt19^Cre TdTomato^LSL mice. Human biliary tree stem/progenitor cells (BTSC) within PBGs were isolated from EHBT obtained from liver donors. Hepatic duct samples (n = 10) were obtained from patients affected by primary sclerosing cholangitis (PSC). Samples were analyzed by histology, immunohistochemistry, western blotting, and polymerase chain reaction. DDC administration causes hyperplasia of PBGs and periductal fibrosis in EHBT. A PBG cell population (Cytokeratin19^- /SOX9⁺ ) is involved in the renewal of surface epithelium in injured EHBT. The Wnt signaling pathway triggers human BTSC proliferation in vitro and influences PBG hyperplasia in vivo in the DDC-mediated mouse biliary injury model. The Notch signaling pathway activation induces BTSC differentiation in vitro toward mature cholangiocytes and is associated with PBG activation in the DDC model. In human PSC, inflammatory and stromal cells trigger PBG activation through the up-regulation of the Wnt and Notch signaling pathways.

CONCLUSIONS

We demonstrated the involvement of PBG cells in regenerating the injured biliary epithelium and identified the signaling pathways driving BTSC activation. These results could have relevant implications on the pathophysiology and treatment of cholangiopathies.

Increased proliferation of hepatic periportal ductal progenitor cells contributes to persistent hypermetabolism after trauma

Prolonged and persistent hypermetabolism and excessive inflammatory response after severe trauma is detrimental and associated with poor outcome. The predisposing pathology or signals mediating this complex response are essentially unknown. As the liver is the central organ mediating the systemic metabolic responses and considering that adult hepatic stem cells are on top of the hierarchy of cell differentiation and may pass epigenetic information to their progeny, we asked whether liver progenitor cells are activated, signal hypermetabolism upon post-traumatic cellular stress responses, and pass this to differentiated progeny. We generated Sox9CreERT2 : ROSA26 EYFP mice to lineage-trace the periportal ductal progenitor cells (PDPCs) and verify the fate of these cells post-burn. We observed increased proliferation of PDPCs and their progeny peaking around two weeks post-burn, concomitant with the hepatomegaly and the cellular stress responses. We then sorted out PDPCs, PDPC-derived hepatocytes and mature hepatocytes, compared their transcriptome and showed that PDPCs and their progeny present a significant up-regulation in signalling pathways associated with inflammation and metabolic activation, contributing to persistent hypermetabolic and hyper-inflammatory state. Furthermore, concomitant down-regulation of LXR signalling in PDPCs and their progeny implicates the therapeutic potential of early and short-term administration of LXR agonists in ameliorating such persistent hypermetabolism.

Hhex regulates the specification and growth of the hepatopancreatic ductal system

Significant efforts have advanced our understanding of foregut-derived organ development; however, little is known about the molecular mechanisms that underlie the formation of the hepatopancreatic ductal (HPD) system. Here, we report a role for the homeodomain transcription factor Hhex in directing HPD progenitor specification in zebrafish. Loss of Hhex function results in impaired HPD system formation. We found that Hhex specifies a distinct population of HPD progenitors that gives rise to the cystic duct, common bile duct, and extra-pancreatic duct. Since hhex is not uniquely expressed in the HPD region but is also expressed in endothelial cells and the yolk syncytial layer (YSL), we tested the role of blood vessels as well as the YSL in HPD formation. We found that blood vessels are required for HPD patterning, but not for HPD progenitor specification. In addition, we found that Hhex is required in both the endoderm and the YSL for HPD development. Our results shed light on the mechanisms directing endodermal progenitors towards the HPD fate and emphasize the tissue specific requirement of Hhex during development.

Generation of insulin-secreting cells from mouse gallbladder stem cells by small molecules in vitro

Background

Stem cell-derived pancreatic β-like cells hold great promise for treating diabetes. Gallbladder belongs to the extrahepatic bile duct system and possesses stem-like cells. These stem cells could be expanded in vitro and have the potential of differentiating into hepatocytes, cholangiocytes, or pancreatic cells. As the gallbladder is highly available, gallbladder stem cells provide a new cell source of pancreatic β-like cells. In this study, we aimed to investigate an approach for the generation of pancreatic β-like cells from gallbladder stem cells (GSCs) without genetic modification.

Methods

A CK19Cre^ERT;Rosa26R-GFP mouse was used to isolate CK19⁺ cells, which represented EpCAM⁺ stem cells in the gallbladder. They were cultured in the modified Kubota’s medium for expansion and further analyzed. Then, we developed a strategy to screen a combination of small molecules that can generate insulin-secreting cells from gallbladder stem cells. These cells were identified with markers of pancreatic cells. Finally, they were seeded into the cellulosic sponge and transplanted to the diabetic mice for functional examination in vivo.

Results

Gallbladder stem cells could be expanded for more than 15 passages. They expressed typical hepatic stem cell markers including CK19, EpCAM, Sox9, and albumin. By screening method, we found that adding Noggin, FR180204, and cyclopamine could efficiently induce gallbladder stem cells differentiating into insulin-secreting cells. These cells expressed Pdx1, Nkx6.1, and insulin but were negative for Gcg. After transplantation with the cellulosic sponge, they could ameliorate hyperglycemia in the diabetic mice.

Conclusion

This study provides a new approach which can generate insulin-secreting cells from the gallbladder without genetic modification. This offers an option for β cell therapy in treating type 1 diabetes.

Common features between neoplastic and preneoplastic lesions of the biliary tract and the pancreas

the bile duct system and pancreas show many similarities due to their anatomical proximity and common embryological origin. Consequently, preneoplastic and neoplastic lesions of the bile duct and pancreas share analogies in terms of molecular, histological and pathophysiological features. Intraepithelial neoplasms are reported in biliary tract, as biliary intraepithelial neoplasm (BilIN), and in pancreas, as pancreatic intraepithelial neoplasm (PanIN). Both can evolve to invasive carcinomas, respectively cholangiocarcinoma (CCA) and pancreatic ductal adenocarcinoma (PDAC). Intraductal papillary neoplasms arise in biliary tract and pancreas. Intraductal papillary neoplasm of the biliary tract (IPNB) share common histologic and phenotypic features such as pancreatobiliary, gastric, intestinal and oncocytic types, and biological behavior with the pancreatic counterpart, the intraductal papillary mucinous neoplasm of the pancreas (IPMN). All these neoplastic lesions exhibit similar immunohistochemical phenotypes, suggesting a common carcinogenic process. Indeed, CCA and PDAC display similar clinic-pathological features as growth pattern, poor response to conventional chemotherapy and radiotherapy and, as a consequence, an unfavorable prognosis. The objective of this review is to discuss similarities and differences between the neoplastic lesions of the pancreas and biliary tract with potential implications on a common origin from similar stem/progenitor cells.

Functions and the Emerging Role of the Foetal Liver into Regenerative Medicine

During foetal life, the liver plays the important roles of connection and transient hematopoietic function. Foetal liver cells develop in an environment called a hematopoietic stem cell niche composed of several cell types, where stem cells can proliferate and give rise to mature blood cells. Embryologically, at about the third week of gestation, the liver appears, and it grows rapidly from the fifth to 10th week under WNT/β-Catenin signaling pathway stimulation, which induces hepatic progenitor cells proliferation and differentiation into hepatocytes. Development of new strategies and identification of new cell sources should represent the main aim in liver regenerative medicine and cell therapy. Cells isolated from organs with endodermal origin, like the liver, bile ducts, and pancreas, could be preferable cell sources. Furthermore, stem cells isolated from these organs could be more susceptible to differentiate into mature liver cells after transplantation with respect to stem cells isolated from organs or tissues with a different embryological origin. The foetal liver possesses unique features given the co-existence of cells having endodermal and mesenchymal origin, and it could be highly available source candidate for regenerative medicine in both the liver and pancreas. Taking into account these advantages, the foetal liver can be the highest potential and available cell source for cell therapy regarding liver diseases and diabetes.

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.

Hyaluronan-Based Grafting Strategies for Liver Stem Cell Therapy and Tracking Methods

Cell adhesion is essential for survival, it plays important roles in physiological cell functions, and it is an innovative target in regenerative medicine. Among the molecular interactions and the pathways triggered during cell adhesion, the binding of cluster of differentiation 44 (CD44), a cell-surface glycoprotein involved in cell-cell interactions, to hyaluronic acid (HA), a major component of the extracellular matrix, is a crucial step. Cell therapy has emerged as a promising treatment for advanced liver diseases; however, so far, it has led to low cell engraftment and limited cell repopulation of the target tissue. Currently, different strategies are under investigation to improve cell grafting in the liver, including the use of organic and inorganic biomatrices that mimic the microenvironment of the extracellular matrix. Hyaluronans, major components of stem cell niches, are attractive candidates for coating stem cells since they improve viability, proliferation, and engraftment in damaged livers. In this review, we will discuss the new strategies that have been adopted to improve cell grafting and track cells after transplantation.

Free episomal and integrated HBV DNA in HBsAg-negative patients with intrahepatic cholangiocarcinoma

There is evidence that chronic hepatitis B virus (HBV) infection is associated with an increased risk of intrahepatic cholangiocarcinoma (ICC) development, and it has been hypothesized an etiological role of HBV in the development of this tumor. Very little is known about occult HBV infection (OBI) in ICC. Aims of the study were to investigate the OBI prevalence and to characterize the HBV molecular status at intrahepatic level in OBI-positive cases with ICC.

Frozen liver tumor specimens from 47 HBV surface-antigen-negative patients with ICC and 41 paired non-tumor liver tissues were tested for OBI by 4 different HBV-specific nested PCR. Covalently closed circular HBV DNA (HBV cccDNA) and viral integrations were investigated in OBI-positive cases.

HBV DNA was detected in tumor and/or non-tumor specimens from 29/47 (61.7%) ICC patients. HBV cccDNA was found in tissues from 5/17 (34.5%) cases examined. HBV integration was detected in 4/10 (40%) tumor tissues tested and involved HBx and HBV-core gene sequences in 3 and 1 cases, respectively. Viral integration occurred: (a) 9,367 nucleotides upstream of the cat-eye-syndrome critical region protein-5-isoform coding sequence; (b) within the cystinosin isoform-1-precursor gene; (c) within the thromboxane-A-synthase-1 gene; (d) within the ATPase phospholipid transporting 9B gene.

Occult HBV infection is highly prevalent in patients with ICC. Both free viral genomes and integrated HBV DNA can be present in these cases. These results suggest an involvement of HBV in the carcinogenic process leading to ICC development even in cases with occult infection.

Influence of Ischemia Time in Injury of Deep Peribiliary Glands of the Bile Ducts Graft: A Prospective Study

The deep peribiliary glands (DPBG) are a niche of progenitor cells in the wall of the biliary duct (BD) and are the second line of multiplication when severe lesion of the epithelium occurs. Previous studies have identified DPBG injury as a cause of post-liver transplant (LT) biliary stenosis; this complication is a major cause of post-LT morbidity. The incidence of biliary stenosis in our center is high (38.1%). This study evaluates the lesion of DPBG in response to ischemia. Graft BD was collected in adult LT between August 2016-July 2017, from donation after brain death. Samples of 45 grafts were collected at 2 moments: BD1-during graft preparation and BD2-before biliary anastomosis. Histological analysis of the samples was performed and then classified according to degree of lesion (0, ≤50%, and >50%). A comparison was made between the degree of lesion and graft ischemia, graft histology, donor, and procurement variables. The DPBG lesion was more frequent in BD2 (20.9% vs 7%, P = .079). BD2 lesions with DPBG lesions had higher medians and means at all times of ischemia. The difference was greater in the warm ischemia time (0: 43.3 ± 12.53 minutes vs ≤50%: 52.4 ± 14.38 minutes, P = .068). The group of BD1 with DPBG lesion presented superior median cold ischemia time (CIT). In the analysis of the remaining variables there were also no statistically significant differences. We concluded that during the period of CIT there is already lesion of the DPBG, which increases after reperfusion of the graft, in greater association with longer warm ischemia time.

Anatomical, histomorphological and molecular classification of cholangiocarcinoma

Cholangiocarcinoma constitutes a heterogeneous group of malignancies that can emerge at any point of the biliary tree. Cholangiocarcinoma is classified into intrahepatic, perihilar and distal based on its anatomical location. Histologically, conventional perihilar/distal cholangiocarcinomas are mucin-producing adenocarcinomas or papillary tumours; intrahepatic cholangiocarcinomas are more heterogeneous and can be sub-classified according to the level or size of the displayed bile duct. Cholangiocarcinoma develops through multistep carcinogenesis and is preceded by dysplastic and in situ lesions. Definition and clinical significance of precursor lesions, including biliary intraepithelial neoplasia, intraductal papillary neoplasms of the bile duct, intraductal tubulopapillary neoplasms and mucinous cystic neoplasm, are discussed in this review. A main challenge in diagnosing cholangiocarcinoma is the fact that tumour tissue for histological examination is difficult to obtain. Thus, a major clinical obstacle is the establishment of the correct diagnosis at a tumour stage that is amenable to surgery which still represents the only curable therapeutic option. Current standards, methodology and criteria for diagnosis are discussed. Cholangiocarcinoma represents a heterogeneous tumour with regard to molecular alterations. In intrahepatic subtype, mainly two distinctive morpho-molecular groups can currently be discriminated. Large-duct type intrahepatic cholangiocarcinoma shows a high mutation frequency of oncogenes and tumour suppressor genes, such as KRAS and TP53 while Isocitrate Dehydrogenase 1/2 mutations and Fibroblast Growth Factor Receptor 2-fusions are typically seen in small-duct type tumours. It is most important to ensure the separation of the given anatomical subtypes and to search for distinct subgroups within the subtypes on a molecular and morphological basis.

Antibodies to a CA 19-9 Related Antigen Complex Identify SOX9 Expressing Progenitor Cells In Human Foetal Pancreas and Pancreatic Adenocarcinoma

The Sialyl Lewis A antigen, or CA 19-9, is the prototype serum biomarker for adenocarcinoma of the pancreas. Despite extensive clinical study of CA 19-9 in gastrointestinal malignancies, surprisingly little is known concerning the specific cell types that express this marker during development, tissue regeneration and neoplasia. SOX9 is a transcription factor that plays a key role in these processes in foregut tissues. We report the biochemistry and tissue expression of the GCTM-5 antigen, a pancreatic cancer marker related to, but distinct from, CA19-9. This antigen, defined by two monoclonal antibodies recognising separate epitopes on a large glycoconjugate protein complex, is co-expressed with SOX9 by foregut ductal progenitors in the developing human liver and pancreas, and in pancreatic adenocarcinoma. These progenitors are distinct from cell populations identified by DCLK1, LGR5, or canonical markers of liver and pancreatic progenitor cells. Co-expression of this antigen complex and SOX9 also characterises the ductal metaplasia of submucosal glands that occurs during the development of Barrett’s oesophagus. The GCTM-5 antigen complex can be detected in the sera of patients with pancreatic adenocarcinoma. The GCTM-5 epitope shows a much more restricted pattern of expression in the normal adult pancreas relative to CA19-9. Our findings will aid in the identification, characterisation, and monitoring of ductal progenitor cells during development and progression of pancreatic adenocarcinoma in man.