Animal models of gastrointestinal and liver diseases. Animal models of cystic fibrosis: gastrointestinal, pancreatic, and hepatobiliary disease and pathophysiology

Pathophysiology of Cystic Fibrosis Liver Disease

Hepatobiliary complications of Cystic Fibrosis (CF) constitute a significant burden for persons with CF of all ages, with advanced CF liver disease in particular representing a leading cause of mortality. The causes of the heterogeneity of clinical manifestations, ranging from steatosis to focal biliary cholestasis and biliary strictures, are poorly understood and likely reflect a variety of environmental and disease-modifying factors in the setting of underlying CFTR mutations. This review summarizes the current understanding of the pathophysiology of hepatobiliary manifestations of CF, and discusses emerging disease models and therapeutic approaches that hold promise to impact this important yet incompletely addressed aspect of CF care.

MCC950 as a promising candidate for blocking NLRP3 inflammasome activation: A review of preclinical research and future directions

The NOD-like receptor thermal protein domain associated protein 3 (NLRP3) inflammasome is a key component of the innate immune system that triggers inflammation and pyroptosis and contributes to the development of several diseases. Therefore, blocking the activation of the NLRP3 inflammasome has therapeutic potential for the treatment of these diseases. MCC950, a selective small molecule inhibitor, has emerged as a promising candidate for blocking NLRP3 inflammasome activation. Ongoing research is focused on elucidating the specific targets of MCC950 as well as assessfing its metabolism and safety profile. This review discusses the diseases that have been studied in relation to MCC950, with a focus on stroke, Alzheimer's disease, liver injury, atherosclerosis, diabetes mellitus, and sepsis, using bibliometric analysis. It then summarizes the potential pharmacological targets of MCC950 and discusses its toxicity. Furthermore, it traces the progression from preclinical to clinical research for the treatment of these diseases. Overall, this review provides a solid foundation for the clinical therapeutic potential of MCC950 and offers insights for future research and therapeutic approaches.

Cystic Fibrosis and Cancer: Unraveling the Complex Role of CFTR Gene in Cancer Susceptibility

Cystic fibrosis (CF) is a genetic disorder affecting multiple organs, primarily the lungs and digestive system. Over the years, advancements in medical care and treatments have significantly increased the life expectancy of individuals with CF. However, with this improved longevity, concerns about the potential risk of developing certain types of cancers have arisen. This narrative review aims to explore the relationship between CF, increased life expectancy, and the associated risk for cancers. We discuss the potential mechanisms underlying this risk, including chronic inflammation, immune system dysregulation, and genetic factors. Additionally, we review studies that have examined the incidence and types of cancers seen in CF patients, with a focus on gastrointestinal, breast, and respiratory malignancies. We also explore the impact of CFTR modulator therapies on cancer risk. In the gastrointestinal tract, CF patients have an elevated risk of developing colorectal cancer, pancreatic cancer, and possibly esophageal cancer. The underlying mechanisms contributing to these increased risks are not fully understood, but chronic inflammation, altered gut microbiota, and genetic factors are believed to play a role. Regular surveillance and colonoscopies are recommended for early detection and management of colorectal cancer in CF patients. Understanding the factors contributing to cancer development in CF patients is crucial for implementing appropriate surveillance strategies and improving long-term outcomes. Further research is needed to elucidate the molecular mechanisms involved and develop targeted interventions to mitigate cancer risk in individuals with CF.

Targeting fibrosis, mechanisms and cilinical trials

Fibrosis is characterized by the excessive extracellular matrix deposition due to dysregulated wound and connective tissue repair response. Multiple organs can develop fibrosis, including the liver, kidney, heart, and lung. Fibrosis such as liver cirrhosis, idiopathic pulmonary fibrosis, and cystic fibrosis caused substantial disease burden. Persistent abnormal activation of myofibroblasts mediated by various signals, such as transforming growth factor, platelet-derived growth factor, and fibroblast growh factor, has been recongized as a major event in the occurrence and progression of fibrosis. Although the mechanisms driving organ-specific fibrosis have not been fully elucidated, drugs targeting these identified aberrant signals have achieved potent anti-fibrotic efficacy in clinical trials. In this review, we briefly introduce the aetiology and epidemiology of several fibrosis diseases, including liver fibrosis, kidney fibrosis, cardiac fibrosis, and pulmonary fibrosis. Then, we summarise the abnormal cells (epithelial cells, endothelial cells, immune cells, and fibroblasts) and their interactions in fibrosis. In addition, we also focus on the aberrant signaling pathways and therapeutic targets that regulate myofibroblast activation, extracellular matrix cross-linking, metabolism, and inflammation in fibrosis. Finally, we discuss the anti-fibrotic drugs based on their targets and clinical trials. This review provides reference for further research on fibrosis mechanism, drug development, and clinical trials.

Cucumis sativus extract elicits chloride secretion by stimulation of the intestinal TMEM16A ion channel

CONTEXT

Cucumber (Cucumis sativus Linn. [Cucurbitaceae]) is widely known for its purgative, antidiabetic, antioxidant, and anticancer therapeutic potential. However, its effect on gastrointestinal (GI) disease is unrecognised.

OBJECTIVE

This study investigated the effect of C. sativus fruit extract (CCE) on intestinal chloride secretion, motility, and motor function, and the role of TMEM16A chloride channels.

MATERIALS AND METHODS

CCE extracts were obtained from commercially available cucumber. Active fractions were then purified by HPLC and analysed by high resolution mass spectrometry. The effect of CCE on intestinal chloride secretion was investigated in human colonic T84 cells, ex vivo mouse intestinal tissue using an Ussing chamber, and the two-electrode voltage-clamp technique to record calcium sensitive TMEM16A chloride currents in Xenopus laevis oocytes. In vivo, intestinal motility was investigated using the loperamide-induced C57BL/6 constipation mouse model. Ex vivo contractility of mouse colonic smooth muscles was assessed by isometric force measurements.

RESULTS

CCE increased the short-circuit current (ΔIsc 34.47 ± µA/cm²) and apical membrane chloride conductance (ΔI_Cl 95 ± 8.1 µA/cm²) in intestinal epithelial cells. The effect was dose-dependent, with an EC₅₀ value of 0.06 µg/mL. CCE stimulated the endogenous TMEM16A-induced Cl^- current in Xenopus laevis oocytes. Moreover, CCE increased the contractility of smooth muscle in mouse colonic tissue and enhanced small bowel transit in CCE treated mice compared to loperamide controls. Mass spectrometry suggested a cucurbitacin-like analogue with a mass of 512.07 g/mol underlying the bioactivity of CCE.

CONCLUSION

A cucurbitacin-like analog present in CCE activates TMEM16A channels, which may have therapeutic potential in cystic fibrosis and intestinal hypodynamic disorders.

Early intrahepatic duct defects in a cystic fibrosis porcine model

Hepatobiliary disease causes significant morbidity and mortality in people with cystic fibrosis (CF), yet this problem remains understudied. Previous studies in the newborn CF pig demonstrated decreased bile flow into the small intestine and a microgallbladder with increased luminal mucus and fluid secretion defects. In this study, we examined the intrahepatic bile ducts of the newborn CF pig. We assessed whether our findings from the gallbladder are present elsewhere in the porcine biliary tract and if CF pig cholangiocytes have fluid secretion defects. Immunohistochemistry demonstrated apical CFTR expression in non-CF pig intrahepatic bile ducts of a variety of sizes; CF pig intrahepatic bile ducts lacked CFTR expression. Assessment of serum markers did not reveal significant signs of hepatobiliary disease except for an elevation in direct bilirubin. Quantitative histology demonstrated that CF pigs had smaller bile ducts that more frequently contained luminal mucus. CF intrahepatic cholangiocyte organoids were smaller and lacked cAMP-mediated fluid secretion. Together these data suggest that cholangiocyte fluid secretion is decreased in the CF pig, contributing to structural changes in bile ducts and decreased biliary flow.

Deletion of the lactoperoxidase gene causes multisystem inflammation and tumors in mice

Strongly oxidative H₂O₂ is biologically important, but if uncontrolled, would lead to tissue injuries. Lactoperoxidase (LPO) catalyzes the redox reaction of reducing highly reactive H₂O₂ to H₂O while oxidizing thiocyanate (SCN^-) to relatively tissue-innocuous hypothiocyanite (OSCN^-). SCN^- is the only known natural, effective reducing-substrate of LPO; humans normally derive SCN^- solely from food. While its enzymatic mechanism is understood, the actual biological role of the LPO-SCN^- system in mammals remains unestablished. Our group previously showed that this system protected cultured human cells from H₂O₂-caused injuries, a basis for the hypothesis that general deficiency of such an antioxidative mechanism would lead to multisystem inflammation and tumors. To test this hypothesis, we globally deleted the Lpo gene in mice. The mutant mice exhibited inflammation and lesions in the cardiovascular, respiratory, digestive or excretory systems, neuropathology, and tumors, with high incidence. Thus, this understudied LPO-SCN^- system is an essential protective mechanism in vivo.

Animal Models and Their Role in Understanding the Pathophysiology of Cystic Fibrosis-Associated Gastrointestinal Lesions

The life expectancy of cystic fibrosis (CF) patients has greatly increased over the past decade, and researchers and clinicians must now navigate complex disease manifestations that were not a concern prior to the development of modern therapies. Explosive growth in the number of CF animal models has also occurred over this time span, clarifying CF disease pathophysiology and creating opportunities to understand more complex disease processes associated with an aging CF population. This review focuses on the CF-associated pathologies of the gastrointestinal system and how animal models have increased our understanding of this complex multisystemic disease. Although CF is primarily recognized as a pulmonary disease, gastrointestinal pathology occurs very commonly and can affect the quality of life for these patients. Furthermore, we discuss how next-generation genetic engineering of larger animal models will impact the field's understanding of CF disease pathophysiology and the development of novel therapeutic strategies.

Animal models for cystic fibrosis: a systematic search and mapping review of the literature. Part 2: nongenetic models

Various animal models are available to study cystic fibrosis (CF). These models may help to enhance our understanding of the pathology and contribute to the development of new treatments. We systematically searched all publications on CF animal models. Because of the large number of models retrieved, we split this mapping review into two parts. Previously, we presented the genetic CF animal models. In this paper we present the nongenetic CF animal models. While genetic animal models may, in theory, be preferable for genetic diseases, the phenotype of a genetic model does not automatically resemble human disease. Depending on the research question, other animal models may thus be more informative.We searched Pubmed and Embase and identified 12,303 unique publications (after duplicate removal). All references were screened for inclusion by two independent reviewers. The genetic animal models for CF (from 636 publications) were previously described. The non-genetic CF models (from 189 publications) are described in this paper, grouped by model type: infection-based, pharmacological, administration of human materials, xenografts and other. As before for the genetic models, an overview of basic model characteristics and outcome measures is provided. This CF animal model overview can be the basis for an objective, evidence-based model choice for specific research questions. Besides, it can help to retrieve relevant background literature on outcome measures of interest.

Gastrointestinal, Pancreatic, and Hepatic Manifestations of Cystic Fibrosis in the Newborn

Gastrointestinal, pancreatic, and hepatic signs and symptoms represent the most common presentation of early disease among patients with cystic fibrosis and may be the initial indication of disease. Regardless of whether cystic fibrosis is diagnosed early by newborn screening or later by clinical course, the impact of gastrointestinal, pancreatic, and hepatic manifestations on early life is nearly ubiquitous. Conditions strongly linked with cystic fibrosis, such as meconium ileus and pancreatic insufficiency, must be recognized and treated early to optimize both short- and long-term care. Similarly, less specific conditions such as reflux, poor weight gain, and cholestasis are frequently encountered in infants with cystic fibrosis. In this population, these conditions may present unique challenges in which early interventions may have significant influence on both short- and long-term morbidity and mortality outcomes.

Androgen aggravates liver fibrosis by activation of NLRP3 inflammasome in CCl4-induced liver injury mouse model

Studies have shown that there are differences between the sexes regarding to the occurrence and development of liver diseases, which may be associated with sex hormones. However, the mechanisms behind it are largely unknown. In this study, we first investigated the differences of liver injury between male and female mice, using the CCl₄-induced liver injury mouse model. It showed that the liver damage of male mice was much more severe than that of female mice. Both the acute injury and fibrosis of the liver were reduced when androgens were depleted by castration of male mice. The vulnerability of male liver was associated with testis endocrine and excessive activation of inflammatory response in the liver. Castrated male mice with testosterone supplementation showed aggravated liver inflammatory response and fibrosis. The activity of NOD-like receptor protein 3 (NLRP3) inflammasome was increased when testosterone supplementation was provided. However, the enhanced inflammatory response and fibrosis due to testosterone supplementation were negated by inhibiting the activation of NLRP3 using the specific small molecule inhibitor MCC950. It suggests that testosterone is a key factor that influences liver injury by regulating the NLRP3 inflammasome activation-mediated inflammatory response.

Phenotypic Characterization and Comparison of Cystic Fibrosis Rat Models Generated Using CRISPR/Cas9 Gene Editing

Animal models of cystic fibrosis (CF) are essential for investigating disease mechanisms and trialing potential therapeutics. This study generated two CF rat models using clustered regularly interspaced short palindromic repeats/clustered regularly interspaced short palindromic repeats-associated protein 9 gene editing. One rat model carries the common human Phe508del (ΔF508) CF transmembrane conductance regulator (CFTR) mutation, whereas the second is a CFTR knockout model. Phenotype was characterized using a range of functional and histologic assessments, including nasal potential difference to measure electrophysiological function in the upper airways, RNAscope in situ hybridization and quantitative PCR to assess CFTR mRNA expression in the lungs, immunohistochemistry to localize CFTR protein in the airways, and histopathologic assessments in a range of tissues. Both rat models revealed a range of CF manifestations, including reduced survival, intestinal obstruction, bioelectric defects in the nasal epithelium, histopathologic changes in the trachea, large intestine, and pancreas, and abnormalities in the development of the male reproductive tract. The CF rat models presented herein will prove useful for longitudinal assessments of pathophysiology and therapeutics.

Lumacaftor/ivacaftor therapy is associated with reduced hepatic steatosis in cystic fibrosis patients

BACKGROUND

Hepatic steatosis is a common form of cystic fibrosis associated liver disease (CFLD) seen in an estimated 15%-60% of patients with cystic fibrosis (CF). The pathophysiology and health implications of hepatic steatosis in cystic fibrosis remain largely unknown. In the general population, hepatic steatosis is strongly associated with insulin resistance and type 2 diabetes. Cystic fibrosis related diabetes (CFRD) impacts 40%-50% of CF adults and is characterized by both insulin insufficiency and insulin resistance. We hypothesized that patients with CFRD would have higher levels of hepatic steatosis than cystic fibrosis patients without diabetes.

AIM

To determine whether CFRD is associated with hepatic steatosis and to explore the impact of lumacaftor/ivacaftor therapy on hepatic steatosis in CF.

METHODS

Thirty patients with CF were recruited from a tertiary care medical center for this cross-sectional study. Only pancreatic insufficient patients with CFRD or normal glucose tolerance (NGT) were included. Patients with established CFLD, end stage lung disease, or persistently elevated liver enzymes were excluded. Mean magnetic resonance imaging (MRI) proton density fat fraction (PDFF) was obtained for all participants. Clinical characteristics [age, sex, body mass index, percent predicted forced expiratory volume at 1 s (FEV1), lumacaftor/ivacaftor use] and blood chemistries were assessed for possible association with hepatic steatosis. Hepatic steatosis was defined as a mean MRI PDFF > 5%. Patients were grouped by diabetes status (CFRD, NGT) and cystic fibrosis transmembrane conductance regulator (CFTR) modulator use (lumacaftor/ivacaftor, no lumacaftor/ivacaftor) to determine between group differences. Continuous variables were analyzed with a Wilcoxon rank sum test and discrete variables with a Chi square test or Fisher’s exact test.

RESULTS

Twenty subjects were included in the final analysis. The median age was 22.3 years (11.3-39.0) and median FEV1 was 77% (33%-105%). Twelve subjects had CFRD and 8 had NGT. Nine subjects were receiving lumacaftor/ivacaftor. The median PDFF was 3.0% (0.0%-21.0%). Six subjects (30%) had hepatic steatosis defined as PDFF > 5%. Hepatic fat fraction was significantly lower in patients receiving lumacaftor/ivacaftor (median, range) (2.0%, 0.0%-6.4%) than in patients not receiving lumacaftor/ivacaftor (4.1%, 2.7-21.0%), P = 0.002. Though patients with CFRD had lower PDFF (2.2%, 0.0%-14.5%) than patients with NGT (4.9%, 2.4-21.0%) this did not reach statistical significance, P = 0.06. No other clinical characteristic was strongly associated with hepatic steatosis.

CONCLUSION

Use of the CFTR modulator lumacaftor/ivacaftor was associated with significantly lower hepatic steatosis. No association between CFRD and hepatic steatosis was found in this cohort.

Update on the diagnosis and management of exocrine pancreatic insufficiency

Exocrine pancreatic insufficiency (EPI) is characterized by inadequate pancreatic enzyme delivery to the small intestine Exocrine pancreatic insufficiency (EPI) is characterized by inadequate pancreatic enzyme delivery to the small intestine, resulting in malabsorption. Clinical manifestations of EPI are often nonspecific and can lead to lack of timely recognition and diagnosis. Central to this clinical dilemma is the lack of highly accurate or specific testing which leads to misdiagnosis and suboptimal treatment. Identification of high-risk patients is key in the diagnosis of EPI and this includes patients with pancreatic parenchyma disorders such as chronic pancreatitis, pancreatic malignancy, cystic fibrosis, and those undergoing pancreatic resection for benign and malignant disease. Less recognized are the number of additional conditions which may also have EPI as a consequence. Owing to an increase in morbidity and impaired quality of life associated with this condition, goals of treatment have been aimed at repleting exocrine enzyme deficiency by oral pancreatic enzyme replacement therapy (PERT). The basis of PERT is to provide activated digestive enzymes to the small bowel during the prandial period, mainly, leading to sufficient absorption of fat and fat-soluble vitamins. The benefits of PERT have been shown to go beyond the improvement in signs and symptoms associated with EPI and include decreasing prevalence of osteopathy and improving survival outcomes in subsets of patients with this condition. However, despite the overall benefits in treatment, the diagnosis and management of EPI are suboptimal. Current literature suggests patients at high risk of developing EPI are not tested and those who are diagnosed are not treated with adequate dosages. In this review, we highlight patients who are at high risk for the development of EPI, analyze consequences and treatment of this disorder, review rationale for enzyme replacement therapy, and examine current evidence for treatment optimization.

Cystic fibrosis liver disease: A condition in need of structured transition and continuity of care

Liver disease affects one-third of patients with cystic fibrosis (CF) and it is one of the major causes of morbidity and mortality in these patients. Historically considered a disease of childhood, its impact is now seen more often in adulthood. The heterogeneous pattern of CF liver disease and its rapid progression to cirrhosis remain a diagnostic challenge and new questions pertaining to the nature of liver involvement have recently been raised. Non-invasive measures to stratify the severity of liver involvement are increasingly used to predict clinical outcomes. A single treatment, ursodeoxycholic acid, has been used to slow progression of liver disease while recent advances in the field of CF treatments are promising. Management of portal hypertension remains challenging but outcomes after liver transplantation are encouraging. While many questions remain unanswered, a growing number of CF patients reach adulthood and will require care for CF liver disease.

Animal models for cystic fibrosis: A systematic search and mapping review of the literature - Part 1: genetic models

Animal models for cystic fibrosis (CF) have enhanced our understanding of the pathology and contributed to the development of new treatments. In the field of CF, many animal models have been developed and described. To our knowledge, thus far, none of the reviews of CF animal models has used a systematic methodology. A systematic approach to creating model overviews can lead to an objective, evidence-based choice of an animal model for new research questions. We searched Pubmed and Embase for the currently available animal models for CF. Two independent reviewers screened the results. We included all primary studies describing an animal model for CF. After duplicate removal, 12,304 publications were left. Because of the large number of models, in the current paper, only the genetic models are presented. A total of 636 publications were identified describing genetic animal models for CF in mice, pigs, ferrets, rats and zebrafish. Most of these models have an altered Cftr gene. An overview of basic model characteristics and outcome measures for these genetic models is provided, together with advice on using these data. As far as the authors are aware, this is one of the largest systematic mapping reviews on genetic animal models for CF. It can aid in selecting a suitable model and outcome measures. In general, the reporting quality of the included publications was poor. Further systematic reviews are warranted to determine the quality and translational value of these models further.

Pathophysiology of Cystic Fibrosis Liver Disease: A Channelopathy Leading to Alterations in Innate Immunity and in Microbiota

Cystic fibrosis (CF) is a monogenic disease caused by mutation of Cftr. CF-associated liver disease (CFLD) is a common nonpulmonary cause of mortality in CF and accounts for approximately 2.5%-5% of overall CF mortality. The peak of the disease is in the pediatric population, but a second wave of liver disease in CF adults has been reported in the past decade in association with an increase in the life expectancy of these patients. New drugs are available to correct the basic defect in CF but their efficacy in CFLD is not known. The cystic fibrosis transmembrane conductance regulator, expressed in the apical membrane of cholangiocytes, is a major determinant for bile secretion and CFLD classically has been considered a channelopathy. However, the recent findings of the cystic fibrosis transmembrane conductance regulator as a regulator of epithelial innate immunity and the possible influence of the intestinal disease with an altered microbiota on the liver complication have opened new mechanistic insights on the pathogenesis of CFLD. This review provides an overview of the current understanding of the pathophysiology of the disease and discusses a potential target for intervention.

Animal Models in the Pathophysiology of Cystic Fibrosis

Our understanding of the multiorgan pathology of cystic fibrosis (CF) has improved impressively during the last decades, but we still lack a full comprehension of the disease progression. Animal models have greatly contributed to the elucidation of specific mechanisms involved in CF pathophysiology and the development of new therapies. Soon after the cloning of the CF transmembrane conductance regulator (CFTR) gene in 1989, the first mouse model was generated and this model has dominated in vivo CF research ever since. Nonetheless, the failure of murine models to mirror human disease severity in the pancreas and lung has led to the generation of larger animal models such as pigs and ferrets. The following review presents and discusses data from the current animal models used in CF research.

Bile acid homeostasis in gastrointestinal and metabolic complications of cystic fibrosis

With the improved treatment of the pulmonary complications of cystic fibrosis (CF), gastrointestinal problems have become more important in the morbidity in CF. A hallmark of the gastrointestinal phenotype of CF, apart from pancreatic insufficiency, is a disruption of bile acid homeostasis. Bile acid homeostasis is important for many gastrointestinal processes including fat absorption, inflammation, microbial composition, as well as regulation of whole body energy metabolism. This review describes the impairment of bile acid homeostasis in CF, its possible consequences for gastrointestinal and metabolic complications and its potential as a target for therapy.

Animal models for cystic fibrosis liver disease (CFLD)

Liver disease is a severe complication in patients with Cystic Fibrosis (CF), a genetic disease caused by mutations in the gene encoding for cystic fibrosis transmembrane conductance regulator (CFTR) channel. The sequence of events leading to CFLD is still unclear and has limited the development of more specific treatments other than the bile acid UDCA. However, in the last twenty years, several gaps have been filled, which have mainly been possible due to the availability of different animal models that mimic CF. CF mice, although they lack a spontaneous liver manifestation, have been essential to better understand the multiple functions of CFTR expression on the apical membrane of cholangiocytes, from chloride channel to regulator of epithelial innate immunity. Additionally, we have learned that the gut microbiota might be a pathogenetic factor for the development of liver disease. The recent creation of novel CF animal models (i.e. pig and ferret) that better reproduce the human disease, will allow for comparative studies with species that spontaneously develop the liver disease and will hopefully lead to novel therapeutic treatments. In this review, we have compared and summarized the main features of the current available CF animal models and their applicability for the study of the liver phenotype.

Guanylate cyclase 2C agonism corrects CFTR mutants

Cystic fibrosis (CF) is a genetic disorder in which epithelium-generated fluid flow from the lung, intestine, and pancreas is impaired due to mutations disrupting CF transmembrane conductance regulator (CFTR) channel function. CF manifestations of the pancreas and lung are present in the vast majority of CF patients, and 15% of CF infants are born with obstructed gut or meconium ileus. However, constipation is a significantly underreported outcome of CF disease, affecting 47% of the CF patients, and management becomes critical in the wake of increasing life span of CF patients. In this study, we unraveled a potentially novel molecular role of a membrane-bound cyclic guanosine monophosphate-synthesizing (cGMP-synthesizing) intestinal enzyme, guanylate cyclase 2C (GCC) that could be targeted to ameliorate CF-associated intestinal fluid deficit. We demonstrated that GCC agonism results in functional rescue of murine F508del/F508del and R117H/R117H Cftr and CFTR mutants in CF patient-derived intestinal spheres. GCC coexpression and activation facilitated processing and ER exit of F508del CFTR and presented a potentially novel rescue modality in the intestine, similar to the CF corrector VX-809. Our findings identify GCC as a biological CFTR corrector and potentiator in the intestine.

Cystic Fibrosis-related Liver Disease: Research Challenges and Future Perspectives

OBJECTIVES

Hepatobiliary complications are a leading cause of morbidity and mortality in cystic fibrosis (CF) patients. Knowledge of the underlying pathological aspects and optimal clinical management is, however, sorely lacking.

METHODS

We provide a summary of the lectures given by international speakers at the European Society for Paediatric Gastroenterology, Hepatology, and Nutrition (ESPGHAN) monothematic conference on cystic fibrosis-related liver disease (CFLD) held in Paris in January 2016, to discuss the status of our current knowledge of liver disease in CF patients, to define the critical areas that need to be addressed, and to resolve actions to elucidate relevant mechanisms of disease to optimise future therapeutic options.

CONCLUSIONS

The need for a universal consensus on the definition of CFLD to clarify disease stage and to identify relevant biomarkers to assess disease severity was highlighted. A deeper understanding of the pathophysiology and prognostic factors for the long-term evolution of CFLD is fundamental to move forward and has a strong bearing on identifying potential treatments. Novel experimental models and new treatment options under investigation are discussed and offer hope for the near future of CFLD.

Animal and model systems for studying cystic fibrosis

The cystic fibrosis (CF) field is the beneficiary of five species of animal models that lack functional cystic fibrosis transmembrane conductance regulator (CFTR) channel. These models are rapidly informing mechanisms of disease pathogenesis and CFTR function regardless of how faithfully a given organ reproduces the human CF phenotype. New approaches of genetic engineering with RNA-guided nucleases are rapidly expanding both the potential types of models available and the approaches to correct the CFTR defect. The application of new CRISPR/Cas9 genome editing techniques are similarly increasing capabilities for in vitro modeling of CFTR functions in cell lines and primary cells using air-liquid interface cultures and organoids. Gene editing of CFTR mutations in somatic stem cells and induced pluripotent stem cells is also transforming gene therapy approaches for CF. This short review evaluates several areas that are key to building animal and cell systems capable of modeling CF disease and testing potential treatments.

Stem cell-derived organoids to model gastrointestinal facets of cystic fibrosis

Cystic fibrosis (CF) is one of the most frequently occurring inherited human diseases caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) which lead to ample defects in anion transport and epithelial fluid secretion. Existing models lack both access to early stages of CF development and a coeval focus on the gastrointestinal CF phenotypes, which become increasingly important due increased life span of the affected individuals. Here, we provide a comprehensive overview of gastrointestinal facets of CF and the opportunity to model these in various systems in an attempt to understand and treat CF. A particular focus is given on forward-leading organoid cultures, which may circumvent current limitations of existing models and thereby provide a platform for drug testing and understanding of disease pathophysiology in gastrointestinal organs.

Animal models of biliary injury and altered bile acid metabolism

In the last 25years, a number of animal models, mainly rodents, have been generated with the goal to mimic cholestatic liver injuries and, thus, to provide in vivo tools to investigate the mechanisms of biliary repair and, eventually, to test the efficacy of innovative treatments. Despite fundamental limitations applying to these models, such as the distinct immune system and the different metabolism regulating liver homeostasis in rodents when compared to humans, multiple approaches, such as surgery (bile duct ligation), chemical-induced (3,5-diethoxycarbonyl-1,4-dihydrocollidine, DDC, α-naphthylisothiocyanate, ANIT), viral infections (Rhesus rotavirustype A, RRV-A), and genetic manipulation (Mdr2, Cftr, Pkd1, Pkd2, Prkcsh, Sec63, Pkhd1) have been developed. Overall, they have led to a range of liver phenotypes recapitulating the main features of biliary injury and altered bile acid metabolisms, such as ductular reaction, peribiliary inflammation and fibrosis, obstructive cholestasis and biliary dysgenesis. Although with a limited translability to the human setting, these mouse models have provided us with the ability to probe over time the fundamental mechanisms promoting cholestatic disease progression. Moreover, recent studies from genetically engineered mice have unveiled 'core' pathways that make the cholangiocyte a pivotal player in liver repair. In this review, we will highlight the main phenotypic features, the more interesting peculiarities and the different drawbacks of these mouse models. This article is part of a Special Issue entitled: Cholangiocytes in Health and Disease edited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Practical guide to exocrine pancreatic insufficiency - Breaking the myths

BACKGROUND

Exocrine pancreatic insufficiency (EPI) is characterized by a deficiency of exocrine pancreatic enzymes, resulting in malabsorption. Numerous conditions account for the etiology of EPI, with the most common being diseases of the pancreatic parenchyma including chronic pancreatitis, cystic fibrosis, and a history of extensive necrotizing acute pancreatitis. Treatment for EPI includes dietary management, lifestyle changes (i.e., decrease in alcohol consumption and smoking cessation), and pancreatic enzyme replacement therapy.

DISCUSSION

Many diagnostic tests are available to diagnose EPI, however, the criteria of choice remain unclear and the causes for a false-positive test are not yet understood. Despite multiple studies on the treatment of EPI using exogenous pancreatic enzymes, there remains confusion amongst medical practitioners with regard to the best approach to diagnose EPI, as well as dosing and administration of pancreatic enzymes. Appropriate use of diagnostics and treatment approaches using pancreatic enzymes in EPI is essential for patients. This opinion piece aims to address the existing myths, remove the current confusion, and function as a practical guide to the diagnosis and treatment of EPI.

Cystic fibrosis

Cystic fibrosis is a common life-limiting autosomal recessive genetic disorder, with highest prevalence in Europe, North America, and Australia. The disease is caused by mutation of a gene that encodes a chloride-conducting transmembrane channel called the cystic fibrosis transmembrane conductance regulator (CFTR), which regulates anion transport and mucociliary clearance in the airways. Functional failure of CFTR results in mucus retention and chronic infection and subsequently in local airway inflammation that is harmful to the lungs. CFTR dysfunction mainly affects epithelial cells, although there is evidence of a role in immune cells. Cystic fibrosis affects several body systems, and morbidity and mortality is mostly caused by bronchiectasis, small airways obstruction, and progressive respiratory impairment. Important comorbidities caused by epithelial cell dysfunction occur in the pancreas (malabsorption), liver (biliary cirrhosis), sweat glands (heat shock), and vas deferens (infertility). The development and delivery of drugs that improve the clearance of mucus from the lungs and treat the consequent infection, in combination with correction of pancreatic insufficiency and undernutrition by multidisciplinary teams, have resulted in remarkable improvements in quality of life and clinical outcomes in patients with cystic fibrosis, with median life expectancy now older than 40 years. Innovative and transformational therapies that target the basic defect in cystic fibrosis have recently been developed and are effective in improving lung function and reducing pulmonary exacerbations. Further small molecule and gene-based therapies are being developed to restore CFTR function; these therapies promise to be disease modifying and to improve the lives of people with cystic fibrosis.

The CF gastrointestinal microbiome: Structure and clinical impact

The gastrointestinal (GI) microbiome is shaped by host diet, immunity, and other physicochemical characteristics of the GI tract, and perturbations such as antibiotic treatments can lead to persistent changes in microbial constituency and function. These GI microbes also play critical roles in host nutrition and health. A growing body of evidence suggests that the GI microbiome in people with CF is altered, and that these dysbioses contribute to disease manifestations in many organs, both within and beyond the GI tract. Therapies that people with CF receive, even those targeting the respiratory tract, may impact the CF GI microbiome in ways that can influence the outcome of treatment. These new perspectives on the microbial contents of the CF intestine offer new opportunities for preventing a variety of CF-associated disorders. Pediatr Pulmonol. 2016;51:S35-S44. © 2016 Wiley Periodicals, Inc.

Development of an in vivo swine model of biliary dilatation-based direct peroral cholangioscopy

A reproducible in vivo swine model of bile duct dilation (BDD) was recently established and reported for preclinical testing of newly developed biliary devices or endoscopic techniques. The aim of the present study was to develop a more advanced large animal model in which it is possible to direct examination of the biliary tree. Methods Six mini pigs were prepared for the study. BDD models were first made by closure of the Vater's ampulla in all swine. Then endoscopic papillary balloon dilation (EPBD) was done in the animals. Feasibility of single-operator peroral cholangioscopy without assistance of accessories was evaluated using an ultra-slim upper endoscope in the animals. Results EPBD could be implemented using a dilation balloon catheter (10~13.5 mm) in all BDD models (6/6, 100%). Success rate of freehand direct insertion of an ultra-slim endoscope into the common bile duct was 100% (6/6), and access to the common hepatic duct with examination was possible using direct peroral cholangioscopy in five animals (5/6, 83.3%). None of the animals died. In the cholangioscopic examination, a bile duct polyp and a benign biliary stricture occurred naturally, respectively, in two of the six swine. Conclusion An in vivo swine model of biliary dilatation-based direct peroral cholangioscopy was established. This novel animal model may be useful for preclinical research of new materials or devices because direct visualization of the biliary tree is feasible.

Lessons learned from the cystic fibrosis pig

Deficient function in the anion channel cystic fibrosis (CF) transmembrane conductance regulator is the fundamental cause for CF. This is a monogenic condition that causes lesions in several organs including the respiratory tract, pancreas, liver, intestines, and reproductive tract. Lung disease is most notable, given it is the leading cause of morbidity and mortality in people with CF. Shortly after the identification of CF transmembrane conductance regulator, CF mouse models were developed that did not show spontaneous lung disease as seen in humans, and this spurred development of additional CF animal models. Pig models were considered a leading choice for several reasons including their similarity to humans in respiratory anatomy, physiology, and in size for translational imaging. The first CF pig models were reported in 2008 and have been extremely valuable to help clarify persistent questions in the field and advance understanding of disease pathogenesis. Because CF pigs are susceptible to lung disease like humans, they have direct utility in translational research. In addition, CF pig models are useful to compare and contrast with current CF mouse models, human clinical studies, and even newer CF animal models being characterized. This "triangulation" strategy could help identify genetic differences that underlie phenotypic variations, so as to focus and accelerate translational research.

Role of CTGF gene promoter methylation in the development of hepatic fibrosis

Connective tissue growth factor (CTGF) plays a critical role in the hepatic stellate cells (HSCs)-mediated development of hepatic fibrosis. Nevertheless, the effects of CTGF gene promoter methylation in the pathogenesis of hepatic fibrosis remain largely unknown. In the current study, we isolated and overexpressed CTGF in primary HSCs. We analyzed the CTGF gene promoter methylation inHSCs that undergo a phenotypic change into myofibroblast-like cellsthat express α-smooth muscle actin (α-SMA) in vitro and in vivo in a CCl4-induced rat hepatic fibrosis model. We found that CTGF promoted the phenotypic changes of HSCs into myofibroblasts in vitro, while inhibition of CTGF promoter methylation augmented the process, suggesting that CTGF gene promoter methylation may negatively regulate hepatic fibrosis. In vivo, CCl4 induced hepatic fibrosis in rats, and the severity of hepatic fibrosis inversely correlated with the levels of CTGF gene promoter methylation in HSCs. Together, our data demonstrate that CTGF gene promoter methylation may prevent the development of hepatic fibrosis, and low level of CTGF gene promoter methylation in HSCs may be a predisposing factor for developing liver fibrotic disease.

CFTR: A New Horizon in the Pathomechanism and Treatment of Pancreatitis

Cystic fibrosis transmembrane conductance regulator (CFTR) is an ion channel that conducts chloride and bicarbonate ions across epithelial cell membranes. Mutations in the CFTR gene diminish the ion channel function and lead to impaired epithelial fluid transport in multiple organs such as the lung and the pancreas resulting in cystic fibrosis. Heterozygous carriers of CFTR mutations do not develop cystic fibrosis but exhibit increased risk for pancreatitis and associated pancreatic damage characterized by elevated mucus levels, fibrosis, and cyst formation. Importantly, recent studies demonstrated that pancreatitis causing insults, such as alcohol, smoking, or bile acids, strongly inhibit CFTR function. Furthermore, human studies showed reduced levels of CFTR expression and function in all forms of pancreatitis. These findings indicate that impairment of CFTR is critical in the development of pancreatitis; therefore, correcting CFTR function could be the first specific therapy in pancreatitis. In this review, we summarize recent advances in the field and discuss new possibilities for the treatment of pancreatitis.

Immunohistochemical Detection of Markers for Translational Studies of Lung Disease in Pigs and Humans

Genetically engineered pigs are increasingly recognized as valuable models for the study of human disease. Immunohistochemical study of cellular markers of disease is an important tool for the investigation of these novel models so as to evaluate genotype and treatment differences. Even so, there remains a lack of validated markers for pig tissues that can serve as a translational link to human disease in organs such as the lung. Herein, we evaluate markers of cellular inflammation (cluster of differentiation [CD]3, CD79a, B cell lymphoma [BCL] 6, ionized calcium-binding adapter molecule [IBA]1, and myeloperoxidase) and those that may be involved with tissue remodeling (alpha-smooth muscle actin, beta-tubulin-III, lactoferrin, mucin [MUC]5AC, MUC5B, and cystic fibrosis transmembrane conductance regulator [CFTR]) for study of lung tissues. We compare the utility of these markers between pig and human lungs to validate translational relevance of each marker. Our results suggest these markers can be a useful addition in the pathological evaluation of porcine models of human disease.

Pancreatic pathophysiology in cystic fibrosis

The pancreas is one of the earliest, and most commonly affected, organs in patients with cystic fibrosis (CF). Studying the pathogenesis of pancreatic disease is limited in CF patients, due to its early clinical onset, co-morbidities and lack of tissue samples from the early phases of disease. In recent years, several new CF animal models have been developed that have advanced our understanding of both CF exocrine and endocrine pancreatic disease. Additionally, these models have helped us to better define the influence of pancreatic lesions on CF disease progression in other organs, such as the gastrointestinal tract and lung.

Liver reserve function assessment by acoustic radiation force impulse imaging

AIM: To evaluate the utility of liver reserve function by acoustic radiation force impulse (ARFI) imaging in patients with liver tumors.

METHODS: Seventy-six patients with liver tumors were enrolled in this study. Serum biochemical indexes, such as aminotransferase (ALT), aspartate aminotransferase (AST), serum albumin (ALB), total bilirubin (T-Bil), and other indicators were observed. Liver stiffness (LS) was measured by ARFI imaging, measurements were repeated 10 times, and the average value of the results was taken as the final LS value. Indocyanine green (ICG) retention was performed, and ICG-K and ICG-R15 were recorded. Child-Pugh (CP) scores were carried out based on patient’s preoperative biochemical tests and physical condition. Correlations among CP scores, ICG-R15, ICG-K and LS values were observed and analyzed using either the Pearson correlation coefficient or the Spearman rank correlation coefficient. Kruskal-Wallis test was used to compare LS values of CP scores, and the receiver-operator characteristic (ROC) curve was used to analyze liver reserve function assessment accuracy.

RESULTS: LS in the ICG-R15 10%-20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.19 ± 0.27 vs 1.59 ± 0.32, P < 0.01). LS in the ICG-R15 > 20% group was significantly higher than in the ICG-R15 < 10% group; and the difference was statistically significant (2.92 ± 0.29 vs 1.59 ± 0.32, P < 0.01). The LS value in patients with CP class A was lower than in patients with CP class B (1.57 ± 0.34 vs 1.86 ± 0.27, P < 0.05), while the LS value in patients with CP class B was lower than in patients with CP class C (1.86 ± 0.27 vs 2.47 ± 0.33, P < 0.01). LS was positively correlated with ICG-R15 (r = 0.617, P < 0.01) and CP score (r = 0.772, P < 0.01). Meanwhile, LS was negatively correlated with ICG-K (r = -0.673, P < 0.01). AST, ALT and T-Bil were positively correlated with LS, while ALB was negatively correlated with LS (P < 0.05). The ROC curve revealed that the when the LS value was 2.34 m/s, the Youden index was at its highest point, sensitivity was 69.2% and specificity was 92.1%.

CONCLUSION: For patients with liver tumors, ARFI imaging is a useful tool for assessing liver reserve function.