Autophagy and senescence in fibrosing cholangiopathies

CircUTRN24/miR-483-3p/IGF-1 Regulates Autophagy Mediated Liver Fibrosis in Biliary Atresia

Biliary atresia (BA) is a rare neonatal cholestatic disease that presents with a marked bile duct reaction and rapid fibrotic development. Our earlier research has shown that circUTRN24 is highly elevated in BA, but the exact molecular mechanism is still unknown. This study attempted to investigate whether circUTRN24 induces BA liver fibrosis through regulation of autophagy and to elucidate its molecular mechanism. Using TGF-β-treated hepatic stellate cells (HSC) LX-2, we created a liver fibrosis model. qRT-PCR was used to analyze the expression of circUTRN24, miR-483-3p, and IGF-1. Western blot analysis was used to assess the expression of IGF-1, HSC activation-related proteins, and autophagy-related proteins. The TGF-β-induced LX-2 cell fibrosis model was then supplemented with circUTRN24 siRNA, miR-483-3p mimics, and the autophagy activator Rapamycin, and functional rescue tests were carried out to investigate the role of circUTRN24, miR-483-3p, and autophagy in BA liver fibrosis. Using a luciferase reporter assay, a direct interaction between miR-483-3p and circUTRN24 or IGF-1 was discovered. With the increase of TGF-β treatment concentration, circUTRN24 expression also gradually increased, as did HSC activation and autophagy-related protein. si-circUTRN24 significantly decreased circUTRN24 expression and inhibited HSC activation and autophagy, which was reversed by Rapamycin. Through bioinformatics prediction and validation, we found circUTRN24 might act through miR-483-3p targeting IGF-1 in the autophagy-related mTOR pathway. Furthermore, miR-483-3p mimics significantly increased miR-483-3p expression and inhibited HSC activation and autophagy, which were reversed by Rapamycin. Functional rescue experiments showed that si-circUTRN24 inhibited circUTRN24 and IGF-1 expressions and promoted miR-483-3p expression, while the miR-483-3p inhibitor abolished these effects. These findings imply that circUTRN24/miR-483-3p/IGF-1 axis mediated LX-2 cell fibrosis by regulating autophagy.

A low baseline serum myostatin concentration is associated with poor clinical outcome in patients with primary biliary cholangitis

BACKGROUND AND AIM

Primary biliary cholangitis (PBC) is an autoimmune-mediated cholestatic liver disease that can progress to biliary cirrhosis and liver-related death. The associations between baseline myostatin levels and clinical outcomes in PBC patients are unknown. We aimed to clarify the influence of myostatin levels on the clinical outcomes of PBC patients.

METHODS

A total of 119 PBC patients were analyzed in this study. Myostatin levels were measured in stored sera before ursodeoxycholic acid treatment, and their associations with the clinical features and prognosis of PBC patients were analyzed. We analyzed the correlation between serum myostatin and chemokines/cytokines.

RESULTS

Serum myostatin was significantly lower in PBC patients (2343 pg/mL) than in healthy controls (4059 pg/mL, P < 0.001). The prevalence of patients with low myostatin levels increased according to the severity of histological fibrosis. The serum myostatin concentration was negatively correlated with the IL-6 and leucine-rich α2 glycoprotein levels, but the chemokine concentration was not correlated with the myostatin concentration. Low myostatin in PBC patients was associated with shorter survival without liver-related complications (hazard ratio [HR], 3.598; 95% confidence interval [CI], 1.27-10.1; P = 0.015) and shorter transplant-free survival (HR, 3.129; 95% CI, 1.02-9.56; P = 0.045) independent of pretreatment GLOBE score. Patients with both high pretreatment GLOBE scores and low myostatin levels had poor prognoses (log-rank test: P < 0.001).

CONCLUSIONS

A low serum myostatin concentration at diagnosis was associated with poor clinical outcomes. Assessment of circulating myostatin levels may improve the prediction of outcomes in patients with PBC.

LP340, a novel histone deacetylase inhibitor, decreases liver injury and fibrosis in mice: role of oxidative stress and microRNA-23a

Effective therapy for liver fibrosis is lacking. Here, we examined whether LP340, the lead candidate of a new-generation of hydrazide-based HDAC1,2,3 inhibitors (HDACi), decreases liver fibrosis. Liver fibrosis was induced by CCl4 treatment and bile duct ligation (BDL) in mice. At 6 weeks after CCl4, serum alanine aminotransferase increased, and necrotic cell death and leukocyte infiltration occurred in the liver. Tumor necrosis factor-α and myeloperoxidase markedly increased, indicating inflammation. After 6 weeks, α-smooth muscle actin (αSMA) and collagen-1 expression increased by 80% and 575%, respectively, indicating hepatic stellate cell (HSC) activation and fibrogenesis. Fibrosis detected by trichrome and Sirius-red staining occurred primarily in pericentral regions with some bridging fibrosis in liver sections. 4-Hydroxynonenal adducts (indicator of oxidative stress), profibrotic cytokine transforming growth factor-β (TGFβ), and TGFβ downstream signaling molecules phospho-Smad2/3 also markedly increased. LP340 attenuated indices of liver injury, inflammation, and fibrosis markedly. Moreover, Ski-related novel protein-N (SnoN), an endogenous inhibitor of TGFβ signaling, decreased, whereas SnoN expression suppressor microRNA-23a (miR23a) increased markedly. LP340 (0.05 mg/kg, ig., daily during the last 2 weeks of CCl4 treatment) decreased 4-hydroxynonenal adducts and miR23a production, blunted SnoN decreases, and inhibited the TGFβ/Smad signaling. By contrast, LP340 had no effect on matrix metalloproteinase-9 expression. LP340 increased histone-3 acetylation but not tubulin acetylation, indicating that LP340 inhibited Class-I but not Class-II HDAC in vivo. After BDL, focal necrosis, inflammation, ductular reactions, and portal and bridging fibrosis occurred at 2 weeks, and αSMA and collagen-1 expression increased by 256% and 560%, respectively. LP340 attenuated liver injury, ductular reactions, inflammation, and liver fibrosis. LP340 also decreased 4-hydroxynonenal adducts and miR23a production, prevented SnoN decreases, and inhibited the TGFβ/Smad signaling after BDL. In vitro, LP340 inhibited immortal human hepatic stellate cells (hTERT-HSC) activation in culture (αSMA and collagen-1 expression) as well as miR23a production, demonstrating its direct inhibitory effects on HSC. In conclusions, LP340 is a promising therapy for both portal and pericentral liver fibrosis, and it works by inhibiting oxidative stress and decreasing miR23a.

Effect of Cellular Senescence in Disease Progression and Transplantation: Immune Cells and Solid Organs

Aging of the world population significantly impacts healthcare globally and specifically, the field of transplantation. Together with end-organ dysfunction and prolonged immunosuppression, age increases the frequency of comorbid chronic diseases in transplant candidates and recipients, contributing to inferior outcomes. Although the frequency of death increases with age, limited use of organs from older deceased donors reflects the concerns about organ durability and inadequate function. Cellular senescence (CS) is a hallmark of aging, which occurs in response to a myriad of cellular stressors, leading to activation of signaling cascades that stably arrest cell cycle progression to prevent tumorigenesis. In aging and chronic conditions, senescent cells accumulate as the immune system's ability to clear them wanes, which is causally implicated in the progression of chronic diseases, immune dysfunction, organ damage, decreased regenerative capacity, and aging itself. The intimate interplay between senescent cells, their proinflammatory secretome, and immune cells results in a positive feedback loop, propagating chronic sterile inflammation and the spread of CS. Hence, senescent cells in organs from older donors trigger the recipient's alloimmune response, resulting in the increased risk of graft loss. Eliminating senescent cells or attenuating their inflammatory phenotype is a novel, potential therapeutic target to improve transplant outcomes and expand utilization of organs from older donors. This review focuses on the current knowledge about the impact of CS on circulating immune cells in the context of organ damage and disease progression, discusses the impact of CS on abdominal solid organs that are commonly transplanted, and reviews emerging therapies that target CS.

Panic at the Bile Duct: How Intrahepatic Cholangiocytes Respond to Stress and Injury

In the liver, biliary epithelial cells (BECs) line intrahepatic bile ducts (IHBDs) and are primarily responsible for modifying and transporting hepatocyte-produced bile to the digestive tract. BECs comprise only 3% to 5% of the liver by cell number but are critical for maintaining choleresis through homeostasis and disease. To this end, BECs drive an extensive morphologic remodeling of the IHBD network termed ductular reaction (DR) in response to direct injury or injury to the hepatic parenchyma. BECs are also the target of a broad and heterogenous class of diseases termed cholangiopathies, which can present with phenotypes ranging from defective IHBD development in pediatric patients to progressive periductal fibrosis and cancer. DR is observed in many cholangiopathies, highlighting overlapping similarities between cell- and tissue-level responses by BECs across a spectrum of injury and disease. The following core set of cell biological BEC responses to stress and injury may moderate, initiate, or exacerbate liver pathophysiology in a context-dependent manner: cell death, proliferation, transdifferentiation, senescence, and acquisition of neuroendocrine phenotype. By reviewing how IHBDs respond to stress, this review seeks to highlight fundamental processes with potentially adaptive or maladaptive consequences. A deeper understanding of how these common responses contribute to DR and cholangiopathies may identify novel therapeutic targets in liver disease.

Emerging Therapeutic Strategies in The Fight Against Primary Biliary Cholangitis

The liver has a vital role in many metabolic and regulatory processes in the body. Primary biliary cholangitis (PBC), previously known as primary biliary cirrhosis, is a chronic cholestatic autoimmune disease of the intrahepatic bile ducts associated with loss of tolerance to mitochondrial antigens. At this time there is no definitive cure for PBC; however, ursodeoxycholic acid (UDCA) has been shown to reduce injury when administered as the first line of treatment. Additional therapeutics can be given concurrently or as an alternative to UDCA to manage the symptoms and further curb disease progression. Currently, a liver transplant is the only potentially curative option when the patient has developed end-stage liver disease or intractable pruritus. This review aims to delineate the pathogenesis of primary biliary cholangitis and shed light on current therapeutic strategies in the treatment of PBC.

Senescence and senotherapies in biliary atresia and biliary cirrhosis

BACKGROUND

Premature senescence occurs in adult hepatobiliary diseases and worsens the prognosis through deleterious liver remodeling and hepatic dysfunction. Senescence might also arises in biliary atresia (BA), the first cause of pediatric liver transplantation. Since alternatives to transplantation are needed, our aim was to investigate premature senescence in BA and to assess senotherapies in a preclinical model of biliary cirrhosis.

METHODS

BA liver tissues were prospectively obtained at hepatoportoenterostomy (n=5) and liver transplantation (n=30) and compared to controls (n=10). Senescence was investigated through spatial whole transcriptome analysis, SA-β-gal activity, p16 and p21 expression, γ-H2AX and senescence-associated secretory phenotype (SASP). Human allogenic liver-derived progenitor cells (HALPC) or dasatinib and quercetin (D+Q) were administrated to two-month-old Wistar rats after bile duct ligation (BDL).

RESULTS

Advanced premature senescence was evidenced in BA livers from early stage and continued to progress until liver transplantation. Senescence and SASP were predominant in cholangiocytes, but also present in surrounding hepatocytes. HALPC but not D+Q reduced the early marker of senescence p21 in BDL rats and improved biliary injury (serum γGT and Sox9 expression) and hepatocytes mass loss (Hnf4a).

CONCLUSIONS

BA livers displayed advanced cellular senescence at diagnosis that continued to progress until liver transplantation. HALPC reduced early senescence and improved liver disease in a preclinical model of BA, providing encouraging preliminary results regarding the use of senotherapies in pediatric biliary cirrhosis.

An involvement of Hippo-yes-associated protein pathway in biliary epithelial senescence in primary biliary cholangitis

BACKGROUND & AIMS

Accumulating evidence suggest that Hippo-yes-associated protein (YAP) pathway plays important roles in development and repair after injuries in biliary system. We disclosed that senescent biliary epithelial cells (BECs) participate in the pathogenesis of primary biliary cholangitis (PBC). We hypothesized that dysregulation of Hippo-YAP pathway may be associated with biliary epithelial senescence in pathogenesis of PBC.

APPROACH & RESULTS

Cellular senescence was induced in cultured BECs by treatment with serum depletion or glycochenodeoxycholic acid. The expression and activity of YAP1 were significantly decreased in senescent BECs (p<0.01). Cellular senescence and apoptosis were significantly increased (p<0.01) and a proliferation activity and a 3D-cyst formation activity were significantly decreased (p<0.01) by a knockdown of YAP1 in BECs. The expression of YAP1 were immunohistochemically determined in livers taken from the patients with PBC (n = 79) and 79 control diseased and normal livers and its association with senescent markers p16^INK4a and p21^WAF1/Cip1 was analyzed. The nuclear expression of YAP1, which indicates activation of YAP1, was significantly decreased in BECs in small bile ducts involved in cholangitis and ductular reactions in PBC, compared to control livers (p<0.01). The decreased expression of YAP1 was seen in senescent BECs showing expression of p16^INK4a and p21^WAF1/Cip1 in bile duct lesions.

CONCLUSION

Dysregulation of Hippo-YAP1 pathway may be involved in the pathogenesis of PBC in association with biliary epithelial senescence.

Recent Advances in Intrahepatic Biliary Epithelial Heterogeneity

Biliary epithelium (i.e., cholangiocytes) is a heterogeneous population of epithelial cells in the liver, which line small and large bile ducts and have individual responses and functions dependent on size and location in the biliary tract. We discuss the recent findings showing that the intrahepatic biliary tree is heterogeneous regarding (1) morphology and function, (2) hormone expression and signaling (3), response to injury, and (4) roles in liver regeneration. This review overviews the significant characteristics and differences of the small and large cholangiocytes. Briefly, it outlines the in vitro and in vivo models used in the heterogeneity evaluation. In conclusion, future studies addressing biliary heterogeneity's role in the pathogenesis of liver diseases characterized by ductular reaction may reveal novel therapeutic approaches.

The role of mitochondria and mitophagy in cell senescence

Mitochondrial malfunction and cell senescence have been defined as the hallmarks of aging. Cell senescence leads to the loss of health allied with aging. While deciphering the complex association between mitochondria and cellular senescence, it is observed that senescence has a two-faced nature being beneficial and hazardous. This duality of cellular senescence is associated with circumstantial aspects. During the process of cellular senescence, dysfunctional mitochondria are accumulated, the efficiency of the oxidative phosphorylation process declines along with the enhanced synthesis of reactive oxygen species. It is suggested that reduction in the negative consequences of senescence throughout old age might be accomplished by targeting the mitochondria as all roads lead towards mitochondria. It is unclear how perturbation of mitophagy in senescence results in the accumulation of mitochondria, impairment of mitochondrial biogenesis and onset of diseases. Understanding this complex interplay will bring about a long yet healthy lifespan. But definitely casual and specific players contribute in the initiation and conservation of the cell senescence. Variations in metabolism, quality control and dynamics of mitochondria are observed during cell aging process. Several On-target and Off-target mechanisms can also cause side effects in cellular senescence. Translational research of these mechanisms may lead to effective clinical interventions. This chapter reviews the role of mitochondria, homeostatic mechanisms and mitophagy as drivers and effectors of cell senescence along with multiple signalling pathways that lead to the initiation, maintenance, induction and suppression of cellular aging process during health and disease.

Role of autophagy in aging: The good, the bad, and the ugly

Autophagy (self-eating) is a conserved catabolic homeostatic process required for cellular metabolic demands by removal of the damaged molecules and organelles and for alleviation of stress initiated by pathology and infection. By such actions, autophagy is essential for the prevention of aging, disease, and cancer. Genetic defects of autophagy genes lead to a host of developmental, metabolic, and pathological aberrations. Similarly, the age-induced decline in autophagy leads to the loss of cellular homeostatic control. Paradoxically, such a valuable mechanism is hijacked by diseases, during tumor progression and by senescence, presumably due to high levels of metabolic demand. Here, we review both the role of autophagy in preventing cellular decline in aging by fulfillment of cellular bioenergetic demands and its contribution to the maintenance of the senescent state and SASP by acting on energy and nutritional sensors and diverse signaling pathways.

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.

Hypoxia-mediated stabilization of HIF1A in prostatic intraepithelial neoplasia promotes cell plasticity and malignant progression

Prostate cancer (PCa) is a leading cause of cancer-related deaths. The slow evolution of precancerous lesions to malignant tumors provides a broad time frame for preventing PCa. To characterize prostatic intraepithelial neoplasia (PIN) progression, we conducted longitudinal studies on Pten^(i)pe-/- mice that recapitulate prostate carcinogenesis in humans. We found that early PINs are hypoxic and that hypoxia-inducible factor 1 alpha (HIF1A) signaling is activated in luminal cells, thus enhancing malignant progression. Luminal HIF1A dampens immune surveillance and drives luminal plasticity, leading to the emergence of cells that overexpress Transglutaminase 2 (TGM2) and have impaired androgen signaling. Elevated TGM2 levels in patients with PCa are associated with shortened progression-free survival after prostatectomy. Last, we show that pharmacologically inhibiting HIF1A impairs cell proliferation and induces apoptosis in PINs. Therefore, our study demonstrates that HIF1A is a target for PCa prevention and that TGM2 is a promising prognostic biomarker of early relapse after prostatectomy.

Mast cells selectively target large cholangiocytes during biliary injury via H2HR-mediated cAMP/pERK1/2 signaling

Bile ducts are heterogenous in structure and function, and primary sclerosing cholangitis (PSC) damages specific bile ducts leading to ductular reaction (DR), mast cell (MC) infiltration, increased histamine release, inflammation, and fibrosis. Bile duct ligation (BDL) induces large duct damage via cyclic adenosine monophosphate (cAMP)/extracellular signal-related protein kinase (ERK) signaling, and large cholangiocytes express H2 histamine receptor (H2HR). We evaluated how MCs interact with large cholangiocytes during cholestasis. Male wild-type (WT) and MC-deficient (Kit^W-sh ) mice 10-12 weeks of age were subjected to BDL for 7 days. Select Kit^W-sh mice were injected with MCs pretreated with control or H2HR antagonist (ranitidine, 25 μm, 48 h) via tail vein injection. In vitro, MC migration toward small mouse cholangiocytes (SMCCs) and large mouse cholangiocytes (LMCCs) treated with lipopolysaccharide or histamine (±ranitidine) was measured. LMCCs were stimulated with MC supernatants pretreated with control, α-methyl-dl-histidine (to block histamine release), or ranitidine. Liver damage, large duct DR/senescence, inflammation, fibrosis, and cAMP/ERK immunoreactivity increased in BDL WT and Kit^W-sh +MC mice but decreased in BDL Kit^W-sh and Kit^W-sh +MC-H2HR mice. In vitro, MCs migrate toward damaged LMCCs (but not SMCCs) blocked by inhibition of H2HR. Loss of MC histamine or MC-H2HR decreases LMCC proliferation, senescence, H2HR, and cAMP/ERK levels. Human PSC livers have increased MC number found near DR, senescent ducts, and H2HR-positive ducts. Conclusion: Infiltrating MCs preferentially interact with large ducts via H2HR signaling promoting biliary and liver damage. Mediation of MCs may be a therapeutic strategy for PSC.

Inhibition of Secretin/Secretin Receptor Axis Ameliorates NAFLD Phenotypes

BACKGROUND AND AIMS

Human NAFLD is characterized at early stages by hepatic steatosis, which may progress to NASH when the liver displays microvesicular steatosis, lobular inflammation, and pericellular fibrosis. The secretin (SCT)/secretin receptor (SCTR) axis promotes biliary senescence and liver fibrosis in cholestatic models through down-regulation of miR-125b signaling. We aim to evaluate the effect of disrupting biliary SCT/SCTR/miR-125b signaling on hepatic steatosis, biliary senescence, and liver fibrosis in NAFLD/NASH.

APPROACH AND RESULTS

In vivo, 4-week-old male wild-type, Sct^-/- and Sctr^-/- mice were fed a control diet or high-fat diet (HFD) for 16 weeks. The expression of SCT/SCTR/miR-125b axis was measured in human NAFLD/NASH liver samples and HFD mouse livers by immunohistochemistry and quantitative PCR. Biliary/hepatocyte senescence, ductular reaction, and liver angiogenesis were evaluated in mouse liver and human NAFLD/NASH liver samples. miR-125b target lipogenesis genes in hepatocytes were screened and validated by custom RT² Profiler PCR array and luciferase assay. Biliary SCT/SCTR expression was increased in human NAFLD/NASH samples and in livers of HFD mice, whereas the expression of miR-125b was decreased. Biliary/hepatocyte senescence, ductular reaction, and liver angiogenesis were observed in human NAFLD/NASH samples as well as HFD mice, which were decreased in Sct^-/- and Sctr^-/- HFD mice. Elovl1 is a lipogenesis gene targeted by miR-125b, and its expression was also decreased in HFD mouse hepatocytes following Sct or Sctr knockout. Bile acid profile in fecal samples have the greatest changes between wild-type mice and Sct^-/- /Sctr^-/- mice.

CONCLUSION

The biliary SCT/SCTR/miR-125b axis promotes liver steatosis by up-regulating lipid biosynthesis gene Elovl1. Targeting the biliary SCT/SCTR/miR-125b axis may be key for ameliorating phenotypes of human NAFLD/NASH.

Drug-Induced Vanishing Bile Duct Syndrome: From Pathogenesis to Diagnosis and Therapeutics

The most concerned issue in the context of drug/herb-induced chronic cholestasis is vanishing bile duct syndrome. The progressive destruction of intrahepatic bile ducts leading to ductopenia is usually not dose dependent, and has a delayed onset that should be suspected when abnormal serum cholestasis enzyme levels persist despite drug withdrawal. Immune-mediated cholangiocyte injury, direct cholangiocyte damage by drugs or their metabolites once in bile, and sustained exposure to toxic bile salts when biliary epithelium protective defenses are impaired are the main mechanisms of cholangiolar damage. Current therapeutic alternatives are scarce and have not shown consistent beneficial effects so far. This review will summarize the current literature on the main diagnostic tools of ductopenia and its histological features, and the differential diagnostic with other ductopenic diseases. In addition, pathomechanisms will be addressed, as well as the connection between them and the supportive and curative strategies for ductopenia management.

Impact of Aging on Liver Cells and Liver Disease: Focus on the Biliary and Vascular Compartments

The aging process is represented by the time-dependent decay in physiologic functions of living beings. Major interest has been focused in recent years on the determinants of this progressive condition due to its correlative relationship with the onset of diseases. Several hallmark features have been observed in aging, such as genetic alterations, mitochondrial impairment, and telomere shortening. At the cellular level, a senescent phenotype has been identified in response to aging that is characterized by a flat appearance, proliferative arrest, and production of specific molecules. The net effect of these cells in the course of diseases is an argument of debate. In fact, while the onset of a senescent phenotype may prevent tumor spreading, these cells appear to support pathological processes in some conditions. Several studies are now focused on clarifying the specific molecular pathways of aging/senescence in different cells, tissues, or organs. Biliary and vascular components, within the liver, have emerged as important determinants of some form of liver disease. In this review we summarize the most recent achievements on aging/senescence, focusing on the biliary and vascular liver system. Conclusion: Several findings, in both preclinical animal models and on human liver specimens, converge in supporting the presence of specific aging hallmarks in the diseases involving these hepatic compartments.

Interferon-induced protein with tetratricopeptide repeats 3 may be a key factor in primary biliary cholangitis

Accumulating studies suggest that senescent biliary epithelial cells (BECs) produce senescence-associated secretory phenotypes (SASPs) and play various roles in the pathogenesis of primary biliary cholangitis (PBC) and other cholangiopathies. We examined comprehensive profiles of senescent BECs and its contribution to the pathogenesis of PBC taking advantage of microarray analysis. cDNA microarray analysis revealed that 1841 genes including CCL2, IFIT3, CPQ were commonly up-regulated in senescent BECs cultured in serum depleted media or media with glycochenodeoxycholic acid. Knockdown of IFIT3 significantly suppressed cellular senescence (p < 0.01) and significantly increased apoptosis (p < 0.01) in BECs treated with serum depletion or glycochenodeoxycholic acid. Significantly increased expression of IFIT3 was seen in senescent BECs in small bile ducts showing cholangitis and in ductular reactions in PBC, compared to control livers (p < 0.01). An inadequate response to UDCA was inversely correlated to the increased expression of IFIT3 in small bile duct in PBC (p < 0.05). In conclusion, the expression of various genes related to immunity and inflammation including SASPs were increased in senescent BECs. Upregulated IFIT3 in senescent BECs may be associated with the pathogenesis of PBC and may be a possible therapeutic target in PBC.

Cholangiocyte senescence in primary sclerosing cholangitis is associated with disease severity and prognosis

Background & Aims

Primary sclerosing cholangitis (PSC) is a rare cholangiopathy of unknown aetiopathogenesis. The aim of this study was to evaluate cellular senescence (CS) marker expression in cholangiocytes of patients with PSC and their correlation with clinical–pathological features and prognosis.

Methods

Thirty-five patients with PSC with at least 1 available liver sampling were included. Clinical laboratory data at the time of liver sampling were collected. The endpoints were survival without liver transplantation (LT), time to LT, and survival without LT or cirrhosis decompensation. Histological grading and staging were assessed according to Nakanuma. Immunohistochemical stains for CS markers, p16^INK4A (p16) and p21^WAF1/Cip1 (p21), were performed and scored by a 3-tier scale based on positivity extent in native bile duct (NBD) and ductular reaction (DR).

Results: p16 expression in NBD and DR was directly correlated with fibrosis (p ≤0.001 for both) and stage (p = 0.006 and p <0.001, respectively). Moreover, p16 in NBD was positively correlated with hepatitis activity (HA) (p = 0.026), whereas p16 in DR was directly correlated with bile duct loss (BDL) (p = 0.005) and metaplastic hepatocytes (MH) (p <0.01). p21 expression in NBD and DR was directly correlated with HA (p = 0.004 and p = 0.043, respectively), fibrosis (p = 0.006 and p <0.001, respectively), stage (p = 0.006 and p = 0.001, respectively), BDL (p = 0.002 and p = 0.03, respectively), and DR and MH (p ≤0.004 for all). By multivariate analysis, p16 expression in DR was independently associated with stage (p = 0.001), fibrosis (p = 0.001), and BDL (p = 0.011). p21 expression in NBD was independently associated with HA (p = 0.012), BDL (p = 0.04), and DR (p = 0.014). Finally, p21 expression in DR was independently associated with LT-free survival, time to LT, and adverse outcome-free survival (p = 0.001, p = 0.017, and p = 0.001, respectively).

Conclusions

Cholangiocyte senescence is detectable in all stages of PSC and is associated with histological and clinical disease severity, potentially representing a new prognostic and therapeutic target.

Lay summary

In this study, we showed that cholangiocyte senescence (CS), previously demonstrated in liver of patients with end-stage primary sclerosing cholangitis (PSC), is an early event and is detectable in all disease stages. Moreover, we observed that CS is associated with histological and clinical disease severity and patients’ outcome. Thus, we suggest that CS may represent a new prognostic tool and a potential therapeutic target in PSC.

Clinical trial number

Protocol number 0034435, 08/06/2020.

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Cholangiocyte senescence was previously described in end-stage PSC.

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Cholangiocyte senescence is present in all stages of PSC and may represent an early pathogenic event.

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Cholangiocyte senescence is associated with histological and clinical severity in patients with PSC.

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Cholangiocyte senescence is independently associated with patients’ outcome in PSC.

Human placenta mesenchymal stem cell-derived exosomes delay H2O2-induced aging in mouse cholangioids

Background

Cholangiocyte senescence is an important pathological process in diseases such as primary sclerosing cholangitis (PSC) and primary biliary cirrhosis (PBC). Stem cell/induced pluripotent stem cell-derived exosomes have shown anti-senescence effects in various diseases. We applied novel organoid culture technology to establish and characterize cholangiocyte organoids (cholangioids) with oxidative stress-induced senescence and then investigated whether human placenta mesenchymal stem cell (hPMSC)-derived exosomes exerted a protective effect in senescent cholangioids.

Methods

We identified the growth characteristics of cholangioids by light microscopy and confocal microscopy. Exosomes were introduced concurrently with H₂O₂ into the cholangioids. Using immunohistochemistry and immunofluorescence staining analyses, we assessed the expression patterns of the senescence markers p16^INK4a, p21^WAF1/Cip1, and senescence-associated β-galactosidase (SA-β-gal) and then characterized the mRNA and protein expression levels of chemokines and senescence-associated secretory phenotype (SASP) components.

Results

Well-established cholangioids expressed cholangiocyte-specific markers. Oxidative stress-induced senescence enhanced the expression of the senescence-associated proteins p16^INK4a, p21^WAF1/Cip1, and SA-β-gal in senescent cholangioids compared with the control group. Treatment with hPMSC-derived exosomes delayed the cholangioid aging progress and reduced the levels of SASP components (i.e., interleukin-6 and chemokine CC ligand 2).

Conclusions

Senescent organoids are a potential novel model for better understanding senescence progression in cholangiocytes. hPMSC-derived exosomes exert protective effects against senescent cholangioids under oxidative stress-induced injury by delaying aging and reducing SASP components, which might have therapeutic potential for PSC or PBC.

Autophagy in liver diseases

Autophagy is the liver cell energy recycling system regulating a variety of homeostatic mechanisms. Damaged organelles, lipids and proteins are degraded in the lysosomes and their elements are re-used by the cell. Investigations on autophagy have led to the award of two Nobel Prizes and a health of important reports. In this review we describe the fundamental functions of autophagy in the liver including new data on the regulation of autophagy. Moreover we emphasize the fact that autophagy acts like a two edge sword in many occasions with the most prominent paradigm being its involvement in the initiation and progress of hepatocellular carcinoma. We also focused to the implication of autophagy and its specialized forms of lipophagy and mitophagy in the pathogenesis of various liver diseases. We analyzed autophagy not only in well studied diseases, like alcoholic and nonalcoholic fatty liver and liver fibrosis but also in viral hepatitis, biliary diseases, autoimmune hepatitis and rare diseases including inherited metabolic diseases and also acetaminophene hepatotoxicity. We also stressed the different consequences that activation or impairment of autophagy may have in hepatocytes as opposed to Kupffer cells, sinusoidal endothelial cells or hepatic stellate cells. Finally, we analyzed the limited clinical data compared to the extensive experimental evidence and the possible future therapeutic interventions based on autophagy manipulation.

A novel model of injured liver ductal organoids to investigate cholangiocyte apoptosis with relevance to biliary atresia

PURPOSE

The fibrogenic process in cholangiopathic diseases such as biliary atresia (BA) involves bile duct injury and apoptosis of cholangiocytes, which leads to the progression of liver fibrosis into liver cirrhosis and can result in end-staged liver disease. Recent advances in the development of organoids or mini-organ structures have allowed us to create an ex vivo injury model of the bile duct that mimics bile duct injury in BA. The aim of this experimental study was to develop a novel model of injured intrahepatic cholangiocytes as this can be relevant to BA. Our new model is important for studying the pathophysiological response of bile ducts to injury and the role of cholangiocytes in initiating the fibrogenic cascade. In addition, it has the potential to be used as a tool for developing new treatment strategies for BA.

METHODS

Liver ductal organoids were generated from the liver of healthy neonatal mouse pups. Intrahepatic bile duct fragments were isolated and cultured in Matrigel dome. Injury was induced in the organoids by administration of acetaminophen in culture medium. The organoids were then evaluated for fibrogenic cytokines expression, cell apoptosis marker and cell proliferation marker.

RESULTS

Organoids generated from intrahepatic bile duct fragments organized themselves into single-layer epithelial spheroids with lumen on the inside mimicking in vivo bile ducts. After 24-h exposure to acetaminophen, cholangiocytes in the organoids responded to the injury by increasing expression of fibrogenic cytokines, transforming growth factor beta-1 (TGF-β1) and platelet-derived growth factor-BB (PDGF-BB). This fibrogenic response of injured organoids was associated with increased cholangiocyte apoptosis and decreased cholangiocyte proliferation.

CONCLUSION

To our knowledge this is the first description of cholangiocyte injury in the organoids derived from intrahepatic bile ducts. Our injury model demonstrated that cholangiocyte apoptosis and its fibrogenic response may play a role in initiation of the fibrogenic process in cholangiopathic diseases such as BA. These findings are important for the development of novel therapy to reduce cholangiocyte apoptosis and to halt the early fibrogenic cascade in liver fibrogenesis. This novel injury model can prove very valuable for future research in biliary atresia.

Regulation of autophagy by bile acids and in cholestasis - CholestoPHAGY or CholeSTOPagy

Autophagy is a lysosomal degradation pathway in which the cell self-digests its own components to provide nutrients in harsh environmental conditions. It also represents an opportunity to rid the cell of superfluous and damaged organelles, misfolded proteins or invaded microorganisms. Liver autophagy contributes to basic hepatic functions such as lipid, glycogen and protein turnover. Deregulated hepatic autophagy has been linked to many liver diseases including alpha-1-antitrypsin deficiency, alcoholic and non-alcoholic fatty liver diseases, hepatitis B and C infections, liver fibrosis as well as liver cancer. Recently, bile acids and the bile acid receptor FXR have been implicated in the regulation of hepatic autophagy, which implies a role of autophagy also for cholestatic liver diseases. This review summarizes the current evidence of bile acid mediated effects on autophagy and how this affects cholestatic liver diseases. Although detailed studies are lacking, we suggest a concept that the activity of autophagy in cholestasis depends on the disease stage, where autophagy may be induced at early stages ("cholestophagy") but may be impaired in prolonged cholestatic states ("cholestopagy").

Downregulation of p16 Decreases Biliary Damage and Liver Fibrosis in the Mdr2/ Mouse Model of Primary Sclerosing Cholangitis

Biliary senescence and hepatic fibrosis are hallmarks of cholangiopathies including primary sclerosing cholangitis (PSC). Senescent cholangiocytes display senescence-associated secretory phenotypes [SASPs, e.g., transforming growth factor-1 (TGF-1)] that further increase biliary senescence (by an autocrine loop) and trigger liver fibrosis by paracrine mechanisms. The aim of this study was to determine the effect of p16 inhibition and role of the TGF-1/microRNA (miR)-34a/sirtuin 1 (SIRT1) axis in biliary damage and liver fibrosis in the Mdr2/ mouse model of PSC. We treated (i) in vivo male wild-type (WT) and Mdr2/ mice with p16 Vivo-Morpholino or controls before measuring biliary mass [intrahepatic bile duct mass (IBDM)] and senescence, biliary SASP levels, and liver fibrosis, and (ii) in vitro intrahepatic murine cholangiocyte lines (IMCLs) with small interfering RNA against p16 before measuring the mRNA expression of proliferation, senescence, and fibrosis markers. p16 and miR-34a increased but SIRT1 decreased in Mdr2/ mice and PSC human liver samples compared to controls. p16 immunoreactivity and biliary senescence and SASP levels increased in Mdr2/ mice but decreased in Mdr2/ mice treated with p16 Vivo-Morpholino. The increase in IBDM and hepatic fibrosis (observed in Mdr2/ mice) returned to normal values in Mdr2/ mice treated with p16 Vivo-Morpholino. TGF-1 immunoreactivity and biliary SASPs levels were higher in Mdr2/ compared to those of WT mice but returned to normal values in Mdr2/ mice treated with p16 Vivo-Morpholino. The expression of fibrosis/senescence markers decreased in cholangiocytes from Mdr2/ mice treated with p16 Vivo-Morpholino (compared to Mdr2/ mice) and in IMCLs (after p16 silencing) compared to controls. Modulation of the TGF-1/miR-34a/SIRT1 axis may be important in the management of PSC phenotypes.

[Autoimmune liver diseases]

Autoimmune liver diseases comprise a spectrum of progredient idiopathic inflammatory diseases. Typical histological features of autoimmune hepatitis (AIH) include the pattern of chronic hepatitis with predominant plasma cell-rich interface activity, rosetting of hepatocytes, and emperipolesis. Florid bile duct lesions are the key feature of primary biliary cholangitis (PBC); onion-like periductal fibrosis characterizes the primary sclerosing cholangitis (PSC). Variants of AIH, or overlap syndromes, show intersecting histomorphologic findings with PBC or PSC. The diagnosis of the different autoimmune inflammatory liver diseases is based on clinical presentation, a hepatitic or cholestatic pattern of liver enzymes, immuno-serological findings, image analysis in PSC, and liver biopsy as a facultative or obligatory adjunct. Liver biopsy plays a major role in the diagnosis of AIH, small-duct PSC, AMA-negative PBC, IgG4-related diseases, overlap syndrome, and in the recognition of concurrent liver diseases, especially drug-induced liver diseases. Herewith pathologists can help clinicians find adequate therapy for different autoimmune inflammatory liver diseases.

Complex Cell Type-Specific Roles of Autophagy in Liver Fibrosis and Cirrhosis

The lysosomal degradation pathway, or autophagy, plays a fundamental role in cellular, tissue, and organismal homeostasis. A correlation between dysregulated autophagy and liver fibrosis (including end-stage disease, cirrhosis) is well-established. However, both the up and downregulation of autophagy have been implicated in fibrogenesis. For example, the inhibition of autophagy in hepatocytes and macrophages can enhance liver fibrosis, whereas autophagic activity in hepatic stellate cells and reactive ductular cells is permissive towards fibrogenesis. In this review, the contributions of specific cell types to liver fibrosis as well as the mechanisms underlying the effects of autophagy are summarized. In view of the functional effects of multiple cell types on the complex process of hepatic fibrogenesis, integrated approaches that consider the role of autophagy in each liver cell type should be a focus of future research.

Therapeutic Potential of Autophagy Modulation in Cholangiocarcinoma

Autophagy is a multistep catabolic process through which misfolded, aggregated or mutated proteins and damaged organelles are internalized in membrane vesicles called autophagosomes and ultimately fused to lysosomes for degradation of sequestered components. The multistep nature of the process offers multiple regulation points prone to be deregulated and cause different human diseases but also offers multiple targetable points for designing therapeutic strategies. Cancer cells have evolved to use autophagy as an adaptive mechanism to survive under extremely stressful conditions within the tumor microenvironment, but also to increase invasiveness and resistance to anticancer drugs such as chemotherapy. This review collects clinical evidence of autophagy deregulation during cholangiocarcinogenesis together with preclinical reports evaluating compounds that modulate autophagy to induce cholangiocarcinoma (CCA) cell death. Altogether, experimental data suggest an impairment of autophagy during initial steps of CCA development and increased expression of autophagy markers on established tumors and in invasive phenotypes. Preclinical efficacy of autophagy modulators promoting CCA cell death, reducing invasiveness capacity and resensitizing CCA cells to chemotherapy open novel therapeutic avenues to design more specific and efficient strategies to treat this aggressive cancer.

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.

The aged liver: Beyond cellular senescence

The aging of the population, the increased prevalence of chronic liver diseases in elderly and the need to broaden the list of potential liver donors enjoin us to better understand what is an aged liver. In this review, we provide a brief introduction to cellular senescence, revisit the main morphological and functional modifications of the liver induced by aging, particularly concerning metabolism, immune response and regeneration, and try to elude some of the signalling pathways responsible for these modifications. Finally, we discuss the clinical consequences of aging on chronic liver diseases and the implications of older age for donors and recipients in liver transplantation.

Increased p16INK4a-expressing senescent bile ductular cells are associated with inadequate response to ursodeoxycholic acid in primary biliary cholangitis

BACKGROUND & AIMS

Senescent biliary epithelial cells (BECs) may be involved in the pathophysiology of primary biliary cholangitis (PBC) by secreting senescence-associated secretory phenotypes. We examined an association of the extent of cellular senescence in BECs with clinicopathological features including response to ursodeoxycholic acid (UDCA) and a possibility of senolytic therapy in PBC.

METHODS

The expression of senescent markers (p21^WAF1/Cip1, p16^INK4a) and B-cell lymphoma-extra large (Bcl-xL), a key regulator of senescent cell anti-apoptotic pathway, was immunohistochemically examined in livers from patients with PBC (n = 145) and 103 control livers. Senolytic effect of Bcl-xL inhibitors (A-1331852 and Navitoclax) was examined in senescent murine BECs.

RESULTS

Senescent BECs were increased in small bile ducts in PBC, compared with control livers (p < 0.01). Senescent BECs were increased in ductular reactions in PBC, stage 3-4, compared with PBC, stage 1-2 and control livers (p < 0.01). The extent of senescent BECs in bile ductules was significantly correlated with stage and hepatitis activity (p < 0.01) and the expression of p16^INK4a in bile ductules was significantly correlated to inadequate response to UDCA in PBC (p < 0.01). Double immunofluorescence revealed an increased expression of Bcl-xL in p16^INK4a-positive senescent BECs in PBC. Bcl-xL inhibitors selectively induced apoptosis in senescent murine BECs (p < 0.01).

CONCLUSION

The extent of senescent BECs in small bile ducts and bile ductules was closely related to stage and activity of PBC and the increased expression of p16 ^INK4a in bile ductules was correlated with inadequate response to UDCA.

Cholestatic liver disease results increased production of reactive aldehydes and an atypical periportal hepatic antioxidant response

Cholangiopathies such as primary sclerosing cholangitis (PSC) are chronic liver diseases characterized by increased cholestasis, biliary inflammation and oxidative stress. The objective of this study was to elucidate the impact of cholestatic injury on oxidative stress-related factors. Using hepatic tissue and whole cell liver extracts (LE) isolated from 11-week old C57BL/6J (WT) and Mdr2^KO mice, inflammation and oxidative stress was assessed. Concurrently, specific targets of carbonylation were assessed in LE prepared from murine groups as well as from normal and human patients with end-stage PSC. Identified carbonylated proteins were further evaluated using bioinformatics analyses. Picrosirius red staining revealed extensive fibrosis in Mdr2^KO liver, and fibrosis colocalized with increased periportal inflammatory cells and both acrolein and 4-HNE staining. Western blot analysis revealed elevated periportal expression of antioxidant proteins Cbr3, GSTμ, Prdx5, TrxR1 and HO-1 but not GCLC, GSTπ or catalase in the Mdr2^KO group when compared to WT. From immunohistochemical analysis, increased periportal reactive aldehyde production colocalized with elevated staining of Cbr3, GSTμ and TrxR1 but surprisingly not with Nrf2. Mass spectrometric analysis revealed an increase in carbonylated proteins in the Mdr2^KO and PSC groups compared to respective controls. Gene ontology and KEGG pathway analysis of carbonylated proteins revealed a propensity for increased carbonylation of proteins broadly involved in metabolic processes as well more specifically in Rab-mediated signal transduction, lysosomes and the large ribosomal subunit in human PSC. Western blot analysis of Rab-GTPase expression revealed no significant differences in Mdr2^KO mice when compared to WT livers. In contrast, PSC tissue exhibited decreased levels of Rabs 4, 5 and increased abundance of Rabs 6 and 9a protein. Results herein reveal that cholestasis induces stage-dependent increases in periportal oxidative stress responses and protein carbonylation, potentially contributing to pathogenesis in Mdr2^KO. Furthermore, during early stage cholestasis, there is cell-specific upregulation of some but not all, antioxidant proteins.

Knockdown of vimentin reduces mesenchymal phenotype of cholangiocytes in the Mdr2-/- mouse model of primary sclerosing cholangitis (PSC)

BACKGROUND

Cholangiocytes are the target cells of cholangiopathies including primary sclerosing cholangitis (PSC). Vimentin is an intermediate filament protein that has been found in various types of mesenchymal cells. The aim of this study is to evaluate the role of vimentin in the progression of biliary damage/liver fibrosis and whether there is a mesenchymal phenotype of cholangiocytes in the Mdr2-/- model of PSC.

METHODS

In vivo studies were performed in 12 wk. Mdr2-/- male mice with or without vimentin Vivo-Morpholino treatment and their corresponding control groups. Liver specimens from human PSC patients, human intrahepatic biliary epithelial cells (HIBEpiC) and human hepatic stellate cell lines (HHSteCs) were used to measure changes in epithelial-to-mesenchymal transition (EMT).

FINDINGS

There was increased mesenchymal phenotype of cholangiocytes in Mdr2-/- mice, which was reduced by treatment of vimentin Vivo-Morpholino. Concomitant with reduced vimentin expression, there was decreased liver damage, ductular reaction, biliary senescence, liver fibrosis and TGF-β1 secretion in Mdr2-/- mice treated with vimentin Vivo-Morpholino. Human PSC patients and derived cell lines had increased expression of vimentin and other mesenchymal markers compared to healthy controls and HIBEpiC, respectively. In vitro silencing of vimentin in HIBEpiC suppressed TGF-β1-induced EMT and fibrotic reaction. HHSteCs had decreased fibrotic reaction and increased cellular senescence after stimulation with cholangiocyte supernatant with reduced vimentin levels.

INTERPRETATION

Our study demonstrated that knockdown of vimentin reduces mesenchymal phenotype of cholangiocytes, which leads to decreased biliary senescence and liver fibrosis. Inhibition of vimentin may be a key therapeutic target in the treatment of cholangiopathies including PSC. FUND: National Institutes of Health (NIH) awards, VA Merit awards.

Autophagy and senescence: A new insight in selected human diseases

Senescence and autophagy play important roles in homeostasis. Cellular senescence and autophagy commonly cause several degenerative processes, including oxidative stress, DNA damage, telomere shortening, and oncogenic stress; hence, both events are known to be interrelated. Autophagy is well known for its disruptive effect on human diseases, and it is currently proposed to have a direct effect on triggering senescence and quiescence. However, it is yet to be proven whether autophagy has a positive or negative impact on senescence. It is known that elevated levels of autophagy induce cell death, whereas inadequate autophagy can trigger cellular senescence. Both have important roles in human diseases such as aging, renal degeneration, neurodegenerative disorders, and cancer. Therefore, this review aims to highlight the relevance of senescence and autophagy in selected human ailments through a summary of recent findings on the connection and effects of autophagy and senescence in these diseases.

Common functional alterations identified in blood transcriptome of autoimmune cholestatic liver and inflammatory bowel diseases

Primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and inflammatory bowel diseases (IBDs), including Crohn’s disease (CD) and ulcerative colitis (UC), are heterogeneous chronic autoimmune diseases that may share underlying pathogenic mechanisms. Herein, we compared simultaneously analyzed blood transcriptomes from patients with PBC, PSC, and IBD. Microarray-based measurements were conducted using RNA isolated from whole blood samples from 90, 45, 95 and 93 patients with PBC, PSC, CD, and UC, respectively, and 47 healthy controls. Expression levels of selected transcripts were analyzed by quantitative reverse-transcribed PCR using an independent cohort of 292, 71 and 727 patients with PBC, PSC, and IBD, respectively. Of 4026, 2650 and 4967 probe sets differentially expressed (adjusted p-value < 0.05) in samples from patients with PBC, PSC, and IBD, respectively, compared with healthy controls, 1946 were common to all three comparisons. Functional analyses indicated that most terms enriched for genes differentially expressed in PBC, PSC, and IBD patients compared with healthy controls were related to mitochondrial function, the vesicle endomembrane system, and GTPase-mediated processes. This study indicates that microarray-based profiling of blood gene expression supports research into the molecular mechanisms underlying disease, rather than being useful for selection of diagnostic biomarkers for use in clinical practice.

Liver fibrosis in biliary atresia

BACKGROUND

Biliary atresia (BA) is the most common cause of obstructive jaundice in infants. Although the Kasai procedure has greatly improved the prognosis, most patients still need liver transplantation (LT) for long-term survival. The pathogenesis of BA has not been fully clarified, and liver fibrosis in BA is far beyond biliary obstructive cirrhosis.

DATA SOURCES

Literature reviews were underwent through PubMed. Persistent inflammation, immune response, biliary epithelial-mesenchymal transition, matrix deposition, decompensated angiogenesis, and unique biliary structure development all contribute to the fibrosis process. Observed evidences in such fields have been collected and form the backbone of this review.

RESULTS

Interactions of the multiple pathways accelerate this process.

CONCLUSIONS

Understanding the mechanisms of the liver fibrosis in BA may pave the way to improved survival after the Kasai procedure.

Neoplastic Transformation of the Peribiliary Stem Cell Niche in Cholangiocarcinoma Arisen in Primary Sclerosing Cholangitis

Primary sclerosing cholangitis (PSC) is a chronic inflammatory cholangiopathy frequently complicated by cholangiocarcinoma (CCA). Massive proliferation of biliary tree stem/progenitor cells (BTSCs), expansion of peribiliary glands (PBGs), and dysplasia were observed in PSC. The aims of the present study were to evaluate the involvement of PBGs and BTSCs in CCA which emerged in PSC patients. Specimens from normal liver (n = 5), PSC (n = 20), and PSC-associated CCA (n = 20) were included. Samples were processed for histology, immunohistochemistry, and immunofluorescence. In vitro experiments were performed on human BTSCs, human mucinous primary CCA cell cultures, and human cholangiocyte cell lines (H69). Our results indicated that all CCAs emerging in PSC patients were mucin-producing tumors characterized by PBG involvement and a high expression of stem/progenitor cell markers. Ducts with neoplastic lesions showed higher inflammation, wall thickness, and PBG activation compared to nonneoplastic PSC-affected ducts. CCA showed higher microvascular density and higher expression of nuclear factor kappa B, interleukin-6, interleukin-8, transforming growth factor β, and vascular endothelial growth factor-1 compared to nonneoplastic ducts. CCA cells were characterized by a higher expression of epithelial-to-mesenchymal transition (EMT) traits and by the absence of primary cilia compared to bile ducts and PBG cells in controls and patients with PSC. Our in vitro study demonstrated that lipopolysaccharide and oxysterols (PSC-related stressors) induced the expression of EMT traits, the nuclear factor kappa B pathway, autophagy, and the loss of primary cilia in human BTSCs. Conclusion: CCA arising in patients with PSC is characterized by extensive PBG involvement and by activation of the BTSC niche in these patients, the presence of duct lesions at different stages suggests a progressive tumorigenesis.

The Secretin/Secretin Receptor Axis Modulates Ductular Reaction and Liver Fibrosis through Changes in Transforming Growth Factor-β1-Mediated Biliary Senescence

Activation of the secretin (Sct)/secretin receptor (SR) axis stimulates ductular reaction and liver fibrosis, which are hallmarks of cholangiopathies. Our aim was to define the role of Sct-regulated cellular senescence, and we demonstrated that both ductular reaction and liver fibrosis are significantly reduced in Sct-/-, SR-/-, and Sct-/-/SR-/- bile duct ligated (BDL) mice compared with BDL wild-type mice. The reduction in hepatic fibrosis in Sct-/-, SR-/-, and Sct-/-/SR-/- BDL mice was accompanied by reduced transforming growth factor-β1 levels in serum and cholangiocyte supernatant, as well as decreased expression of markers of cellular senescence in cholangiocytes in contrast to enhanced cellular senescence in hepatic stellate cells compared with BDL wild-type mice. Secretin directly stimulated the senescence of cholangiocytes and regulated, by a paracrine mechanism, the senescence of hepatic stellate cells and liver fibrosis via modulation of transforming growth factor-β1 biliary secretion. Targeting senescent cholangiocytes may represent a novel therapeutic approach for ameliorating hepatic fibrosis during cholestatic liver injury.

Contribution of Resident Stem Cells to Liver and Biliary Tree Regeneration in Human Diseases

Two distinct stem/progenitor cell populations of biliary origin have been identified in the adult liver and biliary tree. Hepatic Stem/progenitor Cells (HpSCs) are bipotent progenitor cells located within the canals of Hering and can be differentiated into mature hepatocytes and cholangiocytes; Biliary Tree Stem/progenitor Cells (BTSCs) are multipotent stem cells located within the peribiliary glands of large intrahepatic and extrahepatic bile ducts and able to differentiate into hepatic and pancreatic lineages. HpSCs and BTSCs are endowed in a specialized niche constituted by supporting cells and extracellular matrix compounds. The actual contribution of these stem cell niches to liver and biliary tree homeostatic regeneration is marginal; this is due to the high replicative capabilities and plasticity of mature parenchymal cells (i.e., hepatocytes and cholangiocytes). However, the study of human liver and biliary diseases disclosed how these stem cell niches are involved in the regenerative response after extensive and/or chronic injuries, with the activation of specific signaling pathways. The present review summarizes the contribution of stem/progenitor cell niches in human liver diseases, underlining mechanisms of activation and clinical implications, including fibrogenesis and disease progression.

Bile duct paucity in childhood-spectrum, profile, and outcome

We studied the etiological spectrum, clinicolaboratory and histological profile, and outcome of infants and children under 18 years of age presenting between December 2010 and May 2016 with histological evidence of paucity of intralobular bile ducts (PILBD, bile ducts to portal tract ratio < 0.6) Post-transplant PILBD was excluded. Of 632 pediatric liver biopsies screened, 70 had PILBD-44 were infants. PILBD was classified histologically into destructive (n = 50) and non-destructive PILBD (n = 20). Presentations were jaundice (98%), organomegaly (94%), pale stools (50%), and pruritus (43%). Infants had more cholestasis but less fibrosis on histology. Overall, 29 required liver transplantation (LT) for portal hypertension (n = 26), decompensation (n = 25), growth failure (n = 20), intractable pruritus (n = 5), and recurrent cholangitis (n = 2). Destructive PILBD has an odds for poor outcome (decompensation or need for LT within 1 year) of 1.53 (95% CI = 1.15-2.04). On binary logistic regression analysis, poor outcome was related to advanced fibrosis on liver biopsy [Exp (B) = 5.46, 95% CI = 1.56-19.04].

CONCLUSION

PILBD was present in 11% of pediatric liver biopsies and has a varied etiological spectrum. Destructive PILBD has poor outcome. Need for LT is guided by the presence of advanced fibrosis. What is Known: • Natural history of syndromic ductal paucity (Alagille syndrome) is complex. • Duct loss is commonly seen with late presentation of biliary atresia. What is New: • The study classifies the etiological spectrum of ductal paucity histologically into destructive and non-destructive. • Destructive duct loss carries poor prognosis regardless of the etiology of liver disease with subsequent need for liver transplantation.

Mechanisms of cholangiocyte responses to injury

Cholangiocytes, epithelial cells that line the biliary epithelium, are the primary target cells for cholangiopathies including primary sclerosing cholangitis and primary biliary cholangitis. Quiescent cholangiocytes respond to biliary damage and acquire an activated neuroendocrine phenotype to maintain the homeostasis of the liver. The typical response of cholangiocytes is proliferation leading to bile duct hyperplasia, which is a characteristic of cholestatic liver diseases. Current studies have identified various signaling pathways that are associated with cholangiocyte proliferation/loss and liver fibrosis in cholangiopathies using human samples and rodent models. Although recent studies have demonstrated that extracellular vesicles and microRNAs could be mediators that regulate these messenger/receptor axes, further studies are required to confirm their roles. This review summarizes current studies of biliary response and cholangiocyte proliferation during cholestatic liver injury with particular emphasis on the secretin/secretin receptor axis. This article is part of a Special Issue entitled: Cholangiocytes in Health and Diseaseedited by Jesus Banales, Marco Marzioni, Nicholas LaRusso and Peter Jansen.

Increased expression of senescence-associated cell cycle regulators in the progression of biliary atresia: an immunohistochemical study

AIMS

Cellular senescence plays a role in tumour suppression and in the pathogenesis of various non-neoplastic diseases, including primary biliary cholangitis and other adult cholangiopathies. Less is known about the role of cellular senescence in cholangiopathies in children. With that in mind, we examined the expression of senescence-associated cell cycle regulators in biliary atresia, the most common form of paediatric obliterative cholangiopathy.

METHODS AND RESULTS

The expression of senescence-associated cell cycle regulators (p16^Ink4a and p21^WAF1/Cip1 ) and a ductular reaction related marker (neural cell adhesion molecule: NCAM) was examined in bile ducts and bile ductules in liver samples taken from the patients with biliary atresia [n = 80; including 23 samples at the time of the Kasai procedure (KP) and 63 obtained from the explanted liver (LT) (six cases with samples at both surgical stages of disease)] and from appropriate controls (n = 17). The degree of ductular reaction and cholestasis was significantly more extensive in LT than KP (P < 0.01). The expression of p16^INK4a and NCAM was significantly more extensive in bile ducts and bile ductules in ductular reaction in both KP and LT compared to controls and in LT compared to KP (P < 0.05). The expression of p21^WAF1/Cip1 was significantly more extensive in bile ducts and bile ductules in KP compared to both LT and controls (P < 0.01).

CONCLUSIONS

Cellular senescence may play a role in the progression of bile duct loss in biliary atresia in a manner similar to that of adult cholangiopathies.

Cholangiocyte autophagy contributes to hepatic cystogenesis in polycystic liver disease and represents a potential therapeutic target

Polycystic liver disease (PLD) is a group of genetic disorders with limited treatment options and significant morbidity. Hepatic cysts arise from cholangiocytes exhibiting a hyperproliferative phenotype. Considering that hyperproliferation of many cell types is associated with alterations in autophagy, we hypothesized that autophagy is altered in PLD cholangiocytes, contributes to hepatic cystogenesis, and might represent a potential therapeutic target. We employed functional pathway cluster analysis and next-generation sequencing, transmission electron microscopy, immunofluorescence confocal microscopy, and western blotting to assess autophagy in human and rodent PLD cholangiocytes. A three-dimensional culture model was used to study the effects of molecular and pharmacologic inhibition of autophagy on hepatic cystogenesis in vitro, and the polycystic kidney disease-specific rat, an animal model of PLD, to study the effects of hydroxychloroquine, a drug that interferes with the autophagy pathway, on disease progression in vivo. Assessment of the transcriptome of PLD cholangiocytes followed by functional pathway cluster analysis revealed that the autophagy-lysosomal pathway is one of the most altered pathways in PLD. Direct evaluation of autophagy in PLD cholangiocytes both in vitro and in vivo showed increased number and size of autophagosomes, lysosomes, and autolysosomes; overexpression of autophagy-related proteins (Atg5, Beclin1, Atg7, and LC3); and enhanced autophagic flux associated with activation of the cAMP-protein kinase A-cAMP response element-binding protein signaling pathway. Molecular and pharmacologic intervention in autophagy with ATG7 small interfering RNA, bafilomycin A₁ , and hydroxychloroquine reduced proliferation of PLD cholangiocytes in vitro and growth of hepatic cysts in three-dimensional cultures. Hydroxychloroquine also efficiently inhibited hepatic cystogenesis in the polycystic kidney disease-specific rat.

CONCLUSION

Autophagy is increased in PLD cholangiocytes, contributes to hepatic cystogenesis, and represents a potential therapeutic target for disease treatment. (Hepatology 2018;67:1088-1108).

Cellular senescence in gastrointestinal diseases: from pathogenesis to therapeutics

Senescence is a durable cell cycle arrest that can be induced in response to various stress factors, such as telomere erosion, DNA damage or the aberrant activation of oncogenes. In addition to its well-established role as a stress response programme, research has revealed important physiological roles of senescence in nondisease settings, such as embryonic development, wound healing, tissue repair and ageing. Senescent cells secrete various cytokines, chemokines, matrix remodelling proteases and growth factors, a phenotype collectively referred to as the senescence-associated secretory phenotype. These factors evoke immune responses that, depending on the pathophysiological context, can either prevent or even fuel disease and tumorigenesis. Remarkably, even the gut microbiota can influence senescence in various organs. In this Review, we provide an introduction to cellular senescence, addressed particularly to gastroenterologists and hepatologists, and discuss the implications of senescence for the pathogenesis of malignant and nonmalignant gastrointestinal and hepatobiliary diseases. We conclude with an outlook on how modulation of cellular senescence might be used for therapeutic purposes.

Gene-disease associations identify a connectome with shared molecular pathways in human cholangiopathies

Cholangiopathies are a diverse group of progressive diseases whose primary cell targets are cholangiocytes. To identify shared pathogenesis and molecular connectivity among the three main human cholangiopathies (biliary atresia [BA], primary biliary cholangitis [PBC], and primary sclerosing cholangitis [PSC]), we built a comprehensive platform of published data on gene variants, gene expression, and functional studies and applied network-based analytics in the search for shared molecular circuits. Mining the data platform with largest connected component and interactome analyses, we validated previously reported associations and identified essential and hub genes. In addition to disease-specific modules, we found a substantial overlap of disease neighborhoods and uncovered a group of 34 core genes that are enriched for immune processes and abnormal intestine/hepatobiliary mouse phenotypes. Within this core, we identified a gene subcore containing signal transduction and activator of transcription 3, interleukin-6, tumor necrosis factor, and forkhead box P3 prominently placed in a regulatory connectome of genes related to cellular immunity and fibrosis. We also found substantial gene enrichment in the advanced glycation endproduct/receptor for advanced glycation endproducts (RAGE) pathway and showed that RAGE activation induced cholangiocyte proliferation. Conclusion: Human cholangiopathies share pathways enriched by immunity genes and a molecular connectome that links different pathogenic features of BA, PBC, and PSC. (Hepatology 2018;67:676-689).

Multifaceted Roles of GSK-3 in Cancer and Autophagy-Related Diseases

GSK-3 is a ubiquitously expressed serine/threonine kinase existing as GSK-3α and GSK-3β isoforms, both active under basal conditions and inactivated upon phosphorylation by different upstream kinases. Initially discovered as a regulator of glycogen synthesis, GSK-3 is also involved in several signaling pathways controlling many different key functions. Here, we discuss recent advances regarding (i) GSK-3 structure, function, regulation, and involvement in several cancers, including hepatocarcinoma, cholangiocarcinoma, breast cancer, prostate cancer, leukemia, and melanoma (active GSK-3 has been shown to induce apoptosis in some cases or inhibit apoptosis in other cases and to induce cancer progression or inhibit tumor cell proliferation, suggesting that different GSK-3 modulators may address different specific targets); (ii) GSK-3 involvement in autophagy modulation, reviewing signaling pathways involved in neurodegenerative and liver diseases; (iii) GSK-3 role in oxidative stress and autophagic cell death, focusing on liver injury; (iv) GSK-3 as a possible therapeutic target of natural substances and synthetic inhibitors in many diseases; and (v) GSK-3 role as modulator of mammalian aging, related to metabolic alterations characterizing senescent cells and age-related diseases. Studies summarized here underline the GSK-3 multifaceted role and indicate such kinase as a molecular target in different pathologies, including diseases associated with autophagy dysregulation.

Biliary bile acids in hepatobiliary injury - What is the link?

The main trigger for liver injury in acquired cholestatic liver disease remains unclear. However, the accumulation of bile acids (BAs) undoubtedly plays a role. Recent progress in deciphering the pathomechanisms of inborn cholestatic liver diseases, decoding mechanisms of BA-induced cell death, and generating modern BA-derived drugs has improved the understanding of the regulation of BA synthesis and transport. Now is the appropriate time to reassess current knowledge about the specific role of BAs in hepatobiliary injury.

Substance P increases liver fibrosis by differential changes in senescence of cholangiocytes and hepatic stellate cells

Substance P (SP) is involved in the proliferation of cholangiocytes in bile duct-ligated (BDL) mice and human cholangiocarcinoma growth by interacting with the neurokinin-1 receptor (NK-1R). To identify whether SP regulates liver fibrosis during cholestasis, wild-type or NK-1R knockout (NK-1R^-/- ) mice that received BDL or sham surgery and multidrug resistance protein 2 knockout (Mdr2^-/- ) mice treated with either an NK-1R antagonist (L-733,060) or saline were used. Additionally, wild-type mice were treated with SP or saline intraperitoneally. In vivo, there was increased expression of tachykinin precursor 1 (coding SP) and NK-1R in both BDL and Mdr2^-/- mice compared to wild-type mice. Expression of tachykinin precursor 1 and NK-1R was significantly higher in liver samples from primary sclerosing cholangitis patients compared to healthy controls. Knockout of NK-1R decreased BDL-induced liver fibrosis, and treatment with L-733,060 resulted in decreased liver fibrosis in Mdr2^-/- mice, which was shown by decreased sirius red staining, fibrosis gene and protein expression, and reduced transforming growth factor-β1 levels in serum and cholangiocyte supernatants. Furthermore, we observed that reduced liver fibrosis in NK-1R^-/- mice with BDL surgery or Mdr2^-/- mice treated with L-733,060 was associated with enhanced cellular senescence of hepatic stellate cells and decreased senescence of cholangiocytes. In vitro, L-733,060 inhibited SP-induced expression of fibrotic genes in hepatic stellate cells and cholangiocytes; treatment with L-733,060 partially reversed the SP-induced decrease of senescence gene expression in cultured hepatic stellate cells and the SP-induced increase of senescence-related gene expression in cultured cholangiocytes.

CONCLUSION

Collectively, our results demonstrate the regulatory effects of the SP/NK-1R axis on liver fibrosis through changes in cellular senescence during cholestatic liver injury. (Hepatology 2017;66:528-541).

NOD2 gene variants confer risk for secondary sclerosing cholangitis in critically ill patients

Sclerosing cholangitis in critically ill patients (SC-CIP) is a progressive cholestatic disease of unknown aetiology characterized by chronic biliary infections. Hence we hypothesized that common NOD2 (nucleotide-binding oligomerisation domain containing 2) gene variants, known risk factors for Crohn's disease and bacterial translocation in liver cirrhosis, increase the odds of developing SC-CIP. Screening of 4,641 endoscopic retrograde cholangiography procedures identified 17 patients with SC-CIP, who were then genotyped for the three common NOD2 mutations (Cohort 1, discovery cohort). To validate the association, we subsequently tested these NOD2 variants in 29 patients from SC-CIP cohorts of three additional medical centers (Cohort 2, replication cohort). In Cohort 1, the NOD2 variants were present in 5 of 17 SC-CIP patients (29.4%), which is twice the frequency of the general population. These results were replicated in Cohort 2 with 8 patients (27.6%) showing NOD2 mutations. In contrast, polymorphisms of hepatocanalicular transporter genes did not have major impact on SC-CIP risk. This first study on genetic susceptibility in SC-CIP patients shows an extraordinary high frequency of NOD2 variation, pointing to a critical role of inherited impaired anti-bacterial defense in the development of this devastating biliary disease.