Epithelial-mesenchymal transition induced by biliary innate immunity contributes to the sclerosing cholangiopathy of biliary atresia

Potential therapeutic target of EGF on bile duct ligation model and biliary atresia children

BACKGROUND

The pathogenesis of liver fibrosis in biliary atresia (BA) is unclear. Epidermal growth factor (EGF) plays a vital role in liver fibrosis. This study aims to investigate the expression of EGF and the mechanisms of its pro-fibrotic effects in BA.

METHODS

EGF levels in serum and liver samples of BA and non-BA children were detected. Marker proteins of EGF signaling and epithelial-mesenchymal transition (EMT) in liver sections were evaluated. Effects of EGF on intrahepatic cells and the underlying mechanisms were explored in vitro. Bile duct ligation (BDL) mice with/without EGF antibody injection were used to verify the effects of EGF on liver fibrosis.

RESULTS

Serum levels and liver expression of EGF elevated in BA. Phosphorylated EGF receptor (p-EGFR) and extracellular regulated kinase 1/2 (p-ERK1/2) increased. In addition, EMT and proliferation of biliary epithelial cells were present in BA liver. In vitro, EGF induced EMT and proliferation of HIBEpic cells and promoted IL-8 expression in L-02 cells by phosphorylating ERK1/2. And EGF activated LX-2 cells. Furthermore, EGF antibody injection reduced p-ERK1/2 levels and alleviated liver fibrosis in BDL mice.

CONCLUSION

EGF is overexpressed in BA. It aggravates liver fibrosis through EGF/EGFR-ERK1/2 pathway, which may be a therapeutic target for BA.

IMPACT

The exact pathogenesis of liver fibrosis in BA is unknown, severely limiting the advancement of BA treatment strategies. This study revealed that serum and liver tissue levels of EGF were increased in BA, and its expression in liver tissues was correlated with the degree of liver fibrosis. EGF may promote EMT and proliferation of biliary epithelial cells and induce IL-8 overexpression in hepatocytes through EGF/EGFR-ERK1/2 signaling pathway. EGF can also activate HSCs in vitro. The EGF/EGFR-ERK1/2 pathway may be a potential therapeutic target for BA.

Modeling bile duct ischemia and reoxygenation injury in human cholangiocyte organoids for screening of novel cholangio-protective agents

BACKGROUND

Ischemia of the bile duct is a common feature in liver disease and transplantation, which represents a major cause of morbidity and mortality, especially after liver transplantation. Detailed knowledge of its pathogenesis remains incomplete due to the lack of appropriate in vitro models.

METHODS

To recapitulate biliary damage induced by ischemia and reperfusion in vitro, human intrahepatic cholangiocyte organoids (ICOs) were grown at low oxygen levels of 1% up to 72 h, followed by re-oxygenation at normal levels.

FINDINGS

ICOs stressed by ischemia and subsequent re-oxygenation represented the dynamic change in biliary cell proliferation, upregulation of epithelial-mesenchymal transition (EMT)-associated markers, and the evocation of phase-dependent cell death programs similar to what is described in patients. Clinical-grade alpha-1 antitrypsin was identified as a potent inhibitor of both ischemia-induced apoptosis and necroptosis.

INTERPRETATION

These findings demonstrate that ICOs recapitulate ischemic cholangiopathy in vitro and enable drug assessment studies for the discovery of new therapeutics for ischemic cholangiopathies.

FUNDING

Dutch Digestive FoundationMLDS D16-26; TKI-LSH (Topconsortium Kennis en Innovatie-Life Sciences & Health) grant RELOAD, EMC-LSH19002; Medical Delta program "Regenerative Medicine 4D"; China Scholarship Council No. 201706230252.

Type-2 epithelial-mesenchymal transition in oral mucosal nonneoplastic diseases

The oral mucosa is a membranous structure comprising epithelial and connective tissue that covers the oral cavity. The oral mucosa is the first immune barrier to protect the body against pathogens for systemic protection. It is frequently exposed to mechanical abrasion, chemical erosion, and pathogenic invasion, resulting in oral mucosal lesions, particularly inflammatory diseases. Epithelial-mesenchymal transition (EMT) is a crucial biological process in the pathogenesis of oral mucosal disorders, which are classified into three types (types 1, 2, and 3) based on their physiological consequences. Among these, type-2 EMT is crucial in wound repair, organ fibrosis, and tissue regeneration. It causes infectious and dis-infectious immunological diseases, such as oral lichen planus (OLP), oral leukoplakia, oral submucosal fibrosis, and other precancerous lesions. However, the mechanism and cognition between type-2 EMT and oral mucosal inflammatory disorders remain unknown. This review first provides a comprehensive evaluation of type-2 EMT in chronically inflammatory oral mucosal disorders. The aim is to lay a foundation for future research and suggest potential treatments.

Reduced peroxisome proliferator-activated receptor-α and bile acid nuclear receptor NR1H4/FXR may affect the hepatic immune microenvironment of biliary atresia

Background

Biliary atresia (BA) is a childhood liver disease characterized by fibrous obstruction and obstruction of the extrahepatic biliary system and is one of the most common and serious biliary disorders in infants. Significant inflammation and fibrosis of the liver and biliary tract are the most prominent features, regardless of the initial damage to the BA. Abnormalities in innate or adaptive immunity have been found in human patients and mouse models of BA. We previously reported that children with BA had abnormal lipid metabolism, including free serum carnitine.

Objective

To study gene and protein expression levels of the hepatic peroxisome proliferator-activated receptor-α (PPARα) signaling pathway and farnesoid X receptor (FXR) in BA and BA fibrosis, and assess their clinical values.

Methods

Low expression of PPARα and NR1H4 (FXR) in BA were validated in the Gene Expression Omnibus database. Functional differences were determined by gene set enrichment analysis based on of PPARα and NR1H4 expression. BA patients from GSE46960 were divided into two clusters by using consensus clustering according to PPARα, NR1H4, and SMAD3 expression levels, and immunoinfiltration analysis was performed. Finally, 58 cases treated in our hospital were used for experimental verification. (IHC: 10 Biliary atresia, 10 choledochal cysts; PCR: 10 Biliary atresia, 14 choledochal cysts; WB: 10 Biliary atresia, 4 choledochal cysts).

Results

Bioinformatics analysis showed that the expression of PPARα, CYP7A1 and NR1H4 (FXR) in the biliary atresia group was significantly lower than in the control group. More BA-specific pathways, including TGFβ signaling pathway, P53 signaling pathway, PI3K-AKT-mTOR signaling pathway, etc., are enriched in BA patients with low PPARα and NR1H4 expression. In addition, low NR1H4 expression is abundant in inflammatory responses, IL6/STAT3 signaling pathways, early estrogen responses, IL2 STAT5 signaling pathways, and TGFβ signaling pathways. The TGFβ signaling pathway was significant in both groups. According to the expression of PPARα, NR1H4 and SMAD3, a key node in TGFβ pathway, BA patients were divided into two clusters using consensus clustering. In cluster 2, SMAD3 expression was high, and PPARα and NR1H4 expression were low. In contrast to cluster 1, immune cell infiltration was higher in cluster 2, which was confirmed by immunohistochemistry. The mRNA and protein levels of PPARα and NR1H4 in BA patients were lower than in the control group by immunohistochemistry, Western blot analysis and real-time PCR.

Conclusions

The downregulation of PPARα and NR1H4 (FXR) signaling pathway may be closely related to biliary atresia.

The Role of GLI in the Regulation of Hepatic Epithelial-Mesenchymal Transition in Biliary Atresia

OBJECTIVE

To study the regulatory role of GLI1/GLI2, a nuclear transcription factor of the Sonic hedgehog (Shh) signaling pathway, in epithelial-mesenchymal transition (EMT) related to hepatic fibrosis in patients with biliary atresia (BA).

METHODS

The messenger RNA (mRNA) and protein expression levels of GLI1/GLI2, Snail/Slug, and other Shh- and EMT-related cytokines were tested in the liver tissues of BA patients and animals. Then, GLI1/GLI2 was silenced and overexpressed in mouse intrahepatic bile duct epithelial cells (mIBECs) and BA animals to investigate changes in the mRNA and protein expression of EMT key factors and liver fibrosis indicators. After silencing and overexpression of GLI1/GLI2, immunofluorescence was used to detect the expression of cytokeratin-19 (CK19) and α-smooth muscle actin (α-SMA) in mIBECs, and hematoxylin and eosin (HE) staining and Masson staining were used to observe the degree of liver fibrosis in the BA animals.

RESULTS

Compared with the control, the mRNA and protein expression levels of GLI2, Snail, vimentin, and α-SMA were significantly increased and those of E-cadherin were significantly decreased in liver tissue from BA patients and animals. Overexpression of GLI2 increased the mRNA and protein expression levels of Snail, vimentin, and α-SMA and that of E-cadherin was significantly decreased in mIBECs and BA animals. After GLI2 silencing, the opposite pattern was observed. Immunofluorescence detection showed enhanced expression of the bile duct epithelial cell marker CK19 in mIBECs after GLI2 silencing and enhanced expression of the mesenchymal cell marker α-SMA after GLI2 overexpression. HE and Masson staining suggested that the GLI2-overexpressing group had a significantly higher degree of fibrosis.

CONCLUSION

The Shh signaling pathway plays an important role in fibrogenesis in BA. GLI2 can significantly regulate EMT in mIBECs and livers of BA mice.

Relationships between congenital peritoneopericardial diaphragmatic hernia or congenital central diaphragmatic hernia and ductal plate malformations in dogs and cats

OBJECTIVE

To characterize the association between peritoneopericardial diaphragmatic hernia (PPDH) or congenital central diaphragmatic hernia (CCDH) and ductal plate malformations (DPMs) in dogs and cats.

ANIMALS

18 dogs and 18 cats with PPDH or CCDH and 19 dogs and 18 cats without PPDH or CCDH.

PROCEDURES

Evaluation of clinical details verified PPDH or CCDH and survival times. Histologic features of nonherniated liver samples were used to categorize DPM. Immunohistochemical staining for cytokeratin-19 distinguished bile duct profiles per portal tract and for Ki-67-assessed cholangiocyte proliferation. Histologic features of herniated liver samples from PPDH or CCDH were compared with those of pathological controls (traumatic diaphragmatic hernia, n = 6; liver lobe torsion, 6; ischemic hepatopathy, 2).

RESULTS

DPM occurred in 13 of 18 dogs with the proliferative-like phenotype predominating and in 15 of 18 cats with evenly distributed proliferative-like and Caroli phenotypes. Congenital hepatic fibrosis DPM was noted in 3 dogs and 2 cats and renal DPM in 3 dogs and 3 cats. No signalment, clinical signs, or clinicopathologic features discriminated DPM. Kaplan Meier survival curves were similar in dogs and cats. Bile duct profiles per portal tract in dogs (median, 5.0; range, 1.4 to 100.8) and cats (6.6; 1.9 to 11.0) with congenital diaphragmatic hernias significantly exceeded those in healthy dogs (1.4; 1.2 to 1.6) and cats (2.3; 1.7 to 2.6). Animals with DPM lacked active cholangiocyte proliferation. Histologic features characterizing malformative bile duct profiles yet without biliary proliferation were preserved in herniated liver lobes in animals with DPM.

CONCLUSIONS AND CLINICAL RELEVANCE

DPM was strongly associated with PPDH and CCDH. Because DPM can impact health, awareness of its coexistence with PPDH or CCDH should prompt biopsy of nonherniated liver tissue during surgical correction of PPDH and CCDH.

Cholangiocyte Epithelial to Mesenchymal Transition (EMT) is a potential molecular mechanism driving ischemic cholangiopathy in liver transplantation

Donation after circulatory death (DCD) has expanded the donor pool for liver transplantation. However, ischemic cholangiopathy (IC) after DCD liver transplantation causes inferior outcomes. The molecular mechanisms of IC are currently unknown but may depend on ischemia-induced genetic reprograming of the biliary epithelium to mesenchymal-like cells. The main objective of this study was to determine if cholangiocytes undergo epithelial to mesenchymal transition (EMT) after exposure to DCD conditions and if this causally contributes to the phenotype of IC. Human cholangiocyte cultures were exposed to periods of warm and cold ischemia to mimic DCD liver donation. EMT was tested by assays of cell migration, cell morphology, and differential gene expression. Transplantation of syngeneic rat livers recovered under DCD conditions were evaluated for EMT changes by immunohistochemistry. Human cholangiocytes exposed to DCD conditions displayed migratory behavior and gene expression patterns consistent with EMT. E-cadherin and CK-7 expressions fell while N-cadherin, vimentin, TGF_β, and SNAIL rose, starting 24 hours and peaking 1–3 weeks after exposure. Cholangiocyte morphology changed from cuboidal (epithelial) before to spindle shaped (mesenchymal) a week after ischemia. These changes were blocked by pretreating cells with the Transforming Growth Factor beta (TGF_β) receptor antagonist Galunisertib (1 μM). Finally, rats with liver isografts cold stored for 20 hours in UW solution and exposed to warm ischemia (30 minutes) at recovery had elevated plasma bilirubin 1 week after transplantation and the liver tissue showed immunohistochemical evidence of early cholangiocyte EMT. Our findings show EMT occurs after exposure of human cholangiocytes to DCD conditions, which may be initiated by upstream signaling from autocrine derived TGFβ to cause mesenchymal specific morphological and migratory changes.

CXCR5 induces perineural invasion of salivary adenoid cystic carcinoma by inhibiting microRNA-187

CXCR5 played critical roles in tumorigenesis and metastasis. Nevertheless, little was known about the involvement of CXCR5 in perineural invasion (PNI) of salivary adenoid cystic carcinoma (SACC). Here, we confirmed upregulation of CXCR5 in SACC specimens and cells and identified that CXCR5 exhibited a significant positive correlation with PNI. Functionally, knockdown of CXCR5 suppressed SACC cells migration, invasion and PNI ability, whereas CXCR5 overexpression displayed the opposite effects. Moreover, CXCR5 downregulated microRNA (miR)-187, which could competitively sponge S100A4. The PNI-inhibitory effect of CXCR5 knockdown or miR-187 overexpression could be reversed by elevated expression of S100A4. Conjointly, our data revealed that CXCR5 facilitated PNI through downregulating miR-187 to disinhibit S100A4 expression in SACC.

Developmental histology of the portal plate in biliary atresia: observations and implications

PURPOSE

The key characteristic of biliary atresia (BA) is obliteration of the extrahepatic bile ducts at the level of the porta hepatis. We aimed to relate the immunohistochemical features of remnant biliary ductules at the porta hepatis with clinical features and outcomes.

METHODS

Samples were immunostained with anti-cytokeratin 20 (CK20), vimentin and alpha-smooth muscle actin (aSMA). Primary outcome was set as clearance of jaundice (bilirubin ≤ 20 μmol/L) following Kasai portoenterostomy (KPE).

RESULTS

Eighty-two cases were classified into syndromic BA (n = 10), cystic BA (n = 7), CMV IgM+ BA (n = 9) and isolated BA (n = 56). CK20 expression was confirmed in 40/82 (49%), and vimentin expression in 19/82 (23%). aSMA was negative in all cases studied. CK20 expression was less common in isolated BA (n = 20/56, 36%) compared to CMV IgM+ BA (n = 8/9, 89%), cystic BA (n = 7/7, 100%) (isolated BA vs non-isolated BA, P = 0.0008). There was no difference in vimentin expression among the sub-groups (isolated BA vs. non-isolated BA; P = 0.39). CoJ was achieved in 52/82 (63%) overall with significant difference depending simply on sub-group [e.g. syndromic BA 9/10 (90%)]. CK20 expression was associated with a diminished rate of CoJ in the entire cohort [CK20+ 32/56 (57%) vs. CK20- 20/26 (77%); P = 0.04]. By contrast no correlation was observed between vimentin expression and CoJ (P = 0.13).

CONCLUSION

CK20+ expression was associated with reduced clearance of jaundice in BA and a trend towards reduced native liver survival.

The Epithelial-to-Mesenchymal Transition as a Possible Therapeutic Target in Fibrotic Disorders

Fibrosis is a chronic and progressive disorder characterized by excessive deposition of extracellular matrix, which leads to scarring and loss of function of the affected organ or tissue. Indeed, the fibrotic process affects a variety of organs and tissues, with specific molecular background. However, two common hallmarks are shared: the crucial role of the transforming growth factor-beta (TGF-β) and the involvement of the inflammation process, that is essential for initiating the fibrotic degeneration. TGF-β in particular but also other cytokines regulate the most common molecular mechanism at the basis of fibrosis, the Epithelial-to-Mesenchymal Transition (EMT). EMT has been extensively studied, but not yet fully explored as a possible therapeutic target for fibrosis. A deeper understanding of the crosstalk between fibrosis and EMT may represent an opportunity for the development of a broadly effective anti-fibrotic therapy. Here we report the evidences of the relationship between EMT and multi-organ fibrosis, and the possible therapeutic approaches that may be developed by exploiting this relationship.

Current Concepts of Biliary Atresia and Matrix Metalloproteinase-7: A Review of Literature

Biliary atresia (BA) is a rare cholangiopathy of infancy in which the bile ducts obliterate, leading to profound cholestasis and liver fibrosis. BA is hypothesized to be caused by a viral insult that leads to over-activation of the immune system. Patients with BA are surgically treated with a Kasai portoenterostomy (KPE), which aims to restore bile flow from the liver to the intestines. After KPE, progressive liver fibrosis is often observed in BA patients, even despite surgical success and clearance of their jaundice. The innate immune response is involved during the initial damage to the cholangiocytes and further differentiation of the adaptive immune response into a T-helper 1 cell (Th1) response. Multiple studies have shown that there is continuing elevation of involved cytokines that can lead to the progressive liver fibrosis. However, the mechanism by which the progressive injury occurs is not fully elucidated. Recently, matrix metalloproteinase-7 (MMP-7) has been investigated to be used as a biomarker to diagnose BA. MMPs are involved in extracellular matrix (ECM) turnover, but also have non-ECM related functions. The role of MMP-7 and other MMPs in liver fibrosis is just starting to be elucidated. Multiple studies have shown that serum MMP-7 measurements are able to accurately diagnose BA in a cohort of cholestatic patients while hepatic MMP-7 expression correlated with BA-related liver fibrosis. While the mechanism by which MMP-7 can be involved in the pathophysiology of BA is unclear, MMP-7 has been investigated in other fibrotic pathologies such as renal and idiopathic pulmonary fibrosis. MMP-7 is involved in Wnt/β-catenin signaling, reducing cell-to-cell contact by shedding of E-cadherin, amplifying inflammation and fibrosis via osteopontin (OPN) and TNF-α while it also appears to play a role in induction of angiogenesis This review aims to describe the current understandings of the pathophysiology of BA. Subsequently, we describe how MMP-7 is involved in other pathologies, such as renal and pulmonary fibrosis. Then, we propose how MMP-7 can potentially be involved in BA. By doing this, we aim to describe the putative role of MMP-7 as a prognostic biomarker in BA and to provide possible new therapeutic and research targets that can be investigated in the future.

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.

Preclinical insights into cholangiopathies: disease modeling and emerging therapeutic targets

INTRODUCTION

The common predominant clinical features of cholangiopathies such as primary sclerosing cholangitis (PSC), primary biliary cholangitis (PBC), and biliary atresia (BA) are biliary damage/senescence and liver fibrosis. Curative therapies are lacking, and liver transplantation is the only option. An understanding of the mechanisms and pathogenesis is needed to develop novel therapies. Previous studies have developed various disease-based research models and have identified candidate therapeutic targets. Areas covered: This review summarizes recent studies performed in preclinical models of cholangiopathies and the current understanding of the pathophysiology representing potential targets for novel therapies. A literature search was conducted in PubMed using the combination of the searched term 'cholangiopathies' with one or two keywords including 'model', 'cholangiocyte', 'animal', or 'fibrosis'. Papers published within five years were obtained. Expert opinion: Access to appropriate research models is a key challenge in cholangiopathy research; establishing more appropriate models for PBC is an important goal. Several preclinical studies have demonstrated promising results and have led to novel therapeutic approaches, especially for PSC. Further studies on the pathophysiology of PBC and BA are necessary to identify candidate targets. Innovative therapeutic approaches such as stem cell transplantation have been introduced, and those therapies could be applied to PSC, PBC, and BA.

Overexpression of E74-Like Factor 5 (ELF5) Inhibits Migration and Invasion of Ovarian Cancer Cells

Background

E74-like factor 5 (ELF5) plays a key role in the processes of cell differentiation, apoptosis, and occurrence of tumors. However, the effect of ELF5 on metastasis and invasion in human ovarian cancer remains poorly understood.

Material/Methods

Quantitative real-time polymerase chain reaction (qPCR) was performed to measure the expression of ELF5. The viability of cells was detected by cell counting kit (CCK-8). Cell apoptosis was tested by flow cytometry. Matrigel plug angiogenesis assay was employed to determine angiogenesis rate. The protein expression levels of vascular endothelial growth factor (VEGF), cleaved caspase-3, B-cell lymphoma 2 (Bcl-2), Bcl-2-associated X protein (Bax), E-cadherin, N-cadherin, Snail, phosphoinositide 3 kinase (PI3K), phosphorylated (p)-PI3K, tyrosine kinase B (AKT), and phosphorylated (p)-AKT were determined by Western blot. Wound-healing assay and Transwell were used to determine invasion and migration.

Results

We found that expression of ELF5 was obviously decreased in ovarian cancer cell lines. The cells viability, invasion and metastasis were inhibited by overexpression ELF5. ELF5 suppressed angiogenesis rate and the expression of VEGF. Changes of the expressions of Bcl-2, cleaved caspase-3 and Bax showed that anti-apoptosis ability was improved by ELF5. ELF5 also repressed N-cadherin and Snail and increased E-cadherin. The expressions of p-PI3K and p-AKT were decreased by ELF5. Further study showed that IGF-I reversed the inhibitory effect of ELF5 on growth and metastasis of SKOV3 cells.

Conclusions

Overexpression of ELF5 promoted the apoptosis and reduced the migration and invasion of ovarian cancer cells; therefore, it could provide a new approach to gene treatment of ovarian carcinoma.

CSF-1/CSF-1R axis is associated with epithelial/mesenchymal hybrid phenotype in epithelial-like inflammatory breast cancer

Inflammatory breast cancer (IBC) is a rare subtype of breast cancer, accounting for 8–10% of breast cancer-associated deaths in the US. Clinical hallmarks of IBC include tumor emboli in lymphatic vessels and E-cadherin overexpression, which supports a type of metastasis referred to as cell cluster-based metastasis, prevalent in IBC. In contrast, we previously reported epithelial-to-mesenchymal transition (EMT)-based progression of IBC, utilizing in vivo xenografts and in vitro Matrigel culture models. To address these two contradictory concepts of IBC metastasis, we used Matrigel culture to induce EMT in a panel of IBC cells. Results revealed Matrigel culture induced vimentin expression in SUM149 and SUM190 IBC cells at the transcriptional and protein levels while maintaining the expression of E-cadherin, a phenomenon referred to as partial EMT. Transcriptional profiling revealed that expression of colony-stimulating factor 1 (CSF-1) was induced in Matrigel culture. When the receptor tyrosine kinase of CSF-1 (CSF-1R) was inhibited by CSF-1R inhibitor BLZ945, the partial EMT was reversed in a dose-dependent manner, indicating that the CSF-1/CSF-1R axis plays a key role in controlling partial EMT. This observation may help reconcile the two contradictory theories of IBC metastasis, EMT vs cell cluster-based metastasis.

TLR3 promotes MMP-9 production in primary human airway epithelial cells through Wnt/β-catenin signaling

Background

Airway epithelial cells (AEC) act as the first line of defence in case of lung infections. They constitute a physical barrier against pathogens and they participate in the initiation of the immune response. Yet, the modalities of pathogen recognition by AEC and the consequences on the epithelial barrier remain poorly documented.

Method

We investigated the response of primary human AEC to viral (polyinosinic-polycytidylic acid, poly(I:C)) and bacterial (lipopolysaccharide, LPS) stimulations in combination with the lung remodeling factor Transforming Growth Factor-β (TGF-β).

Results

We showed a strong production of pro-inflammatory cytokines (Interleukin (IL)-6, Tumor Necrosis Factor α, TNFα) or chemokines (CCL2, CCL3, CCL4, CXCL10, CXCL11) by AEC stimulated with poly(I:C). Cytokine and chemokine production, except CXCL10, was Toll Like Receptor (TLR)-3 dependent and although they express TLR4, we found no cytokine production after LPS stimulation. Poly(I:C), but not LPS, synergised with TGF-β for the production of matrix metalloproteinase-9 (MMP-9) and fibronectin. Mechanistic analyses suggest the secretion of Wnt ligands by AEC along with a degradation of the cellular junctions after poly(I:C) exposure, leading to the release of β-catenin from the cell membrane and stimulation of the Wnt/β-catenin pathway.

Conclusion

Our results highlight the cross talk between TGF-β and TLR signaling in bronchial epithelium and its impact on the remodeling process.

Electronic supplementary material

The online version of this article (10.1186/s12931-017-0690-y) contains supplementary material, which is available to authorized users.

Sclerosing and obstructive cholangiopathy in biliary atresia: mechanisms and association with biliary innate immunity

Biliary atresia (BA) is histologically characterized by a progressive, sclerosing cholangitis and the obstruction of extrahepatic bile ducts. In terms of the etiology and pathogenesis of BA, several viral infections consisting of dsRNA, including Reoviridae, have been implicated. Human biliary epithelial cells (BECs) possess an innate immune system consisting of Toll-like receptors (TLRs). BECs have negative regulatory mechanisms of TLR tolerance to avoid an excessive inflammatory response to lipopolysaccharide (LPS), a TLR4 ligand; however, they lack the tolerance to poly(I:C) (a synthetic analog of viral dsRNA), a TLR3 ligand. Treatment with poly(I:C) induces the expression of the apoptosis-inducer TNF-related apoptosis-inducing ligand (TRAIL), along with the antiviral molecule IFN-β1, and reduces the viability of BECs by enhancing apoptosis. In response, surviving BECs increase their expression of various markers, including basic FGF [an epithelial-mesenchymal transition (EMT)-inducer], S100A4 (a mesenchymal marker), and Snail (a transcriptional factor), and decrease that of epithelial markers such as CK19 and E-cadherin before undergoing EMT. Extrahepatic bile ducts in BA infants frequently show a lack of epithelial markers and an aberrant expression of vimentin, in addition to the enhancement of TRAIL and apoptosis. dsRNA viruses may directly induce apoptosis and EMT in human BECs as a result of the biliary innate immune response, supporting the notion that Reoviridae infections may be directly associated with the pathogenesis of cholangiopathies in BA.

Oval Cells Contribute to Fibrogenesis of Marginal Liver Grafts under Stepwise Regulation of Aldose Reductase and Notch Signaling

Background and Aims: Expanded donor criteria poses increased risk for late phase complications such as fibrosis that lead to graft dysfunction in liver transplantation. There remains a need to elucidate the precise mechanisms of post-transplant liver damage in order to improve the long-term outcomes of marginal liver grafts. In this study, we aimed to examine the role of oval cells in fibrogenic development of marginal liver grafts and explore the underlying mechanisms.

Methods: Using an orthotopic rat liver transplantation model and human post-transplant liver biopsy tissues, the dynamics of oval cells in marginal liver grafts was evaluated by the platform integrating immuno-labeling techniques and ultrastructure examination. Underlying mechanisms were further explored in oval cells and an Aldose reductase (AR) knockout mouse model simulating marginal graft injury.

Results: We demonstrated that activation of aldose reductase initiated oval cell proliferation in small-for-size fatty grafts during ductular reaction at the early phase after transplantation. These proliferative oval cells subsequently showed prevailing biliary differentiation and exhibited features of mesenchymal transition including dynamically co-expressing epithelial and mesenchymal markers, developing microstructures for extra-cellular matrix degradation (podosomes) or cell migration (filopodia and blebs), and acquiring the capacity in collagen production. Mechanistic studies further indicated that transition of oval cell-derived biliary cells toward mesenchymal phenotype ensued fibrogenesis in marginal grafts under the regulation of notch signaling pathway.

Conclusions: Oval cell activation and their subsequent lineage commitment contribute to post-transplant fibrogenesis of small-for-size fatty liver grafts. Interventions targeting oval cell dynamics may serve as potential strategies to refine current clinical management.

Emerging concepts in biliary repair and fibrosis

Chronic diseases of the biliary tree (cholangiopathies) represent one of the major unmet needs in clinical hepatology and a significant knowledge gap in liver pathophysiology. The common theme in cholangiopathies is that the target of the disease is the biliary tree. After damage to the biliary epithelium, inflammatory changes stimulate a reparative response with proliferation of cholangiocytes and restoration of the biliary architecture, owing to the reactivation of a variety of morphogenetic signals. Chronic damage and inflammation will ultimately result in pathological repair with generation of biliary fibrosis and clinical progression of the disease. The hallmark of pathological biliary repair is the appearance of reactive ductular cells, a population of cholangiocyte-like epithelial cells of unclear and likely mixed origin that are able to orchestrate a complex process that involves a number of different cell types, under joint control of inflammatory and morphogenetic signals. Several questions remain open concerning the histogenesis of reactive ductular cells, their role in liver repair, their mechanism of activation, and the signals exchanged with the other cellular elements cooperating in the reparative process. This review contributes to the current debate by highlighting a number of new concepts derived from the study of the pathophysiology of chronic cholangiopathies, such as congenital hepatic fibrosis, biliary atresia, and Alagille syndrome.

Poly I:C induces collective migration of HaCaT keratinocytes via IL-8

Background

Delayed wound healing reduces the quality of life (QOL) of patients. Thus, understanding the mechanism of wound healing is indispensable for better management. However, the role of innate immunity in wound healing is thus far unknown. Recently the involvement of TLR3 in wound healing has been evaluated. The systemic administration of polyriboinosinic-polyribocytidylic acid (poly I:C ; a substitute for viral dsRNA and a ligand of toll-like receptor 3), enhances wound healing in vivo. The aim of this study is to improve our understanding of the link between innate immunity and human wound healing, particularly in re-epithelialization.

Results

The present study showed that poly I:C significantly accelerated collective HaCaT cell migration in a scratch assay. Poly I:C also increased IL-8 and bFGF production, and anti-IL-8 antibodies significantly inhibited the migration caused by poly I:C. Human recombinant IL-8 also accelerated collective HaCaT cell migration. An immunofluorescence assay and enzyme-linked immunosorbent assay (ELISA) also revealed that poly I:C decreased E-cadherin protein levels and increased vimentin protein levels, and anti-IL-8 antibody reversed this effect. In contrast, nucleic/cytosolic protein ratios of Snail 1 were unchanged in all tested conditions.

Conclusion

Our findings demonstrated that poly I:C accelerated collective HaCaT cell migration via autocrine/paracrine secretions of IL-8 and the subsequent incomplete epithelial-mesenchymal transition (EMT). Our findings provide a new strategy for wound healing by regulating innate immune systems in re-epithelialization.

Toll-like receptor 3 mediates PROMININ-1 expressing cell expansion in biliary atresia via Transforming Growth Factor-Beta

BACKGROUND

In biliary atresia (BA), epithelial-mesenchymal hepatic progenitor cells (HPC) expressing the stem/progenitor cell marker PROMININ-1 (PROM1) undergo expansion and subsequent transdifferentiation into collagen-producing myofibroblasts within regions of evolving biliary fibrosis under the regulation of Transforming Growth Factor-β (TGFβ) signaling. We hypothesized that pro-inflammatory Toll-like Receptor-3 (TLR3) signal activation promotes the differentiation of PROM1+ HPC via TGFβ pathway activation in vitro.

METHODS

PROM1+ Mat1a(-/-) HPC were treated with a double-stranded RNA analog, polyionosinic-polycytidylic acid (Poly I:C), ± small molecule inhibitors nafamostat, or SB431542.

RESULTS

Poly I:C induced myofibroblastic-like morphologic changes, degradation of IκB-α consistent with TLR3-NFκB activation, a 15-fold increase in the expression of Vimentin, a 9-fold increase in Collagen-1a, a 4.6-fold increase in Snail at 24h (p<0.05), and an 8.2-fold increase in Prom1 at 72h (p<0.0001) by qPCR. Immunofluorescence demonstrated nuclear phosphorylated SMAD3, TLR3, and COLLAGEN-1α staining following Poly I:C treatment. Degradation of IκBα was inhibited by nafamostat. Co-treatment with either nafamostat or SB431542 blocked the morphologic change and abrogated the increased expression of Cd133, Collagen, Vimentin, and Snail1.

CONCLUSIONS

TLR3 activation induces myofibroblastic differentiation of PROM1+ HPC in part via TGFβ pathway activation to promote BA-associated biliary fibrosis.

Epithelial-to-mesenchymal transition and hepatolithiasis

Epithelial-to-mesenchymal transition (EMT) is a complex physiological and pathological process in which epithelial cells acquire mesenchymal characteristics. EMT occurs during embryogenesis and organ development, wound healing and organ regeneration, tumor migration and invasion. In recent years, cholangiocytes have been shown to undergo EMT in different cholangiopathies including hepatolithiasis. Transforming growth factor-β/Smads signaling is considered the master regulator. The purpose of this article is to introduce the concept and type of EMT, summarize recent advances that support or refute the concept that cholangiocytes are capable of phenotype transition of hepaticlithiasis and discuss the probable mechanism.

Ductal Plate Malformation in the Liver of Boxer Dogs: Clinical and Histological Features

Ductal plate malformations (DPMs) represent developmental biliary disorders with a wide phenotypic spectrum. This study characterizes DPM in 30 Boxer dogs. Median age was 1.5 (range, 0.3-10.0) years, with 12 dogs <1 year. Clinical features included increased serum levels of liver enzymes (28), gastrointestinal signs (16), poor body condition (14), abdominal effusion (9), and hepatic encephalopathy (2). Additional malformations included gallbladder atresia (8), atrophied left liver (2), absent quadrate lobe with left-displaced gallbladder (1), portal vasculature atresia (left liver, 1), intrahepatic portosystemic shunt (1), and complex intrahepatic arteriovenous malformation (1). All dogs had portal tracts dimensionally expanded by a moderate-to-severe multiple small bile duct phenotype embedded in abundant extracellular matrix; 80% displayed variable portal-to-portal bridging. Quantitative analysis confirmed significantly increased fibrillar collagen and a 3-fold increased portal tract area relative to 6 Boxer and 10 non-Boxer controls. Biliary phenotype was dominated by tightly formed CK19-positive ductules, typically 10 to 15 μm in diameter, with 3 to >30 profiles per portal tract, reduced luminal apertures, and negative Ki-67 immunoreactivity. CK19-positive biliary epithelium intersected directly with zone 1 hepatocytes as a signature feature when considered with other DPM characteristics. Phenotypic variation included a multiple small bile duct phenotype (all dogs), predominantly thin-walled sacculated ducts (4), well-formed saccular ducts (4), and sacculated segmental, interlobular, and intralobular ducts (Caroli malformation, 2 dogs, one with bridging portal fibrosis). Histologic evidence of portal venous hypoperfusion accompanied increased biliary profiles in every case. We propose that this spectrum of disorders be referred to as DPM with appropriate modifiers to characterize the unique phenotypes.

Revisiting Epithelial-to-Mesenchymal Transition in Liver Fibrosis: Clues for a Better Understanding of the "Reactive" Biliary Epithelial Phenotype

Whether liver epithelial cells contribute to the development of hepatic scarring by undergoing epithelial-to-mesenchymal transition (EMT) is a controversial issue. Herein, we revisit the concept of EMT in cholangiopathies, a group of severe hepatic disorders primarily targeting the bile duct epithelial cell (cholangiocyte), leading to progressive portal fibrosis, the main determinant of liver disease progression. Unfortunately, therapies able to halt this process are currently lacking. In cholangiopathies, fibrogenesis is part of ductular reaction, a reparative complex involving epithelial, mesenchymal, and inflammatory cells. Ductular reactive cells (DRC) are cholangiocytes derived from the activation of the hepatic progenitor cell compartment. These cells are arranged into irregular strings and express a “reactive” phenotype, which enables them to extensively crosstalk with the other components of ductular reaction. We will first discuss EMT in liver morphogenesis and then highlight how some of these developmental programs are partly reactivated in DRC. Evidence for “bona fide” EMT changes in cholangiocytes is lacking, but expression of some mesenchymal markers represents a fundamental repair mechanism in response to chronic biliary damage with potential harmful fibrogenetic effects. Understanding microenvironmental cues and signaling perturbations promoting these changes in DRC may help to identify potential targets for new antifibrotic therapies in cholangiopathies.

Liver fibrosis during the development of biliary atresia: Proof of principle in the murine model

BACKGROUND

The murine model of biliary atresia (BA) is used for examining the pathogenesis of BA. The aim of the study was description of the morphological features and illustrating the detailed development of fibrosis using the Biliary Atresia Research Consortium (BARC) system.

METHODS

Neonatal mice were injected intraperitoneally with rhesus rotavirus (RRV) strain (N=17). Healthy mice were the control group (N=29). All mice were sacrificed at 7 or 14days after birth. Two pathologists examined the morphological features using the BARC system; CK19, αSMA and collagen type I were assessed by immunohistochemistry.

RESULTS

In RRV mice, portal fibrous expansion with focal bile duct proliferation and strong portal cellular infiltrate was found in contrast to healthy mice. In RRV mice, CK19 bile duct staining was significantly less or absent (p<0.01), with stronger portal staining of collagen type I (p=0.02). Expansion of staining for αSMA was more in RRV mice (p<0.01), but αSMA portal staining was stronger in healthy mice (p=0.02).

CONCLUSIONS

The morphological features observed in the murine model of BA correspond with the BA characteristics according to the BARC criteria. Fibrosis is an important feature of the model. Therefore, this murine model is useful for investigating the pathogenesis of BA.

Autophagy and senescence in fibrosing cholangiopathies

Fibrosing cholangiopathy such as primary sclerosing cholangitis (PSC) and biliary atresia (BA) is characterized by biliary epithelial injuries and concentric fibrous obliteration of the biliary tree together with inflammatory cell infiltration. In these diseases, inappropriate innate immunity is reported to contribute more to bile duct pathology as compared with various aspects of "classical" autoimmune diseases. Primary biliary cirrhosis (PBC) is characterized by chronic cholangitis with bile duct loss and classical autoimmune features. Cellular senescence of cholangiocytes and a senescence-associated secretory phenotype lead to the production of proinflammatory cytokines and chemokines that may modify the milieu of the bile duct and then trigger fibroinflammatory responses in PSC and PBC. Furthermore, deregulated autophagy might be involved in cholangiocyte senescence and possibly in the autoimmune process in PBC, and the deregulated innate immunity against enteric microbes or their products that is associated with cholangiocyte senescence might result in the fibrosing cholangitis that develops in PBC and PSC. In BA, innate immunity against double-stranded RNA viruses might be involved in cholangiocyte apoptosis and also in the development of the epithelial-mesenchymal transition of cholangiocytes that results in fibrous obliteration of bile ducts. These recent advances in the understanding of immune-mediated biliary diseases represent a paradigm shift: the cholangiocyte is no longer viewed merely as a passive victim of injury; it is now also considered to function as a potential effector in bile duct pathology.

The expression of epithelial-mesenchymal transition-related proteins in biliary epithelial cells is associated with liver fibrosis in biliary atresia

BACKGROUND

The epithelial-mesenchymal transition (EMT) has been implicated as a key mechanism in the pathogenesis of liver fibrosis. The miR-200 family has been shown to inhibit EMT.

METHODS

Liver fibrosis levels were assessed with Masson's trichrome staining of liver samples obtained from biliary atresia (BA) patients. The expressions of cytokeratin-7 (CK-7) and α-smooth muscle actin (α-SMA) in the liver sections were detected by immunohistochemical and immunofluorescent staining. EMTs were induced by transforming growth factor (TGF)-β1 in human biliary epithelial cells (BECs) in vitro.

RESULTS

We showed that the EMT-related proteins CK-7 and α-SMA colocalized to the intrahepatic BECs in the liver sections of patients with BA. The level of α-SMA expression was related to liver fibrosis stage in BA. EMT in primary human intrahepatic BECs was induced by TGF-β1 in vitro. miR-200b is one member of the miR-200 family and significantly inhibited TGF-β1-mediated EMT in BECs.

CONCLUSION

Together, these data suggest that the occurrence of EMT in BECs might contribute to BA fibrosis. miR-200b significantly affects the development and progression of TGF-β1-dependent EMT and fibrosis in vitro.

Intercellular communication in malignant pleural mesothelioma: properties of tunneling nanotubes

Malignant pleural mesothelioma is a particularly aggressive and locally invasive malignancy with a poor prognosis despite advances in understanding of cancer cell biology and development of new therapies. At the cellular level, cultured mesothelioma cells present a mesenchymal appearance and a strong capacity for local cellular invasion. One important but underexplored area of mesothelioma cell biology is intercellular communication. Our group has previously characterized in multiple histological subtypes of mesothelioma a unique cellular protrusion known as tunneling nanotubes (TnTs). TnTs are long, actin filament-based, narrow cytoplasmic extensions that are non-adherent when cultured in vitro and are capable of shuttling cellular cargo between connected cells. Our prior work confirmed the presence of nanotube structures in tumors resected from patients with human mesothelioma. In our current study, we quantified the number of TnTs/cell among various mesothelioma subtypes and normal mesothelial cells using confocal microscopic techniques. We also examined changes in TnT length over time in comparison to cell proliferation. We further examined potential approaches to the in vivo study of TnTs in animal models of cancer. We have developed novel approaches to study TnTs in aggressive solid tumor malignancies and define fundamental characteristics of TnTs in malignant mesothelioma. There is mounting evidence that TnTs play an important role in intercellular communication in mesothelioma and thus merit further investigation of their role in vivo.

Expansion of prominin-1-expressing cells in association with fibrosis of biliary atresia

Biliary atresia (BA), the most common cause of end-stage liver disease and the leading indication for pediatric liver transplantation, is associated with intrahepatic ductular reactions within regions of rapidly expanding periportal biliary fibrosis. Whereas the extent of such biliary fibrosis is a negative predictor of long-term transplant-free survival, the cellular phenotypes involved in the fibrosis are not well established. Using a rhesus rotavirus-induced mouse model of BA, we demonstrate significant expansion of a cell population expressing the putative stem/progenitor cell marker, PROMININ-1 (PROM1), adjacent to ductular reactions within regions of periportal fibrosis. PROM1positive (pos) cells express Collagen-1α1. Subsets of PROM1pos cells coexpress progenitor cell marker CD49f, epithelial marker E-CADHERIN, biliary marker CYTOKERATIN-19, and mesenchymal markers VIMENTIN and alpha-SMOOTH MUSCLE ACTIN (αSMA). Expansion of the PROM1pos cell population is associated with activation of Fibroblast Growth Factor (FGF) and Transforming Growth Factor-beta (TGFβ) signaling. In vitro cotreatment of PROM1-expressing Mat1a-/- hepatic progenitor cells with recombinant human FGF10 and TGFβ1 promotes morphologic transformation toward a myofibroblastic cell phenotype with increased expression of myofibroblastic genes Collagen-1α1, Fibronectin, and α-Sma. Infants with BA demonstrate similar expansion of periportal PROM1pos cells with activated Mothers Against Decapentaplegic Homolog 3 (SMAD3) signaling in association with increased hepatic expression of FGF10, FGFR1, and FGFR2 as well as mesenchymal genes SLUG and SNAIL. Infants with perinatal subtype of BA have higher tissue levels of PROM1 expression than those with embryonic subtype.

CONCLUSION

Expansion of collagen-producing PROM1pos cells within regions of periportal fibrosis is associated with activated FGF and TGFβ pathways in both experimental and human BA. PROM1pos cells may therefore play an important role in the biliary fibrosis of BA.

Epithelial-mesenchymal transition-related protein expression in biliary epithelial cells associated with hepatolithiasis

BACKGROUND AND AIM

Epithelial-mesenchymal transition (EMT) of biliary epithelial cells (BECs) plays major roles in many cholangiopathies. This study evaluated whether EMT of BECs has a role in hepatolithiasis-induced biliary fibrosis and types of BECs that are involved.

METHODS

The expression of EMT-related proteins and epidermal growth factor receptor was evaluated by immunohistochemistry of liver tissues from 102 patients with hepatolithiasis, 32 patients with post-hepatitis cirrhosis, and 48 normal livers. Antibodies against E-cadherin, β-catenin, and cytokeratin were used to identify epithelial cells and antibodies against vimentin, S100A4, podoplanin, and α-smooth muscle actin (α-SMA) were used to identify mesenchymal cells. The relationship between clinical and histological parameters and immunohistochemistry findings in BECs, and the surrounding stroma were evaluated.

RESULTS

Loss of E-cadherin and acquisition of S100A4 and vimentin were observed in BECs. In all BECs, cytokeratin and β-catenin expression were unchanged, while podoplanin and α-SMA were not expressed. Although hepatic fibrosis was more severe in post-hepatitis cirrhosis, EMT of BECs was more widespread in hepatolithiasis. In hepatolithiasis, EMT-related proteins were more highly expressed in small bile ducts than in medium or large bile ducts. Their expression was associated with the severity of biliary fibrosis and the expressions of epidermal growth factor receptor. Expression of α-SMA in fibroblasts from the portal space was closely linked to pathological changes in small bile ducts and EMT-related protein expressions in BECs.

CONCLUSIONS

Proliferating cholangiocytes that form small bile ducts may contribute to cholangiopathies in hepatolithiasis through an EMT-like phenomenon or through interactions with stromal myofibroblasts.

Evidence for and against epithelial-to-mesenchymal transition in the liver

The outcome of liver injury is determined by the success of repair. Liver repair involves replacement of damaged liver tissue with healthy liver epithelial cells (including both hepatocytes and cholangiocytes) and reconstruction of normal liver structure and function. Current dogma posits that replication of surviving mature hepatocytes and cholangiocytes drives the regeneration of liver epithelium after injury, whereas failure of liver repair commonly leads to fibrosis, a scarring condition in which hepatic stellate cells, the main liver-resident mesenchymal cells, play the major role. The present review discusses other mechanisms that might be responsible for the regeneration of new liver epithelial cells and outgrowth of matrix-producing mesenchymal cells during hepatic injury. This theory proposes that, during liver injury, some epithelial cells undergo epithelial-to-mesenchymal transition (EMT), acquire myofibroblastic phenotypes/features, and contribute to fibrogenesis, whereas certain mesenchymal cells (namely hepatic stellate cells and stellate cell-derived myofibroblasts) undergo mesenchymal-to-epithelial transition (MET), revert to epithelial cells, and ultimately differentiate into either hepatocytes or cholangiocytes. Although this theory is highly controversial, it suggests that the balance between EMT and MET modulates the outcome of liver injury. This review summarizes recent advances that support or refute the concept that certain types of liver cells are capable of phenotype transition (i.e., EMT and MET) during both culture conditions and chronic liver injury.

Notch1-Hes1 signalling axis in the tumourigenesis of biliary neuroendocrine tumours

AIMS

Biliary neuroendocrine tumours (NETs) are rare and mostly exist as a component of mixed adenoneuroendocrine carcinomas (MANECs). Although the NET component in biliary MANECs is generally more malignant and clinically more important to the prognosis than the ordinary adenocarcinomatous component, the histogenesis of biliary NET has not been clarified. In this study, the role of the Notch1-Hes1 signalling axis in the histogenesis of biliary NETs was examined.

METHODS

Immunohistochemistry for Notch1, its ligand Jagged1 and Hes1 was performed using surgical specimens from 11 patients with biliary MANEC. Moreover, after the knock-down of Notch1 mRNA expression in a cholangiocarcinoma cell line, the expression of chromogranin A (a neuroendocrine marker) and Ascl1 (a neuroendocrine-inducing molecule inhibited by activated Hes1) was examined by quantitative PCR.

RESULTS

Histological examination revealed that the adenocarcinomatous components were predominately located at the luminal surface of the MANEC and the majority of stromal invasion involved NET components. Ordinary adenocarcinomas and non-neoplastic biliary epithelium constantly expressed Notch1, Jagged1 and Hes1, but the expression of Notch1 and Hes1 was decreased or absent in NET components, suggesting interference with the Notch1-Hes1 signalling axis in biliary NET. Moreover, in the cholangiocarcinoma cell line in which the expression of Notch1 mRNA was knocked down, the mRNA expression of Ascl1 and chromogranin A was increased.

CONCLUSIONS

The Notch1-Hes1 signalling axis suppresses neuroendocrine differentiation and maintains tubular/acinar features in adenocarcinoma and non-neoplastic epithelium in the biliary tree. Moreover, a disruption of this signalling axis may be associated with the tumourigenesis of NETs in biliary MANEC.

Notch-dependent expression of epithelial-mesenchymal transition markers in cholangiocytes after liver transplantation

AIM

  Epithelial-mesenchymal transition (EMT) has been identified in chronic cholestatic liver diseases, which are characterized by biliary proliferation and fibrosis. Activation of Notch signaling mediates EMT in a variety of epithelial cell types. In the present study, we investigated the role of Notch signaling in the regulation of EMT marker expression in cholangiocytes after liver transplantation.

METHODS

  Orthotopic liver transplantation was performed in Sprague-Dawley rats. Liver tissues and isolated cholangiocytes were collected 1 week after transplantation. The expression of mesenchymal and biliary epithelial markers was evaluated by immunohistochemistry, quantitative polymerase chain reaction (PCR) and western blotting in liver sections and isolated cholangiocytes. Quantitative real-time PCR and western blotting for Jagged1 and HES1 were utilized to evaluate the activation of Notch signaling. Proliferation and migration of cholangiocytes were assessed by 5-bromodeoxyuridine and transwell assays, respectively. Cholangiocyte proliferation, migration and expression of EMT markers were also evaluated following the inhibition of Notch signaling with N,(N-[3,5-difluorophenacetyl]-L-alanyl)-S-phenylglycine t-butylester (γ-secretase inhibitor) and a Jagged1-neutralizing antibody.

RESULTS

  Expression of EMT markers by cholangiocytes was observed in liver grafts and isolated cholangiocytes obtained 1 week after transplantation. Inhibition of Notch signaling prevented the expression of EMT markers in bile ducts of liver sections and isolated cholangiocytes. Cholangiocyte proliferative and migratory capacities were also suppressed by the inhibition of Notch signaling.

CONCLUSION

  Activation of Notch signaling promotes cholangiocyte proliferation and expression of EMT markers after liver transplantation.

The crucial role of cholangiocytes in cholangiopathies

Cholangiopathies are diseases involving the intrahepatic biliary tree. They appear to involve, chronic inflammation of the bile ducts, which can lead to the development of bile duct cholestasis, proliferation/ductopenia, biliary fibrosis, and malignant transformation. Sustained stimulatory insults to biliary epithelial cells can induce a ductular reaction, which has a key role in the initiation and progression of cholangiopathies. The epithelial-mesenchymal interaction between reactive cholangiocytes and mesenchymal cells with the inflammatory infiltrates plays a major role in this pathogenesis. Cytokines, chemokines, growth factors and morphogens mediate these interactions in an autocrine or paracrine manner. The main hepatic myofibroblasts (MFs) in cholangiopathies originate from portal fibroblasts. Hepatic stellate cells and fibrocytes also transform into MFs. Whether cholangiocytes or hepatocytes are a source of MFs via the epithelial-mesenchymal transition (EMT) remains a matter of controversy. Although there have been numerous indirect findings supporting the theory of a cholangiocyte EMT in human tissues, recent studies using lineage tracing methods have demonstrated strong evidence against the EMT. Understanding the pathogenic mechanisms involved in cholangiopathies can allow for better-targeted anti-fibrotic therapies in animal models. Before anti-fibrotic therapies can translate into clinical trials, improved monitoring of the fibrotic progression of cholangiopathies and an accurate assessment regarding the effectiveness of the proposed treatments must be achieved.

Tutorial review for understanding of cholangiopathy

The biliary tree consists of intrahepatic and extrahepatic bile ducts and is lined by biliary epithelial cells (or cholangiocytes). There are also peribiliary glands around the intrahepatic large bile ducts and extrahepatic bile ducts. The biliary tree is a conduit of bile secreted by hepatocytes and biliary epithelial cells and also of the peribiliary glands and has several physiological roles. A number of diseases affect mainly the intrahepatic and extrahepatic biliary tree, and, in this special issue, these cholangiopathies are reviewed in detail with respect to genetics, pathogenesis, and pathology. In this paper, the anatomy and physiology of the biliary tree, basic injuries to biliary epithelial cells from stress and bile duct damage, and representative cholangiopathies are briefly reviewed.

Cholangiopathy with respect to biliary innate immunity

Biliary innate immunity is involved in the pathogenesis of cholangiopathies in cases of biliary disease. Cholangiocytes possess Toll-like receptors (TLRs) which recognize pathogen-associated molecular patterns (PAMPs) and play a pivotal role in the innate immune response. Tolerance to bacterial PAMPs such as lipopolysaccharides is also important to maintain homeostasis in the biliary tree, but tolerance to double-stranded RNA (dsRNA) is not found. Moreover, in primary biliary cirrhosis (PBC) and biliary atresia, biliary innate immunity is closely associated with the dysregulation of the periductal cytokine milieu and the induction of biliary apoptosis and epithelial-mesenchymal transition (EMT), forming in disease-specific cholangiopathy. Biliary innate immunity is associated with the pathogenesis of various cholangiopathies in biliary diseases as well as biliary defense systems.

Enhanced innate immune responsiveness and intolerance to intestinal endotoxins in human biliary epithelial cells contributes to chronic cholangitis

BACKGROUND

Pattern recognition receptors (PRRs) orchestrate the innate immune defence in human biliary epithelial cells (BECs). Tight control of PRR signalling provides tolerance to physiological amounts of intestinal endotoxins in human bile to avoid constant innate immune activation in BECs.

AIMS

We wanted to determine whether inappropriate innate immune responses to intestinal endotoxins contribute to the development and perpetuation of chronic biliary inflammation.

METHODS

We examined PRR-mediated innate immune responses and protective endotoxin tolerance in primary BECs isolated from patients with primary sclerosing cholangitis (PSC), alcoholic liver disease and patients without chronic liver disease. Expression studies comprised northern blots, RT-PCR, Western blots and immunocytochemistry. Functional studies comprised immuno-precipitation Western blots, FACS for endotoxin uptake, and NF-κB activation assays and ELISA for secreted IL-8 and tumour necrosis factor (TNF)-α.

RESULTS

Primary BECs from explanted PSC livers showed reversibly increased TLR and NOD protein expression and activation of the MyD88/IRAK signalling complex. Consecutively, PSC BECs exhibited inappropriate innate immune responses to endotoxins and did not develop immune tolerance after repeated endotoxin exposures. This endotoxin hyper-responsiveness was probably because of the stimulatory effect of abundantly expressed IFN-γ and TNF-α in PSC livers, which stimulated TLR4-mediated endotoxin signalling in BECs, leading to increased TLR4-mediated endotoxin incorporation and impaired inactivation of the TLR4 signalling cascade. As TNF-α inhibition partly restored protective innate immune tolerance, endogenous TNF-α secretion probably contributed to inappropriate endotoxin responses in BECs.

CONCLUSION

Inappropriate innate immune responses to intestinal endotoxins and subsequent endotoxin intolerance because of enhanced PRR signalling in BECs probably contribute to chronic cholangitis.

The H4 histamine receptor agonist, clobenpropit, suppresses human cholangiocarcinoma progression by disruption of epithelial mesenchymal transition and tumor metastasis

Cholangiocarcinoma (CCA) is a biliary cancer arising from damaged bile ducts. Epithelial-mesenchymal transition (EMT) occurs as epithelial cells begin to resemble mesenchymal cells leading to increased invasion potential as the extracellular matrix (ECM) degrades. Histamine exerts its effects by way of four receptors (H1-H4 HRs). Clobenpropit, a potent H4HR agonist, inhibits mammary adenocarcinoma growth. We have shown that (1) cholangiocytes and CCA cells express H1-H4 HRs and (2) the H3HR decreases CCA proliferation. We evaluated the effects of clobenpropit on CCA proliferation, invasion, EMT phenotypes, and ECM degradation. In vitro, we used CCA cell lines to study proliferation, signaling pathways, and the morphological invasive potential. Gene and protein expression of the hepatobiliary epithelial markers CK-7, CK-8, and CK-19, the focal contact protein paxillin, and the mesenchymal markers fibronectin, s100A4, and vimentin were evaluated. Cell invasion across an ECM layer was quantitated and matrix metalloproteinase-1, -2, -3, -9, and -11 gene and protein expression was examined. Evaluation of the specific role of H4HR was performed by genetic knockdown of the H3HR and overexpression of H4HR. Proliferation was evaluated by proliferating cellular nuclear antigen immunoblotting. In vivo, xenograft tumors were treated with either vehicle or clobenpropit for 39 days. Tumor volume was recorded every other day. Clobenpropit significantly decreased CCA proliferation by way of a Ca(2+) -dependent pathway and altered morphological development and invasion. Loss of H3HR expression or overexpression of H4HR significantly decreased CCA proliferation. In vivo, clobenpropit inhibited xenograft tumor growth compared with controls.

CONCLUSION

Modulation of H4HR by clobenpropit disrupts EMT processes, ECM breakdown, and invasion potential and decreases tumor growth. Interruption of tumorigenesis and invasion by histamine may add to therapeutic advances for CCAs.

Lineage tracing demonstrates no evidence of cholangiocyte epithelial-to-mesenchymal transition in murine models of hepatic fibrosis

Whether or not cholangiocytes or their hepatic progenitors undergo an epithelial-to-mesenchymal transition (EMT) to become matrix-producing myofibroblasts during biliary fibrosis is a significant ongoing controversy. To assess whether EMT is active during biliary fibrosis, we used Alfp-Cre × Rosa26-YFP mice, in which the epithelial cells of the liver (hepatocytes, cholangiocytes, and their bipotential progenitors) are heritably labeled at high efficiency with yellow fluorescent protein (YFP). Primary cholangiocytes isolated from our reporter strain were able to undergo EMT in vitro when treated with transforming growth factor-β1 alone or in combination with tumor necrosis factor-α, as indicated by adoption of fibroblastoid morphology, intracellular relocalization of E-cadherin, and expression of α-smooth muscle actin (α-SMA). To determine whether EMT occurs in vivo, we induced liver fibrosis in Alfp-Cre × Rosa26-YFP mice using the bile duct ligation (BDL) (2, 4, and 8 weeks), carbon tetrachloride (CCl(4) ) (3 weeks), and 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC; 2 and 3 weeks) models. In no case did we find evidence of colocalization of YFP with the mesenchymal markers S100A4, vimentin, α-SMA, or procollagen 1α2, although these proteins were abundant in the peribiliary regions.

CONCLUSION

Hepatocytes and cholangiocytes do not undergo EMT in murine models of hepatic fibrosis.

Hedgehog activity, epithelial-mesenchymal transitions, and biliary dysmorphogenesis in biliary atresia

Biliary atresia (BA) is notable for marked ductular reaction and rapid development of fibrosis. Activation of the Hedgehog (Hh) pathway promotes the expansion of populations of immature epithelial cells that coexpress mesenchymal markers and may be profibrogenic. We examined the hypothesis that in BA excessive Hh activation impedes ductular morphogenesis and enhances fibrogenesis by promoting accumulation of immature ductular cells with a mesenchymal phenotype. Livers and remnant extrahepatic ducts from BA patients were evaluated by quantitative reverse-transcription polymerase chain reaction (QRT-PCR) and immunostaining for Hh ligands, target genes, and markers of mesenchymal cells or ductular progenitors. Findings were compared to children with genetic cholestatic disease, age-matched deceased donor controls, and adult controls. Ductular cells isolated from adult rats with and without bile duct ligation were incubated with Hh ligand-enriched medium ± Hh-neutralizing antibody to determine direct effects of Hh ligands on epithelial to mesenchymal transition (EMT) marker expression. Livers from pediatric controls showed greater innate Hh activation than adult controls. In children with BA, both intra- and extrahepatic ductular cells demonstrated striking up-regulation of Hh ligand production and increased expression of Hh target genes. Excessive accumulation of Hh-producing cells and Hh-responsive cells also occurred in other infantile cholestatic diseases. Further analysis of the BA samples demonstrated that immature ductular cells with a mesenchymal phenotype were Hh-responsive. Treating immature ductular cells with Hh ligand-enriched medium induced mesenchymal genes; neutralizing Hh ligands inhibited this.

CONCLUSION

BA is characterized by excessive Hh pathway activity, which stimulates biliary EMT and may contribute to biliary dysmorphogenesis. Other cholestatic diseases show similar activation, suggesting that this is a common response to cholestatic injury in infancy.

Analysis of biliary epithelial-mesenchymal transition in portal tract fibrogenesis in biliary atresia

BACKGROUND

The cellular origin of myofibroblast in the liver fibrosis remains unclear. This study was designed to investigate whether biliary epithelial cells (BECs) undergoing epithelial-mesenchymal transition (EMT) might be found in patients with biliary atresia, thereby serving as a source of fibrotic myofibroblasts.

METHODS

Liver sections from patients with biliary atresia were evaluated to detect antigen for the BECs marker 4 and cytokeratin-7 (CK-7), proteins (fibroblast-specific protein 1, also known S100A4; the collagen chaperone heat shock protein 47, HSP47) characteristically expressed by cells undergoing EMT, as well as myofibroblasts marker a-smooth muscle actin (a-SMA).

RESULTS

Normal bile ducts BECs could express CK-7 and low levels of a-SMA; they did not express S100A4 and HSP47. However, BECs from biliary atresia resulted in increased expression of a-SMA, S100A4, with concurrent transition to a fibroblast-like morphology and decreased expression of AK-7. Furthermore, BECs in biliary atresia were associated with significant bile ductular proliferation and coexpressed both epithelial and mesenchymal markers.

CONCLUSIONS

From significant histologic evidence, the BECs forming small- and medium-sized bile ducts undergoing EMT may account for prominent bile ductular proliferation and directly contribute to fibrogenesis in BA.

Analysis of biliary epithelial-mesenchymal transition in portal tract fibrogenesis in biliary atresia

BACKGROUND

The cellular origin of myofibroblast in the liver fibrosis remains unclear. This study was designed to investigate whether biliary epithelial cells (BECs) undergoing epithelial-mesenchymal transition (EMT) might be found in patients with biliary atresia, thereby serving as a source of fibrotic myofibroblasts.

METHODS

Liver sections from patients with biliary atresia were evaluated to detect antigen for the BECs marker 4 and cytokeratin-7 (CK-7), proteins (fibroblast-specific protein 1, also known S100A4; the collagen chaperone heat shock protein 47, HSP47) characteristically expressed by cells undergoing EMT, as well as myofibroblasts marker a-smooth muscle actin (a-SMA).

RESULTS

Normal bile ducts BECs could express CK-7 and low levels of a-SMA; they did not express S100A4 and HSP47. However, BECs from biliary atresia resulted in increased expression of a-SMA, S100A4, with concurrent transition to a fibroblast-like morphology and decreased expression of AK-7. Furthermore, BECs in biliary atresia were associated with significant bile ductular proliferation and coexpressed both epithelial and mesenchymal markers.

CONCLUSIONS

From significant histologic evidence, the BECs forming small- and medium-sized bile ducts undergoing EMT may account for prominent bile ductular proliferation and directly contribute to fibrogenesis in BA.

Epithelial-mesenchymal interactions in biliary diseases

In most cholangiopathies, liver diseases of different etiologies in which the biliary epithelium is the primary target in the pathogenic sequence, the central mechanism involves inflammation. Inflammation, characterized by pleomorphic peribiliary infiltrate containing fibroblasts, macrophages, lymphocytes, as well as endothelial cells and pericytes, is associated to the emergence of "reactive cholangiocytes." These biliary cells do not possess bile secretory functions, are in contiguity with terminal cholangioles, and are of a less-differentiated phenotype. They have acquired several mesenchymal properties, including motility and ability to secrete a vast number of proinflammatory chemo/cytokines and growth factors along with de novo expression of a rich receptor machinery. These functional properties enable reactive cholangiocytes to establish intimate contacts and to mutually exchange a variety of paracrine signals with the different mesenchymal cell types populating the portal infiltrate. The extensive crosstalk between the epithelial and mesenchymal compartments is the driver of liver repair mechanisms in cholangiopathies, ultimately evolving toward portal fibrosis. Herein, the authors first review the properties of the different cell types involved in their interaction, and then analyze the underlying molecular mechanisms as they relate to liver repair in cholangiopathies.

Cholestatic liver disease in children

Inherited syndromes of intrahepatic cholestasis and biliary atresia are the most common causes of chronic liver disease and the prime indication for liver transplantation in children. Our understanding of the pathogenesis of these diseases has increased substantially by the discovery of genetic mutations in children with intrahepatic cholestasis and the findings that inflammatory circuits are operative at the time of diagnosis of biliary atresia. Building on this solid foundation, recent studies provide new insight into genotype-phenotype relationships and how mutations produce altered bile composition and cholestasis. New evidence exists that although liver transplantation is curative for patients with end-stage liver disease owing to cholestasis, some patients may develop recurrence of cholestasis because of the emergence of autoantibodies that disrupt canalicular function in the new graft. Progress is also evident in biliary atresia, with recent studies identifying candidate modifier genes and directly implicating lymphocytes and inflammatory signals in the pathogenesis of bile duct injury and obstruction.

Biliary innate immunity: function and modulation

Biliary innate immunity is involved in the pathogenesis of cholangiopathies in patients with primary biliary cirrhosis (PBC) and biliary atresia. Biliary epithelial cells possess an innate immune system consisting of the Toll-like receptor (TLR) family and recognize pathogen-associated molecular patterns (PAMPs). Tolerance to bacterial PAMPs such as lipopolysaccharides is also important to maintain homeostasis in the biliary tree, but tolerance to double-stranded RNA (dsRNA) is not found. In PBC, CD4-positive Th17 cells characterized by the secretion of IL-17 are implicated in the chronic inflammation of bile ducts and the presence of Th17 cells around bile ducts is causally associated with the biliary innate immune responses to PAMPs. Moreover, a negative regulator of intracellular TLR signaling, peroxisome proliferator-activated receptor-γ (PPARγ), is involved in the pathogenesis of cholangitis. Immunosuppression using PPARγ ligands may help to attenuate the bile duct damage in PBC patients. In biliary atresia characterized by a progressive, inflammatory, and sclerosing cholangiopathy, dsRNA viruses are speculated to be an etiological agent and to directly induce enhanced biliary apoptosis via the expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL). Moreover, the epithelial-mesenchymal transition (EMT) of biliary epithelial cells is also evoked by the biliary innate immune response to dsRNA.

Toll-like receptor signaling and liver fibrosis

Liver fibrosis occurs as a wound-healing scar response following acute and chronic liver inflammation including alcoholic liver disease, non-alcoholic steatohepatitis, hepatitis B and C, and autoimmune hepatitis. Myofibroblasts, mainly transdifferentiated from hepatic stellate cells, are pivotal cell types that produce fibrillar collagen. The activation of inflammatory cells, including Kupffer cells, is a crucial step for activating hepatic stellate cells. Toll-like receptors (TLRs) are pattern recognition receptors that sense pathogen-associated molecular patterns (PAMPs), which discriminate the products of microorganisms from the host. TLRs are expressed on Kupffer cells, endothelial cells, dendritic cells, biliary epithelial cells, hepatic stellate cells, and hepatocytes in the liver. TLR signaling induces potent innate immune responses in these cell types. The liver is constantly exposed to PAMPs, such as LPS and bacterial DNA through bacterial translocation because there is a unique anatomical link, the portal vein system between liver and intestine. Recent evidence demonstrates the role of TLRs in the activation of hepatic immune cells and stellate cells during liver fibrosis. Moreover, crosstalk between TLR4 signaling and TGF-β signaling in hepatic stellate cells has been reported. This paper highlights the role of TLR signaling in stellate cell activation and the progression of liver fibrosis.

BAMBI (bone morphogenetic protein and activin membrane-bound inhibitor) reveals the involvement of the transforming growth factor-beta family in pain modulation

Transforming growth factors-beta (TGF-betas) signal through type I and type II serine-threonine kinase receptor complexes. During ligand binding, type II receptors recruit and phosphorylate type I receptors, triggering downstream signaling. BAMBI [bone morphogenetic protein (BMP) and activin membrane-bound inhibitor] is a transmembrane pseudoreceptor structurally similar to type I receptors but lacks the intracellular kinase domain. BAMBI modulates negatively pan-TGF-beta family signaling; therefore, it can be used as an instrument for unraveling the roles of these cytokines in the adult CNS. BAMBI is expressed in regions of the CNS involved in pain transmission and modulation. The lack of BAMBI in mutant mice resulted in increased levels of TGF-beta signaling activity, which was associated with attenuation of acute pain behaviors, regardless of the modality of the stimuli (thermal, mechanical, chemical/inflammatory). The nociceptive hyposensitivity exhibited by BAMBI(-/-) mice was reversed by the opioid antagonist naloxone. Moreover, in a model of chronic neuropathic pain, the allodynic responses of BAMBI(-/-) mice also appeared attenuated through a mechanism involving delta-opioid receptor signaling. Basal mRNA and protein levels of precursor proteins of the endogenous opioid peptides proopiomelanocortin (POMC) and proenkephalin (PENK) appeared increased in the spinal cords of BAMBI(-/-). Transcript levels of TGF-betas and their intracellular effectors correlated directly with genes encoding opioid peptides, whereas BAMBI correlated inversely. Furthermore, incubation of spinal cord explants with activin A or BMP-7 increased POMC and/or PENK mRNA levels. Our findings identify TGF-beta family members as modulators of acute and chronic pain perception through the transcriptional regulation of genes encoding the endogenous opioids.

Aberrant DNA methylation profile in cholangiocarcinoma

Cholangiocarcinoma (CCA) is a notoriously lethal epithelial cancer originating from the biliary system. As radical resection offers a poor success rate and limited effective adjuvant modalities exist in its advanced stage, the disease leads to a fairly poor prognosis. As the incidence of CCA is increasing, although the mortality rate remains stable, and few other definite etiologies have yet to be established, renewing our knowledge of its fundamental carcinogenesis is advisable. The latest advances in molecular carcinogenesis have highlighted the roles of epigenetic perturbations and cancer-related inflammation in CCA. This review focuses on the reciprocal effects between aberrant DNA methylation and inflammatory microenvironment in CCA.

Epithelial-mesenchymal transition induced by transforming growth factor-{beta}1/Snail activation aggravates invasive growth of cholangiocarcinoma

Epithelial-mesenchymal transition is an important mechanism behind initiation of cancer invasion and metastasis. This study was performed to clarify the involvement of epithelial-mesenchymal transition in the progression of cholangiocarcinoma. Cholangiocarcinoma cell lines, CCKS-1 and TFK-1, were treated with transforming growth factor-beta1 (TGF-beta1), and the phenotypic changes and invasive activity were examined. Immunohistochemical analysis was performed using tissue sections of cholangiocarcinoma. In vitro, TGF-beta1 induced mesenchymal features in CCKS-1 and TFK-1 characterized by the reduction of E-cadherin and cytokeratin 19 expression and the induction of mesenchymal markers, such as vimentin and S100A4. TGF-beta1 also induced the nuclear expression of Snail, and the invasive activity was significantly increased in both cell lines. Studies using a mouse xenograft model showed that TGF-beta1 worsened the peritoneal dissemination of CCKS-1. All these changes by TGF-beta1 were inhibited by the simultaneous administration of soluble TGF-beta type II receptor. In vivo, six (16%) of 37 cholangiocarcinoma cases showed marked immunoreactivity of Snail in their nuclei. In these six cases, the immuno-expression of cytokeratin 19 was significantly reduced, and the expression of vimentin was significantly increased. The Snail expression significantly correlated with the lymph node metastasis and a poor survival rate of the patients. These results suggest that epithelial-mesenchymal transition induced by TGF-beta1/Snail activation is closely associated with the aggressive growth of cholangiocarcinoma, resulting in a poor prognosis.