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Significance Most epithelia are turned over throughout adult life as cells are lost from the surface and replaced by the proliferation of stem cells. Precise regulation of stem cells by signals from the local microenvironment or niche is important to maintain epithelial homeostasis. Here, using intestinal stem cells of the Drosophila midgut as a model system, we use transcriptome profiling to identify genes expressed specifically in stem and progenitor cells and not their differentiated daughters. We find that stem and progenitor cells express ligands of major developmental signaling pathways to both contribute to the niche and regulate the production of niche signals from other cell types., Epithelial homeostasis requires the precise balance of epithelial stem/progenitor proliferation and differentiation. While many signaling pathways that regulate epithelial stem cells have been identified, it is probable that other regulators remain unidentified. Here, we use gene-expression profiling by targeted DamID to identify the stem/progenitor-specific transcription and signaling factors in the Drosophila midgut. Many signaling pathway components, including ligands of most major pathways, exhibit stem/progenitor-specific expression and have regulatory regions bound by both intrinsic and extrinsic transcription factors. In addition to previously identified stem/progenitor-derived ligands, we show that both the insulin-like factor Ilp6 and TNF ligand eiger are specifically expressed in the stem/progenitors and regulate normal tissue homeostasis. We propose that intestinal stem cells not only integrate multiple signals but also contribute to and regulate the homeostatic signaling microenvironmental niche through the expression of autocrine and paracrine factors.

The loss of epithelial homeostasis and the disruption of normal tissue morphology are hallmarks of tumor development. Here, we ask how the uniform activation oncogene RAS affects the morphology and tissue mechanics in a normal epithelium. We found that inducible induction of HRAS in confined epithelial monolayers on soft substrates drives a morphological transformation of a 2D monolayer into a compact 3D cell aggregate. This transformation was initiated by the loss of monolayer integrity and formation of two distinct cell layers with differential cell-cell junctions, cell-substrate adhesion, and tensional states. Computational modeling revealed how adhesion and active peripheral tension induces inherent mechanical instability in the system, which drives the 2D-to-3D morphological transformation. Consistent with this, removal of epithelial tension through the inhibition of actomyosin contractility halted the process. These findings reveal the mechanisms by which oncogene activation within an epithelium can induce mechanical instability to drive morphological tissue transformation., This work was supported by the Spanish Ministry MICINN/FEDER (grants BFU2016-75101-P and RYC-2014-15559 to V.C., DPI2016-74929-R to J.M., BES-2017-081337 to G.F., and BES-2013-062633 to M.U.), Generalitat de Catalunya (grant no. 2017SGR1278 to J.M.), the IBEC-ICMS Exchange Program fund to A.N. for nanoindentation measurements, and the EMBO long-term fellowship (EMBO ALTF 811-2018) to M.U. H.M. was supported by a CRUK/EPSRC Multi-Disciplinary Project Award (C1529/A23335) and the MRC/UCL Laboratory for Molecular Cell Biology (MC_CF12266). A.N. and B.B. were supported by Cancer Research UK (C1529/A28276). The Spanish Ministry (MICINN) and its funding programs (Severo Ochoa, FPI, and Excelencia) along with the CERCA Program of the Generalitat de Catalunya support research at the IBEC.

The balance between self-renewal and differentiation of intestinal stem cells is essential for intestinal epithelial homeostasis, which can be regulated by dietary cues. Recent evidences indicate that metabolic pathways sense changes in nutritional status to control stem cell fate, which may provide new clues for the prevention of intestinal diseases.

Thyroid hormones (THs) are key endocrine regulators of tissue development and homeostasis. They are constantly released into the bloodstream and help to regulate many cell functions. The principal products released by the follicular epithelial cells are T3 and T4. T4, which is the less active form of TH, is produced in greater amounts than T3, which is the most active form of TH. This mechanism highlights the importance of the peripheral regulation of TH levels that goes beyond the central axis. Skin, muscle, liver, bone and heart are finely regulated by TH. In particular, skin is among the target organs most influenced by TH, which is essential for skin homeostasis. Accordingly, skin diseases are associated with an altered thyroid status. Alopecia, dermatitis and vitiligo are associated with thyroiditis and alopecia and eczema are frequently correlated with the Graves’ disease. However, only in recent decades have studies started to clarify the molecular mechanisms underlying the effects of TH in epidermal homeostasis. Herein, we summarize the most frequent clinical epidermal alterations linked to thyroid diseases and review the principal mechanisms involved in TH control of keratinocyte proliferation and functional differentiation. Our aim is to define the open questions in this field that are beginning to be elucidated thanks to the advent of mouse models of altered TH metabolism and to obtain novel insights into the physiopathological consequences of TH metabolism on the skin.

The intestine is inhabited by a diverse range of microorganisms, which requires the host to employ numerous barrier measures to prevent bacterial invasion. However, the intestinal microbiota additionally acts symbiotically with host cells to maintain epithelial barrier function, and perturbation to this interaction plays a pivotal role in intestinal pathogenesis. In this review, we highlight current findings of how the intestinal microbiota influences host intestinal epithelial cells. In particular, we review the roles of numerous microbial-derived products as well as mechanisms by which these microbial products influence the regulation of intestinal epithelial population dynamics and barrier function.

Airway epithelium exerts an active role in coordinating innate and adaptive immune responses upon external insult exposure. The potential adverse health effects following exposure to airborne products of volcanic activity in the settings of airway diseases, inflammation, and injury of airway epithelial cells are largely unknown. The present study was aimed at assessing the effects of a volcanic fumarole condensate(F5HT;HT=high temperature) from Vulcano Island (Eolie Island) on large (16HBE) and distal (A549) airway epithelial cell lines. Gas chromatography was used to analyze chemical composition of fumarole samples. The selected cell lines were exposed to different concentrations of F5HT condensate (2, 5 and 10%) for 24h and then assessed for MTS (to assess cell metabolism/cell viability),for AnnexinV/Propidium Iodide (to assess cell apoptosis/cell necrosis) and for the expression by flow cytometry of IL-33, an allarmin able to support T helper 2 responses. Fumarole samples taken from the same fumarole at different times contained: water vapor from 70-97%, CO2 from 3-30%, acid gases (H2S,SO2,HCl,HF) around 1% and trace elements of He,Ar, H2,N2,CO. F5HT at 2% and 5% did not significantly affect cell viability/metabolism, cell apoptosis /cell necrosis or IL-33 expression in both 16HBE and A549 cell lines. Differently, in both cell lines the exposure to F5HT at 10% induced a significant decrease of the absorbance in MTS assay and an evident intracellular increase in IL-33 expression without inducing cell necrosi/cell apoptosis. Data herein reported describe for the first time molecular events promoted in large/distal airway epithelial cells exposed to volcanic fumaroles.

Most human papillomaviruses cause inapparent infections, subtly affecting epithelial homeostasis, to ensure genome persistence in the epithelial basal layer. As with conspicuous papillomas, these self-limiting lesions shed viral particles to ensure population level maintenance and depend on a balance between viral gene expression, immune cell stimulation and immune surveillance for persistence. The complex immune evasion strategies, characteristic of high-risk HPV types, also allow the deregulated viral gene expression that underlies neoplasia. Neoplasia occurs at particular epithelial sites where vulnerable cells such as the reserve or cuboidal cells of the cervical transformation zone are found. Beta papillomavirus infection can also predispose an individual with immune deficiencies to the development of cancers. The host control of HPV infections thus involves local interactions between keratinocytes and the adaptive immune response. Effective immune detection and surveillance limits overt disease, leading to HPV persistence as productive microlesions or in a true latent state.

Simple Summary Oral cancer affecting the oral cavity represents the most common cancer of the head and neck region. Oral cancer develops in a multistep process in which normal cells gradually accumulate genetic and epigenetic modifications to evolve into a malignant disease. Mortality for oral cancer patients is high and morbidity has a significant long-term impact on the health and wellbeing of affected individuals, typically resulting in facial disfigurement and a loss of the ability to speak, chew, taste, and swallow. The limited scope to which current treatments are able to control oral cancer underlines the need for novel therapeutic strategies. This review highlights the molecular differences between oral cell proliferation, differentiation and terminal differentiation, defines terminal differentiation as an important tumour suppressive mechanism and establishes a rationale for clinical investigation of differentiation-paired therapies that may improve outcomes in oral cancer. Abstract The oral epithelium is one of the fastest repairing and continuously renewing tissues. Stem cell activation within the basal layer of the oral epithelium fuels the rapid proliferation of multipotent progenitors. Stem cells first undergo asymmetric cell division that requires tightly controlled and orchestrated differentiation networks to maintain the pool of stem cells while producing progenitors fated for differentiation. Rapidly expanding progenitors subsequently commit to advanced differentiation programs towards terminal differentiation, a process that regulates the structural integrity and homeostasis of the oral epithelium. Therefore, the balance between differentiation and terminal differentiation of stem cells and their progeny ensures progenitors commitment to terminal differentiation and prevents epithelial transformation and oral squamous cell carcinoma (OSCC). A recent comprehensive molecular characterization of OSCC revealed that a disruption of terminal differentiation factors is indeed a common OSCC event and is superior to oncogenic activation. Here, we discuss the role of differentiation and terminal differentiation in maintaining oral epithelial homeostasis and define terminal differentiation as a critical tumour suppressive mechanism. We further highlight factors with crucial terminal differentiation functions and detail the underlying consequences of their loss. Switching on terminal differentiation in differentiated progenitors is likely to represent an extremely promising novel avenue that may improve therapeutic interventions against OSCC.

Paneth cells are specialized intestinal epithelial cells that are located at the base of small intestinal crypts and play a vital role in preserving the gut epithelium homeostasis. Paneth cells act as a safeguard from bacterial translocation across the epithelium and constitute the niche for intestinal stem cells in the small intestine by providing multiple niche signals. Recently, Paneth cells have become the focal point of investigations defining the mechanisms underlying the epithelium-microbiome interactions and pathogenesis of chronic gut mucosal inflammation and bacterial infection. Function of Paneth cells is tightly regulated by numerous factors at different levels, while Paneth cell defects have been widely documented in various gut mucosal diseases in humans. The post-transcription events, specific change in mRNA stability and translation by RNA-binding proteins (RBPs) and noncoding RNAs (ncRNAs) are implicated in many aspects of gut mucosal physiology by modulating Paneth cell function. Deregulation of RBPs and ncRNAs and subsequent Paneth cell defects are identified as crucial elements of gut mucosal pathologies. Here, we overview the posttranscriptional regulation of Paneth cells by RBPs and ncRNAs, with a particular focus on the increasing evidence of RBP HuR and long ncRNA H19 in this process. We also discuss the involvement of Paneth cell dysfunction in altered susceptibility of the intestinal epithelium to chronic inflammation and bacterial infection following disrupted expression of HuR and H19.

// Chau-Chyun Sheu 1, 2, 3, * , Ming-Ju Tsai 1, 2, 3, 5, * , Feng-Wei Chen 1 , Kuo-Feng Chang 4 , Wei-An Chang 1, 2 , Inn-Wen Chong 2, 5 , Po-Lin Kuo 1, 6, 7 and Ya-Ling Hsu 1, 7 1 Graduate Institute of Clinical Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan 2 Division of Pulmonary and Critical Care Medicine, Department of Internal Medicine, Kaohsiung Medical University Hospital, Kaohsiung, Taiwan 3 Department of Internal Medicine, School of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan 4 Welgene Biotech Inc, Taipei, Taiwan 5 Department of Respiratory Therapy, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan 6 Center for Biomarkers and Biotech Drugs, Kaohsiung Medical University, Kaohsiung, Taiwan 7 Graduate Institute of Medicine, College of Medicine, Kaohsiung Medical University, Kaohsiung, Taiwan * These authors have contributed equally to this work Correspondence to: Po-Lin Kuo, email: kuopolin@seed.net.tw Ya-Ling Hsu, email: hsuyl326@gmail.com Keywords: next-generation sequencing, bioinformatics, microRNA, airway remodeling, asthma Received: April 23, 2017 Accepted: June 19, 2017 Published: July 31, 2017 ABSTRACT Airway epithelial cells play important roles in airway remodeling. Understanding gene regulations in airway epithelial homeostasis may provide new insights into pathogenesis and treatment of asthma. This study aimed to combine gene expression (GE) microarray, next generation sequencing (NGS), and bioinformatics to explore genetic regulations associated with airway epithelial homeostasis. We analyzed expression profiles of mRNAs (GE microarray) and microRNAs (NGS) in normal and asthmatic bronchial epithelial cells, and identified 9 genes with potential microRNA-mRNA interactions. Of these 9 dysregulated genes, downregulation of MEF2C and MDGA1 were validated in a representative microarray (GSE43696) from the gene expression omnibus (GEO) database. Our findings suggested that upregulated mir-203a may repress MEF2C , a transcription factor, leading to decreased cellular proliferation. In addition, upregulated mir-3065-3p may repress MDGA1 , a cell membrane anchor protein, resulting in suppression of cell-cell adhesion. We also found that KCNJ2 , a potassium channel, was downregulated in severe asthma and may promote epithelial cell apoptosis. We proposed that aberrant regulations of mir-203a- MEF2C and mir-3065-3p- MDGA1 , as well as downregulation of KCNJ2 , play important roles in airway epithelial homeostasis in asthma. These findings provide new perspectives on diagnostic or therapeutic strategies targeting bronchial epithelium for asthma. The approach in this study also provides a new aspect of studying asthma.

Summary Intestinal epithelial renewal is mediated by intestinal stem cells (ISCs) that exist in a state of neutral drift, wherein individual ISC lineages are regularly lost and born but ISC numbers remain constant. To test whether an active mechanism maintains stem cell pools in the Drosophila midgut, we performed partial ISC depletion. In contrast to the mouse intestine, Drosophila ISCs failed to repopulate the gut after partial depletion. Even when the midgut was challenged to regenerate by infection, ISCs retained normal proportions of asymmetric division and ISC pools did not increase. We discovered, however, that the loss of differentiated midgut enterocytes (ECs) slows when ISC division is suppressed and accelerates when ISC division increases. This plasticity in rates of EC turnover appears to facilitate epithelial homeostasis even after stem cell pools are compromised. Our study identifies unique behaviors of Drosophila midgut cells that maintain epithelial homeostasis., Highlights • Drosophila intestinal stem cell (ISC) pools do not recover after partial depletion • Ratio of symmetric/asymmetric ISC divisions remains constant during regeneration • Increasing ISC proliferation increases gut epithelial cell turnover • Decreasing ISC proliferation decreases gut epithelial cell turnover, In this report, Edgar and colleagues showed that intestinal stem cell (ISC) pools are not actively maintained in the fly midgut; ISC pools did not recover after their partial depletion. Nevertheless, despite their compromised ISC pools, midguts maintained normal organ size and cell number, not by more frequent ISC divisions but through decreased midgut cell turnover.

Glucocorticoids (GCs) are important hormones involved in the regulation of multiple physiologic functions. GCs are also widely used in anti-inflammatory/immunosuppressant drugs. GCs are synthesized by the adrenal cortex as part of the hypothalamus-pituitary-adrenal axis and also by intestinal epithelial cells, among other peripheral sites. GCs are one of the main therapy choices for the exacerbations of inflammatory bowel disease, but they are not useful to prolong remission, and development of tolerance with secondary treatment failure is frequent. Thus, GC actions at the intestinal epithelial level are of great importance, both physiologically and pharmacologically. We generated a tamoxifen-inducible nuclear receptor subfamily 3 group C member 1 (NR3C1)

Preclinical human IBD mechanisms is part of five focus areas of the Challenges in IBD research document, which also include environmental triggers, novel technologies, precision medicine and pragmatic clinical research. The Challenges in IBD research document provides a comprehensive overview of current gaps in inflammatory bowel diseases (IBD) research and delivers actionable approaches to address them. It is the result of a multidisciplinary input from scientists, clinicians, patients, and funders, and represents a valuable resource for patient centric research prioritization. In particular, the preclinical human IBD mechanisms manuscript is focused on highlighting the main research gaps in the pathophysiological understanding of human IBD. These research gap areas include: 1) triggers of immune responses; 2) intestinal epithelial homeostasis and wound repair; 3) age-specific pathophysiology; 4) disease complications; 5) heterogeneous response to treatments; and 6) determination of disease location. As an approach to address these research gaps, the prioritization of reverse translation studies is proposed in which clinical observations are the foundation for experimental IBD research in the lab, and for the identification of new therapeutic targets and biomarkers. The use of human samples in validating basic research findings and development of precision medicine solutions is also proposed. This prioritization aims to put emphasis on relevant biochemical pathways and humanized in vitro and in vivo models that extrapolate meaningfully to human IBD, to eventually yield first-in-class and effective therapies.

Epithelial tissue homeostasis is fundamental for the survival and maintenance of a healthy organism. During mammary gland morphogenesis, epithelial cells communicate with their surrounding stroma in order to orchestrate the formation of a functional organ by undergoing multiple cycles of controlled proliferation, epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition, migration and invasion. In cancer cells, these processes are dysregulated. Thus, understanding how normal mammary cells preserve their homeostasis during development is crucial to identify the molecular events inducing breast cancer. Homeostasis of epithelia relies on key specific features: apico-basal polarity, cell cohesion and lumen formation. Here stands our protein of interest, EFA6B, exchange factor for Arf6, hence my interest in studying its role in mammary epithelial cells. During my PhD work, I investigated the role of EFA6B on epithelial integrity.Using CRISPR/Cas9 EFA6B knock-out cells, I showed that the loss of EFA6B deregulates the homeostasis of normal mammary epithelial cells at different levels. First, deleting EFA6B allows the formation of invadopodia rich in integrin ITGBI and metalloprotease MMPI 4. My results indicate that EFA6B KO cells invasion is Cdc42-dependent, supported by increased cell contractility and the formation of protrusive branched structures through the Cdc42/MRCK/pMLC and Cdc42/N-WASP/Arp2/3 signaling pathways. Second, we showed that the loss of EFA6B is associated with the engagement of cells into EMT, revealed by a cadherin switch and an upregulation of EMT transcription factors. Third, coherently with EFA6B roles on junction assembly, its depletion prevented cells from polarizing and forming normal acini with central lumens. Collectively, our data are in agreement with previous results showing a correlation between the loss of EFA6B and the breast cancer claudin-low subtype defined by EMT properties, invasion capacities and a decrease in TJ proteins expression. I also contributed to the characterization of the role of a-actininl as an effector of EFA6A in normal epithelial cells (MDCK), and of EFA6B in a tumorigenic mammary cell line (MCF7). I show that EFA6B and a-actininl by regulating together the apical cellular contractility coordinate the establishment of apico-basal polarity and luminogenesis, two essential processes for functional epithelia. Altogether, these results demonstrate that the loss of EFA6B triggers invasive potentials in normal epithelial cells, and modifies their microenvironment (contractility, degradative invadopodia, alteration of the matrisome). We propose the gene PSD4 encoding for EFA6B as an invasion-suppressor gene that will preserve cells from losing their epithelial features in order to maintain tissue integrity.; L'homéostasie des tissus épithéliaux est fondamentale à la survie et au maintien d'un organisme sain. Au cours de la morphogenèse des glandes mammaires, les cellules épithéliales communiquent avec leur stroma environnant afin d'orchestrer la formation d'un organe fonctionnel en passant par de multiples cycles régulés de prolifération, de transitions épithéliomésenchymateuse (TME) et mésenchymateuse-épithéliale, de migration et d'invasion. Dans les cellules cancéreuses, ces processus sont dérégulés. Il est donc important d'étudier comment les cellules mammaires normales conservent leur homéostasie au cours du développement pour appréhender les événements moléculaires induisant le cancer du sein. L'homéostasie de l'épithélium repose sur le contrôle de propriétés spécifiques : polarité apico-basale, cohésion cellulaire et formation de lumen. Notre protéine d'intérêt EFA6B, facteur d'échange d'Arf6, se trouve au cœur de ces caractéristiques structurelles, d'où mon intérêt à étudier son rôle dans les cellules épithéliales mammaires. Au cours de mes travaux de thèse, j'ai étudié l'impact de la perte d'EFA6B sur l'intégrité épithéliale. En utilisant des cellules épithéliales normales mammaires invalidées pour EFA6B par la technique de CRISPR/Cas9, j'ai démontré que la perte d'EFA6B dérégule fortement l'homéostasie épithéliale à différents niveaux. Premièrement, sa déplétion entraîne la formation d'invadopodes riches en intégrine ITGBI et en métalloprotéase MMP 14. Mes résultats indiquent que l'invasion des cellules EFA6B knock-out dépend de l'activation de Cdc42. Elle est soutenue par une contractilité accrue des cellules et la formation de structures branchées protrusives contrôlées par les voies de signalisation Cdc42/MRCK/P-MLC et Cdc42/NWASP/Arp2/3. Deuxièmement, nous avons montré que la perte d'EFA6B est associée à l'engagement des cellules EFA6B knock-out dans une TME, révélée par un échange de cadhérine et une augmentation de l'expression de facteurs de transcription mésenchymateux. Troisièmement, conformément au rôle d'EFA6B dans l'assemblage des jonctions serrées, sa déplétion empêche les cellules de se polariser et de former des acini avec un lumen central. Collectivement, nos données sont en accord avec des résultats précédemment publiés montrant une corrélation entre la perte d'EFA6B et le sous-type de cancer du sein invasif Claudin-low défini par une signature TME et une perte d'expression des protéines des jonctions serrées. J'ai aussi contribué à la caractérisation du rôle de l'a-actinine 1 comme effecteur d'EFA6A dans des cellules épithéliales normales (MDCK) et d'EFA6B dans une lignée cellulaire mammaire tumorigène (MCF 7). Je montre qu'EFA6B et l'a-actinine 1, en régulant la contractilité cellulaire apicale, coordonnent l'établissement de la polarité apico-basale, la formation des jonctions serrées et du lumen. L'ensemble de ces résultats démontre que la perte d'EFA6B stimule les propriétés invasives de cellules épithéliales normales et impacte leur microenvironnement (contractilité, dégradation de la matrice, altération du matrisome). Nous proposons que le gène PSD4 codant pour EFA6B est un gène suppresseur d'invasion qui contribue à préserver l'intégrité des tissus épithéliaux.

Epithelial tissue homeostasis is fundamental for the survival and maintenance of a healthy organism. During mammary gland morphogenesis, epithelial cells communicate with their surrounding stroma in order to orchestrate the formation of a functional organ by undergoing multiple cycles of controlled proliferation, epithelial-mesenchymal transition (EMT) and mesenchymal-epithelial transition, migration and invasion. In cancer cells, these processes are dysregulated. Thus, understanding how normal mammary cells preserve their homeostasis during development is crucial to identify the molecular events inducing breast cancer. Homeostasis of epithelia relies on key specific features: apico-basal polarity, cell cohesion and lumen formation. Here stands our protein of interest, EFA6B, exchange factor for Arf6, hence my interest in studying its role in mammary epithelial cells. During my PhD work, I investigated the role of EFA6B on epithelial integrity.Using CRISPR/Cas9 EFA6B knock-out cells, I showed that the loss of EFA6B deregulates the homeostasis of normal mammary epithelial cells at different levels. First, deleting EFA6B allows the formation of invadopodia rich in integrin ITGBI and metalloprotease MMPI 4. My results indicate that EFA6B KO cells invasion is Cdc42-dependent, supported by increased cell contractility and the formation of protrusive branched structures through the Cdc42/MRCK/pMLC and Cdc42/N-WASP/Arp2/3 signaling pathways. Second, we showed that the loss of EFA6B is associated with the engagement of cells into EMT, revealed by a cadherin switch and an upregulation of EMT transcription factors. Third, coherently with EFA6B roles on junction assembly, its depletion prevented cells from polarizing and forming normal acini with central lumens. Collectively, our data are in agreement with previous results showing a correlation between the loss of EFA6B and the breast cancer claudin-low subtype defined by EMT properties, invasion capacities and a decrease in TJ proteins expression. I also contributed to the characterization of the role of a-actininl as an effector of EFA6A in normal epithelial cells (MDCK), and of EFA6B in a tumorigenic mammary cell line (MCF7). I show that EFA6B and a-actininl by regulating together the apical cellular contractility coordinate the establishment of apico-basal polarity and luminogenesis, two essential processes for functional epithelia. Altogether, these results demonstrate that the loss of EFA6B triggers invasive potentials in normal epithelial cells, and modifies their microenvironment (contractility, degradative invadopodia, alteration of the matrisome). We propose the gene PSD4 encoding for EFA6B as an invasion-suppressor gene that will preserve cells from losing their epithelial features in order to maintain tissue integrity.; L'homéostasie des tissus épithéliaux est fondamentale à la survie et au maintien d'un organisme sain. Au cours de la morphogenèse des glandes mammaires, les cellules épithéliales communiquent avec leur stroma environnant afin d'orchestrer la formation d'un organe fonctionnel en passant par de multiples cycles régulés de prolifération, de transitions épithéliomésenchymateuse (TME) et mésenchymateuse-épithéliale, de migration et d'invasion. Dans les cellules cancéreuses, ces processus sont dérégulés. Il est donc important d'étudier comment les cellules mammaires normales conservent leur homéostasie au cours du développement pour appréhender les événements moléculaires induisant le cancer du sein. L'homéostasie de l'épithélium repose sur le contrôle de propriétés spécifiques : polarité apico-basale, cohésion cellulaire et formation de lumen. Notre protéine d'intérêt EFA6B, facteur d'échange d'Arf6, se trouve au cœur de ces caractéristiques structurelles, d'où mon intérêt à étudier son rôle dans les cellules épithéliales mammaires. Au cours de mes travaux de thèse, j'ai étudié l'impact de la perte d'EFA6B sur l'intégrité épithéliale. En utilisant des cellules épithéliales normales mammaires invalidées pour EFA6B par la technique de CRISPR/Cas9, j'ai démontré que la perte d'EFA6B dérégule fortement l'homéostasie épithéliale à différents niveaux. Premièrement, sa déplétion entraîne la formation d'invadopodes riches en intégrine ITGBI et en métalloprotéase MMP 14. Mes résultats indiquent que l'invasion des cellules EFA6B knock-out dépend de l'activation de Cdc42. Elle est soutenue par une contractilité accrue des cellules et la formation de structures branchées protrusives contrôlées par les voies de signalisation Cdc42/MRCK/P-MLC et Cdc42/NWASP/Arp2/3. Deuxièmement, nous avons montré que la perte d'EFA6B est associée à l'engagement des cellules EFA6B knock-out dans une TME, révélée par un échange de cadhérine et une augmentation de l'expression de facteurs de transcription mésenchymateux. Troisièmement, conformément au rôle d'EFA6B dans l'assemblage des jonctions serrées, sa déplétion empêche les cellules de se polariser et de former des acini avec un lumen central. Collectivement, nos données sont en accord avec des résultats précédemment publiés montrant une corrélation entre la perte d'EFA6B et le sous-type de cancer du sein invasif Claudin-low défini par une signature TME et une perte d'expression des protéines des jonctions serrées. J'ai aussi contribué à la caractérisation du rôle de l'a-actinine 1 comme effecteur d'EFA6A dans des cellules épithéliales normales (MDCK) et d'EFA6B dans une lignée cellulaire mammaire tumorigène (MCF 7). Je montre qu'EFA6B et l'a-actinine 1, en régulant la contractilité cellulaire apicale, coordonnent l'établissement de la polarité apico-basale, la formation des jonctions serrées et du lumen. L'ensemble de ces résultats démontre que la perte d'EFA6B stimule les propriétés invasives de cellules épithéliales normales et impacte leur microenvironnement (contractilité, dégradation de la matrice, altération du matrisome). Nous proposons que le gène PSD4 codant pour EFA6B est un gène suppresseur d'invasion qui contribue à préserver l'intégrité des tissus épithéliaux.

Local mechanical cues can affect crucial fate decisions of living cells. Transepithelial stress has been discussed in the context of epithelial monolayers, but the lack of appropriate experimental systems leads current studies to approximate it simply as an in‐plane stress. To evaluate possible contribution of force vectors acting in other directions, double epithelium in a 3D‐printed “GeminiChip” containing a sessile and a pendant channel is reconstituted. Intriguingly, the sessile epithelia is prone to apoptotic cell extrusion upon crowding, whereas the pendant counterpart favors live cell delamination. Transcriptome analyses show upregulation of RhoA, BMP2, and hypoxia‐signaling genes in the pendant epithelium, consistent with the onset of an epithelial–mesenchymal transition program. HepG2 microtumor spheroids also display differential spreading patterns in the sessile and pendant configuration. Using this multilayered GeminiChip, these results uncover a progressive yet critical role of perpendicular force vectors in collective cell behaviors and point at fundamental importance of these forces in the biology of cancer. NRF (Natl Research Foundation, S’pore) Accepted version

Purpose To report a case of corneal epithelial restoration after penetrating keratoplasty following multiple complications in repeated failed cultivated stem cell grafts. Methods This is a case report of a 62-year old patient who was treated for unilateral severe limbal stem cell deficiency after a chemical burn of the right eye. Results Two attempts to reconstruct the ocular surface using autologous cultivated limbal stem cell grafts (CLET) failed, and were complicated by perforations requiring two emergency penetrating keratoplasties. While the first donor cornea revascularised quickly, the corneal epithelium of the second remained transparent, avascular and stable until one year postoperatively. In vivo confocal microscopic examination confirmed presence of a healthy corneal epithelial phenotype. Conclusions Occurrence of serious adverse events are related to an inadequate epithelial homeostasis following CLET. The mechanisms of action of limbal stem cell transplantation are still poorly understood and the corneal epithelial integrity may be maintained without limbal input.

Intestinal epithelial cells (IECs) are exposed to the low-oxygen environment present in the lumen of the gut. These hypoxic conditions are on one hand fundamental for the survival of the commensal microbiota, and on the other hand, favor the formation of a selective semipermeable barrier allowing IECs to transport essential nutrients/water while keeping the sterile internal compartments separated from the lumen containing commensals. The hypoxia-inducible factor (HIF) complex, which allows cells to respond and adapt to fluctuations in oxygen levels, has been described as a key regulator in maintaining IEC barrier function by regulating their tight junction integrity. In this study, we sought to better evaluate the mechanisms by which low oxygen conditions impact the barrier function of human IECs. By profiling miRNA expression in IECs under hypoxia, we identified miRNA-320a as a novel barrier formation regulator. Using pharmacological inhibitors and short hairpin RNA-mediated silencing we could demonstrate that expression of this miRNA was HIF-dependent. Importantly, using over-expression and knock-down approaches of miRNA-320a we could confirm its direct role in the regulation of barrier functions in human IECs. These results reveal an important link between miRNA expression and barrier integrity, providing a novel insight into mechanisms of hypoxia-driven epithelial homeostasis.

The function of limbal stem/progenitor cells (LSCs) is critical to maintain corneal epithelial homeostasis. Many external insults and intrinsic defects can be deleterious to LSCs and their niche microenvironment, resulting in limbal stem cell dysfunction or deficiency (LSCD). Ocular comorbidities, frequent in eyes with LSCD, can exacerbate the dysfunction of residual LSCs, and limit the survival of transplanted LSCs. Clinical presentation and disease evolution vary among different etiologies of LSCD. New ocular imaging modalities and molecular markers are now available to standardize the diagnosis criteria and stage the severity of the disease. Medical therapies may be sufficient to reverse the disease if residual LSCs are present. A stepwise approach should be followed to optimize the ocular surface, eliminate the causative factors and treat comorbid conditions, before considering surgical interventions. Furthermore, surgical options are selected depending on the severity and laterality of the disease. The standardized diagnostic criteria to stage the disease is necessary to objectively evaluate and compare the efficacy of the emerging customized therapies.

Purpose of Review Epithelial cells line tissues and serve an important functional role in maintaining a barrier between tissue compartments and protection from the external environment. Tight Junctions and apical–basal polarity function to establish and maintain epithelial structures to prevent leakage between cells and define distinct subcellular domains to localize signaling pathways within cells that control growth, survival, and migration. Disruption of tight junctions and cell polarity is frequently observed in cancer.

A recent study shows that, upon stretching or wounding, epithelia display a fast proliferative response that allows for re-establishment of optimal cell density or sealing of the wound. This increased proliferation is induced by the stretch-activated channel Piezo1 and involves calcium-triggered ERK signalling.

Introduction: The female urogenital tract develops through a multistep process from the intermediate mesoderm (IM). Among several transcriptional regulators, Pax2 and Pax8 expression in the IM distinguishes all of the cells fated to become epithelia in the urogenital tract and are necessary to establish and maintain this phenotype. Fallopian tube epithelium mainly consists of two cell types, secretory and ciliated cells. In mice, Pax2 and Pax8 positive secretory cells are the oviduct epithelial progenitors and have the potential to self-renew as well as differentiate to ciliated cell progeny. Serous ovarian cancer (SOC) is the most common and the most lethal, and secretory cells are believed to be the progenitors of SOC. Patients with a predisposition for developing SOC were found to have tubal epithelial dysplastic lesions, such as serous tubal intraepithelial carcinoma (STIC). By generating double and single KO mouse modules of Pax2 and Pax8, we investigate their roles in maintaining the integrity of the oviductal cells and whether these proteins will provide new insight into epithelial homeostasis. Procedures: We used the Cre-loxP system to generate conditional KO of Pax2 and Pax8, using standard genetic and biochemical techniques to study the deletion of both proteins specifically in epithelium secretory cells. We used the OVGP1-Cre tamoxifen-inducible; also, some mice carried the combination with reporter mT/mG. Histology, immunohistochemistry, Western blot, and RNA meta-analysis data were collected and analyzed. Results: Mice carrying the single conditional KO of Pax2 f/f and Pax8f/f;OVGP1-CRE-ER or the double conditional KO of Pax2.flox-Pax8flox;OVGP1-CRE-ER appeared normal with no evidence of loss of function or other abnormalities. After tamoxifen administration and specific oviductal deletion of these proteins, the double Pax2 and Pax8 mutants showed oviduct phenotypes as early as 16 weeks. Such mice also failed to conceive even 8 weeks after tamoxifen administration. We observed progressive phenotypes at later times in the three combinations of protein deletion for up to one year after tamoxifen administration. Strikingly, cell lineage tracing revealed that surviving mutant cells could break through and migrate without losing their epithelial markers. These data demonstrate that Pax2 and Pax8 are needed for regenerating and maintaining the integrity of the fallopian tubes. Conclusions: Human ovarian cancer precursor lesions primarily consist of secretory cells. In mouse oviduct, secretory cells are the most frequently dividing cells of the oviductal epithelium. The mechanisms underlying epithelial homeostasis are still unknown. This in vivo genetic cell lineage tracing study showed that secretory cells give rise to ciliated cells that are altered upon Pax2 and Pax8 deletion. Using a conditional KO mouse model of Pax2 and Pax8 will allow us to identify future novel therapeutic targets and step further in the right direction to develop a novel of biomarkers for diagnostics and treatments. This abstract is also being presented as Poster B44. Citation Format: Abdulsalam Soofi, Yali Zahi, Kathleen Cho, Greg Dressler. Analyses of Pax2 and Pax8 in maintaining oviduct epithelial homeostasis and fertility [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research; 2019 Sep 13-16, 2019; Atlanta, GA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(13_Suppl):Abstract nr PR04.

The relationship between gut microbiota and the host is symbiotic and mutualistic. Gut microbiota has been shown to influence many aspects of host biology, including metabolism, development, and immunity. Due to the close proximity of the microbes to epithelial surfaces, this barrier represents the primary gateway for potential interactions. Alterations in the balance between gut microbiota and host are now clearly recognized as an influencing factor in the cause of a wide range of intestinal diseases. It is therefore important to gain a better understanding of the mechanisms regulating signals that gut microbiota provides to intestinal epithelial cells. In this context, it is expected that an important role is to be played by intestinal stem cells in their role in epithelial regeneration, homeostasis post-damage repair.

Skin tissues, in particular the epidermis, are severely affected by zinc deficiency. However, the zinc-mediated mechanisms that maintain the cells that form the epidermis have not been established. Here, we report that the zinc transporter ZIP10 is highly expressed in the outer root sheath of hair follicles and plays critical roles in epidermal development. We found that ZIP10 marked epidermal progenitor cell subsets and that ablating Zip10 caused significant epidermal hypoplasia accompanied by down-regulation of the transactivation of p63, a master regulator of epidermal progenitor cell proliferation and differentiation. Both ZIP10 and p63 are significantly increased during epidermal development, in which ZIP10-mediated zinc influx promotes p63 transactivation. Collectively, these results indicate that ZIP10 plays important roles in epidermal development via, at least in part, the ZIP10–zinc–p63 signaling axis, thereby highlighting the physiological significance of zinc regulation in the maintenance of skin epidermis.

The aim of this review is to describe the underlying mechanisms of corneal epithelial homeostasis in addition to illustrating the vital role of the limbal epithelial stem cells (LESCs) and the limbal niche in epithelial regeneration and wound healing.The shedded corneal epithelial cells are constantly replenished by the LESCs which give rise to epithelial cells that proliferate, differentiate, and migrate centripetally. While some recent studies have proposed that epithelial stem cells may also be present in the central cornea, the predominant location for the stem cells is the limbus. The limbal niche is the specialized microenvironment consisting of cells, extracellular matrix, and signaling molecules that are essential for the function of LESCs. Disturbances to limbal niche can result in LESC dysfunction; therefore, limbal stem cell deficiency should also be considered a limbal niche deficiency. Current and in-development therapeutic strategies are aimed at restoring the limbal niche, by medical and/or surgical treatments, administration of trophic factors, and cell based therapies.The corneal epithelium is constantly replenished by LESCs that are housed within the limbal niche. The limbal niche is the primary determinant of the LESC function and novel therapeutic approaches should be focused on regeneration of this microenvironment.

This week’s articles describe a cause of chronic inflammation in Gaucher disease, a method for improving the efficacy of T cell–mediated cancer immunotherapy, a type of oncogene amplification that enhances tumor heterogeneity, and a mechanism whereby mechanical stress maintains epithelial homeostasis.

Purpose: To report a case of hypoplastic trigeminal nerve associated with corneal epithelial disorders that were successfully treated with peptides derived from substance P and insulin-like growth factor-1 (IGF-1). Case Report: A 16-month-old boy was referred for treatment of a persistent corneal epithelial defect on his left eye. Magnetic resonance imaging revealed the apparent absence of the trigeminal nerve on the left side, and the patient was therefore diagnosed with neurotrophic keratopathy. Treatment with eye drops containing the tetrapeptides FGLM-NH2 and SSSR derived from the neuropeptide substance P and the growth factor IGF-1, respectively, resulted in resurfacing of the corneal epithelial defect. Discussion: The trigeminal nerve anomaly of the patient likely gave rise to neurotrophic keratopathy as a result of a deficiency of neural factors, emphasizing the importance of neural regulation in corneal epithelial homeostasis.

Islam and colleagues report that sildenafil suppresses inflammation-driven colorectal cancer in mice ([1][1]). Intestinal cyclic guanosine monophosphate (cGMP) signaling regulates epithelial homeostasis and has been implicated in the suppression of colitis and colon cancer. In their study, Islam and

Interleukin-22 (IL-22), an IL-10 family cytokine, is produced by various leukocytes. The receptor of IL-22, however, is preferentially detected on peripheral tissue epithelial cells. IL-22 functions as a unique messenger from immune system to tissue epithelial cells and to regulate homeostasis of epithelia. IL-22 is able to directly enhance antimicrobial defense mechanisms in epithelial cells and to facilitate epithelial barrier repair and wound healing process. It, therefore, possesses an irreplaceable role in host defense against certain pathogens that specifically invade epithelial cells. In addition, IL-22 can help to preserve the integrity and homeostasis of various epithelial organs during infection or inflammation. The importance of its tissue-protective function is manifested in many inflammatory situations such as inflammatory bowel diseases (IBD) and hepatitis. On the other hand, as a cytokine, IL-22 is capable of induction of proinflammatory responses, especially in synergy with other cytokines. Consequently, IL-22 contributes to pathogenesis of certain inflammatory diseases for example psoriasis.

Understanding the role of factors that regulate intestinal epithelial homeostasis and response to injury and regeneration is important. The current literature describes several different methodological approaches to obtain images of intestinal tissues for data validation. In this paper, we delineate a common protocol relating to the derivation and processing of mouse intestinal tissues. Proper fixation of intestinal tissues and Swiss-roll techniques that enhance intestinal epithelial morphology are discussed. Postresection processing and reorientation of embedded intestinal tissues are critical in obtaining paraffin-embedded blocks that display intact intestinal structural features after sectioning. The Swiss-rolling technique helps in histological assessment of the complete intestinal or colonic sections examined. An ability to differentiate intestinal structural features can be vital in quantitative measurements of intestinal inflammation and tumorigenesis along the entire length. Finally, paraffin-embedded sections are ideal for robust processing using both immunohistochemical and immunofluorescent detection methods. Nonfluorescent immunohistochemical sections provide a vibrant image of the tissue detailing different cellular structural features but do not provide flexibility for intracellular co-localization experiments. Multiple fluorescent channels can be appropriately utilized with immunofluorescent detection for co-localization experiments, lending support to mechanistic studies.