RESUMO
In the expanding field of intestinal organoid research, various protocols for three- and two-dimensional organoid-derived cell cultures exist. Two-dimensional organoid-derived monolayers are used to overcome some limitations of three-dimensional organoid cultures. They are increasingly used also in infection research, to study physiological processes and tissue barrier functions, where easy experimental access of pathogens to the luminal and/or basolateral cell surface is required. This has resulted in an increasing number of publications reporting different protocols and media compositions for organoid manipulation, precluding direct comparisons of research outcomes in some cases. With this in mind, here we describe a protocol aimed at the harmonization of seeding conditions for three-dimensional intestinal organoids of four commonly used research species onto cell culture inserts, to create organoid-derived monolayers that form electrophysiologically tight epithelial barriers. We give an in-depth description of media compositions and culture conditions for creating these monolayers, enabling also the less experienced researchers to obtain reproducible results within a short period of time, and which should simplify the comparison of future studies between labs, but also encourage others to consider these systems as alternative cell culture models in their research. Graphic abstract: Schematic workflow of organoid-derived monolayer generation from intestinal spheroid cultures. ECM, extracellular matrix; ODM, organoid-derived monolayer.
RESUMO
BACKGROUND & AIMS: The protozoa Giardia duodenalis is a major cause of gastrointestinal illness worldwide, but underlying pathophysiological mechanisms remain obscure, partly due to the absence of adequate cellular models. We aimed at overcoming these limitations and recapitulating the authentic series of pathogenic events in the primary human duodenal tissue by using the human organoid system. METHODS: We established a compartmentalized cellular transwell system with electrophysiological and barrier properties akin to duodenal mucosa and dissected the events leading to G. duodenalis-induced barrier breakdown by functional analysis of transcriptional, electrophysiological, and tight junction components. RESULTS: Organoid-derived cell layers of different donors showed a time- and parasite load-dependent leak flux indicated by collapse of the epithelial barrier upon G. duodenalis infection. Gene set enrichment analysis suggested major expression changes, including gene sets contributing to ion transport and tight junction structure. Solute carrier family 12 member 2 and cystic fibrosis transmembrane conductance regulator-dependent chloride secretion was reduced early after infection, while changes in the tight junction composition, localization, and structural organization occurred later as revealed by immunofluorescence analysis and freeze fracture electron microscopy. Functionally, barrier loss was linked to the adenosine 3',5'-cyclic monophosphate (cAMP)/protein kinase A-cAMP response element-binding protein signaling pathway. CONCLUSIONS: Data suggest a previously unknown sequence of events culminating in intestinal barrier dysfunction upon G. duodenalis infection during which alterations of cellular ion transport were followed by breakdown of the tight junctional complex and loss of epithelial integrity, events involving a cAMP/protein kinase A-cAMP response element-binding protein mechanism. These findings and the newly established organoid-derived model to study G. duodenalis infection may help to explore new options for intervening with disease and infection, in particular relevant for chronic cases of giardiasis.
Assuntos
Giardíase/fisiopatologia , Mucosa Intestinal/fisiopatologia , Transporte de Íons , Transdução de Sinais , Junções Íntimas/fisiologia , Apoptose , Células CACO-2 , Cloretos/metabolismo , AMP Cíclico/metabolismo , Proteínas Quinases Dependentes de AMP Cíclico/metabolismo , Regulador de Condutância Transmembrana em Fibrose Cística/genética , Duodeno , Impedância Elétrica , Giardia lamblia , Giardíase/genética , Giardíase/imunologia , Humanos , Interleucina-1/genética , Transporte de Íons/genética , NF-kappa B/genética , Organoides , Carga Parasitária , Membro 2 da Família 12 de Carreador de Soluto/genética , Junções Íntimas/genética , Junções Íntimas/patologia , Junções Íntimas/ultraestrutura , Transcriptoma , Fator de Necrose Tumoral alfa/genéticaRESUMO
BACKGROUND: Epithelial barrier defects are well known in coeliac disease, but the mechanisms are only poorly defined. It is unclear, whether barrier disturbance reflects upregulated epithelial transcytosis or paracellular leakage. OBJECTIVE: To characterise the molecular structure and function of the epithelial tight junction (TJ) and mechanisms of its dysregulation. METHODS: Molecular analysis of proteins involved in TJ assembly and their regulation was performed by western blotting and confocal microscopy correlated to electrophysiology. RESULTS: A complex alteration of the composition of epithelial TJ proteins (with more pore-forming claudins like claudin-2 and a reduction in tightening claudins like claudin-3, -5 and -7) was found for protein expression and subcellular localisation, responsible for an increase in paracellular biotin-NHS uptake. In contrast, epithelial apoptosis was only moderately elevated (accounting for a minor portion of barrier defects) and epithelial gross lesions--for example, at cell extrusion zones, were absent. This TJ alteration was linked to an altered localisation/expression of proteins regulating TJ assembly, the polarity complex protein Par-3 and the serine-/threonine phosphatase PP-1. CONCLUSIONS: Changes in cell polarity proteins Par-3 and PP-1 are associated with altered expression and assembly of TJ proteins claudin-2, -3, -5 and -7 and ZO-1, causing paracellular leakage in active coeliac disease.
Assuntos
Doença Celíaca/metabolismo , Proteínas de Ciclo Celular/metabolismo , Polaridade Celular , Mucosa Intestinal/metabolismo , Proteínas de Membrana/metabolismo , Proteína Fosfatase 1/metabolismo , Junções Íntimas/metabolismo , Proteínas Adaptadoras de Transdução de Sinal , Apoptose , Biotinilação , Western Blotting , Estudos de Casos e Controles , Doença Celíaca/patologia , Doença Celíaca/fisiopatologia , Proteínas de Ciclo Celular/fisiologia , Claudinas/metabolismo , Humanos , Mucosa Intestinal/química , Proteínas de Membrana/fisiologia , Microscopia Confocal , Fosfoproteínas/metabolismo , Reação em Cadeia da Polimerase , Proteína Fosfatase 1/fisiologia , Junções Íntimas/química , Proteína da Zônula de Oclusão-1RESUMO
The intestinal permeability of undegraded α9-gliadin peptide 31-49 (p31-49) and 33-mer gliadin peptides is increased in active celiac disease. Two distinct transport pathways have been proposed: paracellular leakage through epithelial tight junctions and protected transcellular transport. To analyze the relative contribution of these pathways, we compared mucosa-to-serosa permeability of small and large permeability markers [ionic conductance (G), mannitol, 182 Da; horseradish peroxidase, 40 kDa] and gliadin peptides [33-mer (p56-88, 3900 Da), 19-mer (p31-49, 2245 Da; and p202-220, 2127 Da), and 12-mer (p57-68, 1453 Da)] in duodenal biopsy specimens mounted in Ussing chambers. The permeability of intact peptides was much higher for p31-49 or 33-mer than for horseradish peroxidase, p202-220, and p57-68. A positive correlation was observed between G, an index of paracellular diffusion of ions, and mannitol permeability. The absence of correlation between G and permeability to intact 33-mer or p31-49 did not favor paracellular diffusion of the peptides. Immunofluorescence studies indicated that 33-mer enters the early endosome antigen 1-positive compartment but escapes the lysosomal-associated protein 2-positive compartment. The results underline that mannitol and ionic conductance G cannot be considered markers of permeability to gliadin peptides. In active celiac disease, increases in transcellular permeability to intact gliadin peptides might be considered in treatment strategies aimed at controlling epithelial permeability to gluten.
Assuntos
Doença Celíaca/metabolismo , Duodeno/metabolismo , Gliadina/farmacocinética , Fragmentos de Peptídeos/farmacocinética , Transporte Biológico , Peroxidase do Rábano Silvestre/farmacocinética , Humanos , Mucosa Intestinal/metabolismo , Manitol/farmacocinética , Permeabilidade , Membrana Serosa/metabolismo , Junções Íntimas/metabolismoRESUMO
BACKGROUND & AIMS: The epithelial sodium channel (ENaC) mediates electrogenic sodium absorption in distal colon. In patients with inflammatory bowel disease (IBD), ENaC induction is impaired, mainly through transcriptional suppression by proinflammatory cytokines such as tumor necrosis factor (TNF)-alpha. Glucocorticoid therapy rapidly increases sodium absorption; we investigated the molecular mechanisms underlying the interaction among TNF-alpha, glucocorticoids, and ENaC induction. METHODS: ENaC-mediated sodium transport in glucocorticoid receptor (GR)-expressing HT-29/B6 cells and rat distal colon, under the influence of the synthetic glucocorticoid dexamethasone and TNF-alpha, was quantified in Ussing chambers. ENaC messenger RNA (mRNA) levels were monitored by real-time polymerase chain reaction. GR transactivation and expression were investigated by gene reporter, immunoblot, and confocal immunofluorescence microscopy analyses. The GR mRNA half-life was determined. Signaling pathways were characterized using mitogen-activated protein kinase inhibitors. RESULTS: Dexamethasone not only prevented TNF-alpha-mediated ENaC suppression but caused synergistic induction of ENaC-dependent sodium absorption in HT-29/B6-GR cells and rat distal colon. This synergy resulted from TNF-alpha-mediated increases in GR protein levels because of GR mRNA stabilization and subsequent GR transactivation by dexamethasone. As a consequence, transcription of the ENaC beta- and gamma-subunits was up-regulated, increasing ENaC-dependent sodium absorption. p38 Mitogen-activated protein kinase is required for this synergistic effect: p38 inhibition blocked the increase in GR protein expression and ENaC-dependent sodium absorption. CONCLUSIONS: TNF-alpha and dexamethasone induce ENaC, explaining the rapid and intense proabsorptive effect of glucocorticoid therapies.
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Dexametasona/farmacologia , Canais Epiteliais de Sódio/metabolismo , Proteína Relacionada a TNFR Induzida por Glucocorticoide/farmacologia , Mucosa Intestinal/efeitos dos fármacos , Fator de Necrose Tumoral alfa/farmacologia , Animais , Colo/citologia , Colo/efeitos dos fármacos , Colo/metabolismo , Sinergismo Farmacológico , Canais Epiteliais de Sódio/genética , Expressão Gênica/efeitos dos fármacos , Células HT29 , Humanos , Absorção Intestinal/efeitos dos fármacos , Absorção Intestinal/fisiologia , Mucosa Intestinal/citologia , Mucosa Intestinal/metabolismo , Masculino , RNA Mensageiro/metabolismo , Ratos , Ratos Wistar , Receptores de Glucocorticoides/genética , Receptores de Glucocorticoides/metabolismo , Sódio/metabolismo , Regulação para Cima/efeitos dos fármacos , Proteínas Quinases p38 Ativadas por Mitógeno/metabolismoRESUMO
BACKGROUND: Giardia lamblia causes infection of the small intestine, which leads to malabsorption and chronic diarrhoea. AIM: To characterise the inherent pathomechanisms of G lamblia infection. METHODS: Duodenal biopsy specimens from 13 patients with chronic giardiasis and from controls were obtained endoscopically. Short-circuit current (I(SC)) and mannitol fluxes were measured in miniaturised Ussing chambers. Epithelial and subepithelial resistances were determined by impedance spectroscopy. Mucosal morphometry was performed and tight junction proteins were characterised by immunoblotting. Apoptotic ratio was determined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labelling staining. RESULTS: In giardiasis, mucosal surface area per unit serosa area was decreased to 75% (3%) of control, as a result of which epithelial resistance should increase. Instead, epithelial resistance of giardiasis biopsy specimens was decreased (19 (2) vs 25 (2) Omega cm(2); p<0.05) whereas mannitol flux was not significantly altered (140 (27) vs 105 (16) nmol/h/cm(2)). As structural correlate, reduced claudin 1 expression and increased epithelial apoptosis were detected. Furthermore, basal I(SC) increased from 191 (20) in control to 261 (12) microA/h/cm(2) in giardiasis. The bumetanide-sensitive portion of I(SC) in giardiasis was also increased (51 (5) vs 20 (9) microA/h/cm(2) in control; p<0.05). Finally, phlorizin-sensitive Na(+)-glucose symport was reduced in patients with giardiasis (121 (9) vs 83 (14) microA/h/cm(2)). CONCLUSIONS: G lamblia infection causes epithelial barrier dysfunction owing to down regulation of the tight junction protein claudin 1 and increased epithelial apoptoses. Na(+)-dependent d-glucose absorption is impaired and active electrogenic anion secretion is activated. Thus, the mechanisms of diarrhoea in human chronic giardiasis comprise leak flux, malabsorptive and secretory components.
Assuntos
Duodeno/fisiopatologia , Giardia lamblia , Giardíase/fisiopatologia , Enteropatias Parasitárias/fisiopatologia , Mucosa Intestinal/fisiopatologia , Adulto , Idoso , Animais , Apoptose , Transporte Biológico Ativo , Biópsia , Doença Crônica , Claudina-1 , Duodeno/patologia , Giardíase/patologia , Humanos , Absorção Intestinal , Enteropatias Parasitárias/patologia , Mucosa Intestinal/patologia , Síndromes de Malabsorção/parasitologia , Síndromes de Malabsorção/patologia , Síndromes de Malabsorção/fisiopatologia , Proteínas de Membrana/metabolismo , Pessoa de Meia-Idade , Permeabilidade , Junções Íntimas/metabolismoRESUMO
Epithelial barrier function is determined by trans- and paracellular permeabilities, the latter of which is mainly influenced by tight junctions (TJs) and apoptotic leaks within the epithelium. The present article aims to present experimental evidence for a functional role of epithelial apoptoses by means of cell culture models as well as in tissues from patients with inflammatory bowel disease. It is shown that epithelial apoptoses are sites of elevated conductance within the intestinal epithelium and that proinflammatory cytokines like TNF-alpha upregulate both the apoptotic rate and single apoptotic conductivity, making cytokine-induced apoptosis functionally far more relevant than is spontaneous apoptosis. In ulcerative colitis and Crohn's disease (CD), but not in collagenous colitis, apoptotic rates are increased to about 5%, in mild-to-moderately inflamed colon specimens, where as the control apoptotic rate is about 2%. Thus, epithelial apoptoses lead to a loss of ions and water into the intestinal lumen, causing leak flux diarrhea and enabling small antigens of <4,000 Da in the intestinal lumen to enter the intestinal mucosa, thereby perpetuating inflammatory responses. In addition to TNF-alpha, interleukin (IL)-13 is an important inductor of epithelial apoptosis in Th2 immune responses. Therapeutically,TNF-alpha-antibodies (infliximab) can restore barrier function in Crohn's disease by downregulating epithelial apoptoses, while epithelial TJs are unaffected.
Assuntos
Apoptose/fisiologia , Colite Ulcerativa/fisiopatologia , Mucosa Intestinal/fisiopatologia , Linhagem Celular , Colite Ulcerativa/patologia , Colo/fisiopatologia , Condutividade Elétrica , Impedância Elétrica , Humanos , Mucosa Intestinal/patologia , Fator de Necrose Tumoral alfa/fisiologiaRESUMO
Intestinal antigen uptake is enhanced in inflammatory bowel disease. We analyzed transcellular transport routes of antigens in different compartments of normal enterocytes and atypical intestinal epithelial cells called "rapid antigen uptake into the cytosol enterocytes" (RACE cells). These cells constitute a recently described population of enterocyte-derived cells, which are increased in inflammatory bowel disease. Mucosa of freshly resected specimens were incubated with the antigens ovalbumin or horseradish peroxidase. Ultrastructural labeling patterns of differentiation-dependent proteins, the brush-border enzyme sucrase-isomaltase and the cytoskeleton proteins villin and actin, were determined in enterocytes. Apoptosis was investigated biochemically and ultrastructurally by cleavage of caspase-3. Both antigens were transported to late endosomes and to trans-Golgi vesicles of enterocytes in inflammatory bowel disease and control specimens. Quantitative evaluation revealed a significantly increased transepithelial antigen transport in both compartments of RACE relative to normal enterocytes. Labeling densities for sucrase-isomaltase, villin, and actin were decreased in RACE relative to normal enterocytes. Caspase-3 was not increased in RACE cells relative to controls. RACE cells are characterized by increased antigen transport to late endosomes and the trans-Golgi network, a disassembled cytoskeleton and lower concentrations of proteins that are markers of cell differentiation.