Fungal Dysbiosis Aggravates Pouchitis in a Rat Model of Ileal Pouch Anal Anastomosis

Cellular and molecular mechanisms in the pathogenesis of pouchitis: more than just the microbiota

Pouchitis, defined as inflammation of the ileal pouch, is the most common complication following restorative proctocolectomy for refractory ulcerative colitis. Antibiotics remain the first line of therapy for pouchitis, but the majority of patients develop subsequent episodes and some are refractory to antibiotic therapy. This highlights the need for more effective treatment options and points to a more complex pathophysiology beyond the role of th pouch microbiome, similar to what is seen in inflammatory bowel disease. In this review, we outline the putative mechanisms of pouchitis, including genetic predisposition, microbiome alterations, dysfunction of the intestinal barrier and the immune system and review the available animal models of pouchitis. In addition, we introduce the concept of pouchitis as a possible transmural disease and discuss the potential role of non-immune cells, including stromal cells, in perpetuating inflammation and intestinal barrier dysfunction. We discuss future directions, implications for novel therapies and propose novel multicellular disease models that can better capture the complexity of pouchitis pathogenesis.

Tryptophan Metabolites Improve Intestinal Mucosal Barrier via the Aryl Hydrocarbon Receptor-Interleukin-22 Pathway in Murine Dextran Sulfate Sodium-Induced Pouchitis

BACKGROUND

Pouchitis is the most common complication after IPAA for ulcerative colitis. The protective effect of tryptophan metabolites on the mucosal barrier may be effective for treating pouchitis. The role of tryptophan metabolites on pouchitis remained unclear.

OBJECTIVE

We aimed to establish a murine model of dextran sulfate sodium-induced pouchitis to examine the roles of tryptophan metabolites in its pathogenesis.

DESIGN

This is a study that combines clinical patient data and animal research. A total of 22 patients were enrolled: 5 patients with familial adenomatous polyposis after IPAA, 8 patients with ulcerative colitis after IPAA with pouchitis, and 9 patients with ulcerative colitis after IPAA with normal pouch. The demographic data and fecal samples of patients were collected. Male C57BL/6 mice were purchased from a licensed breeder and underwent IPAA to establish a murine model of the pouch. The blood, feces, and tissues of mice were collected.

SETTINGS

This study was performed in an academic medical center in China.

INTERVENTIONS

The demographic data of patients were observationally collected. The mice that underwent IPAA were divided into a control group that received a chow diet and 5 study groups: 1) dextran sulfate sodium, 2) 6-formylindolo[3,2-b] carbazole + dextran sulfate sodium, 3) high tryptophan diet + dextran sulfate sodium, 4) CH-223191 + dextran sulfate sodium, and 5) indole-3-carboxaldehyde + dextran sulfate sodium. Animals were euthanized after receiving dextran sulfate sodium for 7 days.

MAIN OUTCOME MEASURES

Fecal tryptophan metabolite level and microbiome composition, the severity of pouchitis, intestinal mucosal barrier function, and activation of the aryl hydrocarbon receptor-interleukin 22 pathway were assessed.

RESULTS

Patients with pouchitis had lower fecal microbial diversity and indole-3-acetic acid levels. In the murine pouchitis model, high tryptophan diet increased fecal levels of 3-indoleglyoxylic acid, indole-3-aldehyde, and indole. A high tryptophan diet and intraperitoneal aryl hydrocarbon receptor ligand 6-formylindolo[3,2-b] carbazole injection alleviated pouchitis. Tryptophan metabolites improved pouch mucosal barriers. Aryl hydrocarbon receptor inhibitors exacerbated experimental pouchitis and disrupted the mucosal barrier; however, the aryl hydrocarbon receptor ligand indole-3-carboxaldehyde reversed this effect.

LIMITATIONS

This study was limited by a small human sample size and lacked an aryl hydrocarbon receptor knockout mouse model.

CONCLUSIONS

A high tryptophan diet and aryl hydrocarbon receptor ligand alleviated dextran sulfate sodium-induced pouchitis in a murine IPAA model, which might be achieved through regulating epithelial tight junctions and promoting goblet cell differentiation, as well as maintaining the integrity and function of the mucosal barrier. This study provides a rationale for the clinical application of aryl hydrocarbon receptor ligands in the treatment of pouchitis. See Video Abstract .

LOS METABOLITOS DEL TRIPTFANO MEJORAN LA BARRERA DE LA MUCOSA INTESTINAL A TRAVS DE LA VA DEL RECEPTOR DE HIDROCARBUROS ARILOINTERLEUCINA EN LA RESERVORITIS INDUCIDA POR SULFATO DE SODIO Y DEXTRANO EN MODELO MURINO

ANTECEDENTES:La reservoritis es la complicación más frecuente después de la anastomosis del reservorio ileal con el ano en la colitis ulcerosa. El efecto protector de los metabolitos del triptófano sobre la barrera mucosa puede ser un método eficaz para tratar la reservoritis. El papel de los metabolitos del triptófano en la reservoritis sigue sin estar claro.OBJETIVO:Nuestro objetivo era establecer un modelo murino de reservoritis inducida por sulfato de dextrano sódico para examinar el papel de los metabolitos del triptófano en su patogenia.DISEÑO:Este es un estudio que combina datos clínicos de pacientes e investigación animal. Se inscribieron un total de 22 pacientes: 5 con poliposis adenomatosa familiar después de un reservorio ileal, ocho pacientes con colitis ulcerosa después de un reservorio ileal que desarrollaron reservoritis y 9 pacientes con colitis ulcerosa después de un reservorio ileal que no presentaron reservoritis. Se recogieron los datos demográficos y las muestras fecales de los pacientes. Se adquirieron ratones macho C57BL/6 de un criador autorizado y se les realizó un reservorio ileal para establecer un modelo murino del reservorio. Se recogieron sangre, heces y tejidos de los ratones.CONFIGURACIÓN:Este estudio se realizó en un centro médico académico en China.INTERVENCIONES:Los datos demográficos de los pacientes se recogieron de forma observacional. Los ratones sometidos a un reservorio ileal se dividieron en seis grupos: grupo de control con dieta normal, sulfato de dextrano sódico, 6-formilindolo[3,2-b] carbazol + sulfato de dextrano sódico, dieta rica en triptófano + sulfato de dextrano sódico, CH-223191 + sulfato de dextrano sódico, indol-3-carboxaldehído + sulfato de dextrano sódico. Los animales fueron sacrificados después de la administración de sulfato de dextrano sódico durante 7 días.PRINCIPALES MEDIDAS DE RESULTADOS:Se evaluaron los niveles de metabolitos de triptófano y la composición del microbioma fecal, la gravedad de la reservoritis, la función de barrera de la mucosa intestinal y la activación de la vía del receptor de hidrocarburos de arilo-interleucina 22.RESULTADOS:Los pacientes con reservoritis tenían una menor diversidad microbiana fecal y niveles de ácido indol-3-acético. En el modelo de reservoritis murino, la dieta rica en triptófano aumentó los niveles fecales de ácido 3-indolglioxílico, indol-3-aldehído e indol. Una dieta rica en triptófano y una inyección intraperitoneal del ligando del receptor de hidrocarburos de arilo 6-formilindolo[3,2-b] carbazol aliviaron la reservoritis. Los metabolitos de triptófano mejoraron las barreras de la mucosa de la reservoritis. Los inhibidores del receptor de hidrocarburos de arilo exacerbaron la reservoritis experimental y alteraron la barrera mucosa; sin embargo, el ligando del receptor de hidrocarburos de arilo indol-3-carboxaldehído revirtió este efecto.LIMITACIONES:Este estudio estuvo limitado por el pequeño tamaño de la muestra humana y la falta de un modelo de ratón con deficiencia del receptor de hidrocarburos arílicos.CONCLUSIONES:Una dieta rica en triptófano y un ligando del receptor de hidrocarburos arílicos aliviaron la reservoritis inducida por sulfato de dextrano sódico en un modelo murino de anastomosis de reservorio ileo-anal, lo que podría deberse a la regulación de las uniones estrechas epiteliales y la promoción de la diferenciación de las células caliciformes, así como al mantenimiento de la integridad y la función de la barrera mucosa. Este estudio proporciona una justificación para la aplicación clínica de los ligandos del receptor de hidrocarburos arílicos en el tratamiento de la reservoritis. (Traducción-Dr. Felipe Bellolio ).

Fecal Filobasidium Is Associated with Clinical Remission and Endoscopic Response following Fecal Microbiota Transplantation in Mild-to-Moderate Ulcerative Colitis

Fecal microbiota transplantation (FMT) has the potential to restore (bacterial and fungal) microbial imbalance in ulcerative colitis (UC) patients and contribute to disease remission. Here, we aimed to identify fecal fungal species associated with the induction of clinical remission and endoscopic response to FMT for patients with mild-to-moderate ulcerative colitis. We analyzed the internal transcribed spacer 1 (ITS1)-based mycobiota composition in fecal samples from patients (n = 31) and donors (n = 7) that participated previously in a double-blinded randomized control trial evaluating the efficacy of two infusions of donor FMT compared with autologous FMT. The abundance of the yeast genus Filobasidium in fecal material used for transplantation was shown to correlate with clinical remission following FMT, irrespective of its presence in the material of donor or autologous fecal microbiota transfer. The amplified sequence variants within the genus Filobasidium most closely resembled Filobasidium magnum. Monocyte-derived macrophages and HT29 epithelial cells were stimulated with fungal species. Especially Filobasidium floriforme elicited an IL10 response in monocyte-derived macrophages, along with secretion of other cytokines following stimulation with other Filobasidium species. No effect of Filobasidium spp. was seen on epithelial wound healing in scratch assays. In conclusion, the enriched presence of Filobasidium spp. in donor feces is associated with the positive response to FMT for patients with UC and hence it may serve as a predictive fungal biomarker for successful FMT.

The role of mycobiota-genotype association in inflammatory bowel diseases: a narrative review

Inflammatory bowel disease (IBD) is a chronic inflammatory disease affecting various parts of the gastrointestinal tract. A majority of the current evidence points out the involvement of intestinal dysbiosis in the IBD pathogenesis. Recently, the association of intestinal fungal composition With IBD susceptibility and severity has been reported. These studies suggested gene polymorphisms in the front line of host defense against intestinal microorganisms are considered to play a role in IBD pathogenesis. The studies have also detected increased susceptibility to fungal infections in patients carrying IBD-related mutations. Therefore, a literature search was conducted in related databases to review articles addressing the mycobiota-genotype association in IBD.