title: Loss of Smad5 leads to the disassembly of the apical junctional complex and increased susceptibility to experimental colitis.
abstract: The regulation of intestinal epithelial cell adhesion and migratory properties is often compromised in inflammatory bowel disease (IBD). Despite an increasing interest in bone morphogenetic protein (Bmp) signaling in gut pathologies, little is known of the specific roles played by individual Smads in intestinal epithelial functions. In the present study, we generated a mouse model with deletion of Smad5 transcriptional effector of the Bmp signaling pathway exclusively in the intestinal epithelium. Proliferation, migration, and apical junctional complex (AJC) protein expression were analyzed by immunofluorescence and Western blot. Human intestinal biopsies from control and IBD patients were analyzed for SMAD5 gene transcript expression by quantitative PCR (qPCR). Smad5(ΔIEC) and control mice were subjected to dextran sulfate sodium (DSS)-induced experimental colitis, and their clinical and histological symptoms were assessed. Loss of Smad5 led to intestinal epithelial hypermigration and deregulation of the expression of claudin-1 and claudin-2. E-cadherin was found to be equally expressed but displaced from the AJC to the cytoplasm in Smad5(ΔIEC) mice. Analysis of SMAD5 gene expression in human IBD patient samples revealed a significant downregulation of the gene transcript in Crohn's disease and ulcerative colitis samples. Smad5(ΔIEC) mice exposed to experimental DSS colitis were significantly more susceptible to the disease and had impaired wound healing during the recovery phase. Our results support that Smad5 is partly responsible for mediating Bmp signals in intestinal epithelial cells. In addition, deficiency in epithelial Smad5 leads to the deregulation of cell migration by disassembling the AJC with increasing susceptibility to experimental colitis and impairment in wound healing.
authors.affiliation: Faculté de Médecine et des Sciences de la Santé, Département d’Anatomie et Biologie Cellulaire, Université de Sherbrooke, Quebec, Canada.
authors.forename: Joannie M
authors.initials: JM
authors.lastname: Allaire
authors.forename: Mathieu
authors.initials: M
authors.lastname: Darsigny
authors.forename: Sébastien S
authors.initials: SS
authors.lastname: Marcoux
authors.forename: Sébastien A B
authors.initials: SA
authors.lastname: Roy
authors.forename: Jean-Francois
authors.initials: JF
authors.lastname: Schmouth
authors.forename: Lieve
authors.initials: L
authors.lastname: Umans
authors.forename: An
authors.initials: A
authors.lastname: Zwijsen
authors.forename: François
authors.initials: F
authors.lastname: Boudreau
authors.forename: Nathalie
authors.initials: N
authors.lastname: Perreault
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002465:Cell Movement / Q000235:genetics; D003092:Colitis / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D004198:Disease Susceptibility / Q000378:metabolism* / Q000473:pathology; D004847:Epithelial Cells / Q000378:metabolism / Q000473:pathology; D005455:Fluorescent Antibody Technique; D006801:Humans; D007365:Intercellular Junctions / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000502:physiology; D051902:Smad5 Protein / Q000235:genetics / Q000378:metabolism*
chemical_list: D051902:Smad5 Protein