Claudins: Beyond Tight Junctions in Human IBD and Murine Models

Area of Science:

• Molecular Biology
• Gastroenterology
• Immunology

Background:

• Claudins are essential transmembrane proteins forming tight junctions, vital for epithelial barrier function.
• Altered claudin expression is observed in inflammatory bowel disease (IBD), suggesting their potential as therapeutic targets.

Purpose of the Study:

• To investigate claudin expression in human IBD and two distinct animal models of colitis.
• To evaluate specific claudins (claudin-1, -2, -3, -4, -8) in epithelial and non-epithelial cells.

Main Methods:

• Immunohistochemistry and quantitative polymerase chain reaction (qPCR) were used to assess claudin expression.
• Western blot and flow cytometry confirmed claudin expression in human mononuclear cells.
• Analysis included human samples and two rodent models: dextran sulfate sodium-induced colitis and adoptive transfer colitis.

Main Results:

• Claudins were expressed not only by epithelial cells but also by cells of mesodermal origin, including in the cytoplasm and nuclei.
• Claudin expression patterns varied between species and murine strains in both healthy and inflamed colons.
• Significant alterations in claudin expression were observed in epithelial and inflammatory cells in IBD and animal models.

Conclusions:

• Claudins exhibit broader expression than previously thought, extending to mesodermal cells.
• Interpreting changes in claudin mRNA levels requires considering overall tissue cellular composition.
• The studied animal models are suitable for investigating claudins as therapeutic targets in IBD, acknowledging species-specific differences.