Functional Assessment of Mouse Gingival Epithelial Barrier Using Fluorescent Tracers

The gingival epithelial barrier serves as a critical frontline defense in oral immunity and homeostasis. An intact epithelial barrier effectively prevents the penetration of harmful substances from the oral environment, whereas its disruption is closely associated with the pathogenesis of conditions such as periodontitis and oral lichen planus. Here, we established a topical application-based method to assess the integrity of the gingival epithelial barrier in mice. First, a mixture of fluorescently labeled dextrans with different molecular weights (40 or 70 kDa) in a 2% sodium carboxymethylcellulose was applied topically to the labial gingival surface of the molar region. After a 30 min incubation period, the maxilla was dissected and fixed in a customized holder for immediate imaging using a single-photon microscopy system. This approach enables visualization and quantification of tracers of different sizes across the epithelial layers, providing a functional readout of gingival epithelial barrier integrity applicable to studies of oral inflammation, wound healing, and disease modeling.