Goblet Cells and Mucus Composition in Jejunum and Ileum Containing Peyer's Patches and in Colon: A Study in Pigs

The intestinal mucus layer is a dynamic protective barrier that maintains gut homeostasis, supports immune defense, and regulates host-microbiota interactions. Rodent models have yielded valuable insights, but their intestinal structure and physiology differ from those of humans and pigs. By contrast, the omnivorous pig shares closer anatomical and immunological features with humans, making it a relevant large-animal model in translational studies. In this study, we established a histological workflow for porcine intestine by combining Carnoy's fixation with Alcian Blue-Periodic Acid-Schiff and Mucicarmine staining. This enabled accurate visualization and quantification of goblet-cell density and mucus thickness across intestinal segments, with a particular focus on Peyer's patches-key sites of immune surveillance. Both stains produced consistent results. We observed a clear proximal-to-distal gradient, from jejunum to colon, in mucus thickness: the colon displayed the thickest layer (~100 μm), whereas the follicle-associated epithelium over Peyer's patches in the jejunum and ileum showed a markedly thinner layer (<12 μm) and fewer goblet cells. Immunofluorescence further revealed strong cytokeratin-18 expression in goblet cells, delineating their morphology and polarity. These findings demonstrate region-specific differences in mucus architecture and goblet-cell distribution that likely reflect specialized immune functions, advancing our understanding of the intestinal barrier and informing future strategies to support gut health and immunity.