Detection of MUC1+/MUC2 and MUC5AC- Membrane-Associated Mucins in the Intraepithelial Surface Mucous Cells of the Developing Rabbit Esophagus.

Introduction: Mucins are polydisperse molecules created to perform a variety of functions at the mucosal surface of the adult gastrointestinal tract. Two main groups of mucins could be identified: the membrane-associated mucins (MUC1, MUC4, MUC13, and MUC16), those bound to the apical plasma membrane of epithelial cells, and the secreted mucins (MUC2, MUC5AC, MUC5B, and MUC6), those secreted from the goblet cells. Little is known about the types and distribution patterns of mucins in prenatal life.

Methods: We detected mucin-secreting cells in the developing rabbit esophagus though these cells are absent in the adult one. In order to identify the content and possible functions of these cells, we investigated the histochemical and immunohistochemical characteristics of their mucins.

Results: Starting at 16th day of pregnancy, periodic acid Schiff (PAS), alcian blue (AB) pH (2.5), and PAS-AB combination intensely stained the mucous content, demonstrating both acidic and neutral mucopolysaccharides. Some blebs could be recognized on the free surface of the esophageal epithelium. Also, the mucous cells and some basal cells strongly immunoreacted with MUC1, but not MUC2, nor MUC5AC antibodies.

Conclusion: Collectively, these data suggest that surface mucous cells are modified epithelial cells, not goblet cells, and may originate from the basal layer of the epithelial cells. A possible regulatory role for these MUC1-positive mucins in esophageal epithelial and mesenchymal cell differentiation and late organogenesis is suggested. However, future functional studies are recommended.