Transepithelial channels for leukocytes in the junctional epithelium

Area of Science:

• Oral biology
• Immunology
• Cell biology

Background:

• The junctional epithelium (JE) is a key defense site rich in polymorphonuclear leukocytes (PMNs).
• PMN migration through the JE is crucial for mucosal defense but lacks clear structural documentation.
• PMNs typically migrate outwards over epithelial surfaces in the intestinal and respiratory tracts.

Purpose of the Study:

• To investigate structural evidence of PMN transepithelial migration through the JE in gingival mucosa.
• To elucidate the pathway and mechanisms of PMN transmigration in the gingival sulcus.

Main Methods:

• Three-dimensional modeling of mouse gingiva using array tomography and field-emission scanning electron microscopy (FESEM).
• Analysis of serial sections at 800 nm thickness.
• Immunohistochemical examination of neutrophil marker CD47 expression.

Main Results:

• Array tomography revealed epithelial channels within the JE, running along its long axis.
• PMNs were predominantly found within these channels, not scattered throughout the JE.
• Channels extended from the JE base to the gingival sulcus bottom, with some interruptions.

Conclusions:

• The JE functions as an organ facilitating PMN transepithelial migration via epithelial channels.
• This migration pathway to the gingival sulcus mirrors mechanisms observed in other mucosal linings.
• Findings support a role for the JE in active immune surveillance and defense at the gingival margin.