The oral mucosa: Epithelial professional phagocytes, lymphatics, telocytes, and false telocytes

The oral mucosa protects the underlying tissue from mechanical damage as well as from the entry of exogenous particles and microorganisms. Telocytes (TCs) are disputed stromal cells featuring peculiarly long and thin processes with uneven calibre known as telopodes, which play a number of roles within the interstitia. The present study aimed to test the key markers recommended for discriminating between TCs and false TCs in samples of normal oral mucosa. Archived paraffin-embedded oral mucosa samples were tested by means of immunohistochemistry with the following markers: CD34, D2-40, CD31 and CD68. The epithelial expression of CD68, D2-40 and CD34 was detected. Two subsets of CD34-expressing stromal cells were identified, large cells with telopodial processes, presumably of the hematopoietic lineage, and spindle-shaped TC-like cells. Macrophages and TC-like cells within the lamina propria expressed CD68. The lymphatic endothelia were found to express CD31 and D2-40, but not CD34. Sprouting lymphangiogenesis was demonstrated by the lymphatic endothelial tip cells, which were projecting thin processes within the connective stroma. The epithelial expression of CD68 suggests the professional phagocytic potential of the oral epithelium. Regarding the TCs and TC-like cells in the oral mucosa they could not be accurately distinguished from other possible cell types, neither on morphological basis (evidence of telopodes) nor by use of panels of markers which include CD34.