Expression of p75NGFR,a Proliferative and Basal Cell Marker,in the Buccal Mucosa Epithelium during Re-epithelialization

We investigated the expression of p75^NGFR, a proliferative and basal cell marker, in the mouse buccal mucosa epithelium during wound healing in order to elucidate the role of epithelial stem cells. Epithelial defects were generated in the epithelium of the buccal mucosa of 6-week-old mice using CO₂ laser irradiation. BrdU was immediately administered to mice following laser irradiation. They were then sacrificed after 1, 3, 7, and 14 days. Paraffin sections were prepared and the irradiated areas were analyzed using immunohistochemistry with anti-p75^NGFR, BrdU, PCNA, and CK14 antibodies. During re-epithelialization, PCNA (–)/p75^NGFR (+) cells extended to the wound, which then closed, whereas PCNA (+)/p75^NGFR (+) cells were not observed at the edge of the wound. In addition, p75^NGFR (–)/CK14 (+), which reflected the presence of post-mitotic differentiating cells, was observed in the supra-basal layers of the extended epithelium. BrdU (+)/p75^NGFR (+), which reflected the presence of epithelial stem cells, was detected sparsely in buccal basal epithelial cells after healing, and disappeared after 7 days. These results suggest that p75^NGFR (+) keratinocytes are localized in the basal layer, which contains oral epithelial stem cells, and retain the ability to proliferate in order to regenerate the buccal mucosal epithelium.