Migration of Merkel cells in the labial mucous epithelium of adult rabbits following mental nerve resection.

Merkel cells in the lower labial mucosa of adult rabbits were studied electron microscopically, 9, 21, 28, and 50 days after resection of the mental nerves. By day 9, nerve fibers were completely retracted from the epithelial layer of the mucosa. On and after day 21, Merkel cells were located not only in the basal layer but also in the prickle or more superficial cell layers. The ultrastructure of the migrating Merkel cells was unchanged, both as to the amount and location of the specific cored granules in the cytoplasm, until the cells reached the granular cell layer. The position of the migrating Merkel cells differed from cell to cell, and migration continued for at least 50 days. A remarkably large number of immature Merkel cells was observed in the basal and suprabasal cell layers of the denervated epithelium even by day 50. Therefore, the possibility of the reproduction of Merkel cells exists. The migrating Merkel cells, as well as the keratinocytes in the same cell layer, had degenerated drastically in the parakeratinized cell layer. This seems to indicate that the Merkel cells belong to the line of keratinocytes.