Merkel cell development in the wound healing in the labial mucosa of adult rabbits.

Merkel cell development was studied in the regenerative labial mucous membrane of adult rabbits. Fullthick wounds were made on the inferior labial mucous membrane of the rabbits, then the regenerative mucous membrane was examined by electron and light microscopy at time intervals of 2, 7, 10, 14, 21 and 30 days after the injury. By 7 days, the regenerative area of the mucous membrane was replaced with a dense lamellar connective tissue, which was mainly composed of alternately arranged collagen fiber layers and fibroblasts, and an overlying stratified squamous epithelium. No Merkel cell was found 7 days after the injury. Ten days after the injury, a few very immature Merkel cells were identified in the regenerative epithelium. The Merkel cells increased in number and matured in structure during the course of the following regenerative period. Thirty days after the injury, the wounded area healed without forming a scar tissue, and the regenerated epithelial ridges usually included regular type Merkel cells. As adult animals were used in this experiment, the reproduction of the Merkel cell in the regenerative epithelium seemed to be independent of the undifferentiated neuroectodermal tissue.