Regeneration of Keratinocytes, Langerhans Cells, Merkel Cells and Melanocytes after Removal of the Palatal Mucosa in the Early Healing Period

Abstract

Abstract：This study investigated the process of wound healing in the palatal mucosa, focusing on the proliferation and differentiation of keratinocytes, and regeneration of the basement membrane, Langerhans cells, Merkel cells and melanocytes. Golden hamsters were used as experimental animals and the entire fourth palatine ruga including the periosteum was removed mechanically with a scalpel. Control and experimental animals were sacrificed 3, 7, 14 and 21 days later. Maxillae were removed and fixed with 10％ formalin. Paraffin sections were then cut and immunohistochemically stained. For immunohistochemical staining, antibodies against PCNA for detecting the proliferating cells, CK14 and CK13 for epithelial differentiation, type IV collagen for the basement membrane, S-100for Langerhans cells and melanocytes, and CK20 for Merkel cells were used. At 14 days, the wound regions were covered with epithelium. CK14 and CK13 staining showed that epithelial differentiation had not been completed either in peripheral or central regions by 21 days. Type IV collagen was detected only in some parts of the epithelial basement membrane on day 14 and 21 in the central region. No S-100 or CK20-positive cell was found in the regenerated epithelium through 21 days in the peripheral regions and the central region. These results suggest that wound healing of the palatal mucosa seems to be macroscopically normal, but normalization of epithelial differentiation and regeneration of the basement membrane require a substantial amount of time. It is also suggested that the immune functions of Langerhans cells and the protective functions of melanocytes cannot regenerate, and that the absence of Merkel cells reduces sensory perception for at least 21 days.