Cytokeratin expression during regeneration of the intralobular duct in rat submandibular glands after YAG laser irradiation.

Changes in the expression of cytokeratin subunits during regeneration of the intralobular duct in partially injured rat submandibular glands were investigated. Limited parts of rat submandibular glands were injured by irradiation with YAG laser. Irradiated glands were investigated histologically and immunohistochemically using anti-cytokeratin monoclonal antibodies, RCK105 and CK19. Irradiated areas became necrotic one day after YAG laser irradiation. At three and five days, duct-like structures and epithelial clusters began to regenerate at the periphery of the remaining lobule. Epithelial clusters without ductal spaces were situated at the terminal portion of the duct-like structures. At seven and ten days, duct-like structures were composed of cuboidal or low columnar cells, and the number of epithelial clusters decreased. Immunohistochemically, cells of intralobular ducts in normal rat submandibular glands reacted to RCK105 and CK19. At three and five days, the epithelial cells of duct-like structures were positive for both antibodies. Many cells in the epithelial clusters showed negative reaction. However, in some epithelial clusters, inner cells and cells facing narrow luminal spaces were positive for both antibodies. At seven and ten days, positive reaction for both antibodies was identified in duct-like structures. This study showed that cells of the epithelial cluster were less mature than those of the duct-like structure, and that in the epithelial cluster, the inner cells were the first to differentiate into intralobular ductal cells.