Immunohistological study of small Rho GTPases and β-catenin during regeneration of the rat submandibular gland.

Our study immunohistochemically evaluated the localization patterns of small Rho GTPases and β-catenin during regeneration of the rat submandibular gland. After 7 days of obstruction, regenerating glands were collected at days 0, 3, 7, 11 and 14 after duct release to study regeneration. RhoA was detected strongly and RhoC was detected weakly in the cytoplasm of newly formed acinar cells from day 3 to 7, and both RhoA and RhoC at the basal site and cytoplasm were detected moderately from day 11 to 14. RhoB was detected strongly and moderately in the cytoplasm of newly formed and matured acinar cells, respectively, and detected strongly in duct-like structures (DLSs) and intercalated ducts (ICDs). Rac1 was detected at the cell-cell and subcellular region, but β-catenin was not observed in newly formed acinar cells. Rac1 immunolabeling gradually reduced, and the β-catenin staining pattern became stronger. p-Rac1, a phosphorylated form of Rac1, was observed in the cytoplasm of newly formed acinar cells. At apical and subcellular region of DLSs and ICDs, Rac1 and β-catenin were detected. These findings suggest that RhoA and RhoC might be involved in the actin cytoskeleton at the basolateral site of regenerating acinar cells, and RhoB might play a unique role in regenerating acinar cells and in DLSs and ICDs. Rac1 and β-catenin at the cell-cell region might play important roles in cell-cell adhesion and the differentiation of regenerating acinar cells, as well as actin reconstruction at apical and subcellular regions of DLSs and ICDs.