The role of myoepithelial cells in the short-term radiogenic impairment of salivary glands. An immunohistochemical, ultrastructural and scintigraphic study

Background and Purpose: The aim of this study was to evaluate the early dose-related functional impairment of salivary glands after radiation, using sialoscintigraphy, immunohistochemistry and electron microscopy in an established rabbit experimental model. Materials and Methods: Twelve rabbits were used for the study. Eight were scintigraphically examined prior to and 24 hours after 15/30 Gy (4 rabbits each). The irradiated glands were examined immunohistochemically using monoclonal antibodies to alpha smooth muscle actin (ASMA), vimentin and Ki-67 proliferation antigen. Ultrastructural investigation was also performed Four control rabbits were sham-treated and provided normal salivary gland tissue. Results: There was a significant increase of the ^99mTc-pertechnetate uptake in the irradiated parotid glands (p<0.05) and a highly significant one in the superficial mandibular glands (p<0.001). Immunohistochemically a significant loss of ASMA and vimentin-stained myoepithelial cells and a decrease of the proliferating rate in the acinar cells could be assessed in both irradiated glands. Ultrastructurally, rarefaction and focal condensation of the myofilaments of the myoepithelial cells in both irradiated glands was observed. No dose-related effect could be assessed. Conclusion: Early functional impairment of salivary glands after radiation could be revealed as early as 24 hours after radiation. The considerable myoepthelial cell impairment may explain the secretory retention assessed scintigraphically and provide -apart from acinar cell damage - a new aspect in the pathogenesis of radiogenic impairment of salivary glands.