Dose-response relationships on the expression profile of cytokeratins and vimentin in rat submandibular glands following fractionated irradiation

OBJECTIVE: The extent of radiogenic damage in salivary gland (SG) tissue depends on the radiation dose (RD), the fractionation (FN) and the localization of SG in the radiation field (RF). While the functional restriction and the radiogenic SG tissue damage are well documented using histomorphological, electron-microscopic and enzyme-histochemical methods, immunohistochemical analysis (IH) of cytokeratins (CK), epithelial differentiation markers, and vimentin, a marker of mesenchymal cells, are rare. Previous studies have shown stronger immunoreactivities of CK in irradiated glands exposed to 60 Gy total dosage. This study was performed to examine dose dependence and alterations related to age, RF, and latency of irradiation.

METHODS: In 124 rat mandibular SG we investigated the vimentin and CK staining profile dependent on age [1 year (y) vs. 1 1/2 y], on FN [2 Gy/day up to a total dosage of 20/40/60 Gy (x-rays)], on RF (inside vs. outside RF) and on the time since irradiation (1/2 y vs. 1 y) using IH.

RESULTS: The mouse monoclonal anti-CK antibodies [(AB) D5/16B4, Ks 13.1, E 3, K8.12, Ks 18.04, against CK 5-6, CK 13, CK 17, CK 13-15-16, CK 18) and the polyclonal anti-vimentin AB GP53 identified different epithelia and mesenchymal structures in rat SG tissue, including excretory duct cells (ECD), striated duct cells (SD), granular convoluted tubules (GTC), intercalated duct cells (ICD) and myoepithelial cells (MC). MC and mesenchymal cells were positive for vimentin AB. The different CK were detected in cell type-specific patterns and at variable levels in non-irradiated SG. In irradiated SG most cell types showed significantly stronger staining for various CKs. With increasing RD from 20 Gy to 60 Gy we found an increasing staining reaction. The CK staining profile up to 20 Gy was non-uniform and did not differ significantly from controls. Age and time since irradiation played a minor role or had no significant effect on staining.

CONCLUSIONS: The CK and vimentin immunoreactivity showed dose-dependent increasing expressions, which could contribute to radiogenic cell and tissue damage. In some tissue structures a possible scattered irradiation effect should be mentioned. Age and time since irradiation (chosen in the study) had a minor or insignificant effect on staining profiles.