Immunhistochemischer Nachweis von Zytokeratinen in der bestrahlten Unterkieferspeicheldrüse der Wistar-Ratte

BACKGROUND: Damage to the salivary gland (SG) is a well-known sequela of radiotherapy in humans. In many cases irradiation damage causes xerostomia and problems of speech and swallowing. While the functional restriction and the radiogenic SG tissue damage is well documented using histomorphological, electron microscopic and enzyme histochemical methods, immunohistochemical analyses (IH) of the profile of cytokeratins (CK), epithelial differentiation markers, and their alterations in irradiated glands are rare.

METHODS: In 59 mandibular glands of rats, we investigated the distribution of CK by IH. The animals differed in age from 3 months to 2 years and pretreatment status (irradiation versus no irradiation). The IH were performed at selected time points (< 4 months/> or = 4-6 months/> 6 months).

RESULTS: The monoclonal antibodies (E3, Ks13.1, NCL5D3, K8.12; against CK 17, CK 13, CK 8 and CK 13/15/16, respectively) identified different epithelial 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). As typical results, E3 usually stained the ICD, SD, and ECD moderately to strongly and stained the GTC in trace amounts or slightly. K8.12 staining was restricted to ECD and MC. Differences in immunoreactivity were seen between irradiated and non-irradiated glands, predominantly with stronger staining in the irradiated group. A conspicuous finding was the stronger expression of CK 13 in irradiated ECD, ICD, and SD within a latency period of 4-6 months. A similar finding was demonstrated in ICD, ECD, and SD cells after incubation with CK 17 antibodies. In both instances, the staining profile of irradiated glands did not return to nontreatment levels in the long term after exposure.

CONCLUSIONS: Previous irradiation has to be considered when interpreting IH of salivary gland tissue, especially in studies on chronic degenerative diseases of the salivary glands.