Immunhistochemischer Nachweis von extrazellulären Matrixproteinen in der bestrahlten Unterkieferspeicheldrüse der Ratte

BACKGROUND: Extracellular matrix proteins (EMP) form the main components of basement membranes (BM) and associated structures. Basement membranes influence tissue structure, exchange of substances, and cell growth and differentiation. While BM changes have been reported in malignant tumors and in inflammatory diseases, systematic studies of BM changes following irradiation are rare. Because functional and histomorphological damage to the salivary glands is a well known sequela of radiotherapy in humans, our goal was to describe possible BM changes using an experimental model and immunohistochemistry (IH).

METHODS: In 59 rat mandibular glands we investigated the distribution of EMP by IH. The animals differed in age from 3 months to 2 years and pre-treatment status (irradiation vs no irradiation). The analyses were performed at selected time points after completion of external irradiation (< 4 months [M]/> or = 4-6 M/> 6 M).

RESULTS: The polyclonal antibodies (anti-laminin [AL], anti-fibronectin [AF], anti-collagen III [AC-III], anti-collagen IV [AC-IV]) identified components of BM (laminin, collagen IV) and BM-associated structures (fibronectin, collagen III) in glandular tissue, in vascular walls, in nerve tissue, and the interstitial connective tissue. Various EMP were detected in different patterns. AL stained nerve tissue moderately and both different gland tissue structures and vascular walls (without adventitia) slightly, while excretory ducts and blood vessel adventitia were distinctly positive for AF. Fibronectin was also present in the connective tissue stroma. Significant differences were seen between irradiated and nonirradiated glands, often with generally stronger and more extensive staining in the irradiated group. For example most tissue structures showed distinctly increasing immunostaining for AL in positive correlation with increasing latency of irradiation up to 6 months. The age was of minor importance.

CONCLUSIONS: Previous irradiation has to be considered when interpreting the EMP profile of salivary gland tissue, especially in studies both on chronic degenerative diseases and tumor differentiation developing in an area that has undergone radiation therapy.