Transforming growth factor beta 1 dependent regulation of Tenascin-C in radiation impaired wound healing.

Abstract

Following preoperative radiotherapy prior to ablative surgery of squamous epithelial cell carcinomas of the head and neck region fibrocontractive wound healing disorders occur. Tenascin-C is significantly increased in fibrotic tissue conditions and can be stimulated by the transcription factor NF kappa B p65. Previous studies showed a reduction of irradiation induced fibrosis during the wound healing process by anti-TGF beta(1)-treatment. The aim of the study was to clarify the question whether Tenascin-C expression is elevated in radiation impaired wounds and whether anti-TGF beta(1)-treatment is capable to influence Tenascin-C and NF kappa B expression. Wistar rats (male, weight 300-500 g) underwent preoperative irradiation of the head and neck region with 40 Gy, fractionated four times 10 Gy (16 animals), whereas 8 non-irradated animals served as a control. Four weeks after irradiation a free myocutaneous gracilis flap taken from the groin was transplanted to the neck. Eight animals additionally received 5 microg anti-TGF beta(1) into the graft bed by intradermal injection prior to each fraction of irradiation and on days 1-7 post-operation. On day 14 and 28 following surgery immunohistochemistry (ABC-POX method) was performed assessing the cytoplasmic NF kappa B and Tenascin-C staining in the transition area between transplant and graft bed. For quantitative considerations the labeling index (ratio: positive cells/total cells) was determined. A significantly altered expression of Tenascin-C in the preirradiated tissue was observed following anti-TGF beta(1)-treatment. NF kappa B protein was upregulated in irradiated animals and was significantly reduced in the anti-TGF beta(1) treated group on day 28 after transplantation. Tenascin-C expression is prolonged in irradiated animals as compared to non-irradiated tissue. Tenascin-C seems to be regulated by TGF beta(1) as the application of TGF beta(1)-neutralizing antibodies reduces Tenascin-C expression. Tenascin-C is a potentially useful marker for tissue remodeling due to its restricted distribution in adult and healthy tissue and a hallmark for developing fibrosis.