Exogenous modulation of TGF-beta(1) influences TGF-betaR-III-associated vascularization during wound healing in irradiated tissue.

Abstract

Following preoperative radiotherapy prior to ablative surgery of squamous epithelial cell carcinomas of the head and neck region, wound-healing disorders occur. Previous experimental studies showed altered expression of transforming growth factor-(TGF-)beta isoforms following surgery in irradiated graft beds. Altered levels of TGF-beta(1) are reported to promote fibrosis and to suppress vascularization during wound healing, whereas expression of TGF-beta receptor-III (TGF-betaR-III) is associated with vascularization. The aim of the study was to analyze the influence of anti-TGF-beta(1) treatment on TGF-betaR-III-associated vascularization in the transition area between irradiated graft bed and graft. Wistar rats (male, weight 300-500 g) underwent preoperative irradiation of the head and neck region with 40 Gy (four fractions of 10 Gy each; n = 16 animals). A free myocutaneous gracilis flap taken from the groin was then transplanted to the neck in all rats. The time interval between operation and transplantation was 4 weeks. Eight animals received 1 micro g anti-TGF-beta(1) into the graft bed by intradermal injection on days 1-7 after surgery. On days 3, 7, 14, 28, 56, and 120, skin samples were taken from the transition area between transplant and graft bed and from the graft bed itself. Immunohistochemistry was performed using the ABC-POX method to analyze the TGF-betaR-III and E-selectin expression. Histomorphometry was performed to analyze the percentage and the area of positively stained vessels. A significantly higher expression of TGF-betaR-III was seen in the irradiated and anti-TGF-beta(1)-treated graft bed in comparison to the group receiving preoperative irradiation followed by transplantation alone. The percentage of TGF-betaR-III positively staining capillaries from the total amount of capillaries in the anti-TGF-beta(1)-treated graft bed was higher than in the group irradiated only. The total area of capillaries was also higher in the TGF-beta(1)-treated group. Neutralizing of TGF-beta(1) activity in irradiated tissue undergoing surgery leads to a higher expression of TGF-betaR-III and increased vascularization. TGF-betaR-III seems to be associated with newly formed blood vessels during neovascularization in wound healing.