Transforming growth factor beta 1 and beta 2 (TGF beta(2)/TGF beta(2)) profile changes in previously irradiated free flap beds

Background. Following preoperative radiotherapy prior to ablative surgery of squamous epithelial carcinomas of the head and neck region, inflammatory changes and the expression of cytokines involved in wound healing could be observed. These processes lead to a delayed healing of free flaps in the graft bed. The aim of the present experimental study was to analyze the expression profiles of transforming growth factor (activated TGF beta (1), TGF beta (2)) and latency-associated peptide (LAP) in the irradiated graft beds and the transition area between grafts and irradiated graft beds. Methods. In Wistar rats (male, weight 300-500 g) undergoing preoperative irradiation of the neck region with 30 Gy (30 animals) and non-irradiated rats (42 animals), a free myocutaneous gracilis flap taken from the groin was transplanted to the irradiated region of the neck. The interval between irradiation and transplantation was 4 weeks. In each group on postoperative days 3, 7, 14, and 28, cytoplasmatic expression of activated TGF beta (1), LAP, and TGF beta (2) was analyzed by immunohistochemistry to determine labeling indices (positive stained cells/total cells). Results. The success rate in graft beds irradiated with 30 Gy was 76% and in non-irradiated graft beds was 86% (p = .02). In the graft beds irradiated with 30 Gy, there was an increased expression of activated TGF beta (1) (range, 19.0-33.0), LAP (14.0-21.0), and TGF beta (2) (3.0-19.5) together with obvious fibrosis. The expression was located in perivascular fibroblasts and endothelial cells. In contrast, a lower expression of activated TGF beta (1) (11.0-21.0), LAP (1.0-8.0), and TGF beta (2) (0.0-0.9) (p = .006) was observed in non-irradiated graft beds. In the transition area between graft and irradiated graft bed, high expression of activated TGF beta (1) (37.0), LAP (19.0), and TGF beta (2) (16.7-33.4) was observed on the 3rd postoperative day in contrast to the transition area in non-irradiated graft beds (activated TGF beta (1), 26.0, LAP 7.0, and TGF beta (2) 0.1) Conclusion. The radiation induced, increased de novo synthesis of LAP, activation of TGF beta (1), and increased expression of TGF beta (2) may represent at least one mechanism for the increased fibrosis and wound healing disorders seen in irradiated tissues and in the transition area to graft tissue. The expression of TGF beta (1), LAP, and TGF beta (2) might possess prognostic value with regard to wound healing and fibrosis in previously irradiated graft beds. (C) 2002 John Wiley & Sons, Inc.