Transforming growth factor beta1 and beta2 (TGFbeta2 / TGFbeta2) 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 TGFbeta(1), TGFbeta(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 TGFbeta(1), LAP, and TGFbeta(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 TGFbeta(1) (range, 19.0-33.0), LAP (14.0-21.0), and TGFbeta(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 TGFbeta(1) (11.0-21.0), LAP (1.0-8.0), and TGFbeta(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 TGFbeta(1) (37.0), LAP (19.0), and TGFbeta(2) (16.7-33.4) was observed on the 3rd postoperative day in contrast to the transition area in non-irradiated graft beds (activated TGFbeta(1) 26.0, LAP 7.0, and TGFbeta(2) 0.l).

CONCLUSION

The radiation induced, increased de novo synthesis of LAP, activation of TGFbeta(1), and increased expression of TGFbeta(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 TGFbeta(1,) LAP, and TGFbeta(2) might possess prognostic value with regard to wound healing and fibrosis in previously irradiated graft beds.