The effects of botulinum toxin A on survival of rat TRAM flap with vertical midline scar

Abstract

The transverse rectus abdominis musculocutaneous (TRAM) flap has been widely used in various reconstructive surgeries. Recently, there have been reports regarding the positive effect of botulinum toxin A (BoTA) on flap survival. We hypothesized that pretreatment with BoTA could augment the survival of pedicled TRAM flaps with a vertical midline scar. Twenty-four Sprague-Dawley rats were randomly divided into 2 groups, namely, control group and BoTA group. Five days after a vertical midline incision, the BoTA group was pretreated with BoTA, whereas the control group was pretreated with normal saline. Ten days after the initial incision, the TRAM flap was harvested. We evaluated the gross flap survival and analyzed the overall histologic change, lumen area of pedicle, and microvessel density with immunohistochemistry. Reverse transcription polymerase chain reaction was performed for the evaluation of angiogenesis-related factors. In the BoTA group, the gross flap survival rate was significantly higher than that in the control group on both ipsilateral and contralateral sides (P < 0.001). In the BoTA group, a significant increase in pedicle lumen area was observed (P < 0.001). In the control group, mild to moderate epidermal necrosis was seen; microvessels were relatively small compared with those of the BoTA group. According to immunohistochemistry, the number of CD31 positively stained vessels was significantly higher on the contralateral side in the control group compared to that in the BoTA group (P < 0.001). The relative messenger RNA (mRNA) expression of CD31 was significantly lower in the BoTA group than that in the control group on both ipsilateral and contralateral sides (P < 0.001). Meanwhile, the relative mRNA expression of VEGF was significantly higher in the BoTA group than in the control group on both ipsilateral and contralateral sides (P < 0.001).We believe that preoperative BoTA therapy is a feasible method to improve circulation of the rat TRAM flap with a vertical midline incision scar.