The study of oxygen free radical scavenger in improving expanded flap's viability and mechanism of protecting blood vessels in rats

Objective To study the effect of oxygen free radical scavenger in improving expanded flap's viability and mechanism of protecting blood vessels in rats. Methods Forty-eight adult SD rats were randomly divided into control group, vitamin E treated group and edaravone treated group, sixteen rats in each group. A soft tissue expander of 30 ml was put into back of every rat in all the three groups. After the operation, normal saline was injected into every soft tissue expanders regularly until the total volume reached to 32 ml. All the soft tissue expanders were removed in the other operation, and then formed a flap sized 2 cm×6 cm in the expanded area of back with the pedicle located at the trailing side. After flaps were formed immediately, vitamin E injection (100 mg/kg), edaravone injection (10 mg/kg) and 1 ml normal saline were respectively injected into rats in vitamin E treated group, edaravone treated group and control group via the tail veins; the frequency of injection was once every 12 hours and until 3 days after the operation.24 hours after the operation, samples of flaps were harvested from eight rats which selected randomly from each group, calculated the apoptotic ratio of cells in vascular wall which located in the middle and distal of the flaps through situ labeling.7 days after the operation, calculated the flap's viability of each group, and marked blood vessels which located in the middle of the flaps by immunohistochemical staining for calculating the average number of vessels subcutaneous flaps. Results 24 hours after the operation, the apoptotic ratio of cells in vascular wall that located in middle and distal of the flaps were respectively (12.47±1.58)%, (23.35±2.46)% in vitamin E treated group and (11.01±1.67)%, (18.94±1.35)% in edaravone treated group; all of the ratio were significantly lower than that in control group correspondingly with the ratio (15.82±2.25)%, (28.34±1.17)% (P<0.05); and in edaravone treated group, the apoptotic ratio of cells in vascular wall that located in distal of the flaps was significantly higher than that in vitamin E treated group(P<0.05). 7 days after the operation, the flaps' viability and the average number of subcutaneous vessels were respectively (64.17±2.82)%, (11.52±1.09)/HP in vitamin E treated group and (73.66±3.24)%, (13.63±1.78)/HP in edaravone treated group; all of the results were significantly higher than that in control group correspondingly with the flaps' viability and the average number of subcutaneous vessels (41.92±3.59)%, (4.30±0.86)/HP (P<0.05); and the flaps' viability and the average number of subcutaneous vessels in edaravone treated group was significantly higher than that in vitamin E treated group (P<0.05). Conclusion Edaravone is more effective than vitamin E in improving expanded flap's viability; the mechanism is related to protecting structure and function of blood vessels, and then improving blood circulation of distal flaps. Key words: Edaravone; Vitamin E; Expanded Flap; Ischemia/reperfusion Injury; Blood vessels