ObjectiveTo study the effects of the new small molecular oxygen free radical scavenger Tempol on the survival and vasculogenesis of the long random pattern skin flap (LRPSF) and its mechanism. MethodsEighty-four male Sprague Dawley rats were randomly divided into control and Tempol groups (42 rats in each group). LRPSF of 9 cm×3 cm in size were prepared on the backs of rats in two groups based on the Mcfarlane flap. Rats were administered with Tempol (100 mg/kg) in the Tempol group and with normal saline in the control group by intraperitoneal injection at 15 minutes before operation and at 1-7 day after operation. The rat and the skin flap survival conditions were observed after operation; the survival rate of skin flap was measured, and the vascular structure, vascular volume, and total length of blood vessels were analyzed with Micro-CT three-dimensional imaging after 7 days; HE staining was used to observe the structure of the skin flaps and inflammation, immumohistochemical staining to observe vascular endothelial growth factor (VEGF) expression; water-soluble tetrazolium-1 method was used to measure the content of superoxide dismutase (SOD) and malondialdehyde (MDA), and ELISA to detect the expressions of tumor necrosis factor α (TNF-α) and interleukin 6 (IL-6) after 1, 3, and 7 days. ResultsAll of rats survived after operation, without hemorrhage, edema, and infection. With the extension of time, necrosis occurred in the distal part of the skin flaps in 2 groups, but the necrosis degree of the Tempol group was lower than that of control group; meanwhile, the blood vessel distribution and continuity were better than those of control group. The skin flaps survival rate, vascular volume, and total length of blood vessels of Tempol group were significantly higher than those of control group after 7 days (P<0.05). The clearer skin flaps structure, lighter inflammation reaction and inflammation cell infiltration, and higher VEGF staining intensity were observed in the Tempol group than the control group after 7 days. There was no significant difference in SOD, MDA, and TNF-α, and IL-6 contents between the 2 groups at immediate after operation. SOD significantly increased, but MDA, TNF-α, and IL-6 contents significantly decreased in the Tempol group when compared with control group after 1, 3, and 7 days (P<0.05). ConclusionTempol can significantly promote the LRPSF survival rates, its mechanism is closely related to the promotion of vasculogenesis and reduction of oxidative stress and inflammation.