Abstract: Objective To observe the effects of platelet-rich plasma (PRP) on the survival of ultra-long dorsal random flaps in rats. Methods Sixteen male Sprague Dawley rats aged 6 to 8 weeks (the same below) were sacrificed to collect whole blood of 9 to 10 mL from each rat, and PRP was prepared by modified APPLE method. The platelet count of retained whole blood and PRP detected by automated blood cell analyzer showed that PRP was made successfully. The other thirty-two rats were collected and divided into PRP group and control group according to the random number table, with 16 rats in each group. One rectangular ultra-long random flap with area of 8 cm×2 cm was made on the back of each rat and replanted in situ. The equidistant 3 points were designed on both sides of the flap of each rat. Rats in PRP group were injected with 0.1 mL PRP from dermis and subcutaneous tissue of each injection point, while rats in control group were injected with the same volume of normal saline. Eight rats in each group were sacrificed at post operation hour (POH) 24 and on post operation day (POD) 7. On POD 7, survival of flaps of rats in 2 groups was observed, and the survival rates of flaps were calculated. On POD 7, the proximal, middle, and distal flaps of rats in 2 groups were collected, and histological changes of the flaps of rats in 2 groups were observed with hematoxylin-eosin staining. At POH 24 and on POD 7, flaps in 3 to 4 cm to pedicles were taken to detect mRNA expressions of vascular endothelial growth factor (VEGF), platelet-derived growth factor AA (PDGF-AA) and PDGF-BB by real-time fluorescent quantitative reverse transcription polymerase chain reaction, and to determine content of nitric oxide by nitrate reductase method. Data were processed with t test. Results (1) On POD 7, flaps of rats in PRP group were dry without purulent exudate, and covered with scab, and the pink new skin emerged after scab fell off. On POD 7, flaps of rats in control group were with a large amount of inflammatory exudates, 1/2 to 2/3 of flaps at the distal were with necrosis and covered by scab which was not easy to be stripped. The survival rate of flap of rats in PRP group was (67±6)%, significantly higher than (52±10)% of rats in control group (t=1.94, P<0.05). (2) There were no obvious inflammatory cell infiltration and a number of microvessels, and fibrous tissue arranged neatly in the proximal flaps of rats in PRP group. There were a few of inflammatory cell infiltration and a number of microvessels, and fibrous tissue arranged slightly disorderly in the middle flaps of rats in PRP group. There were many more inflammatory cell infiltration and microvessels, a small amount of vascular embolism, and fibrous tissue arranged disorderly in the distal flaps of rats in PRP group. There were a large number of inflammatory cells infiltration and a few of microvessels, and fibrous tissue arranged disorderly in the proximal, middle, and distal flaps of rats in control group. (3) At POH 24 and on POD 7, mRNA expressions of VEGF, PDGF-AA, and PDGF-BB of rats in PRP group were significantly higher than those of rats in control group (t=6.46, 5.61, 2.88, 10.18, 6.10, 7.67, P<0.001). (4) At POH 24, content of nitric oxide in flap of rats in PRP group was (5.0±0.9) μmol/g, significantly higher than (3.4±0.9) μmol/g of rats in control group (t=19.14, P<0.001). On POD 7, content of nitric oxide in flap of rats in PRP group was (3.3±0.8) μmol/g, which was close to (3.0±0.6) μmol/g of rats in control group (t=2.93, P>0.05). Conclusions PRP can improve the survival rate of ultra-long dorsal random flap in rats, which may be related to regulation of angiogenesis related factors, increase of nitric oxide content, and inhibition of excessive apoptosis of cells of PRP, so as to alleviate ischemical reperfusion injury and improve microcirculatory disturbance.