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Purpose: In this study, we evaluated the individual and combined effects of mesenchymal stem cells (MSCs) and sildenafil citrate (SC) on the viability of pedicled perforator flaps in which ischemia/reperfusion injury developed after induction of primary ischemia., Materials and Methods: Seven Sprague-Dawley rats were used as donors of cells. Rectangular flaps (7 × 7 cm 2 ) were created featuring the right second epigastric musculocutaneous perforator in 63 male Sprague-Dawley rats. The animals were randomly divided into two experimental groups (based on the ischemia time of 4 or 8 hours) and a control group. Each of the experimental group was further divided into four subgroups with no treatment, subcutaneous administration of MSCs after termination of ischemia, intraperitoneal administration of SC after termination of ischemia, and combined MSCs and SC treatments at the end of the period of ischemia (n = 7 for each subgroup). A sham group with no-ischemia to flap was used as the control (n = 7). On day 7, viable areas on the flaps were calculated from photographs. The levels of the antioxidative enzymes, such as superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX), were analyzed in tissue samples obtained from the most distal regions of the flap prior to ischemia and on day 7 after induction of ischemia., Results: No difference was detected between the no-ischemia group and 4-hours SC-treated subgroup, 4-hours combined MSC and SC treated subgroup, 8-hours MSC-treated subgroup, or 8-hours SC-treated subgroup (P > 0.05). In 4-hours ischemia group, the viable flap area of combined MSC and SC treated subgroup was significantly greater than that of the ischemia subgroup (17.17 ± 12.56 cm 2 vs. 7.24 ± 7.17 cm 2 ; P = 0.015). However, in 8-hours ischemia group, the viable flap area of MSC- treated subgroup was significantly greater than that of the ischemia subgroup (2.69 ± 3.71 cm 2 vs. 14.52 ± 8.57 cm 2 ; P = 0.004). There were no significant differences in SOD, CAT, and GPX levels detected between no-ischemia group and any of the treated subgroups in 4- and 8-hours ischemia groups (P > 0.05). However, SOD, CAT, and GPX levels in the no-ischemia group were lower than that in 4-hours ischemia control subgroup or 8-hours ischemia control subgroup (P < 0.05)., Conclusion: In this rat pedicled perforator based abdominal flap, we found that after primary ischemia, application of MSCs and SC, either individually or in combined form, significantly enhanced antioxidant enzyme levels compared with those in the control group, and provided protection against ischemia/reperfusion injury. The two treatments acted synergistically to protect against damage after 4 hours of ischemia, but either treatment alone more effectively enhanced viable flap area after 8 hours of ischemia, although some flap damage was apparent. © 2015 Wiley Periodicals, Inc. Microsurgery 36:402-409, 2016., (© 2015 Wiley Periodicals, Inc.)