Electroacupuncture preconditioning and mitochondria-associated outcomes in animal models of myocardial ischemia-reperfusion injury: a systematic review and meta-analysis

Background Mitochondrial dysfunction is central to myocardial ischemia-reperfusion injury (MIRI). Although acupuncture preconditioning has shown cardioprotection in animal models, no systematic review has quantitatively synthesized mitochondria-associated outcomes. Objective To evaluate the effects of acupuncture preconditioning on prespecified mitochondria-associated outcomes—reactive oxygen species (ROS), malondialdehyde (MDA), adenosine triphosphate (ATP), Bax, B-cell lymphoma 2 (Bcl-2), and apoptotic index (AI)—and infarct size in animal MIRI models, and to explore the potential mechanisms underlying its cardioprotective effects. Methods Eight databases were searched from inception to 26 July 2026. Randomized controlled animal studies of acupuncture preconditioning in MIRI were included. Two reviewers screened studies, assessed risk of bias (SYRCLE), and extracted data; graphical data were digitized by one reviewer and verified by another. Random-effects meta-analyses used standardized mean differences (SMDs) with Hartung-Knapp-Sidik-Jonkman adjustment. Results Thirty-four publications involving 586 animals were included: 33 electroacupuncture and 1 manual acupuncture. Thirty-three studies were pooled, and one study was qualitatively synthesized because its outcome direction could not be harmonized. Acupuncture preconditioning (predominantly electroacupuncture) reduced infarct size (SMD=-2.69, 95% CI −3.57 to −1.82, I 2 = 72.9%), MDA (−3.76, −6.22 to −1.29, I 2 = 86.8%), ROS (−4.02, −7.18 to −0.85, I 2 = 92.1%), Bax (−6.52, −11.43 to −1.62, I 2 = 93.7%), and AI (−6.36, −10.36 to −2.36, I 2 = 96.5%), and increased ATP (3.21, 2.12 to 4.29, I 2 = 69.9%) and Bcl-2 (8.14, 3.82 to 12.45, I 2 = 94.7%). Subgroup analyses found significant effect modification only for Bcl-2 (species and reperfusion duration); heterogeneity remained high. Egger's test did not indicate publication bias, but trim-and-fill rendered ROS non-significant. Certainty was moderate for most outcomes and low for Bax. Conclusion Electroacupuncture preconditioning was associated with reduced myocardial injury and favorable mitochondria-associated changes in animal MIRI models; only one manual acupuncture study was included, so these findings should not be generalized to acupuncture as a whole. These findings cannot establish mitochondrial protection as a causal mechanism; other pathways may also contribute and were not synthesized. Extreme effect sizes for ROS, Bax, Bcl-2, and AI may be overestimated. Evidence is preclinical and hypothesis-generating; sham-controlled studies are needed. Systematic Review Registration https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD420261477352 , PROSPERO CRD420261477352.