Mitochondrial dysfunction, oxidative stress, and impaired bioenergetics are central drivers of myocardial injury during ischemia-reperfusion (I/R). Mitochondrial transplantation (MTT) has emerged as a potential therapeutic approach, yet its effective dose range, requirement for mitochondrial integrity, and underlying molecular mediators remain unclear. This study aimed to identify the safe and effective dose range of MTT, determine whether intact mitochondria are required for cardioprotection, and define the contribution of Nrf2 signaling. Mitochondria were isolated from mesenchymal stem cells and validated by electron microscopy, confocal imaging, and mitochondrial membrane potential (MMP) assays. In dose-response experiments, cardiomyocytes tolerated up to 3μg/10,000 cells, whereas higher doses reduced viability, depolarized MMP, and increased reactive oxygen species (ROS). To assess functional recovery, Langendorff-perfused rat hearts underwent 30-minutes ischemia followed by 2-h reperfusion. Administration of 100 μg functional mitochondria at reperfusion significantly improved left ventricular developed pressure (LVDP; ∼50% vs. ∼20% in controls). In contrast, non-functional mitochondria (FCCP-treated, 2 μM, 1 h) failed to improve LVDP, confirming that viable mitochondria are essential. Complementary studies in isolated cardiomyocytes subjected to 30-minute hypoxia and reperfusion demonstrated that I/R increased ROS, depolarized MMP, elevated cytosolic Ca 2+ , reduced sarcoplasmic reticulum Ca 2+ content, diminished Ca 2+ transients, decreased ATP, and suppressed Nrf2 expression. Treatment with 1 μg mitochondria restored mitochondrial function, normalized Ca 2+ handling, improved Ca 2+ transients, increased ATP, and reinstated Nrf2 levels. Notably, Nrf2 inhibition (ML385, 20 μM) abolished these protective effects. MTT confers robust cardioprotection in I/R by restoring mitochondrial energetics, limiting oxidative stress, and preserving calcium homeostasis. These benefits require viable, polarized mitochondria and depend on Nrf2 activation, highlighting MTT as a promising mitochondria-targeted therapy with translational potential for ischemic heart disease. Supported by Ankara University BAP TSG-2024-3309.
Aryan et al. (Sun,) studied this question.