Therapeutic delivery of microRNA-125a-5p oligonucleotides improves recovery from myocardial ischemia/reperfusion injury in mice and swine

Rationale: Clinical application of mesenchymal stem cells (MSCs) and MSC-derived exosomes (MSC-Exos) to alleviate myocardial ischemia/reperfusion (I/R) injury is compromised by the low cell engraftment rate and uncontrolled exosomal content. As one of their active ingredients, single-component microRNA therapy may have more inherent advantages. We sought to find an ideal microRNA candidate and determine whether it could reproduce the cardioprotective effects of MSCs and MSC-Exos. Methods: Cardiac function and myocardial remodeling in MSC, MSC-Exo, or microRNA oligonucleotide-treated mouse hearts were investigated after I/R injury. The effects of microRNA oligonucleotides on cardiac cells (macrophages, cardiomyocytes, fibroblasts, and endothelial cells) and their downstream mechanisms were confirmed. Large animals were also employed to investigate the safety of microRNA therapy. Results: The results showed that microRNA-125a-5p (miR-125a-5p) is enriched in MSC-Exos, and intramyocardial delivery of their modified oligonucleotides (agomir) in mouse I/R myocardium, as well as MSCs or MSC-Exos, exerted obvious cardioprotection by increasing cardiac function and limiting adverse remodeling. In addition, miR-125a-5p agomir treatment increased M2 macrophage polarization, promoted angiogenesis, and attenuated fibroblast proliferation and activation, which subsequently contributed to the improvements in cardiomyocyte apoptosis and inflammation. Mechanistically, Klf13, Tgfbr1, and Daam1 are considered the targets of miR-125a-5p for regulating the function of macrophages, fibroblasts, and endothelial cells, respectively. Similar results were observed following miR-125a-5p agomir treatment in a porcine model, with no increase in the risk of arrhythmia or hepatic, renal, or cardiac toxicity. Conclusions: This targeted microRNA delivery presents an effective and safe strategy as a stem cell and exosomal therapy in I/R cardiac repair.