Development of new advanced therapies to mitigate ischemia-reperfusion-induced injury during acute myocardial infarction

Abstract

Current therapeutic approaches against acute myocardial infarction (AMI) are focused on myocardial ischemic zone revascularization. The most common strategy is called primary angioplasty, in which a catheter is introduced to unblock the affected artery and restore blood flux, in a process called reperfusion. Nevertheless, an additional injury on cardiac tissue is caused after reperfusion, and the combination of primary angioplasty with the use of cardioprotective molecules has emerged as a potential strategy to reduce cardiac tissue injury. Two new cell-free therapeutic strategies to preconditionate myocardial ischemic area before reperfusion have been proposed to reduce cardiac injury after AMI. The first therapeutic strategy proposed consisted on the input of a free fatty acid (di-docosahexaenoic acid, diDHA) covalently bound to a polymeric backbone (poly-L-glutamic acid, PGA) in order to increase diDHA solubility and stability and modulate its effect on target cells. Results showed that PGA-diDHA6.4 conjugate administration during ischemia protected cardiomyocytes from reperfusion-induced injury, as apoptotic number of cells and oxidative stress was reduced, and mitochondrial function was less affected when compared to untreated cells. In addition to this, PGA-diDHA6.4 also showed therapeutic effects when locally administered in an ischemia-reperfusion in vivo model in rats and pigs, where a modest reduction of area at risk was observed compared to control groups. The second cell-free strategy proposed in this work was focused on enhancing the therapeutic potential of small extracellular vesicles (SEV or exosomes) isolated form mesenchymal stromal cells (MSC) conditioned media. Previous studies have described the therapeutic potential of paracrine factors released by MSC, where both soluble factors and vesicular components are included. In particular, SEV have gained special attention. Several stretegies, such as genetic modification or cell preconditioning, have been tested to enhance the MSC therapeutic potential. In this work, it was proposed MSC genetic modification in order to load proteins of interest on SEV and potentiate its native therapeutic potential. Based on previous findings, where it has been described a potential anti-fibrotic role of oncostatin-M (OSM) in AMI context, we decided to incorporate OSM on SEV surface by its fusion to CD81 tetraspanin, a protein naturally loaded on SEV surface, in order to trigger functional effects on target cells. OSM sequence modification was necessary in order to load the protein on SEV surface efficiently, and preliminary data showed that modified OSM-CD81 loaded on SEV had a functional effect on human ventricular cardiac fibroblasts. Concretely, decrease of proliferation rate after starvation and telo-Collagen1α1 location pattern modification was observed after stimulation with a pro-fibrotic cocktail (containing TGFβ-1, α-dextran and ascorbic-L-acid sulphate) in vitro when cells were treated with modified OSM-CD81-SEV compared to ctrl and CD81-loaded SEV treatments. Overall, two new advanced cell-free therapies with preliminary promising results have been proposed in order to reduce myocardial injury after AMI in terms of cardiomyocytes apoptosis reduction and fibrosis mitigation.