Chitosan-based polyelectrolyte nanocomplexes for delivery of miRNA-199a in cardiac regeneration

Ischemic heart disease is the main cause of death in developed countries, and full recovery remains unachievable. A potential cure can be based on utilizing miRNAs capable of triggering cardiac regeneration by stimulating cardiomyocyte proliferation. However, to deliver miRNAs efficiently, nanocarriers are required for protection from rapid cleavage in the extracellular milieu and successful uptake by cardiomyocytes. Here, we present biocompatible chitosan nanoparticles, formulated via a green polyelectrolyte complexation process, and efficiently loaded with miR199a-3p. Their safety and therapeutic potential were evaluated in vitro and in vivo. To enhance cardiac accumulation, we further explored the functionalization of these nanoparticles with tannic acid, a polyphenolic compound that exhibits favored cardiac targeting and sustained retention. Thus, we have optimized the miR-loaded chitosan-based formulation to achieve tunable sizes (100-300 nm) while maintaining high biocompatibility with HL-1 cardiomyocytes and primary murine or rat cardiomyocytes. Notably, miRNA-loaded nanoparticles boosted cardiomyocyte proliferation by up to 75%. Confocal microscopy confirmed successful uptake by cardiomyocytes. In vivo, no mortality or adverse effects were observed during the 4-day observation period, with miRNA expression increasing up to sixfold and target gene downregulation reaching 50%. These findings establish a proof of concept that chitosan-based polyelectrolyte complexes can serve as a safe and effective nanoplatform for delivering regenerative miRNAs to the heart, paving the way for next-generation cardiac therapies.