Cardiomyocyte-targeted siRNA delivery by prostaglandin E₂-Fas siRNA polyplexes formulated with reducible poly(amido amine) for preventing cardiomyocyte apoptosis

A cardiomyocyte-targeted Fas siRNA delivery system was developed using prostaglandin E₂ (PGE₂)-modified siRNA polyplexes formed by a reducible poly(amido amine) to inhibit cardiomyocyte apoptosis. PGE₂, which was used as a specific ligand for cardiomyocyte targeting, was conjugated to the terminal-end of the sense siRNA (PGE₂-siRNA). The reducible cationic copolymer, synthesized via Michael-type polyaddition of 1,6-diaminohexane and cystamine bis-acrylamide (poly(DAH/CBA)), tightly condensed the PGE₂-siRNA conjugate to form nanosize polyplexes having a diameter of 100-150 nm. The PGE₂-siRNA/poly(DAH/CBA) polyplexes decomplexed to release PGE₂-siRNA in a cytosolic reducing environment due to the degradation of the reducible poly(DAH/CBA). The cellular uptake of the PGE₂-siRNA/poly(DAH/CBA) polyplex was increased in rat cardiomyocytes (H9C2 cells) due to PGE₂ receptor-mediated endocytosis. When H9C2 cells were transfected with siRNA against Fas, a key regulator of ischemia-induced apoptosis, the PGE₂-Fas siRNA/poly(DAH/CBA) polyplex delivery system led to a significant increase in Fas gene silencing, resulting in inhibition of cardiomyocyte apoptosis. The PGE₂-Fas siRNA/poly(DAH/CBA) polyplex did not induce interferon-alpha in peripheral blood mononuclear cells. These results suggest that the PGE₂-Fas siRNA/poly(DAH/CBA) polyplex formulation may be clinically applicable as a cardiomyocyte-targeted Fas siRNA delivery system to inhibit apoptosis in cardiovascular disease.