P6348Phospholamban antisense oligonucleotides drive the reversal of cardiac dysfunction and multiple heart failure parameters during murine dilated cardiomyopathy

Abstract

Abstract Background Mice lacking muscle LIM protein (Mlp/Cspr3 −/−) develop dilated cardiomyopathy (DCM). Previous work established this model to be amenable to improvements in cardiac function by genetic ablation of phospholamban (PLN). Purpose To test the hypothesis that therapeutic reductions of PLN would similarly improve cardiac function, Mlp KO mice were administered an antisense oligonucleotide (ASO) targeting PLN. Methods Echocardiography measurements of ejection fraction (EF), end-diastolic volume (EDV) and end-systolic volume (ESV) were performed before and after treatment. In addition, global transcriptome profiling using 3'RNA-seq was performed to identify gene expression changes in diseased Mlp KO mice and following PLN ASO treatments. Mlp KO mice with ejection fraction (EF%) of less than 45% (median, 37.6%; interquartile range, 32.2–42.0%) were treated with vehicle (n=10) or PLN ASO (n=9) for 4 weeks. Results Three subcutaneous injections of PLN ASO were administered to Mlp KO mice resulting in 50–70% PLN reductions. Echocardiography performed at study end revealed improvements of EF (60±8 vs. 46±12%), ESV (31±11 vs. 56±21μl) and EDV (79±22 vs. 100±25μl) with PLN ASO treatment. Corrected for baseline values, PLN ASO treatment improved all echocardiographic measurements (p<0.001). Transcriptional analyses revealed that PLN ASO treatment reduced expression of heart failure related markers, such as Myh7 (−70%), Nppa (−72%), Nppb (−71%), Acta1 (−84%) and Ankrd1 (−40%), p<0.05 vs. vehicle. In addition, genes not previously known to be dysregulated in this model, Edn3 and Xirp2, were identified and shown to be reduced following PLN ASO treatment by 71% and 67%, respectively (p<0.001). Bioinformatic analysis suggested improvement of known and novel heart failure associated pathways by PLN inhibition in this model. In conclusion, antisense inhibition of PLN reduced functional and transcriptional indices of heart failure in a DCM model. In view of the failed CUPID trials, a gene therapy approach to improve SERCA2a activity, targeting PLN with ASO may be advantageous due to a likely more robust pharmacological profile.