Abstract 4143841: Cardiomyocyte-specific PLCe1 knock-down attenuates Angiotensin II-induced cardiac hypertrophy.

Background: Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease. We have recently identified Phospholipase C epsilon 1 (PLCe1) to be upregulated in cardiomyocytes (CMs) from HCM patients. PLCe1 has been reported to play a critical role in developing cardiac hypertrophy and PLCe1 heart-specific genetic ablation in mice prevents hypertrophic growth following transaortic constriction. Aim: To further assess the therapeutic potential of PLCe1 modulation, we assessed whether PLCe1 knockdown can rescue agonist-induced cardiac hypertrophy both in vitro and in vivo. Methods: Cardiomyocyte hypertrophy was induced by endothelin 1 (ET1) stimulation in iPSC-derived CMs and primary neonatal mouse ventricular myocytes (NMVMs) followed by PLCe1 knockdown using siRNAs. For in vivo assessment, cardiac hypertrophy was induced in C57BL/6J wild type mice by implanting angiotensin II (Ang II) osmotic minipumps for 4 weeks. Adeno-associated virus serotype 9 carrying GFP-tagged shRNAs against PLCe1 (AAV9-shPLCe1) or GFP alone (AAV9-GFP; control) were delivered retro-orbitally on the day of the surgeries and 1 week after Ang II infusion. M-mode echocardiography was performed at baseline and weekly for 4 weeks. Results: PLCe1 silencing in either human iPSC-CMs or NMVMs treated with ET1 resulted in 25% reduction in cell size, 46% reduction in total protein synthesis, and 72% and 81% reduced expression of the hypertrophic markers NPPA and NPPB, respectively. To evaluate whether PLCe1 therapy can promote left ventricle hypertrophy regression, mice were infused with Ang II and subsequent delivery of AAV9-shPLCe1. Approximately 65% of the CMs were transduced within 3 days after AAV9-shPLCe1 delivery while the maximal transduction levels of 74% were observed after 1 week. We observed significant attenuation of the cardiac hypertrophic response represented by decreased wall thickness and preserved cardiac structure and function 1 week after PLCe1 modulation. Ongoing analysis of the later time points will allow us to better evaluate the salutary effects of PLCe1 therapy. Conclusion: Cardiomyocyte-specific PLCe1 knockdown attenuates Ang II-induced cardiac hypertrophy, highlighting PLCe1 as a potential target for HCM.