A Novel Pkp2 Mouse Model Of Genetic Arrhythmogenic Right Ventricular Cardiomyopathy And Its Rescue By Gene Therapy

Background: Arrhythmogenic right ventricular cardiomyopathy (ARVC) is an inherited cardiac disorder in which cardiomyocytes lack structural integrity and signaling is compromised resulting in the disruption of normal rhythms and formation of fibrosis. Patients suffer from arrhythmia and are at increased risk of sudden cardiac death and heart failure. Previous work has demonstrated that heterozygous mutations in the desmosomal gene, plakophilin-2 ( PKP2 ), are the most common cause of ARVC. Our objective was to investigate the mechanisms of ARVC development and test a potential ARVC gene therapy strategy using a novel mouse model of Pkp2. Methods: A knock-in (KI) mouse model with a point mutation corresponding to human PKP2 ( PKP2 c.2146-1G>C or Pkp2 KI) was generated via CRISPR/Cas9 technology. High fat diet (HFD) was used to induce the ARVC phenotype in the Pkp2 KI heterozygous (het) mice. The Pkp2 KI het mice were crossed with a cardiac-specific Pkp2 cKO (αMHC-Cre ERT ) mouse to generate a tamoxifen inducible model (KIxKO). Cardiac function was assessed by echocardiography and arrhythmia burden by EKG. The KIxKO animals received AAV:PKP2 via retro-orbital injection. Results: Pkp2 KI het animals with normal chow had slow and mild ARVC development, and 50% decrease in PKP2 protein expression, with right ventricle (RV) dilation not occurring until animals were 9 months old. Induction with HFD from 8 weeks hastened and worsened the RV dilation. In contrast, the KIxKO mice exhibited >90% decrease in PKP2 protein expression and a correspondingly severe ARVC phenotype starting from 3 weeks after Tamoxifen induction. This included a high arrhythmia burden and both RV area dilation and decreased ejection fraction, indicating the mice eventually progressed to biventricular heart failure. This resulted in 100% mortality in KIxKO animals by 9 weeks post-tamoxifen induction. A single dose of AAV:PKP2 gene therapy (6E13 vg/kg) maintained ejection fraction, prevented ARVC development and improved survival in the KIxKO mice after 9 weeks of treatment. Conclusion: The current results demonstrated that AAV:PKP2 gene therapy may be a promising therapeutic approach to treat ARVC patients with PKP2 mutations resulting in haploinsufficiency.