Telomere recapping prevents pathogenic telomere-to-mitochondrial DNA communication in heart failure

AIMS: Heart failure (HF) remains a highly prevalent condition with current therapeutic options, five-year survival remains at fifty percent. Diseased cardiomyocytes have been demonstrated to exhibit telomeric shortening and through DNA damage response activation leads to mitochondria dysfunction. How the orchestration between nuclear and mitochondrial transcription systems regulates myocardial function remains elusive. The aim of this study is to test if myocardial telomere reprotection can restore nuclear-mitochondrial balance and offer a strategy for treating heart failure. METHODS AND RESULTS: To re-protect telomeric ends, we designed an adeno-associated virus 9 (AAV9)-mediated delivery system carrying modified human telomerase protein (modhTERTY707F, D868A, JV101) under cardiac troponin T promoter regulation. The modhTERT is engineered to be catalytic inactive, nuclear localized, and bind to telomeric ends to turn off DNA damage response. Telomeric repeat amplification protocol (TRAP) and quantitative fluorescence in situ hybridization (Q-FISH) assays were used to demonstrate loss of enzymatic function and localization of JV101. Using TPP1-knockout (TPP1KO) U2OS (telomerase-deficient) and human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs) lines generated by CRISPR/Cas9 genome editing, we demonstrated that JV101 is recruited by TPP1 through TEL patch to telomeric ends. JV101 restored cardiac function in both Ang II infusion and myocardial ischemia-reperfusion (I/R) HF models and in Ang II-stressed hiPSC-CMs. RNA-Seq data suggests that uncapped telomeres activated p53 and using myocardial p53 deficient (p53cKO) mice we demonstrate that telomere-p53-mitochondrial dysfunction is the main signaling pathway driving HF. Molecularly, JV101 treatment silenced p53, rescued both mitochondrial biogenesis as well as prevented mitochondrial DNA N6-methyladenine (m6A) methylation. CONCLUSIONS: Our work establishes the role of telomere-mitochondria DNA signaling during HF progression and provides proof-of-concept of telomere-targeting gene therapy to restore cardiac function.