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, 5-year survival remains at 50%. Diseased cardiomyocytes have been demonstrated to exhibit telomeric shortening and through DNA damage response (DDR) 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 re-protection can restore nuclear-mitochondrial balance and offer a strategy for treating HF.

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 DDR. Telomeric repeat amplification protocol and quantitative fluorescence in situ hybridization assays were used to demonstrate loss of enzymatic function and localization of JV101. Using TPP1-knock out (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 ischaemia-reperfusion 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 signalling pathway driving HF. Molecularly, JV101 treatment silenced p53, rescued both mitochondrial biogenesis as well as prevented mitochondrial DNA N6-methyladenine (m6A) methylation.

Conclusion
Our work establishes the role of telomere-mitochondria DNA signalling during HF progression and provides proof-of-concept of telomere-targeting gene therapy to restore cardiac function.