Advanced imaging and multi‐omics to characterize cardiomyocyte ageing and its electrocardiographic imprint in PKP2 arrhythmogenic cardiomyopathy

Age is the greatest risk factor for mortality and morbidity. We previously reported premature ageing in PKP2 arrhythmogenic cardiomyopathy (PKP2‐ACM). However, depiction of cardiomyocyte molecular anatomy in premature ageing remains incomplete. Furthermore, the relationship between myocyte premature ageing and the molecular components of electrical homeostasis in PKP2‐deficient hearts remains understudied. Therefore, we aimed to identify molecular anatomical changes of premature ageing in PKP2‐deficient adult cardiomyocytes, the corresponding gene cohort and its imprint in the human electrocardiogram (ECG). We used a murine model of cardiomyocyte‐specific PKP2 knockout. Molecular anatomy was resolved by expansion and structured illumination microscopy, allowing 3D‐nanometric visualization, and by serial block‐face scanning electron microscopy. We used omics databases to distill a subset of genes related to ageing and PKP2 deficiency containing single nucleotide polymorphisms (SNPs) with an ECG‐relevant genomic signature. We found increased DNA damage and reduced abundance of transcriptionally repressed heterochromatin at the lamin‐associated domain (LAD), and disrupted mitochondria ultrastructure at the intercalated disc. Genes dysregulated in ageing hearts and PKP2‐deficient cells were distilled to identify those in the PKP2 human left ventricular gene network (by GTEx) that contain SNPs with an imprint in the human ECG (based on ECG GWAS). These findings indicate that in PKP2 deficiency, transcriptionally repressed heterochromatin in the LAD is vulnerable to damage, and erasing of otherwise transcriptionally inaccessible genomic regions, consistent with premature cellular ageing and transcriptional reprogramming. Multi‐omics analysis indicates that reduced PKP2 expression accelerates cardiomyocyte ageing, and the age‐related gene network contributes to dysfunction of cell metabolism and arrhythmia risk in PKP2‐ACM. image Key points We used advanced imaging technology to unveil DNA damage and loss of heterochromatin architecture in the lamin‐associated domain (LAD), and mitochondrial remodelling at the intercalated disc, as features of premature myocyte ageing in adult PKP2‐deficient murine cardiomyocytes. Multi‐omics analysis identified a network of genes dysregulated by ageing and by PKP2 deficiency. Cross‐correlation with the ECG GWAS database found a subset of single nucleotide polymorphisms with an imprint in the human electrocardiogram. These results provide novel insight into the mechanisms of transcriptional remodelling and take an initial step toward a better understanding of the oligogenic bases of arrhythmia risk in PKP2‐deficient hearts.