Single-Cell Sequencing Identifies the Crucial Role of Mitochondrial Fission-Fusion Imbalance in Heart Failure Progression.

The heart grows in response to both pathological and physiological stimuli. Pathological hypertrophy often leads to cardiomyocyte loss and heart failure (HF), whereas physiological hypertrophy paradoxically protects the heart. Comparing these two types of hypertrophy can elucidate the differences and connections in their molecular mechanisms, which is pivotal for unraveling the pathogenesis of HF. This study compares pathological (TAC-induced) and physiological (exercise-induced) cardiac hypertrophy using single-cell and bulk transcriptomics. Mitochondrial fusion/fission imbalance emerged as a key dysregulated pathway in both models. An early increase in the fusion/fission ratio (2 weeks post-TAC) resembled exercise-induced remodeling, while a progressive decline at 5-8 weeks marked transition to pathological hypertrophy. By 11 weeks, suppressed fusion and increased fission led to heart failure. Downregulation of fusion genes (Mfn1, Mfn2, Opa1) and upregulation of fission genes (Fis1, Dnm1l) highlight mitochondrial dynamics as critical drivers of disease progression.