DWORF Gene Therapy Improves Cardiac Calcium Handling and Mitochondrial Function

BACKGROUND: Calcium (Ca 2+ ) dysregulation is a hallmark of heart failure, impairing excitation-contraction coupling and contributing to pathological remodeling. The SERCA2a (sarco/endoplasmic reticulum Ca 2+ ATPase isoform 2a) mediates Ca 2+ reuptake into the sarcoplasmic reticulum (SR) during diastole, but its activity declines in failing hearts. DWORF (dwarf open reading frame), a newly identified cardiac microprotein, enhances SERCA2a activity and improves cardiomyocyte Ca 2+ cycling and contractility. SR Ca 2+ release also influences mitochondrial metabolism and ATP production. Here, we investigated whether DWORF overexpression improves SR Ca 2+ handling, augments mitochondrial Ca 2+ signaling, and protects against heart failure progression. METHODS: Transgenic and adeno-associated virus approaches were used to overexpress DWORF in the heart. Mice underwent transverse aortic constriction to model pressure overload–induced heart failure. Cardiac function, mitochondrial metabolism, SR Ca 2+ uptake, and remodeling were assessed. RESULTS: Mitochondria from DWORF transgenic hearts displayed increased basal respiration, maximal respiration, and spare respiratory capacity, correlating with enhanced mitochondrial Ca 2+ uptake kinetics. Western blot analysis showed elevated levels of active PDH (pyruvate dehydrogenase) and mitochondrial Ca 2+ uniporter expression in DWORF transgenic hearts, supporting a role for DWORF in Ca 2+ -driven metabolic regulation. Similarly, MyoAAV-mediated DWORF overexpression enhanced mitochondrial respiration and increased levels of active PDH in adult mice. Following TAC, MyoAAV-DWORF–treated mice maintained higher left ventricular function and were protected from further deterioration compared with controls. This benefit was observed when DWORF gene therapy was delivered preventively at the time of pressure overload or after heart failure was already established. DWORF gene therapy also attenuated remodeling, with lower heart weight and lung weight-to-tibia length ratios. Seahorse analysis confirmed sustained mitochondrial improvements in both treatment paradigms. CONCLUSIONS: DWORF overexpression enhances SR Ca 2+ dynamics, improves mitochondrial energetics, and attenuates pathological remodeling and heart failure progression in response to pressure overload. These findings support DWORF as a promising therapeutic target for heart failure.