Exercise in adult zebrafish promotes ventricular cardiomyocyte proliferation in the regenerating heart

Exercise promotes a set of physiological adaptations known to provide long-term health benefits and it can play an important role in cardioprotection. However, the mechanisms underlying exercise-induced cardiac adaptation are not fully understood. In the present study, we examined cardiac adaptive responses to exercise training in the adult zebrafish and in the context of cardiac regeneration.We found that swimming-induced exercise increased cardiomyocyte proliferation and that this response was also found under regenerating conditions, when exercise was performed either prior to and after ventricular cryoinjury (CI). Exercise prior to CI resulted in a mild improvement in cardiac function and lesion recovery over the non-exercise condition.Transcriptomic profiling of regenerating ventricles in cryoinjured fish subjected to exercise revealed a differential regulation of genes related toregeneration as well as other biological processes potentially involved in the exercise response. Taken together, these results suggest that exercise constitutes a physiological stimulus thatmay help promote cardiomiogenic mechanisms of the vertebrate heart and that the zebrafish exercise model may be useful for evaluating the potential cardioprotective effects of exercise.