Magnetic Resonance Imaging of the Regenerating Neonatal Mouse Heart

We present longitudinal magnetic resonance imaging (MRI) of neonatal mouse hearts during the first three weeks following coronary artery ligation to mimic heart attack. We confirm heart regeneration in individual animals injured on post-natal day 1 (P1) while those injured on P7 show the adult response of fibrosis, scarring and impaired heart performance. We document heart growth and development of the principal functional cardiac parameters, and also remodeling during tissue regeneration as compared to fibrosis when imaging repeatedly up to 21 days after myocardial infarction (MI). We reveal compensatory changes in cardiac function with the restoration of tissue and resolution of injury for the P1 cohort and sustained injury responses for the P7 cohort. This study resolves the controversy surrounding neonatal mouse heart regeneration and establishes a functional platform for live capture of the regenerative process and for the future testing of genetic or therapeutic interventions.