1. From the Department of Biology, San Diego State University Heart Institute and the Integrated Regenerative Research Institute, CA (K.M.B., B.J.W., F.F., F.K., M.A.S.); Institute for Cardiovascular Regeneration, Center of Molecular Medicine, Frankfurt, Germany (S.D.); and Department of Cardiology, Hospital General Universitario Gregorio Marañón, Instituto de Investigación Sanitaria Gregorio Marañón (IiSGM), CIBERCV and Universidad Complutense de Madrid, Spain (F.F.-A.).