Reply letter to Dr. Xu et al. on role of circulating endothelial progenitor cells in the reparative mechanisms of stable ischemic myocardium. (1st June 2018) - Morrone, D.; Felice, F.; Scatena, C.; De Martino, A.; Picoi, M.L.E.; Mancini, N.; Blasi, S.; Menicagli, M.; Di Stefano, R.; Bortolotti, U.; Naccarato, A.G.; Balbarini, A.