PTEN and heart failure: In fact, the importance of exosomal microRNA-21-5p was further highlighted by Qiao et al. (2019) when they showed cardiac stromal cell-derived exosomal microRNA-21-5p is reduced in heart failure patients, thus impairing regenerative potential via the PTEN/Akt pathway, the same pathway we found to be modulated by hMSC exosomal microRNA-21-5p.