Assessment of Heart Microstructure

D ow nloaded from DOI: 10.1161/CIRCULATIONAHA.114.009221 2 Stem cell therapy has undergone a rapid translation from bench research to clinical trials as a promising approach for the regeneration of the injured myocardium1,2. Magnetic resonance imaging (MRI) plays a pivotal role in the assessment of stem cell therapy efficacy and elucidation of the mechanisms behind therapeutic effects3. One important aspect of stem cell therapy, however, remains missing: there are currently no non-invasive methods to evaluate the restoration of myocardial tissue microstructure. A study by Sosnovik et al.4 published in this issue of Circulation fills this gap and demonstrates the feasibility of evaluating the integrity and spatial organization of myofibers after cell therapy. The microstructure of the heart was histologically described more than 40 years ago in landmark studies by Streeter et al5. The myoarchitecture of a healthy heart is made up of thre