In the the November 10th online edition of Cell Transplantation, A. C. M. Assis et al. from the Federal Univ. of Minas Gerais (Belo Horizonte, Brazil) reported their study on the homing kinetics and body distribution of marrow-derived mesenchymal stem cells (BM-MSCs) intravenously administered into the tail veins of rats following a myocardial infarct. An adherent population of BM-MSCs were expanded and labeled (technetium-99m/DAPI) in vitro. Five million cells were infused into the infarcted rats. The phenotype of the BM-MSCs were CD90+, CD73+, CD54+ and CD45-. With gamma camera imaging, the investigators reported that the cells initially migrated to the lungs (approx. 70%) with a small fraction of the BM-MSCs found in the hearts, kidneys, spleen, and bladder. The number of cells migrating to the infarcted tissues was slightly higher than the control or sham groups (4.55% vs. 6.34%. However, 7 days post administration, the DAPI-labeled cells were still detected in the heart and only in the infarcted areas. The researchers concluded that "migration of systemically delivered BM-MSCs is time dependent and MI specifically increases BM-MSCs homing to injured hearts. However, the systemic delivery is limited by cell entrapment in the lungs."