1. Center for Regenerative Medicine, University of Edinburgh, Edinburgh, UK
2. Center for Cardiovascular Science, University of Edinburgh, Edinburgh, UK
3. Department of Pathology, Johns Hopkins University, Baltimore, MD, USA
4. INSERM, IRFAC/UMR-S1113, Strasbourg, France
5. Orthopaedic Hospital Research Center and Broad Stem Cell Research Center, University of California, Los Angeles, Los Angeles, CA, USA