1. Department of Orthopedic Surgery, Washington University School of Medicine, St. Louis, MO 63110, USA.
2. Shriners Hospitals for Children—Saint Louis, St. Louis, MO 63110, USA.
3. Center of Regenerative Medicine, Washington University School of Medicine, St. Louis, MO 63110, USA.
4. Department of Biomedical Engineering, Washington University, St. Louis, MO 63105, USA.
5. Department of Orthopaedic Surgery, Duke University School of Medicine, Durham, NC 27710, USA.
6. Department of Biology, Duke University, Durham, NC 27708, USA.
7. Department of Mechanical Engineering and Materials Science, Washington University, St. Louis, MO 63105, USA.
8. Department of Pathology and Immunology, Washington University School of Medicine, St. Louis, MO 63110, USA.
9. Department of Neurology, Duke University School of Medicine, Durham, NC 27710, USA.
10. Department of Pathology, Duke University School of Medicine, Durham, NC 27710, USA.