1. Department of Pediatrics, University of California—San Diego, La Jolla, CA, USA
2. Sanford Consortium for Regenerative Medicine, University of California—San Diego, La Jolla, CA, USA
3. Department of Orthopaedic Surgery, University of California—San Diego, La Jolla, CA, USA
4. Department of Bioengineering, University of California—San Diego, La Jolla, CA, USA
5. Research Division, VA San Diego Healthcare System, San Diego, CA, USA