[1] Massachusetts Gen Hosp, Ctr Regenerat Med, Boston, MA 02114 USA
[2] Harvard Univ, Sch Med, Boston, MA 02115 USA
[3] Harvard Stem Cell Inst, Cambridge, MA 02138 USA
[4] Stanford Univ, Sch Med, Paul F Glenn Labs Biol Aging, Stanford, CA 94305 USA
[5] Stanford Univ, Sch Med, Dept Neurol & Neurol Sci, Stanford, CA 94305 USA
[6] Vet Affairs Palo Alto Hlth Care Syst, Neurol Serv, Palo Alto, CA 94304 USA
[7] Vet Affairs Palo Alto Hlth Care Syst, Rehabil Res & Dev Ctr Excellence, Palo Alto, CA 94304 USA