1 Beijing Rehabilitation Hospital, Capital Medical University, Beijing 100144, China.
2 Center of Excellence for Aging & Brain Repair, Department of Neurosurgery & Brain Repair, Morsani College of Medicine, University of South Florida, Tampa, FL 33612, USA.
3 Intensive Experimental CNS Injury and Repair, Department of Surgical Sciences, University Hospital, Uppsala University, Uppsala S-751 85, Sweden.