1. Samsung Biomedical Research Institute, Samsung Medical Center, Seoul, Korea
2. Department of Neurosurgery, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea
3. Department of Anatomy and Cell Biology, Sungkyunkwan University School of Medicine, Seoul, Korea
4. Department of Health Sciences and Technology, SAIHST, Sungkyunkwan University, Seoul, Korea
5. Department of Stem Cell Biology and Regenerative Medicine, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA