1. a Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China
2. b Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China
3. c Tissue Engineering Program, Life Sciences Institute, National University of Singapore, 117510 Singapore
4. d Department of Veterinary Surgery, College of Veterinary Medicine, Chungbuk National University, Cheongju 361763, South Korea
5. e Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China
6. f Department of Biomedical Engineering, College of Engineering, Peking University, Beijing 100871, P. R. China; Center for Biomaterials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871, P. R. China