1. Institute of Biomedical Engineering, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, China.
2. Department of Anatomy and Histology, School of Basic Medical Sciences, Peking University, Beijing, China.
3. Department of Histology and Embryology, West China School of Basic Medical Sciences & Forensic Medicine, Sichuan University, Chengdu, China.