1. a Reproductive Centre, Sixth Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guang Dong, People's Republic of China
2. b Wake Forest Institute of Regenerative Medicine
3. c Department of Urology First Affiliated Hospital of Sun Yat-Sen University, Guangzhou, Guang Dong, People's Republic of China
4. d Department of Urology Shanghai Tenth People's Hospital, Tongji University School of Medicine, Shanghai, People's Republic of China
5. e Department of Urology The Second Affiliated Hospital of Nanchang University, Nanchang, People's Republic of China
6. f School of Dentistry, Ann Arbor, Michigan, USA
7. g Department of Anesthesiology, Wake Forest School of Medicine, Winston-Salem, North Carolina, USA