1. 1Department of Urology, The Third Hospital of Peking University, Beijing 100191, P.R. China
2. Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Key Laboratory of Assisted Reproduction, Ministry of Education, Peking University Third Hospital, Beijing 100191, P.R. China
3. Department of Urology, Rizhao People's Hospital, Rizhao, Shandong 276500, P.R. China
4. Key Laboratory of Male Reproduction and Genetics, National Health and Family Planning Commission, Family Planning Research Institute of Guangdong Province, Guangzhou, Guangdong 510600, P.R. China