1. Department of Urology, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong 510515, P.R. China
2. Department of Urology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong 510630, P.R. China
3. Center for Reproductive Medicine, The Guangdong Armed Police Hospital, The Guangzhou Medical University, Guangzhou, Guangdong 510507, P.R. China