1. Department of Cell Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou 510515, P. R. China
2. Department of Pathology, Panyu Maternal and Child Care Service Centre of Guangzhou, Guangzhou 511499, P. R. China
3. Center for Reproductive Medicine, Department of Obstetrics and Gynecology, Nanfang Hospital, Southern Medical University, Guangzhou 510515, P. R. China
4. Reproductive center, Affiliated Shenzhen Maternity & Child Healthcare Hospital, Southern Medical University (Shenzhen Maternity & Child Healthcare Hospital), Shenzhen 518017, P. R. China