1. Reproductive Medicine Center, The Second Hospital, Cheeloo College of Medicine, Shandong University, Jinan, Shandong 250000, P.R. China
2. College of Animal Science and Veterinary Medicine, Shandong Agricultural University, Tai'an, Shandong 271018, P.R. China
3. Reproductive Medicine Center, Tongji Medical College, Huazhong University of Science and Technology, Wuhan Tongji Reproductive Medicine Hospital, Wuhan, Hubei 430010, P.R. China