1. Department of Human Anatomy and Histoembryology, School of Basic Medical Sciences, Ningxia Medical University, Yinchuan, China;
2. Department of physiology, School of Basic Medical Sciences, Chengde Medical University, Chengde, China;
3. Department of Human Anatomy, School of Basic Medical Sciences, Chengde Medical University, Chengde, China;
4. Department of Human Anatomy, School of Basic Medical Sciences, North China University of Science and Technology, Tangshan, China;
5. Department of Pathophysiology, School of Basic Medical Sciences, Chengde Medical University, Chengde, China;
6. Key Laboratory of Fertility Preservation and Maintenance of Ministry of Education, Key Laboratory of Reproduction and Genetics of Ningxia Hui Autonomous Region, Ningxia Medical University, Yinchuan, China;
7. Center for Reproductive Biology and Health, School of Agricultural Sciences, The Pennsylvania State University, University Park, USA