1. Department of Center for Reproductive Medicine General Hospital Ningxia Medical University Ningxia 750004 China
2. Key Laboratory of Fertility Preservation and Maintenance of Ministry of Education Ningxia Medical University Ningxia 750004 China
3. Wake Forest University Health Sciences Institute for Regenerative Medicine Winston‐Salem NC 27157 USA
4. Department of Pathology Beijing Chao‐Yang Hospital Capital Medical University Beijing China