Size-specific follicle selection improves mouse oocyte reproductive outcomes
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Updated: Apr 8, 2026
Production and Use of Customizable Agarose Molds for Scaffold-Free Mouse Ovarian Follicle Culture
Published on: October 24, 2025
Shuo Xiao1, Francesca E Duncan2, Lu Bai1
1Department of Obstetrics and GynecologyFeinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USACenter for Reproductive ScienceNorthwestern University, Evanston, Illinois 60208, USADepartment of Anatomy and Cell BiologyUniversity of Kansas Medical Center, Kansas City, Kansas 66160, USAMaster of Biotechnology ProgramNorthwestern University, Evanston, Illinois 60628, USADepartment of Biomedical EngineeringCollege of Engineering and Medical School, University of Michigan, Ann Arbor, Michigan 48109, USA Department of Obstetrics and GynecologyFeinberg School of Medicine, Northwestern University, Chicago, Illinois 60611, USACenter for Reproductive ScienceNorthwestern University, Evanston, Illinois 60208, USADepartment of Anatomy and Cell BiologyUniversity of Kansas Medical Center, Kansas City, Kansas 66160, USAMaster of Biotechnology ProgramNorthwestern University, Evanston, Illinois 60628, USADepartment of Biomedical EngineeringCollege of Engineering and Medical School, University of Michigan, Ann Arbor, Michigan 48109, USA.
Abstract:
Encapsulated in vitro follicle growth (eIVFG) has great potential to provide an additional fertility preservation option for young women and girls with cancer or other reproductive health threatening diseases. Currently, follicles are cultured for a defined period of time and analyzed as a cohort. However, follicle growth is not synchronous, and culturing follicles for insufficient or excessive times can result in compromised gamete quality. Our objective is to determine whether the selection of follicles based on size, rather than absolute culture time, better predict follicle maturity and oocyte quality. Multilayer secondary mouse follicles were isolated and encapsulated in 0.25% alginate. Follicles were cultured individually either for defined time periods or up to specific follicle diameter ranges, at which point several reproductive endpoints were analyzed. The metaphase II (MII) percentage after oocyte maturation on day 6 was the highest (85%) when follicles were cultured for specific days. However, if follicles were cultured to a terminal diameter of 300-350 μm irrespective of absolute time in culture, 93% of the oocytes reached MII. More than 90% of MII oocytes matured from follicles with diameters of 300-350 μm showed normal spindle morphology and chromosome alignment, 85% of oocytes showed two pronuclei after IVF, 81% developed into the two-cell embryo stage and 38% developed to the blastocyst stage, all significantly higher than the percentages in the other follicle size groups. Our study demonstrates that size-specific follicle selection can be used as a non-invasive marker to identify high-quality oocytes and improve reproductive outcomes during eIVFG.
