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Published on: October 24, 2025
Size-specific follicle selection improves mouse oocyte reproductive outcomes
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.
Encapsulated in vitro follicle growth (eIVFG) can improve fertility preservation. Selecting follicles by size, not just culture time, better predicts oocyte quality and enhances reproductive outcomes in eIVFG.
Area of Science:
- Reproductive Biology
- Developmental Biology
- Cell Biology
Background:
- Encapsulated in vitro follicle growth (eIVFG) offers fertility preservation for young women facing diseases that threaten reproductive health.
- Current eIVFG methods analyze follicles as a cohort after a fixed culture duration, which can compromise oocyte quality due to asynchronous follicle development.
Purpose of the Study:
- To investigate if follicle size, rather than fixed culture time, is a better predictor of follicle maturity and oocyte quality in eIVFG.
- To optimize eIVFG protocols for improved fertility preservation outcomes.
Main Methods:
- Multilayer secondary mouse follicles were isolated and encapsulated in alginate.
- Follicles were cultured individually, either for set time periods or until reaching specific diameter ranges (300-350 μm).
- Reproductive endpoints, including oocyte maturation (MII stage), spindle morphology, fertilization, and embryo development, were analyzed.
Main Results:
- Culturing follicles to a diameter of 300-350 μm resulted in a 93% MII oocyte maturation rate, higher than fixed-time cultures (85%).
- Oocytes from size-selected follicles (300-350 μm) showed significantly higher rates of normal spindle morphology, two-pronuclei formation after IVF (85%), two-cell embryo development (81%), and blastocyst development (38%).
Conclusions:
- Follicle size is a reliable non-invasive marker for identifying high-quality oocytes in eIVFG.
- Size-specific follicle selection can significantly improve reproductive outcomes in eIVFG, offering a more precise approach to fertility preservation.
