Fertilization can offset age-related egg changes in mice
Eggs from aged mice fertilized in the lab formed early embryos at rates comparable to young controls and developed without detectable impairment in young recipients.
Limit: Embryos were transferred into young oviducts; development in aged recipients was not measured
Edited by Boris Djordjevic · AgingResearch.News
In an experiment with eggs from aged and young mice, researchers used the same young-donor sperm preparation to fertilize both groups in the lab. This kept the fertilization environment constant and removed variation between sperm donors. Aged eggs formed blastocysts, an early embryo stage, at rates comparable to young controls. After transfer to young oviducts—the tubes that carry eggs toward the uterus—embryos showed no detectable impairment in development through embryonic day 18.5.
Age-related protein differences in eggs did not persist unchanged in blastocysts. For some proteins, especially those depleted in aged eggs, the direction of the age difference reversed. Comparisons with eggs activated without fertilization suggested that fertilization, rather than cell division alone, drove these protein changes.
Why it matters
Age-related declines in egg quality are often assumed to carry over into embryos. This work addresses whether those limits lie within the egg or depend on its reproductive environment.
Caveats
The embryo-transfer results came from young recipients and concerned development through embryonic day 18.5; they do not establish the same effects in people or aged recipients. This preprint has not been peer-reviewed.
Where the evidence stands
Embryo transfer
- 1 lab in 1 country
- Funders: Biotechnology and Biological Sciences Research Council and 4 more
In vitro fertilization
- 2 independent labs in 1 country
- Funders: National Institute of Child Health and Human Development and 3 more
- Embryo transfer
- In vitro fertilization
- PARTHENOGENETIC
- Proteostasis
- Blastocyst cell-lineage composition
- Mice
The paper
Max Planck Institute for Molecular Biomedicine
bioRxiv, Nov 2, 2026, Open access, CC BY, Preprint, not peer-reviewed
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