Scientists 'rejuvenate' the aged eggs of mice — is it possible in people?

A microscope image of an oocyte, or egg cell, in an ovary. There's a round shape of tissue with another round dot in the middle (like a doughnut) — In an experiment, scientists showed that they can seemingly reverse aspects of aging in mouse egg cells, which are similar in structure to the human cells above.

(Image credit: Ed Reschke via Getty Images)

Aging egg cells can be rejuvenated when placed inside young follicles, a new study of mouse cells suggests.

The study could serve as proof-of-concept for future fertility treatments aimed at reversing aging in human egg cells — but much more research is needed to translate these findings to people.

As an oocyte matures, it undergoes multiple rounds of cell division before it's eventually released from the ovary during ovulation. This complex and energetic process is made possible by a follicle that surrounds the maturing oocyte and provides the energy and nutrients needed through thin filaments called tranzonal projections, or TZPs. Without these lifelines to the follicle, an oocyte cannot mature properly.

First author Haiyang Wang, a senior research fellow in the Li lab, designed a 3D system that enables scientists to implant oocytes from one mouse into the empty follicle of another. Wang first removes the oocyte and follicle — which are slightly larger than the width of a human hair — from the mouse ovary by hand using a microscope and tiny tools. When the oocyte is separated from its follicle and then joined to a new one, the TZPs reform and the connections between the follicle and oocyte are reestablished.

The researchers tried implanting oocytes from aging mice into young mouse follicles, finding that the older oocytes showed an uptick in TZP connections, comparable to much younger young egg cells. The eggs also showed improved rates of maturation and about half the rate of chromosomal abnormalities seen in unmodified cells. They also showed quadruple the rate of live births compared to baseline when they were fertilized and reimplanted into mice.

"This impressive study highlights the critical role of the follicular environment in oocyte quality," said Farners Amargant i Riera, a professor of obstetrics and gynecology at Washington University in St. Louis who was not involved in the study. "In addition, it shows that methods to rejuvenate this environment are critical to improve oocyte quality and extend fertility," she told Live Science in an email.

How could these results translate to the problem of age-related fertility? The team would first need to validate the same model and experiments in human cells. But eventually, Li and her colleagues think it would be possible to make a commercial cell line for follicle-forming cells that can be cultured alongside aging oocytes. This, in theory, could be a viable treatment to rejuvenate the old eggs and thus reduce the chance of miscarriage, they propose. Such a treatment would likely be used in the context of IVF.

Jennifer Zieba earned her PhD in human genetics at the University of California, Los Angeles. She is currently a project scientist in the orthopedic surgery department at UCLA where she works on identifying mutations and possible treatments for rare genetic musculoskeletal disorders. Jen enjoys teaching and communicating complex scientific concepts to a wide audience and is a freelance writer for multiple online publications.