Follicle Fundamentals

An adolescent female has, on average, a staggering 350,000 eggs in her ovaries. These eggs live in fluid-filled sacs called follicles. Follicle degeneration occurs as a natural part of puberty but certain conditions that affect fertility, such as polycystic ovarian syndrome, cause too many to degenerate. Using fluorescence microscopy of developing mouse ovaries (pictured in a 3D reconstruction), here researchers confirm that as follicles (green) degenerate, follicle support cells called theca cells (magenta) increase in number. These cells produce androgens that contribute to the hormonal changes of puberty, and here the team also identified the genetic changes in theca cells underlying androgen production. This opens up new avenues of investigation for unpicking how and why follicle degeneration occurs in both health and disease.

Written by Lux Fatimathas

Lux Fatimathas

Writer

Having pursued science through a career in research, communications and publishing, she is currently a writer and editor for a healthcare marketing agency and also juggles freelance science writing.

• Image from work by Qi Yin and Allan C Spradling
• Howard Hughes Medical Institute and Department of Biosphere Sciences, Carnegie Institution for Science, Baltimore, MD, USA
• Image originally published with a Creative Commons Attribution 4.0 International (CC BY 4.0)
• Published in eLife, October 2025