Squeezing Ovarian Follicles: What Happens?

Researchers wanted to see what happens when they put pressure on tiny follicles from mice ovaries being grown in a lab dish. These follicles have baby egg cells inside, and sometimes these cells are grown outside the body to mature (we call this "in vitro maturation" or IVM). First, scientists took 12-day-old female mice and got some preantral follicles. Each follicle grew alone in a special liquid (Alpha Minimal Essential Medium) with oil on top, for 12 days. Then, they either left the follicles alone (the control group) or added some pressure (20 mmHg for 30 minutes) before IVM (the experiment group).After 24-48 hours, they checked how many oocytes (baby egg cells) reached a stage called metaphase II (MII). They also looked at how many helper cells (cumulus cells) were alive and if any were dying (apoptosis). The results were surprising! Pressure increased the number of MII oocytes but made the cumulus cells less alive and more likely to die. This shows that pressure can help egg cells mature but also hurts the supportive cells around them. Scientists think this is because pressure causes apoptosis in cumulus cells, which affects their communication with the oocytes. This connection between the cumulus cells and oocytes is important for egg cell maturation.