Microtubules in ovarian cell bridges identified as crucial for female fertility

Research led by Professor Masamitsu Sato from Waseda University has uncovered that microtubules in ovarian cell bridges are vital for female fertility. Published on July 2, 2026, the study reveals how disruptions in these structures can lead to infertility.

Significance of Microtubules in Ovarian Follicle Development

Female fertility hinges on the growth and maturation of eggs (oocytes) within ovarian follicles. Granulosa cells surrounding the oocyte provide essential nutrients and support. Communication occurs through transzonal projections (TZPs), traditionally viewed as actin-based structures. This study highlights the critical role of microtubules within TZPs.

Research conducted on Camsap3-knockout (KO) mice revealed that these mice were completely infertile, failing to ovulate even with normal estrous cycles. This indicates that hormonal factors were not responsible for the infertility.

Research Methods and Findings

The study utilized a combination of natural mating experiments and hormone-induced superovulation assays to evaluate fertility. Histological analysis and super-resolution microscopy were employed to visualize the structural components of TZPs, actin filaments, and microtubules.

• More than 80% of TZPs contained both microtubules and actin.
• The loss of Camsap3 resulted in disorganized microtubules and fewer TZPs.
• Specialized TNT-like TZPs, which transport large molecules, were also lost.

Dr. Mika Toya noted, “The study demonstrated that Camsap3 stabilizes microtubules within the TZP, revealing the molecular mechanism by which impaired communication between the oocyte and granulosa cells leads to infertility and follicular atresia.”

Implications for Infertility Diagnosis and Treatment

This groundbreaking discovery broadens the understanding of ovarian biology by identifying microtubules as essential for granulosa cell–oocyte communication. This knowledge may lead to new targets for diagnosing and treating infertility.

Furthermore, the insights gained could improve in vitro follicular culture systems used in reproductive technologies, enhancing the prospects for those facing fertility challenges.