Viscosity of fluid in female reproductive tract may influence fertility

In a study providing important new insights into female reproductive development and fertility, researchers have revealed how the thickness of the fluid surrounding the egg can impact the cellular structure of the fallopian tube and how the egg or embryo moves along it.

Published in Nature CommunicationsThe Monash University study sheds light on how changes in the ‘viscosity’ of fluid in the female reproductive tract influence how cells are modified to facilitate the transport of eggs for fertilisation.

Led by Melati Abdul Halim, a doctoral candidate in the Department of Mechanical and Aerospace Engineering, the study highlights the potential for new treatments that could mimic or modify the natural adhesion of fluids in the reproductive system, offering hope for advances in fertility therapies.

“Imagine the difference between walking in water and in thick mud. That’s what the tiny cells of the female reproductive tract feel, where the viscosity of the liquid can vary,” Halim explains.

“When the fluid is thicker, the extra resistance causes cells to change their behavior. Some begin to grow tiny hair-like structures called cilia, which help move things like eggs along the reproductive tract. The thicker the fluid, the more cilia these cells produce and the more coordinated their movements become. This coordinated beating pattern may facilitate the formation of metachronal waves, which are essential for transporting eggs and embryos.”

Dr Reza Nosrati, lead and corresponding author, said the findings suggest that the natural adhesion of fluids in our bodies could play a key role in processes such as fertilisation.

“The study suggests that high viscosity at certain stages of the menstrual cycle may be a natural mechanism to enhance cilia formation and coordination, thereby facilitating fertilization. This important aspect of natural fertilization and the role of higher viscosity fluid in the reproductive tract may require more careful evaluation in the context of infertility diagnosis and assisted reproduction practices,” said Dr. Nosrati.

“This provides insight into how the viscosity (thickness, stickiness) of extracellular fluid influences the behavior of epithelial cells lining the fallopian tubes and could be key to understanding and potentially treating fertility problems.”