Rete Ovarii: The Unsung but CRUCIAL Player in Women's Reproductive Health

Researchers have known about a small structure known as the rete ovarii (RO), an ovary developmental vestige, for over a hundred years. But in recent decades, it has been dismissed and characterized as a vestigial nonfunctioning developmental remnant. A new eLife paper flips that presumption on its head and shows that the RO is not only functional, but potentially an essential component of ovary health and function.

The RO has three parts: one inside the ovary (intraovarian rete or IOR), one that connects it to the outside (connecting rete or CR), and one that is entirely outside the ovary (extraovarian rete or EOR). Under the help of high-tech imaging in mice, researchers observed as all three parts of the RO form and develop from prenatally through a short time after birth. The EOR is chock full of fluid, has hair-like cilia on its cells, and is lined with blood vessels, immune cells, and even nerves. All of which indicates that it simply can't be a useless vestige - it's a living, sensing, and even possibly signaling structure.

                                      

The EOR is highly integrated with its extra-ovarian environment suggesting multifaceted communication.

To learn it's function, scientists injected fluorescent fluid into the EOR and watched it move towards the ovary. This meant that the EOR is actively moving material into the ovary. When they looked at the fluid more carefully using a technique called mass spectrometry, they discovered that it contains secreted proteins, some of which have been discovered to influence ovary function. Included among them is IGFBP2, which controls levels of another hormone called IGF1 that acts on follicular growth - in the initial stage of egg development. Through the release of IGFBP2, the RO may perhaps control how the ovary responds to hormones, and thus coordinate the reproductive cycles.

Researchers also found that the RO does have genes and proteins that play roles in the SNARE complex, which is a component of the machinery cells use to secrete material. That conforms to the idea that the RO is an active secretory organ - like glands that secrete hormones or mucus. Finally, the close linkage of the RO with immune cells and nerves suggests that it can function as a sensor or messenger, responding to the body's changes and influencing the ovary's behavior.

In brief, this research redefines the RO as an active, functional organ which is most likely responsible for keeping the ovary fertile and healthy. The authors recommend that it be formally recognized as part of the female reproductive system - in addition to the ovaries, fallopian tubes, and uterus. By shedding light on the RO, this research opens new windows onto the comprehension of fertility, hormonal balance, and maybe even diseases like ovarian cancer. It reminds us that long-overlooked areas of the body may be harboring vast secrets.

REFERENCE:

Anbarci DN, McKey J, Levic DS, Bagnat M, Capel B. Rediscovering the rete ovarii, a secreting auxiliary structure to the ovary. eLife. 2025 Mar 19;13:RP96662.

IMAGE CREDITS:

• https://images.app.goo.gl/B24qDk1sGEyGPwFbA
• https://images.app.goo.gl/QY97gMUvF1AGnhE89