Rete Ovarii study: Fluid transport toward the ovary observed in mice

Q: Is the Rete Ovarii found only in mice?

No. It has also been anatomically identified in humans, cattle, sheep, cats, dogs and primates. Its presence in different species does not, however, prove that the functions studied in mice occur in the same way in humans.

Q: Why was the Rete Ovarii previously considered functionless?

Although the structure had long been known, its physiological functions were poorly understood. It was therefore thought that it might be a remnant of embryonic development with no clear function in adulthood.

A study with Dilara N. Anbarcı as first author examined the possible functions of the Rete Ovarii, a structure connected to the ovary. The implications of the findings in mice for human fertility have yet to be demonstrated.

Rete Ovarii study: Fluid transport toward the ovary observed in mice

General News

Mirat Haber

12/11/2026 02:36

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Research by Dilara N. Anbarcı and colleagues suggested that the Rete Ovarii, a small network of ducts connected to the ovary, may not be a functionless remnant in adulthood. The study, reported by Milliyet, observed fluid moving from this structure toward the ovary in mice and identified proteins in the fluid within the structure. While the findings raise new questions about ovarian biology, no benefit for human fertility has been demonstrated.

Key findings of the study

The study was published in the journal eLife on 19 March 2025.
The researchers examined the three anatomical parts of the Rete Ovarii: the part inside the ovary, the part outside it and the part connecting the two.
In experiments with mice, labelled fluid was observed moving toward the ovary within approximately 15 minutes.
The precise effects of the identified proteins on ovarian function remain unclear.

Not a new organ, but a fresh look at a known structure

The Rete Ovarii has appeared in anatomical references since the 19th century. It consists of interconnected tubular structures associated particularly with the hilum of the ovary. Although it has long been known, its physiological functions had not been adequately explained, leading to the idea that it might be a functionless remnant of embryonic development in adulthood.

The researchers assessed this duct system in three parts: the portion inside the ovary is called the intraovarian rete, the portion outside it the extraovarian rete, and the portion joining the two the connecting rete. The examination showed that this interconnected structure persists into adulthood and that its cellular characteristics are more complex than previously assumed.

The study’s first author, Dilara N. Anbarcı, was joined by Jennifer McKey, Daniel S. Levic, Michel Bagnat and Blanche Capel. The research by the team affiliated with the Department of Cell Biology at Duke University Medical Center was published under a title that can be rendered as “Rediscovering the Rete Ovarii, an accessory secretory structure for the ovary.”

What did the labelled-fluid experiment show?

In mouse models, fluid containing fluorescently labelled dextran was injected into the Rete Ovarii duct. Approximately 15 minutes later, the fluid was observed moving toward the ovary. Injections in the reverse direction did not produce the same movement. This result supported the interpretation that the duct network may play a role in transporting fluid toward the ovary; it did not demonstrate that the same function exists in humans.

The experiment provided evidence that the structure may be more than an anatomical connection. However, fluid moving in a particular direction and the effects of that movement on ovarian health or fertility remain separate research questions.

Proteins and contact with surrounding tissues under investigation

The team’s examination was not limited to fluid movement. The detection of various proteins in the fluid within the Rete Ovarii suggested that the structure may have a secretory capacity. The researchers consider that these proteins could play a role in regulating the microenvironment around the ovary. However, their precise effects on ovarian function are not yet known.

Blood vessels, cells with smooth muscle characteristics, nerve extensions and structures associated with immune cells were also observed around the duct system. The close contact between nerve extensions and the Rete Ovarii was particularly notable. While this proximity offers a basis for investigating possible communication with surrounding tissues, how the relationship works or whether it affects ovarian function has not been established.

Is this a treatment advance for people hoping to have children?

No. The study did not show that the Rete Ovarii improves egg quality, preserves ovarian reserve or increases the chances of pregnancy. For people hoping to have children, the key distinction is between a biological function observed in mice and a proven treatment benefit in humans. The study’s findings should not be interpreted as a direct fertility treatment outcome.

Unanswered questions include how the structure interacts with hormones, its contribution to maintaining ovarian function and its possible effects on fertility. Further studies are needed to examine these functions in humans and clarify their effects on the ovarian microenvironment. The research’s current contribution is therefore not so much demonstrating a treatment benefit as opening the way for a more detailed investigation of the possible roles of a structure associated with the ovary.

Questions about the Rete Ovarii

Is the Rete Ovarii found only in mice?

No. It has also been anatomically described in humans, cattle, sheep, cats, dogs and primates. However, its presence in different species does not prove that the functions examined in mice occur in the same way in humans.

Why was the Rete Ovarii previously considered functionless?

Although the structure has long been known, its physiological roles had not been sufficiently clarified. It was therefore thought that it might be a remnant of embryonic development with no clear function in adulthood.