Follicular & Ampullary Fluid Vesicles Boost Egg Quality and Fertilization

Jenn Hoskins
9th June, 2025

Follicular & Ampullary Fluid Vesicles Boost Egg Quality and Fertilization

Characterization of the treatment supplements confirmed the successful isolation of extracellular vesicles from follicular and ampullary fluids, revealing their expected morphology via transmission electron microscopy (A) and the presence of key marker proteins via western blot analysis (B).

Image adapted from: Pakniyat et al. / CC BY (Source)

Key Findings

  • At Shiraz and Ferdowsi Universities, scientists found that adding tiny particles from cow reproductive fluids to lab media improved egg cell maturation and fertilization
  • Egg cells treated in two phases with these particles showed enhanced gene activity, stronger mitochondria, and better lipid balance, indicating higher quality
The current study[1] from Shiraz University; Ferdowsi University of Mashhad; and Shiraz University of Medical Sciences explores how tiny particles called extracellular vesicles (EVs), isolated from fluids within the cow’s reproductive system, can improve the quality of oocytes (immature egg cells) in a laboratory setting. This research is part of an ongoing effort to enhance in vitro maturation (IVM) techniques, which help support fertilization and early embryo development outside the animal’s body. Improving these methods may lead to more reliable outcomes in animal breeding and potentially inform human reproductive medicine. In this study, researchers collected follicular fluid from preovulatory follicles—follicles that are ready to release an egg—and ampullary fluid from cows in early metestrus (a phase shortly after ovulation). These fluids are naturally rich in EVs, which are small packages that cells release to send signals or transfer materials to other cells. By isolating these EVs from follicular and ampullary fluid, the investigators were able to add them to the maturation media where oocytes mature in vitro. The oocytes were divided into four groups. The control group did not receive any EVs. The second group, labeled FFEV, was exposed to 40 μg/ml of follicular fluid EVs for the first 18 hours of culture. The third group, called FFAFEV, received the same follicular EV treatment for 18 hours followed by an exposure to 3.4 μg/ml of ampullary fluid EVs for the final 4.5 hours. The fourth group, AFEV, was given only 3.4 μg/ml of ampullary fluid EVs during the final 4.5 hours of the culture period. After a 22.5-hour incubation, the oocytes were analyzed for nuclear maturation (the process by which the nucleus of the cell prepares for fertilization), gene expression, and biochemical markers using Raman microspectroscopy—a technique that identifies molecular characteristics based on how light scatters off a sample. The results showed significantly improved maturation and fertilization rates in all the groups that received EVs compared to the control group. In addition, the EV-treated oocytes demonstrated higher expression of genes associated with oocyte quality and developmental competence, such as TNFAIP6, HAS2, and GDF9. These genes play roles in processes like cell expansion, structural organization, and the overall readiness of the cell for fertilization. Of particular note, the FFAFEV group—receiving a combination of follicular and ampullary EVs—showed favorable changes in cell metabolism. Raman microspectroscopy revealed higher levels of mitochondria (indicated by a peak at 1602 cm⁻¹), more unsaturated lipids (at 1655 cm⁻¹), and a balanced ratio of phenylalanine to carbohydrates (1002/1037), which serves as a marker for oocyte quality. This group also had a lower concentration of saturated lipids (at 2883 cm⁻¹) compared to the control, suggesting a healthier lipid profile. These findings build upon, and in some cases extend, earlier research in the field. For instance, previous studies have demonstrated that co-culture systems and supplementation with reproductive fluids can improve embryo development and quality. One study[2] showed that co-culturing bovine oocytes with epithelial cells from the oviduct increased blastocyst yield and quality, by affecting cell counts and gene expression. Another study[3] found that exposing porcine oocytes to bovine oviductal fluid for a brief period before fertilization enhanced both cleavage and blastocyst development, and beneficially modified gene expression related to apoptosis and mitochondrial function. A separate investigation[4] demonstrated that adding bovine follicular fluid (FF) during oocyte maturation improved important markers such as total cell numbers and cumulus cell expansion, ultimately leading to better blastocyst quality. The current study ties these earlier observations together by directly supplementing the maturation media with specific EVs rather than relying solely on whole fluids or co-culture systems. EVs are thought to work as concentrated messengers, carrying molecular signals that trigger beneficial cellular responses. By using EVs from both follicular and ampullary sources, the researchers could mimic some of the natural conditions present during oocyte development within the animal’s reproductive tract. This strategy appears to enhance intracellular processes, promoting mitochondrial activity and improving lipid homeostasis. Both of these factors are critical because mitochondria provide the energy needed during maturation and early development, while lipid composition is important for cell membrane integrity and signaling. The study’s design emphasizes a stepwise exposure to EVs at distinct time points during oocyte maturation. The initial prolonged exposure to follicular EVs may help prime the oocytes, ensuring that critical genes necessary for maturation are activated. The later introduction of ampullary EVs further refines this process, possibly by optimizing the oocyte’s metabolic state just before the final stages of maturation and fertilization. This two-phase treatment regimen reflects the natural progression of molecular signals that an oocyte would experience in vivo, serving as a practical enhancement to current in vitro protocols. Overall, this research provides strong evidence that supplementing IVM media with EVs from follicular and ampullary fluids can enhance both the maturation and fertilization of bovine oocytes. The study not only complements previous findings from research on co-culture systems and fluid supplementation[2][3][4] but also suggests that a targeted use of EVs offers additional benefits. The improvements in gene expression and the biochemical profiles of the oocytes indicate that EVs could help improve the early stages of embryo development, offering potential for more efficient and successful outcomes in reproductive technologies.

AgricultureBiotechAnimal Science

References

Main Study

1) The effect of follicular and ampullary fluid extracellular vesicles on bovine oocyte competence and in vitro fertilization rates

Published 6th June, 2025

https://doi.org/10.1371/journal.pone.0325268

Related Studies

2) Frozen-thawed ampullary cell monolayer improves bovine embryo in vitro development and quality.

https://doi.org/10.1017/S0967199419000388

3) Effects of oviductal fluid on the development, quality, and gene expression of porcine blastocysts produced in vitro.

https://doi.org/10.1530/REP-08-0405

4) Follicular fluid during individual oocyte maturation enhances cumulus expansion and improves embryo development and quality in a dose-specific manner.

https://doi.org/10.1016/j.theriogenology.2021.02.016


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