Follicular Fluid-Derived Extracellular Vesicles Influence on In Vitro Maturation of Equine Oocyte: Impact on Cumulus Cell Viability, Expansion and Transcriptome.

The study examines how extracellular vesicles (EVs) derived from follicular fluid impact the expansion, viability and genetic expression of cumulus cells, which play a pivotal role in the maturation of equine oocytes, or egg cells. Findings indicate that these EVs enhance cumulus expansion and influence gene expression related to key biological processes involved in oocyte maturation.

Study Aim and Process

• The goal of this study was to understand the effects of ffEVs (follicular fluid-derived extracellular vesicles) on the expansion, viability, and transcriptome (the total set of RNA molecules) of equine cumulus cells. Cumulus cells surround and nourish the egg cell during its development and maturation.
• The researchers subjected Cumulus-oocyte complexes (COCs) to in vitro maturation (IVM) in environments both with and without ffEVs. They observed the COCs for any changes in cumulus cell expansion and viability.
• After 12 hours of in vitro maturation, the cumulus cells were isolated, RNA was extracted, and a cDNA library was generated. This data was then used for transcriptome analysis with next-generation sequencing, a method that allows for rapid, high-throughput sequencing of genetic material.

Findings

• The ffEVs were internalized by the cumulus cells, as shown through confocal microscopy images.
• Supplementing the maturation environment with ffEVs significantly improved cumulus expansion in both compacted (Cp) and expanded (Ex) COCs.
• The viability or survival of cumulus cells increased in the Cp COCs but decreased in the Ex COCs when compared to the control groups.
• Transcriptome analysis showed a subtle but noticeable impact on cumulus cells’ RNA profiles. This means that the presence of ffEVs influenced the expression of certain genes within these cells.
• The genes with altered expression were linked to important processes such as MAPK and Wnt signaling, which have potential impact on the properties of cumulus cells and consequently, oocyte maturation.

Implications

• The results of this study highlight the potential role of ffEVs in enhancing the maturation of equine oocytes through their influence on cumulus cells. This insight could contribute to advancements in reproductive science and veterinary medicine, particularly for species like equines where in vitro maturation and fertilization practices are less established.
• Understanding the effects of ffEVs on cumulus expansion, cell viability, and gene expression could improve protocols for in vitro maturation of equine egg cells, making these practices more efficient and successful.