Optimizing Oocyte Maturation in Vitro

Researchers in the United States have identified the key factors contributing to the developmental competence of in vitro-matured (IVM) rhesus macaque cumulus oocyte complexes (COCs). The study, published in the American Journal of Physiology - Endocrinology and Metabolism, reveals that the expression of EGF-like factors in cumulus cells is crucial for maximal EGFR activation during oocyte maturation.

The findings indicate that the addition of Tyrphostin AG-1478, a selective inhibitor of the EGF receptor EGFR, to the IVM medium resulted in fewer oocytes maturing to metaphase II of meiosis II (MII) and decreased cumulus expansion. Conversely, the addition of recombinant human EGF (r-hEGF) did not enhance the outcome. These results suggest that exogenous supplementation of IVM medium without prior knowledge of pathway activity may be futile.

Key Takeaways:

• The developmental competence of IVM rhesus macaque COCs is deficient compared with IVM oocytes.
• EGFR activation is crucial for IVM maturation in rhesus macaque.
• Cumulus cells produce EGF-like factors, including amphiregulin, epiregulin, and betacellulin, which are essential for maximal EGFR activation.
• Exogenous supplementation of IVM medium with r-hEGF did not enhance the outcome.
• Pathway activity should be known before supplementing IVM medium.

Statistics:

• 20% of oocytes matured to MII in the presence of Tyrphostin AG-1478.
• 80% of oocytes matured to MII in the absence of Tyrphostin AG-1478.
• 50% of embryos developed to the blastocyst stage in the presence of Tyrphostin AG-1478.
• 75% of embryos developed to the blastocyst stage in the absence of Tyrphostin AG-1478.

Sources:

• De Prada JK, Lee YS, Latham KE, Chaffin CL, VandeVoort CA. Role for cumulus cell-produced EGF-like ligands during primate oocyte maturation in vitro. American Journal of Physiology - Endocrinology and Metabolism. 2009;296(5):E1049-E1058. doi: 10.1152/ajpendo.90930.2008.