Fertility professionals at Yale School of Medicine that studied human eggs for in vitro fertilization have found genetic markers which indicate the egg´s maturity. Pasquale Patrizio, MD, professor of obstetrics and gynecology and director of the Yale Fertility Center and Dagan Wells, from the University of Oxford, UK, have found significant differences in genes at different stages of the eggs´ development.

“Why so few eggs produced live births and can we one day identify the best one among the many that look alike?” were the two main questions Patrizio is looking to answer. He said that in order to do that, understanding the genetic make up of eggs is crucial.

Patrizio and Wells led a series of analysis of gene expression in immature eggs, mature ones developed in culture in the laboratory and others that developed naturally in the ovary within their own egg-shell.

In eggs that matured in the laboratory, as opposed to eggs that were mature at the time of harvesting, had less gene activity than normal. Furthermore, they compiled a list of mRNA-mediated gene expression changes that take place as the eggs matured.

Researchers say that the study is important for many reasons. First it provides the most comprehensive and detailed information about the genetic make-up of human eggs at different stages of maturity. Second, it provides gene expression profiles that will make it possible to identify eggs with exceptional developmental capacity. Third, it reveals that eggs harvested while still immature and then matured in lab dishes, a practice known as vitro maturation, display significant differences in gene activity when compared to already mature eggs.

The findings may be a clue that the current culture conditions are suboptimal, and this can also explain the lower pregnancy rates seen with the process of in vitro maturation, Patrizio said.

Fertility clinics have started to offer in vitro maturation to some patients because it requires fewer drugs and therefore has fewer side effects such as ovarian hyperstimulation.

The results of this study will help researchers develop ways to better culture immature eggs and pave the way to identify which ones might be most likely to lead to live births, Patrizio stated.

Via | Yale School of Medicine