U. WARWICK (UK)—Scientists have for the first time directly measured a specific region of DNA in human embryos that could be used as a quality marker for embryonic development.

Researchers measured telomeres, regions of repetitive DNA at the ends of a chromosome which protect it from deterioration. Telomeres shorten each time a cell divides and when telomere length becomes critically short, the cells die.

The research, published in Molecular Human Reproduction Journal, suggests that telomere length is shortest in the early stages of an embryo’s development, at around two days, and then lengthens just before implantation in the womb at five days.

This lengthening may be essential for normal development, because short telomeres may not be enough to survive the many rounds of cell division that take place as embryos grow.

The discovery could have implications for in vitro fertilization (IVF) treatment.

“It has already been shown that artificially shortened telomeres cause problems in animal embryos,” says Geraldine Hartshorne, University of Warwick professor.

“Human embryos are highly variable, and many of them cannot develop normally. We think that telomere length might one day be used to help diagnose which are the most viable embryos.

“We also know that telomeres shorten with oxidative stress, so telomere length might also provide a measure of the stressfulness of the culture systems that we use in IVF and their impact on embryos.”

The research project used oocytes and embryos donated by patients undergoing IVF treatment. Only material that could not be used for the patients’ own treatment was accessed for research.

“These results have given us plenty of new questions as well as answers,” says Sarah Turner, from University Hospital, Coventry.

“We now need to find out why telomere length is relatively short in early development. Our next steps are looking at single sperm and eggs to work out where the telomere length in early embryos is coming from.”

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