Longer is best?

Telomere length may be important in determining which human embryos survive and which do not develop, and could lead to new methods for indicating viable embryos for IVF treatment.

Researchers from the University of Warwick and University Hospital, Coventry studied telomere length – regions of repetitive DNA at the end of a chromosome which protect it from deterioration – in oocytes and embryos

“These results have given us plenty of new questions as well as answers,” said lead author Sarah Turner from University Hospital, Coventry, “We now need to find out why telomere length is relatively short in early development.”

Telomere length is shortest in the early stages of embryo development – at around two days – and lengthens just before implantation in the womb at around five days. This lengthening may be essential for normal development; short telomeres may not be able to survive the numerous rounds of cell division that take place as an embryo grows. Telomeres shorten each time a cell divides, and when telomere length becomes critically short, a cell dies.

Lead author Professor Geraldine Hartshorne, from the Warwick Medical School, said: “It has already been shown that artificially shortened telomeres cause problems in animal embryos. Human embryos are highly variable and many of them cannot develop normally. We think that telomere length might one day be used to diagnose which are the most valuable embryos.”

Professor Hartshorne said oxidative stress also shortens telomeres, so their length may also provide a measure of the stressfulness of the culture systems used in IVF and their impact on embryos.

“Our next steps are looking at single sperm and eggs to work out where the telomere length in early embryos is coming from,” said Turner.

Patients undergoing IFV treatment donated oocytes and embryos which were unsuitable for their own treatment to the research.