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Embryo 'squishing' could improve IVF success rates

29 February 2016
Appeared in BioNews 841

Researchers in the USA have shown that 'squishing' an egg within hours of fertilisation can indicate how healthy and viable it is.

A team of scientists at Stanford University Medical Center, California showed that by measuring the rigidity or 'squishiness' of fertilised human and animal eggs, they could predict the likelihood it would grow into a healthy blastocyst. The technique offers a minimally invasive procedure that could improve the success rate of IVF following single embryo transfer, where only the most viable embryo is implanted into the mother.

'From a clinical perspective, once confirmed, the benefit is immense in that it could give us a proxy of viability of the embryo in the blink of an eye, and from that information we can manipulate the patient's cycle in order to improve success,' said Professor Barry Behr, professor of obstetrics and gynecology at the Stanford University Medical Center and co-author on the study.

In the study, published in Nature Communications, the scientists used a small pipette to apply pressure to mouse eggs an hour after fertilisation and then re-examined them once they had reached the blastocyst stage. The results showed that the fertilised eggs that had 'pushed back' were more likely to produce healthy and symmetrical embryos.

The team then used this data to create a computational model that used the egg's 'squishiness' to predict whether the egg would be likely to develop into a well-formed blastocyst.

'We wanted to develop a mechanical test that could ascertain embryo viability well enough that doctors could implant just one embryo and have a very good feeling that it would be viable,' said lead author Livia Yanez, a PhD student at Stanford University.

Using this computational model, viable embryos based on squishiness were implanted into mice. Results showed that these animals were 50 percent more likely to deliver a normal live birth than with embryos that were classed as viable using conventional techniques.

The experiment was then performed using human eggs with 90 percent accuracy. Genome expression analysis showed that viable human embryos had an optimal squishiness. If the fertilised egg was too firm or soft this caused mis-expression of genes that are critical for DNA repair, cell division and chromosome alignment during replication.

'Although cancer and other diseases involve stiff tumors or tissues, our colleagues have been surprised that we can gain so much information from this simple little mechanical test,' said Dr David Camarillo, assistant professor of bioengineering at Stanford University. 'It is still surprising to think that simply squeezing an embryo the day it was fertilised can tell you if it will survive and ultimately become a baby,' he added.

The team wants to now test this model more extensively in patients.

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