Dr. Kirsty Horsey, Progress Educational Trust
03 February 2004
[BioNews, London]
Mice born following the use of assisted reproduction techniques (ARTs) show differences in their behaviour that could be caused by the embryo-culturing process, a new US study suggests. Researchers at the University of Pennsylvania found that adult IVF mice seem more confident, but had slightly worse memories than their naturally-conceived counterparts. The scientists stress that their results are not 'directly applicable' to children conceived through ARTs, but say the study highlights the need for further research into culture conditions for human embryos. The action of some genes could be disrupted when an embryo is grown in the laboratory, they say, a process that has unknown long-term consequences. The scientists carried out a series of behavioural tests on adult mice derived from embryos cultured in the laboratory. They found that compared to naturally-conceived animals, the IVF mice moved around more, and spent more time in open spaces. Such behaviour goes against a mouse's natural fear of being in the open, and suggests a decrease in anxiety, the researchers say. Other tests revealed that although the IVF mice showed no differences in learning ability, development or movement control, they did have slightly worse memories. Study author Richard Schultz described the effects as 'subtle but significant'.
The new study, which is published in the online edition of the journal Proceedings of the National Academy of Science, supports previous research showing that some genes may be disrupted in laboratory-cultured embryos. In particular, there is some evidence linking IVF to certain rare 'imprinting disorders' such as Beckwith-Wiedemann syndrome. Imprinting is the process by which some genes are switched on or off in very early mammalian embryos, according to which parent they were inherited from.
The researchers say their findings suggest a broader need to examine the techniques used in assisted reproduction. In particular, they say, the length of time and conditions under which embryos are cultured in the laboratory before being transferred to the womb should be optimised: 'Decreasing the length of time between fertilisation and implantation and further refining the composition of the culture medium are two ways that may mitigate risk' said author Ted Abel.
UK biologist Tom Fleming, of the University of Southampton, said of the new research: 'We don't know if this relevant to humans, as there are a number of differences between animal and human embryos'. He added that it would be wrong to cause a scare over the findings, but that it was 'probably a good idea to limit the length of time an embryo is in culture'.
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