New research suggests that embryos that contain abnormal cells still have a chance of developing into healthy babies.
It was previously thought that these cells indicate a birth defect such as Down’s syndrome, but a team of experts has now demonstrated that abnormal cells are often destroyed and replaced with healthy cells. Consequently, the embryo can be completely repaired.
Professor Magdalena Zernicka-Goetz and her team at Cambridge University, UK, carried out a series of tests on mice with a condition known as aneuploidy, in which some embryo cells contain an abnormal number of chromosomes. This reflects certain human conditions, for example, babies born with three copies of chromosome 21 will develop Down’s syndrome.
Knowledge of the likely outcome of these cellular changes is important, as pregnant women in high-risk groups may undergo chorionic villus sampling during early pregnancy, to remove and analyse placenta cells and predict the likelihood of genetic abnormalities. A more accurate test, amniocentesis, may also be carried out in early-to-mid pregnancy.
Hence pregnant women need to know the potential implications for the fate of the embryo, the researchers say. So the team monitored changes in abnormal cells in mouse embryos. This showed that many were destroyed, even when abnormalities remained in placenta cells.
Details appeared on 26 March in Nature Communications.
Professor Zernicka-Goetz, said: "I am one of the growing number of women having children over the age of 40. Many expectant mothers have to make a difficult choice about their pregnancy based on a test whose results we don’t fully understand.
"Given that the average age at which women have their children is rising, this is a question that will become increasingly important."
She added: "The embryo has an amazing ability to correct itself. We found that even when half of the cells in the early stage embryo are abnormal, the embryo can fully repair itself.
"If this is the case in humans, too, it will mean that even when early indications suggest a child might have a birth defect because there are some, but importantly not all abnormal cells in its embryonic body, this isn’t necessarily the case."
Bolton, H. et al. Mouse model of chromosome mosaicism reveals lineage-specific depletion of aneuploid cells and normal developmental potential. Nature Communications 26 March 2016 doi: 10.1038/ncomms11165
Leave a Reply