Early embryos with abnormal chromosomes are capable of returning to normal when grown in culture in the laboratory, according to new research presented to the 21st annual conference of the European Society of Human Reproduction and Embryology today (Monday 20 June).
While such embryos are not capable of developing into normal foetuses if implanted in a woman's womb, the discovery has important implications for stem cell production, especially in countries where the creation of embryos for stem cell research is discouraged or even banned.
Dr Santiago Munné, Director of Reprogenetics, West Orange, New Jersey, USA, told the conference: "Embryos that will not implant or are predestined to miscarry because of chromosome abnormalities, may be a source of more ethically or politically acceptable stem cells because the abnormal cells may self-correct if grown in the laboratory. In addition, stem cells derived from embryos that did not self-correct could be used to study the effect of various chromosomal abnormalities on human development."
Dr Munné took 50 embryos, which preimplantation genetic diagnosis (PGD) had classified as abnormal at the third day of their development, and grew them in culture to the blastocyst stage when the embryonic cells start to differentiate. They were checked on day five to confirm the original diagnosis of chromosome abnormality, and continued to grow to day 12 when 34 of the embryos had succeeded in attaching to the feeder cells in the culture.
Dr Munné said: "Analysis at this stage showed that seven embryos were totally normal, six were mostly abnormal, and 11 had experienced some chromosome normalization, having between 21-88% normal cells. One embryo was tested for, and proved to show, expression of the OCT4 gene, which is essential for the survival of embryonic stem cells and primordial germ cells1."
Good quality, normal embryonic stem cells were obtained initially from one of the normalised cultures, and more are being developed. So far no stem cells from completely abnormal embryos have been developed.