Scientists have discovered a way to regenerate human eggs using the mother’s genetic material that normally goes waste, a breakthrough that may help women of advanced maternal age struggling with infertility treatments. The ‘waste’ DNA comes from small cells called polar bodies that form off eggs and contain the same genetic material as in a woman’s egg nucleus.
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Until now, polar bodies had never been shown to be potentially useful for generating functional human eggs for fertility treatments.
Scientists at Oregon Health and Science University (OHSU) and the Salk Institute for Biological Studies in the US successfully transplanted a polar body from a woman’s developing oocyte – the cellular beginning of an embryo – into the cytoplasm of a donor oocyte stripped of its nucleus.
Though the technique may be years away from progressing to clinical trials, the advancement eventually could be significant for women of advanced maternal age, researchers said.
“We know that fertility declines as women get older. This is potentially a way to double the number of eggs we are able to get from one session of in vitro fertilisation,” said Shoukhrat Mitalipov, from OHSU.
“Although it was only possible to examine a limited number of lines, from the point of view of epigenomic profiles, the quality of polar body-derived embryonic cells looks quite promising,” said Joseph Ecker from Salk Institute.
By rescuing polar bodies that would otherwise simply bud off the developing oocyte, researchers were able to form additional oocytes genetically related to the mother through nuclear transfer.
When fertilised with sperm, the new oocytes developed into viable embryos. None of the embryos were implanted to carry out an actual pregnancy.
“Normally, polar bodies disintegrate and disappear during egg development. We were able to recycle them. We hope that by doing this, we can double the number of patient eggs available for in vitro fertilisation,” said Hong Ma from OHSU.
In addition to potentially benefiting women of advanced maternal age, the technique may present another opportunity to help women known to have mutations in their mitochondria, the tiny powerhouses inside nearly every cell of the body.
Mutations in mitochondria can result in debilitating forms of disease in children.
“This new technique maximises the chances of families having a child through in vitro fertilisation free of genetic mutations,” Mitalipov said.
The study was published in the journal Cell Stem Cell.