Researchers at OHSU and the Salk Institute for Biological Studies have developed a way of transmitting a mother's genetic material into donor eggs. The breakthrough may someday benefit families who are struggling with infertility or a genetic predisposition for debilitating mitochondrial disease.
The team discovered that it's possible to regenerate human eggs or oocytes — the cellular beginning of an embryo — by making use of genetic material that normally goes to waste.
This DNA comes from small cells called polar bodies. Until now, they had never been shown to be potentially useful for generating functional human eggs for fertility treatments. In the study, scientists successfully transplanted a polar body from a woman's developing oocyte into the cytoplasm of a donor oocyte stripped of its nucleus.
Though the technique could be years away from progressing to clinical trials, the advancement could eventually be significant for women of advanced maternal age. One recent survey showed that the average age of first-time mothers increased in the United States from 21.4 years in 1970 to 25 years in 2006.
"We know that fertility declines as women get older," said Shoukhrat Mitalipov, PhD, co- senior author and director of the OHSU Center for Embryonic Cell and Gene Therapy. "This is potentially a way to double the number of eggs we're able to get from one session of in vitro fertilization."
Normally, polar bodies disintegrate and disappear during egg development, explained co-first author Hong Ma, MD, PhD, with OHSU's Center for Embryonic Cell and Gene Therapy. "We were able to recycle them. We hope that by doing this, we can double the number of patient eggs available for in vitro fertilization," added Ma.
In addition to potentially benefitting 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 maximizes the chances of families having a child through in vitro fertilization free of genetic mutations," Mitalipov said.
Mitalipov previously developed a mitochondrial replacement therapy involving the implantation of patient's egg nucleus — or spindle — into a healthy donated egg stripped of its original nucleus. Mitalipov also has successfully demonstrated the spindle-transfer technique in the healthy offspring of rhesus macaque monkeys.