Science is tiptoeing towards a new procedure that could revolutionize fertility treatment, as researchers demonstrate the possibility of transferring DNA from skin cells into a donor egg. While we’re still years away from this being used in the clinic, it could mean a future where women without viable eggs and men in same-sex relationships are able to have children who are genetically related to them.
Damaged or degraded egg cells resulting from disease, medical treatment, or aging are a common cause of infertility. This procedure aims to get around this problem by taking a donor egg, removing its nucleus (where all the genetic information is stored), and replacing that with the nucleus of a skin cell from the parent. You’re then left with a functional egg, containing only genetic material from the parent-to-be and not from the donor.
The technique is called somatic cell nuclear transfer, and while it might sound simple, the reality is far from it.
However, there is a precedent going back over 20 years, with a momentous event that sparked interest in applying this process to humans: the first-ever cloning of a mammal, Dolly the Sheep.
Dolly was no ordinary sheep.
Dolly was created using DNA from a single adult sheep. Where the new process differs, according to the team from Oregon Health & Science University (OHSU) behind the research, is that it is possible to create embryos containing DNA from both parents.
To be very clear: we are not – repeat, not – talking about human cloning.
The team first reported that their experimental procedure could work back in January 2022, but the new study has taken things a step further, demonstrating how it’s possible to achieve the correct number of chromosomes in the egg cell to begin with.
Human sex cells, or gametes, are described as haploid – this means they contain half the number of chromosomes of other cells in the body. When a haploid egg cell is fertilized by an equally haploid sperm cell, the resulting embryo is diploid, with a full complement of chromosomes.
The team at OHSU took egg cells from mice and stripped them of their nuclei, replacing them with nuclei from mouse skin cells. “But wait!” you exclaim. “Aren’t skin cells diploid?” They are indeed, but the team has an ingenious solution. They are able to induce the implanted nucleus to shed half of its chromosomes, resulting in a haploid cell that is virtually indistinguishable from a natural egg cell.
These eggs can then go through in vitro fertilization (IVF) with sperm, a technique that’s used daily in fertility clinics around the world. When successful, it results in an embryo containing chromosomes from two parents.
One of the advantages of the technique is the speed with which the eggs can be produced. Other similar methods under investigation right now require a long process of first turning the skin cells into induced pluripotent stem cells, and then nudging those cells down the path to become eggs or sperm.
“We’re skipping that whole step of cell reprogramming,” explained study author Dr Paula Amato in a statement. “The advantage of our technique is that it avoids the long culture time it takes to reprogram the cell. Over several months, a lot of harmful genetic and epigenetic changes can happen.”
The eventual vision, as laid out by senior author Dr Shoukhrat Mitalipov, is “to produce eggs for patients who don’t have their own eggs,” but this goal is still years away. First author Aleksei Mikhalchenko told the Guardian that “thorough evaluation of safety, efficacy and ethical aspects” will be essential before the technique could be considered for clinical use.
IVF is back in the media spotlight following the Supreme Court of Alabama’s ruling that embryos should be treated as children, with many forecasting this as a key debate in the run-up to the US presidential election. But the ramifications of any advances in assisted reproduction will extend far beyond a single country’s borders; an estimated 1 in 6 adults are affected by infertility worldwide.
The ability to use a donor egg without also incorporating DNA from the donor would certainly rank as a radical change in the landscape of fertility treatment. With this study, science has taken a step forward in its understanding of how this could one day become a reality.
The study is published in Science Advances.
Source Link: DNA From Skin Cells Could Be Used To Make The IVF Eggs Of The Future
