Within the ample sphere of human cloning, a new and controversial option has emerged: producing children from three genetic parents. This has been made possible through the use of a mitochondrial replacement technique, which basically consists of removing the nucleus from an egg, leaving the mitochondrial DNA, transferring to it the nucleus from another egg and subsequently fertilising that hybrid egg with sperm from a donor. This method would produce a child with two genetic mothers and a father.
This technique was specifically developed to prevent mitochondrial conditions. Although these organelles only contain 1% to 2% of cellular DNA, they can still give rise to serious conditions when their DNA is altered, leading to neurodegenerative disease, brain infarction, blindness, muscular dystrophy, diabetes, and deafness and may even cause death in newborn babies, children, youth and adults. This is the reason why a technique such as this is welcomed by parents who want to try to prevent these conditions derived from alterations in the mother’s mitochondria from being passed down to their children – a method which involves transferring the nucleus taken from the egg bearing mitochondrial alterations and placing it in an enucleated egg with normal mitochondria. This creates a new hybrid egg in which the majority of the DNA comes from the nucleus of the mother whose mitochondria are abnormal, with just a small proportion coming from the mitochondrial DNA of another woman.
In theory, this practice may seem acceptable but it gives rise to objective ethical issues, namely the ethical problems associated to the use of cloning to produce a human being and those associated to the use of in vitro fertilisation to produce a child.
In addition, there are other ethical issues that are directly linked to the mitochondrial transfer technique, which have been discussed by F. Baylis in a recent and fascinating article (Reproductive Biomedicine Online 26; 531-534, 2013).
Baylis sets out several of the principal objections to the use of the mitochondrial transfer technique described above.
1. The first concerns the possible harm which could come to the woman who donates her eggs. The risks that come with ovarian hyperstimulation techniques applied to the egg donor are widely known, and vary from abdominal pain, nausea and vomiting, to other, more serious side-effects such as weight gain, respiratory difficulty and damage to other organs including the bladder, intestines or uterus, as well as other long-term indirect side-effects such as reduced fertility, infertility, haemorrhage, thromboembolic events, increased risk of ovarian, breast or colon cancer and on rare occasions, death. In other words, there are objective risks to the donor who, apart from financial compensation, receives no other benefit from the procedure.
As regards the risks of ovarian hyperstimulation and the ethical issues raised when the purpose of this procedure yields no benefit to the woman undergoing said procedure, we would like to remind our readers of the first example of “human cloning” performed by Korean researcher Woo Suk Hwang, who was dismissed from his academic posts not only for falsifying his data, but also because he was suspected of forcing some of his female interns to donate eggs for his research. These donations must have been copious given the low efficiency of the cloning technique used by Hwang.
At any rate, it is clear that using a woman for her eggs as a source of mitochondria carries significant ethical considerations that are impossible to ignore.
2. The second issue discussed by Baylis is that associated to the possible harm of this technique to children and their descendents. Baylis argues that at present, there is little data on the safety and efficiency of this method. Moreover, any manipulation of a germ line must necessarily take into account potential health conditions in descendents.
Nor do we know whether the method of mixing DNA from two mothers is medically safe or whether they could cause alterations to one’s health that are still relatively unknown.
3. The third reason is that the use of this technique would invalidate family-based genetic studies that make use of mitochondrial DNA, thereby hampering any efforts to obtain genealogic information that would be useful in trying to establish family identity.
4. Baylis’s fourth concern involves social considerations. Although this technique is now only being considered for use in the prevention of disorders associated to mitochondrial alterations, it can also be used for other purposes not linked to therapeutic aims. For instance, this method can be used by two women in a same-sex union wishing to create a hybrid egg through the mixing of a nucleus of one woman’s egg with the other’s mitochondria. This egg would then be fertilised to produce a child that is genetically related to both women.
This technique could also be used in genetic enhancement – a procedure which raises significant ethical issues which cannot be detailed here.
We believe that mitochondrial transfer used for any of the purposes explained above carry serious fundamental ethical implications. It is a clear example of a human cloning technique, with all the ethical issues that it entails. These implications are a direct threat to dignity of the human being produced and should not, under any circumstance, be considered ethically acceptable.
Director del Instituto de Ciencias de la Vida de la UCV
Miembro de la Pontificia Academia para la Vida