Mitochondrial donation is a practice that decreases the chances of passing a mitochondrial disease from a mother to her child. In this article, we tell all about mitochondrial donation, what it is and how it is done, along with the accessioned risks and concerns.
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- What is mitochondrial disease?
- What is mitochondrial donation?
- What are mitochondria?
- What techniques does mitochondrial donation involve?
- Issues with mitochondrial donation
- Risks of mitochondrial donation
- Advantages of mitochondrial donation
- Related articles
What is mitochondrial disease?
Mitochondrial diseases belong to severe medical disorders that can be inherited, meaning that the transmission of mitochondrial DNA (mtDNA) from the mother to the child is quite likely. In the case of mitochondrial disease, genetic mutations take place and lead to the inability of mitochondria to derive energy from oxygen and food.
In other words, the risk of passing the disease from the mother to the child translates to the risk of the child's organelles being unable to perform mitochondrial functions. This causes cell damage and even death.
The presence of mutated mtDNA in the body leads to illnesses and, therefore, poor quality of life. And in the case of severe mitochondrial disease, one may go through organ and system failures, eventually dying at a young age.
One of the ways to treat mitochondrial diseases is with genetic research and the donation of biomaterials.
What is mitochondrial donation?
Mitochondrial donation is a type of assisted reproductive technology performed by a fertilization and embryology authority to prevent mitochondrial disease in the fetus. It is performed as a part of the in vitro fertilization (IVF) cycle. Most often, it is recommended to introduce mitochondrial DNA donation to couples where mothers have the disease and, therefore, pose a risk of passing them to the child.
Mitochondrial donation techniques imply that a healthy woman donates an egg for the couple going through IVF to use for conception. The fertilization and embryology experts then perform a procedure of removing the mitochondrial DNA mutations from the egg that will be placed in the patient’s uterus to prevent the transmission of the disease.
In such a way, the woman gets a healthy egg with unhealthy mitochondria removed and fertilized with mitochondrial genes from the donated egg. This is the method used to avoid mitochondrial disease transmission from the mother to the child with assisted reproductive technology.
What are mitochondria?
Mitochondria are organelles that are a part of almost every cell in the human body. Their function is to ensure the proper performance of the cell by supplying it with energy that we get, like with the food we eat. In case of mitochondrial failure, our cells do not receive the power to operate properly, which leads to damage in bigger systems, like organs.
Mitochondria are present in the eggs, too — they help them to work right to be suitable for fertilization and then grow into a healthy fetus. If there is any type of mitochondrial damage in the egg, the fetus is at risk of developing mitochondrial diseases. To prevent mitochondrial disease with donations, donor eggs are used to get a healthy environment for the genetic material of the parents.
What techniques does mitochondrial donation involve?
To prevent the transmission of mitochondrial disease from the mother to the child, the embryology authority can use one of the 2 techniques: maternal spindle transfer (MST) and pronuclear transfer (PNT). Regardless of which one is used, the embryo will end up containing the couple's nuclear DNA, taken from their egg and sperm, and healthy organelles, which are taken from the donated egg.
Maternal spindle transfer (MST)
In the case of maternal spindle transfer (MST), the process starts with exchanging genetic material between the mother's and donor's eggs. To ensure that there will be no transmission of mitochondrial DNA that is unhealthy while other parents’ genes are included, the donor's nuclear DNA is replaced with the mother's one in the donated egg.
The MST procedure results in an egg that contains the mother's nuclear DNA and donor's healthy genetic material. The egg is then fertilized with the father's sperm to create an embryo, which will later be used to complete the IVF cycle.
When pronuclear transfer (PNT) takes place, both the donated and the mother's eggs are first fertilized with the partner's sperm. Now, the embryology authority exchanges the nuclear DNA in the eggs to receive the parents' nuclear DNA with healthy mitochondria in one egg.
Similarly to the first method, the pronuclear transfer results in a fertilized egg with the right mitochondrial DNA, hence preventing the mitochondrial disease from the transmission to the fetus.
Issues with mitochondrial donation
Since mitochondrial research on donation is relatively recent and continues, there are still some uncertainties associated with it. There 3 main areas of concern are ethical, social and legal.
One of the ethical concerns regarding assisted reproductive technology methods to avoid mitochondrial disease transmission implies that mitochondrial replacement therapy involves working with human embryos. Since they are considered morally significant, the changes in the mutated mitochondrial DNA performed on the embryos are, therefore, a major concern in the debate.
Another ethical issue related to the donation of mitochondrial material is that humans get involved in the natural processes. While the long-term goal is to improve national health, the fact that there's human interference and genetic modification makes it an ambiguous practice in terms of ethics.
One of the biggest social issues related to introducing mitochondrial donation techniques is the effects it may have on humanity as a whole. Since the history of mitochondrial donation is not that long, the consequences of mitochondrial transfer on future generations are unknown in terms of people’s physical health and relationships, as well as changes in their genetic material.
Another concern is caused by the fact that a third person is involved in the process and implies the ambiguity of their role in the future family. The way things will stand will be uncertain if the child is eager to start a relationship with the person who participated in the donation of mitochondrial DNA.
Lastly, one more social concern is that gene therapy is not accessible to everyone — only social groups that are economically forward can use it. The cost of the practice and access to medicine, in general, is a privilege that not all individuals have.
As for the legal issues that are associated with the prevention of mitochondrial diseases, these are also related to the use of human biomaterial and the involvement of the people who donate mitochondrial DNA. For example, the issue with using human eggs for donation implies that egg trade may occur, which poses a risk to the rights, freedom and safety of people.
At the same time, the problem with involving a third person creates an ambiguous situation in terms of the right the person gains on the child and the child's right to reach out to the donor. Even if the donor agrees to have no interest in the child any time in the future, the issue of information retention comes up because the donor’s data still needs to be kept for scientific and medical reasons.
Risks of mitochondrial donation
There are some risks that the methods of mitochondrial diseases transmission prevention pose. One of them is that there is no complete guarantee that it will help prevent the transmission of mitochondrial DNA disorders to the embryo. While the process requires extracting the mtDNA disease and placing it in the healthy egg, there are still chances that all unhealthy organelles are not eliminated from the embryo and enter the embryo.
The reason is that some faulty organelles can still get stuck to the DNA in the course of the procedure, and there's nothing fertilization and embryology authority representatives can do about it. With this being said, there is no 100% guarantee that the procedure will prevent the mitochondrial disease from transmission to the fetus.
Then, the extent of mitochondrial DNA diseases will affect the success of the procedure, too. If the unhealthy organelles are still there when an embryo is created, the way they will be balanced with the healthy ones is unpredictable. Sometimes the healthy DNA will prevail, but in some cases, the disease will still be present in the DNA after the procedure and keep the disease active and evolving. This may lead to the occurrence of severe mitochondrial disease in the fetus or even the next generation.
Lastly, there is a chance of a mismatch between the mitochondrial donor's and mother's DNA. Depending on the origins of the mitochondrial donor and the mother, there may appear a mismatch of the mitochondrial genome haplotypes. While this does not mean that the mitochondrial replacement techniques will be ineffective, there are still potential risks of mitochondrial donation caused by the mismatch.
Advantages of mitochondrial donation
While there are certain risks associated with mitochondrial gene donation, the advantages of mitochondrial donation remain strong. In general, it is one of the most effective methods to avoid mitochondrial diseases in children in case of the mtDNA disease presence in the mother. That’s why patients should have mitochondrial DNA donation in case of being under threat of transmission.
Because of the severe consequences of the disease on the person's health and quality of life, the ability of fertilization and embryology specialists to prevent mitochondrial diseases is a significant opportunity. In case of a successful procedure, it is possible to eliminate the present type of mitochondrial diseases in the family and improve national health in the long run.
Now that you know more about mitochondrial donation and how it works, you can really see that this is a helpful practice to prevent mitochondrial diseases. Even though there are still some concerns and risks associated with it, it helps decrease the chances of passing the disease to the child and potentially the next generations. Therefore, it is a helpful practice in assisted reproductive technology.
M.D., IVF specialist, gynecologist, reproductive endocrinologist, expert of ultrasound diagnostics.