In vitro Fertilization with Cytoplasmic Transfer

Cytoplasmic transfer, also known as ooplasm transfer, is a new approach to in vitro fertilization (IVF), when IVF failure is associated with the deficient or damaged mitochondria. In this method, ooplasm, which is the cytoplasm of an egg, is taken from a younger donor to be transferred to achieve pregnancy. An ooplasm from a younger donor includes healthier cytoplasmic content; mitochondria, other organelles, and “unknown cytoplasmic factors”, which will eventually improve the quality of an egg.

Why is Mitochondrial Quality Important to Achieve Pregnancy?

Energy generation, cell division, and cellular growth are all controlled by mitochondria, which is an organelle found in the cytoplasm of egg cells. According to a 2021 article, mitochondrial DNA replication ceases, and each cell division reduces the amount of mitochondria in each blastomere by 50% during fertilization. As a direct consequence of this, a relatively small number of mitochondria are found in each blastomere when the blastocyst is formed.

Mutations in mitochondrial DNA (mtDNA) occur 10 times more frequently than in nuclear DNA and, therefore, may cause mitochondrial dysfunction in blastocyst stage, especially after maternal age. As a result, mitochondrial dysfunction can induce recurrent implantation failures as well as high levels of embryo fragmentation, both of which are causes of poor embryo growth and, as a result, a failed IVF cycle. It can also cause poor embryo development.

Why is Cytoplasmic Transfer Done?

Since mitochondrial dysfunction is commonly seen in women as they get older, those in their late 30s or early 40s who are trying to conceive through in vitro fertilization have a higher risk of having their attempts fail owing to this problem. Cytoplasmic transfer is performed during IVF treatment if any problem associated with mitochondrial dysfunction is suspected. This might be observed as a result of multiple IVF failures. 

How is IVF with Cytoplasmic Transfer Performed?

In cytoplasmic transfer, the patient's own eggs are used, but the procedure also requires an ooplasmic donor with relatively young age so that a healthy cytoplasm necessary for transplantation is acquired. Ooplasmic donor’s cytoplasm is transferred by direct injection or electrofusion. An egg that possesses cytoplasmic organelles from both their biological mother and the ooplasmic donor is then  fertilized with sperm and implanted in the uterus to achieve the pregnancy.

What are the Risks of Cytoplasmic Transfer?

From a genetic point of view, combining nuclear DNA with a donor's mitochondrial DNA (mtDNA) may pose some concerns. However, these concerns are a pretty advanced topic and still controversial due to the lack of solid evidence. It is best to discuss the eligibility of this operation for your case with your doctor.