İnfertility is such a big problem for couples all around the world. People want to become parents turn to IVF units. Most of the failed IVF treatments are due to low quality embryos. To improve the outcomes and get better quality embryos there have been many approaches:
** Clinical (Different type of treatment protocols, supplement therapies, regenerative therapies such as PRP, stem cell/exosome treatment etc…)
**Laboratory techniques better sperm selection methods such as IMSI /microfluid sperm chip or using artificial intelligence ; using more sophisticated embryo culture mediums; following embryos at the time lapse incubators; targeting for better fertilisation rates with oocyte activation via calcium ionophore /piazzo electric technique etc..
Unfortunately, even these techniques poor embryo quality is still remain as the biggest problem underlying infertility.
The egg cytoplasm is crucial for embryo development. Fertilisation occurs in the oocyte cytoplasm (natural conception, IVF, ICSI, IMSI whatever the technique). This cytoplasm contains mitochondria (the energy centre of the cell), proteins, organelles, mRNAs etc. This microenvironment is the key point for a healthy fertilisation and embryo development. A young and healthy cytoplasm even helps to repair some of DNA damages by helping cell repairment systems. In the light of this knowledge ‘changing this cytoplasm’ has become a new tool to help embryo quality problems.
It has been announced as ‘three parent embryos’; because these embryos contain the mother’s DNA, father’s DNA and also the maternal DNA from the donor egg.
There are two techniques for creating ‘three parent embryos’:
- Cytoplasm Transfer: It has been performed for a long time. During fertilisation (ICSI) the embryologist put some of donor’s oocyte cytoplasm into the mother’s egg cytoplasm with husband sperm.
- Maternal Spindle Transfer (MST):
Spindle means the DNA of egg at the stage of metaphase II.
It is more detailed technique compared to only cytoplasm transfer. Because the donor eggs are enucleated first (the genetic material is removed). Also, the mother’s egg’s spindle is removed and replaced into the donor’s enucleated egg. And after this transfer the new hybrid (mother’s spindle and donor’s enucleated egg) egg is going to be fertilised with husband’s sperm.
During MST the risk for oocyte degeneration is higher than only donor cytoplasm transfer. Sometimes it might need additional oocyte activation method for achieving fertilisation.
Although the idea of having ‘healthy /more energised’ environment for embryo development sounds like a solution unfortunately there are some problems:
**Ovarian age is the most important for egg and possible embryo quality. Unfortunately this cytoplasm treatments’ results are among the younger ages (under 40 years old). If the egg carries abnormal DNA due to aging these treatments cannot correct it and at the end even there is morphologically good quality embryo the genetic test will show abnormality. So it can be useful for idiopathic or repeated İVF failures at young age group.
For advanced age group IVF with donor eggs has the highest pregnancy chance.
The technique itself is needed experienced staff. Especially spindle transfer is required additional equipment and embryologists. And there is still risk for harm on eggs.
**The other risk is even there are healthy babies born from this technique it still has conflicts about long term follow up of these babies. There is always risk for mitochondrial DNA problems .
Especially when the MST is performed to avoid mother’s mithocondrial disease and have healthy offsprings unfortunately it is still posiible to have maternal mitochondria .