Our cells’ “parcel delivery service” can help check for healthy embryos in IVF
Reproductive Health IVF Embryo Transfer

Our cells’ “parcel delivery service” can help check for healthy embryos in IVF

Dr. Mónica Faut
Dr. Mónica Faut

In 10 seconds? Researchers are proposing a new method to spot abnormal chromosome counts during in vitro fertilization. The non-invasive technique can help screen the genetic integrity of embryos’ before implantation and thus reduce the failure rate.

Why is it significant? Women under 35 choosing IVF have around a 60% chance to become pregnant after an embryo transfer, whereas for women over 40 the ratio drops to 20%. Around half of the failures are caused by abnormal chromosome counts in the embryos. Therefore, the ability to identify the embryos with these defects cuts this fail rate and improves the chances of giving birth to a healthy baby who will not develop certain diseases (example: autism and neuro-cognitive disabilities) later on. The  discovery allows us to avoid invasive testing, i.e. biopsies of the pre-implantation embryos grown in the lab. (Please note, we are describing the science and not taking a stand in the faith and ethical debate).

OK, so what is an abnormal chromosome count? No problem! The zygote, or in everyday language the fertilized human egg has 23 chromosomes from the mother and 23 from the father. It starts dividing in the first few days before further developing and this is the stage when chromosomal abnormalities can happen when there are too many or too few chromosomes in the zygote. For example, one extra chromosome will make the baby have Down syndrome.

Wait, but embryologists can already check embryos’ DNA, right? Yes. Until now, the procedures involved an embryo biopsy - a complex procedure that is carried out by a highly trained embryologist. Since 1993, Preimplantation Genetic Testing (PGT) has been performed in almost all IFV cycles, involving different variations, i.e. testing for single-gene disorders, chromosome abnormalities, and others. This test provides patients with an opportunity to reduce the chance of a genetic disease in their future children before pregnancy.According to the ESHRE PGT consortium, the efficiency of diagnostic testing is high (between 88% and 94%).

Embryo–maternal interactions mediated by extracellular vesicles secreted from the embryo and endometrium cells. Red dots: embryo-derived EVs, green dots: Endometrium-derived EVs. Source: Bridi, Perecin, da Silveira, 2020
Embryo–maternal interactions mediated by extracellular vesicles secreted from the embryo and endometrium cells. Red dots: embryo-derived EVs, green dots: Endometrium-derived EVs. Source: Bridi, Perecin, da Silveira, 2020

So, what’s the big deal about the new method? Well, with the current method, scientists are concerned that the invasive biopsy can decrease the embryo’s quality, and make the procedure more expensive. So, naturally, they were looking for non-invasive techniques. This newly discovered method promises to be a safer, non-invasive cutting-edge technique.

OK, what is it? It’s called Extracellular vesicle analysis. Yeah, I know it sounds like scientific mumbo-jumbo, so let me explain! Extracellular vesicles (EVs) are like little balls dashing between our cells in the space between them. They are a kind of means for communication between cells and tissues, or little parcel couriers, delivering proteins and other “parcels” to cells. These vesicles contain numerous molecules that can affect the behavior of cells. Recently, researchers have found that these EVs represent an additional layer of communication in the female reproductive system, namely between the embryo and the endometrium. Animal studies have found that EVs from embryos can attach to cells lining the womb and higher numbers indicate a higher likelihood of successful implantation.

How solid is this research? A recent report suggests that all the knowledge regarding EV biology is strong enough to justify its implementation in embryo quality diagnosis. According to the researchers, the high sensitivity of this method enhances the understanding of the molecular field of reproduction. Even more, they propose that EVs have the potential to be reviewed with a particular focus on oocyte competence (the ability of eggs to mature and sustain an embryo), semen quality diagnostics, and detection of endometrial receptivity (the ability of the embryo to “take root” and develop).

Is this available in an IVF center? Well… not yet. Despite all data, there is no standard protocol to use it yet in human health. First, the techniques to collect, isolate, and store EV are different in each lab, and these could modify the results of the analysis. And, much of the research is performed in vitro (lab cells) and in test animals, and we know that in vitro studies cannot replicate the dynamic and complex human reproductive environment.


Cost is a factor in Preimplantation Genetic Testing

A high number of clinics use PGT as an integral part of IVF procedures to ensure the genetic integrity of the transferred embryo, i.e. the high probability of successful pregnancy.

But this, in turn, makes IVF treatment expensive for many couples.

Between 2014 and 2016, the proportion of PGT cycles as a total of Assisted Reproductive Technology procedures remained the same in the UK but increased annually in the USA from 13% to 27%.

A non-invasive embryo screening method, such as the analysis of embryo-secreted EVs, would make IVF treatments more successful, avoid potential embryo damage, reduce cost, and make IVF more accessible to couples.

Mónica has distilled 8 research papers, saving you 28 hours of reading time


The Science Integrity Check of this 3-min Science Digest was performed by Michael Eze.



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