In recent years, a new sperm selection technique has appeared: the annexin V columns. It allows the separation of the best quality spermatozoa by applying magnetic fields and is therefore also known as MACS(magnetic-activated cell sorting). In this article, we will explain what it is based on and what clinical applications it has.
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Methods of sperm selection and fertility
Before using any semen sample during a fertility treatment, the semen quality is analyzed by means of a semen analysis, and a sperm selection is carried out to rule out spermatozoa possessing the worst quality.
The most common methods are density gradients and swim-up and both are based primarily on choosing the best motile sperm for treatment.
However, the fact that a spermatozoon has good motility is not always an indication that it is capable of correctly fertilizing the egg. In some cases, there are genetic alterations that do not alter motility but can affect both fertilization and subsequent embryonic development.
Therefore, even if the result of the seminogram is good and the processed sample also shows adequate concentration and motility, some of the spermatozoa selected by traditional methods may not be of as good quality as expected.
For all these reasons, in recent years efforts are being made to find new methods of sperm selection that will allow sperm to be separated more precisely. In doing so, the aim is to improve the results of assisted reproduction techniques.
Assisted procreation, as any other medical treatment, requires that you rely on the professionalism of the doctors and staff of the clinic you choose. Obviously, each clinic is different. Get now your Fertility Report, which will select several clinics for you out of the pool of clinics that meet our strict quality criteria. Moreover, it will offer you a comparison between the fees and conditions each clinic offers in order for you to make a well informed choice.
What are annexin V columns?
One of the new sperm selection techniques is based on the use of columns of annexin V.
To understand this method, it is first necessary to be clear what apoptosis, which is programmed cell death, consists of. It is our body's mechanism for getting rid of damaged or defective cells to ensure that they will not compromise the function of our body's healthy cells.
In order to carry out this process, the cells must undergo a series of changes, as it must be perfectly regulated. Some of these changes are, for example, the fragmentation of genetic material (DNA) or the externalization of some molecules to the outside so that they are recognized as apoptotic cells and are eliminated.
One of these molecules is phosphatidylserine, a phospholipid that apoptotic spermatozoa externalize in the cell membrane. This marker is present on the membrane before sperm motility is affected. Therefore, through their analysis, we can know which spermatozoa will die earlier than with conventional spermatozoa selection methods.
To detect these apoptotic spermatozoa, we have annexin V, a protein that specifically recognizes the phosphatidylserine of these spermatozoa with great affinity. By binding this protein to metal beads, we can select the apoptotic spermatozoa using a magnet.
Therefore, magnetic selection using columns of annexin V consists of adding this protein to the sample and retaining the apoptotic sperm in a column surrounded by a magnet. The ones that do not get stuck in the spine are the ones used in assisted reproduction treatment, as their quality is better.
Advantages and disadvantages
The main benefit of this technique is that it allows for the discarding of apoptotic spermatozoa, which may not be detected by conventional sperm selection methods. Therefore, it is possible to separate the best quality spermatozoa at an early stage.
Several studies have confirmed that thanks to the MACS technique with annexin V, pregnancy ratesimproved.
However, it should be kept in mind that when annexin columns are used, the concentration of the sperm sample decreases considerably, since only healthy sperm will be present in the final sample. This means that the sample resulting from this procedure, in most cases, can only be used for ICSI, as the concentration is insufficient to perform artificial insemination or conventional in vitro fertilization (IVF).
Another disadvantage of this technique is that it is more expensive and laborious than traditional methods. Therefore, it is only recommended to use it in patients where it is indicated.
In which patients is MACS used?
The couples that can benefit most from this method of sperm selection are those in which the cause of sterility is the male factor or inexplained infertility. This technique is indicated in the following cases:
- High percentage of sperm with fragmented DNA.
- Recurrent failures in previous treatments, such as recurrent miscarriages with unknown cause.
- Low fertilization rate.
- Poor embryo quality.
- Sterility of unknown origin.
- Patients who underwent chemotherapy and/or radiotherapy.
FAQs from users
From how many failed cycles is it recommended to use the MACS technique?
MACS should be used whenever a higher than normal level of apoptosis is detected in a semen sample, in order to avoid cell-damaged sperm. Therefore, it is indicated in cases of: severe male factor, implantation failure (usually we talk about two transfers with high quality embryos, which have not generated pregnancy) and those previous IVF cycles in which fertilization or embryo development has not been as expected, despite the fact that the semen sample was normal or almost normal.
What percentage of sperm selection using adnexin V columns increases the probability of successful treatment?
The selection of spermatozoa using adnexin columns substantially improves the chances of success in those cases where it is indicated.
The percentage of improvement will depend on the percentage of spermatozoa with fragmented DNA in the seminal sample, since this will allow us to select healthy spermatozoa, thus increasing the possibility of having good quality embryos.
Can MACS be performed with sperm obtained through testicular biopsy?
No, because the sperm obtained by this technique are scarce. Therefore, when they are passed through the columns of adnexin V, it is very likely that there will not be enough to carry out the treatment.
Are Annex V columns an alternative to density gradients?
No, the most advisable thing is to pass the sample through density gradients to eliminate spermatozoa with poor mobility and to make the sample cleaner. In this way, it is easier to make the subsequent magnetic selection more efficient.
Can sex be selected using this technique?
No. This technique is based on a marker that is in the sperm cell membrane. To date, there is no known external marker that allows us to separate the sperm with the X sex chromosome (fetus will be XX, female) from those with the Y sex chromosome (fetus will be XY, male).
Suggested for you
As we have seen, patients with a DNA fragmentation index can benefit from the use of this new technique. You can find more information about this disorder in the following article: What is sperm DNA fragmentation?
In addition to the MACS technique, there are also other new sperm selection methods, such as IMSI and PICSI. IMSI (Intracytoplasmic Morphologically Selected Sperm Injection) consists of choosing the sperm to be used in ICSI using a more powerful microscope that allows a better visualization of the morphology. If you want to delve deeper into this topic, we recommend you to visit this article: What is IMSI?
On the other hand, PICSI (physiological ICSI) consists of selecting the spermatozoa that would be capable of fertilizing the egg under physiological conditions, i.e. in the mother's body. In the following article, you can read more about this technique: What is PICSI?
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FAQs from users: 'From how many failed cycles is it recommended to use the MACS technique?', 'What percentage of sperm selection using adnexin V columns increases the probability of successful treatment?', 'Can MACS be performed with sperm obtained through testicular biopsy?', 'Are Annex V columns an alternative to density gradients?' and 'Can sex be selected using this technique?'.