Advanced sperm selection techniques
Characteristics of conventional techniques
Conventional sperm selection techniques used in assisted reproduction (swim-up and density gradients) are based on the recovery or selection of sperm with the best motility and morphology.
In some cases, spermatozoa with normal morphology or motility may exhibit high levels of oxidative stress and DNA fragmentation, two parameters that are not detected in a conventional semen analysis. These abnormalities are significantly more common in subfertile men with abnormal semen parameters, although they can also be found in men with normal semen parameters.
Oxidative stress:
This situation arises when there is an imbalance between reactive oxygen species (ROS) and the antioxidant system. ROS are oxidising agents produced during normal cellular metabolism.
DNA fragmentation:
It involves breaks in the DNA strand within the sperm nucleus.
High levels of oxidative stress can lead to a high rate of DNA fragmentation, which can cause male infertility and compromise the chances of achieving a natural pregnancy, as the genetic integrity of the sperm is essential for embryonic development.
There are different types of sperm DNA fragmentation: single-strand and double-strand. Single-strand breaks are associated with a lower conception rate. On the other hand, double-strand breaks do not prevent pregnancy, but may carry a higher risk of miscarriage.
What are the latest techniques like?
There are now more sophisticated methods designed to select sperm in the most physiologically appropriate way possible, ensuring better morphological and motility characteristics and causing less DNA damage.
These sperm selection techniques are recommended in the following cases:
Patients with an elevated sperm DNA fragmentation index
Patients with recurrent miscarriage
Patients who have not achieved a pregnancy after two or more cycles
Males of advanced age
Our medical and biological team will advise you and recommend the use of these techniques in cases where it is deemed appropriate, following an individual assessment of each patient.
Some of the techniques we use at URE Centro Gutenberg are:
Sperm selection using MACS
Magnetic Activated Cell Sorting (MACS), also known as the annexin V column, is a technique used to remove spermatozoa showing signs of apoptosis (programmed cell death), which is generally associated with high oxidative stress leading to DNA fragmentation.
In patients with a high rate of sperm DNA fragmentation, it has been observed that a significant proportion of spermatozoa exhibit cellular damage related to apoptotic processes. In these cases, MACS acts as a complementary technique in semen preparation, with the aim of recovering spermatozoa without markers of apoptosis and selecting those with the highest viability and fertilisation potential for use in assisted reproduction procedures.
Sperm selection using microfluidics or microchannels.
Sperm selection systems based on microfluidics or microchannel flow, such as Zymot Multi, aim to recover spermatozoa with greater motility, better morphology and lower DNA fragmentation, using a process that is more physiologically similar to natural processes than conventional semen preparation methods.
In these state-of-the-art devices, sperm must pass through microchannels or micropores, allowing those with the best motility to be selected and those of lower quality to be discarded. The aim is to exclude sperm with high levels of double-strand DNA fragmentation, increased production of reactive oxygen species (ROS), low motility or abnormal morphology.
However, these systems have limitations in samples with very low sperm concentrations or severely reduced motility, as their operation depends on the sperm’s ability to actively move through the microchannels.
Further information
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