All semen samples have some sperm that have entered apoptosis, as this is a natural physiological process. However, in certain cases we find a percentage of apoptosis above the range of normality, which could eventually impact on the generation of embryos and their subsequent viability.
Apoptosis is commonly known as cellular suicide, and applied to seminal samples refers to those sperm whose death is imminent. This is a very important mechanism in nature, being necessary for the maintenance of cellular balance in our body. Basically, when a cell in our body is not capable of performing its function and becomes a burden to the rest of the system, it enters a process of programmed and "voluntary" degradation. That is, far from prioritizing its individuality, the cell will seek the collective benefit.
In the case of spermatozoa, those that detect in themselves a failure that produces a suboptimal functioning enter into apoptosis. Although these spermatozoa would not normally be able to fertilize an oocyte naturally, in assisted reproduction, given that spermatozoa in the process of apoptosis are indistinguishable from the rest under the microscope, they could be selected to fertilize an oocyte. In this case, the probability of generating a good embryo that will lead to a viable pregnancy and the birth of a baby is very low.
In this context, MACS should be used whenever a higher than normal level of apoptosis is detected in a semen sample, in order to avoid spermatozoa with cell damage. 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.
In this way, MACS will allow us to make a previous selection of spermatozoa with greater fertilizing capacity and, therefore, discard those that are not optimal, and thus increase the rate of fertilization and consequently, the pregnancy rate.
Obviously, it requires the necessary technology to measure apoptosis in the seminal sample, such as flow cytometry.