Last week you could read in the blog about density gradient centrifugation. This is a method for separating healthy sperm from defective sperm. As mentioned in that blog post, this method can significantly improve the quality of the sperm, but it is still not possible to achieve 100% separation. This is why new methods are constantly being tested to improve sperm quality. One of these alternative methods is called "Magnetic Activated Cell Sorting", or MACS for short.

Who should be screened?

MACS, like density gradient centrifugation, is suitable for removing dead sperm cells. Dead cells are called apoptotic cells in medicine. Some men are healthy in themselves, but have a relatively high number of apoptotic cells in their sperm due to defective spermatogenesis. If these sperm fertilise the egg, the embryo usually develops abnormally. Often the embryo is not viable at all and a miscarriage occurs.

You can find out if you are one of these women by having a spermiogram. There is also a blog article about this on this page.

Why is sperm sorting needed in addition to IVF?

To answer this, you need to think about what exactly happens in IVF. An egg from the woman's ovary is fertilised with the man's sperm in a laboratory. The embryos are then grown in a culture medium. If the first cell divisions are successful, the embryo can be transferred to the uterus. This is sufficient if, for example, the sperm do not move sufficiently. They would not make it to the egg naturally, so they take a shortcut through IVF.

However, the sperm are not sorted because their motility is too low. The aim is to remove apoptotic cells. These would be very unlikely to fertilise naturally, but IFV would. This is particularly dangerous for men who have a high number of apoptotic sperm. IVF would make fertilisation with a defective sperm even more likely. This means that the risk of miscarriage is also greatly increased.

So if you are going to have artificial insemination, you should make sure that you only use healthy sperm, otherwise you will have wasted your time.

How does MACS work?

All cells in the human body have different structures on the outside of their surface. These are used to communicate with other cells. For example, cells that have been attacked by a virus have special structures on their surface so that cells of the immune system can recognise them. This principle also applies to apoptotic sperm cells. They produce a substance called phosphatidylserine. This is only found on the surface of dead sperm; healthy sperm do not have this surface structure.

Under normal conditions, the repair protein annexin V binds very strongly to phosphatidylserine. This is used in the MACS technique. Annexin V can be artificially tagged with magnetic labels. The sperm and the magnetic annexin V are then brought together. The annexin is given time to bind to all sperm with phosphatidylserine. All sperm where binding has taken place are now annexin positive. A magnetic column can now be placed in the sample and all positive sperm will adhere to it.

The removed positive sperm can then be stained to see if and to what extent the genetic information is fragmented or damaged.

MACS compared to other techniques

As mentioned above, the MACS technique was developed in addition to existing methods such as density gradient centrifugation. The latter tends to be the standard method as it is cheaper and somewhat simpler. However, sperm sorting with the magnetic technique appears to be much more efficient. For example, in a series of experiments at the University of Ulm, sperm from 55 patients were examined using the two techniques mentioned above. Before separation, the fragmented, apoptotic sperm were stained and their proportion determined. After separation, the whole process was repeated. In this way, the native proportion of apoptotic cells can be compared with the proportion remaining after sorting. The aim of the separation methods is, of course, to reduce the proportion of apoptotic cells as much as possible.

In the case of density gradient centrifugation, the native proportion of apoptotic spermatozoa averaged 15.96%. Centrifugation reduced this to around 11.83%. This is a significant improvement in sperm quality.

In the samples used for the MACS technique, the average native value was 17.6%. After separation it was only 11.29%.

Overall, MACS can reduce apoptotic sperm by about 10% more than centrifugation. For this reason, it makes sense to use the MACS technique in addition to the normal standard methods. However, even with a combination of both techniques, it is never possible to obtain 100% pure sperm.

Doctor's procedure

For you as a patient, it doesn't really matter which techniques are used in the lab. The normal procedure has been described many times on this blog, but if you want to know exactly what happens, have a look at last week's post.

Basically, all you have to do is make an appointment with the doctor of your choice and give him or her a sample of your sperm. This sample is usually taken at the clinic because it is easier to ensure that it is stored properly. The doctor's surgery or clinic will then send your sample to the laboratory and inform you as soon as the results are available. The optimised sperm can then be frozen. When IVF is due, the sperm can be thawed and used again.

As you can see, researchers in Europe and around the world are constantly improving or adding to existing techniques. Although there is never a guarantee, the chances of using healthy sperm for IVF are much better with these methods. This reduces the risk of disabilities and miscarriages. So if you are still at the beginning of your IVF journey, it is worth having a spermiogram. If the male partner is the problem, it is likely that MACS or other sperm sorting methods can be used to avoid this.