Hyaluronan and Sperm Selection for ICSI
Intracytoplasmic Sperm Injection (ICSI) is a specialized form of in-vitro fertilization (IVF) that can be used to treat many types of male fertility problems. During the ICSI process a single sperm is selected for injecting into an egg based on whether it looks normal (its morphology) and how it moves (its motility).
ICSI is frequently used in situations where there are concerns about sperm quality such as where there is a high percentage of sperm that are abnormally shaped (usually ≥ 95%). Therefore, a question that we are frequently asked in such situations is "How do you know that the sperm you are injecting is normal?" This is a good question, as using sperm for fertilization that have abnormal/damaged genetic material (DNA) can lead to poor fertilization results and poor embryo development.
When we look down a microscope at live sperm that we are going to use for fertilization, no matter how powerful the microscope is, we cannot see what is happening inside sperm such as whether the DNA is damaged/abnormal. In other words when looking down a microscope sperm with damaged DNA cannot be reliably identified/avoided based solely on appearance. Consequently, recent research has focused on approaches to selecting sperm for fertilization that have normal DNA.
Hyaluronan (HA) and Normal Fertilization
A substance called Hyaluronan (HA) is a component of one step during natural sperm selection. Researchers have found that sperm that bind to HA have reduced levels of abnormal DNA and genetic errors (DNA fragmentation and aneuploidy). During natural fertilization the sperm has to bind to a cluster of cells around the egg called the cumulus. Cumulus cells are rich in HA and mature sperm have receptors for HA. Therefore, sperm that are immature are less likely to be able to progress to the next step in the natural selection/fertilization process, and usually only mature sperm are able to fertilize an egg naturally.
Hyaluronan (HA) and Sperm Selection for ICSI
By exposing sperm to HA prior to ICSI we now have a greater ability to select sperm for fertilization that are mature and have the best DNA. As the healthiest sperm bind to the HA we are able to isolate/select them for injecting into the egg. Circumstances where HA-ICSI may be helpful for sperm selection include;
- Where there is high sperm DNA fragmentation
- If during previous IVF there were low fertilisation rates and/or poor embryo development
- If there is recurrent IVF failure or unexplained recurrent pregnancy loss
It should be noted that sperm needs to be motile (swimming) in order to be suitable for this process. There is an additional fee of $250 for the procedure.
If you would like to obtain references to research in this area or have any questions please feel free to talk to your Bubtree fertility specialist and/or scientist.