In order for a sperm to transfer the hereditary material stored in the head part of the sperm to the egg, the acrosome part undergoes a transformation. This transformation is called the acrosomal reaction. The acrosome reaction must occur at the right place and time. The right place is the immediate environment of the egg cell. The right time: when the sperm passes through the layers surrounding the egg cell. It also follows that if, for some reason, the acrosomal reaction takes place elsewhere, earlier or not at all, fertilisation does not occur.
In the test, sperm are isolated from a fresh semen sample and then artificially created to create the conditions that the sperm will encounter as they migrate through the female reproductive tract. This is the so-called capacitation phase, which precedes the acrosome reaction. During capacitation, the sperm prepare for the acrosome reaction. After the capacitation phase, the samples are split in two. One half of the samples is not treated with any substance (unstimulated), the other half is treated (stimulated) with a substance that artificially induces the acrosome reaction in the sperm.
If the proportion of spermatozoa with a premature acrosome reaction is high, or if the induction results in a low number of sperm with an acrosome reaction, then insemination and in vitro fertilisation (IVF) will not be successful as assisted reproductive techniques. Unfortunately, to date, no treatment has been described that can be used to specifically restore the susceptibility to an insufficient acrosomal response in the male reproductive tract. When the cause of infertility is proven to be an inadequate acrosomal response, in vitro assisted reproduction methods should be used instead of treatment. Of these, the methods involving intracytoplasmic injection are also the most successful (ICSI and PICSI).