Traditionally, semen quality is evaluated in a microscope counting how many sperm cells there are, how well they swim and whether they are malformed or not. However, these parameters are not particularly good at predicting how fertile a man is.

Researchers from the Department of Growth and Reproduction, Copenhagen University Hospital, have therefore been looking for another method to assess how good sperm cells are to fertilize an egg. To penetrate an egg, sperm cells must pass through a rigid barrier (the egg coat or zona pellucida) surrounding the egg. To facilitate this, sperm cells have an acrosome, which releases enzymes that can break down the barrier. The acrosome can be compared to a hat on top of the sperm head that only can be removed when it meets an egg. The researchers have developed a new method that easily can estimate the number of sperm cells with an intact acrosome, and therefore have the potential to fertilize an egg. 

Examination of semen samples from more than 230 men showed that over half of the sperm cells had already lost their acrosome, just after the samples were made. In other words, less than half of the sperm cells had the ability to fertilize an egg. Indeed, the number of acrosome-intact sperm cells was found to be good in predicting the fertility of men. Men who became fathers by natural intercourse had significantly more sperm cells with an intact acrosome than men in fertility treatment.

Senior researcher Kristian Almstrup, who has been responsible for the study, just published in the journal Human Reproduction, says, "The method allows us to test the fertility of a man in a new way. If a man has few sperm cells with an intact acrosome, then the couple will probably benefit the most from a treatment where a sperm cell is injected directly into the egg. "

Senior Researcher, Kristian Almstrup: kristian.almstrup@regionh.dk. Tel. 35456639/31668002.