Breakthrough weeds out dying sperm

ICSI is a technique to inject a sperm directly into an egg

Thousands of men who cannot father children because the vast majority of their sperm are faulty could be offered hope by a laboratory advance.

If the genetic information contained in the immature sperm, or germ cell, is faulty, the body will set in motion a process called apoptosis, which instructs it to die so it cannot pass on its faults.

In some men, when samples of testicular tissue containing the germ cells is taken, virtually all of them are dying in this way.

However, it may take some time for the apoptosis to take full effect, and scientists trying to select individual immature sperm to use in fertility treatments find it impossible to distinguish between those that are healthy and those about to die.

What we have done is given men with more than 90% frequency of apoptosis the same chance of ICSI as a normal man

Dr Jan Tesarik, Hospital Virgen del Rocio in Granada, Spain

Even dying sperm look exactly the same and can move around.

If the wrong type is pushed into the egg during a fertility technique known as ICSI, it will not go on to fertilise it, and the attempt will be wasted.

Good germ cells

Dr Jan Tesarik, working at the Hospital Virgen del Rocio in Granada, Spain, told the annual conference of the European Society for Human Reproduction and Development in Bologna he had found a way of helping doctors pick the good germ cells.

His "wait and see" policy involves placing samples in a culture containing growth factor chemicals and testosterone.

After just 24 hours, each type of cell had changed sufficiently to allow identification of those affected by apoptosis.

The healthy ones could then be removed and used in ICSI.

Although the study is at an early stage, four patients, each with well over 90% frequency of apoptosis among their immature sperm, were used to test the theory.

The results were promising, with two of the couples involved achieving pregnancy, one live birth - and in the other two cases, fertilisation of the egg was achieved after ICSI, although no pregnancy resulted.

Dr Tesarik told BBC News Online: "The idea was to put all these sperm into culture - the bad ones were much more obvious after just one day.

"Although there are no certainties in this kind of thing, what we have done is given men with more than 90% frequency of apoptosis the same chance of ICSI as a normal man, who has 10% to 15% apoptosis."