Scientists have found that the DNA of sperm taken from the testicles of infertile men was as good as that of ejaculated sperm of fertile men.

The research may explain a major cause of male infertility and open up the possibility of using sperm taken directly from the testicles to overcome infertility among males. The research was presented at the European Association of Urology Congress in Barcelona. UK-based scientists took sperm samples from the testicles of 63 infertile men and matched them with ejaculated sperm samples produced by the same men.

These infertile men had failed previous fertility treatment (intracytoplasmic sperm injection or ICSI). The scientists also examined the sperm for two types of DNA strand breaks (single and double strand breaks) each in the testicular and ejaculated sperm.

Infertility is a major public health issue. One couple in six is infertile across Europe, with male infertility now being the biggest cause in couples seeking treatment. Sperm DNA damage is known to be a major cause of male infertility and reduces a couple's chances of having a family. This study shows that on the journey from the testicles along the long series of ducts before ejaculation, sperm DNA can suffer major damage, some of which is due to oxidative stress.

According to researcher Jonathan Ramsay, Consultant Urologist, Imperial College, London, "When we looked at ejaculated sperm, we found that the extent of sperm DNA damage was much higher in infertile men than infertile men, with roughly 15 per cent infertile men, but 40 per cent in infertile men."

"It wasn't a surprise to see greater DNA damage in ejaculates of infertile men. What we didn't expect was the consistency in these results when we looked at sperm taken directly from the testicles of infertile men; we found that it was of similar quality to that of ejaculated, fertile sperm."

Explaining further, Ramsay said: “The majority of DNA damage caused in transit from testicles to ejaculate is caused by oxidative stress, which causes DNA single but not double-strand breaks."

"This occurs when the sperm is subjected to poor lifestyle habits such as poor diet, using a laptop all day or smoking. Diseases such as Crohn's disease and Type 2 diabetes are also caused by oxidative stress."

Professor Sheena Lewis, Emeritus Professor Queens University, Belfast and founder of ExamenLab, said: "What this means is that the DNA in sperm from the testicles of infertile men are better quality than sperm from their ejaculates. This opens the way to taking sperm directly from the testes of men who have highly fragmented ejaculated DNA and failed cycles of treatment and trying to achieve fertility with testicular sperm."

"We need to be aware of what this study does and doesn't show. We can't yet prove that this sperm DNA damage is the main cause of male infertility or ART failure in these men, or that using testicular sperm directly would help improve their chance of getting pregnant, but the work certainly points in that direction," said Lewis.

Commenting on the findings, Professor Maarten Albersen, member of EAU Scientific Congress Office, said: "Couples who face an unfulfilled child wish due to male infertility often have to resort to assisted reproductive techniques such as in-vitro fertilization (IVF) or intracytoplasmic sperm injections (ICSI). Success rates of these techniques per cycle are rather low and various factors influence these rates."

"In this study, a group from London shows that DNA integrity in infertile men is higher in testicular sperm than in ejaculated sperm. As DNA integrity is believed to play a role in fertilization rates in assisted reproduction, these results may assist in the decision-making whether or not to resort to testicular biopsy/testicular sperm aspiration rather than using ejaculated sperm to enhance success rates of assisted fertilization in infertile men with signs of DNA damage."

"However, improved fertilisation rates and baby-take home rates would need to be confirmed before adopting this alternate strategy," he said.