Scientists studying male infertility have found lifestyle factors such as smoking and high fat diets could be the reason an important molecular chaperone protein is absent in infertile men.

Male factor infertility is a growing health issue with 1 in 20 Australian men classified infertile and very little knowledge behind what is causing such a high prevalence in our society.

The study, conducted by researchers at the University of Newcastle's School of Environmental and Life Sciences, showed that sperm placed in an environment of oxidative stress may be unable to complete fertilisation.

While there have been previous studies on the link between oxidative stress and male-factor infertility, this is the first study to investigate the impact it has on the ability of the sperm to infiltrate the ovum.

Associate Professor Brett Nixon carried out the research alongside Professor John Aitken and PhD student Elizabeth Bromfield by testing sperm samples from fertile and infertile men.

"The aim of this study was to investigate how sperm recognise the eggs and initiate fertilisation. What we found was a molecular chaperone protein that is capable of regulating the presentation of egg receptors on the sperm surface and thus directing sperm-egg interactions" said Professor Nixon.

"In a subset of infertile men, we found that this molecular chaperone was under-represented or completely absent, which appears to be impacting sperm fertilising potential during the reproductive process.

"We are currently investigating whether the reason this protein is missing is the result of damage caused from excessive oxidative stress," he said.

Professor Nixon said oxidative stress occurs in the testes and damages sperm, compromising the ability to reproduce.

"Oxidative stress occurs when the body has more Reactive Oxygen Species (ROS), or free radicals, than it can deal with. This build-up of ROS is generally thought to be the result of a variety of environmental and lifestyle factors, including advanced age and too much smoking," said Professor Nixon.

"Sperm are particularly vulnerable to oxidative stress which can cause damage to the membrane of the cell and to its DNA," he said.

This study was undertaken on human test subjects and has been a culmination of almost 10 years or research in the field of male infertility, the majority of previous research was undertaken on mice models.

"The reasons behind male infertility are relatively unexplored so it is incredibly important that we continue our studies in this area to increase our knowledge and understanding of this widespread issue," said Professor Nixon.

"By continuing research on sperm cells, not only will we gain a better understanding of male infertility, but it will also be key to helping develop a male centred contraceptive in the future," he said.