A discovery that oxidation causes damage to sperm has led to work on a chemical male contraceptive that can block sexually transmitted infections, and a new technique to address male infertility.
Credit: iStockPhoto
SYDNEY: Although their apparently healthy sperm may swim like tiny Olympians, some men can still suffer from infertility if their sex cells lack a crucial 'chaperone' protein, researchers have found.
This protein is responsible for transporting receptors to the surface of the cell, enabling sperm to recognise and bind to a female egg, and is largely absent in infertile patients. By understanding what activates this protein, researchers could develop new types of contraceptives.
“One in 20 men are infertile,” said lead researcher John Aitken, a reproductive biologist from the University of Newcastle in New South Wales. “Superficially everything about the sperm they produce looks good. They seem to move okay, they just can’t recognise the egg.”
Getting receptors to the cell surface key
On their journey through the female reproductive tract, a sperm cell passes by thousands of cells in search of a desired egg, which it must recognise and latch onto when the time is right.
“Spermatozoa hide away their egg receptors until they approach the egg and are ready to initiate fertilisation,” said Aitken. “They must recognise the egg, bind tenaciously to it, and then initiate the complex cascade of events that culminate in fertilisation.”
It has been previously suggested that individual receptors are needed to perform this function, but Aitken said studies have shown redundancies in these receptors – if one doesn’t work another will simply step in to do the job.
Infertile men have all the necessary receptors, said Aitken, but they seem to lack the chaperone protein – known as HSP2A – which is responsible for transporting the egg-finding receptors across the cell’s membrane to its outer surface.
How the sperm stacks up
Aitken and his team compared the sperm of infertile and fertile patients, analysing their protein structures. They found that levels of the chaperone protein were present in far lower concentrations in the sperm from infertile patients.
While there might not be any direct therapeutic benefit from this research in terms of treating infertility, Aitken said improved insight into what activates this protein might clarify the origins of male infertility.
Furthermore, by defining essential pathways in the physiology of sperm, and particularly sperm-egg binding, researchers could develop new types of contraceptives – an area of research where Aitken’s Australian-based team is making headway.
Trust me baby - I took the
Trust me baby - I took the pill.