Male infertility can be the result of sperm missing just one vital protein, which is necessary to activate the egg when the sperm fuses with it. But injecting that egg with the missing protein can “kick-start” the vital processes of embryo development, and dramatically increase the chances of a successful pregnancy.

These are the findings of a new study by a team at Cardiff University in the UK who write about their work in a paper being published in the journal Fertility and Sterility. They suggest the findings strengthen the case for the potential use of the protein in treating male infertility.

Professors Tony Lai and Karl Swann led the research team at the University’s Institute of Molecular and Experimental Medicine, where they discovered how during the fertilization process, sperm transfers a vital protein called PLC-zeta (PLCz), to the egg. This protein activates the egg, in effect initiating the biological processes of early embryo development.

They also found that a defective PLCz protein, which is linked to some forms of male infertility, doesn’t fertilize the egg, and treating such unfertilized eggs with an active form of the protein, restores egg activation.

They prepared the active form of human sperm PLCz protein in the lab.

Lai says in a press statement, their study establishes that “this one sperm protein, PLCz, is absolutely critical at the point where life begins”.

“We know that some men are infertile because their sperm fail to activate eggs. Even though their sperm fuses with the egg, nothing happens. These sperm may lack a proper functioning version of PLCz, which is essential to trigger the next stage in becoming pregnant,” he adds.

Lai explains that when they injected an unfertilized egg with the human PLCz they prepared in the lab, it responded “exactly as it should do at fertilization, resulting in successful embryo development to the blastocyst stage, vital to pregnancy success”.

The team points out that an important feature of their study is they used human sperm PLCz; previous studies showing such positive results had only been done in mice.

There is however, still a way to go before the protein can be used in clinical treatments:

“Whilst this was a lab experiment and our method could not be used in a fertility clinic in exactly the same way – there is potential to translate this advance into humans,” says Lai.

He suggests it will be possible to make human PLCz protein and “use it to stimulate egg activation in a completely natural way”. Lai also suggests it could help couples having IVF treatments “ultimately improve their chances of having a baby and treat male infertility”.

The research was funded by the Wellcome Trust.

Written by Catharine Paddock PhD