Removing the tiny cap of potent enzymes from human sperm prior to the common assisted-fertility treatment, ICSI, could boost the efficiency of this reproductive technology, new research suggests.Intracytoplasmic sperm injection, where a whole sperm is injected straight into an egg cell, has become a popular option for infertile couples for whom traditional IVF has failed. But the success rate is still low. “In most infertility clinics, only three of 10 couples bring babies home after ICSI,” says Ryuzo Yanagimachi at the University of Hawaii School of Medicine, US.Yanagimachi and his colleague Kazuto Morozumi, also at the school, wanted to assess the potential hazards of sperm cap enzymes on developing mouse embryos. This is because, with natural fertilisations, the chemicals in this cap, or acrosome, would never enter the egg cell: the powerful hydrolysing enzymes are used to break down the egg’s cell wall. For certain animals – such as the golden hamster, which has a particularly large acrosome – ICSI always fails unless the cap is removed.
