Test for motile sperm improves ICSI outcomes

By Sally Robertson, B.Sc.Jul 23 2012

Researchers have developed a new sperm test that could improve pregnancy rates among women treated with intracytoplasmic sperm injection (ICSI).

The polyvinylpyrrolidone (PVP) motility test enables motile versus immotile sperm to be selected for use in ICSI cycles.

Although successful fertilization and embryo development can occur with immotile sperm, the implantation rate is very low, say Tulay Irez (Yeni Yuzyil University, Istanbul, Turkey) and colleagues.

"For ICSI, the selection should not be random but rather take motility, morphology, and other markers of viability into consideration."

The artificial polymer PVP is routinely used during ICSI to facilitate handling of sperm. However, it has been found to cause sub-microscopic changes to sperm structure, damaging the sperm nucleus both in terms of shape and in the texture of chromatin.

In a study of 123 couples with male infertility, Irez and team separated sperm that was progressive or slightly motile during PVP incubation (PVP+) from sperm that was completely immotile during incubation (PVP-), before it was injected during ICSI.

As reported in Andrologia, the total number of embryos obtained was significantly higher among women in the PVP+ group compared with those in the PVP- group, at 4.52 versus 2.84.

The number of transferred embryos and grade 1 embryos was also significantly higher in the PVP+ group.

Furthermore, fifty (64%) of 78 women in the PVP+ group became pregnant, compared with only 12 (26%) of 45 women in the PVP- group.

"These data suggest that the presence of PVP positivity, in other words presence of sperm motility in PVP incubation, is a valuable predictor of success rate of ICSI procedure," writes the team.

Further analysis using aniline blue staining and a sperm chromatin decondensation test showed that PVP+ sperm had higher chromatin condensation and decondensation capacity than PVP- sperm.

"Sperm nuclear chromatin is in a highly condensed state prior to fertilization," explain the researchers. "In vitro decondensation occurs in the ooplasm and is essential for successful fertilization and the formation of male pronucleus and the zygote to occur," they add.

"The PVP motility test is a simple method that can help in the sperm selection process with a higher morphological normal embryo percentage and also a higher pregnancy rate," concludes the team.

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