Sperm cryopreservation may enhance fertilization

Sperm cryopreservation does not adversely affect hyaluronan binding, an apparently critical step in fertilization, and may even modestly enhance the process, according to a study of 36 specimens conducted by Stanford University investigators. They reported yesterday that cryopreservation increased overall hyaluronan binding rates by a mean of 9% (p=.002).

"Hyaluronan binding has been described as a marker of sperm maturity and, as such, immature sperm may not be able to survive the freeze-thaw process as well as mature sperm," explained Stewart McCallum, MD, assistant professor of urology at Stanford. "Alternatively, the media used to prepare the sperm for cryopreservation may have played a role in hyaluronan binding."

Whatever the reason for the increase, the results bode well for men considering cryopreservation of sperm. Chief among them are patients about to undergo radiation treatment or chemotherapy for cancer, many of whom bank sperm prior to their therapy.

The ability of sperm to bind hyaluronan, the main component of the oocyte cumulus matrix, is characteristic of the sperm plasma membrane. It has been shown to correlate with markers of sperm maturity.

Specimens were collected prospectively from men who presented for semen analysis. Each specimen underwent standard analysis and an assay for hyaluronan binding in the fresh and frozen/thawed states.

Twenty-nine specimens maintained sperm motility adequate for hyaluronan binding analysis. While binding rates increased somewhat, there was no apparent correlation between hyaluronan binding and parameters of the semen analysis.