Predictors of Sperm Cryopreservation Success

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DENVER—Raw semen total motile count (TMC) is the best predictor of sperm motility and TMC after cryopreservation of sperm, according to study findings presented at the American Society of Reproductive Medicine annual meeting.

Researchers at the University of Washington in Seattle found that pentoxifylline (PX) and, to a lesser extent, slow-freezing protocols and preparation medium (HTF, HamsF10) may benefit men undergoing cryopreservation. The findings suggest that identification of optimal protocols for cryopreservation may be possible in selected patients.

“There are a few other papers in the literature that have looked at this issue [in men],” said study investigator James Hotaling, MD, MS, a urology resident.

Most studies have been done with animals, such as cattle and horses. “Nobody has really ever gone back to see if there are specific types of men that may benefit from one protocol versus another protocol,” he said.

Previously published data showed that mathematical modeling could help predict cryopreservation success. Modifiable factors for cryopreservation success and specific regimens for sub-populations of men have not been identified, however.

Dr. Hotaling and his colleagues reviewed laboratory data from 423 men attending their male infertility laboratory from 1994 to 2009. The men provided 1,000 semen samples that underwent cryopreservation and at least one test thaw. The researchers analyzed variables such as sperm concentration, motility (total percentage), sperm motility enhancement, preparation medium (HTF, Hams F10), and freezing rate (rapid and slow).

Raw semen TMC was the strongest predictor of sperm motility and TMC in thawed semen specimens. The percentage of recovery of TMC and motility after test-thaws increased significantly by 65% and 4% for each quartile of improvement in raw TMC. After controlling for raw semen parameters, PX and PX/DOA yielded a significant 76% and 73.7% improvement in motile sperm recovery. The use of Hams F10 compared with HTF demonstrated minor improvements in motile sperm recovery. The same was true for slow versus rapid freezing.

“I think these findings are clinically relevant,” Dr. Hotaling told Renal & Urology News. “If you can identify some simple parameters in terms of the different media that are used that are of equivalent costs, and it is simply using one versus the other, then those can make a highly significant difference.  This can make a big difference, especially for oncology patients who are banking sperm before treatment with chemotherapy for testes cancer and other types of malignancies. If you can optimize their yield after that then it makes a big difference for them.”

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