What is the maximal timeframe between sperm acquisition to sperm cryopreservation, in different "culture" conditions?

Most of the literature about postmortem sperm retrieval (PMSR) deals with the controversies surrounding ethical and legal aspects, while the optimal time interval between the death and viable sperm acquisition is indefinite. In an attempt to aid fertility specialists, while counseling whether to pursue and adopt PMSR, we aim to explore the maximal time frame from ejaculated sperm acquisition to sperm cryopreservation in different "culture" conditions, observations that might be extrapolated to PMSR requests.

Five healthy men with normal semen analysis were enrolled. The sperm specimen from each man was diluted to 6.5 mL. After extracting 0.5 mL for cryopreservation, the remaining 6 mL were divided into three tubes: one was maintained in room temperature (23-25 °C), the second in an incubator (37 °C), and the third in a refrigerator (4 °C). Thereafter, every day, a 0.5 mL of each sample was extracted, examined, and cryopreserved. A week later, all the cryopreserved samples were thawed and tested for sperm motility and viability.

While at room temperature, frozen/thawed sperm were still motile (6.5%) and viable (9.9%) up to 96 h; those maintained in the refrigerator, following freezing/thawing were immotile already at 48 h in culture, but still viable (6.0%) up to 72 h in culture. Those maintained in the incubator demonstrated the worse results with negligible motility (1.5%) and viability (3.7%) following freezing/thawing, already after 48 h in culture.

The timeframe cut-off between ejaculated sperm acquisition and cryopreservation should be 72 h, unless sperm was maintained at room temperature, where it might be longer. It would be prudent to check for sperm vitality prior to freezing in cases where only immotile sperms are present.