A method of short-term cryostorage and selection of viable sperm for use in the various assisted reproductive techniques.

The objective of this study was to determine if spermatozoa, following short-term cryostorage at 5 degrees C in Test-Yolk buffer (TYB; ZBL, Inc., Lexington, KY, USA), could be recovered and improved via the SpermPrep filtration method and to assess the possibly enhanced fertilizing capacity of the selected spermatozoa. Semen specimens from 20 men were collected, evaluated, diluted 1:1 (v/v) with TYB, divided into aliquots and cooled to 5 degrees C for 24 and 48 hr. Semen samples were assessed for volume, sperm count, percentage and grade of motility, percentage of morphologically normal spermatozoa and outcome of the sperm penetration assay (SPA). After storage, aliquots were rewarmed at 37 degrees C, centrifuged, and the pellet was resuspended in 1.0 ml of SpermPrep media (ZBL, Inc.). Following 15 min of incubation, the rewarmed spermatozoa were filtered via the SpermPrep I filtration column (ZBL, Inc.) and assessed accordingly. The results obtained in this study indicate that the short-term cryostorage procedure yielded spermatozoa of adequate qualitative characteristics when compared to the fresh spermatozoa. Furthermore, filtration of rewarmed specimens yielded spermatozoa of significantly higher qualitative characteristics and superior fertilizing capacity following a short-term cryostorage period in TYB when compared to fresh and rewarmed spermatozoa (p < 0.05). This method of short-term cryostorage in TYB and selection of superior spermatozoa via the SpermPrep filtration method could further enhance the fertilizing ability of patients who produce spermatozoa characterized by deficient capacitation, acrosome reaction and subsequent fertilization.