Pentoxifylline-supplemented cryoprotectant improves human sperm motility after cryopreservation.

In this study, human spermatozoa obtained from donors (n = 15) with normal semen characteristics were cryopreserved in human sperm preservation medium, supplemented with the phosphodiesterase inhibitor pentoxifylline at concentrations of 0, 1, 3 and 10 mM. The effect of pentoxifylline on cryopreserved spermatozoa was determined by monitoring changes in sperm motility and acrosome morphology by labelling the spermatozoa with fluorescein-conjugated concanavalin A lectin. Cryoprotectant supplemented with 1 mM pentoxifylline was found to improve post-thaw progressive motility from 15.3 +/- 2.4 (control) to 23.1 +/- 3.8% (P < 0.01), and total motility from 27.4 +/- 3.3 (control) to 38.2 +/- 3.9% (P < 0.05) without reducing the percentage of spermatozoa with normal acrosomal regions, and so appears useful for cryopreservation purposes. The beneficial effects of 1 mM pentoxifylline on sperm motility were shown to be maintained post-thaw over a 6 h time course. Cryoprotectant supplemented with 3 mM pentoxifylline was found to improve only post-thaw progressive motility, from 15.3 +/- 2.4 (control) to 20.7 +/- 3.0% (P < 0.05). However, cryopreservation in the presence of 10 mM pentoxifylline was found to have a significantly (P < 0.01) detrimental effect on acrosome morphology post-thaw, reducing it from 29.0 +/- 2.0 (control) to 21.0 +/- 2.4% without affecting sperm motility. This suggests that assessment of the acrosomal region may indicate subtle deleterious effects of cryoprotectant supplements that cannot be determined from post-thaw motility assessments alone. These findings differ from previous studies in that a lower concentration of pentoxifylline (1 mM) was found to be optimal for cryopreservation purposes.