Abstract
The objective of the present study was to investigate the effects of the direct addition of pentoxifylline (PF) to the ejaculates of men with poor sperm quality before freezing on post-thaw sperm motility, viability, acrosome integrity, and agonist-induced acrosome reaction. Semen specimens from 16 infertile men with impaired sperm count and motility (oligoasthenozoospermia) were divided into two equal aliquots: one received no treatment (control) while the other was incubated with 5 mM PF (treated). Both aliquots were cryopreserved by the liquid nitrogen vapor method. Motility was assessed according to WHO criteria. Acrosome integrity and spontaneous and calcium ionophore-induced acrosome reactions were assessed with fluorescein isothiocyanate-conjugated peanut agglutinin combined with a supra-vital dye (Hoechst-33258). Cryopreservation impaired sperm motility (percentage reduction: 87.4 (interquartile range, IQ: 70.3-92.9) vs 89.1 (IQ: 72.7-96.0%)), viability (25.9 (IQ: 22.2-29.7) vs 25.6 (IQ: 19.7-40.3%)) and acrosome integrity (18.9 (IQ: 5.4-38.9) vs 26.8 (IQ: 0.0-45.2%)) to the same extent in both treated and control aliquots. However, PF treatment before freezing improved the acrosome reaction to ionophore challenge test scores in cryopreserved spermatozoa (9.7 (IQ: 6.6-19.7) vs 4.8 (IQ: 0.5-6.8%); P = 0.002). These data show that pre-freeze treatment of poor quality human sperm with pentoxifylline did not improve post-thaw motility or viability nor did it prevent acrosomal loss during the freeze-thaw process. However, PF, as used, improved the ability of thawed spermatozoa to undergo the acrosome reaction in response to calcium ionophore. The present data indicate that treatment of poor quality human sperm with PF may enhance post-thaw sperm fertilizing ability.
Highlights
Cryopreservation impairs sperm fertilizing ability by decreasing sperm motility and motion characteristics, penetration into the cervical mucus and into zona-free hamster eggs, viability, membrane integrity and acrosome structure, and activity of acrosome protease and acrosin [1,2,3,4]
We examined if the benefits of PF for freezing normal sperm can be extrapolated to poor quality sperm obtained from oligoasthenozoospermic men
Our results indicated that the cryopreservation process was detrimental to sperm motility and viability, irrespective of whether or not spermatozoa had been treated with PF before freezing, corroborating previous reports [12]
Summary
Cryopreservation impairs sperm fertilizing ability by decreasing sperm motility and motion characteristics, penetration into the cervical mucus and into zona-free hamster eggs, viability, membrane integrity and acrosome structure, and activity of acrosome protease and acrosin [1,2,3,4]. Treatments that increase intracellular cAMP concentrations often cause an increase in sperm motility and kinematics as well as in the agonist-induced acrosome reaction [9] and fertilization rates [5,6]. It has been reported that pre-freeze sperm treatment with PF decreases acrosome loss during the freeze-thaw process and increases the post-thaw agonist-induced acrosome reaction rate in normal semen [12]. This strategy may be clinically useful because it can improve the fertilizing potential of cryopreserved human semen. We investigated if the beneficial effects of the addition of PF directly to the seminal plasma before freezing, as seen in normal human semen [12], can be demonstrated in poor quality specimens, such as those obtained from infertile men with decreased sperm count and motility (oligoasthenozoospermia)
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