Sperm-oocyte interaction: studies on the kinetics of zona pellucida binding and acrosome reaction of human spermatozoa

Abstract

Successful sperm-oocyte interaction depends, among other things, on sperm capacitation, which is defined by acrosomal and motility alterations. In the study described here the authors evaluated different aspects of this gamete interaction in humans. Specifically, the authors studied (1) the relationship between the number of spermatozoa bound to the zona pellucida and sperm concentration and incubation period, (2) the capacitation status and kinetics of acrosome reaction among the zona-bound spermatozoa, and (3) the effect of human follicular fluid on the zona-binding potential and acrosome status of spermatozoa from different men. The results indicated a concentration of lo7 cells ml-' after 15 min of coincubation to be the optimum for zona binding. The number of sperm bound after 0, 3 and 5 h of incubation was the same. In addition, spermatozoa incubated for 3 or 5 h underwent the acrosome reaction (range 9-43'10) on the zona surface within 15 min of binding. The maximum percentage of acrosome-reacted spermatozoa was reached after 60 min of binding. Follicular fluid affected the sperm populations selectively, since it did not influence zona binding capacity in all cases. The data enhances the authors' understanding of critical events occurring before fertilization.

Elevated and Sustained Intracellular Calcium Signalling Is Necessary for Efficacious Induction of the Human Sperm Acrosome Reaction

“…We found no association between the PPN-mediated AR induction and IVF fertilisation rate, which is in keeping with the analysis of the studies examining the predictive potential of P4-mediated AR [ 44 ]. The acrosome-reacted and acrosome-intact human sperm bind the ZP [ 80 , 81 ]; the solubilized ZP increases in the [Ca 2+ ]i [ 82 , 83 , 84 ] and the AR is triggered by the intact and solubilized ZP [ 5 , 82 , 85 , 86 ]. Therefore, as has been suggested for the mouse sperm [ 11 , 67 ], the nature of the trigger may not be of great significance but, rather, the fact that the human sperm possess the potential to react.…”

Protein Phosphatases Decrease Their Activity during Capacitation: A New Requirement for This Event

“…At the end of each incubation time, sperm aliquots were washed twice in PBS (137 mM NaCl, 2.7 mM KCl, 1.5 mM KH 2 PO 4 , 4.3 mM Na 2 HPO 4 , pH 7.4) by centrifuging at 800×g for 5 min. The resulting washed sperm pellet was resuspended in homogenization buffer (50 mM HEPES, 10% glycerol, pH 7.4) at a concentration of 30×10 6 cells/ml [28], [29] and maintained at −20°C until use.…”

Identification of Sialyl-Lewis(x)-Interacting Protein on Human Spermatozoa

“…When human ZP2 is absent from these mice, human spermatozoa rarely bind to the oocytes ( Avella et al, 2014 ). It is noted that the human spermatozoa take 180–240 min to bind onto the mouse ZP containing human ZP2 ( Baibakov et al, 2012 ), which was much longer than 15–60 min for binding to human ZP ( Plachot et al, 1986 ; Morales et al, 1994 ). The slower binding kinetics could be due to inappropriate glycosylation of human ZP2 in the mice, consistent with differential interaction of human spermatozoa to recombinant human ZP2 and native ZP2 with different glycosylation ( Chiu et al, 2014 ; Gupta, 2021 ).…”