Sperm capacitation is, after all, a prerequisite for both partial and complete acrosome reaction

Abstract

The acrosome reaction (AR)^an essential step in mammalian fertilization^can occur, according to the consensus, only in capacitated spermatozoa. In apparent contrast, recent reports have demonstrated that human spermatozoa incubated in vitro in an albumin-free medium and therefore believed to be noncapacitated, do undergo the AR. With the aim of determining unequivocally whether or not capacitation is required for the AR and whether albumin is essential for capacitation, we compared the potential to undergo partial and complete AR (induced by phorbol myristate ester or by the Ca 2+ ionophore A23187) between human spermatozoa incubated in a capacitating medium, albumin-free medium, and non-capacitating medium. The results clearly demonstrate that capacitation is, after all, a prerequisite for both partial and complete AR. Albumin, on the other hand, is essential only for acquiring the capacity to undergo complete, not partial AR.z 1998 Federation of European Biochemical Societies.

Human sperm chemotaxis depends on critical levels of reactive oxygen species

“…As previously recommended by the Andrology Special Interest Group of the European Society for Human Reproduction and Embryology, we used the calcium ionophore A23187 to stimulate the acrosome reaction (14) only in capacitated spermatozoa (15,16).…”

Le chimiotactisme des spermatozoïdes a-t-il un rôle dans la fécondation?

“…L'obtention de ces souspopulations enrichie et non enrichie a conduit la d6termination que l'6tat capacit6 des spermatozoides humains n'6tait pas statique mais plutSt transitoire avec une dur6e de vie de 50 240 minutes in vitro, et qu'il existait un processus continu de remplacement des spermatozoides capacit6s au sein d'une population de spermatozoides [21]. La cons6quence de ce remplacement continu des spermatozo~des capacit6s est l'existence d'une population h4t6-rog6ne de spermatozoides, qui comprend des cellules qui n'ont pas encore d6but6 le processus de capacitation, des cellules ~ diverses 6tapes de la capacitation, des cellules pleinement capacit6es, des cellules post-capacit6es et des cellules ayant fait leur r4action acrosomique [22,23]. L'association entre sensibilit6 au chimiotactisme et 6tat capacit6 repose sur a) la similarit6 des pourcentages de spermatozoides chimiotactiques et capacit6s dans une population donn4e de spermatozoides, b) la similarit6 de la cin6tique de remplacement des spermatozoides capacit6s et chimiotactiques, et c) le fait qu'une d6pl6tion d61ib6r6e en spermatozo~des capacit6s entraine une perte totale du chimiotactisme et, vice versa, une d6pl6tion en spermatozoides chimiotactiques entraine une d6pl6tion des spermatozo~des capacit6s [21].…”

Mammalian sperm chemotaxis and its association with capacitation

“…The spermatozoa that underwent these processes, termed capacitated spermatozoa, are endowed with a number of abilities that are essential for fertilization: (1) to be released from the oviductal sperm reservoir (see below), (2) to penetrate the cumulus layer that surrounds the egg, (3) to bind to the sperm receptor on the egg coat, and (4) to undergo the acrosome reaction that permits sperm penetration of the egg coat and fusion with the egg [Jaiswal and Eisenbach, 1999]. Cells that are partially capacitated can only undergo a partial acrosome reaction [Jaiswal et al, 1998[Jaiswal et al, , 1999a.…”

“…The availability of these enriched and deficient subpopulations led to the determination that the capacitated state of a human spermatozoon is not static, but rather transient with a life span of 50-240 min in vitro and that there is a continuous process of replacement of capacitated spermatozoa within a sperm population [Cohen-Dayag et al, 1995]. The consequence of this continuous replacement of capacitated spermatozoa is a heterogeneous sperm population, which includes cells that have not yet started the process of capacitation, cells at various stages of capacitation, fully capacitated cells, postcapacitated cells, and acrosome-reacted cells [Jaiswal et al, 1998[Jaiswal et al, , 1999a. The association between chemotactic responsiveness and the capacitated state relies on (1) the similarity of the percentages of chemotactic and capacitated spermatozoa in a given sperm population; (2) the similarity of the kinetics of replacement of capacitated and chemotactic spermatozoa; and (3) the fact that deliberate depletion of capacitated spermatozoa results in total loss of chemotaxis and, vice versa, depletion of chemotactic spermatozoa results in depletion of capacitated spermatozoa [CohenDayag et al, 1995].…”