Acrosome‐reacted human sperm in insemination medium do not bind to the zona pellucida of human oocytes

Abstract

In the literature there is still confusion whether acrosome-reacted sperm in medium can initiate primary binding to human zona pellucida (ZP). The ability of acrosome-reacted sperm to bind to ZP in vitro can be deduced by measuring the acrosome reaction (AR) of ZP-bound sperm compared with sperm in medium after incubation under different conditions inhibiting the ZP-induced AR. Motile sperm from fertile men, normospermic men and infertile men diagnosed with disordered ZP-induced AR (DZPIAR) were selected by swim-up (2 x 10(6) in 1 mL medium) and incubated for 1-2 h with four oocytes from failed in vitro fertilization (IVF). The acrosome status of sperm was assessed using pisum sativum agglutinin labelled with fluorescein. The ZP-induced AR was inhibited in experiments using sperm from DZPIAR patients, hyper-osmotic medium (400 mOsm/kg) and medium containing soybean trypsin inhibitor (SBTI; 4 mg/mL). Pre-treatment with calcium ionophore was used to create a sperm population with elevated AR. In all experiments with factors inhibiting the ZP-induced AR, the AR was significantly lower for ZP-bound sperm compared with sperm in medium: DZPIAR patients 4% vs. 15%, hyper-osmotic medium 3% vs. 12%, SBTI 2% vs. 12% and SBTI 3% vs. 23% after treatment with calcium ionophore. In conclusion, acrosome-reacted sperm in vitro have significantly reduced, in fact probably zero ability to bind to the ZP.

A sperm GPI-anchored protein elicits sperm-cumulus cross-talk leading to the acrosome reaction

“…This notion is also consistent with the recent finding that human spermatozoa exposed to the cumulus mass, when compared with those spermatozoa cultured in medium alone, are more likely to be acrosome reacted in the absence of ZP [28]. These cumulus-induced acrosome reacted spermatozoa may not bind to the ZP of human oocytes [29] and may even die before reaching the ZP. However, their sacrifice may pave the way for other unreacted sperm to reach the ZP where they will undergo the conventional ZP-induced acrosome reaction to penetrate this second layer of egg investment.…”

Dynamic resolution of acrosomal exocytosis in human sperm

“…sperm dysfunction (http://www.who.int/ reproductive-health/ infertility/ report.pdf), but 20-30% of these are classified 'normal' by standard semen analyses (quantity, morphology and motility) (Liu and Baker, 2003). A crucial aspect of sperm function not amenable to such analysis is the acrosome reaction (AR), yet premature AR and/or AR failure are important causes of male infertility (Liu et al, 2006). The AR, the Ca 2+ -dependent exocytosis of the acrosome, requires multiple fusions between the outer acrosomal membrane (OAM) and the closely apposed plasma membrane.…”

Secretory Mechanisms and Ca2+ Signaling in Gametes: Similarities to Regulated Neuroendocrine Secretion in Somatic Cells and Involvement in Emerging Pathologies

“…In another study, patients with unexplained infertility and low fertilization rates with routine IVF also had a subnormal value for their zonainduced acrosome score; pregnancy was achieved by ICSI [133]. In infertility couples in which most or all eggs do not fertilize with routine IVF, a recent literature review indicated that these cases are associated with reduced sperm-zona binding, or impaired zona-induced acrosome exocytosis and zona penetration [134]. It should be noted that both animal and human studies indicated that the zona-induced acrosome exocytosis appears to be an important prerequisite for zona penetration, as sperm experimentally induced to undergo the acrosome reaction had decreased binding to the zona in in vitro assays [134].…”