The Acrosome Exocytosis as a Diagnostic Functional Test: a narrative review

Infertility affects millions of couples worldwide, and male factors contribute to approximately 20–50% of infertility cases. Male infertility is typically evaluated with a semen analysis, which is a fundamental analysis to determine sperm quality. However, this analysis is limited. One of its most important deficiencies is the lack of functional sperm assessment. Because of this, semen analysis does not reveal information about the in vivo behavior of spermatozoa or their fertilization potential. This constitutes a concern because, in conventional semen analyses, 30% of infertile men display normal values in their semen analysis. In contrast, functional tests such as sperm-zona pellucida (ZP) binding assay and acrosome exocytosis (AE, also known as acrosome reaction) test predict male fertilization potential with greater accuracy. Here, we review functional tests and their potential to improve male infertility diagnostics and their predictive value for fertilization rates after IVF intervention. We also discuss the advantages of AE as a functional test to improve the diagnosis of male infertility in humans and other species, and its implementation in the clinic.