Evaluating sperm fertilizing potential: what can we predict?

Abstract

Multiparametric approaches that characterize the functional and metabolic aspects of sperm offer real-time information to discriminate and identify sperm subpopulations with attributes suitable for fertilization. In vivo, sperm requires various abilities to fertilize an oocyte that are less relevant for in vitro fertilization (IVF). Traditional evaluations such as sperm motility, DNA integrity, morphology, and viability as a measure of plasma membrane integrity are less sensitive and specific in detecting sublethal damage that can reduce a sample’s fertilizing potential. During in vivo fertilization, the female reproductive tract has a critical role in removing most of the dead sperm and those with sublethal damage that may explain why certain sperm variables have reduced predictive power for IVF success. Assessment of metabolic and physiological status provides new methods to estimate sperm fertilizing potential both in vivo and in vitro by identifying sublethal damage and capacitation-related changes. For IVF and intracytoplasmic sperm injections, sperm factors involved in oocyte activation and embryo development (e.g. phospholipase C zeta 1 [PLCZ1]), are considered the major male factors contributing to the failure of oocyte activation and embryo development. Reduced amounts, abnormal localization, and genetic variability of the PLCZ1 have been identified as factors in male infertility, suggesting potential diagnostic and prognostic value for clinical applications. However, male reproductive performance and fertilization are highly complex processes influenced by several factors. This complexity limits the predictive value of any single sperm assessment for reliably determining fertility outcomes.