Sperm plasma membrane potential as a marker for fertilization success for non-normozoospermic patients undergoing assisted reproduction technologies

PURPOSE: Semen analysis is a standard tool for assessing male fertility, but it frequently fails to accurately predict fertilization outcomes. We investigated whether sperm plasma membrane potential (Em) can be used to predict fertilization success in non-normozoospermic samples. METHODS: This study included semen samples from 119 non-normozoospermic men undergoing either in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI). After completion of the clinical ART procedure, the remaining spermatozoa were stained with the Em-sensitive dye DiSC₃(5) and propidium iodide to assess viability. Sperm Em were assessed by time-lapse flow cytometry and correlated with the fertilization outcomes. RESULTS: Unsupervised clustering of Em values revealed three distinct patient groups with different degrees of membrane polarization. Notably, samples exhibiting more depolarized Em values were associated with significantly lower fertilization rates (< 60%), whereas more hyperpolarized samples correlated with higher fertilization rates (60%). This correlation was only observed in patients undergoing IVF, but not ICSI. CONCLUSIONS: These findings show that despite inter-individual variability, sperm Em could serve as a complementary tool to predict the fertilization potential during IVF in patients with sperm abnormalities, thus providing valuable information for clinical decision-making in ART.