Capacitation-Induced Zinc Ion Flux and Sperm Plasma Membrane Remodeling Predict Porcine In Vitro Fertilization...

Semen evaluation in human and animal reproduction relies on sperm motility and morphology; however, these often fail to predict fertility. The domestic boar (Sus scrofa) serves as a biomedical model for male reproduction due to similarities in sperm size, capacitation dynamics, and acrosomal structure to humans in comparison to traditional rodent models. This study evaluated sperm capacitation biomarkers, particularly zinc signatures, to predict cleavage success after in vitro fertilization (IVF). Semen from 20 boars (3 replicates each) was analyzed at 0, 1 and 4 h post-in vitro capacitation (IVC) using image-based flow cytometry to assess 4 zinc signatures, plasma membrane integrity, and acrosomal remodeling. Capacitation kinetics were quantified between timepoints. Motility was measured by computer-assisted semen analysis, and IVF cleavage percentages were determined. Zinc signature 1 at 4 h post-IVC negatively correlated with cleavage percentage (r = -0.366), indicating higher noncapacitated sperm proportions reduce fertilization potential. The delta of zinc signature 3 from 1 to 0 h also negatively correlated (r = -0.441), suggesting excessively rapid capacitation impairs fertilization. Models combining capacitation biomarkers, motility, kinetics, and morphology parameters had higher predictive power (R² = 0.469) than motility models alone. Zinc signatures may serve as mechanistic fertility biomarkers in a translational boar model applicable to animal breeding and human-assisted reproduction.