ProAKAP4: A Promising Biomarker Linking Post-Thaw Sperm Quality to Fertility in Dogs?

ProAKAP4, the precursor of A-kinase anchoring protein 4 (AKAP4), is a sperm-specific structural protein involved in flagellar organization, regulation of motility and energy metabolism. It has emerged as a potential biomarker of semen quality and fertility in several mammalian species. However, its relevance in canine reproduction remains insufficiently characterized. This study investigated the association between proAKAP4 concentrations, sperm kinematic parameters and fertility outcomes in dogs. Twenty-six ejaculates were collected from eight privately owned dogs (5-11 years old, various breeds), cryopreserved and evaluated before and after thawing. Sperm motility and velocity parameters were assessed using Computer-Assisted Sperm Analysis (CASA). ProAKAP4 concentrations were quantified using a species-Specific Dog 4MID ELISA assay. Artificial inseminations were performed in six bitches, and pregnancy rates and litter sizes were recorded. Post-thaw samples showed higher measurable proAKAP4 concentrations than fresh semen. However, no significant correlations were observed between proAKAP4 levels and total motility, progressive motility, conception rate, or litter size (p < 0.05) concentrations and sperm velocity parameters (VAP, VSL and VCL). These findings suggest that proAKAP4 may reflect aspects of sperm structural integrity.