To achieve fertilization, mammalian spermatozoa must undergo capacitation and the acrosome reaction (AR) within the female reproductive tract. However, the effects of cryopreservation on sperm maturation and fertilizing potential have yet to be established. To gain insight into changes in protein levels within sperm cells prepared for use in the context of fertilization, a comprehensive quantitative proteomic profiling approach was used to analyze frozen–thawed Ashidan yak spermatozoa under three sequential conditions: density gradient centrifugation-based purification, incubation in a capacitation medium, and treatment with the calcium ionophore A23187 to facilitate AR induction. In total, 3280 proteins were detected in these yak sperm samples, of which 3074 were quantified, with 68 and 32 being significantly altered following sperm capacitation and AR induction. Differentially abundant capacitation-related proteins were enriched in the metabolism and PPAR signaling pathways, while differentially abundant AR-related proteins were enriched in the AMPK signaling pathway. These data confirmed a role for superoxide dismutase 1 (SOD1) as a regulator of sperm capacitation while also offering indirect evidence that heat shock protein 90 alpha (HSP90AA1) regulates the AR. Together, these findings offer a means whereby sperm fertility-related marker proteins can be effectively identified. Data are available via Proteome Xchange with identifier PXD035038.

Our goal was to investigate heparin‐induced capacitation of frozen‐thawed yak sperm and to assess the effects of caffeine or ouabain supplementation with heparin on sperm capacitation. Sperm were incubated with varying heparin concentrations, namely 0, 12.5, 25, 50 and 100 μg/ml, for 0, 15, 30 and 60 min. In every treatment, sperm capacitation was assessed using microscopic examination of the sperm acrosomal status and western blot analysis of the levels of tyrosine phosphorylation (Tyr‐P). Based on our results, the optimal condition for frozen‐thawed yak sperm capacitation was a 30‐min exposure to 50‐μg/ml heparin. Next, we incubated frozen‐thawed yak sperm with 50‐μg/ml heparin, along with varying concentrations of caffeine supplementation, namely 0, 2.5, 5 and 10 mM for 30 min. Interestingly, caffeine significantly increased yak sperm acrosome reaction (AR) and Tyr‐P (p < .05). The optimal caffeine concentration was 5 mM, followed by 2.5 and 10 mM, with the lowest AR and Tyr‐P found in sperm cells that did not receive any caffeine. To examine the effects of ouabain on sperm capacitation, we next incubated frozen‐thawed yak sperm with 50‐μg/ml heparin, along with varying concentrations of ouabain, namely 0, 25, 50 and 100 µM for 30 min. We demonstrated that ouabain supplementation did not alter yak sperm AR or Tyr‐P in sperm cells, relative to the control (p > .05). In summary, our findings suggested that caffeine acts synergistically with heparin to increase yak sperm capacitation, but ouabain does not synergize with heparin to promote yak sperm capacitation.