Recombinant heat shock protein HSPA1A increases cryoresistanceof bull sperm

Abstract

This study evaluated the effect of recombinant heat shock protein HSPA1A on bovine sperm subjected to cooling (for 96 hours at 5 °C) and freezing process. An initial experiment determined the optimal concentration of HSPA1A (0, 15, 30, and 45 µg/mL) supplemented into the OPTIXcell extender, using 18 ejaculates (from 2 bulls) refrigerated for 96 hours. Subsequently, the effect of supplementing 45 µg/mL of HSPA1A (optimal concentration) into the OPTIXcell extender was evaluated, using 6 ejaculates subjected to freezing via static liquid nitrogen vapor. The results indicated that all concentrations of HSPA1A produced higher values for kinematic variables, viability, and acrosomal integrity compared to the control during 96 hours of refrigeration (p < 0.05). Additionally, 45 µg/mL HSPA1A showed a higher beat cross frequency (BCF) than the other HSPA1A concentrations (p < 0.05). After thawing, the motilities, BCF, and cryoresistance indices for motility, viability, and acrosomal integrity were higher in samples frozen with HSPA1A compared to the control (p < 0.05). In conclusion, the recombinant HSPA1A protein improved the motility, viability, and acrosomal integrity of refrigerated and cryopreserved bull sperm