Hyaluronic acid delays boar sperm capacitation after 3 days of storage at 15 °C

The present study was undertaken to determine the effects of the addition of hyaluronic acid (HA), ranged from 12.5 to 200 μg/ml, on boar sperm capacitation status during a storage time (up to 3 days) at 15 °C in Beltsville thawing solution (BTS). The raw extender was the negative control whereas different concentrations of caffeine (CAF), ranged from 0.25 to 8 mM, served as positive controls. Sperm viability, motility, morphology, and osmotic resistance were also determined before and after assessing the treatments. Samples were obtained from 28 healthy and post-pubertal Piétrain boars and sperm parameters were tested immediately after the addition of treatments and after 1, 2 and 3 days of refrigeration at 15 °C. Sperm capacitation status was determined by chlortetracycline (CTC) staining and sperm viability by means of a multiple fluorochrome-staining test. Sperm motility and morphology were assessed using phase-contrast microscopy accompanied by a computer assisted sperm analysis system (CASA). Whereas HA delayed sperm capacitation, CAF increased the frequency of capacitated spermatozoa after 2 days of cooling. Moreover, HA did not modify other sperm parameters, such as sperm velocity, whereas CAF increased progressive motility during the first 2 days of cooling and then decreased. It can be concluded that the addition of HA at 50 and 100 μg/ml to the BTS extender may delay sperm capacitation after 3 days of cooling.