Ultrasound Exposure May Detrimentally Affect Sperm Function and Survival: Possible Implications for Cryobiology

Ultrasound has attracted interest in cryobiology for its potential to enhance heat transfer and reduce thermal gradients during thawing. Little is, however, known about how ultrasound exposure affects sperm cells. This study evaluated the effects of ultrasound on the functional parameters of pig semen. Semen samples from 10 boars were diluted, packaged in 0.5-mL straws at a standard freezing concentration, and exposed to ultrasound (40 kHz) for 0, 15, 30, 60 or 120 s. After treatment (10 min), sperm motility was assessed using computer-assisted sperm analysis, and plasma membrane integrity, mitochondrial membrane potential and intracellular reactive oxygen species were evaluated by flow cytometry. While short ultrasound exposure (15 s) did not affect sperm functionality, longer exposure (30-120 s) reduced both progressive and total motility and decreased plasma membrane integrity (p < 0.05). Mitochondrial membrane potential remained unchanged among treatments. These results indicate that ultrasound exposure has time-dependent effects on sperm function and survival, providing new insights into the potential use of ultrasound-assisted strategies for thawing cryopreserved sperm.