[Mitochondria-targeted antioxidant Mitoquinone protects post-thaw human sperm against oxidative stress injury]

To investigate the potential protective effect of the mitochondria-targeted antioxidant Mitoquinone (MitoQ) on post-thaw human sperm.

Semen samples were collected from 60 normal fertile men, each divided into six parts of equal volume to be incubated at 37 °C in normal saline (G0, control) or in the extender with 2 nmol/L (G1), 20 nmol/L (G2), 200 nmol/L (G3), 2 µmol/L (G4), and 20 µmol/L of MitoQ (G5). After one hour of incubation, the samples were subjected to computer-assisted semen analysis (CASA) for sperm motility, flow cytometry for reactive oxygen species (ROS), thiobarbituric acid assay for the concentration of malondialdehyde (MDA), and MitoTracker fluorescent staining and flow cytometry for the sperm mitochondrial membrane potential (MMP). Then, the semen were cryopreserved with none (B0), 200 nmol/L (B1), and 2 µmol/L of MitoQ (B2), followed by detection of the changes in the ROS, MDA, and MMP of the post-thaw sperm.

The percentage of progressively motile sperm and total rate of sperm motility were significantly higher in G3 ([30.8 ± 10.2]% and [70.6 ± 9.0]%) and G4 ([32.7 ± 13.5]% and [70.3 ± 11.9]%) than in G0 ([17.6 ± 5.0]% and [54.9 ± 11.5]%) (P < 0.05). The level of ROS dropped markedly with the increased concentration of MitoQ, 86.5 ± 31.6 in G3, 93.6 ± 42.0 in G4, and 45.1 ± 15.0 in G5, as compared with 160.8 ± 39.7 in G0 (P < 0.05). The content of MDA was remarkably lower in G3 ([0.9 ± 0.5] µmol/mg) and G4 ([0.9 ± 0.5] µmol/mg) than in G0 ([1.9 ± 1.1] µmol/mg) (P < 0.05), but not in G5 ([1.7 ± 0.7] µmol/mg), which was even higher than in G3 and G4 (P < 0.05). The MMP showed a significant reduction in G5 (1156 ± 216) in comparison with G0 (1701 ± 251) (P < 0.05) but exhibited no remarkable difference between G0 and G1 (1810 ± 298), G2 (1995 ± 437), G3 (1950 ± 334), or G4 (1582 ± 314). The percentage of progressively motile sperm and total rate of sperm motility after freezing-thawing were significantly decreased as compared with those of the fresh semen (P < 0.01), but both were remarkably higher in B1 ([3.2 ± 2.3]% and [ 43.0 ± 9.5]%) than in B0 ([0.8 ± 0.6]% and [26.5 ± 11.4]%) (P < 0.05). The ROS level was significantly lower in B1 and B2 than in B0 (34.6 ± 12. 3 and 37.0 ± 10.5 vs 56.9 ± 14.3, P < 0.05), and so was the MDA content ([1.4 ± 0.5] and [1.4 ± 0.6] µmol/mg vs [2.6 ± 1.0] µmol/mg, P < 0.05), but the MMP was markedly higher in B1 and B2 than in B0 (1010.0 ± 130.5 and 880.6 ± 128.6 vs 721.1 ± 24.8, P < 0.05).

Addition of MitoQ to the freezing extender at 200 nmol/L may effectively improve the quality of human sperm and MitoQ is a good protective addictive for human sperm cryopreservation.