The power of 810 nm near-infrared photobiomodulation therapy for human asthenozoospermia

Sperm motility is a crucial factor in male fertility. Photobiomodulation (PBM) has been reported to increase sperm motility, but a consistent approach suitable for identifying standardizable protocols is lacking. We collected asthenozoospermic (n = 70) and normozoospermic (n = 20) semen. The asthenozoospermic samples were irradiated with an 810 nm diode laser, in continuous wave mode, at 0.25 W, 0.5 W, 1 W and 2 W for 60 s on a circular area of 1 cm2 through a novel handpiece with an innovative flat-top profile. Sperm motility was assessed immediately, after 30 and 60 min. A sample size calculator, unpaired t-test and one-way ANOVA with post-hoc Tukey HSD tests were used for statistics. One and 2 W were the most effective outputs in increasing progressive motility compared to control (p < 0.001). The maximum effect was immediately after 1 W-PBM (p < 0.001) and decreased after 60 min (p < 0.001). Time physiologically decreased vitality (p < 0.001), but less in the 1 W-PBM samples (p < 0.05). 1 W-PBM did not affect chromatin condensation. Asthenozoospermic samples displayed an impairment of 80% in oxygen consumption and ATP production and a slight inefficiency of oxidative phosphorylation compared to normozoospermic samples (p < 0.001). 1 W-PBM partially restored the functionality of aerobic metabolism (p < 0.001) by recovery of oxidative phosphorylation efficiency. PBM did not affect lactate dehydrogenase (glycolysis pathway). No irradiated samples increased accumulated malondialdehyde, a marker of lipidic peroxidation. In conclusion, PBM improves progressive motility in asthenozoospermia through increased mitochondrial energetic metabolism without harmful oxidative stress.