Shining a light on male infertility: the power of 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 lacks a standardized protocol. We collected asthenozoospermic (n=70) and normozoospermic (n=20) semen. The asthenozoospermic samples were irradiated with an 810 nm diode laser at 0.25W, 0.5W, 1W, and 2W. Sperm motility was assessed immediately, after 30 and 60 minutes. 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 minutes (p<0.001). Time physiologically decreased vitality (p<0.001), but less in the 1W-PBM samples (p<0.05). 1W-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). 1W-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.