Background: The effects of Low Level Light Therapy (LLLT) on cellular function arise predominantly from stimulation of ATP production and reduction of oxidative stress. These effects are dose dependent and a function of beam irradiance and irradiation time. Human sperm motility has been shown to increase with LLLT irradiation. The objective of this study was to investigate the effects of laser and Light Emitting Diode (LED) LLLT photobiomodulation on human spermatozoa motility and DNA integrity.
Methods: An in-vitro controlled trial was performed within an IVF clinic laboratory using three human semen specimens, one fresh and two frozen. Sperm were exposed to light from a GaAlAs single laser (810 nm 200 mW) and an LED cluster (660 nm and 850 nm total power 2 W) for various irradiation times. Sperm motility for the test and control aliquots was assessed using a SQA-IIB analyser, but fertilizing ability was not. Sperm chromatin integrity was tested using the Sperm Chromatin Structure Assay.
Results: The Sperm Motility Index and Total Functional Sperm Count increased up to four fold compared to controls with inhibitory effects observed at higher doses (longer irradiation times). The maximum effect varied with irradiance and irradiation time and whether the sample was fresh or frozen.
Discussion: Human sperm motility is modified by exposure to LLLT and this motility modification is dependent upon beam irradiance and irradiation time as well as the condition of the sample. A higher stimulatory dose provides a rapid increase in motility that is short in duration, while a lower stimulatory dose provides a slower increase in motility. An inhibitory does causes reduced motility. Future research could consider animal models, such as the mouse, to test fertilization capacity and the safety of resulting fetuses.
Keywords: Effect of Lasers in Tissue; Experimental Research; Laser Photobiomodulation; Light Emitting Diode (LED); Low-Level Laser Therapy.