LED‐based red light photostimulation improves short‐term response of cooled boar semen exposed to thermal stress at 37°C

Abstract

Pre‐treatment of boar semen with a red light photostimulation procedure increases its “in vivo” fertilising ability. However, “in vitro” conducted studies shown contradictory results regarding the ability of photostimulated spermatozoa to react against strong stress and to achieve the capacitation status. The aim here was to determine the effect of photostimulation on the response to short‐term moderate thermal stress of boar semen. Boar semen was exposed to red LED light regime emitting a 620–630 nm during 10 min of light, 10 min of rest and 10 min of light after 3 hr since semen was collected. An aliquot without photostimulation was included as a control. After the photostimulation, the sperm cells were incubated for 15 min at 37°C. Afterwards, motility, viability, intracellular Ca2+ level and production of reactive oxygen species (ROS) and peroxynitrite were analysed. The results showed that the photostimulated group maintained total motility throughout the time, whereas a significant decrease in total motility was observed in the nonphotostimulated control group. Furthermore, for kinetic parameters of motility, a significant increase was observed in LIN, STR and WOB in photostimulated spermatozoa. Peroxynitrite production was significantly increased in the photostimulated spermatozoa, whereas viability, ROS production and intracellular Ca2+ levels were not affected by photostimulation. In conclusion, photostimulation of commercial boar semen has a positive effect on motility of spermatozoa subjected to a short‐term moderate thermal stress, which was concomitant with an increase in peroxynitrite production.

Red-Light Irradiation of Horse Spermatozoa Increases Mitochondrial Activity and Motility through Changes in the Motile Sperm Subpopulation Structure

“…Studies conducted with pig semen have reported that reproductive performance can be increased through light-stimulation of semen prior to AI [ 7 , 8 ]. In effect, previous works using different light sources, such as lasers and light-emitting diodes (LED), have suggested that light-stimulation has a positive effect on the motility and ability of sperm to fertilize the oocyte in pigs [ 7 , 8 , 9 ], mice [ 10 ], and sheep [ 11 ]. Remarkably, no study has reported any detrimental effect of visible light on DNA integrity [ 12 , 13 , 14 ].…”

“…Among all visible light spectra tested, red-light has been shown to be the one that improves sperm motility the most [ 15 ]. In addition to this, it has been reported that red-light stimulation (620–630 nm) by LED increases the fertilizing ability of pig sperm [ 7 , 8 , 9 ], without affecting their viability [ 7 , 9 ].…”

Red‐light stimulation of boar semen prior to artificial insemination improves field fertility in farms: A worldwide survey

“…In the case of boar semen, a previous study found that LED‐based red‐light stimulation increased its in vivo fertilizing ability (Yeste et al, ). While this study was performed in one farm, further reports showed inconsistent effects of red‐light stimulation on sperm quality parameters evaluated in vitro (Luther, Thi, Schäfer, Schulze, & Waberski, ; Pezo et al, ).…”

Comparative Effect of Low‐intensity Laser Radiation in Green and Red Spectral Regions on Functional Characteristics of Sturgeon Sperm

“…Numerous studies performed with sperm from different species have shown that the radiation in visible spectral region (blue-green region: k = 470 nm (13), green: k = 532 nm (25,39), k = 490-540 nm (34); red: k = 620-630 (2,(20)(21)(22)(23), k = 630 (19), k = 632.8 (15,24,27,28,30,35,36), k = 635 nm (38), k = 637 nm (14), k = 647 nm (1), k = 650 nm (35), k = 655 nm (30,31), k = 660 nm (26,29), k = 670 nm (37)) and in near-infrared spectral region (k = 810 nm (16,19), k = 830 nm (12), k = 850 nm (14), k = 905 nm (11), k = 940 nm (10)), as well as broadband white light (k = 400-800 nm (17,18,27)), exerts a regulatory effect on spermatozoa.…”

“…At the present time, convincing evidences of the changes in the most important characteristics of spermatozoa exposed to light (motility, velocity, vitality, maintaining at a higher level the functional characteristics of spermatozoa during storage and their fertilization rate) have been obtained. The effects of photobiomodulation were reported upon irradiation of sperm from different species: mammals (human (1,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), boar (20)(21)(22), horse (2), donkey (23), bull (24)(25)(26)(27), ram (28,29), rabbit (30), dog (31,32), mouse (18,33,34)), birds (35,36) and hydrobionts (29,(37)(38)(39)(40). Changes in the functional characteristics of spermatozoa are induced by exposure to coherent laser radiation (1,9,11,12,15,16,19,(24)(25)…”