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

A Comprehensive Systematic Review of the Effects of Photobiomodulation Therapy in Different Light Wavelength Ranges (Blue, Green, Red, and Near-Infrared) on Sperm Cell Characteristics in Vitro and in Vivo

Around 7% of the male population in the world are entangle with considerable situation which is known as male infertility. Photobiomodulation therapy (PBMT) is the application of low-level laser radiation, that recently used to increase or promote the various cell functions including, proliferation, differentiation, ATP production, gene expressions, regulation of reactive oxygen spices (ROS), and also boost the tissue healing and reduction of inflammation. This systematic review's main idea is a comprehensive appraisal of the literatures on subjects of PBMT consequences in four light ranges wavelength (blue, green, red, near-infrared (NIR)) on sperm cell characteristics, in vitro and in vivo. In this study, PubMed, Google Scholar, and Scopus databases were used for abstracts and full-text scientific papers published from 2003-2023 that reported the application of PBM on sperm cells. Criteria's for inclusion and exclusion to review were applied. Finally, the studies that matched with our goals were included, classified, and reported in detail. Also, searched studies were subdivided into the effects of four ranges of light irradiation, including the blue light range (400-500 nm), green light range (500-600 nm), red light range (600-780 nm), and NIR light range (780-3000 nm) of laser irradiation on human or animal sperm cells, in situations of in vitro or in vivo. Searches with our keywords results in 137 papers. After primary analysis, some articles were excluded because they were review articles or incomplete and unrelated studies. Finally, we use the 63 articles for this systematic review. Our category tables were based on the light range of irradiation, source of sperm cells (human or animal cells) and being in vitro or in vivo. Six% of publications reported the effects of blue, 10% green, 53% red and 31% NIR, light on sperm cell. In general, most of these studies showed that PBMT exerted a positive effect on the sperm cell motility. The various effects of PBMT in different wavelength ranges, as mentioned in this review, provide more insights for its potential applications in improving sperm characteristics. PBMT as a treatment method has significant effectiveness for treatment of different medical problems. Due to the lack of reporting data in this field, there is a need for future studies to assessment the biochemical and molecular effects of PBMT on sperm cells for the possible application of this treatment to the human sperm cells before the ART process.

The effects of photobiomodulation on the improvement of sperm parameters: A review study

The prevalence of male infertility has become a significant clinical concern worldwide, with a noticeable upward trend in recent times. The rates of fertilization and subsequent development of embryos are dependent on many parameters associated with the quality and viability of sperm. Photobiomodulation (PBM) is a promising approach with a great potential for translational applications in the treatment of spermatozoa exhibiting low quality and motility. In this study, a comprehensive analysis of the existing literature, specifically examining the mechanisms of action of PBM has been presented. Our objective was to enhance knowledge in the field of laser light therapy in order to promote the usage of irradiation in clinical settings in a more effective way. Within the realm of reproductive science, the utilization of PBM has been employed to enhance the metabolic processes, motility, and viability of spermatozoa. This is attributed to its advantageous effects on mitochondria, resulting in the activation of the mitochondrial respiratory chain and subsequent synthesis of ATP. This therapeutic approach can be highly advantageous in circumventing the reliance on chemical substances within the culture medium for spermatozoa while also facilitating the viability and motility of spermatozoa, particularly in circumstances involving thawing or samples with significant immotility.

The effects of red LED light on pig sperm function rely upon mitochondrial electron chain activity rather than on a PKC-mediated mechanism

While irradiation with red LED light has been reported to modulate sperm function in different mammalian species, the mechanisms underlying their response are poorly understood. This work sought to provide new insights into whether this effect relies on a direct action upon mitochondrial electron chain and/or on PKC-linked mechanisms such as those related to opsins. For this purpose, pig semen was light-stimulated for 1, 5 or 10 min in the presence/absence of antimycin A, an inhibitor of the mitochondrial electron chain, or PKC 20–28^® (PKCi), a PKC inhibitor. Antimycin A completely blocked the effects of light at all the performed irradiation patterns. This effect was linked to a complete immobility of sperm, which was accompanied with a significant (p < 0.05) drop in several markers of mitochondrial activity, such as JC-1 staining and O₂ consumption rate. Antimycin A, however, did not affect intracellular ATP levels, intramitochondrial calcium, total ROS, superoxides or cytochrome C oxidase (CCO) activity. In the case of PKCi, it did also counteract the effects of light on motility, O₂ consumption rate and CCO activity, but not to the same extent than that observed for antimycin A. Finally, the effects observed when sperm were co-incubated with antimycin A and PKCi were similar to those observed with antimycin A alone. In conclusion, red LED light acts on sperm function via a direct effect on mitochondrial electron chain. Additionally, light-activated PKC pathways have a supplementary effect to that observed in the electron chain, thereby modulating sperm parameters such as motility and CCO activity.

Photo Stimulation of Seminal Doses with Red LED Light from Duroc Boars and Resultant Fertility in Iberian Sows

Simple Summary

The main objective of breeding Iberian pigs is the production of high-quality dry cured meat products. As this breed shows a reduced litter size in comparison to the commercial breeds, some previous studies have reported the use of photostimulation of seminal doses as a method for improving the farrowing rate and litter size. The aim of this study was to explore whether the application of a photostimulation procedure to Duroc seminal doses has any beneficial effect on fertility and litter size. Semen samples were obtained from 38 fertile Duroc boars and the fertility study was conducted on two commercial farms using multiparous Iberian sows (farm A, n = 824; farm B, n = 2131), that were randomly assigned to LED (L) or control (C) groups. Post-cervical insemination took place 0 and 24 h after the diagnosis of estrus, with seminal doses from the same ejaculate and same treatment. The photostimulation of the seminal doses had no effect on the reproductive performance (farrowing rate: 91.72% C vs. 90.09% L, litter size: 8.71 ± 0.06 piglets C vs. 8.70 ± 0.05 L, p > 0.05).

Abstract

In pigs, it has been reported that increased farrowing rates and litter size have been induced by photostimulating the seminal doses for artificial insemination with red LED light. As the reproductive characteristics, production system, and outcome parameters of Iberian breed pigs are different from other commercial breeds, the aim of this study was to evaluate the possible effect of illuminating seminal doses from Duroc boars with red LED light and the fertility outcomes of Iberian females. Semen samples were obtained from 38 fertile Duroc boars. Photostimulation of the artificial insemination (AI) seminal doses was carried out by illuminating the samples with a red LED for 10 min, followed by 10 min of darkness, and finally 10 additional minutes of red light. The fertility study was conducted on two commercial farms using multiparous Iberian sows (farm A, n = 824; farm B, n = 2131), that were randomly assigned to LED (L) or control (C) groups. No differences were found between L and C groups in both farms (p > 0.05) for parity, pregnancy rate, duration of pregnancy, farrowing rate, and litter size (total, alive, and stillborn piglets). Farrowing rates in farm A were 88.8% (n = 383) for control and 89.6% (n = 441, p = 0.67) for the LED group. In farm B, farrowing rates were C:90.5% (n = 1030) and L: 90.1% (n = 1101, p = 0.48). In farm A, total born piglets were 8.69 ± 0.11 for C and 8.71 ± 0.11 for L (p = 0.87). In farm B, the results were 8.72 ± 0.7 for C and 8.70 ± 0.06 (p = 0.82) for L. Under the production conditions for the Iberian breed, the photostimulation with red LED light using Duroc pig seminal doses was not effective in improving the fertility of Iberian sows.

Effect of continuous wave, quasi-continuous wave and pulsed laser radiation on functional characteristics of fish spermatozoa

For the first time, using sturgeon sperm as a model system, sensitive to optical radiation, the comparative studies of biological effect of continuous wave, quasi-continuous wave, nano- and picosecond laser radiation under conditions with equal average irradiance (3 mW/cm²) and wavelength (532 nm) have been carried out. Analyzing the parameters of spermatozoa motion it has been shown that, depending on the energy dose and mode of laser operation, the radiation may have both stimulatory and inhibitory effect on the velocity of motion and spermatozoa motility duration as well as on sustaining of functional characteristics of cold-stored sperm. The possibility of increasing the fertilization rate due to use of the sperm preliminary treated with laser radiation is demonstrated. For the first time, the possibility of enhancement of biological effect going from continuous wave to quasi-continuous wave laser radiation at equal irradiance and wavelength has experimentally been proven. It is shown that the difference in biological effect of continuous wave, quasi-continuous wave, nano- and picosecond laser radiation is due to amplitude (peak) values of intensity. Using fluorescence analysis and luminol-dependent chemiluminescence assay, evidence for the participation of endogenous flavins and metal-free porphyrins in sensitized ROS formation (singlet oxygen, hydrogen peroxide, and hydroxyl radicals) in sturgeon sperm was obtained. Mechanisms of photochemical and photothermal reactions explaining the difference in efficacy of action of laser radiation in above modes are discussed.

The Effects of Red Light on Mammalian Sperm Rely upon the Color of the Straw and the Medium Used

Simple Summary

Several studies have shown that the exposure of semen to red light improves sperm quality and fertilizing ability, which could improve the efficiency of assisted reproductive techniques with irradiated semen. However, despite being considered as possible sources of variation, the effects of the color of the container (straws) or the medium have not yet been evaluated. In this study, 13 ejaculates from different stallions were split into equal fractions, diluted either with Kenney or Equiplus extender, and subsequently packed into straws of five different colors. After storage at 4 °C for 24 h, the sperm were irradiated and different variables, including sperm motility, plasma membrane integrity, and mitochondrial membrane potential, were evaluated. Our results confirm that irradiation increases some motion characteristics and mitochondrial membrane potential without affecting sperm viability and demonstrate that the effects depend on the color of the straw and the extender used.

Abstract

Previous research has determined that irradiation of mammalian sperm with red light increases motility, mitochondrial activity, and fertilization capacity. In spite of this, no study has considered the potential influence of the color of the straw and the extender used. Therefore, this study tests the hypothesis that the response of mammalian sperm to red light is influenced by the color of the straw and the turbidity/composition of the extender. Using the horse as a model, 13 ejaculates from 13 stallions were split into two equal fractions, diluted with Kenney or Equiplus extender, and stored at 4 °C for 24 h. Thereafter, each diluted fraction was split into five equal aliquots and subsequently packed into 0.5-mL straws of red, blue, yellow, white, or transparent color. Straws were either nonirradiated (control) or irradiated with a light–dark–light pattern of 3–3–3 (i.e., light: 3 min, dark: 3 min; light: 3 min) prior to evaluating sperm motility, acrosome and plasma membrane integrity, mitochondrial membrane potential, and intracellular ROS and calcium levels. Our results showed that irradiation increased some motion variables, mitochondrial membrane potential, and intracellular ROS without affecting the integrities of the plasma membrane and acrosome. Remarkably, the extent of those changes varied with the color of the straw and the extender used; the effects of irradiation were more apparent when sperm were diluted with Equiplus extender and packed into red-colored straws or when samples were diluted with Kenney extender and packed into transparent straws. As the increase in sperm motility and intracellular ROS levels was parallel to that of mitochondrial activity, we suggest that the impact of red light on sperm function relies upon the specific rates of energy provided to the mitochondria, which, in turn, vary with the color of the straw and the turbidity/composition of the extender.

Red LED Light Acts on the Mitochondrial Electron Chain of Donkey Sperm and Its Effects Depend on the Time of Exposure to Light

This work aimed to investigate how stimulation of donkey sperm with red LED light affects mitochondrial function. For this purpose, freshly diluted donkey semen was stimulated with red light for 1, 5, and 10 min, in the presence or absence of oligomycin A (Omy A), a specific inhibitor of mitochondrial ATP synthase, or FCCP, a specific disruptor of mitochondrial electron chain. The results obtained in the present study indicated that the effects of red LED light on fresh donkey sperm function are related to changes in mitochondria function. In effect, irradiation of donkey sperm resulted in an increase in mitochondrial membrane potential (MMP), the activity of cytochrome C oxidase and the rate of oxygen consumption. In addition, in the absence of oligomycin A and FCCP, light-stimulation augmented the average path velocity (VAP) and modified the structure of motile sperm subpopulations, increasing the fastest and most linear subpopulation. In contrast, the presence of either Omy A or FCCP abolished the aforementioned effects. Interestingly, our results also showed that the effects of red light depend on the exposure time applied, as indicated by the observed differences between irradiation protocols. In conclusion, our results suggest that exposing fresh donkey sperm to red light modulates the function of their mitochondria through affecting the activity of the electron chain. However, the extent of this effect depends on the irradiation pattern and does not exclude the existence of other mechanisms, such as those related to thermotaxis.

Red LED Light Acts on the Mitochondrial Electron Chain of Mammalian Sperm via Light-Time Exposure-Dependent Mechanisms

This work analyzes the effects of red LED light on mammalian sperm mitochondrial function, using the pig as an animal model. Liquid-stored pig semen was stimulated with red-light for 1, 5 and 10 min in the presence or absence of oligomycin A, a specific inhibitor of mitochondrial ATP synthase, or carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP), a specific disruptor of mitochondrial electron chain. Whereas exposure for 1 and 5 min significantly (p < 0.05) decreased total motility and intracellular ATP levels, irradiation for 10 min induced the opposite effect. Oligomycin A abolished the light-effects on intracellular ATP levels, O2 consumption and mitochondrial membrane potential, whereas compared to non-irradiated samples, FCCP significantly (p < 0.05) increased O2 consumption when sperm were irradiated for 1 min. Both oligomycin A and FCCP significantly (p < 0.05) decreased total motility. Red-light increased cytochrome c oxidase activity with a maximal effect after 5 min of irradiation, which was abolished by both oligomycin A and FCCP. In conclusion, red-light modulates sperm mitochondrial function via electron chain activity in an exposition, time-dependent manner.

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

Previous studies in other mammalian species have shown that stimulation of semen with red-light increases sperm motility, mitochondrial activity, and fertilizing capacity. This study sought to determine whether red-light stimulation using a light emitting diode (LED) at 620–630 nm affects sperm motility and structure of motile subpopulations, sperm viability, mitochondrial activity, intracellular ATP levels, rate of O₂ consumption and DNA integrity of horse spermatozoa. For this purpose, nine ejaculates were collected from nine different adult stallions. Upon collection, semen was diluted in Kenney extender, analyzed, its concentration was adjusted, and finally it was stimulated with red-light. In all cases, semen was packaged in 0.5-mL transparent straws, which were randomly divided into controls and 19 light-stimulation treatments; 6 consisted of a single exposure to red-light, and the other 13 involved irradiation with intervals of irradiation and darkness (light-dark-light). After irradiation, sperm motility was assessed using a Computerized Semen Analysis System (CASA). Flow cytometry was used to evaluate sperm viability, mitochondrial membrane potential and DNA fragmentation. Intracellular levels of ATP and O₂ consumption rate were also determined. Specific red-light patterns were found to modify kinetics parameters (patterns: 4, 2-2-2, 3-3-3, 4-4-4, 5-1-5, and 5-5-5 min), the structure of motile sperm subpopulations (patterns: 2, 2-2-2, 3-3-3, and 4-1-4 min), mitochondrial membrane potential (patterns: 4, 3-3-3, 4-4-4, 5-1-5, 5-5-5, 15-5-15, and 15-15-15 min), intracellular ATP levels and the rate of O₂ consumption (pattern: 4 min), without affecting sperm viability or DNA integrity. Since the increase in some kinematic parameters was concomitant with that of mitochondrial activity, intracellular ATP levels and O₂ consumption rate, we suggest that the positive effect of light-irradiation on sperm motility is related to its impact upon mitochondrial activity. In conclusion, this study shows that red LED light stimulates motility and mitochondrial activity of horse sperm. Additional research is needed to address the impact of red-light irradiation on fertilizing ability and the mechanisms through which light exerts its effects.

Medium-term effects of the diluted pig semen irradiation with red LED light on the integrity of nucleoprotein structure and resilience to withstand thermal stress

This study sought to evaluate the effects of irradiating pig seminal doses with red LED light irradiation on their quality and longevity over liquid-storage at 17 °C. For this purpose, boar ejaculates were diluted in a commercial extender at a final concentration of 3 × 10⁷ sperm/mL and stored at 17 °C for 96 h. Upon arrival to our laboratory (5-6 h within collection), 1.5 mL-aliquots were subjected to irradiation with a temperature-controlled red light-emitting diode (LED) for 1 min, 5 min or 10 min. Controls consisted of non-irradiated spermatozoa. Aliquots were then stored at 17 °C for 96 h, and plasma membrane and acrosome integrity, motility and free cysteine radicals of sperm head proteins were evaluated every 24 h. In addition, the sperm resilience to withstand thermal stress following irradiation was evaluated at 24 h, 48 h, 72 h and 96 h by incubating stored seminal doses at 37 °C for 120 min. In our experimental conditions, light-stimulation for 5 min and 10 min counteracted the decrease in thermal stress observed in non-irradiated samples during the first 48 h of storage. Moreover, all irradiation protocols counteracted the decrease in percentages of spermatozoa with altered acrosomes observed in non-irradiated samples after 72 h of storage. The effects of light-stimulation upon sperm motility parameters were less consistent. While liquid-storage also led to an increase in the free cysteine levels of sperm head proteins, this increment was partially mitigated through light-stimulation for 5 min and 10 min. Our results suggest that effects linked with red LED light irradiation would be consistently maintained in our experimental conditions for the first 48 h. Finally, the maintenance of light effect appears to depend upon the specific experimental design, the analyzed sperm parameters and the utilized irradiation patterns.

Irradiating frozen-thawed stallion sperm with red-light increases their resilience to withstand post-thaw incubation at 38 °C

The aim of this study was to evaluate whether red-light stimulation increases the longevity and resilience of cryopreserved stallion sperm to withstand post-thaw incubation for 120 min. Sixteen frozen straws of 0.5 mL from eight stallions were used. Samples were cryopreserved, thawed through incubation at 38 °C for 30 s and divided into the control and samples exposed to red-light using a triple LED photo-activation system (wavelength: 620-630 nm). Three irradiation protocols consisting of different light-dark-light intervals (1-1-1, 2-2-2 and 3-3-3 min) were tested. Sperm quality parameters were analyzed immediately after light-stimulation (0 min) and after 120 min of incubation at 38 °C. Sperm motility was evaluated using a Computerized Semen Analysis System (CASA), and flow cytometry and different fluorochromes were used to evaluate the integrity and lipid disorder of plasma membrane, mitochondrial membrane potential and intracellular levels of peroxides and superoxides. Irradiation significantly increased the percentages of spermatozoa with high mitochondrial membrane potential (1-1-1 pattern) and the intracellular levels of peroxides (2-2-2 pattern) at 0 min. In addition, sperm kinematic parameters (2-2-2 and 3-3-3 patterns) and percentages of viable spermatozoa with low membrane lipid disorder (3-3-3 pattern) were significantly higher in irradiated samples than in the control at 120 min. Our results indicate that red-light stimulation could help increase the resilience of frozen-thawed stallion sperm to withstand post-thaw incubation at 38 °C for 120 min and that these effects rely on the irradiation pattern. Further research should evaluate whether light-stimulation could also have a positive on fertility rates after artificial insemination.

Effects of red-light irradiation on the function and survival of fresh and liquid-stored donkey semen

This study sought to determine whether sperm irradiation using a light emission diode (LED) at 620-630 nm affects the motility, membrane integrity (viability), mitochondrial activity and intracellular levels of reactive oxygen species (ROS) in fresh diluted and liquid-stored donkey semen. With this purpose, sixteen ejaculates (eight fresh diluted and eight cooled-stored) were collected from eight adult jackasses. Fresh semen samples were diluted in Kenney extender and stimulated with red-light after collection, whereas cooled semen was stored at 4 °C for 24 h after dilution and then irradiated. In all cases, semen samples were packed into 0.5-mL transparent straws, which were then randomly divided into control and 19 treatments: six consisted of single red-light exposure, and the other 13 involved irradiation at light-dark-light intervals. Upon irradiation, sperm motility, membrane integrity mitochondrial membrane potential (MMP) and intracellular levels of superoxide anion (·O₂^-) and hydrogen peroxide (H₂O₂) were evaluated. While specific light-patterns increased both sperm motility and mitochondrial activity, they did not affect sperm membrane integrity and had no clear impact on intracellular ROS levels. The effects of irradiation patterns differed between fresh and cooled semen since, whereas 1 and 4 min patterns induced the greatest increments in the total and progressive motility of fresh semen, 4 min, 4-1-4 and 4-4-4 were the most suitable for cooled-stored samples. In both fresh diluted and cooled-stored semen, the motility increase observed after light-stimulation for 4 min was concomitant with changes in the percentages of spermatozoa with high mitochondrial membrane potential. In summary, this study shows, for the first time, that specific irradiation patterns increase sperm motility and mitochondrial activity in the donkey. Furthermore, the precise effect of red-light appears to depend on the specific functional status of cells, with separate effects on fresh and cooled samples.

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

A survey of in vivo fertility data from 31 pig farms distributed worldwide was conducted to determine whether stimulating boar semen with LED-based red light increases its reproductive performance following artificial insemination (AI). Red-light stimulation with MaXipig^® was found to increase farrowing rates (mean ± SEM, control: 87.2% ± 0.4% vs. light stimulation 90.3% ± 0.5%) and the number of both total and live newborn piglets. Red-light stimulation increased farrowing rates in 27 farms, with an increase ranging from 0.2% to 9.1%. Similar results were observed in litter sizes. Suboptimal management after AI was suggested in those farms with no response to red-light stimulation. Our results indicate that a routine use of red-light stimulation of boar semen can have a positive effect on the reproductive performance. However, the effectiveness of this system appears to highly rely upon proper management of pig farms.

Photostimulation and thermotaxis of sperm: Overview and practical implications in porcine reproduction

The journey of mammalian sperm through the female genital tract requires the existence of a myriad of mechanisms that allow cells to reach the oviduct in a timely manner from the place of semen deposition. Several biochemical mechanisms such as signaling through molecules like bicarbonate, neurotransmitters or even glycosaminoglycanes are known and have been studied by several relevant groups worldwide. However, biophysical mechanisms for sperm transport are much less studied and understood. Thermotaxis, for example, is a powerful, physical signaling system that is known to direct sperm inside the female genital tract, although the intimate mechanisms by which this effect is launched are yet to be elucidated. This review is focuses on the analysis of thermotaxis and its possible relationship with another phenomenon that has been observed in sperm from a variety of species, namely photostimulation. An overall review on sperm thermotaxis and putative mechanism/s that can be involved in this phenomenon is developed, followed by a description of the most recent findings on the mechanisms underlying sperm photostimulation, highlighting its possible relationship with thermotactic mechanisms. Finally, an overview regarding some practical implications of the phototactic/thermotactic phenomenon has been included in order to evaluate the possible use of techniques based on these phenomena as tools for improving pig reproduction.