Preclinical and Clinical Applications of Photobiomodulation Therapy in Sperm Motility: A Narrative Review

Abstract

About 50% of infertility problems are related to male factors and reduced sperm motility. The important factor that affects the structure and function of sperm is reactive oxygen species (ROS), and over-concentration of ROS reduces the quality and motility of sperm. Photobiomodulation therapy (PBMT) using red to near-infrared (NIR) light is useful in oxidative stress restoration. It plays a therapeutic role in disorders such as asthenospermia, oligospermia cases, and cryopreserved sperm. It also enhances the metabolic capacity of sperm and increases the low-level and non-harmful intracellular content of Ca²⁺, nitric oxide (NO), and ROS in the stressed cells. Likewise, it modulates survival intracellular pathways and maintains the motility, viability, DNA, and acrosome integrity of sperm. This article reviews the state-of-the-art preclinical and clinical evidence regarding the efficacy of semen PBMT.

Introduction

Today infertility is the most important issue in many countries having population health problems. The rate of infertility in couples is different in various countries throughout the world.

Infertility influences about 20.2% of couples in Iran,¹ 10% in Europe, 15% in the USA, and 17% in Canada. The infertility rate in the world is 12%-15% while this rate is much higher in Iran.² Studies have shown that about 30% to 80% of male infertility cases are related to the adverse effects of oxidative stress. Controlled reactive oxygen species (ROS) concentrations can promote spermatozoal activities under normal situations (e.g. hyperactivation, sperm maturation, acrosome reaction, capacitation, and fertilization). However, increased physiological ROS concentrations lead to oxidative stress that causes molecular damage, sperm motility reduction, and lipid peroxidation, and finally, it may provide a basis for male infertility. Several factors such as genetic abnormalities,³ lifestyle,⁴ varicocele,⁵ drugs ⁶, prolonged exposure of the testis to heat, hypoxia,⁷ and dysfunction in energy metabolism may contribute to oxidative stress in testicular tissue of spermatozoa.⁸ Sperm motility, capacitation, and acrosome response are tightly regulated by adenosine triphosphate (ATP), intracellular Ca²⁺, and nitric oxide (NO) production mitochondria.⁹ Normal physiological levels of ROS regulate the intracellular cascades, and hence, it mediates necessary physiological mechanisms (e.g. hyperactivation, sperm maturation, acrosome reaction, capacitation, and fertilization), while increased physiological ROS concentrations lead to oxidative stress.^8,9 In addition, an increase in the ROS level has also been shown in 40% of infertile men’s semen samples.¹⁰ Photobiomodulation (PBM) has been widely used in clinical methods as fertilizing potential, and its safety and positive effects have been proven in many studies.¹¹ Generally, this light-based method engages the exposure of a low-level laser which exploits the various visible to near-infrared (NIR) (600–1100 nm) wavelength ranges.¹² In this spectrum range, light easily penetrates the tissues, Many structures and molecules are affected, mainly those involved in oxygen delivery, energy production, and light absorption. The mechanical basis of the use of photobiomodulation therapy (PBMT) is related to the intracellular metabolism upregulation by higher ATP production, augmentation of some metabolic pathways, and reduction or induction of ROS.^13-15 PBM beneficial effects depend on time, irradiated area, and other treatment parameters (e.g. dose). The present review aims to provide studies regarding the efficacy of PBMT in the ROS level and sperm motility.

ATP and Sperm Motility

Motility is one of the most features of sperm cells, and it is also very essential for men’s fertility.¹

A lot of energy is needed by the highly specialized cells called spermatozoa. A direct correlation exists between the rate at which ATP is converted to energy and the beat frequency of the flagellum.¹⁶ It is widely acknowledged that there are two primary metabolic routes through which spermatozoa generate ATP: oxidative phosphorylation in the mitochondria and glycolysis in the head and principal piece.¹⁷ Multiple ATP-producing biological pathways are required for the flagellar mobility of the sperm cell, according to the proteome analysis of asthenozoospermic men. Men with asthenozoospermia were shown to have down-regulated levels of the enzymes involved in glycolysis, the tricarboxylic acid cycle, pyruvate metabolism, ketone metabolism, oxidative phosphorylation, and the beta-oxidation of fatty acids. These results suggest that several metabolic pathways may help regulate sperm motility.¹⁸

Two motility types, including activated motility and hyperactivated motility, are seen in spermatozoa at the fertilization site. Both of these motility types need a sufficient energy supply of ATP type which is used by the flagellar dynein-ATPase.

Calcium and Sperm Motility

The main functions of ion channels and transporters located in the sperm tail membrane consist of regulation of the calcium concentration, membrane voltage, and intracellular pH of spermatozoa ([Ca²⁺ ]), and they are necessary for sperm maintenance and fertility.^19,20

Calcium ion is another significant element that acts as an intracellular second messenger. It is necessary for different functions of sperm, such as spermatogenesis, capacitation, acrosome reaction, fertilization, and sperm activity and hyperactivity. The homeostasis of calcium ions in sperm is strictly controlled by the calcium pump because of plasma membrane Ca²⁺ -ATPase activation.²¹ The activity of mitochondria adjusts the Ca²⁺ signals. For instance, the control of the Ca²⁺ signal of mitochondria is essential to regulate both the cellular membrane voltage and particularly pH gradients which drive the generation of ATP.²² Eventually, dysfunction in mitochondria is related to infertility and asthenospermia.^23,24 Mitochondrial dysfunction is the subject of many types of disorders in organs that need a lot of respiratory energy.²⁵

In eukaryotic organisms, cilia and flagella consist of a scaffold of a pair of similar microtubules whose extension of the cellular membrane covers them, and they are powered by dynein ATPase motors. It is well known that augmented ciliary beating and accelerated forward swimming are related to membrane hyperpolarization, whereas ciliary reversal and backward swimming result from depolarization ²⁶. Intracellular calcium concentration ([Ca²⁺ ]) causes depolarization or hyperpolarization by the activation of specific channels in different cell regions (e.g. voltage-dependent Ca²⁺ channels, Ca²⁺ stores). Also, calcium regulates ciliary movement through the NO pathway and the phosphorylation and dephosphorylation of ciliary proteins.²⁷

Reactive Oxygen Species and Sperm Motility

Although ROS can exert useful effects via the regulation of signaling cascades of vital cells, they are considered toxic metabolites. High ROS concentration induces oxidative stress and has harmful effects on the quality of semen, and it has been related to many types of men fertility complications such as cryptorchidism, varicocele, infection of the urogenital tract, presence of bacteria, and idiopathic infertility.²⁸ In seminal plasma, ROS has two sources, Endogenous (varicocele, leucocytes, and immature spermatozoa) and exogenous (alcohol, poisons, radiation, long heat exposure, and smoking), which induce DNA damage in sperm,^29,30 peroxidation of lipid,³¹ and disorder in the structure and function of sperm.³⁰

The mechanism of ROS production and the effects of oxidative stress on sperm are summarized in Figure 1.

Figure 1.

ROS Production and its Effects of Oxidative Stress on Sperm

Spermatozoa can mainly produce ROS in two ways: (1) the oxidase system of nicotinamide adenine dinucleotide phosphate that produces ROS at the plasma membrane of sperm, and (2) the production of ROS at the mitochondrial level.

Spermatozoa have many mitochondria because of their permanent need for energy for motility.³² Elevating the level of dysfunctional spermatozoa in semen results in the production of ROS and affects sperm motility.³³ On the other side, the higher rate of unsaturated fatty acids in sperm and insufficient cells for repairing systems weaken it for lipid peroxidation at high ROS concentration, causing an efflux of ATP and flagellar impairment.³⁴ The main ROS in spermatozoa of humans is superoxide (O₂^–), and it reacts on its own via dismutation reactions to produce hydrogen peroxide (H₂O₂). If transitional metals (e.g. copper and iron) exist, hydroxyl radical (OH^–) production can be induced by H₂O₂ and O₂^– via the Haber–Weiss reaction, which can begin lipid peroxidation cascade, disrupt membrane fluidity, and impair sperm function.

Mechanism of Photobiomodulation on ATP, Ca and ROS

There are low-intensity laser-sensitive photoreceptors in the mitochondria membranes.^35,36 Photon absorption by the photoreceptors activates molecular signals in these receptors and alters the molecular configuration of the cells.^12,37 The signal between the nucleus and mitochondria affects many cellular activities in both pathological and normal conditions,^35,38 although the optimal result of PBM is seen in stressed cells more than it is seen in healthy cells.^39,40 It has already been proven that ROS overproduction occurs through the dysfunction of mitochondria in pathologic conditions.⁴¹

The PBM appears to be the initial stage of the recuperation of oxidative stress since the mitochondria are the primary site for interactions between red/NIR light cells. Additionally, Hamblin observed that the level of ROS decreased under cellular oxidative stress situations in the animal disease models after PBM.¹³ The hypothetical mechanism supposed that in stressed cells, the NO produced in the mitochondria is connected to cytochrome c oxidase; therefore, it competitively moves oxygen, inhibits electron transport, and disrupts the respiratory chain.⁴²

The PBM may cause the separation of NO from binding sites; hence, it leads to oxygen influx, resumes respiration, and generates ROS.^43,44 Besides, the concentrations of NO are raised because of photo-relaxation from other intracellular stores like nitrosylated myoglobin and hemoglobin.^6,45 Additionally, alteration in the respiratory chain changes Ca²⁺ ion flow between cytoplasm and mitochondria.^46,47 The signaling cascade which raises cytoprotection and proliferation of the cells begins with the increased low-level and non-harmful intracellular content of Ca²⁺, NO as well as ROS.⁴⁸ The main underlying mechanism of PBMT in mitochondria is summarized in Figure 2.

Figure 2.

Mechanism of Photobiomodulation Therapy in Mitochondria

Previous studies have stated that a laser increases the rate of cyclooxygenase, Vmax, and ATP values in irradiated sperm, and also a direct relationship exists between the rate of cyclooxygenase and progressive sperm motility (PSM), and ATP level.^49,50 In vitro increase of human sperm motility following PBMT can be potentially useful for the technologies of assisted reproduction. Before the insemination of intrauterine periovulatory, the low-quality semen can be treated to raise the possibility of conception. Before the insemination of oocytes in vitro, the motility of poorer semen samples can be increased for maximizing fertilization of the oocyte. This probably avoids using an injection of intracytoplasmic sperm to attain fertilization.⁵¹

Dose-Dependent Effects of Photobiomodulation

Today assisted reproduction methods in both animals and humans depend upon direct sperm injection into the oocyte and using drugs to improve fertility. These two methods may not be successful in all cases, and they can be more effective by using additional devices for increasing fertility. Also, the ongoing methods might be used in association with accepted IVF techniques for the improvement of treatment outcomes.⁵² Initially, Sato et al showed that the stimulation of laser light affects human spermatozoa with low energy density.⁵³

Some studies have reported the probability of increasing sperm motility following laser irradiation in the sperm of bovines,^4,54 canines,⁵ and humans^32,53,55,56 (Table 1).

Table 1. The Effects of Laser Irradiation on Sperm Motility of Bovines, Canines, and Humans .

Study/Year	Specimen	Light Source	Wavelength	Irradiation parameter	Finding
Salman Yazdi et al, 201357	Human	GaAlAs laser	830 nm	200 mW 4, 6, 10 J/cm2 for 30, 45, 60 min.	The progressive motility significantly increased in all three doses. The highly irradiated group indicated better motility than the other groups. Not statistically significant increase in the level of DNA fragmentations in sperm cells. Reduce swelling cell percentage in the 10 J/cm2 irradiation group
Ban Frangz et al, 201558	Human	LED	850, 625, 660, 470 nm	2.16, 3.92, 5.06, 8.23 mW/cm2	An LED improved sperm motility in asthenozoospermia regardless of the wavelength. The improvement of sperm motility was the largest in 5.06 mW/cm2 470 nm semen samples.
Hasani et al, 202059	Mice	Infrared laser	890 nm	0.03 J/cm2, 30 s, 80 Hz	- The increasing level of serum testosterone. Decrease ROS production, as well as the expression of IL1-α, IL6, and TNF-α genes - Higher improvement in the number of spermatozoa
Espey et al, 202032	Human	Pulsed laser probe	655 nm	25 mW/cm2 4, 6, and 10 J/cm2	- No significant effect on DNA fragmentation - Improved sperm motility and velocity in asthenozoospermic patients - Increase of progressive sperm motility at 6 J/cm2 for asthenozoospermic patients - No change in expression of CD46 protein
Salama et al, 201560	Human	LED	636.6-nm	496 mg/cm2, 1.241 J/cm2 & 2.482 J/cm2 for 2, 5 and 10 minutes	- Increase in sperm motility at the different doses, particularly at 5 min - The progressive motility declined with time(10 min) - Progressive motility higher in the normal semen samples than that in the asthenospermic samples post-irradiation
Iaffaldano et al, 2016 49	Ram	He-Ne laser	632.8 nm	6 m W, 3.96, 6.12 and 9 J/cm2	- Increases in sperm mass motility, progressive motility, ATP contents, and viability in a dose of 6.12 J/cm2 - Lower DNA integrity in the semen samples irradiated at 9 J/cm2
Safian et al, 202161	Human	Diode laser	810 nm	0.6 J/cm2, 23 s, 0.0261 W/cm2	- Decrease ROS and lipid peroxidation - Increase sperm motility and modulate mitochondrial membrane potential
Firestone et al, 201362	Human	Infrared	905 nm	50 m W/cm2 1.5 J/cm2 for 30 seconds	- Increase motility in oligospermia and asthenospermic samples - No increase in DNA damage - Significant changes in sperm motion kinetics
Safian et al, 202063	Human	Diode laser	Red 630 nm	0.05 (W); 23, 46, 92 (s); 0.6, 1.2, 2.4 J/cm2	At 0.6 J/cm2 had significantly decreased viability
			NIR 810 nm	0.05 (W); 23, 46, 92 (s); 0.6, 1.2, 2.4 J/cm2	- Increase PSM in all dose after 15 min - No increased DNA fragmentation index
			Red + NIR 630 + 810 nm	0.6, 1.2, 2.4 J/cm2	- Increased progressive sperm motility in all dose after 60 min - Increased DNA fragmentation index with 2.4 J/cm2
Preece et al, 201752	Human	Red laser light	633 nm	5.66 mW/cm2	- Increases sperm swimming speed - ROS production level that does not cause significant DNA damage - No DNA damage to sperm cells
Fernandes et al, 201564	Bull	AlGaInP	660 nm	30 mW, 4 and 6 J	- Increase in the percentage of live sperm cells in 4 and 6 - Maintained the integrity of the acrosome membrane of living cells in 4 and 6 J - Head side movement and mobile progress were higher in the 4j group compared with 6 J
Shahar et al, 201165	Human	Visible light	600 nm	40 m W/cm2 for 3 min	- Hyper-activated motility - Production of ROS
Iaffaldano et al, 201066	Rabbit	He–Ne	632.8 nm	3.96, 6.12, and 9.00 J/cm2	Motility, viability, and acrosome integrity are mostly preserved with an energy dose of 6.12 J/cm2 in time 0,24 and 48 after irradiation.
Siqueira et al, 201667	Bull	He-Ne	630nm	5, 7.5 and 10 mW during 5 and 10 min in all powers	- 5, 7.5, and 10 mW applied during 10 min improved sperm function - The positive effect of 5 and 10 mW on motility parameters using a 10 min exposure

Abbreviation: GaAlAs, gallium-aluminum-arsenide; DNA, deoxyribonucleic acid; LED, light-emitting diode; ATP, adenosine triphosphate; ROS, reactive oxygen species; IL1-α, Interleukin 1 alpha; IL6, Interleukin 6; TNF-α, tumor necrosis factor; CD46, cluster of differentiation 46; NIR, near-infrared; He-Ne, helium-neon; AlGaInP, aluminium gallium indium phosphide.

Normally, visible light irradiation (600 nm, 40 m W/cm² in 3 min.) created higher hyperactivated motility and produced ROS.⁶⁵ Nevertheless, previous studies assessed the PBM effect on normal and fresh sperm of humans only in the range of red to NIR light. They showed that PSM increases in the exposure of all experimental wavelengths. The shortest time of radiation (23 seconds) in the NIR laser at the energy density sample of 0.6 J/cm² and after 60 minutes of exposure created the best PSM result. In addition, the DNA fragmentation index (DFI) did not increase by NIR.⁶³ Based on various dose responses, it seems that shorter radiation of PMB with NIR compared to red light has more useful effects on the motility of sperm with no DNA damage in the sample of fresh and normal semen.

One study assessed the fresh samples of human semen in asthenozoospermic patients and stated that laser energy doses of 4 and 6 J/cm² with the exposure time of 0, 0.5, 1, 1.5, and 2 hours of radiation increased the motility and velocity of sperm. PBM showed a non-significant effect on the expression of CD46, a biomarker of acrosome integrity, and the fragmentation level of DNA.³² In another study, an improvement in sperm motility of asthenozoospermia patients was observed after using PBM. They applied 4 treatments with 3 minutes. of PBM protocols including (a) 850 nm with 2.16 mW/cm², (b) 625, 660, and 850 nm with 3.92 mW/cm², (c) 470 nm with 5.06 mW/cm² and, (d) 470, 625, and 660 nm with 8.23 mW/cm². They showed that these protocols significantly increase the proportion of quick progressive sperm and decrease the immotile sperm ratio.⁵⁸ In preliminary studies, Firestone et al showed that utilizing an infrared laser pulse for irradiation (905 nm, duration of 30 seconds, and 50 mW/cm²) reaches a motility increase of 85% in asthenospermic and oligospermia human groups after 30 minutes of exposure. After 2 hours, DNA damage showed a non-significant increase compared to the control group. They suggested that PBM does not enhance DNA damage and has a positive short-time effect on the motility of treated spermatozoa.⁶²

As mentioned above, the protective effects of light-emitting diodes (LEDs) and lasers increase the ability to fertilize, the motility of sperm, the reaction of acrosome,⁶⁸ and the defenses of antioxidants⁶⁹ in different conditions (e.g. asthenospermia). On this subject, Salama et al, in their studies, showed that a light LED (636.6 nm, duration of 2, 5, and 10 minutes for 0.496, 1.241, and 2.482 J/cm² respectively) in normal and asthenospermic men increased the sperm motility at different doses, particularly at 5 minutes, and the progressive motility especially decreased over time from 5 to 10 minutes. Following the application of light, an increase in sperm motility was seen in both types. Nevertheless, the increased level of progressive motility was significantly lower only at the 2-minute point of the asthenospermia group than in the control semen group.⁶⁰ In general, results show that PBM, regardless of its wavelength, increases the motility of sperm in asthenozoospermia.

Also, Hasani et al showed that photobiomodulation (890 nm, 0.03 J/cm², 30 seconds for each testis) improves the motility of sperm and decreases oligospermia caused by scrotal hyperthermia in a mouse model.⁵⁹ In general, results show that PBM, regardless of its wavelength, increases the motility of sperm in asthenozoospermia. Thawing and freezing of sperm cause the production of ROS at destructive levels.⁷⁰

ROS elevated levels impair the cellular plasma membrane of sperms via the peroxidation of lipids and the formation of stable products (e.g. malondialdehyde in cells) ⁷¹. In this regard, Peerce et al, in some interesting studies, assessed the effect of red light irradiation (633 nm, 5.66 mW/cm² with 35 minutes’ duration) on frozen healthy human sperm samples, and they observed a significant increase in swimming speed with little or no production of DNA damage in sperm cells, but the levels of ROS production were not high enough to create significant DNA harm.⁵²

Safian et al studied the quality of human sperm characteristics via cryopreservation. They observed that applying PBM preconditioning (810 nm) before thawing and freezing procedures of sperm can maintain human spermatozoa versus peroxidation of lipids and increase ROS levels and PSM of cryopreserved human sperm after thawing.⁶¹

In a notable series of investigations, Iaffaldano et al estimated the helium-neon laser irradiation (632.8 at 3.96, 6.12, and 9 J/cm²), and they showed that cryopreserved ram sperm increases mass sperm and progressive motility, viability, DNA and Acrosome integrity, and content of ATP.⁴⁹ In another study, the same authors assessed the He–Ne irradiation (632.8 nm with energy doses of 3.96, 6.12, and 9.00 J/cm²) on rabbits’ sperm parameters. Viability, motility, and acrosome integrity are mainly protected with an energy dose of 6.12 J/cm² in time. There was a slight increase in the motility of irradiation samples and integrity of sperm compared to the control group at the time zero, as well as a particularly significant increase in an energy dose of 6.12 J/cm² after 24 and 48 hours of irradiation.⁶⁶ AlGaInP irradiation (660 nm in two doses of 4 and 6 J) before cryopreservation caused statistical differences in the percentage of cell motility with an increase of 4 J in the proportion of acrosome integrity and live sperm cells in connection with control cells when subjected to low-power laser irradiation in two disparate doses.⁶⁴ Likewise, Salman Yazdi et al showed that the GaAlAs laser (830 nm, 200 m W and 4, 6, 10 J/cm² for 30, 45, and 60 minutes) significantly increased the progressive motility in all three doses. The highly irradiated group indicated better motility than the other groups, and no significant increase was observed in the level of DNA fragmentation in sperm cells.⁵⁷

Siqueira et al investigated the effect of the He-Ne laser (633 nm) on the functions of frozen bovine sperm and simultaneously assessed the effect of various times and

output powers of irradiation. Their results showed significant effects related to power while applying 10-minute irradiation on the parameters of motility and the potential of mitochondria. Thus, it seems that the effect of PBMT depends on not only fluency or doses but also irradiation power and exposure duration.⁶⁷ The transcription factors (e.g. NF-κB) can be activated by involved photons, which simulate more ATP and produce less ROS. The enhancement of PBM effects seen in clinics is caused by gene products.⁷² It is possible to hypothesize that the mild oxidative stress stimulation of the sperm cells before freezing may be responsible for the beneficial effects of PBM preconditioning.

Conclusion

Since sperm contains large quantities of mitochondria, the application of red to NIR lights (600-1100) for the treatment of low-quality semen is very attractive. The main problem until now has been to get enough light in the sperm to achieve the beneficial effects. The activation of intracellular signaling and transcription factors (e.g. NF-κB) simulate more ATP and produce less ROS. PBMT has the most important effects on improving sperm motility, stimulating antioxidant defenses, and increasing fertility sperm motility deficits associated with many male infertility disorders. The overall results from extensive preclinical and clinical studies in the sperm PBM field suggest that the modest levels of red and NIR light show stimulatory effects without significant DNA damage, decrease ROS levels, and could be activated by involved photons. The transcribed products of genes are responsible for improving the effects of PBM observed in clinics.

Conflict of Interests

The authors declare that there is no conflict of interest.

Ethical Considerations

Not applicable.

Please cite this article as follows: Poorhassan M, Gholaminejhad M, Ahmadi H, Mehboudi L, Chahar Kameh M, Pirani M, et al. Preclinical and clinical applications of photobiomodulation therapy in sperm motility: a narrative review. J Lasers Med Sci. 2022;13:e75. doi:10.34172/ jlms.2022.75.