Photobiomodulation Triple Treatment in Peripheral Nerve Injury: Nerve and Muscle Response

Neuroprotective Potential of Photobiomodulation Therapy: Mitigating Amyloid-Beta Accumulation and Modulating Acetylcholine Levels in an In Vitro Model of Alzheimer's Disease

Objective: To investigate the effects of photobiomodulation therapy (PBMT) at 660 and 810 nm on amyloid-beta (Aβ)42-induced toxicity in differentiated SH-SY5Y cells and to assess its impact on Aβ42 accumulation and cholinergic neurotransmission. Background: Alzheimer's disease (AD) is characterized by the accumulation of Aβ peptides, leading to neurodegeneration, cholinergic deficit, and cognitive decline. PBMT has emerged as a potential therapeutic approach to mitigate Aβ-induced toxicity and enhance cholinergic function. Methods: Differentiated neurons were treated with 1 μM Aβ42 for 1 day, followed by daily PBMT at wavelengths of 660 and 810 nm for 7 days. Treatments used LEDs emitting continuous wave light at a power density of 5 mW/cm2 for 10 min daily to achieve an energy density of 3 J/cm2. Results: Differentiated SH-SY5Y cells exhibited increased Aβ42 aggregation, neurite retraction, and reduced cell viability. PBMT at 810 nm significantly mitigated the Aβ42-induced toxicity in these cells, as evidenced by reduced Aβ42 aggregation, neurite retraction, and improved cell viability and neuronal morphology. Notably, this treatment also restored acetylcholine levels in the neurons exposed to Aβ42. Conclusions: PBMT at 810 nm effectively reduces Aβ42-induced toxicity and supports neuronal survival, highlighting its neuroprotective effects on cholinergic neurons. By shedding light on the impact of low-level light therapy on Aβ42 accumulation and cellular processes. These findings advocate for further research to elucidate the mechanisms of PBMT and validate its clinical relevance in AD management.

Delayed repair of the facial nerve and its negative impacts on nerve and muscle regeneration

Background

In this experimental protocol, we evaluated the immediate and delayed repair of the buccal branch of the facial nerve (BBFN) with heterologous fibrin biopolymer (HFB) as a coaptation medium and the use of photobiomodulation (PBM), performing functional and histomorphometric analysis of the BBFN and perioral muscles.

Methods

Twenty-eight rats were divided into eight groups using the BBFN bilaterally (the left nerve was used for PBM), namely: G1 - control group, right BBFN (without injury); G2 - control group, left BBFN (without injury + PBM); G3 - Denervated right BBFN (neurotmesis); G4 - Denervated left BBFN (neurotmesis + PBM); G5 - Immediate repair of right BBFN (neurotmesis + HFB); G6 - Immediate repair of left BBFN (neurotmesis + HFB + PBM); G7 - Delayed repair of right BBFN (neurotmesis + HFB); G8 - Delayed repair of left BBFN (neurotmesis + HFB + PBM). Delayed repair occurred after two weeks of denervation. All animals were sacrificed after six weeks postoperatively.

Results

In the parameters of the BBFN, we observed inferior results in the groups with delayed repair, in relation to the groups with immediate repair, with a significant difference (p < 0.05) in the diameter of the nerve fiber, the axon, and the thickness of the myelin sheath of the group with immediate repair with PBM compared to the other experimental groups. In measuring the muscle fiber area, groups G7 (826.4 ± 69.90) and G8 (836.7 ± 96.44) were similar to G5 (882.8 ± 70.51). In the functional analysis, the G7 (4.10 ± 0.07) and G8 (4.12 ± 0.08) groups presented normal parameters.

Conclusion

We demonstrated that delayed repair of BBFN is possible with HFB, but with worse results compared to immediate repair, and that PBM has a positive influence on nerve regeneration results in immediate repair.

Long-Term Survival and Functional Recovery of Cryopreserved Vascularized Groin Flap and Below-the-Knee Rat Limb Transplants

Effective cryopreservation of large tissues, limbs, and organs has the potential to revolutionize medical post-trauma reconstruction options and organ preservation and transplantation procedures. To date, vitrification and directional freezing are the only viable methods for long-term organ or tissue preservation, but are of limited clinical relevance. This work aimed to develop a vitrification-based approach that will enable the long-term survival and functional recovery of large tissues and limbs following transplantation. The presented novel two-stage cooling process involves rapid specimen cooling to subzero temperatures, followed by gradual cooling to the vitrification solution (VS) and tissue glass transition temperature. Flap cooling and storage were only feasible at temperatures equal to or slightly lower than the VS Tg (i.e., -135°C). Vascularized rat groin flaps and below-the-knee (BTK) hind limb transplants cryopreserved using this approach exhibited long-term survival (>30 days) following transplantation to rats. BTK-limb recovery included hair regrowth, normal peripheral blood flow, and normal skin, fat, and muscle histology. Above all, BTK limbs were reinnervated, enabling rats to sense pain in the cryopreserved limb. These findings provide a strong foundation for the development of a long-term large-tissue, limb and organ preservation protocol for clinical use.

Relationship between Laser Intensity at the Peripheral Nerve and Inhibitory Effect of Percutaneous Photobiomodulation on Neuronal Firing in a Rat Spinal Dorsal Horn

Photobiomodulation is an effective treatment for pain. We previously reported that the direct laser irradiation of the exposed sciatic nerve inhibited firing in the rat spinal dorsal horn evoked by mechanical stimulation, corresponding to the noxious stimulus. However, percutaneous laser irradiation is used in clinical practice, and it is unclear whether it can inhibit the firing of the dorsal horn. In this study, we investigated whether the percutaneous laser irradiation of the sciatic nerve inhibits firing. Electrodes were inserted into the lamina II of the dorsal horn, and mechanical stimulation was applied using von Frey filaments (vFFs) with both pre and post laser irradiation. Our findings show that percutaneous laser irradiation inhibited 26.0 g vFF-evoked firing, which corresponded to the noxious stimulus, but did not inhibit 0.6 g and 8.0 g vFF-evoked firing. The post- (15 min after) and pre-irradiation firing ratios were almost the same as those for direct and percutaneous irradiation. A photodiode sensor implanted in the sciatic nerve showed that the power density reaching the sciatic nerve percutaneously was attenuated to approximately 10% of that on the skin. The relationship between the laser intensity reaching the nerve and its effect could be potentially useful for a more appropriate setting of laser conditions in clinical practice.

Morphofunctional Improvement of the Facial Nerve and Muscles with Repair Using Heterologous Fibrin Biopolymer and Photobiomodulation

Peripheral nerve injuries impair the patient's functional capacity, including those occurring in the facial nerve, which require effective medical treatment. Thus, we investigated the use of heterologous fibrin biopolymer (HFB) in the repair of the buccal branch of the facial nerve (BBFN) associated with photobiomodulation (PBM), using a low-level laser (LLLT), analyzing the effects on axons, muscles facials, and functional recovery. This experimental study used twenty-one rats randomly divided into three groups of seven animals, using the BBFN bilaterally (the left nerve was used for LLLT): Control group-normal and laser (CGn and CGl); Denervated group-normal and laser (DGn and DGl); Experimental Repair Group-normal and laser (ERGn and ERGl). The photobiomodulation protocol began in the immediate postoperative period and continued for 5 weeks with a weekly application. After 6 weeks of the experiment, the BBFN and the perioral muscles were collected. A significant difference (p < 0.05) was observed in nerve fiber diameter (7.10 ± 0.25 µm and 8.00 ± 0.36 µm, respectively) and axon diameter (3.31 ± 0.19 µm and 4.07 ± 0.27 µm, respectively) between ERGn and ERGl. In the area of muscle fibers, ERGl was similar to GC. In the functional analysis, the ERGn and the ERGI (4.38 ± 0.10) and the ERGI (4.56 ± 0.11) showed parameters of normality. We show that HFB and PBM had positive effects on the morphological and functional stimulation of the buccal branch of the facial nerve, being an alternative and favorable for the regeneration of severe injuries.

TISSUE EXPRESSION OF NEURONAL PROTEINS DURING SCIATIC NERVE REGENERATION AND INFLUENCE OF DIFFERENT SPECTRUM LASER RADIATION

OBJECTIVE

Aim: To determine the effect of laser irradiation of different spectrum on the expression of neuronal proteins (GFAP, S100, NSE and NF-L) in the sciatic nerve during its regeneration after crossing and surgical suturing.

PATIENTS AND METHODS

Materials and methods: The experiment was performed on 60 laboratory rats of the Wistar line (200-250 g) with crossing of the left sciatic nerve and sutur¬ing with an epineural suture end to end 30 minutes after neurotomy. 90 days later, an immunohistochemical study was performed using specific antibodies (Thermo Fisher Scientific; USA).

RESULTS

Results: A study of the marker of non-myelin Schwann GFAP cells showed their pronounced activation with germination in nerve thickness and the formation of weaves of processes around regenerated nerve fibers. The number of S-100-positive myelin Schwann cells decreased, the heterogeneity of their color and the loss of processes were determined. It showed a general decrease in the intensity of NSE- and NF-L-positive staining of nerve fibers regenerated after neurotomy, which was less pronounced when irradiated with a laser with a wavelength of 450-480 nm and 520 nm.

CONCLUSION

Conclusions: In general, the use of laser radiation had a positive effect on the repair of nerve fibers after neurotomy. According to the immunohistochemical study of neuromarkers, the effect of laser irradiation of the blue spectrum was the most effective.

Application of Fibrin Associated with Photobiomodulation as a Promising Strategy to Improve Regeneration in Tissue Engineering: A Systematic Review

Fibrin, derived from proteins involved in blood clotting (fibrinogen and thrombin), is a biopolymer with different applications in the health area since it has hemostasis, biocompatible and three-dimensional physical structure properties, and can be used as scaffolds in tissue regeneration or drug delivery system for cells and/or growth factors. Fibrin alone or together with other biomaterials, has been indicated for use as a biological support to promote the regeneration of stem cells, bone, peripheral nerves, and other injured tissues. In its diversity of forms of application and constitution, there are platelet-rich fibrin (PRF), Leukocyte- and platelet-rich fibrin (L-PRF), fibrin glue or fibrin sealant, and hydrogels. In order to increase fibrin properties, adjuvant therapies can be combined to favor tissue repair, such as photobiomodulation (PBM), by low-level laser therapy (LLLT) or LEDs (Light Emitting Diode). Therefore, this systematic review aimed to evaluate the relationship between PBM and the use of fibrin compounds, referring to the results of previous studies published in PubMed/MEDLINE, Scopus and Web of Science databases. The descriptors “fibrin AND low-level laser therapy” and “fibrin AND photobiomodulation” were used, without restriction on publication time. The bibliographic search found 44 articles in PubMed/MEDLINE, of which 26 were excluded due to duplicity or being outside the eligibility criteria. We also found 40 articles in Web of Science and selected 1 article, 152 articles in Scopus and no article selected, totaling 19 articles for qualitative analysis. The fibrin type most used in combination with PBM was fibrin sealant, mainly heterologous, followed by PRF or L-PRF. In PBM, the gallium-aluminum-arsenide (GaAlAs) laser prevailed, with a wavelength of 830 nm, followed by 810 nm. Among the preclinical studies, the most researched association of fibrin and PBM was the use of fibrin sealants in bone or nerve injuries; in clinical studies, the association of PBM with medication-related treatments osteonecrosis of the jaw (MRONJ). Therefore, there is scientific evidence of the contribution of PBM on fibrin composites, constituting a supporting therapy that acts by stimulating cell activity, angiogenesis, osteoblast activation, axonal growth, anti-inflammatory and anti-edema action, increased collagen synthesis and its maturation, as well as biomolecules.

Negative neuromuscular and functional repercussion of forced swimming after axonotmesis

Peripheral nerve injuries are cause of sensory disturbances and in functional abilities, and are associated personal and social costs. Strategies that maximize nerve regeneration and functional recovery are necessary, the exercise is an option. This study evaluated the effects of forced swimming exercise on neuromuscular histomorphometry and on functional recovery in a median nerve crush model. Sixteen Wistar rats underwent median nerve crush and were divided into control group (CG) and swimming group (SG). The forced swimming protocol started one week after the injury and was performed for 1 hr a day, 5 days per week, for 2 weeks. The rats swam with an overload of 5% and 10% of body weight in the first and second week, respectively. The functional recovery was assessed in three moments using the grasping test. On day 21, fragments of the median nerve and of the forearm flexors muscles were removed for histomorphometric analysis. The SG had functional recovery impaired (P<0.001) and presented lower myelinated fibers number, fiber and axon minimal diameter, myelin thickness and g-ratio in the proximal e distal segments of the median nerve (P<0.005) and area muscle fiber (P<0.005) than CG. Also, the SG presented a number of capillaries in the proximal segments of the median nerve greater than CG (P<0.005). The exercise protocol used in this study impaired the regeneration of the median nerve and negatively influenced the functional recovery.

Effect of Photobiomodulation on Denervation-Induced Skeletal Muscle Atrophy and Autophagy: A Study in Mice

OBJECTIVE

The purpose of this study was to investigate whether photobiomodulation (PBM) can protect against and attenuate muscle atrophy owing to complete peripheral nerve lesion in mice by acting on autophagy.

METHODS

C57BL/10 mice underwent right sciatic nerve transection to induce tibialis anterior muscle atrophy. After 6 hours of denervation, the mice received PBM (wavelength, 830 nm) daily, transcutaneously over the tibialis anterior muscle region for 5 or 14 days. Some mice with sciatic nerve lesion did not receive PBM. Mice that did not have sciatic nerve lesion and PBM were used as controls. After 5 and 14 days, the right tibialis anterior muscle was examined using histomorphometric (cross-sectional area of muscle fibers), Western blot (levels of the autophagy marker LC3), and immunofluorescence analyses (number of LC3 puncta in the muscle fibers).

RESULTS

The cross-sectional area of the tibialis anterior muscle fibers decreased after 5 and 14 days of denervation. PBM protected against muscle fiber atrophy after 5 days of denervation and attenuated muscle fiber atrophy after 14 days of denervation. After 5 days of muscle denervation, autophagy did not change, as demonstrated by the comparable levels of LC3-I/II ratio and LC3 puncta between the controls and the mice with atrophic muscle; PBM did not change this profile. After 14 days of denervation, an increased LC3-I/II ratio suggested an ongoing autophagy, which was not affected by PBM.

CONCLUSION

PBM attenuated the tibialis anterior muscle atrophy induced by sciatic nerve transection in the mice after at least 5 and 14 days of muscle denervation, without affecting autophagy. The transient protective effect of PBM was observed as early as 5 days after the of complete nerve lesion.

Photobiomodulation Therapy Applied after 6 Months for the Management of a Severe Inferior Alveolar Nerve Injury

Despite its significant negative impact on the quality of life, the methods for the management of the inferior alveolar nerve (IAN) injury are still limited. In this case report, the patient did not show any improvement from the day of the iatrogenic accident until 6 months. A significant improvement of the symptoms started to appear only at 6 months when PBMT was applied. A total of 42 sessions of PBMT took place. The application zone included intraoral and extraoral areas. The parameters were: Delivery power of 0.1 W, for 40 s, continuous wave (CW), contact mode, and delivered energy of 4 J. The delivered energy density related to the fiber diameter was 1415 J/cm². Each treated point was considered to be 1 cm² of diameter. At the end of the treatment, all of the symptoms disappeared except for an abnormal sensation on touching the mucosa and gingiva of the concerned area. No side effects were noted. This case report shows that PBMT can be a very promising approach for the management of severe cases that are not improving with conventional methods.

Effects of Photobiomodulation Therapy (LED 630 nm) on Muscle and Nerve Histomorphometry after Axonotmesis

Peripheral injuries constitute a substantial clinical problem with unsatisfactory treatment. The study's objective was to analyze the effects of photobiomodulation therapy (PBMT) on median nerve regeneration and muscle recovery after axonotmesis. Twenty-four rats were randomized into three groups: control (CG), injury (IG), and LED therapy (LEDG). A 630 ± 20 nm (300-mW) LED was placed in contact with the skin. One point over the injury site was irradiated for 30 s, delivering 9 J (9 J cm-2 ). PBMT irradiation was performed once daily for 5 days followed by two-day interval and then more five consecutive days of treatment. Proximal and distal segments of the nerve and flexors muscles were removed for histomorphometric analysis using H&E staining for muscles and osmium tetroxide for nerves. The myelinated fiber and axon diameter and the myelin sheath thickness were greater in the proximal and distal nerve segments in the LEDG compared to the IG (P ≤ 0.05). The number of myelinated fibers was greater in the distal segment of the LEDG (P ≤ 0.05). The area, circumference, and diameter of the muscle fibers were larger in the LEDG than in the IG (P ≤ 0.05). The PBMT protocol used favored axonal regeneration and muscle recovery.

Efficacy of multi-wave locked system laser therapy on nerve regeneration after crushing in Wister rats

[Purpose] To investigate the efficacy of the multi-wave locked system laser therapy on the regeneration of peripheral nerve injuries by evaluating the functional, electrophysiological, and morphological changes of the crushed sciatic nerve in Wistar rats. [Materials and Methods] Sixty male Wistar rats (200–250 g) were randomly assigned to control negative, control positive, or laser groups and subjected to no laser therapy or crushing, to crushing without laser therapy, or crushing followed by multi-wave locked system laser therapy five times/week for four weeks (power=1 W, energy density=10 J/cm², total energy=100 J), respectively. Functional, electrophysiological, and morphometric analyses were performed before and 7, 15, 21, and 28 days after crushing. The sciatic functional index, compound motor action potential amplitude, motor nerve conduction velocity, and nerve and myelin sheath diameters were measured. [Results] The sciatic functional index value decreased significantly, while the compound motor action potential amplitude, motor nerve conduction velocity, nerve diameter, and myelin sheath diameter increased significantly in the laser group post-treatment compared to the values in the control groups. [Conclusion] Multi-wave locked system laser therapy was effective in accelerating the regeneration of crushed sciatic nerves in Wistar rats.

Effects of photobiomodulation on different application points and different phases of complex regional pain syndrome type I in the experimental model

BACKGROUND

Complex regional pain syndrome type I (CRPS-I) consists of disorders caused by spontaneous pain or induced by some stimulus. The objective was to verify the effects of photobiomodulation (PBM) using 830 nm wavelength light at the affected paw and involved spinal cord segments during the warm or acute phase.

METHODS

Fifty-six mice were randomized into seven groups. Group (G) 1 was the placebo group; G2 and G3 were treated with PBM on the paw in the warm and acute phase, respectively; G4 and G5 treated with PBM on involved spinal cord segments in the warm and acute phase, respectively; G6 and G7 treated with PBM on paw and involved spinal cord segments in the warm and acute phase, respectively. Edema degree, thermal and mechanical hyperalgesia, skin temperature, and functional quality of gait (Sciatic Static Index [SSI] and Sciatic Functional Index [SFI]) were evaluated.

RESULTS

Edema was lower in G3 and G7, and these were the only groups to return to baseline values at the end of treatment. For thermal hyperalgesia only G3 and G5 returned to baseline values. Regarding mechanical hyperalgesia, the groups did not show significant differences. Thermography showed increased temperature in all groups on the seventh day. In SSI and SFI assessment, G3 and G7 showed lower values when compared to G1, respectively.

CONCLUSIONS

PBM irradiation in the acute phase and in the affected paw showed better results in reducing edema, thermal and mechanical hyperalgesia, and in improving gait quality, demonstrating efficacy in treatment of CRPS-I symptoms.

On-Site Laser Photobiomodulation Treatment of Crushed Muscle Due to Prolonged Pressure in Rats

BACKGROUND AND OBJECTIVES

Crush injuries and prolonged pressure on muscles lead to bruises and sprains and, in most of the cases, cause distraction of the muscle and release of particles into the blood stream, causing renal and systemic complications in severe cases. Laser photobiomodulation treatment (i.e., laser phototherapy) is a method suggested to decrease the pressure damage in the first 24-48 hours after muscle injury, allowing a faster and more complete physical rehabilitation. We studied the efficacy of non-invasive laser photobiomodulation treatment as an on-site treatment for crush-injured gastrocnemius muscles, developing a moderate muscle crush injury model and aiming at decreasing damage extent while regaining physical competence faster.

STUDY DESIGN/MATERIALS AND METHODS

Muscle crush injury was performed on 30 female Wistar rats using direct pressure for 10 minutes on the gastrocnemius muscle in both left and right hindlimbs. Immediately after the injury, only the left hindlimb were irradiated for 16 minutes (with 780 nm laser with a power of 250 mW, the energy at the target was 240 J, and the fluence was 1019 J/cm² ) for 1, 3, or 7 consecutive days, and sacrificed accordingly. During the follow-up period, 1, 3, or 7 days, both gastrocnemius muscles (of the treated and untreated hindlimbs) were evaluated for electrophysiology and functionality.

RESULTS

The laser photobiomodulation treatment showed a significant electrophysiological and functional recovery of the gastrocnemius muscle during the first 3 days after injury, in comparison with the untreated hindlimb.

CONCLUSIONS

These preliminary results are promising, showing a significant effect of the laser photobiomodulation treatment during the first 3 days after the induction of the muscle crush injury, which is the most critical period in the clinical aspect. These findings suggest a therapeutic approach, which may help restore the muscle after crush injury.

Photobiomodulation Promotes Neuronal Axon Regeneration After Oxidative Stress and Induces a Change in Polarization from M1 to M2 in Macrophages via Stimulation of CCL2 in Neurons: Relevance to Spinal Cord Injury

To study the effect of photobiomodulation (PBM) on axon regeneration and secretion change of dorsal root ganglion (DRG) under oxidative stress after spinal cord injury (SCI), and further explore the effect of changes in DRG secretion caused by PBM on the polarization of macrophages. The PBM-DRG model was constructed to perform PBM on neurons under oxidative stress simulated in vitro. And the irradiation conditions were as follows: wavelength, 810 nm; power density, 2 mW/cm²; irradiation area, 4.5 cm²; and irradiation time, 440 s. Then resulted in an energy of 4 J (2 mW/cm² × 4.5 cm² × 440 s). About 100 μM H₂0₂ was added to the culture medium to simulate oxidative stress after SCI. An ROS (reactive oxygen species) assay kit was used to measure ROS contend in the DRG. The survival level of the neurons was measured using the CCK-8 method, and the axon regeneration of neurons was observed by using immunofluorescence. The secretion level of CCL2 from DRG was determined by RT-qPCR and ELISA. Further culturing macrophages of DRG-conditioned medium culture, the expression level of iNOS and Arg-1 in macrophages was assessed using Western blot analysis. The expression level of TNF-α and IL-1β was determined by ELISA. After adding the neutralizing antibody of CCL2 to the DRG neuron-conditioned medium following PBM irradiation to culture macrophages to observe the effects on macrophage polarization and secretion. PBM could reduce ROS levels in neurons, increase neuronal survival under oxidative stress, and promote neuronal axon regeneration. In addition, PBM could also promote CCL2 secretion by DRG under oxidative stress. By constructing a DRG supernatant-M1 macrophage adoptive culture model, we found that the supernatant of DRG after PBM intervention could reduce the expression level of iNOS and the secretion of TNF-α and IL-1β in M1 macrophages; at the same time, it could also up-regulate the expression of Arg-1, one of the markers of M2 macrophages. Furthermore, these effects could be prevented by the addition of neutralizing antibodies of CCL2. PBM could promote survival and axonal regeneration of DRG under SCI oxidative stress, increase the secretion level of CCL2 by DRG, and this change can reduce the polarization of macrophages to M1, further indicating that PBM could promote spinal cord injury repair.

Photobiomodulation reduces nociception and edema in a CFA-induced muscle pain model: effects of LLLT and LEDT

Photobiomodulation therapy (PBMT) is an effective therapeutic strategy and a noninvasive method to improve the regulation of inflammation and pain. Our aim was to examine the effects of different doses of PBMT on improvement of edematogenic and nociceptive responses in a myositis model in rats. We administered complete Freund's adjuvant (CFA) into the gastrocnemius muscle (GS) of rats to induce myositis and observe the effect of PBMT using different doses of energy and two types of light sources, a low-level laser (LLL) and light emitting diodes (LED). For this, we evaluated the effects of these different energies to improve nociceptive and edematogenic responses using behavioural tests. In addition, we analysed histological images in animals with myositis induced by CFA. The administration of CFA to the GS induced increased cellular infiltrates, edema and a nociceptive response when compared to animals without myositis. When we treated the CFA-induced myositis animals with PBMT (LLLT or LEDT), we observed a decrease in nociception and edema formation. Our results demonstrated that only the major energy for both the LED and LLL was able to remain in a homogeneous form throughout the period analyzed. Based on our results, we suggest that both LLLT and LEDT using the highest dose (3 J) could be an alternative treatment for myositis in rats.

Green Tea Polyphenols Promote Functional Recovery from Peripheral Nerve Injury in Rats

Background

Peripheral nerve injury (PNI) is a common and progressive disorder with sensory and motor deficits in the peripheral nervous system (PNS). Treatment is difficult, with unfavorable prognosis. Green tea polyphenols (GTPs) exert neuroprotective effects on regeneration of the central nervous system (CNS). However, the effects of GTPs on functional recovery of the PNS have not been fully characterized. Consequently, the present study investigated the effects of GTPs on nerve regeneration of rats with PNI.

Material/Methods

The model of PNI was established in rats by sciatic nerve injury (SNI). Adult male Wistar rats with SNI were randomly divided into a vehicle group and a GTPs group. The compound muscle action potential (CMAP) of rat sciatic nerves (SN) was measured using the CM6240 physiological signal acquisition and processing system. The wet weight of the triceps muscle was determined using an analytical balance. The number of myelinated nerve fibers was counted under an optical microscope. Ultrastructure of the regenerated nerves in SN was observed by transmission electron microscopy. The mRNA and protein expression of nerve growth factor (NGF), growth-associated protein-43 (GAP-43), neurofilament 200 (NF200), and myelin-associated glycoprotein (MAG) in SN stumps were measured by real-time quantification PCR (RT-qPCR) and Western blot, respectively.

Results

In rats with SNI, GTPs relieved the adhesion between nerve anastomosis and surrounding tissues, and significantly increased nerve conduction velocity, wet weight of the triceps muscle, and development and axonal regeneration of myelinated nerve fibers. Moreover, GTPs promoted the mRNA and protein expressions of NGF, GAP-43, NF200, and MAG in SN stumps.

Conclusions

GTPs promotes nerve regeneration in rats with SNI.

Neurite growth of trigeminal ganglion neurons in vitro with near-infrared light irradiation

Trigeminal ganglion (TG) neurons play an essential role in the sensory nerves of the face. Damaged TG neurons resulting from the accidental and non-intentional nerve lesions, commonly identified as neuropathic pain, which is known to cause intense pain and sensory abnormalities. For the treatment, surgical methods are conducted when the pharmacological treatment fails to provide satisfactory recovery. However, the process of surgery or drug intake can burden the patient or cause side effects. One of the logical choices of study becomes photobiomodulation (PBM) referred to as therapeutic approaches based on the interactions of visible or near-infrared (NIR) photons with biomolecules inside cells or tissues. In this study, we constructed a PBM illumination setup to stimulate the cultured primary TG neurons and compared the growth morphology between the non-irradiated control group and irradiation group with NIR laser of 808 nm wavelength. In addition, we applied various radiant exposures of 1, 2, and 10 J/cm² with different pulse frequencies of 1, 10, and 100 Hz. We found that PBM could promote neurite growth of TG neurons, and it works at relatively low energy densities at 1 and 2 J/cm². The irradiation group in the pulsed wave mode with the frequency of 10 Hz was found to be the most effective when compared to other frequencies. Thus, PBM on TG neurons facilitated neuronal growth in vitro in a dose and frequency-dependent fashion. PBM may provide a potential therapeutic approach to treat damaged peripheral nerves.

THE ACTION OF SERICIN PROTEIN ON INITIAL NERVE REPAIR, ASSOCIATED OR NOT WITH SWIMMING IN WISTAR RATS

ABSTRACT Objective: To analyze the effects of sericin treatment, associated or not with swimming with load exercise, on initial sciatic nerve repair after compression in Wistar rats. Methods: Forty animals were divided into five groups: control, injury, injury-sericin, injury-swimming and injury-sericin-swimming. During the axonotmesis procedure, the sericin was applied to the injury-sericin and injury-sericin-swimming groups. The injury-swimming and injury-sericin-swimming groups performed the swimming with load exercise for five days, beginning on the third postoperative day (PO), and were evaluated for function, nociception and allodynia. Euthanasia was performed on the 8th PO day and fragments of the nerve were collected and prepared for quantitative and descriptive analysis in relation to the total amount of viable nerve fibers and non-viable nerve fibers, nerve fiber diameter, axon diameter and myelin sheath thickness. Results: There was no significant improvement in the sciatic functional index up to the eighth day. The Von Frey test of the surgical scar and plantar fascia indicated a reduction in pain and allodynia for the injury-swimming and injury-sericin-swimming groups. The morphological analysis presented similar characteristics in the injury-sericin, injury-swimming and injury-sericin-swimming groups, but there was a significant difference in the number of smaller non-viable nerve fibers in the injury-swimming and injury-sericin-swimming groups as compared to the others. Conclusions: Isolated sericin protein presented proinflammatory characteristics. There was improvement of allodynia and a decrease in the pain at the site of the surgical incision, possibly linked to an aquatic effect. There was no acceleration of nerve repair on the eighth day after the injury. Level of Evidence I; High quality randomized clinical trial with or without statistically significant difference, but with narrow confidence intervals.

The effect of 808 nm and 905 nm wavelength light on recovery after spinal cord injury

We investigated the effect of a Multiwave Locked System laser (with a simultaneous 808 nm continuous emission and 905 nm pulse emission) on the spinal cord after spinal cord injury (SCI) in rats. The functional recovery was measured by locomotor tests (BBB, Beam walking, MotoRater) and a sensitivity test (Plantar test). The locomotor tests showed a significant improvement of the locomotor functions of the rats after laser treatment from the first week following lesioning, compared to the controls. The laser treatment significantly diminished thermal hyperalgesia after SCI as measured by the Plantar test. The atrophy of the soleus muscle was reduced in the laser treated rats. The histopathological investigation showed a positive effect of the laser therapy on white and gray matter sparing. Our data suggests an upregulation of M2 macrophages in laser treated animals by the increasing number of double labeled CD68+/CD206+ cells in the cranial and central parts of the lesion, compared to the control animals. A shift in microglial/macrophage polarization was confirmed by gene expression analysis by significant mRNA downregulation of Cd86 (marker of inflammatory M1), and non-significant upregulation of Arg1 (marker of M2). These results demonstrated that the combination of 808 nm and 905 nm wavelength light is a promising non-invasive therapy for improving functional recovery and tissue sparing after SCI.

Photobiomodulation promotes adenoviral gene transduction in auditory cells

Gene therapy is the delivery of a therapeutic gene into target cells to treat disorders by replacing disease-causing mutated genes with healthy ones. Gene therapy of the inner ear has been recently described, with applications for sensorineural hearing loss. However, gene delivery to the location of the inner ear, and thus efficacy of therapy, is challenging. Photobiomodulation (PBM) with a low-level laser has been suggested to have a therapeutic effect and has the potential to augment gene therapy. To investigate whether PBM improves the rate of adenovirus (Ad)-mediated viral delivery, we compared low-level laser therapy (LLLT) and non-LLLT HEI-OC1 cells treated with an Ad viral vector carrying green fluorescent protein (GFP). Cultured HEI-OC1 cells were divided into six groups: no treatment control, LLLT only, 1 μL Ad-GFP, 3 μL Ad-GFP, 1 μL Ad-GFP + LLLT, and 3 μL Ad-GFP + LLLT (LLLT: 808 nm at 15 mW for 15 min). Cells were irradiated twice: at 2 h and again at 24 h. A nonparametric Mann-Whitney U test was used to statistically analyze differences between the control and treatment groups. The viral inoculations used in this study did not change the amount of viable HEI-OC1 cells (N = 4-8). The 1 μL Ad-GFP + LLLT and 3 μL Ad-GFP + LLLT groups showed an increased density of GFP-positive cells compared to 1 μL and 3 μL Ad-GFP cells (N = 5-8, 1 μL: p = 0.0159; 3 μL: p = 0.0168,). The quantitative analysis of the epifluorescence of the 1 μL Ad-GFP + LLLT, and 3 μL Ad-GFP + LLLT groups revealed increased GFP expression/cell compared to 1 μL and 3 μL Ad-GFP cells (N = 6-15, 1 μL: p = 0.0082; 3 μL: p = 0.0012). The RT-qPCR results were consistent (N = 4-5, p = 0.0159). These findings suggest that PBM may enhance the gene delivery of Ad-mediated viral transduction, and the combination of the two may be a promising tool for gene therapy for sensorineural hearing loss.

Photobiomodulation in Neuroscience: A Summary of Personal Experience

OBJECTIVE

This review summarizes personal experience with laser photobiomodulation and its potentials for the treatment of peripheral and central nerve system injuries.

METHODS AND RESULTS

Laser photobiomodulation was shown to induce nerve cell activation, have a positive effect on metabolism of the nerve cells, and to stimulate nerve sprouting processes. Studies investigating the effects of laser photobiomodulation on injured peripheral nerves in rats reported immediate protective effects which increase the functional activity of the nerve, decrease or prevent scar tissue formation at the injured site, prevent or decrease degeneration in corresponding motor neurons of the spinal cord, and significantly increase axonal growth and myelinization. A direct application of laser on the spinal cord had a positive impact on the corresponding injured peripheral nerve and promoted recovery. A 780-nm laser phototherapy was applied following peripheral nerve reconstruction using a guiding nerve tube. Results showed myelinated axons crossing through the nerve tube and the continuation of axonal sprouting through the tube toward the distal part of the nerve. In a double-blind, placebo-controlled randomized pilot clinical trial in patients with incomplete stable long-term peripheral nerve injury (PNI), 780-nm laser irradiation progressively improved peripheral nerve function and led to substantial functional recovery. Muscle atrophy represents a major challenge in restorative medicine. Laser phototherapy was shown to increase biochemical activity and improve morphological recovery in muscle and, thus, could have a direct therapeutic application, especially during progressive muscle atrophy resulting from PNI. The effectiveness of composite implants of cultured embryonal nerve cells and the role of laser irradiation on regeneration and repair of the completely transected rat spinal cord were examined. Results suggested that laser photobiomodulation treatment accelerates the axonal growth.

CONCLUSIONS

The significance of the performed experimental and clinical studies is in the provision of new laser technology in field of cell therapy and its therapeutic value for peripheral nerve and spinal cord injuries. Additional well-designed clinical studies are needed to evaluate the effectiveness and role of laser photobiomodulation treatment in a clinical setting.