Swimming exercise in the acute or late phase after sciatic nerve crush accelerates nerve regeneration

Brief Electrical Stimulation Promotes Recovery after Surgical Repair of Injured Peripheral Nerves

Injured peripheral nerves regenerate their axons in contrast to those in the central nervous system. Yet, functional recovery after surgical repair is often disappointing. The basis for poor recovery is progressive deterioration with time and distance of the growth capacity of the neurons that lose their contact with targets (chronic axotomy) and the growth support of the chronically denervated Schwann cells (SC) in the distal nerve stumps. Nonetheless, chronically denervated atrophic muscle retains the capacity for reinnervation. Declining electrical activity of motoneurons accompanies the progressive fall in axotomized neuronal and denervated SC expression of regeneration-associated-genes and declining regenerative success. Reduced motoneuronal activity is due to the withdrawal of synaptic contacts from the soma. Exogenous neurotrophic factors that promote nerve regeneration can replace the endogenous factors whose expression declines with time. But the profuse axonal outgrowth they provoke and the difficulties in their delivery hinder their efficacy. Brief (1 h) low-frequency (20 Hz) electrical stimulation (ES) proximal to the injury site promotes the expression of endogenous growth factors and, in turn, dramatically accelerates axon outgrowth and target reinnervation. The latter ES effect has been demonstrated in both rats and humans. A conditioning ES of intact nerve days prior to nerve injury increases axonal outgrowth and regeneration rate. Thereby, this form of ES is amenable for nerve transfer surgeries and end-to-side neurorrhaphies. However, additional surgery for applying the required electrodes may be a hurdle. ES is applicable in all surgeries with excellent outcomes.

The Role of Physical Exercise and Rehabilitative Implications in the Process of Nerve Repair in Peripheral Neuropathies: A Systematic Review

BACKGROUND

The various mechanisms involved in peripheral nerve regeneration, induced by exercise and electrical nerve stimulation, are still unclear.

OBJECTIVE

The aim of this review was to summarize the influence of physical exercise and/or electrical stimulation on peripheral nerve repair and regeneration and the variation of impact of intervention depending on timing, as well as kind and dosage of the intervention. A literature survey was conducted on PubMed, Scopus, and Web of Science, between February 2021 to July 2021, with an update in September 2022.

METHODOLOGY

The literature search identified 101,386 articles with the keywords: "peripheral nerve" OR "neuropathy" AND "sprouting" OR "neuroapraxia" OR "axonotmesis" OR "neurotmesis" OR "muscle denervation" OR "denervated muscle" AND "rehabilitation" OR "physical activity" OR "physical exercise" OR "activity" OR "electrical stimulation". A total of 60 publications were included. Eligible studies were focused on evaluating the process of nerve repair (biopsy, electromyographic parameters or biomarker outcomes) after electrical stimulation or physical exercise interventions on humans or animals with peripheral sensory or motor nerve injury.

SYNTHESIS

This study shows that the literature, especially regarding preclinical research, is mainly in agreement that an early physical program with active exercise and/or electrical stimulation promotes axonal regenerative responses and prevents maladaptive response. This was evaluated by means of changes in electrophysiological recordings of CMAPs for latency amplitude, and the sciatic functional index (SFI). Furthermore, this type of activity can cause an increase in weight and in muscle fiber diameter. Nevertheless, some detrimental effects of exercising and electrical stimulation too early after nerve repair were recorded.

CONCLUSION

In most preclinical studies, peripheral neuropathy function was associated with improvements after physical exercise and electrical stimulation. For humans, too little research has been conducted on this topic to reach a complete conclusion. This research supports the need for future studies to test the validity of a possible rehabilitation treatment in humans in cases of peripheral neuropathy to help nerve sprouting.

Therapeutic exercise interventions in rat models of arthritis

Arthritis is the leading cause of musculoskeletal pain and disability worldwide. Nearly 50% of individuals over the age of 65 have arthritis, which contributes to limited function, articular pain, physical inactivity, and diminished quality of life. Therapeutic exercise is often recommended in clinical settings for patients experiencing arthritic pain, however, there is little practical guidance regarding the use of therapeutic exercise to alleviate arthritic musculoskeletal pain. Rodent models of arthritis allow researchers to control experimental variables, which cannot be done with human participants, providing an opportunity to test therapeutic approaches in preclinical models. This literature review provides a summary of published findings in therapeutic exercise interventions in rat models of arthritis as well as gaps in the existing literature. We reveal that preclinical research in this field has yet to adequately investigate the impact of experimental variables in therapeutic exercise including their modality, intensity, duration, and frequency on joint pathophysiology and pain outcomes.

Resistance exercise promotes functional test via sciatic nerve regeneration, and muscle atrophy improvement through GAP-43 regulation in animal model of traumatic nerve injuries

Resistance training improves muscle strength through a combination of neural plasticity and muscle hypertrophy. This study aimed to evaluate the effects of resistance exercise on sciatic nerve regeneration and histology, growth-associated protein 43 (GAP-43) expressions, and soleus muscle atrophy following traumatic nerve injuries in Wistar rats. In the present study, 40 male Wistar rats were randomly assigned into four groups: healthy control (HC) as a sham group was exposed to the surgical procedures without any sciatic nerve compression, lesioned control (LC), resistance training (RT,non-lesioned), and lesioned rats+RT (LRT) (n=10 in each). The RT group performed a resistance-training program 5 days/week for 4 weeks. Sciatic functional index (SFI) score, beam score and Basso, Beattie, and Bresnahan (BBB) score decreased and the hot plate time increased significantly in the LC‌ group compared to the HC (p<0.05) group. However, the LRT‌ group showed a significant increase in the SFI score (p=0.001) and a significant decrease in hot plate time (p=0.0232) compared to the LC group. The LC group also showed neurological morphological damage and muscle atrophy and a decrease in GAP-43 in nerve tissue. In comparison to the LC group, a significant increase in sciatic nerve caliber, diameter, number of muscle fibers, and the expression of GAP-43‌ (p<0.05) was observed in the LRT group. Doing resistance training even for four weeks seems to affect sciatic nerve lesions and injuries. It can also repair and regenerate nerve tissue by upregulating GAP-43 expression‌, improving motor behavioral tests, and controlling muscle atrophy.

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.

Early Intervention of Cold-Water Swimming on Functional Recovery and Spinal Pain Modulation Following Brachial Plexus Avulsion in Rats

Brachial plexus avulsion (BPA) causes peripheral nerve injury complications with motor and sensory dysfunction of the upper limb. Growing evidence has shown an active role played by cold-water swimming (CWS) in alleviating peripheral neuropathic pain and functional recovery. This study examined whether CWS could promote functional recovery and pain modulation through the reduction of neuroinflammation and microglial overactivation in dorsal horn neurons at the early-stage of BPA. After BPA surgery was performed on rats, they were assigned to CWS or sham training for 5 min twice a day for two weeks. Functional behavioral responses were tested before and after BPA surgery, and each week during training. Results after the two-week training program showed significant improvements in BPA-induced motor and sensory loss (p < 0.05), lower inflammatory cell infiltration, and vacuole formation in injured nerves among the BPA-CWS group. Moreover, BPA significantly increased the expression of SP and IBA1 in dorsal horn neurons (p < 0.05), whereas CWS prevented their overexpression in the BPA-CWS group. The present findings evidenced beneficial rehabilitative effects of CWS on functional recovery and pain modulation at early-stage BPA. The beneficial effects are partially related to inflammatory suppression and spinal modulation. The synergistic role of CWS combined with other management approaches merits further investigation.

The Potential Role of Exercise Training and Mechanical Loading on Bone-Associated Skeletal Nerves

The spatial distribution, innervation, and functional role of the bone-associated skeletal nerves have been previously reported in detail. However, studies examining exercise-induced associations between skeletal nerves and bone metabolism are limited. This review introduces a potential relationship between exercise and the skeletal nerves and discusses how it can contribute to exercise-induced bone anabolism. First, the background and current understanding of nerve fiber types and their functions in the skeleton are provided. Next, the influence of exercise and mechanical loading on the skeletal nervous system is elaborated. Effective synthesis of recent studies could serve as an established baseline for the novel discovery of the effects of exercise on skeletal nerve density and bone anabolic activity in the future. Therefore, this review overviews the existing evidence for the neural control of bone metabolism and the potential positive effects of exercise on the peripheral skeletal nervous system. The influence of exercise training models on the relationships of sensory nerve signals with osteoblast-mediated bone formation and the increased bone volume provides the first insight on the potential importance of exercise training in stimulating positive adaptations in the skeletal nerve-bone interaction and its downstream effect on bone metabolism, thereby highlighting its therapeutic potential in a variety of clinical populations.

The role of exercise on peripheral nerve regeneration: from animal model to clinical application

Peripheral nerve injury is a complex condition with a variety of signs and symptoms depending on the severity and nerves involved. Peripheral nerve damage may lead to sensory and motor functions deficits and even lifelong disability, causing important socioeconomic costs worldwide. Despite the increase in knowledge of the mechanisms of injury and regeneration, a full functional recovery is still unsatisfying in the majority of patients. It is well known that exercise promotes physical and psychological well-being, by ameliorating general health. In the last years, there has been a growing interest in evaluating the effects of exercise on the peripheral nervous system. Experimental works with rodent models showed the potential utility of exercise following peripheral nerve injuries, as evinced by increasing axon regeneration, muscle reinnervation, better recovery of strength, muscle mass and higher expression of neurotrophic factors. Moreover, clinical evidence showed positive trends in favour of physical therapy following peripheral nerve damage based on the improvement of range of motion (ROM), muscle power grade and pain. After a brief overview of peripheral nerve anatomy and the different types of nerve injury, the present review aims to summarize the impact of exercise on peripheral nerve regeneration. Some clinical evidence regarding the effect of exercise after peripheral nerve injury will also be discussed.

Ladder-based resistance training elicited similar ultrastructural adjustments in forelimb and hindlimb peripheral nerves of young adult Wistar rats

To analyze the morphological response induced by high-volume, high-intensity ladder-based resistance training (LRT) on the ultrastructure of the radial (forelimb) and sciatic (hindlimb) nerves of adults Wistar rats. Twenty rats were equally distributed into groups: sedentary (SED) and LRT. After the rodents were subjected to the maximum load (ML) carrying test, the LRT group performed 6-8 progressive climbs (2 × 50% ML, 2 × 75% ML, 2 × 100% ML, and 2 × 100% ML + 30 g) three times per week. After 8 weeks, the radial and sciatic nerves were removed and prepared for transmission electron microscopy. In the radial nerve, myelinated axons cross-sectional area (CSA), unmyelinated axons CSA, myelin sheath thickness, and Schwann cells nuclei area were statistically larger in the LRT group than SED (p < 0.05). Also, the number of microtubules and neurofilaments per field were statistically higher in the LRT group than in SED (p < 0.01). For sciatic nerve, myelinated fibers CSA, unmyelinated axons CSA, myelin sheath thickness, Schwann cells nuclei area, and the number of neurofilaments per field were statistically larger in the LRT group compared to the SED group (p < 0.05). LRT with high-volume and high-intensity effectively induce similar changes in adult Wistar rats' radial and sciatic nerves' ultrastructure.

Whole-body vibration therapy does not improve the peripheral nerve regeneration in experimental model

OBJECTIVES

Whole-body vibration (WBV) is commonly used to improve motor function, balance and functional performance, but its effects on the body are not fully understood. The main objective was to evaluate the morphometric and functional effects of WBV in an experimental nerve regeneration model.

METHODS

Wistar rats were submitted to unilateral sciatic nerve crush and treated with WBV (4-5 weeks), started at 3 or 10 days after injury. Functional performances were weekly assessed by sciatic functional index, horizontal ladder rung walking and narrow beam tests. Nerve histomorphometry analysis was assessed at the end of the protocol.

RESULTS

Injured groups, sedentary and WBV started at 3 days, had similar functional deficits. WBV, regardless of the start time, did not alter the histomorphometry parameters in the regeneration process.

CONCLUSIONS

The earlier therapy did not change the expected and natural recovery after the nerve lesion, but when the WBV starts later it seems to impair function parameter of recovery.

Assessment of the Effects of Swimming as a Postoperative Rehabilitation on Nerve Regeneration of Wistar Rats Submitted to Grafting of Autologous Nerves after Injury to the Sciatic Nerve

Objective  To evaluate the effects of swimming on nerve regeneration after sciatic nerve injury in Wistar rats. Methods  A total of 30 Wistar rats was divided into 3 groups: Sham + Nat group animals that were not submitted to graft surgery and were submitted to swimming ( n  = 10); Graft group: animals submitted to autologous sciatic nerve graft ( n  = 10); and Graft + Nat group: animals submitted to autologous sciatic nerve graft surgery and to swimming ( n  = 10). The results were analyzed on the software (GraphPad Software, San Diego, CA, USA). Results  In the first evaluation, all sciatic functional index (SFI) values were similar ( p  = 0.609). Thirty days after the surgical procedure, we observed differences between all the comparisons: Sham + Nat (-34.64 ± 13.89) versus Graft (-145.9 ± 26.06); Sham + Nat versus Graft + Nat (-89.40 ± 7.501); Graft (-145.9 ± 26.06) versus Graft + Nat (-89.40 ± 7.501). In the measurements (60 and 90 days), there was no statistical difference between the Graft and Graft + Nat groups, with significantly lower values in relation to the control group ( p  < 0.001). The number of motor neurons presented differences in the comparisons between the Sham + Nat and Graft groups (647.1 ± 16.42 versus 563.4 ± 8.07; p  < 0.05), and between the Sham + Nat and Graft + Nat groups (647.1 ± 16.42 versus 558.8 ± 14.79; p  < 0.05). There was no difference between the Graft and Graft + Nat groups. Conclusion  Animals submitted to the swimming protocol after the sciatic nerve grafting procedure did not present differences in the SFI values and motor neuron numbers when compared to the control group. Therefore, this type of protocol is not efficient for the rehabilitation of peripheral nerve lesions that require grafting. Therefore, further studies are needed.

Treadmill exercise activates ATF3 and ERK1/2 downstream molecules to facilitate axonal regrowth after sciatic nerve injury

The purpose of this study was to investigate the effect of treadmill exer-cise on activating transcription factors such as activating transcription factor 3 (ATF3) and extracellular signal-regulated kinase (ERK1/2) sig-naling pathway to facilitate axonal regrowth after sciatic nerve injury (SNI). The experimental rats divided into the normal control (n=10), sedentary groups for 7 (n=10) and 14 days (n=10) post crush, exercise group for 7 (n=10) and 14 days (n=10) post crush (dpc). The rats in ex-ercise groups run on treadmill device at a speed of 8 m/min for 20 min once a day according to exercise duration. In order to evaluate specific regeneration markers and axonal elongation in injured sciatic nerve, we applied immunofluorescence staining and western blot techniques. Treadmill exercise further increased growth-associated protein (GAP-43) expression and axonal regrowth at 7 and 14 dpc than those in sed-entary group. Among mitogen-activated protein kinase downstream molecules, phospho-ERK1/2 (p-ERK1/2) was enhanced by treadmill ex-ercise at only 7 dpc and decreased to basal level 14 days later. But c-Jun N-terminal kinase, c-Jun, and phospho-cyclic adenosine mono-phosphate response element-binding protein showed a tendency to in-crease continuously until 14 dpc by exercise. ATF3 expression in exer-cise group was upregulated at both 7 and 14 dpc compared to the sed-entary group. These results indicate that treadmill exercise had benefi-cial effect on expression of regeneration-related proteins after SNI, suggesting that exercise might be one of various therapeutic strategies for sciatic nerve regeneration.

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.

Modulatory effects of swimming exercise against malathion induced neurotoxicity in male and female rats

Malathion is one of the most commonly used organophosphorus (OP) pesticides. It is important to regard that exposure to OP poisoning may cause anxiety and depression. Malathion toxicity induces cholinergic symptoms. Brain-derived neurotrophic factor (BDNF) is the most profusely expressed neurotrophin in the central nervous system; it promotes the survival of neurons. Regular exercise improves brain well-being and enhances recovery from brain Injuries. It is suggested that BDNF may mediate these effects. Therefore, this study was planned to assess the modulatory effects of regular exercise performance on brain BDNF level, cholinergic activity, oxidative stress and apoptosis in male and female rats subjected to neurotoxicity induced by malathion administration.

MATERIALS AND METHODS

Thirty-two adult male and thirty-two adult female albino rats were included in this study. The rats were divided into four equal groups (8rats). Control group, malathion treated group, exercised group, malathion exercised group. Acetylcholinesterase (AchE) activity, total antioxidant capacity (TAC), BDNF level and Caspase 3 activity were assessed.

RESULTS

Female rats had higher baseline content of BDNF in brain homogenate than male rats. Malathion administration induced a significant decrease in BDNF level in female rats and in the total antioxidant capacity in both male and female rats. A significant elevation in caspase 3 activity was detected in the malathion treated groups, with more elevation in female rats. Swimming exercise improved BDNF level, AchE activity, and apoptosis in both male and female rats in all groups. In addition, male rats were more cholinergic system responders to regular exercise than female rats.

CONCLUSION

It could be concluded that malathion induced elevation in oxidative stress and apoptosis in all rats, with reduction in BDNF level in female rats. Meanwhile, regular swimming exercise was found to improve brain health through modulation of BDNF level and cholinergic activity. It is recommended to practice regular exercise to maintain brain health. Further studies are required to clarify the involvement of sex hormones in BDNF regulation.

Sericin silk protein in peripheral nervous repair associated with the physical exercise of swimming in Wistar rats

OBJECTIVE

To verify the action of sericin associated to swim exercise with overload, on sciatic nerve repair in Wistar rats, after 22 days of nerve compression.

METHODS

Forty animals been composed of five groups: control, injury, injury-sericin, injury-swimming and injury-sericin-swimming. During the lesion procedure, sericin, in hydrolyzed form, applied directly to the injury in the injury-sericin and injury-sericin-swimming groups. Injury-swimming and injury-sericin-swimming groups underwent to 5 days per week for 3 weeks, with a 10% overload of the animal's body weight, and a weekly progressive evolution of swimming time, lasting 15, 20 and 25 min/day. Pre and throughout the treatment period the animals performed evaluation of sciatic functional index and pressure pain threshold with digital von Frey filament. Euthanasia was performed on the 22nd postoperative day, and two fragments of the nerve were collected and prepared for descriptive and quantitative analysis.

RESULTS

The sciatic functional index assessment showed significant differences in the motor function of the control until the 14th day. Regarding the allodynia, there was revealed a significant improvement in injury-swimming performance relative to injury, injury-sericin and injury-sericin-swimming, and the number of viable and non-viable nerve fibers smaller than 4 μm in diameter was significantly higher in the injury-sericin-swimming.

CONCLUSION

swimming showed a better evolution of the nociceptive threshold and allodynia. Sericin treatment had exacerbated pro-inflammatory characteristics. On the other hand, the association of sericine and swimming showed a possible regulatory effect by resting swimming exercise, with a significant increase of fibers of smaller diameter.

The Role of BDNF in Peripheral Nerve Regeneration: Activity-Dependent Treatments and Val66Met

Despite the ability of peripheral nerves to spontaneously regenerate after injury, recovery is generally very poor. The neurotrophins have emerged as an important modulator of axon regeneration, particularly brain derived neurotrophic factor (BDNF). BDNF regulation and signaling, as well as its role in activity-dependent treatments including electrical stimulation, exercise, and optogenetic stimulation are discussed here. The importance of a single nucleotide polymorphism in the BDNF gene, Val66Met, which is present in 30% of the human population and may hinder the efficacy of these treatments in enhancing regeneration after injury is considered. Preliminary data are presented on the effectiveness of one such activity-dependent treatment, electrical stimulation, in enhancing axon regeneration in mice expressing the met allele of the Val66Met polymorphism.

Effect of swimming training on nerve morphological recovery after compressive injury

OBJECTIVE

This study aims to investigate morphological alterations caused by partial sciatic nerve ligation (PNL) and the efficacy of a moderate-intensity swimming training as therapeutic strategy for nerve regeneration.

METHODS

A number of 30 male adult mice were equally divided in control, 14 days after PNL (PNL 14 days), 42 days after PNL (PNL 42 days), 70 days after PNL (PNL 70 days) and 5-week exercise training after 7 days post-lesion (PNL trained 35 days) groups. PNL trained 35 days group began with a 10-min session for 3 days and this time was gradually increased by 10 min every three sessions until the animals had swum for 50 min per session. Morphoquantitative analysis was carried out to assess nerve regeneration in each group.

RESULTS

PNL 14 days group exhibited less degenerating signs than PNL 42 days group, where most post-lesion alterations were visualized. Nerve area and minimum diameter were significantly lower (p < 0.05) than control group. PNL 70 days group showed a greater degree of regenerating fibers and similar morphometric parameters to control group. PNL trained 35 days demonstrated signs of regeneration, reaching control group values in the morphometric analysis.

DISCUSSION

PNL promotes great histopathological changes, which became more visible at 42 post-injury days. A natural nerve-regeneration tendency was observed throughout time, as observed in PNL 70 days group; nevertheless, moderate swimming training was found to be a therapeutic resource for nerve regeneration, accelerating such process from a morphoquantitative perspective.

ABBREVIATIONS

ANOVA: One-way analysis of variance; BDNF: Brain-derived neurotrophic factor; FGF-2: Fibroblast growth factor 2; GDNF: Glial cell line derived neurotrophic factor; IGF: Insulin-link growth factor; IL-1β: Interleukin-1β; NGF: Neural growth factor; PBS: Phosphate-buffered saline; PNL: Partial sciatic nerve ligation.

The Effects of Two Different Exercise Programs on the Ultrastructural Features of the Sciatic Nerve and Soleus Muscle After Sciatic Crush

Peripheral nerve injuries constitute a significant medical problem and the recovery is critically dependent on post-injury treatment. In this study, following sciatic nerve crush, we investigated the effects of a 4-week endurance training program (ET) and balance and coordination training program (BCT) on the ultrastructural features of the sciatic nerve and soleus muscle. The animals were randomly divided into Sham, non-trained (NT), ET, and BCT groups each of which included three animals. Ultra-thin cross and longitudinal sections (70-85 nm) were digitized and analyzed comparatively. The electron micrographic analysis of the sciatic nerve showed similar organelles features in the injury groups (myelin debris and swelling mitochondria). Nonetheless, the ET group presented better ultrastructural features as demonstrated by the greater predominance of rounded fibers and more defined organization in the myelinated axon bundles. In the soleus muscle's analyses, the injured groups demonstrated similar organelles' features (nucleus contained highly heterochromatic nuclei and smaller mitochondria). However, ET and BCT groups showed apparently enlarged myofibril cross-sectional areas and less collagen around muscle fibers, although, the ET group displayed reduced intermyofibrillar spaces and more closely aligned myofilaments when compared with the BCT group. Based on electron micrographic analysis, our findings suggest the presence of ultrastructural differences between the Sham, NT, and the trained groups. Therefore, exercise type seems to be responsible for producing some different positive features in the trained groups, while ET seems to have a more pronounced influence on the ultrastructural features of the sciatic nerve and the soleus muscle after a crush injury. Anat Rec, 300:1654-1661, 2017. © 2017 Wiley Periodicals, Inc.

Effects of swimming exercise on nerve regeneration in a rat sciatic nerve transection model

Background: Swimming is commonly considered to be an efficient rehabilitation exercise to treat peripheral nerve injury. However, the most effective resistance level and exercise duration is still unclear. We investigated the effects and mechanisms of swimming at various exertion levels in a rat sciatic nerve transection model.

Methods: Sciatic nerve transection rats were randomized into the following four groups based on swimming duration (from the 7th day to the 28th day post-surgery): sedentary control group (SC), S10 group (10 min/3 times/week), S20 group (20 min/3 times/week), and S30 group (30 min/3 times/week) (n = 10 each). Axon regeneration, electrophysiological properties, muscular weights, macrophage infiltration, and nerve repair associated maker, calcitonin gene-related peptide (CGRP), were measured.

Results: Dramatic higher successful percentages of nerve regeneration across the 10-mm gaps in swimming groups compared to the SC group. Total area of nerve regeneration significantly improved in the S10 group; however, electrophysiological properties, muscular weights, and macrophage infiltration in the regenerated nerves of rats did not differ significantly between the various exercise groups. CGRP expression was significantly increased in the spinal cord of rats in the S20 group.

Conclusions: Our data indicated that CGRP-related axonal regeneration improved significantly with moderate swimming. These results should inspire new studies in physiotherapeutic practice for related human treatment.

Swimming does not alter nociception threshold in obese rats submitted to median nerve compression

OBJECTIVES

We, herein, analyzed the effect of swimming on nociception threshold and peripheral nerve regeneration in lean and obese rats submitted to median nerve compression.

METHODS

To induce obesity, newborn male Wistar rats received injections of monosodium glutamate (MSG), whereas the control (CTL) group received saline. The animals were separated into 6 groups; control and obese (CTL and MSG), control and obese with lesion (CTL LES and MSG LES), and control and obese with lesion submitted to physical exercise (CTL LES PE and MSG LES PE).

RESULTS

Median nerve compression reduced nociception threshold in CTL LES and MSG LES rats. Swimming effectively altered nociception only in CTL LES PE animals. Lean and obese animals displayed histological differences, when compared to sedentary animals, and exercise improved axon regeneration in both groups. The brain-derived neurotrophic factor and GAP 43 protein expression was greater in animals submitted to nervous compression without alteration by exercise.

DISCUSSION

In conclusion, swimming, a conservative treatment for peripheral nerve lesions, was not able to improve the nociception threshold in obese rats.

Nociceptive and Neuronal Evaluation of the Sciatic Nerve of Wistar Rats Subjected to Compression Injury and Treated with Resistive Exercise

Background. To investigate the climb stairs resistance exercise on nociception and axonal regeneration in the sciatic nerve of rats. Methods. 24 Wistar rats were divided: control group (CG—no injury), exercise group (EG—no injury with physical exercise), lesion group (LG—injury, but without exercise), and treated group (LEG—injury and physical exercise). LG and LEG were subjected to sciatic nerve compression with hemostat. From the 3rd day after injury began treatment with exercise, and after 22 days occurs the removal of a nerve fragment for morphological analysis. Results. Regarding allodynia, CG obtained values less than EG (p = 0.012) and larger than LG and LEG (p < 0.001). Histological results showed that CG and EG had normal appearance, as LG and LEG showed up with large amounts of inflammatory infiltration, degeneration and disruption of nerve fibers, and reduction of the myelin sheath; however LEG presented some regenerated fibers. From the morphometric data there were significant differences, for nerve fiber diameter, comparing CG with LG and LEG and comparing axon diameter and the thickness of the myelin of the CG to others. Conclusion. Climb stairs resistance exercise was not effective to speed up the regenerative process of axons.

Exercise dependent increase in axon regeneration into peripheral nerve grafts by propriospinal but not sensory neurons after spinal cord injury is associated with modulation of regeneration-associated genes

Insufficient regeneration of central nervous system (CNS) axons contributes to persisting neurological dysfunction after spinal cord injury (SCI). Peripheral nerve grafts (PNGs) support regeneration by thousands of injured intraspinal axons and help them bypass some of the extracellular barriers that form after SCI. However this number represents but a small portion of the total number of axons that are injured. Here we tested if rhythmic sensory stimulation during cycling exercise would boost the intrinsic regenerative state of neurons to enhance axon regeneration into PNGs after a lower thoracic (T12) spinal transection of adult rats. Using True Blue retrograde tracing, we show that 4 weeks of cycling improves regeneration into a PNG from lumbar interneurons but not by primary sensory neurons. The majority of neurons that regenerate their axon are within 5 mm of the lesion and their number increased 70% with exercise. Importantly propriospinal neurons in more distant regions (5-20 mm from the lesion) that routinely exhibit very limited regeneration responded to exercise by increasing the number of regenerating neurons by 900%. There was no exercise-associated increase in regeneration from sensory neurons. Analyses using fluorescent in situ hybridization showed that this increase in regenerative response is associated with changes in levels of mRNAs encoding the regeneration associated genes (RAGs) GAP43, β-actin and Neuritin. While propriospinal neurons showed increased mRNA levels in response to SCI alone and then to grafting and exercise, sensory neurons did not respond to SCI, but there was a response to the presence of a PNG. Thus, exercise is a non-invasive approach to modulate gene expression in injured neurons leading to an increase in regeneration. This sets the stage for future studies to test whether exercise will promote axon outgrowth beyond the PNG and reconnection with spinal cord neurons, thereby demonstrating a potential clinical application of this combined therapeutic intervention.

Balance and coordination training, but not endurance training, enhances synaptophysin and neurotrophin-3 immunoreactivity in the lumbar spinal cord after sciatic nerve crush

INTRODUCTION

Numerous rehabilitation treatments have been shown to be useful for peripheral and central restoration after (PNI).

METHODS

After sciatic nerve crush, we investigated 4 weeks of endurance training (ET) and balance and coordination training (BCT) with sciatic function index, hind-paw stride length, and spinal cord dorsal horn synaptophysin and neurotrophin-3 immunoreactivity.

RESULTS

Our results demonstrated no significant differences between the non-trained (NT), ET, and BCT groups in sciatic functional index, and in stride-length analysis, but the ET showed higher values compared with the NT group. Synaptophysin immunoreactivity was higher in the BCT group compared with the NT group, and neurotrophin-3 immunoreactivity in the BCT group was greater compared with the other groups.

CONCLUSION

BCT can positively affect spinal cord plasticity after a (PNI), and these modifications are important in the rehabilitation process.

Exercise, neurotrophins, and axon regeneration in the PNS

Electrical stimulation and exercise are treatments to enhance recovery from peripheral nerve injuries. Brain-derived neurotrophic factor and androgen receptor signaling are requirements for the effectiveness of these treatments. Increased neuronal activity is adequate to promote regeneration in injured nerves, but the dosing of activity and its relationship to neurotrophins and sex steroid hormones is less clear. Translation of these therapies will require principles associated with their cellular mechanisms.

Strategies to promote peripheral nerve regeneration: electrical stimulation and/or exercise

Enhancing the regeneration of axons is often considered to be a therapeutic target for improving functional recovery after peripheral nerve injury. In this review, the evidence for the efficacy of electrical stimulation (ES), daily exercise and their combination in promoting nerve regeneration after peripheral nerve injuries in both animal models and in human patients is explored. The rationale, effectiveness and molecular basis of ES and exercise in accelerating axon outgrowth are reviewed. In comparing the effects of ES and exercise in enhancing axon regeneration, increased neural activity, neurotrophins and androgens are considered to be common requirements. Similarly, there are sex-specific requirements for exercise to enhance axon regeneration in the periphery and for sustaining synaptic inputs onto injured motoneurons. ES promotes nerve regeneration after delayed nerve repair in humans and rats. The effectiveness of exercise is less clear. Although ES, but not exercise, results in a significant misdirection of regenerating motor axons to reinnervate different muscle targets, the loss of neuromuscular specificity encountered has only a very small impact on resulting functional recovery. Both ES and exercise are promising experimental treatments for peripheral nerve injury that seem to be ready to be translated to clinical use.

Effect of low-level laser therapy (LLLT) on peripheral nerve regeneration using fibrin glue derived from snake venom

OBJECTIVES

The purpose of this study was to assess whether the adhesive permits the collateral repair of axons originating from a vagus nerve to the interior of a sural nerve graft, and whether low-level laser therapy (LLLT) assists in the regeneration process.

MATERIALS AND METHODS

Study sample consisted of 32 rats randomly separated into three groups: Control Group (CG; n=8), from which the intact sural nerve was collected; Experimental Group (EG; n=12), in which one of the ends of the sural nerve graft was coapted to the vagus nerve using the fibrin glue; and Experimental Group Laser (EGL; n=12), in which the animals underwent the same procedures as those in EG with the addition of LLLT. Ten weeks after surgery, the animals were euthanized. Morphological analysis by means of optical and electron microscopy, and morphometry of the regenerated fibers were employed to evaluate the results.

RESULTS

Collateral regeneration of axons was observed from the vagus nerve to the interior of the autologous graft in EG and EGL, and in CG all dimensions measured were greater and presented a significant difference in relation to EG and EGL, except for the area and thickness of the myelin sheath, that showed significant difference only in relation to the EG.

CONCLUSIONS

The present study demonstrated that the fibrin glue makes axonal regeneration feasible and is an efficient method to recover injured peripheral nerves, and the use of low-level laser therapy enhances nerve regeneration.

Gallic acid and exercise training improve motor function, nerve conduction velocity but not pain sense reflex after experimental sciatic nerve crush in male rats

OBJECTIVE

The aim of present study was to evaluate the effects of oral administration of gallic acid (GA) for 21 days alone and in combination with exercise on nerve conduction velocity and sensory and motor functions in rats with sciatic nerve crush.

MATERIALS AND METHODS

Seventy adult male Wistar rats (250-300 g) were divided randomly into 7 groups with 10 in each: 1) Control (Cont), 2) Crushed + Vehicle (Cr +Veh), 3-5) Crushed + gallic acid (Cr+GA) (50, 100, and 200 mg/kg/2 mL, orally), 6) Crushed + exercise (Cr+Exe), and 7) Crushed + exercise + effective dose of gallic acid (Cr+Exe +GA200) for 21 days. In order to establish an animal model of sciatic nerve crush, equivalent to 7 kg of force pressed on 2-3 mm of sciatic nerve for 30 s, three times with 30 s intervals. Pain sense reflex in hot plate, motor coordination in rotarod, and sciatic nerve conduction velocity (SNCV) in all groups were tested. Data were analyzed using one-way ANOVA followed by Tukey's post hoc test and p<0.05 has assigned as the significant difference.

RESULTS

Pain threshold was increased significantly in untreated crushed rats while motor function and SNCV were decreased in all groups with nerve crush (p<0.05, p<0.01, p<0.001 vs. control). Pain reflex latency was not changed in treated groups. Motor coordination and SNCV were improved in groups Cr+GA200 and Cr+Exe + GA200 (p<0.05, p<0.01 vs. Cr+Veh).

CONCLUSION

GA, dose-dependently, may have therapeutic potential to improve the peripheral nerve degeneration, which is most likely related, at least in part, to its antioxidant and therapeutic properties.

Balance and coordination training and endurance training after nerve injury

INTRODUCTION

Different rehabilitation treatments have proven useful in accelerating regeneration.

METHODS

After sciatic nerve crush in rats, we tested balance and coordination training (BCT) and endurance training (ET) through sensorimotor tests and analyzed nerve and muscle morphology.

RESULTS

After BCT and ET, rats performed better in sensorimotor tests than did non-trained animals. However, only BCT maintained sensorimotor function during training. Furthermore, BCT and ET produced significantly larger muscle area than in non-trained animals.

CONCLUSIONS

These findings indicate that BCT and ET, when initiated in the early phase after sciatic nerve injury, improve morphological properties of the soleus muscle and sciatic nerve, but only the task-oriented BCT maintained sensorimotor function. The success of rehabilitative strategies appears to be highly task-specific, and strategies that stimulate sensory pathways are the most effective in improving balance and/or coordination parameters.

Effects of pulsed electromagnetic field and swimming exercise on rats with experimental sciatic nerve injury

[Purpose] The current study aimed to reveal the therapeutic effects of a pulsed electromagnetic field and swimming exercises on rats with experimental sciatic nerve injury, which was induced with crush-type neuropathy model damage, using electrophysiological methods. [Subjects] In the current study, the sample consisted of 28 adult male Wistar albino rats. [Methods] The rats were randomized into four groups (n=7). Swimming exercise and PEMF (2 Hz and 0.3 MT) were applied one hour a day, five days a week, for four weeks. Electroneuromyographic (ENMG) measurements were taken on day 7. [Results] When the data were evaluated, it was found that the 4 weeks of PEMF and swimming exercises led to an increase in motor conduction rates and a decrease in latency values, but the changes were not significant in comparison with the control and injury groups. The compound muscle action potential (CMAP) values of the left leg were lower in weeks 2, 3, and 4 in the swimming exercise group in comparison with the control group, although for the PEMF group, the CMAP values of the left leg reached the level observed in the control group beginning in week 3. [Conclusion] PEMF and swimming exercise made positive contributions to nerve regeneration after week 1, and regeneration was enhanced.