Does pulsed magnetic field therapy influence nerve regeneration in the median nerve model of the rat?

Application of magnetism in tissue regeneration: recent progress and future prospects

Tissue regeneration is a hot topic in the field of biomedical research in this century. Material composition, surface topology, light, ultrasonic, electric field and magnetic fields (MFs) all have important effects on the regeneration process. Among them, MFs can provide nearly non-invasive signal transmission within biological tissues, and magnetic materials can convert MFs into a series of signals related to biological processes, such as mechanical force, magnetic heat, drug release, etc. By adjusting the MFs and magnetic materials, desired cellular or molecular-level responses can be achieved to promote better tissue regeneration. This review summarizes the definition, classification and latest progress of MFs and magnetic materials in tissue engineering. It also explores the differences and potential applications of MFs in different tissue cells, aiming to connect the applications of magnetism in various subfields of tissue engineering and provide new insights for the use of magnetism in tissue regeneration.

Novel Approach of Femur Shortening With Insertion of Expandable Rod to Achieve End-to-End Repair of Sciatic Nerve Laceration

BACKGROUND

Sciatic nerve injuries are challenging for diagnosis and treatment. Particularly in proximally located high-grade injuries, neurorrhaphy often has poor outcomes. Most advocate autologous grafting and some more recently have suggested the value of knee flexion braces to facilitate end-to-end repair.

OBJECTIVE

To describe a case of femur shortening to facilitate tension-free, end-to-end sciatic nerve neurorrhaphy.

METHODS

The patient was a 17-year-old man who was injured by the propeller of a motor boat and suffered a series of lacerations to both lower extremities including transection of his right sciatic nerve in the proximal thigh. After extensive mobilization of the nerve, a greater than 7-cm gap was still present. The patient was treated with femur shortening to facilitate end-to-end coaptation. He subsequently had an expandable rod placed which was lengthened 1 mm per day until his leg length was symmetric.

RESULTS

Within 7 months postoperatively, the patient had an advancing Tinel sign and paresthesias to the dorsum of his foot. Nine months postoperatively, he had early mobility in his plantarflexion.

CONCLUSION

We present a novel method of femur shortening with insertion of an expandable rod to facilitate direct end-to-end and tension-free sciatic nerve neurorrhaphy in a proximally located injury. Furthermore, larger scale and comparative studies are warranted to further explore this and other techniques.

The Grasping Test Revisited: A Systematic Review of Functional Recovery in Rat Models of Median Nerve Injury

The rat median nerve model is a well-established and frequently used model for peripheral nerve injury and repair. The grasping test is the gold-standard to evaluate functional recovery in this model. However, no comprehensive review exists to summarize the course of functional recovery in regard to the lesion type. According to PRISMA-guidelines, research was performed, including the databases PubMed and Web of Science. Groups were: (1) crush injury, (2) transection with end-to-end or with (3) end-to-side coaptation and (4) isogenic or acellular allogenic grafting. Total and respective number, as well as rat strain, type of nerve defect, length of isogenic or acellular allogenic allografts, time at first signs of motor recovery (FSR) and maximal recovery grasping strength (MRGS), were evaluated. In total, 47 articles met the inclusion criteria. Group I showed earliest signs of motor recovery. Slow recovery was observable in group III and in graft length above 25 mm. Isografts recovered faster compared to other grafts. The onset and course of recovery is heavily dependent from the type of nerve injury. The grasping test should be used complementary in addition to other volitional and non-volitional tests. Repetitive examinations should be planned carefully to optimize assessment of valid and reliable data.

Effects of sub-acute co-exposure to WIFI (2.45 GHz) and Pistacia lentiscus oil treatment on wound healing by primary intention in male rabbits

Background

The bioeffects of WIFI on cutaneous wound healing remains unexplored. In addition, several medicinal plant products including lentisk oil have been shown to interfere with wound healing process. Since the use of this oil is increasing, the co‐exposure (WIFI‐Lentisk oil) assessment is of paramount importance.

Objectives

We aimed in the present study to investigate the effects of WIFI exposure as well as the application of Pistacia lentiscus oil on sutured wounds (SW).

Methods

New Zealand male rabbits (n = 24) were used and randomly divided into four groups of six animals each: a control group (SW) and three experimental groups (i) a first group exposed to WIFI (2.45 GHz, 6 h/day) during 16 days (SWW); (ii) a second group exposed to WIFI (2.45 GHz, 6 h/day) during 16 days and treated with lentisk oil (SWWL) and (iii) a third group not exposed to WIFI but treated with lentisk oil (SWL). The wound healing was evaluated by monitoring clinical parameters (temperature, food intake, relative weight variation, and macroscopic aspect) and histology.

Results

The mean food intake was higher in the SWWL group compared to the three other groups (p < 0.001) and higher in the SWL group compared to the SW group (p = 0.014). The exposition to WIFI (SWW group) or lentisk oil application (SWL group) can promote the collagen deposition and ameliorate the general aspect of wounds. By contrast, the co‐exposure to WIFI and lentisk oil (SWWL) results in antagonist effects and extends the inflammatory phase of wound healing.

Conclusions

Wounds treated topically with Pistacia lentiscus oil should not be exposed to WIFI.

The effects of pulsed electromagnetic field on experimentally induced sciatic nerve injury in rats

Some experimental research indicates that low-frequency pulsed electromagnetic field (PEMF) stimulation may accelerate regeneration in sciatic nerve injury. However, little research has examined the electrophysiological and functional properties of regenerating peripheral nerves under PEMF. The main aim of the present study is to investigate the effects of PEMF on sciatic nerve regeneration in short- and long-term processes with electrophysiologically and functionally after crushing damage. Crush lesions were performed using jewelery forceps for 30 s. After crush injury of the sciatic nerves, 24 female Wistar-Albino rats were divided into 3 groups with 8 rats in each group: SH(Sham), SNI (Sciatic Nerve Injury), SNI+PEMF(Sciatic Nerve Injury+Pulsed Electromagnetic Field). SNI+PEMF group was exposed to PEMF (4 h/day, intensity; 0.3mT, low-frequency; 2 Hz) for 40-days. Electrophysiological records (at the beginning and 1st, 2nd, 4th and 6th weeks post-crush) and functional footprints (at 1st, 2nd, 3rd, 4th, 5th and 6th weeks post crush) were measured from all groups during the experiment. The results were compared to SNI and SNI+PEMF groups, it was found that amplitude and area parameters in the first-week were significantly higher and latency was lower in the SNI+PEMF group than in the SNI group (p < 0,05). However, the effect of PEMF was not significant in the 2nd, 4th, 6th weeks. In addition, in the 1st and 2nd weeks, the SSI parameters were significantly higher in SNI+PMF group than SNI group (p < .05). These results indicate that low-frequency PEMF is not effective for long-periods of application time while PEMF may be useful during the short-term recovery period.

The Median Nerve Injury Model in Pre-clinical Research - A Critical Review on Benefits and Limitations

The successful introduction of innovative treatment strategies into clinical practise strongly depends on the availability of effective experimental models and their reliable pre-clinical assessment. Considering pre-clinical research for peripheral nerve repair and reconstruction, the far most used nerve regeneration model in the last decades is the sciatic nerve injury and repair model. More recently, the use of the median nerve injury and repair model has gained increasing attention due to some significant advantages it provides compared to sciatic nerve injury. Outstanding advantages are the availability of reliable behavioural tests for assessing posttraumatic voluntary motor recovery and a much lower impact on the animal wellbeing. In this article, the potential application of the median nerve injury and repair model in pre-clinical research is reviewed. In addition, we provide a synthetic overview of a variety of methods that can be applied in this model for nerve regeneration assessment. This article is aimed at helping researchers in adequately adopting this in vivo model for pre-clinical evaluation of peripheral nerve reconstruction as well as for interpreting the results in a translational perspective.

Sensory neurotization of muscle: past, present and future considerations

Research has shown that temporary innervation by a sensory neuron can provide trophic support to a denervated muscle and stave off muscular atrophy until motor neuron transfer is viable. This so called 'sensory protection' allows for improved outcomes when motor reinnervation able to occur. The theoretical benefit of sensory neurotization is hypothesized to maintain tissue architecture of the end organ due to tropic effects of stimulation. While the literature supports direct motor neurotization from 2 to 4 months post-injury, patient factors including the location of the injury and loss of nerve can preclude this therapeutic window. When direct neurotization is not possible, or there is a long distance to traverse for reinnervation, sensory neurotization may be beneficial. The theorized trophic stimulation enabling end organ architectural maintenance provided by sensory neurotization has been shown to allow for delayed direct motor neurotization without the irreversible sequelae of prolonged denervation. This is a review of the pathogenesis of nerve injury and a literature review of sensory neurotization. An analytical search of the literature in PubMed was performed in order to find articles pertinent to the topic of sensory neurotization, including experimental data from both animal models and case reports in humans.

A morphological and biochemical evaluation of the effects of quercetin on experimental sciatic nerve damage in rats

The present study evaluated the neuroprotective and antioxidant effects of quercetin in a rat model of sciatic nerve crush injury using histopathological, morphometric and biochemical methods. A total of 48 male Sprague Dawley rats, aged 10-12 weeks old were randomly divided into eight groups, consisting of two sham groups (S-7, S-28), three quercetin-treated groups (Q-7, Q-28; 200 mg/kg/7 days), trauma (T-7, T-28; 1 min sciatic nerve crush injury) and three trauma+quercetin groups (T+Q-7, T+Q-28; trauma+quercetin 200 mg/kg/7 days). Rats were sacrificed on day 7 or 28. Oxidant-antioxidant biochemical parameters in nerve tissues from all groups were analyzed using histopathological staining with toluidine blue and Masson's trichrome. DNA fragmentations were identified using terminal deoxynucleotidyl transferase deoxyuridine triphosphate nick-end labeling in cells from each tissue sample. Degeneration of the axons and myelin sheath, the breakdown of the concentric lamellar structure of the myelin sheath and axonal swelling were observed in groups T-7 and T-28. Myelin sheath thicknesses, nerve fiber diameters and the number of myelinated nerve fibers decreased, while the apoptotic index (AI) increased in the T-7 and T-28 groups. However, it was observed that nerve regeneration began in the T+Q-7 and T+Q-28 groups compared with the sham groups, together with the healing of cellular damage and axonal structure and a decrease in the AI. Malondialdehyde and superoxide dismutase activity did not differ significantly between the T-7 and S-7 groups. However, catalase activity significantly decreased in the T-28 group when compared with the sham 7 day group. Tissue malondialdehyde levels significantly increased, while serum catalase activity increased in the T+Q-7 group compared with the T-7 group. These results suggest that quercetin has beneficial effects on nerve regeneration and may shorten the healing period in crush-type sciatic nerve injuries.

Controversies related to electromagnetic field exposure on peripheral nerves

Electromagnetic field (EMF) is a pervasive environmental presence in modern society. In recent years, mobile phone usage has increased rapidly throughout the world. As mobile phones are generally held close to the head while talking, studies have mostly focused on the central and peripheral nervous system. There is a need for further research to ascertain the real effect of EMF exposure on the nervous system. Several studies have clearly demonstrated that EMF emitted by cell phones could affect the systems of the body as well as functions. However, the adverse effects of EMF emitted by mobile phones on the peripheral nerves are still controversial. Therefore, this review summarizes current knowledge on the possible positive or negative effects of electromagnetic field on peripheral nerves.

Injured Nerve Regeneration using Cell-Based Therapies: Current Challenges

This paper reviews the recent research progress in the past several years on promoting peripheral nerve recovery using stem and progenitory cells. The emphasis is placed on studies aimed at assessing various stem cells capable of expressing neurotrophic and growth factors and surviving after implantation in the nerve or a conduit. Approaches to improving nerve conduit design are summarized. The contribution of stem cells to axonal regeneration and neural repair is discussed. The side effects associated with cell-based treatment are highlighted. From the studies reviewed, it is concluded that the fate of transplanted stem cells needs further elucidation in a microenvironment-dependent manner.