Nerve Regeneration Process Research Articles

A biomaterials approach to Schwann cell development in neural tissue engineering.

Schwann cells, in addition to forming myelin sheaths, have pivotal roles in regeneration of injured axons in the peripheral nervous system such as producing a natural permissive conduit between distal and proximal stumps and secreting nerve growth factors. Due to the atrophy and senescence of Schwann cells in long nerve gap, and the need to ensure the presence of nerve growth factors and basal lamina tubes for axon regeneration in a critical time, injection of Schwann cells with the aid of an engineered conduit seems to be an effective approach to induce axon regrowth. Stem cells with high differentiation and proliferation capability can provide an adequate number of Schwann cells in healthy state for regeneration purposes. Guidance of stem cells differentiation into desired lineages, control of implanted Schwann cells fate, maintenance of nerve growth factors expression, and guidance of axon regrowth are possible with the aid of biomaterials with appropriate chemical, physical, and mechanical properties. Biomaterials' surface chemistry and biomolecules interacting with cells' receptors initiate specific intracellular signaling cascades and direct cells fate. In addition, biomaterials' surface topography in association with cells contact area, focal adhesion, and cytoskeletal remodeling by mechanotransduction process influences cells behavior and induces specific differentiation. The main objective of this review is to investigate the chemical, topographical, and mechanical properties of biomaterials which influence the fate of Schwann cells and the nerve regeneration process.

HISTOLOGICAL ANALYSIS OF WISTAR RATS SCIATIC NERVES SUBJECTED TO COMPRESSION AND TREATED WITH LOW LEVEL LASER THERAPY AND NEURAL MOBILIZATION

Background: The physical therapy resources, as Low-Level Laser Therapy (LLLT) and neural mobilization are usually used with regenerative purpose and for the relief of symptoms for peripheral nerve injury. However, there is a lack of consensus on its effects as well as its association. Objective: Evaluate the influence of low-level laser therapy (LLLT) associated with neural mobilization (NM) on nerve regeneration of female Wistar rats subjected to sciatic compression. Methods: Twenty four Wistar rats were divided into: G1 (Placebo), G2 (NM), G3 (LLLT) and G4 (NM+LLLT), all animals were subject to compression of the right sciatic nerve. The treatment occurred on the 3 rd , 5 th , 7 th , 10 th , 12 th and 14 th postoperative day (PO). On the 17th PO the animals were euthanized. Histological and morphometric analysis of the right (compression) and the left (control) sciatic nerve were performed. Results: In the morphometric analysis no significant differences between groups, but differences among sides were found. Histological analysis revealed the presence of inflammatory infiltrate and disruption of nerve fibers in the right sciatic nerves. Conclusion: Both techniques used (LLLT and neural mobilization), isolated and associated, on the parameters proposed, were not effective to accelerate the process of nerve regeneration.

Schwann cell plasticity-roles in tissue homeostasis, regeneration, and disease.

How tissues are maintained over a lifetime and repaired following injury are fundamental questions in biology with a disruption to these processes underlying pathologies such as cancer and degenerative disorders. It is becoming increasingly clear that each tissue has a distinct mechanism to maintain homeostasis and respond to injury utilizing different types of stem/progenitor cell populations depending on the insult and/or with a contribution from more differentiated cells that are able to dedifferentiate to aid tissue regeneration. Peripheral nerves are highly quiescent yet show remarkable regenerative capabilities. Remarkably, there is no evidence for a classical stem cell population, rather all cell-types within the nerve are able to proliferate to produce new nerve tissue. Co-ordinating the regeneration of this tissue are Schwann cells (SCs), the main glial cells of the peripheral nervous system. SCs exist in architecturally stable structures that can persist for the lifetime of an animal, however, they are not postmitotic, in that following injury they are reprogrammed at high efficiency to a progenitor-like state, with these cells acting to orchestrate the nerve regeneration process. During nerve regeneration, SCs show little plasticity, maintaining their identity in the repaired tissue. However, once free of the nerve environment they appear to exhibit increased plasticity with reported roles in the repair of other tissues. In this review, we will discuss the mechanisms underlying the homeostasis and regeneration of peripheral nerves and how reprogrammed progenitor-like SCs have broader roles in the repair of other tissues with implications for pathologies such as cancer.

Increased angiogenesis by the rotational muscle flap is crucial for nerve regeneration.

BackgroundThe gold standard surgical treatment of nerve injury includes direct repair, nerve graft, and neurolysis. The underlying effects (either beneficial or detrimental) of angiogenesis during nerve regeneration by rotational muscle flap have not yet determined. We assess the neurological outcome and angiogenesis of nerve injury following a rotational muscle flap.MethodsWe retrospectively analyzed the outcome of the patients with severe radial nerve injury by neurolysis and rotational muscle flap; we also mimicked the clinical situation by nerve crush followed by rotational muscle flap in animals to assess associated angiogenesis factor expression.ResultsTwenty-three out of 25 (92%) cases of severe radial nerve injury underwent neurolysis assisted by muscle flap rotation and eventually reached their preinjury neurological outcome. In the animal study, both FITC–dextran and Dil infusion showed a remarkably increased vascular structure in the crushed nerve integrated by the muscle flap and abolished by Avastin injection. The rotational muscle flap significantly increased angiogenesis factor expression, and this was attenuated by Avastin injection. The increased angiogenesis factor expression paralleled the improvement seen in neurobehavioral and electrophysiological studies as well as the significant expression of nerve regeneration markers and the restoration of denervated muscle morphology.ConclusionBased on the clinical and animal data analysis, we conclude that muscle flap rotation provides a platform for angiogenesis in the acceleration of nerve regeneration. It appears that the muscle flap rotation augmented the nerve regeneration process which may be beneficial for nerve repair in clinical application.

Recent advances in the use of magnetic nanoparticles to promote neuroregeneration.

Recent advances in the use of magnetic nanoparticles to promote neuroregeneration.

Semaphorin 3A Inhibits Nerve Regeneration During Early Stage after Inferior Alveolar Nerve Transection

Neuroma formation at sites of injury can impair peripheral nerve regeneration. Although the involvement of semaphorin 3A has been suggested in neuroma formation, this detailed process after injury is not fully understood. This study was therefore undertaken to examine the effects of semaphorin 3A on peripheral nerve regeneration during the early stage after injury. Immunohistochemistry for semaphorin 3A and PGP9.5, a general neuronal marker, was carried out for clarify chronological changes in their expressions after transection of the mouse inferior alveolar nerve thorough postoperative days 1 to 7. At postoperative day 1, the proximal stump of the damaged IAN exhibited semaphorin 3A, while the distal stump lacked any immunoreactivity. From this day on, its expression lessened, ultimately disappearing completely in all regions of the transected inferior alveolar nerve. A local administration of an antibody to semaphorin 3A into the nerve transection site at postoperative day 3 inhibited axon sprouting at the injury site. This antibody injection increased the number of trigeminal ganglion neurons labeled with DiI (paired t-test, p < 0.05). Immunoreactivity of the semaphorin 3A receptor, neuropilin-1, was also detected at the proximal stump at postoperative day 1. These results suggest that nerve injury initiates semaphorin 3A production in ganglion neurons, which is then delivered through the nerve fibers to the proximal end, thereby contributes to the inhibition of axonal sprouting from the proximal region of injured nerves in the distal direction. To our knowledge, this is the first report to reveal the involvement of Sema3A in the nerve regeneration process at its early stage.

Simvastatin vs. L-Carnitine: An experimental study on optimizing nerve repair.

Complicity and slow rate of axons regeneration necessitates microsurgery that adjuvant therapy can help it. Improving nerve metabolic capacity and response to neural growth factors are positive effects of simvastatin and L-carnitine. To decrease neuronal loss after axotomy and improve neuronal regeneration, this study was designed to assay effects of these agents on nerve repair. Left sciatic nerve of 70 female rats were cut and repaired under aseptic microsurgery. Based on medications and treatment period, seven groups were formed. no medication. SIM1W: one week daily oral simvastatin. LC1W: one week daily oral L-carnitine. Plb1W: one week daily oral placebo. SIM1M: one month daily oral simvastatin. LC1M: one month daily oral L-carnitine. Plb1M: one month daily oral placebo. Following 90 days, behavioral assessments and then histopathology were done. Mean reflex time of withdrawal reflex latency and toe out angle in all experimented groups increased than normal. Long-term drug-medication significantly improved toe out angle. In long-term drug-medication, inflammation and neural bundle differentiation were significantly lower and higher, respectively. Vascular index showed reduction but number of myelinated nerve fibers had rises in drug-medicated groups compared to control and placebo groups. No obvious differences were detected in myeline diameter. Both Simvastatin and L-carnitine can accelerate and improve the process of nerve regeneration in a long enough treatment period. The regulatory influence of these exogenous neurotrophic drugs may be essential to optimize regeneration of nerve fibers; so can broaden horizons for novel therapeutic modalities to decrease neuronal apoptosis.

In vivo Evaluation of Nanostructured Fibrin-Agarose Hydrogels With Mesenchymal Stem Cells for Peripheral Nerve Repair.

The regenerative capability of peripheral nerves is very limited, and several strategies have been proposed to increase nerve regeneration. In the present work, we have analyzed the in vivo usefulness of a novel nanostructured fibrin-agarose bio-artificial nerve substitute (Nano) used alone or in combination with NeuraGen® collagen type I conduits (Coll-Nano) in laboratory rats with a 10-mm sciatic nerve defect. Control animals were subjected to the gold-standard autograft technique (Auto). Results first demonstrated that the percentage of self-amputations was lower in Nano and Coll-Nano groups as compared to the Auto group. Neurotrophic ulcers were more abundant in the Auto group (60%, with 66.6% of them being >2-mm) than Nano and Coll-Nano groups (0%) at 4 weeks, although Nano showed more ulcers after 12 weeks. Foot length was significantly altered in Auto animals due to neurogenic retraction, but not in Nano and Coll-Nano groups after 12 weeks. At the functional level, all animals showed a partial sensory recovery as determined by the pinch test, especially in Nano and Auto groups, but did not reach the levels of native animals. Toe-spread test revealed a partial motor function recovery only in Nano animals at 4 weeks and Auto and Nano at 12 weeks. Electromyography showed clear denervation signs in all experimental groups, with few differences between Auto and Nano animals. After 12 weeks, an important denervation decrease and an increase of the reinnervation process was found in Auto and Nano groups, with no differences between these groups. Histological analyses demonstrated an active peripheral nerve regeneration process with newly formed peripheral nerve fascicles showing S-100, GAP-43 and myelin in all experimental groups. The peripheral nerve regeneration process was more abundant in Auto group, followed by Nano group, and both were better than Coll-Nano group. Muscle histology confirmed the electromyography results and showed some atrophy and fibrosis signs and an important weight and volume loss in all groups, especially in the Coll-Nano group (56.8% weight and 60.4% volume loss). All these results suggest that the novel Nano substitutes used in in vivo were able to contribute to bridge a 10-mm peripheral nerve defect in rats.

Traumatic neuroma caused the post-amputation neuropathic pain: epidemiology, mechanisms and factors involved in pain generation

Loss of the integrity of the peripheral nerves as a result of the traumatic injury or due to lower limb amputations in case of advanced ischemic disease is leading to serious complications and impaired tissue regeneration. Patients who experiencedamputation procedure do not only suffer from physical limitations and psychological problems, but also from chronic neuropathic pain, referred to as post-amputation pain (PAP), which significant decrease their quality of life. One of the main reason of PAP is post-traumatic neuromas, which are form chaotic structures consisting of regenerative axons and connective tissue, as a results of excessive regeneration of axons. The process of peripheral nerve regeneration starts with Wallerian degeneration and its main role is to degenerate damaged axons in the distal end of the injured nerve and initiate repair processes. In the process of nerves regeneration are involved Schwann cells, which attract immunocompetent cells (mainly macrophages, neutrophils and T lymphocytes) and activate inflammation process, necessary to remove damaged tissues and cells. However, the coordination of the production of pro- and anti-inflammatory cytokines and the activity of neurotrophic factors is of key importance. During regeneration of peripheral nerves, in the microenvironment of the damaged tissues increase the activity of neurotrophic factors including: nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), glial-derived neurotrophic factor (GDNF), and ciliary neurotrophic factor (CNTF) - proteins promoting survival and regeneration of axons. The activity of neurotrophic factors supports axonal regeneration from the proximal part into the distal direction and the final re-innervation of the tissue. In the case of amputation of the limb, the lack of distal stump of the nerve disturb proper regeneration of axons, and excessive activity of neurotrophic factors at the site of injury leads to uncontrolled axonal proliferation and neuroma formation. In addition, the increased activity of NGF enhances the expression of the protein associated with the calcitonin gene related protein (CGRP), which is one of the factors involved in the genesis of neuropathic pain. The protection of the proximal end of the damaged nerve from the regenerative signals coming from the microenvironment of damaged nerve can prevent excessive growth of axons and may inhibit the post-traumatic neuroma formation.

Force induced piezoelectric effect of polyvinylidene fluoride and polyvinylidene fluoride-co-trifluoroethylene nanofibrous scaffolds.

Polyvinylidene fluoride and its co-polymer with trifluoroethylene are promising biomaterials for supporting nerve regeneration processes because of their proven biocompatibility and piezoelectric properties that could stimulate cell ingrowth due to electrical activity upon mechanical deformation. This study reports the piezoelectric effect of electrospun polyvinylidene fluoride scaffolds in response to mechanical loading. An impact test machine was used to evaluate the generation of electrical voltage upon application of an impact load. Scaffolds were produced via electrospinning from polyvinylidene fluoride and polyvinylidene fluoride-co-trifluoroethylene with concentrations of 10-20 wt% dissolved in N,N-dimethylformamide (DMF) and acetone (6:4). The structural and thermal properties of scaffolds were analyzed using Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry, respectively. The piezoelectric response of the scaffolds was induced using a custom-made manual impact press machine. Impact forces between 0.4 and 14 N were applied. Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimetry results demonstrated the piezoelectric effect of the electrospun polyvinylidene fluoride and polyvinylidene fluoride-co-trifluoroethylene scaffolds. All the scaffolds exhibited a piezoelectric polar beta-phase formation. Their thermal enthalpies were higher than the value of the initial materials and exhibited a better tendency of crystallization. The electrospun scaffolds exhibited piezoelectric responses in form of voltage by applying impact load. Polyvinylidene fluoride-co-trifluoroethylene scaffolds showed higher values in the range of 6-30 V as compared to pure polyvinylidene fluoride. Here, the mechanically induced electrical impulses measured were between 2.5 and 8 V. Increasing the impact forces did not increase the piezoelectric effect. The results demonstrate the possibility of producing electrospun polyvinylidene fluoride and polyvinylidene fluoride-co-trifluoroethylene scaffolds as nerve guidance with piezoelectric response. Further experiments must be carried out to analyze the piezoelectricity at dynamic conditions.

Photobiomodulation Therapy (PBMT) in Peripheral Nerve Regeneration: A Systematic Review.

Photobiomodulation therapy (PBMT) has been investigated because of its intimate relationship with tissue recovery processes, such as on peripheral nerve damage. Based on the wide range of benefits that the PBMT has shown and its clinical relevance, the aim of this research was to carry out a systematic review of the last 10 years, ascertaining the influence of the PBMT in the regeneration of injured peripheral nerves. The search was performed in the PubMed/MEDLINE database with the combination of the keywords: low-level laser therapy AND nerve regeneration. Initially, 54 articles were obtained, 26 articles of which were chosen for the study according to the inclusion criteria. In the qualitative aspect, it was observed that PBMT was able to accelerate the process of nerve regeneration, presenting an increase in the number of myelinated fibers and a better lamellar organization of myelin sheath, besides improvement of electrophysiological function, immunoreactivity, high functionality rate, decrease of inflammation, pain, and the facilitation of neural regeneration, release of growth factors, increase of vascular network and collagen. It was concluded that PBMT has beneficial effects on the recovery of nerve lesions, especially when related to a faster regeneration and functional improvement, despite the variety of parameters.

Hepatocyte Growth Factor (HGF) Promotes Peripheral Nerve Regeneration by Activating Repair Schwann Cells

During the peripheral nerve regeneration process, a variety of neurotrophic factors play roles in nerve repair by acting on neuronal or non-neuronal cells. In this report, we investigated the role(s) of hepatocyte growth factor (HGF) and its receptor, c-met, in peripheral nerve regeneration. When mice were subjected to sciatic nerve injury, the HGF protein level was highly increased at the injured and distal sites. The level of both total and phosphorylated c-met was also highly upregulated, but almost exclusively in Schwann cells (SCs) distal from the injury site. When mice were treated with a c-met inhibitor, PHA-665752, myelin thickness and axon regrowth were decreased indicating that re-myelination was hindered. HGF promoted the migration and proliferation of cultured SCs, and also induced the expression of various genes such as GDNF and LIF, presumably by activating ERK pathways. Furthermore, exogenous supply of HGF around the injury site, by intramuscular injection of a plasmid DNA expressing human HGF, enhanced the myelin thickness and axon diameter in injured nerves. Taken together, our results indicate that HGF and c-met play important roles in Schwann cell-mediated nerve repair, and also that HGF gene transfer may provide a useful tool for treating peripheral neuropathy.

Soluble Neuregulin1 Down-Regulates Myelination Genes in Schwann Cells.

Peripheral nerves are characterised by the ability to regenerate after injury. Schwann cell activity is fundamental for all steps of peripheral nerve regeneration: immediately after injury they de-differentiate, remove myelin debris, proliferate and repopulate the injured nerve. Soluble Neuregulin1 (NRG1) is a growth factor that is strongly up-regulated and released by Schwann cells immediately after nerve injury. To identify the genes regulated in Schwann cells by soluble NRG1, we performed deep RNA sequencing to generate a transcriptome database and identify all the genes regulated following 6 h stimulation of primary adult rat Schwann cells with soluble recombinant NRG1. Interestingly, the gene ontology analysis of the transcriptome reveals that NRG1 regulates genes belonging to categories that are regulated in the peripheral nerve immediately after an injury. In particular, NRG1 strongly inhibits the expression of genes involved in myelination and in glial cell differentiation, suggesting that NRG1 might be involved in the de-differentiation (or “trans-differentiation”) process of Schwann cells from a myelinating to a repair phenotype. Moreover, NRG1 inhibits genes involved in the apoptotic process, and up-regulates genes positively regulating the ribosomal RNA processing, thus suggesting that NRG1 might promote cell survival and stimulate new protein expression. This in vitro transcriptome analysis demonstrates that in Schwann cells NRG1 drives the expression of several genes which partially overlap with genes regulated in vivo after peripheral nerve injury, underlying the pivotal role of NRG1 in the first steps of the nerve regeneration process.

Schwann cell durotaxis can be guided by physiologically relevant stiffness gradients

BackgroundSuccessful nerve regeneration depends upon directed migration of morphologically specialized repair state Schwann cells across a nerve defect. Although several groups have studied directed migration of Schwann cells in response to chemical or topographic cues, the current understanding of how the mechanical environment influences migration remains largely understudied and incomplete. Therefore, the focus of this study was to evaluate Schwann cell migration and morphodynamics in the presence of stiffness gradients, which revealed that Schwann cells can follow extracellular gradients of increasing stiffness, in a form of directed migration termed durotaxis.MethodsPolyacrylamide substrates were fabricated to mimic the range of stiffness found in peripheral nerve tissue. We assessed Schwann cell response to substrates that were either mechanically uniform or embedded with a shallow or steep stiffness gradient, respectively corresponding to the mechanical niche present during either the fluid phase or subsequent matrix phase of the peripheral nerve regeneration process. We examined cell migration (velocity and directionality) and morphology (elongation, spread area, nuclear aspect ratio, and cell process dynamics). We also characterized the surface morphology of Schwann cells by scanning electron microscopy.ResultsOn laminin-coated polyacrylamide substrates embedded with either a shallow (∼0.04 kPa/mm) or steep (∼0.95 kPa/mm) stiffness gradient, Schwann cells displayed durotaxis, increasing both their speed and directionality along the gradient materials, fabricated with elastic moduli in the range found in peripheral nerve tissue. Uniquely and unlike cell behavior reported in other cell types, the durotactic response of Schwann cells was not dependent upon the slope of the gradient. When we examined whether durotaxis behavior was accompanied by a pro-regenerative Schwann cell phenotype, we observed altered cell morphology, including increases in spread area and the number, elongation, and branching of the cellular processes, on the steep but not the shallow gradient materials. This phenotype emerged within hours of the cells adhering to the materials and was sustained throughout the 24 hour duration of the experiment. Control experiments also showed that unlike most adherent cells, Schwann cells did not alter their morphology in response to uniform substrates of different stiffnesses.ConclusionThis study is notable in its report of durotaxis of cells in response to a stiffness gradient slope, which is greater than an order of magnitude less than reported elsewhere in the literature, suggesting Schwann cells are highly sensitive detectors of mechanical heterogeneity. Altogether, this work identifies durotaxis as a new migratory modality in Schwann cells, and further shows that the presence of a steep stiffness gradient can support a pro-regenerative cell morphology.

Growing Neural PC-12 Cell on Crosslinked Silica Aerogels Increases Neurite Extension in the Presence of an Electric Field.

Externally applied electrical stimulation (ES) has been shown to enhance the nerve regeneration process and to influence the directionality of neurite outgrowth. In addition, the physical and chemical properties of the substrate used for nerve-cell regeneration is critical in fostering regeneration. Previously, we have shown that polyurea-crosslinked silica aerogels (PCSA) exert a positive influence on the extension of neurites by PC-12 cells, a cell-line model widely used to study neurite extension and electrical excitability. In this work, we have examined how an externally applied electric field (EF) influences the extension of neurites in PC-12 cells grown on two substrates: collagen-coated dishes versus collagen-coated crosslinked silica aerogels. The externally applied direct current (DC) bias was applied in vitro using a custom-designed chamber containing polydimethysiloxane (PDMS) embedded copper electrodes to create an electric field across the substrate for the cultured PC-12 cells. Results suggest orientation preference towards the anode, and, on average, longer neurites in the presence of the applied DC bias than with 0 V DC bias. In addition, neurite length was increased in cells grown on silica-crosslinked aerogel when compared to cells grown on regular petri-dishes. These results further support the notion that PCSA is a promising material for nerve regeneration.

Hydrogel composition and laser micropatterning to regulate sciatic nerve regeneration.

Treatment of peripheral nerve injuries has evolved over the past several decades to include the use of sophisticated new materials endowed with trophic and topographical cues that are essential for in vivo nerve fibre regeneration. In this research, we explored the use of an advanced design strategy for peripheral nerve repair, using biological and semi-synthetic hydrogels that enable controlled environmental stimuli to regenerate neurons and glial cells in a rat sciatic nerve resection model. The provisional nerve growth conduits were composed of either natural fibrin or adducts of synthetic polyethylene glycol and fibrinogen or gelatin. A photo-patterning technique was further applied to these 3D hydrogel biomaterials, in the form of laser-ablated microchannels, to provide contact guidance for unidirectional growth following sciatic nerve injury. We tested the regeneration capacity of subcritical nerve gap injuries in rats treated with photo-patterned materials and compared these with injuries treated with unpatterned hydrogels, either stiff or compliant. Among the factors tested were shear modulus, biological composition, and micropatterning of the materials. The microchannel guidance patterns, combined with appropriately matched degradation and stiffness properties of the material, proved most essential for the uniform tissue propagation during the nerve regeneration process.

Lumbricus rubellus Protein Fraction DLBS1033N Increases Nerve Growth Factor Expression via Tyrosine Kinase Activation

Nerve injury occurred due to mechanical, thermal, chemical, or ischemic factors. Nerve regeneration is needed for recovery. Schwann cell proliferation and differentiation are important factors in the nerve regeneration process. Schwann cells release neurotrophins in the nerve regeneration process. In this study, Lumbricus rubellus protein fraction DLBS1033N was used as therapeutic protein candidate for nerve regeneration treatments. DLBS1033N treatments promoted the growth and survival of Schwann cell in free serum and free serum plus minimum O2 conditions. Real-time PCR and ELISA methods revealed that DLBS1033N induced NGF expressions. The growth and survival of Schwann cells were related to NGF expressions in a specific inhibitor TrkA study. Furthermore, in real-time PCR study, DLBS1033N was able to activate phosphatidylinositol-3-kinase (PI3K) pathway. This study showed that L. rubellus protein fraction DLS1033N can promote the growth and survival of Schwann cells by inducing NGF expressions. Cells growth and survival activities are likely achieved via PI3K pathway.

Biomécanique des nerfs collatéraux digitaux – étude cadavérique

Injuries to digital collateral nerves after hand trauma are frequent and results from surgical treatment are poor. Characterization of mechanical behavior of healthy collateral nerves is necessary to produce numeric models and enhance the comprehension of nerve repair and regeneration process. There is no standard in the literature to characterize healthy nerve mechanics. The mechanical properties of the repaired nerve should be as similar as the healthy nerves, following the principles of mechanobiology. The aim of this study was to characterize the mechanical properties of human digital collateral nerves to look for a correlation with density as an intrinsic property of materials. 4 hands, 18 digital collateral nerves of 5 cm average length, were harvested and preserved by immersion in a NaCl 0.9 % solution to be tested. Each nerve was labelled to identify the corresponding finger during the tensile test. The nerves were positioned in a frame of emery paper, sutured and glued with ethyl-2-cyanoacrylate. Once positioned and aligned in the tensile test machine, Instron ® 3345 the tensile test was performed at speed of 6 mm min. During the test the nerve was continuously rehydrated with a NaCl 0.9 % solution. Density was measured using a Pycnometer and registered for each nerve. The test was recorded by a high-speed camera to identify the failure pattern according to wether the failure occurs in distal, middle and proximal area of the nerve. Finally, the diameter was measured using ImageJ software in a posterior image analysis. The results concern 3 thumbs, 2 index fingers, 6 middle fingers, 3 ring fingers and 4 pinky fingers There is no statistical significant difference between the studied variables among fingers. The failure pattern was distal in 72.22 %, middle 11.11 % and proximal in 16.67 % of the cases in contrast to the results presented by Goldberg et al. [Goldberg SH et al., 2007]. Our study presented a specific modulus characterization of human digital collateral nerves, we do not found other studies to compare our results. A pattern for each finger can be expected, but due to the scanty number of probes patterns do not emerge. We presented the human digital collateral nerve specific modulus constituted of 18 nerves. The failure pattern was distal in 70 % cases. Further studies in nerve composition must be conducted to enhance the knowledge of nerve biomechanical behaviour.

Overlapping Mechanisms of Peripheral Nerve Regeneration and Angiogenesis Following Sciatic Nerve Transection.

Peripheral nervous system owns the ability of self-regeneration, mainly in its regenerative microenvironment including vascular network reconstruction. More recently, more attentions have been given to the close relationship between tissue regeneration and angiogenesis. To explore the overlap of molecular mechanisms and key regulation molecules between peripheral nerve regeneration and angiogenesis post peripheral nerve injury, integrative and bioinformatic analysis was carried out for microarray data of proximal stumps after sciatic nerve transection in SD rats. Nerve regeneration and angiogenesis were activated at 1 day immediately after sciatic nerve transection simultaneously. The more obvious changes of transcription regulators and canonical pathways suggested a phase transition between 1 and 4 days of both nerve regeneration and angiogenesis after sciatic nerve transection. Furthermore, 16 differentially expressed genes participated in significant biological processes of both nerve regeneration and angiogenesis, a few of which were validated by qPCR and immunofluorescent staining. It was demonstrated that STAT3, EPHB3, and Cdc42 co-expressed in Schwann cells and vascular endothelial cells to play a key role in regulation of nerve regeneration and angiogenesis simultaneously response to sciatic nerve transection. We provide a framework for understanding biological processes and precise molecular correlations between peripheral nerve regeneration and angiogenesis after peripheral nerve transection. Our work serves as an experimental basis and a valuable resource to further understand molecular mechanisms that define nerve injury-induced micro-environmental variation for achieving desired peripheral nerve regeneration.

Expression of membrane progesterone receptors (mPRs) in rat peripheral glial cell membranes and their potential role in the modulation of cell migration and protein expression

The role played by progestogens in modulating Schwann cell pathophysiology is well established. Progestogens exert their effects in these cells through both classical genomic and non-genomic mechanisms, the latter mediated by the GABA-A receptor. However, there is evidence that other receptors may be involved. Membrane progesterone receptors (mPRs) are novel 7-transmembrane receptors coupled to G proteins that have been characterized in different tissues and cells, including the central nervous system (CNS). The mPRs were shown to mediate some of progestogens’ neuroprotective effects in the CNS, and to be upregulated in glial cells after traumatic brain injury. Based on this evidence, this paper investigated the possible involvement of mPRs in mediating progestogen actions in S42 Schwann cells. All five mPR isoforms and progesterone receptor membrane component 1 (PGRMC1) were detected in Schwann cells, and were present on the cell membrane. Progesterone and the mPR-specific agonist, Org-OD-02-0 (02) bound to these membranes, indicating the presence of functional mPRs. The mPR agonist 02 rapidly increased cell migration in an in vitro assay, suggesting a putative role of mPRs in the nerve regeneration process. Treatment with pertussis toxin and 8-Br-cAMP blocked 02-induced cell migration, suggesting this progestogen action is mediated by activation of an inhibitory G protein, leading to a decrease in intracellular cAMP levels. In contrast, long-term mPR activation led to increased expression levels of myelin associated glycoprotein (MAG). Taken together, these findings show that mPRs are present and active in Schwann cells and have a role in modulating their physiological processes.