Myelinated Fibers Research Articles

Voluntary wheel running prevents formation of membrane attack complexes and myelin degradation after peripheral nerve injury

Regular aerobic activity is associated with a reduced risk of chronic pain in humans and rodents. Our previous studies in rodents have shown that prior voluntary wheel running can normalize redox signaling at the site of peripheral nerve injury, attenuating subsequent neuropathic pain. However, the full extent of neuroprotection offered by voluntary wheel running after peripheral nerve injury is unknown. Here, we show that six weeks of voluntary wheel running prior to chronic constriction injury (CCI) reduced the terminal complement membrane attack complex (MAC) at the sciatic nerve injury site. This was associated with increased expression of the MAC inhibitor CD59. The levels of upstream complement components (C3) and their inhibitors (CD55, CR1 and CFH) were altered by CCI, but not increased by voluntary wheel running. Since MAC can degrade myelin, which in turn contributes to neuropathic pain, we evaluated myelin integrity at the sciatic nerve injury site. We found that the loss of myelinated fibers and decreased myelin protein which occurs in sedentary rats following CCI was not observed in rats with prior running. Substitution of prior voluntary wheel running with exogenous CD59 also attenuated mechanical allodynia and reduced MAC deposition at the nerve injury site, pointing to CD59 as a critical effector of the neuroprotective and antinociceptive actions of prior voluntary wheel running. This study links attenuation of neuropathic pain by prior voluntary wheel running with inhibition of MAC and preservation of myelin integrity at the sciatic nerve injury site.

Retro is the new modern: Contemporary application of gold impregnation staining on brain cryosections for digital image analysis

Background and purpose: Since the times of Golgi and Cajal, impregnation with gold or silver has been used to visualize microscopic details of the nervous tissue. Although immunohistochemistry has largely replaced impregnation techniques, they are still used, and there is a growing interest in combining them with modern image analysis methods for quantitative studies in neuroscience. The aim of this research was to modify the gold chloride impregnation method published by Schmued to improve consistency of staining, to be adequate for digital image analysis. Materials and methods: Brains of 8 six-month-old female Wistar rats were fixed in 4% PFA, cryoprotected in sucrose and flash‑frozen in liquid nitrogen. Neighboring sets of coronal sections were chosen for gold impregnation, Nissl staining and MAP2 immunohistochemistry. Whole-slide images and images of specific regions were taken for analysis. Results: Myelinated fibers were stained dark reddish to brown on goldstained sections, and other tissue was yellowish, which gave an excellent contrast for digital image analysis. Gold staining was consistent in all regions, and no major artifacts were noticed. When compared to Nissl and MAP2, only myelinated structures were stained with gold impregnation. Conclusions: Modified gold impregnation method is an alternative that’s on par with traditional myelin staining methods. The new, modified gold impregnation method gives a consistent and reproducible staining suitable for digital image analysis. It can be useful in morphometric evaluation of nervous tissue and investigation of neuropathological changes in nervous tissue, especially for quantitative studies.

ASK1-K716R reduces neuroinflammation and white matter injury via preserving blood–brain barrier integrity after traumatic brain injury

BackgroundTraumatic brain injury (TBI) is a significant worldwide public health concern that necessitates attention. Apoptosis signal-regulating kinase 1 (ASK1), a key player in various central nervous system (CNS) diseases, has garnered interest for its potential neuroprotective effects against ischemic stroke and epilepsy when deleted. Nonetheless, the specific impact of ASK1 on TBI and its underlying mechanisms remain elusive. Notably, mutation of ATP-binding sites, such as lysine residues, can lead to catalytic inactivation of ASK1. To address these knowledge gaps, we generated transgenic mice harboring a site-specific mutant ASK1 Map3k5-e (K716R), enabling us to assess its effects and elucidate potential underlying mechanisms following TBI.MethodsWe employed the CRIPR/Cas9 system to generate a transgenic mouse model carrying the ASK1-K716R mutation, aming to investigate the functional implications of this specific mutant. The controlled cortical impact method was utilized to induce TBI. Expression and distribution of ASK1 were detected through Western blotting and immunofluorescence staining, respectively. The ASK1 kinase activity after TBI was detected by a specific ASK1 kinase activity kit. Cerebral microvessels were isolated by gradient centrifugation using dextran. Immunofluorescence staining was performed to evaluate blood–brain barrier (BBB) damage. BBB ultrastructure was visualized using transmission electron microscopy, while the expression levels of endothelial tight junction proteins and ASK1 signaling pathway proteins was detected by Western blotting. To investigate TBI-induced neuroinflammation, we conducted immunofluorescence staining, quantitative real-time polymerase chain reaction (qRT-PCR) and flow cytometry analyses. Additionally, immunofluorescence staining and electrophysiological compound action potentials were conducted to evaluate gray and white matter injury. Finally, sensorimotor function and cognitive function were assessed by a battery of behavioral tests.ResultsThe activity of ASK1-K716R was significantly decreased following TBI. Western blotting confirmed that ASK1-K716R effectively inhibited the phosphorylation of ASK1, JNKs, and p38 in response to TBI. Additionally, ASK1-K716R demonstrated a protective function in maintaining BBB integrity by suppressing ASK1/JNKs activity in endothelial cells, thereby reducing the degradation of tight junction proteins following TBI. Besides, ASK1-K716R effectively suppressed the infiltration of peripheral immune cells into the brain parenchyma, decreased the number of proinflammatory-like microglia/macrophages, increased the number of anti-inflammatory-like microglia/macrophages, and downregulated expression of several proinflammatory factors. Furthermore, ASK1-K716R attenuated white matter injury and improved the nerve conduction function of both myelinated and unmyelinated fibers after TBI. Finally, our findings demonstrated that ASK1-K716R exhibited favorable long-term functional and histological outcomes in the aftermath of TBI.ConclusionASK1-K716R preserves BBB integrity by inhibiting ASK1/JNKs pathway in endothelial cells, consequently reducing the degradation of tight junction proteins. Additionally, it alleviates early neuroinflammation by inhibiting the infiltration of peripheral immune cells into the brain parenchyma and modulating the polarization of microglia/macrophages. These beneficial effects of ASK1-K716R subsequently result in a reduction in white matter injury and promote the long-term recovery of neurological function following TBI.

A multifaceted architectural framework of the mouse claustrum complex.

Accurate anatomical characterizations are necessary to investigate neural circuitry on a fine scale, but for the rodent claustrum complex (CLCX), this has yet to be fully accomplished. The CLCX is generally considered to comprise two major subdivisions, the claustrum (CL) and the dorsal endopiriform nucleus (DEn), but regional boundaries to these areas are debated. To address this, we conducted a multifaceted analysis of fiber- and cytoarchitecture, genetic marker expression, and connectivity using mice of both sexes, to create a comprehensive guide for identifying and delineating borders to CLCX, including an online reference atlas. Our data indicated four distinct subregions within CLCX, subdividing both CL and DEn into two. Additionally, we conducted brain-wide tracing of inputs to CLCX using a transgenic mouse line. Immunohistochemical staining against myelin basic protein (MBP), parvalbumin (PV), and calbindin (CB) revealed intricate fiber-architectural patterns enabling precise delineations of CLCX and its subregions. Myelinated fibers were abundant dorsally in CL but absent ventrally, whereas PV expressing fibers occupied the entire CL. CB staining revealed a central gap within CL, also visible anterior to the striatum. The Nr2f2, Npsr1, and Cplx3 genes expressed specifically within different subregions of the CLCX, and Rprm helped delineate the CL-insular border. Furthermore, cells in CL projecting to the retrosplenial cortex were located within the myelin sparse area. By combining own experimental data with digitally available datasets of gene expression and input connectivity, we could demonstrate that the proposed delineation scheme allows anchoring of datasets from different origins to a common reference framework.

Peripheral nerve traction injury. Literature review

Traction injury of the peripheral nerve (TIPN) is an injury that occurs as a result of stretching the nerve beyond its normal elastic properties. An analysis of the available literature has revealed the following. TIPN is the most common type of severe nerve injury in the setting of road traffic accidents, catatrauma, gunshot wounds, birth injuries, etc. The dynamics of TIPN during fast and slow stretching is the same and includes three phases: elastic, inelastic and tearing. The limits of elastic stretching of the nerve are determined by the degree of tortuosity of myelinated fibers and the elasticity of the connective tissue framework of the nerve. Stretching of the nerve beyond its elastic limits is characterized by rupture of axons and endoneurial sheaths, including at a considerable distance from the epicenter of pathomorphological changes, which determines the severity of the injury and the impossibility of effective nerve autoregeneration. The force of stretching and the direction of its application to the nerve trunk determine the severity of TIPN. The degree of nerve stretching varies along its length and reaches a maximum in the periarticular areas. A fairly moderate stretching of the nerve can lead to a noticeable change in the conductivity of electrical impulses. Unlike other localized types of nerve injury, the pattern of pathomorphological changes in TIPN includes various forms of damage to structural elements. Understanding the pathophysiology of TIPN is a prerequisite for the development of optimal treatment of this type of injury.

Microstructural Neurodegeneration of the Entorhinal-Hippocampus Pathway along the Alzheimer's Disease Continuum.

Conventional neuroimaging biomarkers for the neurodegeneration of Alzheimer's disease (AD) are not sensitive enough to detect neurodegenerative alterations during the preclinical stage of AD individuals. We examined whether neurodegeneration of the entorhinal-hippocampal pathway could be detected along the AD continuum using ultra-high-field diffusion tensor imaging and tractography for ex vivo brain tissues. Postmortem brain specimens from a cognitively unimpaired individual without AD pathological changes (non-AD), a cognitively unimpaired individual with AD pathological changes (preclinical AD), and a demented individual with AD pathological changes (AD dementia) were scanned with an 11.7T diffusion magnetic resonance imaging. Fractional anisotropy (FA) values of the entorhinal layer II and number of perforant path fibers counted by tractography were compared among the AD continuum. Following the imaging analyses, the status of myelinated fibers and neuronal cells were verified by subsequent serial histological examinations. At 250μm (zipped to 125μm) isotropic resolution, the entorhinal layer II islands and the perforant path fibers could be identified in non-AD and preclinical AD, but not in AD dementia, followed by histological verification. The FA value of the entorhinal layer II was the highest among the entorhinal laminae in non-AD and preclinical AD, whereas the FA values in the entorhinal laminae were homogeneously low in AD dementia. The FA values and number of perforant path fibers decreased along the AD continuum (non-AD>preclinical AD > AD dementia). We successfully detected neurodegenerative alterations of the entorhinal-hippocampal pathway at the preclinical stage of the AD continuum.

The potential protective effects of melatonin and omega-3 on the male rat optic nerve exposed to 900 MHz electromagnetic radiation during the prenatal period

Background Due to children and adolescents’ widespread use of electronic devices, researchers have focused on pre-and early postnatal electromagnetic field (EMF) exposure. However, little is known about the effects of EMF exposure on the optic nerve. The aim of study was to investigate the changes occurring in the optic nerve and the protective effects of melatonin (mel) and omega 3 (ω-3) in rats. Methods Thirty-five pregnant rats were divided into seven groups, Cont, Sham, EMF, EMF + melatonin (EMF + Mel), EMF + ω3, Mel, and ω3. The EMF groups were exposed to 900 megahertz (MHz) EMF daily for two hours during pregnancy. After the experiment, the right optic nerve of each offspring rat was removed and fixed in glutaraldehyde. Thin and semi-thin sections were taken for electron microscopic and stereological analyses. Myelinated axon numbers, myelin sheath thicknesses, and axonal areas were estimated using stereological methods. Results The groups had no significant differences regarding mean numbers of axons, mean axonal areas, or mean myelin sheath thicknesses (p > 0.05). Histological observations revealed impaired lamellae in the myelin sheath of most axons, and vacuolization was frequently observed between the myelin sheath and axon in the EMF-exposed group. The Mel and ω-3-treated EMF groups exhibited well-preserved myelinated nerve fibers and intact astrocytes and oligodendrocytes. Conclusions At the ultrastructural level, Mel and ω3 exhibits a neuroprotective effect on the optic nerve exposed to prenatal EMF. The protective effects of these antioxidants on oligodendrocytes, which play an essential role in myelin formation in the central nervous system, now require detailed investigation.

Long-term invasive electrical stimulation of peripheral nerve in the functional recovery of neuromuscular complex in experiment

Background. Limb damage dominates in the structure of combat trauma, making up to 75 % in modern wars and the number of wounded with peripheral nerve injuries of the limbs can be up to 25 %. The degree of disability of patients is 65–70 %, which makes the problem of restoring peripheral nerves extremely actual. The purpose of the study was to determine the effect of long-term invasive electrical stimulation on the functional restoration of the neuromuscular complex in experiment. Materials and methods. The study was performed on 29 white outbred rabbits (2500 ± 250 g, 5–6 months) according to all norms of bio­ethics. Animals were divided into the following experimental groups: group 1 (n = 8, controls) — epineural suture of the sciatic nerve and implantation of a non-working antenna of the electrical stimulation device; group 2 (n = 7): similar operation of epineural suture of the sciatic nerve with implantation of the electric stimulator antenna and stimulation on beginning at the 2nd day after the operation; group 3 (n = 7): a similar operation of the sciatic nerve epineural suture with implantation of an electric stimulator antenna and the start of stimulation after 2 weeks, when the initial signs of nerve regeneration were observed; group 4 (n = 7): autografting of the sciatic nerve and implantation of an electrical stimulator and the beginning of stimulation at a time point that will coincide with the signs of nerve regeneration. Results. Therefore, in group 2, where electrical stimulation was started the day after the operation, the indicators of functional recovery of the neuromuscular complex were better than in its absence, as well as under the conditions of starting the stimulation in the period when the initial signs of regeneration were observed. Therefore, it can be assumed that the invasive electrical stimulation of the peripheral nerve, started in the acute period after the injury, has a positive effect on the regeneration of the peripheral nerves, as well as on the results of the functional restoration of the neuromuscular complex. The positive effect of electrical stimulation on the functional state of muscles is indirectly evidenced by the larger amplitude of the compound muscle action potential (CMAP) in the group where the stimulation was started faster. A larger amplitude of the CMAP during the observation indicates a greater number of axons that reached the muscle during 8 weeks. Given that the growth cone of the regenerating nerve contains a certain number of axons that first grow to the effector organ, in this case the muscle, with a relatively unchanged action potential latency, it can be assumed that direct electrical stimulation of the peripheral nerve leads to an increase speed of axons sprouting, with their relatively unchanged number. The absence of a significant difference in the action potential latency in the groups where autografting and suture were performed under the same conditions of stimulation indicates a positive effect of stimulation on the myelination of nerve fibers. A better CMAP indirectly indicates a satisfactory functional state of the muscle, which in conditions of denervation allows to preserve its potential for recovery and prevent atrophy. Conclusions. Summarizing all of the above, according to the data of electrophysiological research, we can indirectly conclude that: 1) the impact of invasive electrical stimulation on the regeneration of the neuromuscular complex is positive, and is accompanied by a better effect if it is performed early after the injury; 2) invasive electrical stimulation of the peripheral nerve is a procedure that allows to accelerate the growth of nerve fibers, improve their myelination and prevent the loss of functional capacity of the denervated muscle.

Modeling the excitation of nerve axons under transcutaneous stimulation

Computational models enable a safe and convenient way to study the excitation of nerve fibers under external stimulation. Contemporary models calculate the electric field distribution from transcutaneous stimulation and the resulting neuronal response separately. This study uses finite element methods to develop a multi-scale model that couples electric fields within macroscopic tissue layers and microscopic nerve fibers in a single-stage computational framework. The model included a triaxial myelinated nerve fiber bundle embedded within a volume conductor of tissue layers to represent the median nerve innervating the forearm muscles. The model captured the excitability of nerve fibers under transcutaneous stimulation and their nerve-tissue interactions to a transient external stimulus. The determinants of the strength-duration curve, rheobase, and chronaxie for the proposed model had close correlations with in-vivo experimentation on human participants. Additionally, the excitability indices for the triaxial myelinated nerve fiber implemented using the finite element method agreed well with experimental data from the literature. The validity of the proposed model encourages its use for applications involving transcutaneous stimulation. Capable of capturing field distribution across realistic morphologies, the model can serve as a testbed to improve stimulation protocols and electrode designs with subject-level specificity.

The mTOR pathway and transgenic animals with deletion of the TSC gene in the regeneration of the nervous system and selected models of sciatic nerve damage

Traumatic damage to the nervous system has been a common occurrence for years, reducing patients' quality of life. The mammalian target of rapamycin (mTOR) pathway plays a key role in nervous system physiology, including by controlling nerve cell survival and differentiation. Excessive activation of the mTOR pathway leads to an increase in cell cycle protein activity and apoptosis of nerve cells. Moreover, current findings suggest the involvement of the mTOR pathway in neuroplasticity. The use of transgenic animals with deletion of the TSC gene as well as various models of sciatic nerve damage, allows activation of the mTOR pathway. Currently, the results confirm that inactivation of point mutations in TSC-1 or TSC-2 genes, activates the canonical signaling pathway of the mTORC-1 complex, in turn, reactivation of the mTORC-1 pathway through the absence of the TSC-1 gene in mature neurons induces axonal regeneration. Dysfunction of the mTORC-1 pathway in Schwann cells (SC) inhibits myelination of nerve fibers. The aim of the present study is to understand the physiology and role of the mTOR pathway as well as to demonstrate the impact of TSC gene deletion in the regeneration of the nervous system. Current research on the activity of the mTOR pathway may provide new strategies to intensify peripheral nerve regeneration.

Myelinated Retinal Nerve Fiber Layer in Idiopathic Intracranial Hypertension: A Rare and Challenging Scenario.

Myelinated Retinal Nerve Fiber Layer in Idiopathic Intracranial Hypertension: A Rare and Challenging Scenario.

2,4-Dinitrophenol does not exert neuro-regenerative potential in experimental autoimmune neuritis

ObjectiveWe evaluated the potential neuro-regenerative effects of the mitochondrial uncoupler 2,4-Dinitrophenol in experimental autoimmune neuritis, an animal model for an acute autoimmune neuropathy. MethodsExperimental autoimmune neuritis was induced in Lewis rats. Different concentrations of 2,4-Dinitrophenol (1 mg/kg, 0.1 mg/kg and 0.01 mg/kg) were applied during the recovery phase of the neuritis (at days 18, 22 and 26) and compared to the vehicle. Any effects were assessed through functional, electrophysiological, and morphological analysis via electron microscopy of all groups at day 30. Additional immune-histochemical analysis of inflammation markers and remyelination of the sciatic nerves were performed for the dosage of 1 mg/kg and control. ResultsNo enhancement of functional or electrophysiological recovery was observed in all 2,4-Dinitrophenol-treated groups. Cellular inflammation markers of T cells (CD3+) were comparable to control, and an increase of macrophages (IbA1+) invasion in the sciatic nerves was observed. Treatment with 2,4-Dinitrophenol reduced axonal swelling in myelinated and unmyelinated fibers with an increased production of brain-derived neurotrophic factor. ConclusionOur findings do not support the hypothesis that repurposing of the mitochondrial uncoupler 2,4-Dinitrophenol exerts functionally relevant neuro-regenerative effects in autoimmune neuritis.

Acupuncture on “Huantiao” (GB30) and "Yanglingquan" (GB34) acupoints promotes nerve regeneration in mice model of peripheral nerve injury

ObjectiveTo investigate the effects of acupuncture on promoting nerve regeneration in mice with sciatic nerve crushed injury, an animal model of peripheral nerve injury (PNI). MethodsAcupuncture was performed on the "Huantiao" (GB30) and "Yanglingquan" (GB34) acupoints in PNI mice model for 2 weeks. Gait analysis, toe spreading test, electrophysiological test, toluidine blue staining and immunostaining of myelin basic protein (MBP), neurofilament-200 (NF200), p75 neurotrophin receptor (p75NTR), and growth associated protein-43 (GAP43) were respectively performed to investigate the effects of acupuncture on crushed sciatic nerve. ResultsAcupuncture stimulation of “Huantiao” (GB30) and "Yanglingquan" (GB34) acupoints promoted the recovery of motor function and electrophysiological function in PNI mice model, which was indicated by a better gait level, toe spreading level and CMAP value in acupuncture group. The number of myelinated nerve fibers and the fluorescence intensity of MBP, NF200, p75NTR and GAP43 staining demonstrated that the acupuncture stimulation promoted the regeneration of injured nerves in PNI mice model. ConclusionAcupuncture significantly promoted the functional and morphological recovery of crushed sciatic nerve via promoting the expression of p75NTR in Schwann cells.

Micro-pharmacokinetics of lidocaine and bupivacaine transfer across a myelinated nerve fiber

BackgroundThe aim of the present study was to predict the time to onset and duration of action of two local anesthetics (lidocaine and bupivacaine) based on experimental dimensions of a typical nerve and experimental octanol/water partition coefficients. MethodsWe began our compilation of experimental data with a numerical solution of the Smoluchowski equation for the transfer of lidocaine and bupivacaine across the axon membrane in the region of the node of Ranvier (axolemma) and across the Schwann cell. The difference between the aqueous and lipid environments of the neuron was simulated by including the coordinate-dependent chemical potential. In the second step, the permeation rates calculated using the diffusion equation were used to solve a system of four ordinary differential equations. This approach allowed us to simulate the cellular environment for a longer time and to compare our model with pharmacokinetic properties (time to onset and duration of action) of local anesthetics from the literature. The behavior of local anesthetics under physiological conditions and in case of local acidosis was also simulated. ResultsWe demonstrated that local anesthetics cross the axolemma in a time span of less than 1 μs. The time to onset of action, controlled by diffusion from the epineurium to an axon with a typical distance of 500 μm, was 167 s and 186 s for lidocaine and bupivacaine, respectively. The calculated half-life, which is a measure of the duration of action, was 41 min and 328 min for lidocaine and bupivacaine, respectively. ConclusionsDuration of action is controlled by the storage capacity of lipophilic compartments around the axon, which is higher for bupivacaine but lower in local acidosis. For the latter case, the literature, including textbooks, provides a misinterpretation, namely that protonated species cannot penetrate the membrane.

Myelin protein zero mutation-related hereditary neuropathies: Neuropathological insight from a new nerve biopsy cohort.

Myelin protein zero (MPZ/P0) is a major structural protein of peripheral nerve myelin. Disease-associated variants in the MPZ gene cause a wide phenotypic spectrum of inherited peripheral neuropathies. Previous nerve biopsy studies showed evidence for subtype-specific morphological features. Here, we aimed at enhancing the understanding of these subtype-specific features and pathophysiological aspects of MPZ neuropathies. We examined archival material from two Central European centers and systematically determined genetic, clinical, and neuropathological features of 21 patients with MPZ mutations compared to 16 controls. Cases were grouped based on nerve conduction data into congenital hypomyelinating neuropathy (CHN; n = 2), demyelinating Charcot-Marie-Tooth (CMT type 1; n = 11), intermediate (CMTi; n = 3), and axonal CMT (type 2; n = 5). Six cases had combined muscle and nerve biopsies and one underwent autopsy. We detected four MPZ gene variants not previously described in patients with neuropathy. Light and electron microscopy of nerve biopsies confirmed fewer myelinated fibers, more onion bulbs and reduced regeneration in demyelinating CMT1 compared to CMT2/CMTi. In addition, we observed significantly more denervated Schwann cells, more collagen pockets, fewer unmyelinated axons per Schwann cell unit and a higher density of Schwann cell nuclei in CMT1 compared to CMT2/CMTi. CHN was characterized by basal lamina onion bulb formation, a further increase in Schwann cell density and hypomyelination. Most late onset axonal neuropathy patients showed microangiopathy. In the autopsy case, we observed prominent neuromatous hyperinnervation of the spinal meninges. In four of the six muscle biopsies, we found marked structural mitochondrial abnormalities. These results show that MPZ alterations not only affect myelinated nerve fibers, leading to either primarily demyelinating or axonal changes, but also affect non-myelinated nerve fibers. The autopsy case offers insight into spinal nerve root pathology in MPZ neuropathy. Finally, our data suggest a peculiar association of MPZ mutations with mitochondrial alterations in muscle.

Blockade of Rho-associated kinase prevents inhibition of axon regeneration of peripheral nerves induced by anti-ganglioside antibodies.

Anti-ganglioside antibodies are associated with delayed/poor clinical recovery in Guillain-Barrè syndrome, mostly related to halted axon regeneration. Cross-linking of cell surface gangliosides by anti-ganglioside antibodies triggers inhibition of nerve repair in in vitro and in vivo paradigms of axon regeneration. These effects involve the activation of the small GTPase RhoA/ROCK signaling pathways, which negatively modulate growth cone cytoskeleton, similarly to well stablished inhibitors of axon regeneration described so far. The aim of this work was to perform a proof of concept study to demonstrate the effectiveness of Y-27632, a selective pharmacological inhibitor of ROCK, in a mouse model of axon regeneration of peripheral nerves, where the passive immunization with a monoclonal antibody targeting gangliosides GD1a and GT1b was previously reported to exert a potent inhibitory effect on regeneration of both myelinated and unmyelinated fibers. Our results demonstrate a differential sensitivity of myelinated and unmyelinated axons to the pro-regenerative effect of Y-27632. Treatment with a total dosage of 9 mg/kg of Y-27632 resulted in a complete prevention of anti-GD1a/GT1b monoclonal antibody-mediated inhibition of axon regeneration of unmyelinated fibers to skin and the functional recovery of mechanical cutaneous sensitivity. In contrast, the same dose showed toxic effects on the regeneration of myelinated fibers. Interestingly, scale down of the dosage of Y-27632 to 5 mg/kg resulted in a significant although not complete recovery of regenerated myelinated axons exposed to anti-GD1a/GT1b monoclonal antibody in the absence of toxicity in animals exposed to only Y-27632. Overall, these findings confirm the in vivo participation of RhoA/ROCK signaling pathways in the molecular mechanisms associated with the inhibition of axon regeneration induced by anti-GD1a/GT1b monoclonal antibody. Our findings open the possibility of therapeutic pharmacological intervention targeting RhoA/Rock pathway in immune neuropathies associated with the presence of anti-ganglioside antibodies and delayed or incomplete clinical recovery after injury in the peripheral nervous system.

Quantification of heat shock proteins in the posterior interosseous nerve among subjects with type 1 and type 2 diabetes compared to healthy controls.

Diabetic peripheral neuropathy (DPN) is a common complication of both type 1 (T1D) and type 2 diabetes (T2D). No cure for DPN is available, but several potential targets have been proposed for treatment. Heat shock proteins (HSPs) are known to respond to both hyper- and hypoglycemia. DPN can be diagnosed using electrophysiology and studied using peripheral nerve biopsies. This study aimed to analyze the presence and patterns of HSPs in peripheral nerve biopsies from subjects with T1D, T2D, and healthy controls. Posterior interosseous nerves (PIN) from a total of 56 subjects with T1D (n = 9), with T2D (n = 24), and without diabetes (i.e., healthy controls, n = 23) were harvested under local anesthesia and prepared for quantitative mass spectrometry analysis. Protein intensities were associated with electrophysiology data of the ulnar nerve and morphometry of the same PIN, and differences in protein intensities between groups were analyzed. In total, 32 different HSPs were identified and quantified in the nerve specimens. No statistically significant differences were observed regarding protein intensities between groups. Furthermore, protein intensities did not correlate with amplitude or conduction velocity in the ulnar nerve or with the myelinated nerve fiber density of PIN. Quantitative proteomics can be used to study HSPs in nerve biopsies, but no clear differences in protein quantities were observed between groups in this cohort.

Congenital Insensitivity to Pain with Anhidrosis (CIPA): The First Reported Case in Bangladesh

Congenital insensitivity to pain with anhidrosis (CIPA) is also known as hereditary sensory and autonomic neuropathy type IV. It is an exceedingly rare autosomal recessive disease which occurs due to lack of maturation of small myelinated and unmyelinated fibers of peripheral nerves. These fibers are required for transmission of pain and temperature sensation. This disorder is characterized by insensitivity to pain with intact tactile perception, anhidrosis, self mutilation, recurrent unexplained fever, auto amputation, mental retardation & autonomic nervous system abnormality from infancy. The clinical presentation of a 4-year-old boy with this rare disease is worth to describe, as the first case to be reported in Bangladesh. Rehabilitative treatments for prevention of disease complications and their progress should be given emphasis in every encounter Journal of Current and Advance Medical Research, July 2022;9(2):91-94

Avoiding scar tissue formation of peripheral nerves with the help of an acellular collagen matrix.

Extensive scar tissue formation after peripheral nerve injury or surgery is a common problem. To avoid perineural scarring, implanting a mechanical barrier protecting the nerve from inflammation processes in the perineural environment has shown promising results for functional recovery. This study investigates the potential of an acellular collagen-elastin matrix wrapped around a peripheral nerve after induction of scar tissue formation. In the present study, 30 Lewis rats were separated into three groups and sciatic nerve scarring was induced with 2.5% glutaraldehyde (GA-CM) or 2.5% glutaraldehyde with a supplemental FDA-approved acellular collagen-elastin matrix application (GA+CM). Additionally, a sham group was included for control. Nerve regeneration was assessed by functional analysis using the Visual Statisc Sciatic Index (SSI) and MR neurography during the 12-week regeneration period. Histological and histomorphometry analysis were performed to evaluate the degree of postoperative scar tissue formation. Histological analysis showed an extensive scar tissue formation for GA-CM. Connective tissue ratio was significantly (p < 0.009) reduced for GA+CM (1.347 ± 0.017) compared to GA-CM (1.518 ± 0.057). Similarly, compared to GA+CM, MR-Neurography revealed extensive scar tissue formation for GA-CM with a direct connection between nerve and paraneural environment. Distal to the injury site, quantitative analysis presented significantly higher axon density (p = 0.0145), thicker axon diameter (p = 0.0002) and thicker myelinated fiber thickness (p = 0.0008) for GA+CM compared to GA-CM. Evaluation of functional recovery revealed a significantly faster regeneration for GA+CM. The supplemental application of an acellular collagen-elastin matrix showed beneficial effects in histological, radiological, and functional analysis. Therefore, applying a collagen-elastin matrix around the nerve after peripheral nerve injury or surgery may have beneficial effects on preventing scar tissue formation in the long run. This represents a feasible approach to avoid scar tissue formation in peripheral nerve surgery.

Modulating individual axons and axonal populations in the peripheral nerve using transverse intrafascicular multichannel electrodes.

Objective.A transverse intrafascicular multichannel electrode (TIME) may offer advantages over more conventional cuff electrodes including higher spatial selectivity and reduced stimulation charge requirements. However, the performance of TIME, especially in the context of non-conventional stimulation waveforms, remains relatively unexplored. As part of our overarching goal of investigating stimulation efficacy of TIME, we developed a computational toolkit that automates the creation and usage ofin siliconerve models with TIME setup, which solves nerve responses using cable equations and computes extracellular potentials using finite element method.Approach.We began by implementing a flexible and scalable Python/MATLAB-based toolkit for automatically creating models of nerve stimulation in the hybrid NEURON/COMSOL ecosystems. We then developed a sciatic nerve model containing 14 fascicles with 1,170 myelinated (A-type, 30%) and unmyelinated (C-type, 70%) fibers to study fiber responses over a variety of TIME arrangements (monopolar and hexapolar) and stimulation waveforms (kilohertz stimulation and cathodic ramp modulation).Main results.Our toolkit obviates the conventional need to re-create the same nerve in two disparate modeling environments and automates bi-directional transfer of results. Our population-based simulations suggested that kilohertz stimuli provide selective activation of targeted C fibers near the stimulating electrodes but also tended to activate non-targeted A fibers further away. However, C fiber selectivity can be enhanced by hexapolar TIME arrangements that confined the spatial extent of electrical stimuli. Improved upon prior findings, we devised a high-frequency waveform that incorporates cathodic DC ramp to completely remove undesirable onset responses.Conclusion.Our toolkit allows agile, iterative design cycles involving the nerve and TIME, while minimizing the potential operator errors during complex simulation. The nerve model created by our toolkit allowed us to study and optimize the design of next-generation intrafascicular implants for improved spatial and fiber-type selectivity.