Myelin Thickness Research Articles

Deletion of Calcineurin in Schwann Cells Does Not Affect Developmental Myelination, But Reduces Autophagy and Delays Myelin Clearance after Peripheral Nerve Injury.

In the PNS, myelination occurs postnatally when Schwann cells (SCs) contact axons. Axonal factors, such as Neuregulin-1 Type III, trigger promyelinating signals that upregulate myelin genes. Neuregulin-1 Type III has been proposed to activate calcineurin signaling in immature SCs to initiate differentiation and myelination. However, little is known about the role of calcineurin in promyelinating SCs after birth. By creating a SC conditional KO of calcineurin B (CnBscko), we assessed the effects of CnB ablation on peripheral myelination after birth in both male and female mice. Surprisingly, CnBscko mice have minimal myelination defects, no alteration of myelin thickness, and normal KROX20 expression. In contrast, we did find a unique role for calcineurin in SCs after nerve injury. Following nerve crush, CnBscko mice have slower degeneration of myelin compared with WT mice. Furthermore, absence of CnB in primary SCs delays clearance of myelin debris. SCs clear myelin via autophagy and recent literature has demonstrated that calcineurin can regulate autophagy via dephosphorylation of transcription factor EB (TFEB), a master regulator of lysosomal biogenesis and autophagy. We demonstrate that loss of CnB reduces autophagic flux in primary SCs, indicating a possible mechanism for impaired myelin clearance. In addition, ablation of CnB impairs TFEB translocation to the nucleus 3 d after crush, suggesting that calcineurin may regulate autophagy in SCs via TFEB activation. Together, our data indicate that calcineurin is not essential for myelination but has a novel role in myelin clearance after injury.SIGNIFICANCE STATEMENT Our data offer a novel mechanism for activation of autophagy after peripheral nerve injury. Efficient clearance of myelin after injury by Schwann cells is important for axonal regrowth and remyelination, which is one reason why the PNS is significantly better at recovery compared with the CNS. Improved understanding of myelin clearance allows for the identification of pathways that are potentially accessible to increase myelin clearance and improve remyelination and recovery. Finally, this paper clarifies the role of calcineurin in Schwann cells and myelination.

Amyloidosis is associated with thicker myelin and increased oligodendrogenesis in the adult mouse brain.

In Alzheimer's disease, amyloid plaque formation is associated with the focal death of oligodendrocytes and soluble amyloid β impairs the survival of oligodendrocytes in vitro. However, the response of oligodendrocyte progenitor cells (OPCs) to early amyloid pathology remains unclear. To explore this, we performed a histological, electrophysiological, and behavioral characterization of transgenic mice expressing a pathological form of human amyloid precursor protein (APP), containing three single point mutations associated with the development of familial Alzheimer's disease (PDGFB‐APPSw.Ind, also known as J20 mice). PDGFB‐APPSw.Ind transgenic mice had impaired survival from weaning, were hyperactive by 2 months of age, and developed amyloid plaques by 6 months of age, however, their spatial memory remained intact over this time course. Hippocampal OPC density was normal in P60‐P180 PDGFB‐APPSw.Ind transgenic mice and, by performing whole‐cell patch‐clamp electrophysiology, we found that their membrane properties, including their response to kainate (100 µM), were largely normal. However, by P100, the response of hippocampal OPCs to GABA was elevated in PDGFB‐APPSw.Ind transgenic mice. We also found that the nodes of Ranvier were shorter, the paranodes longer, and the myelin thicker for hippocampal axons in young adult PDGFB‐APPSw.Ind transgenic mice compared with wildtype littermates. Additionally, oligodendrogenesis was normal in young adulthood, but increased in the hippocampus, entorhinal cortex, and fimbria of PDGFB‐APPSw.Ind transgenic mice as pathology developed. As the new oligodendrocytes were not associated with a change in total oligodendrocyte number, these cells are likely required for cell replacement.

The visual white matter connecting human area prostriata and the thalamus is retinotopically organized

The human visual system is capable of processing visual information from fovea to the far peripheral visual field. Recent fMRI studies have shown a full and detailed retinotopic map in area prostriata, located ventro-dorsally and anterior to the calcarine sulcus along the parieto-occipital sulcus with strong preference for peripheral and wide-field stimulation. Here, we report the anatomical pattern of white matter connections between area prostriata and the thalamus encompassing the lateral geniculate nucleus (LGN). To this end, we developed and utilized an automated pipeline comprising a series of Apps that run openly on the cloud computing platform brainlife.io to analyse 139 subjects of the Human Connectome Project (HCP). We observe a continuous and extended bundle of white matter fibers from which two subcomponents can be extracted: one passing ventrally parallel to the optic radiations (OR) and another passing dorsally circumventing the lateral ventricle. Interestingly, the loop travelling dorsally connects the thalamus with the central visual field representation of prostriata located anteriorly, while the other loop travelling more ventrally connects the LGN with the more peripheral visual field representation located posteriorly. We then analyse an additional cohort of 10 HCP subjects using a manual plane extraction method outside brainlife.io to study the relationship between the two extracted white matter subcomponents and eccentricity, myelin and cortical thickness gradients within prostriata. Our results are consistent with a retinotopic segregation recently demonstrated in the OR, connecting the LGN and V1 in humans and reveal for the first time a retinotopic segregation regarding the trajectory of a fiber bundle between the thalamus and an associative visual area.

Allogenous Freeze-Dried Platelet-Rich Plasma Promotes Peripheral Myelin Repair in Chronic Constriction Nerve Injury

Background: Neuropathic pain is a chronic pain condition that refers to all pain that begins or is caused by a primary lesion or dysfunction or a temporary disorder in the peripheral or central nervous system (CNS). Neuropathic pain is caused by damage or injury to nerves that transfer information to the brain and spinal cord from the skin, muscles and other body parts. Platelet concentrates such as Platelet Rich Plasma (PRP) have been proven very useful for tissue regeneration since they contain high Growth Factors. PRP is tested for nerve injury to determine the potential of PRP in improving nerve. Objective: The purpose of this study is to prove the role of PRP in increasing the thickness of myelin in the process of repairing nerves on days 14 and 21. Methods: This study used three-month-old Rattus novergicus as experimental animals. Experimental animals were randomly divided into 7 groups, each consisting of six rats. On day 14 and 21 after treatment, rats were sacrificed. The examination of myelin thickness was obtained from Osmium Tetraoxide-Toluidine blue staining. Analysis of the data was performed with ANOVA test. Results: The differentiation capability of FD-PRP towards the sciatic nerve was better in the single dose PRP at 21 days, as indicated by an increase in axon remyelinization compared with differentiation in the chronic ligation group. The myelin thicknes was significantly increased (p 0.000 < 0.05) in FD-PRP groups compared to ligation group at day 21, whereas myelin thicknes no significantly increased (p < 0.05) in FD-PP groups compared to control group at day 21. Conclusion: PRP can increase axon remyelinization in neuroregeneration. Administration of PRP Single doses for 21 days show the most effective dose for neuroregeneration.

Improvement of Remyelination in Demyelinated Corpus Callosum Using Human Adipose-Derived Stem Cells (hADSCs) and Pregnenolone in the Cuprizone Rat Model of Multiple Sclerosis.

Adipose-derived stem cells (ASCs) have neuroprotective effects, and their repair ability has been approved in neurodegenerative studies. Pregnenolone as a neurosteroid plays significant roles in neurogenesis. We aimed to consider the effect of ADSCs and pregnenolone injection on the multiple sclerosis (MS) model created by cuprizone. Male Wistar rats (n = 36) were fed with an ordinary diet or a diet with cuprizone (0.6%) for 3weeks. H-ADSCs were taken from patients with lipoaspirate surgery. The rats were divided into six groups (n=6): healthy, MS, sham, pregnenolone injection, ADSCs injection, pregnenolone and ADSCs injection. Behavioral test, histological examination and TEM were conducted. The specific markers for myelin and cell differentiation were assessed using immunohistochemistry staining. Additionally, the measure of MBP and MOG gene expression and the amount of related proteins were determined using real-time RT-PCR and ELISA techniques, respectively. Histologic results showed that induced demyelination in corpus callosum fibers. TEM revealed an increased thickness of myelin in fibers in the treated groups (P < 0.05). Injection of hADSC and pregnenolone significantly increased the expression levels of MBP and MOG (P < 0.001). The mean percentage of MOG and MBP markers were significantly increased in the treated groups compared to MS and sham groups (P < 0.05). Moreover, the OD level of MBP and MOG proteins showed that their values in the ADSCs/pregnenolone group were close to those of the control group without a significant difference. Our data indicated the remyelination potency and cell differentiation can improve with ADSCs and pregnenolone treatments in the multiple sclerosis model which created by cuprizone in rats.

Evaluation of the Antioxidant and Anti‐inflammatory Effects of SMTP‐44D against Streptozotocin‐Induced Diabetic Neuropathy in Mice

ObjectiveDiabetic neuropathy (DN), a major complication of diabetic mellitus, is present in more than 50% of diabetic patients. During the early stages of pathologic progression, patients with DN may experience sensory defects such as allodynia and hyperalgesia. Patients in advanced stages may present with sensory paralysis, such as nerve injury and the degeneration of axons, which are frequently accompanied by foot ulcerations, amputations, and poor prognoses. The pathogenesis of DN primarily involves oxidative stress and inflammation; thus, oxidative stress and inflammation are considered important therapeutic targets. However, few effective therapies are approved for the treatment of painful or insensate DN. The study aimed to evaluate the antioxidant and anti‐inflammatory effects of Stachybotrys microspora triprenyl phenol‐44D (SMTP‐44D) in a mouse model of DN.MethodsWe induced diabetes in C57BL/6J male mice by administering a single intraperitoneal injection of streptozotocin (200 mg/kg). SMTP‐44D (0.3, 3, and 30 mg/kg) was subsequently administered daily from 1 to 4 weeks after the injection of streptozotocin. The effects of SMTP‐44D were evaluated by mechanical and thermal thresholds to assess allodynia and hyperalgesia, and conduction velocity and blood flow in sciatic nerves. In addition, the levels of oxidative stress and inflammatory cytokines in sciatic nerves were determined via a thiobarbituric acid reactive substances assay and enzyme‐linked immunosorbent assay, respectively. To evaluate for neurological degeneration, G‐ratios (ratio of axon diameter to myelinated fiber diameter) and myelin thickness in the Schwann cells of sciatic nerves were measured.ResultsMechanical and thermal thresholds, conduction velocity, blood flow, and myelin thickness were significantly lower in the diabetic group than in the nondiabetic group. Moreover, the levels of oxidative stress (e.g., malondialdehyde), inflammatory cytokines (e.g., tumor necrosis factor‐α, interleukin‐1β, and interleukin‐6), and G‐ratios were significantly higher in the diabetic group than in the nondiabetic group. Such results demonstrated that the DN model was successfully established. In mice with DN, treatment with SMTP‐44D significantly and dose‐dependently improved allodynia, hyperalgesia, conduction velocity of sciatic nerves, and blood flow in sciatic nerves. Furthermore, G‐ratios and myelin thickness in the Schwann cells of sciatic nerves were also significantly improved by the suppression of oxidative stress and inflammatory cytokines.ConclusionIt is believed that oxidative stress and inflammation are involved in the pathological progression of DN and that they are important therapeutic targets. Our results showed that SMTP‐44D improved DN by exerting antioxidant and anti‐inflammatory effects, which suggests that SMTP‐44D is a potential novel therapeutic agent for the treatment of DN.Support or Funding InformationThis study was supported in part by the Japan Society for the Promotion of Science KAKENHI (Grant Number 26460346, awarded to KN; Grant Number 18K14958, awarded to KS). SMTP‐44D was generously donated by TMS Co., Ltd. (Tokyo, Japan).

Relationship (?) Between Histological and Functional Measures in Moderate Contusion SCI in Adult Rat

To create a spinal cord injury (SCI), most laboratories implement a standardized method; however, considerable variability in injury size and associated functional deficits can occur across subjects. The present study was initiated to explore relationships between the histological features of spinal cord (SC) lesion and the associated functional deficits in locomotor, respiratory, and lower urinary tract (LUT) function in a widely used rat contusion SCI model that is generated using an Infinite Horizon impactor. To this end, adult female rats (n=8) received a moderate mid‐thoracic contusion SCI (200 kdyn, T8), and the impact displacement and force were recorded. Indices of functional recovery included: (1) BBB open field locomotor scoring at 1‐week post SCI, (2) total volume of expressed urine during the first 2‐weeks post SCI, and (3) diaphragm EMG activity and reflex micturition behavior and residual urine volume recorded during an acute cystometry experiment at 4‐weeks post SCI, after which the bladder was removed and weighed. Following fixation (4% PFA) and cryoprotection of the SC, 20 μm thick horizonal sections were obtained and counterstained with cresyl violet and Cyanine R / FeCl3 to visualize cell bodies and myelin, respectively, and the section at the level of the central canal was used as the site for preliminary analysis of the extent of lesion damage and degree of white matter sparing. The lesion area ranged from 27–49% and was measured by outlining the perimeter of the lesion site using a threshold tool and then normalized (%) to the area of a standardized 7 mm rostral‐caudal length region of SC that included the injury site. Myelin thickness was measured at 3 sites at the level of the injury and at the rostral and caudal ends of the tissue (uninjured) on each side of the SC, and the injury site measurements were normalized to the average myelin thickness of the corresponding uninjured side. A spared myelin index (%) using the larger minimum myelin thickness from the right or left side of the SC was then determined and ranged from 19–91%. For generation of the SCI, impactor displacement varied from 1287 to 1728 μm, with larger displacements being associated with larger injury sites and less myelin sparing. The lesion area, however, was not a strong predictor of myelin sparing, particularly in cases with asymmetrical lesions (n=2). Both lesion area and spared myelin index were reasonable predictors of post SCI recovery of locomotor (BBB scores) and LUT (expressed urine volume) function but not in predicting the degree of dysfunction in reflex micturition (increased residual volume) and bladder hypertrophy or inspiratory burst measures and their variability. These preliminary results suggest that factors in addition to the histological characteristics of the lesion site contribute to the degree of functional deficits/recovery following SCI.Support or Funding InformationDOD CDMRP W81XWH‐17‐1‐0260; NIH NS096514; NYS DOH SCIRB C32088GG

Platelet-rich fibrin membrane nerve guidance conduit: a potentially promising method for peripheral nerve injuries.

Platelet-rich fibrin membrane nerve guidance conduit: a potentially promising method for peripheral nerve injuries.

Strategies for Autonomic Nervous System Mapping of Fiber Composition and Neural Circuitry Using Transmission Electron Microscopy in Support of SPARC Projects

The optimization of neuromodulation strategies is important for a development and refinement of therapies. The design of customized tools, such as electrical stimulating devices, depends on the detailed knowledge of nerve fiber composition and inter‐relationships between target organs, nerve populations, and synaptic circuitry. The autonomic nervous system gives support to organs and are composed by myelinated and unmyelinated fibers as well as pre‐ and post‐ganglionic neurons. Mapping an autonomic nerve such as the pelvic or vagus nerve that innervates peripheral tissues and understanding the synaptology of neurons in the cardiac and stellate ganglia may provide advanced knowledge for improved neuromodulation strategies. Transmission electron microscopy (TEM) is a high‐level technology that helps to identify and characterize axonal myelination and ultrastructure of unmyelinated fibers. TEM also allows for fine structural analysis of neural circuitry and innervation of autonomic targets. Immunogold detection techniques using TEM permits the identification and characterization of neuronal tracers in the nervous system. With the support from the Stimulating Peripheral Activity to Relieve Conditions (SPARC) program at NIH, we developed customized ultrastructural studies of the autonomic nervous system to facilitate refinement of neuromodulation strategies related to the autonomic control of cardiac, gastrointestinal, and lower urinary tract systems. Morphometric analysis is performed by automatic segmentation, and the development of a new strategy to calculate measurements of axon diameter, fiber diameter, myelin thickness, and G‐ratio provides a better understanding of fiber size for modelling studies. Both males and females from different species, including humans, are analyzed and compared. Implementation of common sampling techniques for nerves and ganglia across species provides increased rigor and reproducibility. TEM studies promote an improved understanding of functional studies and provide critical ultrastructural information for the development of new neuromodulation strategies.Support or Funding InformationSPARC/NIH 1OT2OD026585‐01 and Dr Miriam and Sheldon G. Adelson Medical Research Foundation (AMRF)

Rnd2 Uniquely Regulates Myelination by Oligodendrocytes Depending on Myelinating Process

Oligodendrocyte precursor cells differentiate into oligodendrocytes to wrap their plasma membranes around axons. While myelination is known to be one of the most dynamic cell morphological changes, the overall molecular pictures remain to be elucidated. Herein we describe the biphasic roles of Rnd2, an atypical branch of the Rho GTPase, in oligodendrocyte myelination during development and after maturation. Oligodendrocyte-specific Rnd2 knockout mice exhibit decreased myelin thickness in the onset of myelination whereas the knockout increased thickness in the subsequent process. Consistently, the biphasic role of Rnd2 is obtained using oligodendrocyte-specific Rnd2 transgenic mice. Indeed, Rho kinase and the substrate Mbs, the signaling unit regulating negatively myelination, exist in the decreased phosphorylated forms in the early developmental stage and in the increased phosphorylated forms in the subsequent stage. Therefore, Rnd2 uniquely regulates myelination, demonstrating the presence of a modulator that plays different roles depending on the myelination process.

Electrophysiological parameters that contribute to the pathogenesis of familial amyloid polyneuropathy caused by transthyretin mutations

Familial amyloid polyneuropathy (FAP) is a rare, hereditary peripheral neuropathy commonly caused by mutations in human transthyretin (TTR) gene. Clinically, FAP caused by TTR mutations (TTR-FAP) involves both large and small nerve fibers. Details of early electrophysiological features in TTR-FAP remain unclear. To address this issue, we evaluated nerve excitability (NET) results in motor axons of control mice and two transgenic mouse models carrying V30M (TTRV30M) or A97S (TTRA97S) mutations that simulate clinical features of TTR-FAP. Transgenic TTRV30M and TTRA97S mice demonstrated significant increases in latency in hindlimb withdraw tests, as well as, poor rotarod test performance, compared to TTRORF mice. NET evaluation showed reduced S2 accommodation, and increased TEdundershoot during threshold electrotonus (TE) in motor axons of both TTRV30M and TTRA97S mice, indicating that axonal membranes were in a depolarized state. Decreased rheobase combined with increased refractoriness in the transgenic mice suggested that there were reduced sodium currents. Further immunohistochemical study of the sciatic nerves revealed the significantly decrease of voltage-gated sodium channel expression in the transgenic mice. Moreover, superexcitability during the recovery cycle is significantly increased in transgenic mice compared with control mice, which is attributed to increased internodal capacitance. Finally, the electron microscopy demonstrated the reduced g-ratio in TTRA97S mice may correlate with an atrophic change of axons and/or increase of myelin thickness. In summary, we evaluated NET results in transgenic mice which modeled the clinical features presented in TTR-FAP patients. Reduced sodium channel expression and increased internodal capacitance are factors contributing to the electrophysiological changes in TTR-FAP.

Experimental Demyelination of the Lateral Olfactory Tract and Anterior Commissure

Demyelination significantly affects brain function. Several experimental methods, each inducing varying levels of myelin and neuronal damage, have been developed to understand the process of myelin loss and to find new therapies to promote remyelination. The present work investigates the effect of one such method, lysolecithin administration, on the white matter tracts in the olfactory system. The olfactory forebrain contains two distinct tracts with differing developmental histories, axonal composition, and function: the lateral olfactory tract (LOT), which carries ipsilateral olfactory information from the olfactory bulb to olfactory cortex, and the anterior commissure (AC), which interconnects olfactory regions across hemispheres. The effects of lysolecithin injections were assessed in two ways: (1) the expression of myelin basic protein, a component of compacted myelin sheaths, was quantified using immunohistochemistry and (2) electron microscopy was used to obtain measurements of myelin thickness of individual axons as well as qualitative descriptions of the extent of damage to myelin and surrounding tissue. Data were collected at 7, 14, 21, and 30 days post-injection (dpi). While both the LOT and AC exhibited significant demyelination at 7 dpi and had returned to control levels by 30 dpi, the process differed between the two tracts. Remyelination occurred more rapidly in the LOT: substantial recovery was observed in the LOT by 14 dpi, but not in the AC until 21 dpi. The findings indicate that (a) the LOT and AC are indeed suitable tracts for studying lysolecithin-induced de- and remyelination and (b) experimental demyelination proceeds differently between the two tracts.

Journal Digest: Events Before First-Episode Psychosis; Poor Neuron Insulation and Autism; Memory Suppression and Adaptation After Trauma

Journal Digest: Events Before First-Episode Psychosis; Poor Neuron Insulation and Autism; Memory Suppression and Adaptation After Trauma

Conditional depletion of Fus in oligodendrocytes leads to motor hyperactivity and increased myelin deposition associated with Akt and cholesterol activation.

Fused in sarcoma (FUS) is a predominantly nuclear multifunctional RNA/DNA-binding protein that regulates multiple aspects of gene expression. FUS mutations are associated with familial amyotrophic lateral sclerosis (fALS) and frontotemporal lobe degeneration (FTLD) in humans. At the molecular level, the mutated FUS protein is reduced in the nucleus but accumulates in cytoplasmic granules. Oligodendrocytes (OL) carrying clinically relevant FUS mutations contribute to non-cell autonomous motor neuron disease progression, consistent with an extrinsic mechanism of disease mediated by OL. Knocking out FUS globally or in neurons lead to behavioral abnormalities that are similar to those present in FTLD. In this study, we sought to investigate whether an extrinsic mechanism mediated by loss of FUS function in OL contributes to the behavioral phenotype. We have generated a novel conditional knockout (cKO) in which Fus is selectively depleted in OL (FusOL cKO). The FusOL cKO mice show increased novelty-induced motor activity and enhanced exploratory behavior, which are reminiscent of some manifestations of FTLD. The phenotypes are associated with greater myelin thickness, higher number of myelinated small diameter axons without an increase in the number of mature OL. The expression of the rate-limiting enzyme of cholesterol biosynthesis (HMGCR) is increased in white matter tracts of the FusOL cKO and results in higher cholesterol content. In addition, phosphorylation of Akt, an important regulator of myelination is increased in the FusOL cKO. Collectively, this work has uncovered a novel role of oligodendrocytic Fus in regulating myelin deposition through activation of Akt and cholesterol biosynthesis.

A genome-wide CRISPR/Cas9 screen reveals that the aryl hydrocarbon receptor stimulates sphingolipid levels

Sphingolipid biosynthesis generates lipids for membranes and signaling that are crucial for many developmental and physiological processes. In some cases, large amounts of specific sphingolipids must be synthesized for specialized physiological functions, such as during axon myelination. How sphingolipid synthesis is regulated to fulfill these physiological requirements is not known. To identify genes that positively regulate membrane sphingolipid levels, here we employed a genome-wide CRISPR/Cas9 loss-of-function screen in HeLa cells using selection for resistance to Shiga toxin, which uses a plasma membrane-associated glycosphingolipid, globotriaosylceramide (Gb3), for its uptake. The screen identified several genes in the sphingolipid biosynthetic pathway that are required for Gb3 synthesis, and it also identified the aryl hydrocarbon receptor (AHR), a ligand-activated transcription factor widely involved in development and physiology, as being required for Gb3 biosynthesis. AHR bound and activated the gene promoter of serine palmitoyltransferase small subunit A (SPTSSA), which encodes a subunit of the serine palmitoyltransferase that catalyzes the first and rate-limiting step in de novo sphingolipid biosynthesis. AHR knockout HeLa cells exhibited significantly reduced levels of cell-surface Gb3, and both AHR knockout HeLa cells and tissues from Ahr knockout mice displayed decreased sphingolipid content as well as significantly reduced expression of several key genes in the sphingolipid biosynthetic pathway. The sciatic nerve of Ahr knockout mice exhibited both reduced ceramide content and reduced myelin thickness. These results indicate that AHR up-regulates sphingolipid levels and is important for full axon myelination, which requires elevated levels of membrane sphingolipids.

Ketogenic Diet Potentiates Electrical Stimulation-Induced Peripheral Nerve Regeneration after Sciatic Nerve Crush Injury in Rats.

Recent findings indicate that the ketogenic diet (KD) is neuroprotective and electrical stimulation (ES) can improve functional recovery from peripheral nerve injury. However, it is not clear whether KD and ES play a synergistical role in the peripheral nerve recovery following injury. A KD consisting of a 3:1 ratio of fat to carbohydrate+protein is used and is coupled with ES treatment in a rat model of peripheral nerve crush injury. Neuromuscular recovery is evaluated by electromyography, and axonal regeneration and myelination by histological methods. The effects on insulin-like growth factor 1 (IGF-1) and IGF-1 receptor expression in peripheral nerve tissue, pre- and post-nerve injury, are also investigated. The combination of KD and ES synergistically increases muscle force in biceps femoris and gluteus maximus and prevents development of hypersensitivity in biceps femoris. It promotes peripheral nerve regeneration by increasing total axons, axon density, and axonal diameter, as well as myelin thickness and axon/fiber ratio. These effects are due to modulation of the IGF system as the treatment expression of IGF-1 and IGF-1 receptor in regenerated nerve tissue. The results establish that KD and ES promote peripheral nerve regeneration. Patients recovering from peripheral nerve injury may benefit from this combinational approach.

Histologic evaluation of femoral nerve demyelinating and axonal neuropathy in Wistar rats due to alendronate intake: a randomised study

BackgroundBisphosphonates (BPs) are forceful inhibitors of osteoclast-mediated bone resorption. Long-term BP use is associated with multiple rare but severe adverse effects. The objective of this study was to investigate the possible effects of BPs in the structure of femoral nerve. Specimens from the femoral nerve of ten female 12-month old Wistar rats were used as control group and ten female 12-month old Wistar rats to which Alendronate (Fosamax, Merck) was administered per os for 13 weeks, were used as research group. Samples were observed under a Transmission Electron Microscope. G ratio measurements and statistical analysis with SPSS program were also performed.ResultsThe control group showed no major changes of the nerve’s histologic image, with the exception of some spots of thickness of the nerve myelin sheath. The research group showed major morphological changes which varied from partial disorganization or thickening of the myelin to severe myelin thickening and axon strangulation. A statistically significant difference of the G ratio between the two groups was observed.ConclusionsThe reported values (found in literature) for the morphologic measurements of the femoral nerve in Wistar rats are not complying with the ones we found in our study. There was a significant reduction of all three variables (the mean axon like diameter, the myelin thickness, G ratio) studied in the femoral nerve of the research group in contrast to control group. Our study demonstrates a possible correlation between alendronate administration and femoral nerve’s function, nevertheless due to the small specimen further research is needed.

Different patterns in age-related morphometric alteration of myelinated fibers and capillaries of the tibial nerve: a longitudinal study in normal rats.

Age-related regression of myelinated fibers in peripheral nerves of the lower limbs is strongly influenced by capillaries and results in balance dysfunction and falls. However, the temporal relationships between alteration patterns of myelinated fibers and capillaries have not yet been clarified. This study aimed to investigate age-related morphological and histological changes of both myelinated fibers and capillaries in peripheral nerves to clarify whether myelinated fibers or capillaries change earlier. Seven male Wistar rats each were randomly selected at 20weeks (young group), 70weeks (middle group), and 97weeks (old group) for histological evaluations. The left and right tibial nerves were removed morphologically and histologically to examine myelinated fibers and capillaries. Axon diameter and myelin thickness were almost unaltered in the middle group compared with the young group but were significantly reduced in the old group when compared with the other two groups. However, the capillary diameter and number of microvascular branch points were substantially reduced in the middle group. The current study demonstrates that myelinated fibers of peripheral nerves show signs of regression in elderly rats, whereas capillaries start to reduce in middle-aged animals. In normal aging of the tibial nerve, capillaries may regress before myelinated fibers.

Functions of histone modifications and histone modifiers in Schwann cells.

Schwann cells (SCs) are the main glial cells present in the peripheral nervous system (PNS). Their primary functions are to insulate peripheral axons to protect them from the environment and to enable fast conduction of electric signals along big caliber axons by enwrapping them in a thick myelin sheath rich in lipids. In addition, SCs have the peculiar ability to foster axonal regrowth after a lesion by demyelinating and converting into repair cells that secrete neurotrophic factors and guide axons back to their former target to finally remyelinate regenerated axons. The different steps of SC development and their role in the maintenance of PNS integrity and regeneration after lesion are controlled by various factors among which transcription factors and chromatin-remodeling enzymes hold major functions. In this review, we discussed how histone modifications and histone-modifying enzymes control SC development, maintenance of PNS integrity and response to injury. The functions of histone modifiers as part of chromatin-remodeling complexes are discussed in another review published in the same issue of Glia.

Abstract WP496: Optogenetic Neuronal Stimulation Promotes Myelination After Subcortical Ischemic Vascular Dementia

Introduction: Subcortical ischemic small vessel disease (SIVD) causing hypoxic-ischemic white matter lesions is one of the major subtypes of Vascular dementia. White matter damage is associated with short-term working memory deficits in which medial prefrontal cortex (mPFC) plays a central role. Recent studies have reported that active neurons may produce white matter changes and enhance connectivity. However, little is known about how white matter damage impairs short-term working memory and whether neuronal activity promotes white matter restore in SIVD. In the present study, we used optogenetics in bilateral common carotid artery stenosis (BCAS) model mice to find the damaged circuit and explore whether neuronal activity could ameliorate white matter damage. Methods: Fiber photometry system monitoring in vivo calcium (Ca 2+ ) transients was performed to explore the damaged circuit of BCAS model mice. The damaged circuit were labelled using AAV expressing channel-rhodopsin 2 (CHR2). Optogenetics were used to selectively activate neurons expressing CHR2. The thymidine analog 5-ethynyl-2 ’ -deoxyuridine (EDU) was administered at the time of optogenetic stimulation to mark dividing cells and immunofluorescence was performed to identify the proliferating cell types. Transmission electron microscope (TEM) was used to evaluate myelin thickness. Y-mazes were performed to evaluated short-term working memory. Results and Conclusions: The structure and function of glutamatergic neurons in the circuit from mPFC to corpus callosum (CC) were damaged in BCAS model mice. And optogenetics stimulation of mPFC projecting glutamatergic neurons resulted in proliferation of oligodendrocyte in CC. Besides, an increase of myelin thickness and improved short-term working memory were found after three weeks of optogenetics stimulation. These results suggest that SIVD affected short-term working memory through damaging neuron projections from mPFC to CC, and optogenetic neuronal activity could regulate myelination and restore white matter damage.