Myelinated Nerve Research Articles

Oriented Graphene Oxide Scaffold Promotes Nerve Regeneration in vitro and in vivo.

Treating peripheral nerve injuries (PNI) with defects remains challenging in clinical practice. The commercial conduits have shown suboptimal nerve regeneration and functional recovery due to their basic tubular design without electroactive and oriented topographical cues. To develop a new scaffold with oriented microstructure and electroactive Graphene oxide (GO) and investigate its' therapeutic effect on nerve regeneration in vitro and in vivo. This study employed a straightforward approach to co-spin PCL and GO, yielding an oriented hybrid nanofibrous scaffold known as the O-GO/PCL scaffold. The physical and chemical properties of nanofibrous scaffold were tested by scanning electron microscopy (SEM), transmission electron microscope (TEM), tensile test and so on. Primary Schwann cells (SCs) and dorsal root ganglia (DRG) were used to investigate the impact of the newly developed scaffolds on the biological behavior of neural cells in vitro. Transcriptome sequencing (mRNA-seq) was employed to probe the underlying mechanisms of the synergistic effect of electroactive GO and longitudinal topographic guidance on nerve regeneration. Furthermore, the developed O-GO/PCL scaffold was utilized to bridge a 10-mm sciatic nerve defect in rat, aiming to investigate its therapeutic potential for peripheral nerve regeneration in vivo. The SEM and TEM revealed that the newly developed O-GO/PCL scaffold showed longitudinally oriented microstructure and GO particles were homogenously and uniformly distributed inside the nanofibers. Primary SCs were utilized to assess the biocompatibility of the GO-based scaffold, revealing that negligible cytotoxicity when GO concentration does not exceed 0.5%. In vitro analysis of nerve regeneration demonstrated that axons in the O-GO/PCL group exhibited an average length of 1054.88 ± 161.32 µm, significant longer than those in the other groups (P < 0.05). Moreover, mRNA sequencing results suggested that the O-GO/PCL scaffold could enhance nerve regeneration by upregulating genes associated with neural regeneration, encompassing ion transport, axon guidance and cell-cell interactions. Most importantly, we employed the O-GO/PCL scaffold to repair a 10-mm sciatic nerve defect in rat, resulting in augmented nerve regeneration, myelination, and functional recovery. The O-GO/PCL scaffold with oriented microstructure and electroactive GO represents a promising heral nerve reconstruction.

AI‐based studies using fundus images

The artificial intelligence (AI)/deep learning (DL) algorithms were shown to detect diseases based on image analysis, including retinal diseases from fundus photos and optical coherence tomography (OCT) scans, lung diseases from chest radiographs, and skin disorders from skin photos. It was also shown that retinal photos can be used to identify risk factors related with cardiovascular disorders, including blood pressure, smoking and body mass index.The fundus picture was shown to source data for developing AI/DL algorithms detecting many ophthalmic diseases and pathologies, including diabetic retinopathy, diabetic macular edema, retinal artery and vein occlusion, macular hole, epiretinal membrane, AMD, glaucoma, retinopathy of prematurity, myopia, myopic macular degeneration, hyperopia, optic disc edema, optic nerve atrophy, central serous retinopathy, myelinated nerve fibres, and retinitis pigmentosa. Moreover, fundus pictures were also used to develop many AI/DL algorithms detecting non ophthalmic diseases and pathologies, including Alzheimer and Parkinson disease, risk of stroke, risk of cardiac infarction, systemic hypertension, chronic renal disease, peripheral arterial disease, and anaemia.

Acer truncatum Bunge seed oil ameliorated oxaliplatin-induced demyelination by improving mitochondrial dysfunction via the Pink1/Parkin mitophagy pathway.

Dietary nutritional support for special populations is an effective and feasible method to improve the quality of life of patients and reduce medical pressure. Acer truncatum Bunge seed oil (ATSO) is widely recognized for its ability to promote nerve myelin regeneration. To evaluate the ameliorative effects of ATSO on chemotherapy-induced demyelination, a zebrafish model of chemotherapy-induced demyelination was established. The results showed that 100 μg mL-1 of ATSO reversed tail morphology damage, axon degeneration, touch response delay, ROS level upregulation and the expression of myelin basic protein decrease in chemotherapy-induced zebrafish. In addition, the expression of myelin markers (including sox10, krox20, and pmp22) in oxaliplatin-induced cells was markedly reversed by ATSO and its active components (gondoic acid, erucic acid, and nervonic acid). ATSO and its active components could reverse demyelination by ameliorating mitochondrial dysfunction. Conversely, linoleic acid and linolenic acid promoted demyelination by exacerbating mitochondrial dysfunction. Moreover, the Pink1/Parkin pathway was recognized as the main reason for ATSO and its active components improving mitochondrial function by activating mitophagy and restoring autophagic flow. Taken together, this study demonstrated that ATSO and its active components could be further developed as novel functional food ingredients to antagonize demyelination.

Influence of shortwave laser therapy on morphometric parameters of sciatic nerve regeneration after experimental neurorrhaphy

The aim of this work was to reveal the effectiveness of delayed laser therapy for the regeneration of the sciatic nerve. Materials and methods. In 21 rats, transection and epineural microsurgical suture of the right sciatic nerve (SN) were performed. In 16 rats (experimental group) in the period from 1.0 to 2.5 months after surgery, a course of laser therapy (LT-1, n = 8) and a delayed (after 6 months) course of laser therapy (LT-2, n = 8) were used 18 sessions were performed in each subgroup. Laser therapy was not performed in 5 operated animals and they were included in the control group. The terms of withdrawal of rats from the experiment were 2.5 and 12.0 months after the operation. During the morphometry of semi-thin sections distal to the level of the sutures, the volumetric density of the constituent elements of the SN, the number density of myelinated nerve fibers (MNF), their diameters, the thickness of the axons and myelin sheath, the myelination index (index G) distribution of MNF by diameter and dependence of index G on the fiber caliber were measured. For double control, we used muscle morphometry data from intact rats (Intact). Muscle tissue was additionally examined by the method of transmission electron microscopy using a generally accepted technique with a REM-100 electron microscope (Selmi, Sumy, Ukraine). Results. In the control group, as compared to the intact group, the numerical density of muscle fibers was 21 % higher, but 38 % less than the numerical density of microvessels, therefore, the vascularization index was reduced by 1.7 times. The obtained results indicated laser compensation for denervation atrophy, which was confirmed by morphometric data. Conclusions. The results of the study indicate a stimulating prolonged effect of delayed laser therapy in regenerative axonogenesis.

Neuroprotective effect of 2-ethyl-6-methyl-3-hydroxypyridine succinate on the sciatic nerve and its segmental centers in experimental paclitaxel-induced peripheral neuropathy

Up to 60 % of patients suffer from the neurotoxicity of the chemotherapy drug Paclitaxel, namely paclitaxel-induced peripheral neuropathy (PIPN), during the treatment of breast cancer, ovarian cancer, and non-small cell lung cancer. Of these, up to 25 % of patients require modification of the paclitaxel treatment regimen, including dose reduction, delay, or discontinuation of therapy. Previous attempts to use neuroprotective agents in humans and in animal models have not shown sufficient efficacy in preventing or significantly reducing the manifestations of PIPN. The aim of our study was to study the effect of the neuroprotective agent 2-ethyl-6-methyl-3-hydroxypyridine succinate (HS) on the morpho-functional parameters of the sciatic nerve and its segmental centers in experimental PIPN. In the experiment, 56 white rats were used, which were injected intraperitoneally with Paclitaxel at a dose of 2 mg/kg of body weight 4 times after one day, after which the animals were divided into an experimental group – 24 animals that were injected with HS and a control group (24 animals, injection of water for injections). The method of studying mechanical allodynia was von Frey monofilaments, thermal hyperalgesia was studied by the hot plate test, and the electron microscopic examination was carried out according to generally accepted methods and studied with the help of a PEM-125 K electron microscope. The results of the hot plate test and the use of von Frey monofilaments showed that the use of HS reliably reduces manifestations of PIPN on the 7th, 14th and 28th days of the experiment. In rats treated with HS, destructive-dystrophic phenomena in the myelin nerve fibers of the sciatic nerve are less pronounced, and in individual fibers in the axon, phenomena of incomplete splitting of mitochondria with the formation of vacuoles filled with medium electron density contents are observed, and small young mitochondria are also visualized. During the first 28 days, we noted less pronounced destructive-dystrophic changes in the neurons of the spinal cord nodes, namely: chromatolysis of light and dark neurons and swelling of their cytoplasm, phenomena of neuronophagy in gliocytes, hypertrophy of certain areas of the myelin sheath. The results of the electron microscopic study are fully consistent with the data of neurophysiological studies and indicate the possibility of using HS as an effective neuroprotector in PIPN.

Chitosan nerve conduit filled with ZIF-8-functionalized guide microfibres enhances nerve regeneration and sensory function recovery in sciatic nerve defects

Nerve conduits have shown promise as alternatives to autologous nerves, but their repair effects need to be improved. The topographical guidance and functionalization of scaffolds are crucial in nerve repair. In this work, a chitosan-based nerve graft filled with guiding fibres modified by ZIF-8 nanoparticles (CS@ZIF-8) was fabricated for defective nerve repair. An in vitro study demonstrated that CS@ZIF-8 exhibited excellent cytocompatibility and could significantly promote Schwann cell proliferation. In vivo, nerve conduits filled with CS@ZIF-8 were observed to guide stronger axonal longitudinal elongation. Rats bridged with the conduit filled with CS@ZIF-8 showed significant morphological and functional improvements in terms of regenerated nerve density, the number of myelinated nerve fibres, the number of myelin layers, the thickness of myelin sheath, target muscle recovery and sensory function compared to those transplanted with the hollow conduit and the conduit filled with pure chitosan fibres. The repair effects achieved by using the conduit filled with CS@ZIF-8 were similar to those of autografts. Altogether, the data here show that nerve conduits filled with ZIF-8-loaded guide fibres provide a promising approach for repairing nerve defects.

Neurotropin Alleviates Bortezomib-Induced Neurotoxicity Via Microglial Neuroinflammation

Objective: To investigate the effect of neurotropin (NTP) on the prevention and amelioration of neurotoxicity induced by bortezomib (BTZ)-based chemotherapy regimens and the possible mechanism of action, and to provide new ideas for the prevention mechanism and treatment of bortezomib-induced peripheral neuropathy (BIPN). Methods: The BIPN model was constructed by injecting bortezomib （ BTZ group ）or bortezomib+saline ( BTZ+NS group)into the tail vein of C57BL/6 mice. After successful modeling, NTP was added to take intraperitoneal injections for 4 weeks, which were defined to be NTP group. In order to assess the severity of BIPN, systemic toxicity, pain behavioral and sensorimotor kinetic changes in mice of different group were observed while transmission electron microscopy examination was used to observe the damage of peripheral nerve ultrastructure and myelin thickness. Immunofluorescence staining method was used to detected the activation of spinal cord microglial and their expression level of inflammatory factors such as IL-1β, IL-6 and TNF-α. ELISA was used to detected the expression of IL-1β, IL-6 and TNF-α in the dorsal horn homogenate of the spinal cord; Western blot to detect the protein expression of pathway-associated proteins JAK/STAT. Results: The Compared with the Control group, the BTZ and BTZ+NS groups showed significant decreases in mechanical, thermal pain thresholds and motor coordination compared with the Control group (P&amp;lt;0.05), and ultrastructural damage to the peripheral nerves, with demyelinating lesions and a significant reduction in the overall thickness of myelin sheaths in myelinated fibers (0.62±0.08 Vs 0.56±0.12, P＜0.01). NTP administration significantly improved pain behavioral changes, reduced ultrastructural damage, reversed demyelinating lesions and significantly increased myelin thickness (0.56±0.06 Vs 0.62±0.08, P＜0.01) in model mice compared with BTZ group. Immunofluorescence staining suggested that microglia in the dorsal horn of the spinal cord of mice in the BTZ group and the BTZ+NS group were significantly activated, which were shown the fluorescence ratio of IBA-1 + was significantly increased (2.55±0.61 Vs 0.55±0.04，2.42±0.89 Vs 0.55±0.04，P＜0.0001), while NTP significantly improved the activation of microglia in the model mice (0.71±0.13 Vs 2.55±0.61, 0.71±0.13 Vs 2.42±0.89, P&amp;lt;0.0001). The co-staining results suggest that the increase in inflammatory factors may originate from microglia. ELISA results that the expression level of IL-6 and TNF-α in NTP administration group significantly decreased compared with the group of BTZ group (IL-6: 37.87±23.2 Vs 111.8±6.0, P＜0.05; TNF-α: 547.9±17.11 Vs 998.8±333.4, P＜0.05) and the BTZ+NS group (IL-6: 37.87±23.2 Vs 88.3±15.58, P&amp;lt;0.05; TNF-α: 547.9±17.11 Vs 768.3±37.45, P&amp;lt;0.05) in the dorsal horn homogenate of the spinal cord. The results of spinal cord proteomics showed that neurotropin could induce the changes of differential proteins, such as PI3K-AKT, MAPK, JAK/STAT, which were related to inflammation. Moreover, these differential proteins can be significantly enriched in the JAK/STAT KEGG Pathway. The KEGG pathway of differential protein enrichment in the spinal cord of differential BIPN mice was detected by proteomics chip after NTP treatment, and the JAK/STAT pathway was significantly down-regulated after NTP treatment. Western blot showed that the protein expression of JAK1/STAT3 decreased after NTP administration. Conclusion: Neurotropin alleviates bortezomib induced neurotoxicity through microglial neuroinflammation, and may reduce the release of glial inflammation by regulating JAK1/STAT3 signaling pathway, thus playing a therapeutic role in BIPN. Repeated experiments are needed for further research. Keywords: Neurotropin, Bortezomib, Peripheral neuropathy, Neuroinflammation

Changes in myelinated nerve fibers induced by pulsed electrical stimulation: A microstructural perspective on the causes of electrical stimulation side effects

Electrical brain stimulation technology is widely used in the clinic to treat brain neurological disorders. However, during treatment, patients may experience side effects such as pain, poor limb coordination, and skin rash. Previous reports have focused on the brilliant chapter on electrical brain stimulation technology and have not paid attention to patients' suffering caused by side effects during treatment. In this study, electrodes were arranged on the medulla oblongata. Pulsed electric fields of different frequencies were used to perform electrical stimulation to study the impact of electric fields on myelinated nerve fibers and reveal the possible microstructural origin of side effects. Transmission electron microscopy was used to analyze and quantify the changes in microstructure. The results illustrated that myelinated nerve fibers underwent atrophy under pulsed electric fields, with the mildest degree of atrophy under high-frequency (400 Hz) electric fields. Myelin sheaths experienced plate separation under pulsed electric fields, and a distinct laminar structure appeared. The microstructure changes may be related to the side effects of clinical electrical stimulation. This study can provide pathological possibilities for exploring the causes of the side effects of electrical stimulation and supply guidance for selecting electrical parameters for clinical electrical stimulation therapy from a distinctive perspective.

Distributed loss-amplification modeling for the mid-infrared signal propagating in the myelinated and demyelinated nerve.

The terahertz (THz) to infrared (IR) neural signal model is a potential mechanism for explaining neural communication. Myelinated neurons could be a lossy dielectric waveguide that can propagate these THz-IR neural signals. We propose an electromagnetic loss-amplification model to describe the propagation characteristics of mid-IR signals on myelinated neurons. During transmission with loss and amplification, neural signal intensity can be consistently maintained at 15.9pW in bands 55 to 75THz. This phenomenon becomes more pronounced as the number of myelin sheaths increases. However, escalated degrees of demyelination result in a reduction of signal intensity from 15.9 to 10pW. This phenomenon eventually disrupts the process of loss amplification, consequently impeding the transmission of the signal. These results may contribute to a deeper understanding of mid-IR signal propagation mechanisms in myelinated nerves and studies of diseases associated with demyelination.

Proteomic analysis of peripheral nerve myelin during murine aging.

Aging of the peripheral nervous system (PNS) is associated with structural and functional changes that lead to a reduction in regenerative capacity and the development of age-related peripheral neuropathy. Myelin is central to maintaining physiological peripheral nerve function and differences in myelin maintenance, degradation, formation and clearance have been suggested to contribute to age-related PNS changes. Recent proteomic studies have elucidated the complex composition of the total myelin proteome in health and its changes in neuropathy models. However, changes in the myelin proteome of peripheral nerves during aging have not been investigated. Here we show that the proteomes of myelin fractions isolated from young and old nerves show only subtle changes. In particular, we found that the three most abundant peripheral myelin proteins (MPZ, MBP, and PRX) do not change in old myelin fractions. We also show a tendency for high-abundance myelin proteins other than these three to be downregulated, with only a small number of ribosome-related proteins significantly downregulated and extracellular matrix proteins such as collagens upregulated. In addition, we illustrate that the peripheral nerve myelin proteome reported in this study is suitable for assessing myelin degradation and renewal during peripheral nerve degeneration and regeneration. Our results suggest that the peripheral nerve myelin proteome is relatively stable and undergoes only subtle changes in composition during mouse aging. We proffer the resultant dataset as a resource and starting point for future studies aimed at investigating peripheral nerve myelin during aging. Said datasets are available in the PRIDE archive under the identifier PXD040719 (aging myelin proteome) and PXD041026 (sciatic nerve injury proteome).

Chitosan/hBMSC-ECM biomimetic nerve grafts containing orienting microchannels for peripheral nerve regeneration

Bone marrow mesenchymal stem cell extracellular matrix (BMSC-ECM) can promote peripheral nerve regeneration, and microphysical orientation is essential for peripheral nerve regeneration. In this study, human-derived BMSC-ECM (hBMSC-ECM) and microchannels were introduced into chitosan-based nerve grafts (OCS/ECM) to construct dual biomimetic nerve grafts of structure and composition. For comparison, the same procedure was applied to nerve grafts containing only orienting microchannels (OCS) and autogenous nerves. In vitro experiments showed that the prepared grafts had good blood compatibility and no cytotoxicity. In vivo studies demonstrated that OCS/ECM had better histocompatibility than OCS. The introduction of microchannels allowed chitosan nerve grafts to achieve similar repair effects as autologous nerve grafts in the functional recovery of rats with sciatic nerve defects. Further introduction of hBMSC-ECM may result in synergistic effects on structure and composition that could significantly promote the rate of nerve regeneration, myelination, and target muscle recovery. Dual biomimetic nerve grafts are attractive candidates for the treatment of critical nerve defects.

Potential therapeutic effect of olfactory ensheathing cells in neurological diseases: neurodegenerative diseases and peripheral nerve injuries.

Neurological diseases are destructive, mainly characterized by the failure of endogenous repair, the inability to recover tissue damage, resulting in the increasing loss of cognitive and physical function. Although some clinical drugs can alleviate the progression of these diseases, but they lack therapeutic effect in repairing tissue injury and rebuilding neurological function. More and more studies have shown that cell therapy has made good achievements in the application of nerve injury. Olfactory ensheathing cells (OECs) are a special type of glial cells, which have been proved to play an important role as an alternative therapy for neurological diseases, opening up a new way for the treatment of neurological problems. The functional mechanisms of OECs in the treatment of neurological diseases include neuroprotection, immune regulation, axon regeneration, improvement of nerve injury microenvironment and myelin regeneration, which also include secreted bioactive factors. Therefore, it is of great significance to better understand the mechanism of OECs promoting functional improvement, and to recognize the implementation of these treatments and the effective simulation of nerve injury disorders. In this review, we discuss the function of OECs and their application value in the treatment of neurological diseases, and position OECs as a potential candidate strategy for the treatment of nervous system diseases.

Enhanced peripheral nerve regeneration by mechano-electrical stimulation

To address limitations in current approaches for treating large peripheral nerve defects, the presented study evaluated the feasibility of functional material-mediated physical stimuli on peripheral nerve regeneration. Electrospun piezoelectric poly(vinylidene fluoride-trifluoroethylene) nanofibers were utilized to deliver mechanical actuation-activated electrical stimulation to nerve cells/tissues in a non-invasive manner. Using morphologically and piezoelectrically optimized nanofibers for neurite extension and Schwann cell maturation based on in vitro experiments, piezoelectric nerve conduits were synthesized and implanted in a rat sciatic nerve transection model to bridge a critical-sized sciatic nerve defect (15 mm). A therapeutic shockwave system was utilized to periodically activate the piezoelectric effect of the implanted nerve conduit on demand. The piezoelectric nerve conduit-mediated mechano-electrical stimulation (MES) induced enhanced peripheral nerve regeneration, resulting in full axon reconnection with myelin regeneration from the proximal to the distal ends over the critical-sized nerve gap. In comparison, a control group, in which the implanted piezoelectric conduits were not activated in vivo, failed to exhibit such nerve regeneration. In addition, at both proximal and distal ends of the implanted conduits, a decreased number of damaged myelination (ovoids), an increased number of myelinated nerves, and a larger axonal diameter were observed under the MES condition as compared to the control condition. Furthermore, unlike the control group, the MES condition exhibited a superior functional nerve recovery, assessed by walking track analysis and polarization-sensitive optical coherence tomography, demonstrating the significant potential of the piezoelectric conduit-based physical stimulation approach for the treatment of peripheral nerve injury.

Fe-Ni dual-single atoms nanozyme with high peroxidase-like activity for sensitive colorimetric and fluorometric dual-mode detection of cholesterol

Cholesterol is widely existed in nerve myelin sheath and various membrane structures, whose abnormal level would deteriorate human cells or even cause diseases. Herein, Fe-Ni dual-single-atom nanozyme was efficiently incorporated into N-doped carbon nanosheets (FeNi DSAs/N-CSs) by a simple calcination method. Its nanozyme activity and catalytic mechanism were investigated in details. The FeNi DSAs/N-CSs nanozyme showed superior peroxidase-like property, which was applied for the dual-mode determination of hydrogen peroxide (H2O2) and cholesterol. The colorimetric/fluorometric assays of H2O2 displayed the linear ranges of 1–50 mM and 5–40 mM with low limits of detection of 0.45 mM and 3.33 mM, respectively. In parallel, there exhibited the linear ranges of 0.5–5.0 mM and 0.25–5.0 mM for the colorimetric/fluorometric analysis of cholesterol, coupled with the limits of detection down to 0.19 mM and 0.044 mM, respectively. This work provided a rapid, cost-effectiveness and simple colorimetric/fluorometric method for sensitive dual-mode detection of cholesterol in human serum samples.

Astrocytes of the optic nerve exhibit a region-specific and temporally distinct response to elevated intraocular pressure

BackgroundThe optic nerve is an important tissue in glaucoma and the unmyelinated nerve head region remains an important site of many early neurodegenerative changes. In both humans and mice, astrocytes constitute the major glial cell type in the region, and in glaucoma they become reactive, influencing the optic nerve head (ONH) microenvironment and disease outcome. Despite recognizing their importance in the progression of the disease, the reactive response of optic nerve head astrocytes remains poorly understood.MethodsTo determine the global reactive response of ONH astrocytes in glaucoma we studied their transcriptional response to an elevation in IOP induced by the microbead occlusion model. To specifically isolate astrocyte mRNA in vivo from complex tissues, we used the ribotag method to genetically tag ribosomes in astrocytes, restricting analysis to astrocytes and enabling purification of astrocyte-associated mRNA throughout the entire cell, including the fine processes, for bulk RNA-sequencing. We also assessed the response of astrocytes in the more distal myelinated optic nerve proper (ONP) as glaucomatous changes manifest differently between the two regions.ResultsAstrocytes of the optic nerve exhibited a region-specific and temporally distinct response. Surprisingly, ONH astrocytes showed very few early transcriptional changes and ONP astrocytes demonstrated substantially larger changes over the course of the experimental period. Energy metabolism, particularly oxidative phosphorylation and mitochondrial protein translation emerged as highly upregulated processes in both ONH and ONP astrocytes, with the former showing additional upregulation in antioxidative capacity and proteolysis. Interestingly, optic nerve astrocytes demonstrated a limited neuroinflammatory response, even when challenged with a more severe elevation in IOP. Lastly, there were a greater number of downregulated processes in both astrocyte populations compared to upregulated processes.ConclusionOur findings demonstrate an essential role for energy metabolism in the response of optic nerve astrocytes to elevated IOP, and contrary to expectations, neuroinflammation had a limited overall role. The transcriptional response profile is supportive of the notion that optic nerve astrocytes have a beneficial role in glaucoma. These previously uncharacterized transcriptional response of optic nerve astrocytes to injury reveal their functional diversity and a greater heterogeneity than previously appreciated.

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.

A novel 3D bilayer hydrogel tri-culture system for studying functional motor units

BackgroundA motor unit (MU) is formed by a single alpha motor neuron (MN) and the muscle fibers it innervates. The MU is essential for all voluntary movements. Functional deficits in the MU result in neuromuscular disorders (NMDs). The pathological mechanisms underlying most NMDs remain poorly understood, in part due to the lack of in vitro models that can comprehensively recapitulate multistage intercellular interactions and physiological function of the MU.ResultsWe have designed a novel three-dimensional (3D) bilayer hydrogel tri-culture system where architecturally organized MUs can form in vitro. A sequential co-culture procedure using the three cell types of a MU, MN, myoblast, and Schwann cell was designed to construct a co-differentiating tri-culture on a bilayer hydrogel matrix. We utilized a µ-molded hydrogel with an additional Matrigel layer to form the bilayer hydrogel device. The µ-molded hydrogel layer provides the topological cues for myoblast differentiation. The Matrigel layer, with embedded Schwann cells, not only separates the MNs from myoblasts but also provides a proper micro-environment for MU development. The completed model shows key MU features including an organized MU structure, myelinated nerves, aligned myotubes innervated on clustered neuromuscular junctions (NMJs), MN-driven myotube contractions, and increases in cytosolic Ca2+ upon stimulation.ConclusionsThis organized and functional in vitro MU model provides an opportunity to study pathological events involved in NMDs and peripheral neuropathies, and can serve as a platform for physiological and pharmacological studies such as modeling and drug screening. Technically, the rational of this 3D bilayer hydrogel co-culture system exploits multiple distinct properties of hydrogels, facilitating effective and efficient co-culturing of diverse cell types for tissue engineering.

Regional Gene Expression in the Retina, Optic Nerve Head, and Optic Nerve of Mice with Optic Nerve Crush and Experimental Glaucoma.

A major risk factor for glaucomatous optic neuropathy is the level of intraocular pressure (IOP), which can lead to retinal ganglion cell axon injury and cell death. The optic nerve has a rostral unmyelinated portion at the optic nerve head followed by a caudal myelinated region. The unmyelinated region is differentially susceptible to IOP-induced damage in rodent models and human glaucoma. While several studies have analyzed gene expression changes in the mouse optic nerve following optic nerve injury, few were designed to consider the regional gene expression differences that exist between these distinct areas. We performed bulk RNA-sequencing on the retina and separately micro-dissected unmyelinated and myelinated optic nerve regions from naïve C57BL/6 mice, mice after optic nerve crush, and mice with microbead-induced experimental glaucoma (total = 36). Gene expression patterns in the naïve unmyelinated optic nerve showed significant enrichment of the Wnt, Hippo, PI3K-Akt, and transforming growth factor β pathways, as well as extracellular matrix-receptor and cell membrane signaling pathways, compared to the myelinated optic nerve and retina. Gene expression changes induced by both injuries were more extensive in the myelinated optic nerve than the unmyelinated region, and greater after nerve crush than glaucoma. Changes present three and fourteen days after injury largely subsided by six weeks. Gene markers of reactive astrocytes did not consistently differ between injury states. Overall, the transcriptomic phenotype of the mouse unmyelinated optic nerve was significantly different from immediately adjacent tissues, likely dominated by expression in astrocytes, whose junctional complexes are inherently important in responding to IOP elevation.

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.

Optical absorption spectra and corresponding in vivo photoacoustic visualization of exposed peripheral nerves.

Multispectral photoacoustic imaging has the potential to identify lipid-rich, myelinated nerve tissue in an interventional or surgical setting (e.g., to guide intraoperative decisions when exposing a nerve during reconstructive surgery by limiting operations to nerves needing repair, with no impact to healthy or regenerating nerves). Lipids have two optical absorption peaks within the NIR-II and NIR-III windows (i.e., 1000 to 1350nm and 1550 to 1870nm wavelength ranges, respectively) which can be exploited to obtain photoacoustic images. However, nerve visualization within the NIR-III window is more desirable due to higher lipid absorption peaks and a corresponding valley in the optical absorption of water. We present the first known optical absorption characterizations, photoacoustic spectral demonstrations, and histological validations to support in vivo photoacoustic nerve imaging in the NIR-III window. Four in vivo swine peripheral nerves were excised, and the optical absorption spectra of these fresh ex vivo nerves were characterized at wavelengths spanning 800 to 1880nm, to provide the first known nerve optical absorbance spectra and to enable photoacoustic amplitude spectra characterization with the most optimal wavelength range. Prior to excision, the latter two of the four nerves were surrounded by aqueous, lipid-free, agarose blocks (i.e., 3% w/v agarose) to enhance acoustic coupling during in vivo multispectral photoacoustic imaging using the optimal NIR-III wavelengths (i.e., 1630 to 1850nm) identified in the ex vivo studies. There was a verified characteristic lipid absorption peak at 1725nm for each ex vivo nerve. Results additionally suggest that the 1630 to 1850nm wavelength range can successfully visualize and differentiate lipid-rich nerves from surrounding water-containing and lipid-deficient tissues and materials. Photoacoustic imaging using the optimal wavelengths identified and demonstrated for nerves holds promise for detection of myelination in exposed and isolated nerve tissue during a nerve repair surgery, with possible future implications for other surgeries and other optics-based technologies.