Human Nerve Research Articles

Observational study of cenegermin for the treatment of limbal stem cell deficiency associated with neurotrophic keratopathy.

Neurotrophic keratopathy (NK) and limbal stem cell deficiency (LSCD) have high morbidity and require aggressive management to prevent permanent vision loss. Cenegermin, a recombinant human nerve growth factor, was approved by the Federal Drug Administration in 2018 for the treatment of NK. To determine the efficacy and safety of cenegermin in the treatment of LSCD associated with NK. Prospective cohort study. Patients diagnosed with LSCD and NK who had failed conventional treatment were enrolled in this prospective open-label study. Patients were treated with cenegermin for 8 weeks. The primary objective was to determine whether the area of abnormal epithelium decreased following treatment. Corneal sensation, visual acuity (VA), and LSCD severity were also evaluated. Six eyes of 5 patients were included in the study. Cenegermin significantly improved the area of abnormal corneal epithelium in 5 of 6 eyes, measuring 73% of total corneal area at the initial visit and 48% at the final visit (P = .036). Corneal sensation improved in all patients, Cochet-Bonnet aesthesiometry measured 14.7 and 26.7 mm at the initial and final visit, respectively (P = .009). VA improved in 4 out of 6 eyes, with mean initial logMAR VA of 1.67 and final logMAR VA of 1.19 (P = .045). Finally, LSCD grading improved using the Aravena scoring system; however, this difference was not statistically significant (P = .14). One patient presented with an epithelial defect at baseline, which resolved following treatment. No patient withdrew from the study due to adverse effects. Cenegermin effectively improved the cornea epithelium, VA, and corneal sensation in patients with LSCD and NK who had failed prior treatment. Further studies are necessary to better understand the anatomical changes and to confirm our results with a larger randomized control trial. The study was registered at ClinicalTrials.gov with identifier NCT04552730 (https://clinicaltrials.gov/ct2/show/NCT04552730).

Retesting Conjecture of Acupuncture in Traditional Chinese Medicine Theory

This study proposes the following hypothesis based on studies from various aspects and various historical periods in acupuncture: meridians and collaterals are a continuous, interwoven and ordered system of cells with the same active vibration frequency that guides human nerve activity and blood circulation, and acupuncture can temporarily open, unblock or shut such a system. Yin and Yang depend on the acidity and alkalinity of the internal and external liquid of cells caused by the human body after ingestion of food or influenced by the environment. Traditional Chinese medicine can help the human body adjust the acid-base balance, which is to say, adjust the imbalance state of Yin and Yang. The structure of functional active groups determines the efficacy of traditional Chinese medicine, and the structure can be predicted by using the principle of topology to play a role in the treatment of the corresponding target.

Apical Reference Stimulation: A Possible Solution to Facial Nerve Stimulation.

Postimplantation facial nerve stimulation is a common side-effect of intracochlear electrical stimulation. Facial nerve stimulation occurs when electric current intended to stimulate the auditory nerve, spread beyond the cochlea to excite the nearby facial nerve, causing involuntarily facial muscle contractions. Facial nerve stimulation can often be resolved through adjustments in speech processor fitting but, in some instances, these measures exhibit limited benefit or may have a detrimental effect on speech perception. In this study, apical reference stimulation mode was investigated as a potential intervention to facial nerve stimulation. Apical reference stimulation is a bipolar stimulation strategy in which the most apical electrode is used as the reference electrode for stimulation on all the other intracochlear electrodes. A person-specific model of the human cochlea, facial nerve and electrode array, coupled with a neural model, was used to predict excitation of auditory and facial nerve fibers. These predictions were used to evaluate the effectiveness in reducing facial nerve stimulation using apical reference stimulation. Predictions were confirmed in psychoacoustic tests by determining auditory comfort and threshold levels for the apical reference stimulation mode while capturing electromyography data in two participants. Models predicted a favorable outcome for apical reference stimulation, as facial nerve fiber thresholds were higher and auditory thresholds were lower, in direct comparison to conventional monopolar stimulation. Psychophysical tests also illustrated decreased auditory thresholds and increased dynamic range during apical reference stimulation. Furthermore, apical reference stimulation resulted in lower electromyography energy levels, compared to conventional monopolar stimulation, which suggests a reduction in facial nerve stimulation. Subjective feedback corroborated that apical reference stimulation alleviated facial nerve stimulation. Apical reference stimulation may be a viable strategy to alleviate facial nerve stimulation considering the improvements in dynamic range and auditory thresholds, complemented with a reduction in facial nerve stimulation symptoms.

Neuroprotective role of human neuritin 1 on axotomized human eyes pressurized using the Translaminar Autonomous System

Purpose: Primary open-angle glaucoma is a leading cause of vision loss worldwide characterized by retinal ganglion cell death (RGC) and visual field loss. Glaucoma is most commonly associated with an increase in intraocular pressure (IOP), and current clinical management is limited to lowering intraocular pressure. We have previously shown that the secreted human protein neuritin 1 (NRN1) exhibits neuroprotection, regeneration, and preservation of RGC function after RGC axonal injury. We propose to overcome RGC degeneration by over-expressing NRN1 in our novel ex-vivo perfused pressurized Translaminar Autonomous System (TAS). 
 Methods: Human donor eyes were obtained from eye banks. To model glaucomatous conditions, dissected human posterior eye cups were cultured in the TAS model with IOP:ICP conditions of 16:12 mmHg over 6 days. Flow rate of perfusion medium to the interior and exterior (around optic nerve) of the eye cup (IOP and ICP, respectively) was controlled by automated pumps to induce the translaminar pressure gradient.We assessed survival of RGCs with and without hNRN1 treatment by TaqMan array analysis of apoptosis/inflammatory markers (retina). Expression of FN and COLIV was examined from conditioned medium of both groups by Western analysis. 
 Results: We successfully maintained IOP: ICP differentials over 6 days. The RGCs degenerated faster in non-treated conditions compared to NRN1 treated eyes. In contrast to control, NRN1-treated group displayed differential expression of FN and COLIV. We observed dysregulated expression of GFAP, BAX and TLR4 expression between control and experimental conditions. 
 Conclusion: We utilized our unique TAS model to recreate the human optic nerve head environment of elevated translaminar pressure for testing a unique neuroprotective and regenerative gene therapy. Using this approach, we hope to identify human Neuritin 1 as a therapeutic gene to save the visual neurons and develop a new treatment for glaucoma.

Polarity Sensitivity of Human Auditory Nerve Fibers Based on Pulse Shape, Cochlear Implant Stimulation Strategy and Array.

Neural health is of great interest to determine individual degeneration patterns for improving speech perception in cochlear implant (CI) users. Therefore, in recent years, several studies tried to identify and quantify neural survival in CI users. Among all proposed techniques, polarity sensitivity is a promising way to evaluate the neural status of auditory nerve fibers (ANFs) in CI users. Nevertheless, investigating neural health based on polarity sensitivity is a challenging and complicated task that involves various parameters, and the outcomes of many studies show contradictory results of polarity sensitivity behavior. Our computational study benefits from an accurate three-dimensional finite element model of a human cochlea with realistic human ANFs and determined ANF degeneration pattern of peripheral part with a diminishing of axon diameter and myelination thickness based on degeneration levels. In order to see how different parameters may impact the polarity sensitivity behavior of ANFs, we investigated polarity behavior under the application of symmetric and asymmetric pulse shapes, monopolar and multipolar CI stimulation strategies, and a perimodiolar and lateral CI array system. Our main findings are as follows: (1) action potential (AP) initiation sites occurred mainly in the peripheral site in the lateral system regardless of stimulation strategies, pulse polarities, pulse shapes, cochlear turns, and ANF degeneration levels. However, in the perimodiolar system, AP initiation sites varied between peripheral and central processes, depending on stimulation strategies, pulse shapes, and pulse polarities. (2) In perimodiolar array, clusters formed in threshold values based on cochlear turns and degeneration levels for multipolar strategies only when asymmetric pulses were applied. (3) In the perimodiolar array, a declining trend in polarity (anodic threshold/cathodic threshold) with multipolar strategies was observed between intact or slight degenerated cases and more severe degenerated cases, whereas in the lateral array, cathodic sensitivity was noticed for intact and less degenerated cases and anodic sensitivity for cases with high degrees of degeneration. Our results suggest that a combination of asymmetric pulse shapes, focusing more on multipolar stimulation strategies, as well as considering the distances to the modiolus wall, allows us to distinguish the degeneration patterns of ANFs across the cochlea.

Age-related reduction in frequency-following responses as a potential marker of cochlear neural degeneration

Healthy aging may be associated with neural degeneration in the cochlea even before clinical hearing loss emerges. Reduction in frequency-following responses (FFRs) to tonal carriers in older clinically normal-hearing listeners has previously been reported, and has been argued to reflect an age-dependent decline in temporal processing in the central auditory system. Alternatively, age-dependent loss of auditory nerve fibers (ANFs) may have little effect on audiometric sensitivity and yet compromise the precision of neural phase-locking relying on joint activity across populations of fibers. This peripheral loss may, in turn, contribute to reduced neural synchrony in the brainstem as reflected in the FFR. Here, we combined human electrophysiology and auditory nerve (AN) modeling to investigate whether age-related changes in the FFR would be consistent with peripheral neural degeneration. FFRs elicited by pure tones and frequency sweeps at carrier frequencies between 200 and 1200 Hz were obtained in older (ages 48–76) and younger (ages 20–30) listeners, both groups having clinically normal audiometric thresholds up to 6 kHz. The same stimuli were presented to a computational model of the AN in which age-related loss of hair cells or ANFs was modelled using human histopathological data. In the older human listeners, the measured FFRs to both sweeps and pure tones were found to be reduced across the carrier frequencies examined. These FFR reductions were consistent with model simulations of age-related ANF loss. In model simulations, the phase-locked response produced by the population of remaining fibers decreased proportionally with increasing loss of the ANFs. Basal-turn loss of inner hair cells also reduced synchronous activity at lower frequencies, albeit to a lesser degree. Model simulations of age-related threshold elevation further indicated that outer hair cell dysfunction had no negative effect on phase-locked AN responses. These results are consistent with a peripheral source of the FFR reductions observed in older normal-hearing listeners, and indicate that FFRs at lower carrier frequencies may potentially be a sensitive marker of peripheral neural degeneration.

Research on Chemical Process Optimization Based on Artificial Neural Network Algorithm

Artificial Neural Network (ANN) is established by imitating the human brain's nerve thinking mode. Because of its strong nonlinear mapping ability, fault tolerance and self-learning ability, it is widely used in many fields such as intelligent driving, signal processing, process control and so on. This article introduces the basic principles, development history and three common neural network types of artificial neural networks, BP neural network, RBF neural network and convolutional neural network, focusing on the research progress of the practical application of neural networks in chemical process optimization.

Human organ donor-derived vagus nerve biopsies allow for well-preserved ultrastructure and high-resolution mapping of myelinated and unmyelinated fibers

The vagus nerve provides motor, sensory, and autonomic innervation of multiple organs, and electrical vagus nerve stimulation (VNS) provides an adjunctive treatment option for e.g. medication-refractory epilepsy and treatment-resistant depression. The mechanisms of action for VNS are not known, and high-resolution anatomical mapping of the human vagus nerve is needed to better understand its functional organization. Electron microscopy (EM) is required for the detection of both myelinated and unmyelinated axons, but access to well-preserved human vagus nerves for ultrastructural studies is sparse. Intact human vagus nerve samples were procured intra-operatively from deceased organ donors, and tissues were immediately immersion fixed and processed for EM. Ultrastructural studies of cervical and sub-diaphragmatic vagus nerve segments showed excellent preservation of the lamellated wall of myelin sheaths, and the axolemma of myelinated and unmyelinated fibers were intact. Microtubules, neurofilaments, and mitochondria were readily identified in the axoplasm, and the ultrastructural integrity of Schwann cell nuclei, Remak bundles, and basal lamina was also well preserved. Digital segmentation of myelinated and unmyelinated axons allowed for determination of fiber size and myelination. We propose a novel source of human vagus nerve tissues for detailed ultrastructural studies and mapping to support efforts to refine neuromodulation strategies, including VNS.

Reconstructing subcortical and cortical somatosensory activity via the RAMUS inverse source analysis technique using median nerve SEP data

This study concerns reconstructing brain activity at various depths based on non-invasive EEG (electroencephalography) scalp measurements. We aimed at demonstrating the potential of the RAMUS (randomized multiresolution scanning) technique in localizing weakly distinguishable far-field sources in combination with coinciding cortical activity. As we have shown earlier theoretically and through simulations, RAMUS is a novel mathematical method that by employing the multigrid concept, allows marginalizing noise and depth bias effects and thus enables the recovery of both cortical and subcortical brain activity. To show this capability with experimental data, we examined the 14–30 ms post-stimulus somatosensory evoked potential (SEP) responses of human median nerve stimulation in three healthy adult subjects. We aim at reconstructing the different response components by evaluating a RAMUS-based estimate for the primary current density in the nervous tissue. We present source reconstructions obtained with RAMUS and compare them with the literature knowledge of the SEP components and the outcome of the unit-noise gain beamformer (UGNB) and standardized low-resolution brain electromagnetic tomography (sLORETA). We also analyzed the effect of the iterative alternating sequential technique, the optimization technique of RAMUS, compared to the classical minimum norm estimation (MNE) technique. Matching with our previous numerical studies, the current results suggest that RAMUS could have the potential to enhance the detection of simultaneous deep and cortical components and the distinction between the evoked sulcal and gyral activity.

Repair of peripheral nerve injuries using a prevascularized cell-based tissue-engineered nerve conduit

One of the major challenges in the development of a larger and longer nerve conduit for peripheral nerve repair is the limitation in oxygen and nutrient diffusion within the tissue after transplantation preventing Schwann cell and axonal migration. This restriction is due to the slow neovascularization process of the graft starting from both nerve endings. To overcome this limitation, we propose the design of a living tissue-engineered nerve conduit made of an internal tube with a three-dimensional structure supporting axonal migration, which is inserted inside a hollow external tube that plays the role of an epineurium and is strong enough to be stitched to the severed nerve stumps. The internal tube is made of a rolled living fibroblast sheet and can be seeded with endothelial cells to promote the formation of a network containing capillary-like structures which allow rapid inosculation with the host nerve microvasculature after grafting. Human nerve conduits were grafted in immunodeficient rats to bridge a 15 mm sciatic nerve gap. Human capillaries within the pre-vascularized nerve conduit successfully connected to the host circulation 2 weeks after grafting. Twenty-two weeks after surgery, rats transplanted with the nerve conduits had a similar motor function recovery compared to the autograft group. By promoting rapid vascularization of the internal nerve tube from both ends of the nerve stumps, this endothelialized nerve conduit model displays a favorable environment to enhance axonal migration in both larger caliber and longer nerve grafts.

Efficacy of rhNGF-loaded amniotic membrane transplantation for rabbit corneal epithelial and nerve regeneration.

To evaluate the efficacy of recombinant human nerve growth factor-loaded amniotic membrane (rhNGF-AM) on corneal epithelial and nerve regeneration in rabbit model. Freshly prepared human amniotic membrane (AM) were immersed into PBS buffer containing 100 or 500 µg/mL rhNGF for 15, 30, and 60min at 4°C. The in vitro release kinetics of rhNGF was measured with ELISA. For in vivo evaluation, the AM were immersed with 500 µg/mL rhNGF for 30min. Fifty-seven rabbits were selected to establish corneal epithelial defect model. In addition to the 19 rabbits in control group, 38 rabbits received AM transplantation with or without rhNGF after the removal of central epithelium. Corneal epithelial defect area, sub-epithelial nerve fiber density, corneal sensitivity, rhNGF contents in resident AM and corneas were measured after the surgery. rhNGF was sustained release from the AM within 14d in vitro, with the positive correlation with initial immersion concentration. The immersion of AM in 500 µg/mL rhNGF for 30min achieved the most stable release within 14d. After transplantation in rabbit cornea, a high concentration of rhNGF in resident rhNGF-AM and cornea was maintained within 8d. Corneal epithelial healing, nerve fiber regeneration and the recovery of corneal sensitivity were significantly accelerated after the rhNGF-AM transplantation when compared to simple AM transplantation (all P<0.05). Simple immersion of AM achieves the sustained release of rhNGF, and promotes corneal epithelial wound healing and nerve regeneration, as well as the recovery of corneal sensitivity in rabbit.

Application of Human Epineural Conduit Supported with Human Mesenchymal Stem Cells as a Novel Therapy for Enhancement of Nerve Gap Regeneration

Various therapeutic methods have been suggested to enhance nerve regeneration. In this study, we propose a novel approach for enhancement of nerve gap regeneration by applying human epineural conduit (hEC) supported with human mesenchymal stem cells (hMSC), as an alternative to autograft repair. Restoration of 20 mm sciatic nerve defect with hEC created from human sciatic nerve supported with hMSC was tested in 4 experimental groups (n = 6 each) in the athymic nude rat model (Crl:NIH-Foxn1rnu): 1 - No repair control, 2 - Autograft control, 3 - Matched diameter hEC filled with 1 mL saline, 4 - Matched diameter hEC supported with 3 × 106 hMSC. Assessments included: functional tests: toe-spread and pinprick, regeneration assessment by immunofluorescence staining: HLA-1, HLA-DR, NGF, GFAP, Laminin B, S-100, VEGF, vWF and PKH26 labeling; histomorphometric analysis of myelin thickness, axonal density, fiber diameter and myelinated nerve fibers percentage; Gastrocnemius Muscle Index (GMI) and muscle fiber area ratio. Best sensory and motor function recovery, as well as GMI and muscle fiber area ratio, were observed in the autograft group, and were comparable to the hEC with hMSC group (p = 0.038). Significant improvements of myelin thickness (p = 0.003), fiber diameter (p = 0.0296), and percentage of myelinated fibers (p < 0.0001) were detected in hEC group supported with hMSC compared to hEC with saline controls. At 12-weeks after nerve gap repair, hEC combined with hMSC revealed increased expression of neurotrophic and proangiogenic factors, which corresponded with improvement of function comparable with the autograft control. Application of our novel hEC supported with hMSC provides a potential alternative to the autograft nerve repair.Graphical

Phase 1b Randomized Controlled Study of Short Course Topical Recombinant Human Nerve Growth Factor (rhNGF) for Neuroenhancement in Glaucoma: Safety, Tolerability, and Efficacy Measure Outcomes

No approved therapies directly target retinal ganglion cells (RGCs) for neuroprotection or neuroenhancement in glaucoma. Recombinant human nerve growth factor (rhNGF) has been shown to promote RGC survival and function in animal models of optic neuropathy. Here we evaluate the safety, tolerability, and efficacy of short-term, high-dose rhNGF eye drops versus placebo in a cohort of glaucoma patients. This was a prospective, phase 1b, single-center, randomized, double-masked, vehicle-controlled, parallel-group study. This study was designed to assess safety and tolerability as well as short-term neuroenhancement of structure and function (clinicaltrials.gov NCT02855450). A total of 60 open-angle glaucoma patients were randomized 40:20 to receive either 180 μg/mL rhNGF or vehicle control eye drops in both eyes, 3 times daily for 8 weeks, with a 24-week post-treatment follow-up. One eye was officially selected as the study eye, although both eyes were studied and dosed. Primary endpoints were safety, as assessed by adverse events, and tolerability, as assessed by patient-reported outcomes. Secondary outcome measures included best corrected visual acuity (BCVA), Humphrey visual field, electroretinograpy (ERG), and optical coherence tomography (OCT) of retinal nerve fiber layer (RNFL) thickness at baseline, after 8 weeks of treatment, and at 4 and 24 weeks after treatment (12 and 32 weeks total). Of the 60 randomized patients, 23 were female (38%) and the average age was 66.1 years. Through week 32, there were no treatment-related serious adverse events, including no unexpectedly severe progression of optic neuropathy, no adverse events affecting ocular function or pressure, and no drug-related systemic toxicity. Topical high-dose rhNGF was tolerated well, with a low level of symptom burden mainly eliciting periocular ache (in 52% of treated group and 5% of placebo group) and only 3 patients (7.5%) discontinuing treatment because of discomfort, of whom 1 patient (2.5%) prematurely withdrew from the study. There were no statistically significant differences in global indices of Humphrey visual field and no meaningful differences in total, quadrant, or clock-hour mean RNFL thickness between the groups, although both of these function and structure measures showed nonsignificant trends toward significance in favor of rhNGF. Real-world participant data was used to generate an estimate of cohort size needed to power subsequent studies. Use of rhNGF is safe and tolerable in a topical 180-μg/mL formulation. Although no statistically significant short-term neuroenhancement was detected in this trial, given the strong effects of NGF in preclinical models and the trends detected in this study, analysis for efficacy in a neuroprotection trial is warranted. NOTE: Publication of this article is sponsored by the American Ophthalmological Society.

Comparative study of decellularization techniques to obtain natural extracellular matrix scaffolds of human peripheral-nerve allografts.

We hypothesize that adding sonication cycles to the process of decellularization of cadaveric human peripheral nerves will increase the removal of cell debris and myelin sheath, increasing their utility as allografts. Our aim of this study was to develop a decellularization protocol that allows the removal of cells and myelin sheath without detrimental effects on nerve architecture. Segments of ulnar and median nerves from human donors, isolated both before and after cardiac arrest, were subjected to two methods of decellularization: two-detergent-based (M1) and the same method with sonication added (M2). We evaluated the histology of unprocessed and decellularized nerves (n = 24 per group) for general morphology, presence of cell nuclei, nuclear remnants, collagen fibers, and myelin. We performed immunohistochemistry to verify the removal of Schwann cells associated with histomorphometry. We used scanning electron microscopy (EM) to evaluate the ultrastructure of both native and decellularized nerves. The efficacy of decellularization was assessed by analysis of genomic DNA. Histology confirmed that both decellularization protocols were adequate and maintained natural nerve architecture. Scanning EM showed that 3D ultrastructural architecture also was maintained. Histomorphometric parameters showed a more complete removal of the myelin with the M2 protocol than with M1 (p = 0.009). Fiber diameter and density were not modified by decellularization methods. Sonication can be a complementary method to decellularization of peripheral nerve allografts with sonication increasing the effectiveness of detergent-based protocols for the removal of unwanted cellular components from peripheral nerve allografts.

Role of NaV 1.7 in action potential conduction along human bronchial vagal afferent C-fibres.

The purpose of this study was to determine the role of NaV 1.7 in action potential conduction in C-fibres in the bronchial branches of the human vagus nerve. Bronchial branches of the vagus nerve were dissected from human donor tissue. The C-wave of the electrically evoked compound action potential was quantified in the absence and presence of increasing concentrations of the selective NaV 1.7 blocking drugs, PF-05089771 and ST-2262, as well as the NaV 1.1, 1.2, and 1.3 blocking drug ICA121-431. The efficacy and potency of these inhibitors were compared to the standard NaV 1 blocker, tetrodotoxin. We then compared the relative potencies of the NaV 1 blockers in inhibiting the C-wave of the compound action potential, with their ability to inhibit parasympathetic cholinergic contraction of human isolated bronchi, a response previously shown to be strictly dependent on NaV 1.7 channels. The selective NaV 1.7 blockers inhibited the C-wave of the compound action potential with potencies similar to that observed in the NaV 1.7 bronchial contractions assay. Using rt-PCR, we noted that NaV 1.7 mRNA was strongly expressed and transported down the vagus nerve bundles. NaV 1.7 blockers can prevent action potential conduction in the majority of vagal C-fibres arising from human bronchi. Blockers of NaV 1.7 channels may therefore have value in inhibiting the responses to excessive airway C-fibre activation in inflammatory airway disease, responses that include coughing as well as reflex bronchoconstriction and secretions.

A Novel Alaska Pollock Gelatin Sealant Shows Higher Bonding Strength and Nerve Regeneration Comparable to That of Fibrin Sealant in a Cadaveric Model and a Rat Model

A novel biocompatible sealant composed of Alaska pollock-derived gelatin (ApGltn) has recently shown good burst strength and biocompatibility in a porcine aorta. The purpose of this study was to investigate the bonding strength and biocompatibility of the ApGltn sealant in transected digital nerves of fresh frozen cadavers and in the sciatic nerves of a rat model. Eighty human digital nerves of fresh frozen cadavers were transected for biomechanical traction testing. They were treated with four surgical interventions: (1) suture plus ApGltn sealant; (2) suture; (3) ApGltn sealant; and (4) fibrin sealant. Forty-three sciatic nerves of male Wistar rats were used for functional and histopathologic evaluation. They were treated with six surgical interventions: (1) suture plus ApGltn sealant; (2) suture; (3) ApGltn sealant; (4) fibrin sealant; (5) resection with a 5-mm gap (10 rats per group); and (6) sham operation (three rats). Macroscopic confirmation, muscle weight measurement, and histopathologic findings including G-ratio were examined 8 weeks after the procedure. The maximum failure load of the ApGltn sealant was significantly higher than that of a fibrin sealant (0.22 ± 0.05 N versus 0.06 ± 0.04 N). The maximum failure load of the ApGltn sealant was significantly lower that of suture plus ApGltn sealant (1.37 N) and suture (1.27 N). Functional evaluation and histologic examination showed that sciatic nerves repaired with ApGltn sealant showed similar nerve recovery compared to repair with the suture and fibrin sealant. The ApGltn sealant showed higher bonding strength and equal effect of nerve regeneration when compared with the fibrin sealant.

Origin, branching pattern, foraminal and intraspinal distribution of the human lumbar sinuvertebral nerves

BACKGROUND CONTEXTThe lumbar sinuvertebral nerve (SVN) innervates the outer posterior intervertebral disc (IVD); it is thought to mediate discogenic low-back pain (LBP). Controversy, however, exists on its origins at higher (L1–L2) versus lower (L3–L5) lumbar levels. Additionally, lack of knowledge regarding its foraminal and intraspinal branching patterns and extensions may lead to iatrogenic damage. PURPOSETo systematically describe the origins of the L2 and L5 SVNs, their morphological variation in the intervertebral foramen (IVF) and intraspinal distribution. STUDY DESIGNDissection-based study of 20 SVNs with histological confirmation in five embalmed human cadavers. METHODSThe origin, branching pattern and distribution of the L2 and L5 SVNs was investigated bilaterally in five human cadavers using dorsal and anterolateral dissection approaches. Parameters studied included somatic and/or autonomic SVN root contributions, foraminal SVN morphology and course, diameter, branching point, intraspinal distribution and IVD innervation pattern. Nerve tissue was confirmed by immunostaining for neurofilament and S100 proteins. RESULTSThe SVN and its origins was identified in all except one IVF at L2 and in all foramina at L5. At L2, the SVN arose in nearly 90% of sides from both somatic and autonomic roots and at L5 in 40% of sides. The remaining SVNs were formed by purely autonomic roots. The SVN arose from significantly more roots at L2 than L5 (3.1 ± 0.3 vs. 1.9 ± 0.3, respectively; p=.022). Four different SVN morphologies could be discerned in the L2 IVF: single filament (22%), multiple (parallel or diverging) filament (33%), immediate splitting (22%) and plexiform (22%) types, whereas the L5 SVN consisted of single (90%) and multiple (10%) filament types. SVN filaments were significantly thicker at L2 than L5 (0.48 ± 0.06 mm vs. 0.33 ± 0.02 mm, respectively; p=.043). Ascending SVN filaments coursed roughly parallel to the exiting spinal nerve root trajectory at L2 and L5. Branching of the SVN into ascending and descending branches occurred mostly intraspinal both at L2 and L5. Spinal canal distribution was also similar for L2 and L5 SVNs. Lumbar posterior IVDs were innervated by the descending branch of the parent SVN and ascending branch of the subjacent SVN. CONCLUSIONSThe SVN at L2 originates from both somatic and autonomic roots in 90% of cases and at L5 in 40% of cases. The remaining SVNs are purely autonomic. In the IVF, the L2 SVN is morphologically heterogeneous, but generally consists of numerous filaments, whereas at L5 90% contains a single SVN filament. The L2 SVN is formed by more roots and is thicker than the L5 SVN. Intraspinal SVN distribution is confined to its level of origin; lumbar posterior IVDs are innervated by corresponding and subjacent SVNs (ie, two spinal levels). CLINICAL SIGNIFICANCEOur findings indicate that L5 discogenic LBP may be mediated both segmentally and nonsegmentally in 40% of cases and nonsegmentally in 60% of cases. Failure of lower lumbar discogenic pain treatment may be the result of only interrupting the nonsegmental pathway, but not the segmental one as well. Relating SVN anatomy to microsurgical spinal approaches may prevent iatrogenic damage to the SVN and the formation of postsurgical back pain.

Live Imaging of Primary Neurons in Long-Term Cryopreserved Human Nerve Tissue.

Tissue cryopreservation provides a convenient solution for tackling one of the major problems in neuroscience research, namely, the scarce availability of human nerve tissues, especially if needed alive. While brain tissue can be used only postmortem, live nerve tissue can reasonably well be harvested from the periphery. A valuable source of primary neurons is the intestine, which compared with brain has the advantage to be safely accessible via endoscopy. The nerve tissue innervating the intestine (the enteric nervous system; ENS) can be sampled with regular endoscopic biopsy forceps and remains viable for multiple physiological and immunohistochemical tests, as previously demonstrated. Here, we present a method to preserve, over longer periods of time, human primary neurons contained in these biopsies. The use of a cryoprotective agent and the application of controlled cooling revealed to be crucial to properly store the nerve tissue and to enable functional measurements after thawing. These primary neurons were evaluated for functionality (live imaging) and morphology (histology) up to one year after cryopreservation. Calcium (Ca2+) imaging indicated that human primary neurons remained viable and responded to selective stimulations (serotonergic and nicotinic agonists) after cryopreservation. Additionally, immunohistochemistry performed with specific neuronal markers showed that nerve structure and neuronal morphology were retained, with no signs of cellular damage. In this study, we demonstrate that the human ENS is a realistic source of primary neurons, which can be successfully preserved over long times and as such can be exploited both for gastrointestinal-specific as well as for general neuroscience research.

Editors' Note: Guillain-Barré Syndrome in the Placebo and Active Arms of a COVID-19 Vaccine Clinical Trial

In “Guillain-Barré Syndrome in the Placebo and Active Arms of a COVID-19 Vaccine Clinical Trial,” Márquez Loza et al. presented a patient who developed the Guillain-Barré syndrome (GBS) after being vaccinated in a COVID-19 vaccine clinical trial and highlighted the fact that this should not be considered a postvaccination complication, given that, by chance alone, 900–2,200 people can be expected to develop GBS within 6 weeks of a 1-dose vaccine and 1,500–3,700 people can be expected to develop GBS within 10 weeks of a 2-dose vaccine. Willer comments that although vaccines can increase the risk of GBS because of antibody production, they can also decrease the risk of GBS because of infection prevention. On behalf of the authors, Amato agrees that vaccines can reduce the risk of postinfection GBS in general but notes that a large epidemiologic cohort study found no causal relationship between COVID-19 and GBS and no evidence of molecular mimicry between any SARS-CoV-2 proteins and axonal or myelin proteins in human nerves. Amato recommends performance of large-scale epidemiologic studies and meta-analyses to better understand the relationship between COVID-19 vaccination and GBS. In “Guillain-Barré Syndrome in the Placebo and Active Arms of a COVID-19 Vaccine Clinical Trial,” Márquez Loza et al. presented a patient who developed the Guillain-Barré syndrome (GBS) after being vaccinated in a COVID-19 vaccine clinical trial and highlighted the fact that this should not be considered a postvaccination complication, given that, by chance alone, 900–2,200 people can be expected to develop GBS within 6 weeks of a 1-dose vaccine and 1,500–3,700 people can be expected to develop GBS within 10 weeks of a 2-dose vaccine. Willer comments that although vaccines can increase the risk of GBS because of antibody production, they can also decrease the risk of GBS because of infection prevention. On behalf of the authors, Amato agrees that vaccines can reduce the risk of postinfection GBS in general but notes that a large epidemiologic cohort study found no causal relationship between COVID-19 and GBS and no evidence of molecular mimicry between any SARS-CoV-2 proteins and axonal or myelin proteins in human nerves. Amato recommends performance of large-scale epidemiologic studies and meta-analyses to better understand the relationship between COVID-19 vaccination and GBS.

Author Response: Guillain-Barré Syndrome in the Placebo and Active Arms of a COVID-19 Vaccine Clinical Trial.

We thank Dr. Willer for his interest in our case report.1 We agree that vaccines can reduce the risk of Guillain-Barré syndrome (GBS) by reducing infection, but this generally assumes that the specific infection that the vaccine targets also increases the risk of GBS.2 However, as mentioned in our article, a large epidemiological-cohort study from Great Britain found no evidence for causality between COVID-19 and GBS.3 A complicating factor is the reduced incidence of GBS during the pandemic that may be attributed to social distancing, wearing masks, and better hygiene. Nonetheless, GBS and COVID-19 incidences vary between regions and do not correlate with one another. These authors also found no evidence of molecular mimicry between any SARS-CoV-2 proteins and human nerve axonal or myelin proteins that might implicate molecular mimicry. Furthermore, not all vaccines cause GBS. Standard epidemiologic methods were used to identify the rare risk of GBS with other vaccines—such as H1N1—and will be needed to ascertain if there is a risk present for the different available COVID-19 vaccinations.