Neurofilament Proteins as Biomarkers to Monitor Neurological Diseases and the Efficacy of Therapies

Blood diagnostic and prognostic biomarkers in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a devastating neurodegenerative disease for which the current treatment approaches remain severely limited. The principal pathological alterations of the disease include the selective degeneration of motor neurons in the brain, brainstem, and spinal cord, as well as abnormal protein deposition in the cytoplasm of neurons and glial cells. The biological markers under extensive scrutiny are predominantly located in the cerebrospinal fluid, blood, and even urine. Among these biomarkers, neurofilament proteins and glial fibrillary acidic protein most accurately reflect the pathologic changes in the central nervous system, while creatinine and creatine kinase mainly indicate pathological alterations in the peripheral nerves and muscles. Neurofilament light chain levels serve as an indicator of neuronal axonal injury that remain stable throughout disease progression and are a promising diagnostic and prognostic biomarker with high specificity and sensitivity. However, there are challenges in using neurofilament light chain to differentiate amyotrophic lateral sclerosis from other central nervous system diseases with axonal injury. Glial fibrillary acidic protein predominantly reflects the degree of neuronal demyelination and is linked to non-motor symptoms of amyotrophic lateral sclerosis such as cognitive impairment, oxygen saturation, and the glomerular filtration rate. TAR DNA-binding protein 43, a pathological protein associated with amyotrophic lateral sclerosis, is emerging as a promising biomarker, particularly with advancements in exosome-related research. Evidence is currently lacking for the value of creatinine and creatine kinase as diagnostic markers; however, they show potential in predicting disease prognosis. Despite the vigorous progress made in the identification of amyotrophic lateral sclerosis biomarkers in recent years, the quest for definitive diagnostic and prognostic biomarkers remains a formidable challenge. This review summarizes the latest research achievements concerning blood biomarkers in amyotrophic lateral sclerosis that can provide a more direct basis for the differential diagnosis and prognostic assessment of the disease beyond a reliance on clinical manifestations and electromyography findings.

Alternating hemiplegia of childhood associated mutations in Atp1a3 reveal diverse neurological alterations in mice

Pathogenic variants in the neuronal Na+/K+ ATPase transmembrane ion transporter (ATP1A3) cause a spectrum of neurological disorders including alternating hemiplegia of childhood (AHC). The most common de novo pathogenic variants in AHC are p.D801N (∼40 % of patients) and p.E815K (∼25 % of patients), which lead to early mortality by spontaneous death in mice. Nevertheless, knowledge of the development of clinically relevant neurological phenotypes without the obstacle of premature death, is critical for the identification of pathophysiological mechanisms and ultimately, for the testing of therapeutic strategies in disease models. Here, we used hybrid vigor attempting to mitigate the fragility of AHC mice and then performed behavioral, electrophysiological, biochemical, and molecular testing to comparatively analyze mice that carry either of the two most common AHC patient observed variants in the Atp1a3 gene. Collectively, our data reveal the presence but also the differential impact of the p.D801N and p.E815K variants on disease relevant alterations such as spontaneous and stress-induced paroxysmal episodes, motor function, behavioral and neurophysiological activity, and neuroinflammation. Our alternate AHC mouse models with their phenotypic deficits open novel avenues for the investigation of disease biology and therapeutic testing for ATP1A3 research.

Effect of deep brain stimulation for lateral hypothalamic area on memory decline and hippocampal neurofilaments expression dysfunctions in aged rats

OBJECTIVE

Studying the effect of deep brain stimulation (DBS) in the lateral hypothalamic area (LHA) in young and aging rats regarding memory changes, hippocampal neuronal dystrophy, and neurofilament expression.

METHODS

Thirty-six male Sprague-Dawley rats were divided into two main groups: adult young ( n  = 18, 8 weeks old) and aged ( n  = 18, 24 months old). Each main group was further subdivided into three equal subgroups ( n  = 6) including control, sham, and DBS. DBS of LHA was conducted using high-frequency electric currents (130 Hz) for 1.5 h with 5-min breaks every 30 min for five consecutive days. Assessment of working memory was done using passive avoidance test (PAT). Then, the brain was dissected and hippocampal neuronal dystrophic damage was assessed as well as immunohistochemical examination of neurofilaments (NF68, NF200) expression.

RESULTS

Aging rats had progressive hippocampal neuronal degeneration and downregulation of heavy and light chain neurofilaments, that was associated with progressive decline in working memory. Nevertheless, activation of DBS in the LHA enhanced memory function as it increased latency to entry in PAT ( P  < 0.001) compared to old normal and sham groups. Dystrophic damage score significantly decreased with DBS ( P  < 0.001) in the hippocampal CA1, CA3, and dentate gyrus regions. Moreover, DBS upregulated hippocampal NF68, NF200 expression ( P  < 0.001) in both young and old rats. We also found a significant positive correlation between working memory and NFs expression and a negative correlation between dystrophic damage score and NFs expression.

CONCLUSIONS

DBS in the LHA may have a neuroprotective effect in aging rats as it enhanced the working memory and decreased hippocampal neuronal dystrophy. This protective effect may be caused by the upregulation of neurofilaments.

Potential Correlation Between Molecular Biomarkers and Oxidative Stress in Traumatic Brain Injury

Diagnosing traumatic brain injury (TBI) remains challenging due to an incomplete understanding of its neuropathological mechanisms. TBI is recognised as a complex condition involving both primary and secondary injuries. Although oxidative stress is a non-specific molecular phenomenon observed in various neuropathological conditions, it plays a crucial role in brain injury response and recovery. Due to these aspects, we aimed to evaluate the interaction between some known TBI molecular biomarkers and oxidative stress in providing evidence for its possible relevance in clinical diagnosis and outcome prediction. We found that while many of the currently validated molecular biomarkers interact with oxidative pathways, their patterns of variation could assist the diagnosis, prognosis, and outcomes prediction in TBI cases.

Role of Antioxidants in Modulating the Microbiota-Gut-Brain Axis and Their Impact on Neurodegenerative Diseases

This narrative review presents the role of antioxidants in regulating the gut microbiota and the impact on the gut-brain axis, with a particular focus on neurodegenerative diseases, such as Alzheimer's (AD) and Parkinson's disease (PD). These diseases are characterised by cognitive decline, motor dysfunction, and neuroinflammation, all of which are significantly exacerbated by oxidative stress. This review elucidates the contribution of oxidative damage to disease progression and explores the potential of antioxidants to mitigate these pathological processes through modulation of the gut microbiota and associated pathways. Based on recent studies retrieved from reputable databases, including PubMed, Web of Science, and Scopus, this article outlines the mechanisms by which antioxidants influence gut health and exert neuroprotective effects. Specifically, it discusses how antioxidants, including polyphenols, vitamins, and flavonoids, contribute to the reduction in reactive oxygen species (ROS) production and neuroinflammation, thereby promoting neuronal survival and minimising oxidative damage in the brain. In addition, the article explores the role of antioxidants in modulating key molecular pathways involved in oxidative stress and neuroinflammation, such as the NF-κB, Nrf2, MAPK, and PI3K/AKT pathways, which regulate ROS generation, inflammatory cytokine expression, and antioxidant responses essential for maintaining cellular homeostasis in both the gut and the central nervous system. In addition, this review explores the complex relationship between gut-derived metabolites, oxidative stress, and neurodegenerative diseases, highlighting how dysbiosis-an imbalance in the gut microbiota-can exacerbate oxidative stress and contribute to neuroinflammation, thereby accelerating the progression of such diseases as AD and PD. The review also examines the role of short-chain fatty acids (SCFAs) produced by beneficial gut bacteria in modulating these pathways to attenuate neuroinflammation and oxidative damage. Furthermore, the article explores the therapeutic potential of microbiota-targeted interventions, including antioxidant delivery by probiotics and prebiotics, as innovative strategies to restore microbial homeostasis and support brain health. By synthesising current knowledge on the interplay between antioxidants, the gut-brain axis, and the molecular mechanisms underlying neurodegeneration, this review highlights the therapeutic promise of antioxidant-based interventions in mitigating oxidative stress and neurodegenerative disease progression. It also highlights the need for further research into antioxidant-rich dietary strategies and microbiota-focused therapies as promising avenues for the prevention and treatment of neurodegenerative diseases.

Basic Pathological Mechanisms in Peripheral Nerve Diseases

Pathological changes and the cellular and molecular mechanisms underlying axonopathy and myelinopathy are key to understanding a wide range of inherited and acquired peripheral nerve disorders. While the clinical indications for nerve biopsy have diminished over time, its diagnostic value remains significant in select conditions, offering a unique window into the pathophysiological processes of peripheral neuropathies. Evidence highlights the symbiotic relationship between axons and myelinating Schwann cells, wherein disruptions in axo-glial interactions contribute to neuropathogenesis. This review synthesizes recent insights into the pathological and molecular underpinnings of axonopathy and myelinopathy. Axonopathy encompasses Wallerian degeneration, axonal atrophy, and dystrophy. Although extensively studied in traumatic nerve injury, the mechanisms of axonal degeneration and Schwann cell-mediated repair are increasingly recognized as pivotal in non-traumatic disorders, including dying-back neuropathies. We briefly outline key transcription factors, signaling pathways, and epigenetic changes driving axonal regeneration. For myelinopathy, we discuss primary segmental demyelination and dysmyelination, characterized by defective myelin development. We describe paranodal demyelination in light of recent findings in nodopathies, emphasizing that it is not an exclusive indicator of demyelinating disorders. This comprehensive review provides a framework to enhance our understanding of peripheral nerve pathology and its implications for developing targeted therapies.

DNA origami signal amplification in lateral flow immunoassays

Lateral flow immunoassays (LFIAs) enable a rapid detection of analytes in a simple, paper-based test format. Despite their multiple advantages, such as low cost and ease of use, their low sensitivity compared to laboratory-based testing limits their use in e.g. many critical point-of-care applications. Here, we present a DNA origami-based signal amplification technology for LFIAs. DNA origami is used as a molecularly precise adapter to connect detection antibodies to tailored numbers of signal-generating labels. As a proof of concept, we apply the DNA origami signal amplification in a sandwich-based LFIA for the detection of cardiac troponin I (cTnI) in human serum. We show a 55-fold improvement of the assay sensitivity with 40-nm gold nanoparticle labels and an adjustable signal amplification of up to 125-fold with fluorescent dyes. The technology is compatible with a wide range of existing analytes, labels, and sample matrices, and presents a modular approach for improving the sensitivity and reliability of lateral flow testing.

Novel insights into the molecular nature of neurofilament light polypeptide species in cerebrospinal fluid

The quantification of neurofilament light polypeptide (NFL) in biofluids is being clinically used to detect and grade general neuronal damage in neurodegenerative diseases and quantify neuronal injury during acute events like traumatic brain injury. Specific assays that target only particular molecular breakdown products of neurofilaments have the potential to distinguish between various pathologies. Nevertheless, the molecular structure of neurofilament light polypeptide in cerebrospinal fluid remains to be elucidated. We characterized neurofilament light polypeptide in cerebrospinal fluid by size-exclusion chromatography, Western blotting and mass spectrometry. Neurofilament light polypeptide in cerebrospinal fluid was found to be composed of aggregates of fragments of the full-length molecule. These aggregates were sensitive to reduction by dithiothreitol and dissociated to monomeric fragments of 6-12 kDa (Western blot), covering most of the coiled-coil domains of neurofilament light polypeptide. Since only cysteine residues can form disulfide bonds, this points to a role of the single cysteine 322 for maintaining the stability of the aggregates. The sequence region covered by the identified fragments ended just a few amino acids C-terminally of the coiled-coil region at a site which had been previously mapped to a calpain cleavage site in the glial fibrillary acidic protein, which is highly homologous to neurofilament light polypeptide in the coiled-coil region. This cleavage site was also confirmed to be present in bovine neurofilament light polypeptide by in vitro digestion of purified neurofilament light polypeptide with calpain-1. The difference of the molecular weights of the reduced and non-reduced forms of neurofilament light polypeptide suggests that neurofilament light polypeptide in CSF consists of disulfide-linked aggregated fragments, most likely tetramers, or alternately dimers in a complex with another binding partner.

An Improved Method for Sampling and Quantitative Protein Analytics of Cerebrospinal Fluid of Individual Mice

The mouse is the species most commonly used in preclinical research, but protein analytics of murine cerebrospinal fluid (CSF) remains challenging because of low sample volumes (often <10 μl) and frequent contaminations with blood. We developed an improved CSF sampling method that allows routine collection of larger volumes (20-30 μl) of pure CSF from individual mice, enabling multiple protein analytical assays from a single sample. Based on cell counts and hemoglobin ELISAs, we provide an easy quality control workflow for obtaining cell- and blood-free murine CSF. Through mass spectrometry-based proteomics using an absolutely quantified external standard, we estimated concentrations for hundreds of mouse CSF proteins. While repeated CSF sampling from the same mouse was possible, it induced CSF proteome changes. Applying the improved method, we found that the mouse CSF proteome remains largely stable over time in wild-type mice, but that amyloid pathology in the 5xFAD mouse model of Alzheimer's disease massively changes the CSF proteome. Neurofilament light chain and TREM2, markers of neurodegeneration and activated microglia, respectively, were strongly upregulated and validated using immunoassays. In conclusion, our refined murine CSF collection method overcomes previous limitations, allowing multiple quantitative protein analyses for applications in biomedicine.

Secreted neurofilament light chain after neuronal damage induces myeloid cell activation and neuroinflammation

Neurofilament light chain (NfL) is a neuron-specific cytoskeletal protein that provides structural support for axons and is released into the extracellular space following neuronal injury. While NfL has been extensively studied as a disease biomarker, the underlying release mechanisms and role in neurodegeneration remain poorly understood. Here, we find that neurons secrete low baseline levels of NfL, while neuronal damage triggers calpain-driven proteolysis and release of fragmented NfL. Secreted NfL activates microglial cells, which can be blocked with anti-NfL antibodies. We utilize in vivo single-cell RNA sequencing to profile brain cells after injection of recombinant NfL into the mouse hippocampus and find robust macrophage and microglial responses. Consistently, NfL knockout mice ameliorate microgliosis and delay symptom onset in the SOD1 mouse model of amyotrophic lateral sclerosis (ALS). Our results show that released NfL can activate myeloid cells in the brain and is, thus, a potential therapeutic target for neurodegenerative diseases.

Alzheimer's disease neuropathology and its estimation with fluid and imaging biomarkers

Alzheimer's disease (AD) is neuropathologically characterized by the extracellular deposition of the amyloid-β peptide (Aβ) and the intraneuronal accumulation of abnormal phosphorylated tau (τ)-protein (p-τ). Most frequently, these hallmark lesions are accompanied by other co-pathologies in the brain that may contribute to cognitive impairment, such as vascular lesions, intraneuronal accumulation of phosphorylated transactive-response DNA-binding protein 43 (TDP-43), and/or α-synuclein (αSyn) aggregates. To estimate the extent of these AD and co-pathologies in patients, several biomarkers have been developed. Specific tracers target and visualize Aβ plaques, p-τ and αSyn pathology or inflammation by positron emission tomography. In addition to these imaging biomarkers, cerebrospinal fluid, and blood-based biomarker assays reflecting AD-specific or non-specific processes are either already in clinical use or in development. In this review, we will introduce the pathological lesions of the AD brain, the related biomarkers, and discuss to what extent the respective biomarkers estimate the pathology determined at post-mortem histopathological analysis. It became evident that initial stages of Aβ plaque and p-τ pathology are not detected with the currently available biomarkers. Interestingly, p-τ pathology precedes Aβ deposition, especially in the beginning of the disease when biomarkers are unable to detect it. Later, Aβ takes the lead and accelerates p-τ pathology, fitting well with the known evolution of biomarker measures over time. Some co-pathologies still lack clinically established biomarkers today, such as TDP-43 pathology or cortical microinfarcts. In summary, specific biomarkers for AD-related pathologies allow accurate clinical diagnosis of AD based on pathobiological parameters. Although current biomarkers are excellent measures for the respective pathologies, they fail to detect initial stages of the disease for which post-mortem analysis of the brain is still required. Accordingly, neuropathological studies remain essential to understand disease development especially in early stages. Moreover, there is an urgent need for biomarkers reflecting co-pathologies, such as limbic predominant, age-related TDP-43 encephalopathy-related pathology, which is known to modify the disease by interacting with p-τ. Novel biomarker approaches such as extracellular vesicle-based assays and cryptic RNA/peptides may help to better detect these co-pathologies in the future.

Neurofilaments as Prognostic Biomarkers in the Assessment of the Risk of Advanced Taxane-Induced Neuropathy in Breast Cancer Patients-A Pilot Study

OBJECTIVES

The aim of the present study was to assess the clinical value of measuring the concentration of neurofilament light chains (NF-Ls) in the diagnosis of taxane-induced neuropathy (CIPN) during neoadjuvant chemotherapy (NAC) in breast cancer patients.

METHODS

This study included a total of 94 patients who qualified for NAC with taxanes. Serum samples were collected before starting NAC, after three and six cycles, and 3-6 months after NAC. The NF-L concentration was determined using the Ella technology. The assessment of CIPN was based on the clinical symptoms included in the EORTC QLQ-CIPN20 scores.

RESULTS

The median NF-L concentrations increased during NAT monitoring. After the end of therapy, a significant decrease in NF-L concentrations was observed (p = 0.001, R = 0.37). We established a cut-off point of 29.5 pg/mL to distinguish between the control group and patients with early symptoms of neuropathy (CIPN G1) (p = 0.001; AUC = 0.982). We showed that NF-L concentrations, regardless of the stage of therapy, increased with the severity of neuropathy symptoms (CIPG1 vs. G2 vs. G3) (p = 0.0189, R = 0.33). According to the established cut-off points, serum NF-L concentrations above 196 pg/mL in patients undergoing therapy likely indicate the presence of low-grade neuropathy (p = 0.0076), while values above 218 pg/mL may indicate advanced CIPN (p = 0.0008).

CONCLUSIONS

In this study, we demonstrated the usefulness of NF-L levels to confirm neuropathy early in the course of treatment, which is important as the questionnaire-based assessment of neuropathy currently used in practice remains subjective. Ultimately, serum NF-L levels are helpful in determining the severity of NAC-induced neuropathy among breast cancer patients.

Neuroinflammation causes mitral cell dysfunction and olfactory impairment in a multiple sclerosis model

BACKGROUND

Olfactory dysfunction is an underestimated symptom in multiple sclerosis (MS). Here, we examined the pathogenic mechanisms underlying inflammation-induced dysfunction of the olfactory bulb using the animal model of MS, experimental autoimmune encephalomyelitis (EAE).

RESULTS

Reduced olfactory function in EAE was associated with the degeneration of short-axon neurons, immature neurons, and both mitral and tufted cells, along with their synaptic interactions and axonal repertoire. To dissect the mechanisms underlying the susceptibility of mitral cells, the main projection neurons of the olfactory bulb, we profiled their responses to neuroinflammation by single-nucleus RNA sequencing followed by functional validation. Neuroinflammation resulted in the induction of potassium channel transcripts in mitral cells, which was reflected in increased halothane-induced outward currents of these cells, likely contributing to the impaired olfaction in EAE animals.

CONCLUSION

This study reveals the crucial role of mitral cells and their potassium channel activity in the olfactory bulb during EAE, thereby enhancing our understanding of neuroinflammation-induced neurodegeneration in MS.

Long-Term Clinical and Biological Prognostic Factors of Anti-NMDA Receptor Encephalitis in Children

BACKGROUND AND OBJECTIVES

Anti-NMDAR encephalitis (NMDARE) is a severe neurologic condition, and recently, the NMDAR Encephalitis One-Year Functional Status (NEOS) score has emerged as a 1-year prognostic tool. This study aimed to evaluate NEOS score and biomarker (neurofilament light chains [NfL], total-Tau protein, glial fibrillary acidic protein, and serum cytokines) correlation with modified Rankin Scale (mRS), cognitive impairment, and clinical recovery in pediatric NMDARE over 2 years.

METHODS

In this French multicenter observational study, 104 pediatric patients with NMDARE were followed for a minimum of 2 years. Clinical data and serum/plasma samples were collected. Biomarker levels, measured using electroluminescence mesoscale discovery (MSD) S-PLEX, were compared between patients and controls and assessed for correlations with disease activity, mRS, cognitive/language impairment, and recovery status at 2 years.

RESULTS

At a median follow-up of 39.5 months, 68 percent of patients had unfavorable recovery and 54% had significant cognitive impairment. Both outcomes were strongly associated with younger age at diagnosis (OR 6.10 [1.91-27.3] p < 0.01 and 5.69 [1.46-27.7] p = 0.02, respectively). A higher NEOS score was significantly correlated with increased cognitive impairment (OR 2.53 [1.52-4.21], p < 0.001), higher mRS scores (OR 2.12 [1.34-3.57], p < 0.01), and unfavorable recovery at 2 years (OR 2.00 [1.30-3.06], p = 0.015). Elevated NfL levels were significantly associated with unfavorable recovery (OR 3.62 [1.29-10.9] p = 0.012) and severe cognitive impairment (OR 3.77 [1.38-10.9] p = 0.012) at 2 years. The combined area under the curve (AUC) for NfL and NEOS was significantly higher than the AUCs of NEOS and NfL alone (p = 0.01).

DISCUSSION

The NEOS score strongly predicts long-term outcomes in NMDARE, with its predictive value extending beyond the first-year mR prediction. NfL levels at disease onset seem to improve accuracy in predicting poor outcomes, providing valuable information for treatment decisions and future clinical trials.

An Update of Salivary Biomarkers for the Diagnosis of Alzheimer's Disease

Alzheimer's disease (AD) is characterized by progressive cognition and behavior impairments. Diagnosing AD early is important for clinicians to slow down AD progression and preserve brain function. Biomarkers such as tau protein and amyloid-β peptide (Aβ) are used to aid diagnosis as clinical diagnosis often lags. Additionally, biomarkers can be used to monitor AD status and evaluate AD treatment. Clinicians detect these AD biomarkers in the brain using positron emission tomography/computed tomography or in the cerebrospinal fluid using a lumbar puncture. However, these methods are expensive and invasive. In contrast, saliva collection is simple, inexpensive, non-invasive, stress-free, and repeatable. Moreover, damage to the brain parenchyma can impact the oral cavity and some pathogenic molecules could travel back and forth from the brain to the mouth. This has prompted researchers to explore biomarkers in the saliva. Therefore, this study provides an overview of the main finding of salivary biomarkers for AD diagnosis. Based on these available studies, Aβ, tau, cholinesterase enzyme activity, lactoferrin, melatonin, cortisol, proteomics, metabolomics, exosomes, and the microbiome were changed in AD patients' saliva when compared to controls. However, well-designed studies are essential to confirm the reliability and validity of these biomarkers in diagnosing and monitoring AD.

Association between serum neurofilament light chains and Life's Essential 8: A cross-sectional analysis

BACKGROUND AND AIM

Serum neurofilament light chain (sNfL), a protein released into the bloodstream post-neuronal axonal damage, has been validated as a robust biomarker for a range of neurological and systemic diseases. Concurrently, Life's Essential 8 (LE8) comprises a holistic suite of health behaviors and metabolic markers that are essential for assessing and enhancing cardiovascular health. Nevertheless, the interrelation between LE8 and sNfL is not yet fully elucidated. This investigation seeks to evaluate the association between LE8 and sNfL within the framework of the National Health and Nutrition Examination Survey (NHANES).

METHODS

According to data from the 2013-2014 NHANES, the study enrolled a total of 5262 participants aged between 20 and 75 years. We excluded 3035 individuals lacking sNfL measurements, included 2071 subjects for analysis, and further excluded cases from LE8 due to missing data. Ultimately, 1691 valid datasets were obtained. Hierarchical and multiple regression analyses were conducted, supplemented by smooth curve fitting and saturation effect analysis to investigate the relationship between LE8 and sNfL.

RESULTS

An inverse correlation was observed between LE8 scores and sNfL levels. For each SD change increase in LE8, log-transformed sNfL levels decreased by 0.14 (-0.17, -0.11 in the non-adjusted model), 0.08 (-0.10, -0.05 in the minimally adjusted model), and 0.08 (-0.12, -0.05 in the fully adjusted model). The multi-factor adjusted β coefficients and 95% confidence intervals (CIs) for LE8 categories (<50, 50 ~ 80, and ≥80) were as follows: reference, -0.20 (-0.34, -0.06), and -0.26 (-0.42, -0.10). The inflection point was determined to be 58.12, identified using a two-piece linear regression model.

CONCLUSION

The analysis indicated a non-linear relationship between LE8 scores and sNfL levels. Associations were noted a positive association between LE8 and sNfL. These results suggest that lifestyle modifications and optimization of metabolic markers could potentially correlate with reduced sNfL levels; further investigation is necessary to confirm a causal relationship.

Body Fluid Biomarkers of Neurological Injury in HIV-1-Associated Neurocognitive Disorder

Since combined antiretroviral therapy for human immunodeficiency virus-associated neurocognitive dysfunction (HAND) only slows the disease's progression, early identification and timely intervention are crucial for effective therapy. In this article, we review the latest evidence in body fluid biomarkers of HAND, providing an overview of research conducted on cerebrospinal fluid and blood samples to draw conclusions on promising biomarkers. Although the significance of biomarkers such as amyloid metabolites, tau proteins, neurofilament light chain, myelin oligodendrocyte glycoprotein, and brain-derived neurotrophic factor in the early detection of HAND may not be immediately clear, they could potentially play a crucial role in evaluating prognosis and tracking the effectiveness of treatment.

Novel Nose-to-brain delivery of carbenoxolone via mucoadhesive solid lipid nanoparticles for Parkinson's symptoms management: In vitro and in vivo evaluation in a rotenone-induced rat model

Parkinson's disease (PD) is a debilitating neurodegenerative disorder characterized by motor and non-motor symptoms, with limited effective treatment options. This study proposes a novel approach utilizing intranasal delivery of carbenoxolone (CBX) via chitosan-coated solid lipid nanoparticles (CS-coated SLNs) to manage PD symptoms by enhancing CBX delivery and brain targeting. Formulated CS-coated SLNs exhibited favorable quality attributes including particle size (164 ± 0.12 nm), surface charge (18 ± 0.89 mV), high entrapment efficiency (97.98 ± 0.98 %), and sustained drug release profile. In vivo evaluations in a rotenone-induced rat model of PD involved intranasal administration of CBX suspension and CBX-loaded CS-coated SLN (equivalent to 20 mg/kg/day) over four weeks. The CBX nano-formulation group showed significant improvements in motor function, coordination, and balance, as well as modulation of neurotransmitter levels, with increased dopamine and decreased α-synuclein levels compared to the control group. Moreover, the CBX nano-formulation exhibited superior efficacy in reducing neuroinflammation, oxidative stress, and apoptosis markers. Histological examination revealed restored neuronal architecture, suggesting potential neuroprotective effects. In conclusion, mucoadhesive chitosan-coated SLNs offer a promising nasal delivery system overcoming brain drug delivery obstacles facing CBX therapy in PD, paving the way to the development of novel treatments and improved quality of life for PD patients.

Evaluation of Serum and Aqueous Humor Neurofilament Light Chain as Markers of Neurodegeneration in Glaucoma

Purpose

The purpose of this study was to evaluate the relationship between serum and aqueous humor (AH) neurofilament light chain (NfL) and to determine whether serum NfL is elevated in patients undergoing ocular surgery who have glaucoma compared with those who do not.

Methods

In this single-center, case-control study, we enrolled patients with various types and stages of glaucoma undergoing planned ophthalmic surgery as part of their routine care and compared them with patients without glaucoma undergoing phacoemulsification for age-related cataract. We recruited 110 patients with glaucoma and 113 patients without glaucoma and collected AH and blood from these participants. Levels of AH and serum NfL were quantified using the Single-Molecule Array (Simoa) NF-light assay (Quanterix). Clinical information was obtained by reviewing the medical records.

Results

In a model controlling for age and body mass index (BMI), AH NfL was significantly elevated in patients with glaucoma compared with controls (P < 0.001). In contrast, after controlling for age, BMI, and Mini Mental Status Examination (MMSE) scores, serum NfL was not elevated in patients with glaucoma compared with controls (P = 0.81).

Conclusions

Although our findings validate AH NfL as a marker of glaucomatous neurodegeneration, no such evidence was found for serum NfL.

Translational Relevance

NfL levels in AH may be a molecular marker of retinal ganglion cell health in glaucoma; in contrast, serum NfL has limited utility for monitoring glaucomatous neurodegeneration.

Cerebrospinal fluid biomarkers as predictors of multiple sclerosis severity

BACKGROUND

Prognostic biomarkers at multiple sclerosis (MS) onset to predict disease severity may help guide initial therapy selection for people with MS. Over 20 disease-modifying treatments (DMTs) of varying levels of risk and efficacy now exist. The ability to predict MS severity would help to identify those patients at higher risk where a highly effective, but potentially risky, therapy would be optimal. The goal of this project was to determine if cerebrospinal fluid (CSF) soluble markers obtained near time of diagnosis can predict disease severity in people with relapsing remitting MS (RRMS).

METHODS

We identified 42 RRMS subjects with 4 or more years of clinical follow-up at our center, 8 subjects with other inflammatory neurological diseases (OIND), and 4 subjects with non-inflammatory neurological diseases (NIND) who had donated CSF samples collected for disease diagnosis. This study evaluated soluble CSF biomarkers chosen to reflect neuroinflammation (chemokine ligand 13 - CXCL13), microglia activity (soluble triggering receptor expressed on myeloid cells 2 - sTREM2), demyelination (myelin basic protein -MBP), axon injury and loss (neurofilament light, heavy, and intermediate chains - NFL, NFH, internexin-alpha - INT-α) and neuronal loss (parvalbumin - PVALB) to determine whether any of these CSF factors might predict future MS disease severity. The main outcome measure was MS Severity Score (MSSS), which takes into account disability accumulation (expanded disability status scale - EDSS) and duration of disease. EDSS at last clinical visit was a secondary outcome measure. Univariate and multivariable regression models were used for analysis. Spearman correlations were performed to evaluate correlation between laboratory and clinical variables.

RESULTS

Forty-two RRMS patients with mean 9.4 years follow-up since lumbar puncture (LP) contributed data. Higher NFH, NFL, and sTREM2 each predicted worse MSSS using both univariate and multivariable regression models. Older age at the time of LP predicted worse MSSS both in the univariate and multivariable models. NFL correlated with NFH, and both were positively correlated with sTREM2 and CXCL13. In the combined OIND and NIND comparator group, NFH correlated with both NFL and CXCL13.

CONCLUSION

These data support that CSF sTREM2, NFH, and NFL are predictors of MSSS, a measure of MS disease aggressiveness. This study adds to a growing literature implicating microglial activity and axonal injury in MS progression, starting from early stages of the disease.

Neurofilament light chain associates with IVH and ROP in extremely preterm infants

BACKGROUND

Neurofilament light chain (NfL) is known for indicating adult brain injury, but the role of NfL in extremely preterm infants is less studied. This study examines the relationship between NfL and neurovascular morbidities in these infants.

METHODS

A secondary analysis of the Mega Donna Mega trial was conducted on preterm infants <28 weeks gestational age (GA). The study measured NfL levels and proteomic profiles related to the blood-brain barrier in serum from birth to term-equivalent age, investigating the association of NfL with GA, retinopathy of prematurity (ROP), intraventricular hemorrhage (IVH), and blood-brain barrier proteins.

RESULTS

Higher NfL levels were seen in the first month in infants with severe IVH and for those born <25 weeks GA (independent of ROP or IVH). Additionally, infants born at 25-27 weeks GA with high NfL were at increased risk of developing severe ROP (independent of IVH). NfL was significantly associated with the proteins CDH5, ITGB1, and JAM-A during the first month.

CONCLUSION

NfL surges after birth in extremely preterm infants, particularly in those with severe IVH and ROP, and in the most immature infants regardless of IVH or ROP severity. These findings suggest NfL as a potential predictor of neonatal morbidities, warranting further validation studies.

IMPACT STATEMENT

This study shows that higher NfL levels are related to neurovascular morbidities in extremely preterm infants. The degree of immaturity seems important as infants born <25 weeks gestational age exhibited high postnatal serum NfL levels irrespective of neurovascular morbidities. Our findings suggest a potential link between NfL and neurovascular morbidities possibly affected by a more permeable blood-brain barrier.

Immunohistochemical labeling of ongoing axonal degeneration 10 days following cervical contusion spinal cord injury in the rat

STUDY DESIGN

Experimental Animal Study.

OBJECTIVE

To continue validating an antibody which targets an epitope of neurofilament light chain (NF-L) only available during neurodegeneration and to utilize the antibody to describe the pattern of axonal degeneration 10 days post-unilateral C4 contusion in the rat.

SETTING

University of Florida laboratory in Gainesville, USA.

METHODS

Sprague Dawley rats received either a unilateral 150kdyne C4 contusion (n = 4 females, n = 5 males) or a laminectomy control surgery (n = 2 females, n = 3 males). Ten days following SCI or laminectomy, spinal cords and brainstems were processed for immunohistochemistry. Serial spinal cord and brainstem cross-sections were stained with the degeneration-specific NF-L antibody (MCA-6H63) and dual labeled with either an antibody against the C-terminus portion of NF-L (NF-L-Ct), to label healthy axons, or an antibody against amyloid precursor protein (APP), considered the current "gold standard" for identifying axonal injury. The pattern of ongoing axonal degeneration was assessed.

RESULTS

Spinal cord and brainstem cross-sections from injured rats had punctate MCA-6H63 positive fibers with a pathological appearance, loss of anti-NF-L-Ct colabeling, and frequent colocalization with APP. Immunopositive fibers were abundant rostral and caudal to the lesion in white matter tracts that would be disrupted by the unilateral C4 contusion. This pattern of staining was not observed in control tissue.

CONCLUSIONS

The MCA-6H63 antibody labels degenerating axons following SCI and offers a tool to quantify axonal degeneration.

Neurofilament heavy phosphorylated epitopes as biomarkers in ageing and neurodegenerative disease

From the day we are born, the nervous system is subject to insult, disease and degeneration. Aberrant phosphorylation states in neurofilaments, the major intermediate filaments of the neuronal cytoskeleton, accompany and mediate many pathological processes in degenerative disease. Neuronal damage, degeneration and death can release these internal components to the extracellular space and eventually the cerebrospinal fluid and blood. Sophisticated assay techniques are increasingly able to detect their presence and phosphorylation states at very low levels, increasing their utility as biomarkers and providing insights and differential diagnosis for the earliest stages of disease. Although a variety of studies focus on single or small clusters of neurofilament phosphorylated epitopes, this review offers a wider perspective of the phosphorylation landscape of the neurofilament heavy subunit, a major intermediate filament component in both ageing and disease.

A real-world data of serum neurofilament light chain in a large cohort of Egyptian multiple sclerosis patients: Hospital-based study

BACKGROUND

Serum neurofilament light chain (sNFL) is a promising biomarker for neuroaxonal injury in multiple sclerosis (MS). Traditional clinical and radiological examinations often fail to capture the underlying neurodegeneration, particularly in the absence of clinical relapses or gadolinium-enhanced lesions. This study aims to assess sNFL levels in real-world MS patients who have no evidence of activity, to evaluate the potential of sNFL as a biomarker for smoldering-associated worsening (SAW).

MATERIALS AND METHODS

A cross-sectional study, involved 162 MS patients without evidence of disease activity and 40 healthy, age, sex, and education matched controls (HCs). Patients were classified according to MS subtype, DMT status, and type. sNFL levels were measured using an enzyme-linked immunosorbent assay (ELISA) and levels were compared in each group.

RESULTS

sNFL levels were significantly higher in MS patients compared to (HCs) (p < 0.001). Median sNFL levels were lowest in the clinically isolated (CIS) group and steady increase in RRMS and reaching the highest levels in the SPMS group (p < 0.001). Despite a slight decrease in sNFL levels in patients who started DMT for a year or less than in the naïve group, sNFL levels were highest in patients who were on DMTs for longer durations (p = 0.003). EDSS score was the sole independent predictor of sNFL levels (B = 0.415, p = 0.002). A cut-off value of 23.25 pg/ml was set to distinguish cases and HCs (92 % specificity and 90 % sensitivity), and 75.48 pg/ml was set to distinguish progressive forms (70.00 % sensitivity and 78.30 % specificity).

CONCLUSION

sNFL is sensitive for detecting subclinical neurodegeneration in the absence of relapse or gadolinium-enhanced lesions, supporting the utility of sNFL measurements into routine clinical practice to improve monitoring and management of MS.

Plasma extracellular vesicle neurofilament light chain as the biomarkers of the progression of Parkinson's disease

Parkinson's disease (PD) is a common neurodegenerative disorder characterized by progressive symptoms, underscoring the urgent need for predictive blood biomarkers. Plasma extracellular vesicles (EVs) offer a promising platform for biomarker development, with neurofilament light chain (NfL) emerging as a potential candidate for neurological diseases. This study evaluated plasma EV NfL as a biomarker for disease progression in a PD cohort.A total of 55 patients with PD (PwP) and 58 healthy controls (HCs) were followed, with PwP completing an average of 3.96 visits and HCs 2.25 visits. Plasma EVs were isolated and validated, and EV NfL levels were measured using an immunomagnetic reduction assay. Generalized estimating equations and Spearman correlations assessed relationships between clinical symptom progression and biomarkers. Although no significant differences in plasma EV NfL levels were observed between PwP and HCs over time, changes in plasma EV NfL significantly correlated with motor symptom progression, specifically with adjusted-total and akinetic-rigidity subscores of the Unified PD Rating Scale (UPDRS) Part III. Additionally, changes in UPDRS Part II scores were significantly associated with plasma EV NfL levels. These findings suggest that plasma EV NfL reflects motor symptom progression in PwP, highlighting its potential as a valuable biomarker for monitoring disease progression and guiding clinical trials in PD.

Neurofilament light chain (Nf-L) in cerebrospinal fluid and serum as a potential biomarker in the differential diagnosis of neurological diseases in cattle

Neurofilament light chain (Nf-L) is a biomarker for axonal damage in human neurology but is understudied in cattle. With this study we wanted to determine Nf-L stability at two different storage temperatures and Nf-L levels in healthy cattle and the relationship with age, evaluate whether Nf-L holds diagnostic potential for neurological disorders, and whether an association exists between Nf-L in serum and in cerebrospinal fluid (CSF). To do this, we measured Nf-L levels in CSF and serum samples from 49 healthy and 75 sick cattle. Storage at -80 °C or -20 °C had no impact on Nf-L concentration. Physiological median Nf-L levels were 6.3 pg/mL (serum) and 414 pg/mL (CSF) in calves and 5.5 pg/mL (serum) and 828 pg/mL (CSF) in adult cattle. There was no association between Nf-L levels in CSF and calf age (r2 0.07, p = 0.13), while a weak association was found for Nf-L in serum (r2 0.26, p = 0.01), and a significant association in adult cattle (CSF, r2 0.69, p = 0.0001; serum, r2 0.68, p = 0.0003). CSF Nf-L levels were higher in samples from animals with degenerative (median Nf-L 49971 pg/mL) and infectious central nervous system (CNS) disorders (median Nf-L, age < 2 months 8863 pg/mL; age 2-12 months 17474 pg/mL; age 1-6 years 3546 pg/mL), CNS anomalies and metabolic/toxic disorders. There was a significant association between CSF Nf-L and serum Nf-L in cattle with neurological disorders (r2 0.2, p = 0.009). Taken together, these findings suggest the potential of Nf-L as a diagnostic tool in cattle neurology.

The potential role of SCF combined with DPCs in facial nerve repair

Facial nerve injuries lead to significant functional impairments and psychological distress for affected patients. Effective repair of these injuries remains a challenge. For longer nerve gaps, the regeneration outcomes after nerve grafting remain suboptimal due to limited sources and postoperative immune responses. Tissue engineering techniques are conventional methods for repairing peripheral nerve defects. This study explores the potential of dental pulp cells (DPCs) combined with stem cell factor (SCF) to enhance neurogenic differentiation and improve facial nerve regeneration. DPCs were isolated from rabbit dental pulp, the pluripotency of the cells was identified from three perspectives: osteogenic differentiation, adipogenic differentiation, and neurogenic differentiation. In vivo experiments involved injuring the buccal branch of the facial nerve in New Zealand white rabbits, followed by treatment with PBS, DPCs, SCF, or SCF + DPCs. Functional recovery was assessed over 12 weeks, with SCF + DPCs demonstrating the most significant improvement in whisker movement scores. Histomorphological evaluations revealed enhanced myelinated fiber density and axonal morphology in the SCF + DPCs group. RNA sequencing identified 608 differentially expressed genes, with enrichment in the TGF-β signaling pathway. In in vitro experiments, we demonstrated from multiple angles using Western blot analysis, Real-time quantitative polymerase chain reaction (QPCR) analysis, and immunofluorescence staining that SCF can promote the neurogenic differentiation of DPCs through the TGF-β1 signaling pathway. Our findings indicate that the combination of SCF and DPCs offers a promising strategy for enhancing facial nerve repair.

Brain injury biomarkers and applications in neurological diseases

ABSTRACT

Neurological diseases are a major health concern, and brain injury is a typical pathological process in various neurological disorders. Different biomarkers in the blood or the cerebrospinal fluid are associated with specific physiological and pathological processes. They are vital in identifying, diagnosing, and treating brain injuries. In this review, we described biomarkers for neuronal cell body injury (neuron-specific enolase, ubiquitin C-terminal hydrolase-L1, αII-spectrin), axonal injury (neurofilament proteins, tau), astrocyte injury (S100β, glial fibrillary acidic protein), demyelination (myelin basic protein), autoantibodies, and other emerging biomarkers (extracellular vesicles, microRNAs). We aimed to summarize the applications of these biomarkers and their related interests and limits in the diagnosis and prognosis for neurological diseases, including traumatic brain injury, status epilepticus, stroke, Alzheimer's disease, and infection. In addition, a reasonable outlook for brain injury biomarkers as ideal detection tools for neurological diseases is presented.

Biomarkers Unveiling the Interplay of Mind, Nervous System, and Immunity

The field of psychoneuroimmunology has significantly expanded in the last few decades and so has our understanding of the bidirectional communications between the immune and central nervous systems (CNS). There is a preponderance of evidence supporting the fact that immunological pathways and neuroinflammation are involved in the pathophysiology of multiple neurological and mental health conditions. In this chapter, we have explored various neuroimmunological biomarkers involved in these pathways, responsible for developing and perpetuating different neuropsychiatric disorders. This chapter will examine inflammatory biomarkers and those associated with intestinal homeostasis, blood-brain barrier (BBB) permeability, glial cells, and neuronal injury. A range of tests has been developed to evaluate these markers, and we will also explore the existing methods currently employed for these techniques. Further studies of these inflammatory and neurological markers are needed to support their utility as biomarkers for diagnosis and prognosis and to inform treatment strategies for various neuropsychiatric disorders.

Vibrotactile stimulation at 40 Hz inhibits Aβ-induced changes in SH-SY5Y, BV2 cells, and pericytes

Alzheimer's disease (AD) poses a major societal challenge, yet no definitive cure exists. Noninvasive brain stimulation methods, such as transcranial magnetic stimulation and transcranial direct current stimulation, have shown promise in alleviating cognitive symptoms associated with neurodegenerative disorders. This study investigated the effects of 40 Hz vibrotactile stimulation on AD-related cellular responses using SH-SY5Y neuroblastoma cells, primary human brain pericytes, and BV2 microglia. SH-SY5Y cells and brain pericytes treated with oligomeric beta-amyloid (Aβ) underwent 40 Hz vibrational stimulation for varying durations. Cell viability was determined via the CCK-8 assay, while intracellular calcium levels in pericytes were assessed. Protein expression was measured using western blotting, and gene expression was quantified via a real-time quantitative polymerase chain reaction. Detailed vibrational parameters were employed to ensure precise stimulation. Notably, 40 Hz vibrotactile stimulation improved cell viability in Aβ-exposed SH-SY5Y cells, reduced intracellular calcium ion (Ca2+) levels in Aβ-treated pericytes, activated autophagy, and mitigated tau hyperphosphorylation in SH-SY5Y cells. Additionally, it exhibited anti-neuroinflammatory properties in BV2 microglia. These findings highlight the potential of 40 Hz vibrotactile stimulation as a therapeutic strategy for AD.

Neurological Biomarker Profiles in Royal Canadian Air Force (RCAF) Pilots and Aircrew

BACKGROUND/OBJECTIVES

Military aviators can be exposed to extreme physiological stressors, including decompression stress, G-forces, as well as intermittent hypoxia and/or hyperoxia, which may contribute to neurobiological dysfunction/damage. This study aimed to investigate the levels of neurological biomarkers in military aviators to assess the potential risk of long-term brain injury and neurodegeneration.

METHODS

This cross-sectional study involved 48 Canadian Armed Forces (CAF) aviators and 48 non-aviator CAF controls. Plasma samples were analyzed for biomarkers of glial activation (GFAP), axonal damage (NF-L, pNF-H), oxidative stress (PRDX-6), and neurodegeneration (T-tau), along with S100b, NSE, and UCHL-1. The biomarker concentrations were quantified using multiplexed immunoassays.

RESULTS

The aviators exhibited significantly elevated levels of GFAP, NF-L, PRDX-6, and T-tau compared to the CAF controls (p < 0.001), indicating increased glial activation, axonal injury, and oxidative stress. Trends toward higher levels of S100b, NSE, and UCHL-1 were observed but were not statistically significant. The elevated biomarker levels suggest cumulative brain damage, raising concerns about potential long-term neurological impairments.

CONCLUSIONS

Military aviators are at increased risk for neurobiological injury, including glial and axonal damage, oxidative stress, and early neurodegeneration. These findings emphasize the importance of proactive monitoring and further research to understand the long-term impacts of high-altitude flight on brain health and to develop strategies for mitigating cognitive decline and neurodegenerative risks in this population.

Single-cell transcriptomic and neuropathologic analysis reveals dysregulation of the integrated stress response in progressive supranuclear palsy

Progressive supranuclear palsy (PSP) is a sporadic neurodegenerative tauopathy variably affecting brainstem and cortical structures, and characterized by tau inclusions in neurons and glia. The precise mechanism whereby these protein aggregates lead to cell death remains unclear. To investigate the contribution of these different cellular abnormalities to PSP pathogenesis, we performed single-nucleus RNA sequencing (snRNA-seq) and analyzed 50,708 high quality nuclei targeting the diencephalon, including the subthalamic nucleus and adjacent structures, from human post-mortem PSP brains with varying degrees of pathology compared to controls. Cell-type-specific differential expression and pathway analysis identified both common and discrete changes in numerous pathways previously implicated in PSP and other neurodegenerative disorders. This included EIF2 signaling, an adaptive pathway activated in response to diverse stressors, which was activated in multiple vulnerable cell types and validated in independent snRNA-seq and bulk RNA-seq datasets. Using immunohistochemistry, we found that activated eIF2α was positively correlated with tau pathology burden in vulnerable brain regions. Multiplex immunofluorescence localized activated eIF2α positivity to hyperphosphorylated tau (p-tau) positive neurons and ALDH1L1-positive astrocytes, supporting the increased transcriptomic EIF2 activation observed in these vulnerable cell types. In conclusion, these data provide insights into cell-type-specific pathological changes in PSP and support the hypothesis that failure of adaptive stress pathways play a mechanistic role in the pathogenesis and progression of PSP.

Customized antisense oligonucleotide-based therapy for neurofilament-associated Charcot-Marie-Tooth disease

DNA-based therapeutics have emerged as a revolutionary approach for addressing the treatment gap in rare inherited conditions by targeting the fundamental genetic causes of disease. Charcot-Marie-Tooth (CMT) disease, a group of inherited neuropathies, represents one of the most prevalent Mendelian disease groups in neurology and is characterized by diverse genetic aetiology. Axonal forms of CMT, known as CMT2, are caused by dominant mutations in >30 different genes that lead to degeneration of lower motor neuron axons. Recent advances in antisense oligonucleotide therapeutics have shown promise in targeting neurodegenerative disorders. Here, we elucidate pathomechanistic changes contributing to variant specific molecular phenotypes in CMT2E, caused by a single nucleotide substitution (p.N98S) in the neurofilament light chain gene (NEFL). We used a patient-derived induced pluripotent stem cell-induced motor neuron model that recapitulates several cellular and biomarker phenotypes associated with CMT2E. Using an antisense oligonucleotide treatment strategy targeting a heterozygous gain-of-function variant, we aimed to resolve molecular phenotypic changes observed in the CMT2E p.N98S subtype. To determine the therapeutic potential of antisense oligonucleotide, we applied our treatment strategy in induced pluripotent stem cell-derived motor neurons and used both established and new biomarkers of peripheral nervous system axonal degeneration. Our findings demonstrated a significant decrease in clinically relevant biomarkers of axonal degeneration, presenting the first clinically viable genetic therapeutic for CMT2E. Similar strategies could be used to develop precision medicine approaches for otherwise untreatable gain-of-function inherited disorders.

Emerging Trends: Neurofilament Biomarkers in Precision Neurology

Neurofilaments are structural proteins found in the cytoplasm of neurons, particularly in axons, providing structural support and stability to the axon. They consist of multiple subunits, including NF-H, NF-M, and NF-L, which form long filaments along the axon's length. Neurofilaments are crucial for maintaining the shape and integrity of neurons, promoting axonal transport, and regulating neuronal function. They are part of the intermediate filament (IF) family, which has approximately 70 tissue-specific genes. This diversity allows for a customizable cytoplasmic meshwork, adapting to the unique structural demands of different tissues and cell types. Neurofilament proteins show increased levels in both cerebrospinal fluid (CSF) and blood after neuroaxonal damage, indicating injury regardless of the underlying etiology. Precise measurement and long-term monitoring of damage are necessary for determining prognosis, assessing disease activity, tracking therapeutic responses, and creating treatments. These investigations contribute to our understanding of the importance of proper NF composition in fundamental neuronal processes and have implications for neurological disorders associated with NF abnormalities along with its alteration in different animal and human models. Here in this review, we have highlighted various neurological disorders such as Alzheimer's, Parkinson's, Huntington's, Dementia, and paved the way to use neurofilament as a marker in managing neurological disorders.

Molecular mechanisms of neurofilament alterations and its application in assessing neurodegenerative disorders

Neurofilaments are intermediate filaments present in neurons. These provide structural support and maintain the size and shape of the neurons. Dysregulation, mutation, and aggregation of neurofilaments raise the levels of these proteins in the blood and cerebrospinal fluid (CSF), which are characteristic features of axonal damage and certain rare neurological diseases, such as Giant Axonal Neuropathy and Charcot-Mare-Tooth disease. Understanding the structure, dynamics, and function of neurofilaments has been greatly enhanced by a diverse range of biochemical and preclinical investigations conducted over more than four decades. Recently, there has been a resurgence of interest in post-translational modifications of neurofilaments, such as phosphorylation, aggregation, mutation, oxidation, etc. Over the past twenty years, several rare disorders have been studied from structural alterations of neurofilaments. These disorders are monitored by fluid biomarkers such as neurofilament light chains. Currently, there are many tools, such as Enzyme-Linked Immunosorbent Assay, Electrochemiluminescence Assay, Single-Molecule Array, Western/immunoblotting, etc., in use to assess the neurofilament proteins in Blood and CSF. However, all these techniques utilize expensive, non-specific, or antibody-based methods, which make them unsuitable for routine screening of neurodegenerative disorders. This provides room to search for newer sensitive, cost-effective, point-of-care tools for rapid screening of the disease. For a long time, the molecular mechanisms of neurofilaments have been poorly understood due to insufficient research attempts, and a deeper understanding of them remains elusive. Therefore, this review aims to highlight the available literature on molecular mechanisms of neurofilaments and the function of neurofilaments in axonal transport, axonal conduction, axonal growth, and neurofilament aggregation, respectively. Further, this review discusses the role of neurofilaments as potential biomarkers for the identification of several neurodegenerative diseases in clinical laboratory practice.

Plasma neurofilament heavy chain is a prognostic biomarker for the development of severe epilepsy after experimental traumatic brain injury

OBJECTIVE

This study was undertaken to test whether the postinjury plasma concentration of phosphorylated neurofilament heavy chain (pNF-H), a marker of axonal injury, is a prognostic biomarker for the development of posttraumatic epilepsy.

METHODS

Tail vein plasma was sampled 48 h after traumatic brain injury (TBI) from 143 rats (10 naïve, 21 controls, 112 with lateral fluid percussion injury) to quantify pNF-H by enzyme-linked immunosorbent assay. During the 6th postinjury month, rats underwent 30 days of continuous video-electroencephalographic monitoring to detect unprovoked seizures and evaluate epilepsy severity. Somatomotor (composite neuroscore) and spatial memory (Morris water maze) testing and quantitative T2 magnetic resonance imaging were performed to assess comorbidities and lesion severity.

RESULTS

Of the 112 TBI rats, 25% (28/112) developed epilepsy (TBI+) and 75% (84/112) did not (TBI-). Plasma pNF-H concentrations were higher in TBI+ rats than in TBI- rats (p < .05). Receiver operating characteristic curve analysis indicated that plasma pNF-H concentration distinguished TBI+ rats from TBI- rats (area under the curve [AUC] = .647, p < .05). Differentiation was stronger when comparing TBI+ rats exhibiting severe epilepsy (≥3 seizures/month) with all other TBI rats (AUC = .732, p < .01). Plasma pNF-H concentration on day 2 (D2) distinguished TBI+ rats with seizure clusters from other TBI rats (AUC = .732, p < .05). Higher plasma pNF-H concentration on D2 after TBI correlated with lower neuroscores on D2 (p < .001), D6 (p < .001), and D14 (p < .01). Higher pNF-H concentration on D2 correlated with greater T2 signal abnormality volume on D2 (p < .001) and D7 (p < .01) and larger cortical lesion area on D182 (p < .01). Plasma pNF-H concentration on D2 did not correlate with Morris water maze performance on D37-D39.

SIGNIFICANCE

Plasma pNF-H is a promising clinically translatable prognostic biomarker for the development of posttraumatic epilepsy with frequent seizures or seizure clusters.

Extracellular Vesicles from Human Induced Pluripotent Stem Cells Exhibit a Unique MicroRNA and CircRNA Signature

Extracellular vesicles (EV) have emerged as promising cell-free therapeutics in regenerative medicine. However, translating primary cell line-derived EV to clinical applications requires large-scale manufacturing and several challenges, such as replicative senescence, donor heterogeneity, and genetic instability. To address these limitations, we used a reprogramming approach to generate human induced pluripotent stem cells (hiPSC) from the young source of cord blood mesenchymal stem/stromal cells (CBMSC). Capitalizing on their inexhaustible supply potential, hiPSC offer an attractive EV reservoir. Our approach encompassed an exhaustive characterization of hiPSC-EV, aligning with the rigorous MISEV2023 guidelines. Analyses demonstrated physical features compatible with small EV (sEV) and established their identity and purity. Moreover, the sEV-shuttled non-coding (nc) RNA landscape, focusing on the microRNA and circular RNA cargo, completed the molecular signature. The kinetics of the hiPSC-sEV release and cell internalization assays unveiled robust EV production and consistent uptake by human neurons. Furthermore, hiPSC-sEV demonstrated ex vivo cell tissue-protective properties. Finally, via bioinformatics, the potential involvement of the ncRNA cargo in the hiPSC-sEV biological effects was explored. This study significantly advances the understanding of pluripotent stem cell-derived EV. We propose cord blood MSC-derived hiPSC as a promising source for potentially therapeutic sEV.

Detection of Brain-Derived Cell-Free DNA in Plasma

Background: Neuronal loss is a major pathological feature of neurodegenerative diseases. The analysis of plasma cell-free DNA (cfDNA) is an emerging approach to track cell death events in a minimally invasive way and from inaccessible areas of the body, such as the brain. Previous studies showed that DNA methylation (DNAm) profiles can be used to map the tissue of origin of cfDNA and to identify molecules released from the brain upon cell death. The aim of the present study is to contribute to this research field, presenting the development and validation of an assay for the detection of brain-derived cfDNA (bcfDNA). Methods: To identify CpG sites with brain-specific DNAm, we compared brain and non-brain tissues for their chromatin state profiles and genome-wide DNAm data, available in public datasets. The selected target genomic regions were experimentally validated by bisulfite sequencing on DNA extracted from 44 different autoptic tissues, including multiple brain regions. Sequencing data were analysed to identify brain-specific epihaplotypes. The developed assay was tested in plasma cfDNA from patients with immune effector cell-associated neurotoxicity syndrome (ICANS) following chimeric antigen receptor T (CAR-T) therapy. Results: We validated five genomic regions with brain-specific DNAm (four hypomethylated and one hypermethylated in the brain). DNAm analysis of the selected genomic regions in plasma samples from CAR-T patients revealed higher levels of bcfDNA in participants with ongoing neurotoxicity syndrome. Conclusions: We developed an assay for the analysis of bcfDNA in plasma. The assay is a promising tool for the early detection of neuronal loss in neurodegenerative diseases.

Cerebrospinal fluid neurofilament light chain levels in children with acquired demyelinating syndrome

Objective

To study the cerebrospinal fluid (CSF) neurofilament light chain (NfL) in pediatric acquired demyelinating syndrome (ADS) and its association with factors of laboratory and imaging results.

Methods

We analyzed clinical data from children with ADS collected from May 2020 to January 2021 at the Department of Neurology of Guangzhou Women and Children's Medical Center. Enzyme-linked immunosorbent assays were used to detect the CSF NfL of patients.

Results

Thirty pediatric ADS patients (17 male, 13 female) were included in the study. The most frequent diagnosis was uncategorized ADS (36.7%, 11/30), followed by acute disseminating encephalomyelitis (ADEM) (23.3%, 7/30), myelin oligodendrocyte glycoprotein antibody-associated disorder (MOGAD) (20.0%, 6/30), NMO (6.7%, 2/30), multiple sclerosis (MS) (6.7%, 2/30), and neuromyelitis optic spectrum disorders (NMOSD) (6.7%, 2/30). The median CSF NfL for the first time was 7,425.28 pg/ml (interquartile range, 1,273.51, >10,000 pg/ml). CSF NfL increase over normal value (<290.00 pg/ml for people younger than 30 years old) was seen in 98.7% of patients. Patients were divided into uncategorized ADS, ADEM, MOGAD, and MS/NMO/NMOSD groups, with no significant difference in CSF NfL between each group. The CSF NfL positively correlated with the immunoglobulin (Ig) G (ρ = 0.473) and IgE (ρ = 0.366). However, the CSF NfL did not correlate with CSF white blood count and CSF protein. Furthermore, there was no significant difference between patients with oligoclonal bands positive and without. The CSF NfL negatively correlated with interferon γ (ρ = -0.501), CD45 + CD3+ T (ρ = -0.466), CD45 + CD3 + CD4+ T (ρ = -0.466), and CD45 + CD3 + CD8+ T cells (ρ = -0.521). However, it did not correlate with CD45 + CD19+ B cells. CSF NfL in patients with cerebral white matter lesions in MRI was higher than in patients without. Moreover, the CSF NfL positively correlated with the number of brain MRI locations (ρ = 0.362). Nine patients underwent multiple detections of CSF NfL, and their CSF NfL for the last detection was not significantly different from the first.

Conclusions

The CSF NfL increases significantly in pediatric ADS, and it can be a biomarker of neuro-axonal injury and a good indication of the extent of lesions.

Proteomics Analysis of Human Chorionic Villi Reveals Dysregulated Pathways That Contribute to Recurrent Pregnancy Loss

PURPOSE

Recurrent pregnancy loss (RPL) represents a common disorder with consequences on family and society. As more than half of the RPL cases do not have a clearly identified cause, uncovering the mechanisms behind the idiopathic RPL is urgently needed.

EXPERIMENTAL DESIGN

Using label-free data-independent LC-MS/MS acquisition coupled with ion mobility, we compared the proteome of chorionic villi from 13 RPL cases with 10 age and gestational week-matched elective pregnancies. Transcriptional levels of selected candidate biomarkers were determined in chorionic villi of 35 RPL cases and 25 controls using quantitative polymerase chain reaction (qPCR).

RESULTS

Statistically significant difference in abundance (Benjamini-Hochberg [B-H] p ≤ 0.05) and fold change ≥1.5 showed 128 proteins. Bioinformatics analysis identified complement and coagulation cascades, platelet activation, tricarboxylic acid cycle (TCA) cycle, and ferroptosis as pathways with the highest significance. Correlation with transcriptome datasets revealed a weak statistically significant positive correlation with 45% of the co-differentially expressed proteins/genes displaying the same regulation trend. The transcription levels of neurofilament light polypeptide (NEFL), dihydrolipoyllysine-residue succinyltransferase component of 2-oxoglutarate dehydrogenase complex_mitochondrial (DLST), nitric oxide synthase 3 (NOS3), and ceruloplasmin (CP) were significantly increased in the RPL, consistent with the proteomics findings.

CONCLUSIONS AND CLINICAL RELEVANCE

Our data suggests alteration of several pathways as potential causes of idiopathic RPL from the fetal side and opens the way for investigations concerning clinical management.

The Relevance of Spinal Muscular Atrophy Biomarkers in the Treatment Era

Spinal muscular atrophy (SMA) is a severe neuromuscular disorder that currently has an approved treatment for all forms of the disease. Previously, biomarkers were primarily used for diagnostic purposes, such as detecting the presence of the disease or determining a specific clinical type of SMA. Currently, with the availability of therapy, biomarkers have become more valuable due to their potential for prognostic, predictive, and pharmacodynamic applications. This review describes the most promising physiological, functional, imaging and molecular biomarkers for SMA, derived from different patients' tissues. The review summarizes information about classical biomarkers that are already used in clinical practice as well as fresh findings on promising biomarkers that have been recently disclosed. It highlights the usefulness, limitations, and strengths of each potential biomarker, indicating the purposes for which each is best suited and when combining them may be most beneficial.

Comparison of Serum and Cerebrospinal Fluid Neurofilament Light Chain Concentrations Measured by Ella™ and Lumipulse™ in Patients with Cognitive Impairment

OBJECTIVE

Neurofilament light chain proteins (NfLs) are considered a promising biomarker of neuroaxonal damage in several neurological diseases. Their measurement in the serum and cerebrospinal fluid (CSF) of patients with dementia may be especially useful. Our aim was to compare the NfL measurement performance of two advanced technologies, specifically the Ella™ microfluidic platform and the Lumipulse™ fully automated system, in patients with cognitive disorders.

METHODS

Thirty subjects with neurodegenerative cognitive disorders (10 with Alzheimer's Disease, 10 with Frontotemporal Dementia, and 10 with non-progressive Mild Cognitive Impairment) seen at the Cognitive Neurology Clinic of Modena University Hospital (Italy) underwent CSF and serum NfL measurement with both the Ella™ microfluidic platform (Bio-Techne, Minneapolis, MN, USA)) and the Lumipulse™ fully automated system for the CLEIA (Fujirebio Inc., Ghent, Belgium). Correlation and regression analyses were applied to assess the association between NfL concentrations obtained with the two assays in CSF and serum. The Passing-Bablok regression method was employed to evaluate the agreement between the assays.

RESULTS

There were high correlations between the two assays (r = 0.976, 95% CI. 0.950-0.989 for CSF vs. r = 0.923, 95% CI 0.842-0.964 for serum). A Passing-Bablok regression model was estimated to explain the relationship between the two assays, allowing us to switch from one to the other when only one assay was available.

CONCLUSIONS

We found a good degree of correlation between the two methods in patients with neurocognitive disorders. We also established a method that will allow comparisons between results obtained with either technique, allowing for meta-analyses and larger sample sizes.

Implications of Lead (Pb)-Induced Transcriptomic and Phenotypic Alterations in the Aged Zebrafish (Danio rerio)

Lead (Pb) is a well-known neurotoxin with established adverse effects on the neurological functions of children and younger adults, including motor, learning, and memory abilities. However, its potential impact on older adults has received less attention. Using the zebrafish model, our study aims to characterize the dose-response relationship between environmentally relevant Pb exposure levels and their effects on changes in behavior and transcriptomics during the geriatric periods. We exposed two-year-old zebrafish to waterborne lead acetate (1, 10, 100, 1000, or 10,000 µg/L) or a vehicle (DMSO) for 5 days. While lower concentrations (1-100 µg/L) reflect environmentally relevant Pb levels, higher concentrations (1000-10,000 µg/L) were included to assess acute toxicity under extreme exposure scenarios. We conducted adult behavior assessment to evaluate the locomotor activity following exposure. The same individual fish were subsequently sacrificed for brain dissection after a day of recovery in the aquatic system. RNA extraction and sequencing were then performed to evaluate the Pb-induced transcriptomic changes. Higher (1000-10,000 ug/L) Pb levels induced hyperactive locomotor patterns in aged zebrafish, while lower (10-100 ug/L) Pb levels resulted in the lowest locomotor activity compared to the control group. Exposure to 100 µg/L led to the highest number of differentially expressed genes (DEGs), while 10,000 µg/L induced larger fold changes in both directions. The neurological pathways impacted by Pb exposure include functions related to neurotransmission, such as cytoskeletal regulation and synaptogenesis, and oxidative stress response, such as mitochondrial dysfunction and downregulation of heat shock protein genes. These findings emphasize a U-shape dose-response relationship with Pb concentrations in locomotor activity and transcriptomic changes in the aging brain.

Blood-Based Biomarkers in Alzheimer's Disease: Advancing Non-Invasive Diagnostics and Prognostics

Alzheimer's disease (AD), the most prevalent form of dementia, is expected to rise dramatically in incidence due to the global population aging. Traditional diagnostic approaches, such as cerebrospinal fluid analysis and positron emission tomography, are expensive and invasive, limiting their routine clinical use. Recent advances in blood-based biomarkers, including amyloid-beta, phosphorylated tau, and neurofilament light, offer promising non-invasive alternatives for early AD detection and disease monitoring. This review synthesizes current research on these blood-based biomarkers, highlighting their potential to track AD pathology and enhance diagnostic accuracy. Furthermore, this review uniquely integrates recent findings on protein-protein interaction networks and microRNA pathways, exploring novel combinations of proteomic, genomic, and epigenomic biomarkers that provide new insights into AD's molecular mechanisms. Additionally, we discuss the integration of these biomarkers with advanced neuroimaging techniques, emphasizing their potential to revolutionize AD diagnostics. Although large-scale validation is still needed, these biomarkers represent a critical advancement toward more accessible, cost-effective, and early diagnostic tools for AD.

Neurofilament light chain as a biomarker of chemotherapy-induced peripheral neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of chemotherapy. The frequency of CIPN ranges from one in three to almost all patients depending on type of chemotherapy and dose. It causes symptoms that can range from sensitivity to touch and numbness to neuropathic pain in hands and feet. CIPN is notoriously difficult to grade objectively and has mostly relied on a clinician- or patient-based rating that is subjective and poorly reproducible. Thus, considerable effort has been aimed at identifying objective biomarkers of CIPN. Recent in vitro, animal, and clinical studies suggest that neurofilament light chain (NFL), a structural neuronal protein, may be an objective biomarker of CIPN. NFL released from cells to cell culture media reflects in vitro neurotoxicity, while NFL in serum reflects neuronal damage caused by chemotherapy in rodent models. Finally, NFL in serum may be a diagnostic biomarker of CIPN, but its prognostic ability to predict CIPN requires prospective evaluation. We discuss current limitations and future perspectives on the use of NFL as a preclinical and clinical biomarker of CIPN.

Nutritional Optimization for Brain Health in Contact Sports: A Systematic Review and Meta-Analysis on Long-Chain ω-3 Fatty Acids and Neurofilament Light

Background

Accumulating evidence has highlighted the acute and chronic impact of repetitive subconcussive head impacts (rSHIs) in contact sports. Neurofilament-light (Nf-L), a brain-derived biomarker of neuroaxonal injury, elevates in concert with rSHI. Recently, long-chain ω-3 polyunsaturated fatty acids (LC ω-3 PUFAs) supplementation has been suggested to mitigate brain injury from rSHI as reflected by attenuation of Nf-L concentrations within contact sport athletes.

Objective

Using a systematic review with a meta-analysis, we aimed to determine the effect of LC ω-3 PUFA supplementation on Nf-L concentrations in athletes routinely exposed to rSHI.

Methods

Electronic databases (PubMed and CINAHL) were searched from inception through January 2024. One-stage meta-analysis of individual participant-level data was used to detect changes in Nf-L concentrations between LC ω-3 PUFA and control/placebo (PL) groups from baseline to midseason (MS) and postseason (PS). Least square means (±SE) for Nf-L change from baseline were compared by treatment group for MS/PS using contrast t tests. Significance was set a priori at adjusted P ≤ 0.05.

Results

Of 460 records identified, 3 studies in collegiate American football players (n = 179; LC ω-3 PUFA = 105, PL = 71) were included in the meta-analysis. Compared with PL, the change in Nf-L concentrations was statistically similar at MS [mean difference (MD) = -1.66 ± 0.82 pg·mL-1, adjusted P = 0.09] and significantly lower at PS (MD = -2.23 ± 0.83 pg·mL-1, adjusted P = 0.02) in athletes following LC ω-3 PUFA supplementation.

Conclusions

Our findings demonstrate preliminary support for the prophylactic administration of LC ω-3 PUFA in contact sport athletes exposed to rSHI; however, further research is required to determine the effective dosage required.This trial was registered at OSF (DOI: https://doi.org/10.17605/OSF.IO/EY5QW).

Biomarker discovery in progressive supranuclear palsy from human cerebrospinal fluid

BACKGROUND

Progressive supranuclear palsy (PSP) is a neurodegenerative disorder often misdiagnosed as Parkinson's Disease (PD) due to shared symptoms. PSP is characterized by the accumulation of tau protein in specific brain regions, leading to loss of balance, gaze impairment, and dementia. Diagnosing PSP is challenging, and there is a significant demand for reliable biomarkers. Existing biomarkers, including tau protein and neurofilament light chain (NfL) levels in cerebrospinal fluid (CSF), show inconsistencies in distinguishing PSP from other neurodegenerative disorders. Therefore, the development of new biomarkers for PSP is imperative.

METHODS

We conducted an extensive proteome analysis of CSF samples from 40 PSP patients, 40 PD patients, and 40 healthy controls (HC) using tandem mass tag-based quantification. Mass spectrometry analysis of 120 CSF samples was performed across 13 batches of 11-plex TMT experiments, with data normalization to reduce batch effects. Pathway, interactome, cell-type-specific enrichment, and bootstrap receiver operating characteristic analyses were performed to identify key candidate biomarkers.

RESULTS

We identified a total of 3,653 unique proteins. Our analysis revealed 190, 152, and 247 differentially expressed proteins in comparisons of PSP vs. HC, PSP vs. PD, and PSP vs. both PD and HC, respectively. Gene set enrichment and interactome analysis of the differentially expressed proteins in PSP CSF showed their involvement in cell adhesion, cholesterol metabolism, and glycan biosynthesis. Cell-type enrichment analysis indicated a predominance of neuronally-derived proteins among the differentially expressed proteins. The potential biomarker classification performance demonstrated that ATP6AP2 (reduced in PSP) had the highest AUC (0.922), followed by NEFM, EFEMP2, LAMP2, CHST12, FAT2, B4GALT1, LCAT, CBLN3, FSTL5, ATP6AP1, and GGH.

CONCLUSION

Biomarker candidate proteins ATP6AP2, NEFM, and CHI3L1 were identified as key differentiators of PSP from the other groups. This study represents the first large-scale use of mass spectrometry-based proteome analysis to identify cerebrospinal fluid (CSF) biomarkers specific to progressive supranuclear palsy (PSP) that can differentiate it from Parkinson's disease (PD) and healthy controls. Our findings lay a crucial foundation for the development and validation of reliable biomarkers, which will enhance diagnostic accuracy and facilitate early detection of PSP.

Neurofilament light chain as a promising biomarker for depression diagnosis: a systematic review and meta-analysis

BACKGROUND

Depression is a prevalent and serious mental health disorder that significantly impacts daily life and functioning. Neurofilament Light chain (NfL), associated with axonal neuronal damage, has been identified as a promising biomarker, potentially aiding in early diagnosis of depression, personalized treatment, and tracking disease progression. This study used meta-analysis to evaluate the potential of plasma NfL as a biomarker for depression patients.

METHODS

A systematic search following the PRISMA guidelines was conducted across PubMed, Web of Science, Scopus, and Google Scholar databases to find relevant studies on plasma NfL levels in patients with depression. A random effects model meta-analysis was applied to determine its potential as a biomarker for differentiating patients from controls.

RESULTS

Our meta-analysis, based on four articles with six datasets, revealed that plasma NfL levels were notably higher in individuals with depression (228 cases) compared to healthy controls (118 individuals). The weighted mean difference (WMD) was 8.78 (95% CI: 5.28, 12.28; P < 0.01), indicating a significant effect size. Given the diverse confounding factors inherent in the included observational studies, the observed variability can be attributed to these influences. Due to the observed heterogeneity (heterogeneity Chi-Square: 54.91, p < 0.05), we performed a subgroup analysis. Subgroup analyses based on depression type and analysis method consistently supported the association between NfL and depression, strengthening the evidence.

CONCLUSION

Our meta-analysis demonstrates that elevated NfL levels may serve as a promising biomarker for diagnosing depressive disorders. Further research on diverse subtypes and longitudinal changes is needed to validate its clinical utility.

Gigaxonin, mutated in Giant Axonal Neuropathy, interacts with TDP-43 and other RNA binding proteins

Giant Axonal Neuropathy (GAN) is a neurodegenerative disease caused by loss-of-function mutations in the KLHL16 gene, encoding the cytoskeleton regulator gigaxonin. In the absence of functional gigaxonin, intermediate filament (IF) proteins accumulate in neurons and other cell types due to impaired turnover and transport. GAN neurons exhibit distended, swollen axons and distal axonal degeneration, but the mechanisms behind this selective neuronal vulnerability are unknown. Our objective was to identify novel gigaxonin interactors pertinent to GAN neurons. Unbiased proteomics revealed a statistically significant predominance of RNA-binding proteins (RBPs) within the soluble gigaxonin interactome and among differentially-expressed proteins in iPSC-neuron progenitors from a patient with classic GAN. Among the identified RBPs was TAR DNA-binding protein 43 (TDP-43), which associated with the gigaxonin protein and its mRNA transcript. TDP-43 co-localized within large axonal neurofilament IFs aggregates in iPSC-motor neurons derived from a GAN patient with the 'axonal CMT-plus' disease phenotype. Our results implicate RBP dysfunction as a potential underappreciated contributor to GAN-related neurodegeneration.

SORD-deficient rats develop a motor-predominant peripheral neuropathy unveiling novel pathophysiological insights

Biallelic SORD mutations cause one of the most frequent forms of recessive hereditary neuropathy, estimated to affect ∼10 000 patients in North America and Europe alone. Pathogenic SORD loss-of-function changes in the encoded enzyme sorbitol dehydrogenase result in abnormally high sorbitol levels in cells and serum. How sorbitol accumulation leads to peripheral neuropathy remains to be elucidated. A reproducible animal model for SORD neuropathy is essential to illuminate the pathogenesis of SORD deficiency and for preclinical studies of potential therapies. Therefore, we have generated a Sord knockout (KO), Sord-/-, Sprague Dawley rat, to model the human disease and to investigate the pathophysiology underlying SORD deficiency. We have characterized the phenotype in these rats with a battery of behavioural tests as well as biochemical, physiological and comprehensive histological examinations. Sord-/- rats had remarkably increased levels of sorbitol in serum, CSF and peripheral nerve. Moreover, serum from Sord-/- rats contained significantly increased levels of neurofilament light chain, an established biomarker for axonal degeneration. Motor performance significantly declined in Sord-/- animals starting at ∼7 months of age. Gait analysis evaluated with video motion-tracking confirmed abnormal gait patterns in the hindlimbs. Motor nerve conduction velocities of the tibial nerves were slowed. Light and electron microscopy of the peripheral nervous system revealed degenerating myelinated axons, de- and remyelinated axons, and a likely pathognomonic finding-enlarged 'ballooned' myelin sheaths. These findings mainly affected myelinated motor axons; myelinated sensory axons were largely spared. In summary, Sord-/- rats develop a motor-predominant neuropathy that closely resembles the human phenotype. Our studies revealed novel significant aspects of SORD deficiency, and this model will lead to an improved understanding of the pathophysiology and the therapeutic options for SORD neuropathy.