Muscle & Nerve

Background: Facioscapulohumeral muscular dystrophy (FSHD) is a common hereditary neuromuscular disorder. The Russian FSHD Patient Registry was established in 2019 following the development of a PCR-based method for genetic confirmation of the diagnosis. Results: The registry included 470 participants (51% male). Genetic confirmation was obtained for 76% (n=356), the remainder were included based on clinical and anamnestic data. Clinical assessment forms and patient-reported questionnaires were analyzed for 310 and 142 patients, respectively. D4Z4 repeat unit (RU) distribution showed patterns consistent with European cohorts, with a predominance of patients with 3 RUs. A moderate inverse correlation was found between RUs number and clinical severity scales. Periscapular weakness was the most common onset manifestation (46.8%), followed by facial weakness (31.6%) which was often unnoticed by patients. The mean age in the Russian cohort was 37.8 years (range 0-97), indicating a younger cohort compared to international data. A delta-adjusted cluster analysis (n=215) identified three distinct trajectories: a classic phenotype with onset before age 14 and early involvement of various muscle groups (n=177), and two clusters characterized by either facial or periscapular onset with slow progression. Conclusion: The Russian FSHD registry provides a comprehensive characterization of a large national cohort, revealing a predominance of patients with 3 D4Z4 repeats and a younger demographic profile compared to international data. Cluster analysis identified three heterogeneous disease trajectories, offering a framework for improved patient stratification.

Adenylosuccinate synthetase 1 (ADSS1) myopathy is an ultra-rare disease characterized by progressive muscle dysfunction. The objective of this investigation was to employ a non-invasive biomarker approach to phenotype (fine-)motor skills, speech production and cognition in adults with ADSS1 myopathy. Five individuals with ADSS1 myopathy and five age-sex-matched healthy controls (HCs) underwent a comprehensive multimodal evaluation. Assessments included, (i) evaluation of motor performance, (ii) speech production and cognitive test batteries, (iii) patient-reported outcomes, (iv) electrical impedance myography (EIM), (v) musculoskeletal magnetic resonance imaging (MRI) and (vi) plasma proteomics. ADSS1 participants vs. HCs demonstrated reduced performance on the 9-Hole Peg and grip strength tests as well as lower self-reported mobility. Speech production analysis revealed asthenia (p=0.02), lower intelligibility (p=0.008), and worse voice quality during the sustained vowel task (p=0.03) in the ADSS1 cohort. Cognitive functioning remained unaffected in patients with ADSS1. On EIM, ADSS1 participants vs. HCs, demonstrated a pattern of higher resistance and lower reactance and phase across upper- and lower-extremity measurements, indicative of poorer muscle health, with large effect sizes (Cliffs 8=0.5-0.9). MRI revealed intramuscular fat infiltration, particularly in posterior compartments of the upper leg (e.g., biceps femoris). Proteomics indicated reduced (p=0.04) Neurotrophin-3 (NTF3; implicated in neuronal development, survival and differentiation) levels in the ADSS1 cohort relative to HCs. Lower NTF3 levels associated with poorer performance on hand-motor tasks as well as higher resistance and lower reactance and phase on EIM. This study highlighted the value of multimodal phenotyping for quantifying disease expression and advancing monitoring strategies in ADSS1 myopathy. Take-home messageThis multimodal investigation demonstrates that integrating electrical impedance myography with quantitative motor, speech, musculoskeletal imaging, and proteomic assessments provides a sensitive and non-invasive research framework for capturing neuromuscular dysfunction and functional disease burden in patients with ADSS1 myopathy, thereby supporting the current biomarker strategy for refined phenotyping and longitudinal disease monitoring in this ultra-rare condition.

ObjectivesTo screen the entire genome for genes associated with risk for lateral epicondylopathy and improve understanding of underlying biological mechanisms and inform future research aimed at risk stratification and personalized prevention and treatment strategies. MethodsA genome-wide association study was conducted using UK Biobank data. Lateral epicondylopathy cases were identified based on electronic health records from individuals of European ancestry. Logistic regression tested associations between single-nucleotide polymorphisms and disease status, adjusting for sex, age, height, weight and ancestry principal components. Previously-identified candidate genes from the literature were also tested for association with lateral epicondylopathy. ResultsAmong 20,390 cases of lateral epicondylopathy, two loci reached genome-wide significance: one comprising 144 linked SNPs and one single SNP. The first locus, led by rs13127477 (p=7.7x10-12; OR 0.93, 95% CI 0.91 to 0.95), is located near three SIBLING genes (IBSP, MEPE and SPP1) involved in extracellular matrix remodelling at fibrocartilaginous entheses. The risk allele was associated with increased SIBLING gene expression, suggesting that excessive entheseal matrix remodelling contributes to disease susceptibility. The second locus was defined by rs138254824 (p=3.69x10-8; OR 3.42, 95% CI 2.23 to 5.25) near NEDD9 and TMEM170B. Previously reported collagen gene associations were not replicated. ConclusionIn the first genome-wide screen for lateral epicondylopathy, two loci were identified. These loci provide insight regarding the pathophysiology of lateral epicondylopathy and a roadmap for preventing and treating this injury with personalized medicine. Summary BoxO_ST_ABSWhat is already known on this topicC_ST_ABSLateral epicondylopathy is a common and disabling overuse tendon condition, yet its genetic basis has remained poorly characterised, with prior studies limited to small candidate gene analyses. What this study addsThis study provides the first genome-wide association analysis of lateral epicondylopathy, identifying two risk loci on chromosomes 4 and 6 and implicating SIBLING genes (IBSP, MEPE, and SPP1) involved in entheseal extracellular matrix remodelling. How this study might affect research, practice or policyThese findings offer new biological insight into disease susceptibility and challenge previously reported collagen gene associations.

BackgroundPeripheral nerve trauma denervates skeletal muscle resulting in paralysis and atrophy that is reversible if timely reinnervation occurs, due to its regenerative capacity. If reinnervation is delayed muscles regenerative ability is exhausted and resident fibroadipogenic progenitors (FAPs) differentiate into adipocytes and fibroblasts that replace muscle with non-contractile fibrotic tissue and fat, resulting in physical disability. Prostaglandin E2 (PGE2) inhibits adipogenesis and fibrosis in other tissues. We determined whether PGE2 could inhibit fibro-fatty degradation of long-term denervated muscle. MethodsWe utilized the rat tibial nerve transection model, denervating the gastrocnemius and selected a 5 week post-denervation time point to represent short-term muscle denervation injury (reversible with reinnervation), and 12 weeks to represent sustained, irreversible injury. Gastrocnemius FAPs were isolated via FACS and grown in culture to assess endogenous PGE2 production and the proliferative and differentiation response to exogenous PGE2. We evaluated transcript and protein expression of PGE2 synthesizing enzyme PTGS2, PGE2 degrading enzyme 15-PGDH and markers of proliferation, adipogenesis and fibrogenesis using RT-qPCR, immunofluorescence and SDS-PAGE/Western blotting. Paracrine impact of FAPs produced PGE2 was assessed by treating C2C12 myoblasts with FAPs conditioned media. ResultsTranscript expression of PTGS2 was increased and 15-PGDH decreased (4.37{+/-}2.63 and -3.06{+/-}0.85 fold change respectively, p<0.05) in 5 week, but not 12 week denervated gastrocnemius, consistent with increased PGE2 production in 5 week denervated muscle. Similarly, PTGS2 transcript levels were significantly increased (2.58{+/-}0.33 fold change, p<0.05) and 15-PGDH decreased (-5.24{+/-}3.19 fold change, p<0.05) in FAPs isolated from 5 week, but not 12 week denervated muscle, demonstrating that FAPs are a source of PGE2 in short-term denervated muscle. 16,16-dimethyl PGE2 did not impact naive FAPs in vitro proliferation, but significantly inhibited their differentiation as demonstrated by 88.9%, 82.3% and 94.2% decreases in FAPs expression of adipogenic marker perilipin-1, fibrogenic marker -smooth muscle actin (-SMA) and lipid content respectively, mediated via PGE2 binding to the FAPs EP4 receptor. FAPs isolated from 12 week denervated muscle demonstrated increased adipogenesis and fibrogenesis vs. naive FAPs (perilipin-1 and -SMA 7.93{+/-}2.96 and 2.00{+/-}0.33 fold increase respectively, p<0.05) and remained fully susceptible to PGE2 inhibition of fibro-adipogenic differentiation. Conditioned media from FAPs derived from 5 week, but not 12 week, denervated gastrocnemius stimulated C2C12 myoblast proliferation which was prevented by EP4 blockade. ConclusionsPGE2 is identified as a novel negative regulator of FAPs differentiation in traumatically denervated muscle, suggesting the therapeutic potential of PGE2 to prevent fibro-fatty degradation of long-term denervated muscle awaiting reinnervation.

Background and objectivesA pathogenic GGC repeat expansion in the zinc finger homeobox 3 (ZFHX3) gene, encoding a pure polyglycine tract, is the cause of spinocerebellar ataxia type 4 (SCA4). Intermediate expansions of other SCA loci contribute to the risk of amyotrophic lateral sclerosis (ALS), a fatal neurodegenerative disease involving the progressive loss of motor neurons. There is increasing awareness of the role of short tandem repeat (STR) motif composition and configuration in disease pathogenicity. Given the genetic pleiotropy between ALS and SCA, this study aimed to evaluate whether ZFHX3 GGC expansions were associated with ALS and to characterise repeat motif composition. MethodsExpansionHunter v5 was used to genotype ZFHX3 GGC repeat sizes in short-read whole genome sequencing data from people with ALS and healthy controls of European ancestry. Repeat sizes were visually inspected using REViewer v2. Repeat motif configurations of Australian ALS cases were manually derived from REViewer images. Receiver operating characteristic (ROC) curve analysis and Youdens J statistic were performed to find a candidate repeat size threshold for association testing using Fishers exact test. ResultsAnalysis of 5,785 people with ALS and 7,982 healthy controls found no association between ZFHX3 GGC repeat expansions and disease risk. However, more than 30 unique repeat motif compositions were identified across 802 people with ALS. Of these, seven distinct configurations coded a pure polyglycine tract which, when expanded, is canonical to SCA4. DiscussionAlthough no association was observed between ZFHX3 GGC repeat expansions and ALS, this study established the dynamic nature of ZFHX3 repeat motif composition and configuration. Unique motif compositions were identified both within and between repeat sizes, including the presence of pure polyglycine repeats in ALS. Consideration of repeat motif composition and configuration, in addition to repeat allele length, may be important for assessing neurodegenerative disease risk.

IntroductionSuccessful reinnervation following peripheral nerve injury is highly variable, and the molecular programs underlying human muscle degeneration and recovery remain poorly defined. There is a critical need for high-resolution, spatially resolved gene expression data from human skeletal muscle obtained in clinically relevant settings. This study aimed to establish the feasibility of applying spatial transcriptomics to intra-operatively human muscle biopsies and to generate a framework for identifying gene expression signatures associated with reinnervation outcomes. MethodsTo validate the workflow, we collected biopsies intraoperatively from upper-extremity muscles during standard-of-care orthopaedic surgical procedures 5 months after traumatic brachial plexus injury. The flash-frozen biopsy was processed using the 10x Genomics Visium HD high-resolution platform. Quality metrics confirmed high RNA integrity and robust transcript detection at 8 {micro}m resolution. ResultsGenes involved in neuromuscular junction formation, degeneration, and regeneration were identified at subcellular resolution and showed fiber-type-specific expression patterns. Analyses were performed using complementary approaches in Seurat and Loupe Browser. ConclusionsTogether, these findings demonstrate the feasibility of spatial transcriptomics in human muscle, establish baseline gene-expression signatures, and provide a foundation for future studies aimed at identifying biomarkers associated with successful reinnervation and improved nerve-repair strategies.

Dystonia treatment evaluation in cerebral palsy (CP) is limited by the lack of clinician-assessed scales linking dystonia severity to functional impact. We asked 7 pediatric movement disorder specialists to review videos of 27 children with CP while performing an upper extremity task and while walking. Experts rated arm and leg dystonia severity using the Global Dystonia Severity Rating Scale (GDRS) and task-specific functional impact on a five-point scale adapted from the Dyskinetic Cerebral Palsy Functional Impact Scale. Arm GDRS scores correlated with functional impact on the upper extremity task (linear regression R^2=0.48, p=0.0005). Leg GDRS scores correlated with gait impact (R^2=0.43, p=0.001). A four-point increase in total GDRS corresponded to a one-point worsening in combined functional impact. By demonstrating how expert-rated limb dystonia severity correlates with task-specific functional impact in children with CP, these results could help clinically identify functionally-meaningful differences in dystonia severity.

BackgroundIn critically ill patients admitted to the intensive care unit (ICU), rapid skeletal muscle atrophy frequently develops in the acute phase. This ICU-acquired weakness can significantly impair long-term physical function. Although the biceps brachii cross-sectional area (CSA) is commonly used to assess muscle atrophy, its ultrasound imaging can be technically challenging, and the flexor carpi ulnaris may offer a more accessible alternative. Therefore, this study aimed to investigate whether CSA changes of the flexor carpi ulnaris correlate with those of the biceps brachii in critically ill patients admitted to the ICU, as well as whether the flexor carpi ulnaris CSA reflects systemic muscle atrophy in the acute phase of the ICU stay. MethodsTwenty critically ill patients admitted to the ICU underwent serial ultrasound assessment of the biceps brachii and flexor carpi ulnaris CSAs on days 0, 5, 7, and 14 after admission. Longitudinal changes in CSA were analyzed using the Friedman and Wilcoxon signed-rank tests. Correlations between the biceps brachii and flexor carpi ulnaris were examined using Spearmans rank correlation, and structural equation modeling was applied to explore causal relationships between clinical variables and CSA changes. ResultsSignificant CSA reductions were observed in both the flexor carpi ulnaris (-20.6%) and biceps brachii (-16.3%) by day 14, and the relative CSA changes of the biceps brachii and flexor carpi ulnaris showed a moderate positive correlation ({rho} = 0.5489, p = 0.0122). Structural equation modeling analysis revealed that the biceps brachii CSA change had positive effect on that of the flexor carpi ulnaris ({beta} = 0.249, p = 0.0011). Moreover, body mass index was positively associated with the baseline flexor carpi ulnaris CSA ({beta} = 0.042, p = 0.0004). However, the baseline flexor carpi ulnaris CSA was not a significant predictor of subsequent CSA changes. ConclusionUltrasound measurement of the flexor carpi ulnaris CSA offers a practical alternative to that of the biceps brachii for early detection of muscle wasting in ICU patients. Given its anatomical accessibility and high sensitivity to early atrophic changes, it may serve as a feasible screening tool for ICU-acquired weakness and inform timely interventions.

BackgroundDystonia is a debilitating movement disorder that is difficult to assess when co-existing with spasticity, as is typical in cerebral palsy (CP). Querying caregivers about their childrens movements is known to increase clinical dystonia identification. However, beyond identification, determining whether dystonia is the predominant vs. accompanying movement feature in a child with CP can guide clinical decision making, particularly regarding surgical candidacy. ObjectiveTo determine whether caregivers movement descriptions differed between children with predominant dystonia, predominant spasticity with accompanying dystonia, and predominant spasticity without dystonia. MethodsIn this cross-sectional study, we used conventional content analysis to codify caregivers descriptions of triggered involuntary movements in children with CP seen in a tertiary care CP center between 4/2023 and 12/2024. Movement feature frequencies were compared across tone types using Chi-square tests with Bonferroni corrections for multiple comparisons. ResultsOf 180 children with CP (mean age 9.2, 47.8% male), caregivers of children with predominant dystonia (50/180, 27.8%) more frequently described movements triggered by negative emotions (p<0.002) and affecting their back, trunk, and whole body (p<0.04). Caregivers of children with predominant spasticity with dystonia (99/180, 55.0%) more frequently described movements affecting a single limb (p<0.04). Caregivers of children without dystonia (31/180, 17.2%) described movements as being slight or small (p<0.008). These differences persisted even for caregivers unaware their child had dystonia (77/149, 51.6%). ConclusionsCaregivers movement descriptions differ between children with different combinations of dystonia and spasticity, which may help inform clinical management and guide communication with families about dystonia.

ObjectivesEpidural spinal cord stimulation (SCS) is an emerging therapy for motor rehabilitation following spinal cord injury (SCI) and other motor disorders. Conventionally, SCS leads are placed along the dorsal spinal cord (SCSD), where stimulation activates large diameter afferent fibers, which indirectly activate motoneurons through reflex pathways. This leads to broad activation of flexor and extensor muscles and limited fine-tuned control of motor output. Targeting the ventral spinal cord (SCSV) may enable more direct activation of motoneuron pools, potentially improving the specificity of muscle activation; however, there is currently no established method to place leads ventrally. To address this, we evaluated the feasibility of four modified percutaneous implantation techniques to target the ventrolateral thoracolumbar spinal cord. Materials and methodsPercutaneous SCSV implantation was performed in three human cadaver torso specimens under fluoroscopic guidance. The following approaches were evaluated: sacral hiatus, transforaminal, interlaminar contralateral, and interlaminar ipsilateral. The leads in the latter 3 approaches were inserted between L1 and L5. Eighteen implants were attempted, with nine leads retained for analysis. Lead and electrode position were assessed using computed tomography (CT) with three-dimensional reconstruction, along with anatomical dissection to verify lead and electrode placement within the epidural space. ResultsSuccessful ventral epidural lead placement was achieved using all four implantation approaches. The sacral hiatus (16/16 electrodes) and transforaminal (8/8 electrodes) approaches resulted in exclusively ventrolateral placement. The interlaminar contralateral approach led to 27/32 electrodes positioned ventrolaterally and 5/32 dorsally. The interlaminar ipsilateral implantation approach led to 14/32 electrodes positioned ventrolaterally and 18/32 positioned ventromedially. ConclusionsThese findings demonstrate that ventral epidural SCS lead placement can be achieved using modified percutaneous implant techniques. The four approaches outlined here provide a clinically feasible pathway to SCSV and establishes a foundation for future clinical studies investigating SCSV for motor rehabilitation following SCI.

EMG-based muscle force predictions are often inaccurate following active muscle stretch or shortening because of residual force enhancement (rFE) or depression (rFD), respectively, which can alter the neural drive to a muscle. However, the extent of neural drive modulation due to rFE or rFD remains unknown, making it difficult to correct EMG-based force predictions. Therefore, seventeen participants performed dorsiflexion contractions at 20 and 40% of maximum voluntary torque (MVT) in three conditions: stretch-hold, shortening-hold, and fixed-end reference (REF) conditions. The ankle dorsiflexion torques and angles were matched using dynamometry to the REF condition over a 10-s steady state following a 1-s 25{degrees} stretch or shortening, during which we recorded and decomposed tibialis anterior individual motor unit action potentials from high-density surface EMG recordings to gain insights into neural drive. Normalized EMG amplitudes were 2% lower following stretch and 1 or 3% higher following shortening relative to REF at 20 versus 40% MVT (p[&le;].008), respectively. Discharge rates (DRs) from 19 matched motor units per person on average obtained via DEMUSE and MUedit were similar (p=.871). Following stretch and shortening, DRs were [~]1 Hz lower (p[&le;].004) and 0 (p=.966) to 1 Hz higher relative to REF (p=.003), respectively. More unique motor units were also detected following shortening versus REF and in REF versus following stretch. These findings indicate that to account for rFE or rFD, neural drive is respectively decreased or increased via reduced or additional motor unit recruitment and DR modulation, with a contraction-intensity specific discharge rate modulation following active shortening.

Background: Spinal cord injury (SCI) is associated with widespread reorganisation of cortical sensorimotor circuits. Persistent complications such as spasticity and neuropathic pain suggest that homeostatic plasticity, which normally helps stabilise and constrain activity-dependent changes in sensorimotor circuits, may be disrupted after SCI. Homeostatic plasticity can be probed using repeated blocks of transcranial direct current stimulation (tDCS); in healthy individuals, two closely spaced excitatory blocks typically leads to an inhibitory response, reflected as a reduction in corticomotor excitability. Objective: To determine whether individuals with SCI show reduced homeostatic suppression of corticospinal excitability in response to repeated anodal tDCS, compared with healthy controls. Methods: Twenty adults with thoracic or below SCI and 20 healthy controls completed three counterbalanced sessions. Each session comprised two 10-minute blocks of 2 mA tDCS separated by 5 minutes, with the second block always being anodal tDCS over left primary motor cortex. The first block was either anodal, cathodal, or sham tDCS, yielding 3 condition types: anodal-anodal, cathodal-anodal, and sham-anodal. To assess corticomotor excitability, transcranial magnetic stimulation-evoked motor evoked potentials (MEPs) were elicited at baseline, after priming, and every 5 minutes for 60 minutes after the second block. The primary outcome was percent change in MEP amplitude from baseline. Results: In the anodal-anodal condition, the SCI group showed greater facilitation than controls over 0-30 minutes (estimate = 83.09, 95% CI 49.75 to 116.43, p < 0.001), suggestive of a weaker homeostatic response. The cathodal-anodal condition led to a significant overall facilitatory effect with no between-group difference, while the sham-anodal condition showed no change in MEP amplitude relative to baseline. Within the SCI group, exploratory subgroup analysis suggests that those with neuropathic pain and a traumatic injury showed greater facilitation in the anodal-anodal condition than those without these features, indicative of a weaker homeostatic response. Conclusions: SCI is associated with impairment in the homeostatic regulation of corticomotor excitability following repeated excitatory brain stimulation. Disrupted plasticity stabilisation may be relevant to persistent symptoms such as neuropathic pain.

Mitochondrial diseases are a diverse group of inherited neuromuscular disorders leading to progressive disability and early mortality. Mitochondrial myopathy is a common feature of mitochondrial disorders, affecting most patients. Assessment of disease progression and treatment efficacy in mitochondrial disease trials has often relied on muscle biopsies, however, these are increasingly considered unfavourable by patients. Imaging biomarkers of disease could reduce the patient burden, enabling non-invasive longitudinal monitoring of molecular information. Photoacoustic imaging combines the molecular sensitivity of light absorption with the deep tissue imaging capabilities of ultrasound, enabling a safe and fast imaging technique. Tuning the wavelength of light allows for the detection of molecular constituents such as oxy- and deoxy-haemoglobin, lipids, and water. These signatures may reflect underlying pathophysiological alterations and serve as valuable indicators of disease state and progression. We conducted an exploratory study of a photoacoustic imaging dataset in patients with mitochondrial myopathy due to the m.3243A>G mt-tRNALeu mutation and compared to healthy volunteers. We generated photoacoustic measurements at wavelengths in the near infrared, comparing absolute values and ratios derived in the bicep muscle. Confounding factors such as skin colour and sex were considered, and we ensured that these parameters were matched in healthy volunteers and patients. We identified significant differences between patients and controls, revealing changes in ratios between water and total haemoglobin, lipid and total haemoglobin, and lipid and water content. This study highlights the promise of photoacoustic imaging as a novel imaging biomarker in mitochondrial myopathies, paving the way for larger scale studies.

As therapeutic options emerge for hereditary spastic paraplegias (HSP), clinical trials require outcome measures that reflect disease aspects most important to patients. Patient priorities in HSP remain poorly defined. This study aimed to develop a regulatory-compliant framework of patient-prioritised health domains to evaluate treatment response in clinical trials. Patient-reported data on health impacts were collected via two multinational, multilingual online surveys conducted sequentially, including 616 and 504 patients across the clinical and genetic spectrum of HSP. Using a staged approach, we examined prevalence, relevance, and severity, focusing on health impacts that were (i) common (ii) sensitive to disease progression, (iii) highly relevant to patients, and (iv) showed strong severity-relevance correlation. Patient representatives contributed centrally to study design and prioritisation. Our patient-focused analysis yielded five highly prevalent and relevant core health domains: mobility, lower body function, autonomic dysregulation, pain, and psychosocial aspects. Ambulation and lower body function ranked highest across all disease stages. Among non-motor impacts, reduced ability to work, bladder incontinence, and fatigue were most relevant. In mild disease stages, reduced walking distance, reduced walking speed, and the urgency to empty the bladder were the most frequent and most relevant health impact. This work provides the most comprehensive patient-reported and disease stage specific profiling of HSP health impacts to date. It lays the necessary groundwork for developing patient-focused outcome tools capable of capturing treatment effects in future trials.

An overlap syndrome of myositis and/or myocarditis associated with myasthenia gravis (MG) has emerged as a life-threatening immune-related adverse event (irAE) in cancer patients treated with immune checkpoint inhibitors (ICIs). This syndrome closely resembles a rare form of idiopathic inflammatory myopathy (IIM) seen in a subset of MG patients. In this systematic review, we searched PubMed for reports of concurrent MG and IIM as well as ICI-related overlap syndromes. By integrating clinical, serological, and pathological observations, we delineated a previously unrecognized clinicopathological subtype of myositis that overlaps with MG. This entity is defined by a strong association with striational antibodies (StrAbs) and frequent co- occurrence with thymoma as a paraneoplastic process, and we classify it as StrAb-associated myositis. The idiopathic and ICI-induced forms share similar, though not identical, clinical, serological, and histopathological characteristics. We found that AChR antibody positivity, independent of established clinical risk factors such as respiratory or cardiac involvement, predicted more severe ICI-myotoxicity. Together with supporting evidence, our findings suggest a pathogenic model in which thymoma-driven cytotoxic T-cell responses trigger secondary AChR autoimmunity. These results highlight the potential utility of StrAbs and anti-AChR antibodies as practical biomarkers for diagnosis, risk stratification, and early intervention in patients at risk for severe neuromuscular irAEs.

BackgroundSystemic sclerosis (SSc) is a severe autoimmune disease characterised by progressive fibrosis driven by fibroblast activation. Primary cilia, key hubs for profibrotic signalling, are markedly shortened in SSc fibroblasts, but the mechanisms underlying this phenotype remain unclear. This study aimed to define the signalling pathways responsible for primary cilia shortening and fibroblast activation in SSc. MethodsPrimary dermal fibroblasts from SSc patients and healthy controls were analysed for cilia incidence and length by immunofluorescence, profibrotic marker expression by qPCR, and contractility using gel contraction assays. Cells were treated with TGF{beta}1 and pharmacological inhibitors targeting AURKA, HDAC6, ROCK2, and Smad3 signalling. CAV1-silenced fibroblasts were used as an in vitro model of SSc. ResultsMaintenance of the constitutively short primary cilia phenotype in SSc fibroblasts did not require active TGF{beta} signalling. However, TGF{beta}1 induced reversible cilia shortening in healthy fibroblasts and further shortened cilia in SSc fibroblasts to a similar final length, mediated by Rho/ROCK2 rather than canonical Smad3-dependent signalling. Constitutive cilia shortening in SSc was driven by aberrant AURKA activity upstream of HDAC6, promoting ciliary disassembly. Pharmacological inhibition of AURKA or HDAC6 selectively elongated cilia in SSc fibroblasts, reduced profibrotic marker expression, and abrogated fibroblast contractility. CAV1-silenced fibroblasts similarly exhibited constitutive cilia shortening that was reversed by AURKA inhibition without affecting healthy cells. ConclusionsAberrant activation of the AURKA/HDAC6 axis maintains short primary cilia and promotes fibroblast activation in SSc. These findings reveal a mechanistic link between cilia morphology and fibrosis and identify AURKA as a potential therapeutic target for SSc-associated tissue remodelling.

BackgroundChitinases, including chitotriosidase (CHIT1) and chitinase-3-like protein 1 (CHI3L1), are markers of neuroinflammation, a key process in amyotrophic lateral sclerosis (ALS). Tear fluid (TF) can be collected non-invasively and may represent a promising alternative to CSF or blood to study chitinases. MethodsTF was collected from 50 ALS patients and 50 control subjects using Schirmer strips. CHIT1 and CHI3L1 levels in TF, serum, and CSF were quantified using ELISA. Serum NfL was measured using SIMOA. The frequency of a 24 bp-duplication polymorphism in the CHIT1 gene influencing CHIT1 expression was assessed by PCR. ResultsNo group differences in the distribution of the CHIT1 polymorphism were detected. Carriers of the polymorphism in both ALS and controls showed lower CHIT1 levels in serum and TF. CHI3L1 levels in TF were higher in ALS patients compared to controls (p = 0.007), consistent with changes in CSF but not serum. In ALS, males showed higher TF CHIT1-values compared to females (p = 0.009). Combining TF chitinase values with serum NfL values improved discrimination between ALS and controls. ConclusionsChitinases are detectable in TF, and CHI3L1 levels recapitulate changes observed in CSF, highlighting its potential for non-invasive longitudinal assessment. Furthermore, chitinase values in TF, together with serum NfL, may act complementary by capturing distinct aspects of the disease, neuroinflammation and axonal damage. These results suggest TF chitinases and serum NfL could complementarily contribute to the diagnosis and monitoring of the disease, and call for further evaluation of TF as a biomarker source in ALS.

Introduction: Adults with spinal cord injury (SCI) often experience reduced or lost sensation and movement, impairing the ability of the brain to locate paralyzed body parts, which, in turn, compromises sensorimotor recovery. This disruption of the internal body map of the brain, or mental body representations (MBR), also contributes to neuropathic pain in about 69% of adults with SCI. Medications for neuropathic pain are often ineffective and can cause adverse reactions. Our previous pilot clinical trial showed that Cognitive Multisensory Rehabilitation (CMR), a physical therapy that restores MBR, produced significant, lasting reductions in neuropathic pain, improved sensorimotor function, and enhanced brain function. Building on these results, we examined whether 8 weeks of CMR or adaptive fitness (1) improved sensorimotor function and reduced pain; (2) greater brain activity and connectivity related to sensorimotor function and MBR in adults with SCI. Methods: Sixteen participants (52+/-8 years old, 13+/-10 years post-SCI) were randomized to 8 weeks of CMR or adaptive fitness (45 min, 3x/week). Ten participants had neuropathic pain of 3/10 or greater. Pain and sensorimotor function were assessed at baseline, post-intervention, and 3-month follow-up using the Numeric Pain Rating Scale (NPRS), ASIA Impairment Scale (AIS), and Neuromuscular Recovery Scale (NRS). Functional MRI included resting-state and 4 tasks: imagining feeling the left leg, imagining moving the left leg, whole-body movement imagery, and a sensation task. Results: After CMR, participants improved on AIS with large effect sizes (touch: d=1.54; pinprick: d=1.83; lower limb motor function: d=1.32), while adaptive fitness had small/moderate effects (touch: d=0.49; pinprick: d=0.53; lower limb motor function: d=0.74). CMR also showed larger effect sizes for NRS (core: d=2.19; upper limb: d=0.69; lower limb: d=0.74) than fitness (core: d=0.73; upper limb: d=0.34; lower limb: d=0.00). Benefits persisted at follow-up. Highest neuropathic pain intensity reduced post-CMR and at 3-month follow-up (d=0.48; d=0.63). Pain increased slightly after fitness (n=6; d=-0.19; d=-0.41). CMR increased brain connectivity and activation during the leg imagery task. Increased activation during whole-body imagery was greater after CMR than fitness. Discussion: These preliminary results support the potential of CMR to improve function and reduce neuropathic pain in adults with SCI, warranting larger confirmatory trials. Clinicaltrial.gov: NCT05167032

BackgroundPeri-synaptic astrocyte processes (PAPs) play a fundamental role in synapse formation and function. Central afferent synapse loss and astrocyte dysfunction greatly impede sensory-motor circuitry in spinal muscular atrophy (SMA) disease progression, however mechanisms underpinning tripartite synapse dysfunction remains to be fully elucidated. The aims of this study were to further define PAP and motor neuron synaptic defects in human SMA disease pathology and implement a therapeutic intervention strategy to improve motor neuron function. MethodsWe derived astrocyte monocultures and motor neuron astrocyte co-cultures from healthy and SMA patient induced pluripotent stem cell (iPSC) lines to assess intrinsic astrocyte filopodia defects and phenotypes occurring at the synapse-PAP interface, respectively, using cell surface capture mass spectrometry proteomics, confocal and super resolution microscopy, synaptogliosome isolation, and electrophysiology. ResultsSMA astrocytes demonstrated intrinsic filopodia actin defects featuring low abundance of actin-associated cell surface N-glycoproteins, and decreased filopodia density and CDC42-GTP levels after actin remodeling stimulation. This phenotype is likely driven by the significant reduction of CD44 and phosphorylated ezrin, radixin and moesin ERM proteins (pERM) within SMA astrocyte filopodia. The dual combination of SMN1 gene therapy and forskolin treatment, an adenylyl cyclase activator leading to increased cyclic adenosine monophosphate (cAMP) levels and actin signaling pathway stimulation, led to extensive branching and increased filopodia density of SMA astrocytes during actin remodeling. SMA patient-derived motor neuron and astrocyte co-cultures, particularly samples derived from male patient iPSC lines, demonstrated a significant decrease in synapse number, actin-associated pre-synaptic neurotransmitter release protein, synapsin I (SYN1), and PAP-associated expression of pERM and glutamate transporter, EAAT1. Our astrocyte-targeted SMN1 augmentation and forskolin treatment paradigm restored SYN1 protein levels within the SMA synaptogliosome, resulting in significant increases in motor neuron synapse formation and function, but did not fully restore PAP-associated proteins levels at the synapse. ConclusionsSMA astrocytes demonstrate intrinsic actin-associated defects within filopodia, which correlates with decreased pERM levels at tripartite motor neuron synapses. We also define a SMN- and cAMP-targeted treatment paradigm that significantly increases pre-synaptic neurotransmitter release protein levels to improved SMA motor neuron synapse formation and function. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=117 SRC="FIGDIR/small/714618v1_ufig1.gif" ALT="Figure 1"> View larger version (44K): org.highwire.dtl.DTLVardef@1257ab8org.highwire.dtl.DTLVardef@19c0010org.highwire.dtl.DTLVardef@c84552org.highwire.dtl.DTLVardef@3f1e62_HPS_FORMAT_FIGEXP M_FIG C_FIG

Neurodegenerative diseases often feature a prolonged presymptomatic phase during which pathological processes evolve before overt clinical manifestation. In Amyotrophic lateral sclerosis (ALS), defining this prodromal period is critical for identifying early disease features and the optimal window for intervention, yet it remains poorly characterised. In this cross-sectional study, we compared 475 ALS patients with 285 controls recruiting across 20 ALS expert centres in Germany and Switzerland. Participants completed a structured digital questionnaire capturing prodromal complaints, healthcare utilisation, comorbidities, lifestyle factors, and weight changes during the 10 years preceding ALS symptom onset. ALS patients reported substantially higher burden of prodromal complaints than controls (OR=7.50, 95% CI 4.27-13.17; P < 0.001; Padj < 0.001), particularly neuro-motor, sensory, and pain-related symptoms. Prior to symptom onset, ALS patients more frequently consulted neurologists (OR=1.26, CI 1.10-1.44; P < 0.001; Padj = 0.007). Speech therapy consultations were significantly more common among female patients (OR = 2.35, CI 1.05-5.28; P = 0.038) and those with bulbar-onset ALS (OR = 8.67, CI 3.80-19.77; P < 0.001). Prodromal musculoskeletal dysfunction was more frequently reported by ALS patients and exhibited sex- and site-specific patterns. Herniated discs were reported more often by male ALS patients (OR=2.21, CI 1.04-4.68; P = 0.038) and by those with spinal-onset disease (OR=2.32, CI 1.38-3.93; P = 0.002). ALS patients more often completed lower secondary education (OR=1.93, CI 1.24-3.01; P = 0.004; Padj = 0.020) and were more likely to have worked in physically demanding occupations (OR=2.21, CI 1.42-3.43; P < 0.001; Padj = 0.003). Lifestyle factors differed significantly, with higher prior consumption of caffeine (OR=7.21, CI 3.27-15.89; P < 0.001; Padj < 0.001), alcohol (OR=2.25, CI 1.47-3.43; P < 0.001; Padj = 0.002), and cigarettes (OR=1.64, CI 1.20-2.24; P = 0.002) among ALS patients (Padj = 0.011). Weight trajectories differed by sex (P = 0.009), with male ALS patients showing significant loss already during the pre-onset phase (P < 0.001). These findings demonstrate that ALS is preceded by a distinct prodromal phase characterised by mild motor impairment, altered healthcare engagement, and sex- and site-specific patterns in comorbidities, lifestyle, and metabolic change. Characterising these early features of ALS may facilitate earlier diagnosis and enable timely enrolment in clinical trials.