Citations

Abstract Objective Myositis is a heterogeneous family of inflammatory myopathies. We sought to define the differential expression of cytokines, cytokine receptors and immune checkpoint genes in muscle biopsies from patients with different forms of myositis in order to characterize patterns of inflammation in each. Methods Bulk RNA-sequencing was performed on muscle biopsy samples from 669 patients, including 105 with DM, 80 with immune-mediated necrotizing myopathy (IMNM), 65 with anti-synthetase syndrome, 53 with IBM, 19 with anti-PM/Scl myositis, 310 with other inflammatory or genetic myopathies and 37 controls with normal tissue (NT). Myositis clinical groups and autoantibody subgroups were analysed separately. Expression data were analysed for 338 genes encoding cytokines, cytokine receptors and immune checkpoints. Myositis group-specific genes were identified from this list by finding genes that were specifically differentially expressed in one group compared with all samples and compared with NT (α < 0.001). Results IBM patients had the most differentially overexpressed genes (71) among all clinical groups, including 37 that were IBM-specific. Among the top genes were several involved in type 1 inflammation, including CCL5, CXCR3, CCR5, CXCL9 and IFNG. Anti-Jo1 and anti-PM/Scl patients exhibited differential overexpression of a similar set of genes, while DM patients exhibited differential overexpression of a different set of genes involved in type 1 inflammation. IMNM patients had the least number of differentially overexpressed genes with no predominant inflammatory pattern. Conclusion Each myositis clinical group and autoantibody subgroup had differentially overexpressed inflammatory mediators, including a strong type 1 inflammatory gene signature in IBM.

ABSTRACTBackgroundIdiopathic inflammatory myopathies, beyond inclusion body myositis (IBM), have demonstrated an increased risk of adverse cardiovascular outcomes, particularly myocardial infarction (MI). This study evaluated the risk of cardiovascular disease in IBM.MethodsWe conducted a non‐concurrent cohort study utilizing the expanded Rochester Epidemiologic Project, including 50 patients with IBM, matched 1:6 to age‐, sex‐, and calendar year‐matched referents without IBM. Baseline cardiovascular risk factors were recorded. Differences in baseline covariates were adjusted by the inverse probability of treatment weighting method. Participants were followed from the index date forward to determine relative risks (RR) and hazard ratios (HR) for the development of cardiovascular outcomes including MI, ischemic stroke, cardiomyopathy, congestive heart failure (CHF), and peripheral vascular disease (PVD).Results50 patients with IBM and 294 matched population referents were included. Baseline cardiovascular risk factors were similar between groups. Aspirin use was more common (28% vs. 18%, p = 0.03) and statin use less common (26% vs. 38%, p = 0.04) in IBM versus referents. Patients with IBM had an increased hazard of MI compared to referents [HR: 5.79, 95% CI (2.51, 13.36)]. The risk of MI remained consistently elevated across all models, after accounting for potential confounders. For PVD, 16/50 IBM patients versus 16/287 referents were excluded due to pre‐existing PVD at index (p < 0.001). Among remaining participants, RR for PVD was 2.38 (0.82, 6.9). IBM was not associated with an increased risk of ischemic stroke, cardiomyopathy, or CHF.ConclusionsIBM is associated with increased risk of MI compared to population referents. Heightened cardiovascular monitoring and prevention strategies are needed in IBM.

Abstract Objectives IBM is characterized by slowly progressive muscle weakness making it challenging to detect significant changes in weakness during a clinical trial. Trial participants receiving placebo may behave differently from in natural history studies. We aimed to quantify the change in muscle strength and IBM Functional Rating Scale (IBMFRS) of IBM patients receiving placebo during clinical trials. Methods Several databases were searched. Randomized, double-blinded, placebo-controlled trials without treatment intervention on the placebo group were included. Standardized mean differences (SMD) for change in muscle strength and mean differences for IBMFRS were used to calculate pooled effects, using DerSimonian-Laird continuous random effect models. Meta-regression determined change in muscle strength. Heterogeneity was evaluated using the I2 indicator. Results Eleven eligible trials were identified with 257 participants receiving placebo and a low risk of bias per the Cochrane Collaboration Risk of Bias 2 (RoB2) tool. Participants receiving placebo on average had a measurable decline in muscle strength with a mean effect size of –0.398 (95% CI –0.652, –0.144) (P = 0.002). SMD changed by –0.009 (–0.016, –0.002) points per week (P = 0.015). Manual muscle testing was associated with higher heterogeneity (I2 = 67.68%) compared with quantitative muscle testing (I2 = 0%). Only three studies reported IBMFRS results. The pooled change in IBMFRS at 12 months was –2.189 points (–3.893, –0.485) on this 0 to 40-point scale (P = 0.012), with relatively high heterogeneity. Conclusion Participants with IBM displayed a measurable decline in their muscle strength and IBMFRS during clinical trials, in keeping with the disease’s slowly progressive nature. These estimates can inform sample size calculations in future studies.

Abstract Nerve conduction F-wave studies contain crucial information about subclinical motor dysfunction that can be used to diagnose patients with amyotrophic lateral sclerosis (ALS). However, F-wave responses are highly variable in morphology, making waveform interpretation challenging. Artificial intelligence techniques can extract time–frequency features to provide new insights into ALS diagnosis and prognosis. A retrospective analysis was performed on F-wave responses from 46 802 patients. Discrete wavelet transforms were applied to time-series waveform responses after stimulating ulnar, median, fibular and tibial nerves. Wavelet coefficient statistics, onset age, sex and body mass index were features for training a Gradient Boosting Machine model on 40 095 patients (5329 diagnosed with motor neuron disease). Model performance was tested on responses from 689 ALS patients meeting Gold Coast criteria and 689 age- and sex-matched controls. An exploratory analysis examined model performance on cohorts of patients with inclusion body myositis, cervical radiculopathy, lumbar radiculopathy or peripheral neuropathy, which can mimic ALS symptoms. Factors affecting survival were estimated through Cox proportional hazards regression. The model trained using wavelet features on the full waveform had 90% recall, 87% precision and 88% accuracy. Similar model performance was measured using features from only the M-wave or F-wave. Classification probabilities for ALS patients were statistically different from the diagnoses mimicking ALS symptoms (P &lt; 0.001, ANOVA, Tukey’s post hoc test). Higher model classification probabilities of ALS, older age at onset, and family history of ALS alone or with frontotemporal dementia were factors decreasing survival. Longer diagnostic delay and upper limb onset site were factors increasing survival. Model scores two standard deviations below the mean had 4 months increased survival (two standard deviations below had 3 months decreased survival). Artificial intelligence techniques extracted important information from F-wave responses to estimate a patient’s likelihood of ALS and their survival risks. Although the model can make predictions at a specific decision threshold as presented here, the true strength of such a model lies in its ability to provide probabilities about whether a patient is likely to have ALS in comparison to other mimicking diagnoses, such as inclusion body myositis, cervical or lumbar radiculopathy or peripheral neuropathy. These probabilities provide clinicians with additional information that they can use to make the final diagnosis with greater confidence and precision. Integrating such a model into the clinical workflow could help clinicians to diagnose ALS sooner and manage treatment based on estimated survival, which might improve outcomes and the quality of life of patients.

ABSTRACT Background Inclusion body myositis (IBM) is the most prevalent muscle disease in adults for which no current treatment exists. The pathogenesis of IBM remains poorly defined. In this study, we aimed to explore the interplay between inflammation and mitochondrial dysfunction in IBM. Methods The study population consisted of 38 IBM patients and 22 age‐ and sex‐matched controls without a myopathy. Mean age was 62.9 years (SD = 9) in IBM group and 59.7 (10) in controls. Bulk RNA sequencing, Meso Scale Discovery electrochemiluminescence (ECL), western blotting, histochemistry and immunohistochemistry were performed on frozen muscle samples from the study participants. Results We demonstrated activation of the NLRP3 inflammasome in IBM muscle samples, with the NLRP3 inflammasome being the most upregulated pathway on RNA sequencing, along with increased expression of NLRP3 and ASC proteins in IBM group. NLRP3 RNA levels most strongly correlated with TLR7 (correlation coefficient ρ = 0.91) and complement activation‐related genes, and inversely correlated with several mitochondria‐related genes among others. On muscle histopathology, there was increased NRLP3 immunoreactivity in both inflammatory cells and muscle fibres. Mitophagy is critical for removing damaged mitochondria and preventing the formation of a vicious cycle of mitochondrial dysfunction—NLRP3 inflammasome activation. Herein, we showed altered mitophagy, as witnessed by the elevated levels of p‐S65‐Ubiquitin, a mitophagy marker, in muscle lysates from IBM patients compared to controls (median of 114.3 vs. 81.25 ECL units, p = 0.005). The p‐S65‐Ubiquitin levels were most significantly elevated in IBM males compared to male controls (136 vs. 83.5 ECL units; p = 0.013), whereas IBM females had milder nonsignificant elevation compared to female controls (97.25 vs. 69 ECL units, p = 0.31). On muscle histopathology, p‐S65‐Ubiquitin aggregates accumulated in muscle fibres that were mostly Type 2 and devoid of cytochrome‐c‐oxidase reactivity. NLRP3 RNA levels correlated with p‐S65‐Ubiquitin levels in both sexes (males: ρ = 0.48, females: ρ = 0.54) but with loss of muscle strength, as reflected by the manual motor test score, only in males (males: ρ = 0.62, females: ρ = −0.14). Lastly, we identified sex‐specific molecular pathways in IBM. Females had upregulation of pathways related to response to stress, which could conceivably offset some of the pathomechanisms of IBM, while males had upregulation of pathways related to cell adhesion and migration. Conclusions There is activation of the NLRP3 inflammasome in IBM, along with altered mitophagy, particularly in males, which is of potential therapeutic significance. These findings suggest sex‐specific mechanisms in IBM that warrant further investigation.