Non-Invasive Respiratory Assessment in Duchenne Muscular Dystrophy: From Clinical Research to Outcome Measures

Improved diagnostic performance of high-sensitivity cardiac troponins in muscle dystrophies using comprehensive definition criteria for cardiac involvement: A longitudinal study on 35 patients

BACKGROUND AND PURPOSE

Sparse information is available on the correct interpretation of elevated high-sensitivity cardiac troponin (hs-cTn) in confirmed muscular dystrophies.

METHODS

Serum concentrations of hs-cTn T (hs-cTnT) and hs-cTn I (hs-cTnI) were determined in 35 stable outpatients with confirmed skeletal muscle dystrophies. We calculated sensitivities, specificities, and positive and negative predictive values of hs-cTnT and hs-cTnI for identification of cardiac involvement using a comprehensive definition that included diastolic left ventricular and right ventricular function, strain analysis using two-dimensional transthoracic echocardiogram and magnetic resonance imaging, myocardial biopsies, and consideration of a variety of triggers for cardiac injury, including arrhythmias, conduction disorders, and hypoxemia due to respiratory failure.

RESULTS

Cardiac involvement was diagnosed in 34 of 35 cases. Specificities of hs-cTnT increased from 12.5% to 100% (p = 0.0006) applying the comprehensive definition compared to a definition based on electrocardiography and echocardiography alone. At the recommended 99th percentile upper limit of normal, sensitivities were significantly lower for hs-cTnI than for hs-cTnT (29.4% vs. 100%, p = 0.0164). Conversely, the specificities of hs-cTnT and hs-cTnI increased to 100% when using the comprehensive definition criteria for diagnosing cardiac involvement.

CONCLUSIONS

Elevated hs-cTnT but not hs-cTnI discriminates cardiac involvement in cases with confirmed skeletal muscle dystrophies with very high sensitivity and 100% specificity. Prior reports on worse performance may be explained by the use of less sensitive imaging methods or incomplete assessment of cardiac involvement.

Interpretation of elevated baseline concentrations and serial changes of high-sensitivity cardiac troponin T in confirmed muscular dystrophies

AIMS

Concentrations of high-sensitivity cardiac troponin T (hs-cTnT) are frequently elevated in stable patients with confirmed muscle dystrophies. However, sparse information is available on the interpretation of serial concentration changes.

METHODS

Hs-cTnT was collected in 35 stable outpatients with confirmed skeletal muscle dystrophies at 0 and 1 h and after 6-12 months during scheduled outpatient visits. We simulated the effectiveness of the European Society of Cardiology (ESC) 0/1 h algorithm and assessed biological variation at 6-12 months using two established methods: reference change value (RCV) and minimal important difference (MID).

RESULTS

Median baseline hs-cTnT concentrations were 34.4 ng/L [inter-quartile range (IQR): 17.5-46.2], and values > 99th percentile upper limit of normal were present in 34 of 35 patients. All patients were stable without cardiovascular adverse events during a follow-up of 6.6 months (IQR: 6-7). Median concentration change was 1.9 ng/L (IQR: 0.7-3.2) and 0.8 ng/L (IQR: 0-7.0) at 60 min and 6-9 months, respectively. Applying the criteria of the ESC 0/1 h algorithm for triage of suspected acute coronary syndrome (ACS) showed poor overall effectiveness of baseline hs-cTnT values. No patient would qualify for rule-out based on hs-cTnT less than the limit of detection, whereas five cases would qualify for rule-in based on hs-cTnT ≥ 52 ng/L. Biological variabilities at 6-12 months per MID and RCV were 1.2 ng/L [95% confidence interval (CI): 0.7-2.1] and 28.6% (95% CI: 27.9-29.6), respectively. A total of 8 (22.9%) and 25 (71.4%) cases exceeded the biological variation range, suggesting some additional myocardial damage.

CONCLUSIONS

The high prevalence of elevated hs-cTnT could negatively impact the effectiveness of rule-out and rule-in strategies based on a single hs-cTnT value. Knowledge of the physiological and biological variation of hs-cTnT after 6-12 months is helpful to detect the progression of cardiac involvement or to search for cardiac complications including but not limited to arrhythmias that may trigger acute or chronic myocardial damage.

Lipin1 as a therapeutic target for respiratory insufficiency of duchenne muscular dystrophy

In Duchenne muscular dystrophy (DMD), diaphragm muscle dysfunction results in respiratory insufficiency which is a leading cause of death in patients. Mutations to the dystrophin gene result in myocyte membrane instability, contributing to the structural deterioration of the diaphragm muscle tissues. With previous works suggesting the importance of lipin1 for maintaining skeletal muscle membrane integrity, we explored the roles of lipin1 in the dystrophic diaphragm. We found that the protein expression levels of lipin1 were reduced by 60% in the dystrophic diaphragm. While further knockdown of lipin1 in the dystrophic diaphragm leads to increased necroptosis, restoration of lipin1 in the dystrophic diaphragm results in reduced inflammation and fibrosis, decreased myofiber death, and improved respiratory function. Our results demonstrated that lipin1 restoration improved respiratory function by enhancing membrane integrity and suggested that lipin1 could be a potential therapeutic target for preventing respiratory insufficiency and respiratory failure in DMD. Continued investigation is required to better understand the mechanisms behind these findings, and to determine the role of lipin1 in maintaining muscle membrane stability.

Community-based respiratory health measures in children and young people with cerebral palsy: A scoping review

AIM

To identify, map, and describe outcome measurement domains and instruments used within a community setting to assess respiratory health in children and young people aged 1 to 18 years, diagnosed with cerebral palsy (CP).

METHOD

A scoping review methodology informed structured searches in nine databases, grey literature, and registries, conducted in August 2021 (updated in February 2023). Articles were screened for eligibility by two independent researchers. Any outcome measurement instruments used to assess respiratory health or associated impact were extracted, categorized, and mapped to health and health-related domains of the International Classification of Functioning, Disability, and Health.

RESULTS

Seventy-six outcome measurement instruments were identified across 78 articles worldwide between 1970 and 2023. These were categorized into 'Body functions and structures' (n = 20), 'Activity and performance' (n = 22), and 'Participation and quality of life' (n = 19), with a further 15 mapped to 'Health care resources use'.

INTERPRETATION

No consensus of 'what' to measure and 'how' to measure respiratory health in children and young people with CP was found. Moreover, many measures were not replicable in individuals with more severe forms of CP, excluding those at increased risk of respiratory-related morbidity and mortality. Further research is required to agree important outcome domains and associated measures in research and clinical practice.

WHAT THIS PAPER ADDS

A limited number and size of experimental designs were found. Seventy-six measures were identified to assess respiratory health in cerebral palsy. No consensus was found in 'what' or 'how' to measure respiratory health. Many measures were not replicable in children and young people at risk of poorer respiratory health outcomes. Children and young people with comorbidities and learning disability were frequently excluded from studies.

How Can Proteomics Help to Elucidate the Pathophysiological Crosstalk in Muscular Dystrophy and Associated Multi-System Dysfunction?

This perspective article is concerned with the question of how proteomics, which is a core technique of systems biology that is deeply embedded in the multi-omics field of modern bioresearch, can help us better understand the molecular pathogenesis of complex diseases. As an illustrative example of a monogenetic disorder that primarily affects the neuromuscular system but is characterized by a plethora of multi-system pathophysiological alterations, the muscle-wasting disease Duchenne muscular dystrophy was examined. Recent achievements in the field of dystrophinopathy research are described with special reference to the proteome-wide complexity of neuromuscular changes and body-wide alterations/adaptations. Based on a description of the current applications of top-down versus bottom-up proteomic approaches and their technical challenges, future systems biological approaches are outlined. The envisaged holistic and integromic bioanalysis would encompass the integration of diverse omics-type studies including inter- and intra-proteomics as the core disciplines for systematic protein evaluations, with sophisticated biomolecular analyses, including physiology, molecular biology, biochemistry and histochemistry. Integrated proteomic findings promise to be instrumental in improving our detailed knowledge of pathogenic mechanisms and multi-system dysfunction, widening the available biomarker signature of dystrophinopathy for improved diagnostic/prognostic procedures, and advancing the identification of novel therapeutic targets to treat Duchenne muscular dystrophy.

Safety and Efficacy of DT-DEC01 Therapy in Duchenne Muscular Dystrophy Patients: A 12 - Month Follow-Up Study After Systemic Intraosseous Administration

Duchenne Muscular Dystrophy (DMD) is a progressive and fatal muscle-wasting disease with no known cure. We previously reported the preliminary safety and efficacy up to six months after the administration of DT-DEC01, a novel Dystrophin Expressing Chimeric (DEC) cell therapy created by fusion of myoblasts of DMD patient and the normal donor. In this 12-month follow-up study, we report on the safety and functional outcomes of three DMD patients after the systemic intraosseous administration of DT-DEC01. The safety of DT-DEC01 was confirmed by the absence of Adverse Events (AE) and Severe Adverse Events (SAE) up to 21 months after intraosseous DT-DEC01 administration. The lack of presence of anti-HLA antibodies and Donors Specific Antibodies (DSA) further confirmed DT-DEC01 therapy safety. Functional assessments in ambulatory patients revealed improvements in 6-Minute Walk Test (6MWT) and timed functions of North Star Ambulatory Assessment (NSAA). Additionally, improvements in PUL2.0 test and grip strength correlated with increased Motor Unit Potentials (MUP) duration recorded by Electromyography (EMG) in both ambulatory and non-ambulatory patients. DT-DEC01 systemic effect was confirmed by improved cardiac and pulmonary parameters and daily activity recordings. This follow-up study confirmed the safety and preliminary efficacy of DT-DEC01 therapy in DMD-affected patients up to 12 months after intraosseous administration. DT-DEC01 introduces a novel concept of personalized myoblast-based cellular therapy that is irrespective of the mutation type, does not require immunosuppression or the use of viral vectors, and carries no risk of off target mutations. This establishes DT-DEC01 as a promising and universally effective treatment option for all DMD patients.

Monitoring and Management of Respiratory Function in Pompe Disease: Current Perspectives

Pompe disease (PD) is a neuromuscular disorder caused by a deficiency of acid alpha-glucosidase (GAA) - a lysosomal enzyme responsible for hydrolyzing glycogen. GAA deficiency leads to accumulation of glycogen in lysosomes, causing cellular disruption. The severity of PD is directly related to the extent of GAA deficiency - if no or minimal GAA is produced, symptoms are severe and manifest in infancy, known as infantile onset PD (IOPD). If left untreated, infants with IOPD experience muscle hypotonia and cardio-respiratory failure leading to significant morbidity and mortality in the first year of life. In contrast, late-onset PD (LOPD) patients have more GAA activity and present later in life, but also have significant respiratory function decline. Despite FDA-approved enzyme replacement therapy, respiratory insufficiency remains a major cause of morbidity and mortality, emphasizing the importance of early detection and management of respiratory complications. These complications include impaired cough and airway clearance, respiratory muscle weakness, sleep-related breathing issues, and pulmonary infections. This review aims to provide an overview of the respiratory pathology, monitoring, and management of PD patients. In addition, we discuss the impact of novel approaches and therapies on respiratory function in PD.

Perfluorocarbons: A perspective of theranostic applications and challenges

Perfluorocarbon (PFC) are biocompatible compounds, chemically and biologically inert, and lacks toxicity as oxygen carriers. PFCs nanoemulsions and nanoparticles (NPs) are highly used in diagnostic imaging and enable novel imaging technology in clinical imaging modalities to notice and image pathological and physiological alterations. Therapeutics with PFCs such as the innovative approach to preventing thrombus formation, PFC nanodroplets utilized in ultrasonic medication delivery in arthritis, or PFC-based NPs such as Perfluortributylamine (PFTBA), Pentafluorophenyl (PFP), Perfluorohexan (PFH), Perfluorooctyl bromide (PFOB), and others, recently become renowned for oxygenating tumors and enhancing the effects of anticancer treatments as oxygen carriers for tumor hypoxia. In this review, we will discuss the recent advancements that have been made in PFC's applications in theranostic (therapeutics and diagnostics) as well as assess the benefits and drawbacks of these applications.