δ-Sarcoglycan-deficient muscular dystrophy: from discovery to therapeutic approaches

Mutations in the δ-sarcoglycan gene cause limb-girdle muscular dystrophy 2F (LGMD2F), an autosomal recessive disease that causes progressive weakness and wasting of the proximal limb muscles and often has cardiac involvement. Here we review the clinical implications of LGMD2F and discuss the current understanding of the putative mechanisms underlying its pathogenesis. Preclinical research has benefited enormously from various animal models of δ-sarcoglycan deficiency, which have helped researchers to explore therapeutic approaches for both muscular dystrophy and cardiomyopathy

Long-Term Blocking of Calcium Channels in mdx Mice Results in Differential Effects on Heart and Skeletal Muscle

The disease mechanisms underlying dystrophin-deficient muscular dystrophy are complex, involving not only muscle membrane fragility, but also dysregulated calcium homeostasis. Specifically, it has been proposed that calcium channels directly initiate a cascade of pathological events by allowing calcium ions to enter the cell. The objective of this study was to investigate the effect of chronically blocking calcium channels with the aminoglycoside antibiotic streptomycin from onset of disease in the mdx mouse model of Duchenne muscular dystrophy (DMD)

Peri-operative red blood cell transfusion in neonates and infants: NEonate and Children audiT of Anaesthesia pRactice IN Europe: A prospective European multicentre observational study

BACKGROUND: Little is known about current clinical practice concerning peri-operative red blood cell transfusion in neonates and small infants. Guidelines suggest transfusions based on haemoglobin thresholds ranging from 8.5 to 12 g dl-1, distinguishing between children from birth to day 7 (week 1), from day 8 to day 14 (week 2) or from day 15 (≥week 3) onwards. OBJECTIVE: To observe peri-operative red blood cell transfusion practice according to guidelines in relation to patient outcome. DESIGN: A multicentre observational study. SETTING: The NEonate-Children sTudy of Anaesthesia pRactice IN Europe (NECTARINE) trial recruited patients up to 60 weeks' postmenstrual age undergoing anaesthesia for surgical or diagnostic procedures from 165 centres in 31 European countries between March 2016 and January 2017. PATIENTS: The data included 5609 patients undergoing 6542 procedures. Inclusion criteria was a peri-operative red blood cell transfusion. MAIN OUTCOME MEASURES: The primary endpoint was the haemoglobin level triggering a transfusion for neonates in week 1, week 2 and week 3. Secondary endpoints were transfusion volumes, 'delta haemoglobin' (preprocedure - transfusion-triggering) and 30-day and 90-day morbidity and mortality. RESULTS: Peri-operative red blood cell transfusions were recorded during 447 procedures (6.9%). The median haemoglobin levels triggering a transfusion were 9.6 [IQR 8.7 to 10.9] g dl-1 for neonates in week 1, 9.6 [7.7 to 10.4] g dl-1 in week 2 and 8.0 [7.3 to 9.0] g dl-1 in week 3. The median transfusion volume was 17.1 [11.1 to 26.4] ml kg-1 with a median delta haemoglobin of 1.8 [0.0 to 3.6] g dl-1. Thirty-day morbidity was 47.8% with an overall mortality of 11.3%. CONCLUSIONS: Results indicate lower transfusion-triggering haemoglobin thresholds in clinical practice than suggested by current guidelines. The high morbidity and mortality of this NECTARINE sub-cohort calls for investigative action and evidence-based guidelines addressing peri-operative red blood cell transfusions strategies. TRIAL REGISTRATION: ClinicalTrials.gov, identifier: NCT02350348

Connecting real-world digital mobility assessment to clinical outcomes for regulatory and clinical endorsement–the Mobilise-D study protocol

Background: The development of optimal strategies to treat impaired mobility related to ageing and chronic disease requires better ways to detect and measure it. Digital health technology, including body worn sensors, has the potential to directly and accurately capture real-world mobility. Mobilise-D consists of 34 partners from 13 countries who are working together to jointly develop and implement a digital mobility assessment solution to demonstrate that real-world digital mobility outcomes have the potential to provide a better, safer, and quicker way to assess, monitor, and predict the efficacy of new interventions on impaired mobility. The overarching objective of the study is to establish the clinical validity of digital outcomes in patient populations impacted by mobility challenges, and to support engagement with regulatory and health technology agencies towards acceptance of digital mobility assessment in regulatory and health technology assessment decisions. Methods/design: The Mobilise-D clinical validation study is a longitudinal observational cohort study that will recruit 2400 participants from four clinical cohorts. The populations of the Innovative Medicine Initiative-Joint Undertaking represent neurodegenerative conditions (Parkinson’s Disease), respiratory disease (Chronic Obstructive Pulmonary Disease), neuro-inflammatory disorder (Multiple Sclerosis), fall-related injuries, osteoporosis, sarcopenia, and frailty (Proximal Femoral Fracture). In total, 17 clinical sites in ten countries will recruit participants who will be evaluated every six months over a period of two years. A wide range of core and cohort specific outcome measures will be collected, spanning patient-reported, observer-reported, and clinician-reported outcomes as well as performance-based outcomes (physical measures and cognitive/mental measures). Daily-living mobility and physical capacity will be assessed directly using a wearable device. These four clinical cohorts were chosen to obtain generalizable clinical findings, including diverse clinical, cultural, geographical, and age representation. The disease cohorts include a broad and heterogeneous range of subject characteristics with varying chronic care needs, and represent different trajectories of mobility disability. Discussion: The results of Mobilise-D will provide longitudinal data on the use of digital mobility outcomes to identify, stratify, and monitor disability. This will support the development of widespread, cost-effective access to optimal clinical mobility management through personalised healthcare. Further, Mobilise-D will provide evidence-based, direct measures which can be endorsed by regulatory agencies and health technology assessment bodies to quantify the impact of disease-modifying interventions on mobility. Trial registration: ISRCTN12051706

Peptide-conjugated phosphodiamidate oligomer-mediated exon skipping has benefits for cardiac function in <i>mdx</i> and <i>Cmah-/-mdx</i> mouse models of Duchenne muscular dystrophy

<div><p>Cardiac failure is a major cause of mortality in patients with Duchenne muscular dystrophy (DMD). Antisense-mediated exon skipping has the ability to correct out-of-frame mutations in DMD to produce truncated but functional dystrophin. Traditional antisense approaches have however been limited by their poor uptake into cardiac muscle. The addition of cell-penetrating peptides to antisense molecules has increased their potency and improved their uptake into all muscles, including the heart. We have investigated the efficacy of the Peptide-conjugated phosphodiamidate morpholino oligomer (P-PMO) Pip6a-PMO, for restoration of cardiac dystrophin and functional rescue in DMD mice- the <i>mdx</i> mouse and the less well characterised <i>Cmah-/-mdx</i> mouse (which carry a human-like mutation in the mouse Cmah gene as well as a mutation in DMD). In our first study male mdx mice were administered Pip6a-PMO, i.v, fortnightly from 12 to 30 weeks of age alongside mock-injected age-matched mdx and <i>C57BL10</i> controls. Mice received 4 doses of 18 mg/kg followed by 8 doses of 12.5 mg/kg. The cardiac function of the mice was analysed 2 weeks after their final injection by MRI followed by conductance catheter and their muscles were harvested for dystrophin quantification. In the second study, male <i>Cmah-/-mdx</i> mice, received 12.5 mg/kg Pip6a-PMO, i.v fortnightly from 8 to 26 weeks and assessed by MRI at 3 time points (12, 18 and 28 weeks) alongside mock-injected age-matched mdx, <i>C57BL10</i> and <i>Cmah-/-mdx</i> controls. The mice also underwent MEMRI and conductance catheter at 28 weeks. This allowed us to characterise the cardiac phenotype of <i>Cmah-/-mdx</i> mice as well as assess the effects of P-PMO on cardiac function. Pip6a-PMO treatment resulted in significant restoration of dystrophin in mdx and <i>Cmah-/-mdx</i> mice (37.5% and 51.6%, respectively), which was sufficient to significantly improve cardiac function, ameliorating both right and left ventricular dysfunction. <i>Cmah-/-mdx</i> mice showed an abnormal response to dobutamine stress test and this was completely ameliorated by PIP6a-PMO treatment. These encouraging data suggest that total restoration of dystrophin may not be required to significantly improve cardiac outcome in DMD patients and that it may be realistic to expect functional improvements with modest levels of dystrophin restoration which may be very achievable in future clinical trials.</p></div

Peptide-conjugated phosphodiamidate oligomer-mediated exon skipping has benefits for cardiac function in <i>mdx</i> and <i>Cmah-/-mdx</i> mouse models of Duchenne muscular dystrophy - Fig 4

<p><b>A-F: P-PMO significantly ameliorates left and right ventricular dysfunction in <i>Cmah-/-mdx</i> mice.</b> Longitudinal MRI data showing A) cardiac index, B) LV ejection fraction and C) LV ESV index. D) RV stroke volume index, E) RV end diastolic volume index and F) RV ejection fraction index (n = 8-13/group) (*p<0.05, **p<0.01 different from <i>C57BL10</i>, #p<0.05, ##p<0.01, ###p<0.001 different from <i>Cmah-/-mdx</i>, ^p<0.05 different from <i>mdx</i>,1-way ANOVA, post-hoc Bonferroni). For clarity of presentation, significant differences between treated <i>Cmah-/-mdx</i> and <i>mdx</i> controls are not annotated. Error bars represent SEM.</p

Peptide-conjugated phosphodiamidate oligomer-mediated exon skipping has benefits for cardiac function in <i>mdx</i> and <i>Cmah-/-mdx</i> mouse models of Duchenne muscular dystrophy - Fig 6

<p><b>A-D: P-PMO corrects abnormal dobutamine stress response of <i>Cmah-/-mdx</i> mice.</b> C57BL10 mice demonstrate a normal response to dobutamine stress with elevation of A) Heart rate, B) dPdt max, C) LV EF and D) LV SV. In Cmah-/-mdx these parameters show a blunted response to dobutamine which is corrected by P-PMO treatment. (*p<0.05, significantly different compared to baseline, Paired Student’s t-test) (n = 7-8/group). Error bars represent SEM.</p

Peptide-conjugated phosphodiamidate oligomer-mediated exon skipping has benefits for cardiac function in <i>mdx</i> and <i>Cmah-/-mdx</i> mouse models of Duchenne muscular dystrophy - Fig 2

<p><b>A-D: P-PMO reduces fibrosis in early treated <i>Cmah-/-mdx</i> mice.</b> A) Treated and untreated <i>mdx</i> mice show a similar range of cardiac pathology but treated animals showed a distinct aspect of pathology- brown staining cells (yellow arrow) which are assumed to be cells rich in intrinsic pigment (such as melanin). H&E staining of heart demonstrating presence of fibrosis, necrotic fibres (green arrows) and (x10) Scale bar = 50 μm. B) Quantification of fibrosis on masson’s trichrome stained <i>Cmah-/-mdx</i> heart sections (*p<0.05, **p<0.01 different from <i>C57BL10</i>, ^P<0.05 different from <i>Cmah-/-mdx</i>, Unpaired Student’s t-tests) (n = 6-9/group) C) Masson’s trichrome stained sections of the most fibrotic animals in each group (Scale bar = 500 μm). D) P-PMO treatment does not significantly affect fibre size distribution (n = 6-9/group, 2-way ANOVA. Error bars represent SEM).</p