Muscle Biopsy Sections Research Articles

Isolation of Live Leukocytes from Human Inflammatory Muscles.

In inflammatory myopathies, the self-reactive immune cells involved in muscle aggression have been studied mostly using histological assessment of muscle biopsy sections; this methodology provides the advantage of visualizing and identifying cells within the tissue, but it does not allow further investigation. To gain access to live and isolated cells, many studies utilized blood samples; however, in the absence of biological tools to discriminate the leukocytes associated with the autoimmune process from those that emerged from responses against pathogens, the information observed on circulating immune cells often lacks in specificity, and thus result interpretation may prove difficult. In order to selectively retrieve self-reactive immune cells, we developed a protocol to isolate live leukocytes from human muscle biopsies, which allows for further analysis using a large range of methodologies. The protocol uses enzymatic digestion to release live leukocytes from freshly collected skeletal muscle samples, followed by filtration and separation of the leukocytes from the myocytes by density gradient centrifugation. The isolated cells can be submitted immediately to various analysis strategies to characterize ex vivo the specific cellular and molecular mechanisms responsible for self-directed immune muscle aggression or may be placed in culture for expansion.

What Every Neuropathologist Needs to Know: The Muscle Biopsy.

Competence in muscle biopsy evaluation is a core component of neuropathology practice. The practicing neuropathologist should be able to prepare frozen sections of muscle biopsies with minimal artifacts and identify key histopathologic features of neuromuscular disease in hematoxylin and eosin-stained sections as well as implement and interpret a basic panel of additional histochemical, enzyme histochemical, and immunohistochemical stains. Important to everyday practice is a working knowledge of normal muscle histology at different ages, muscle motor units, pitfalls of myotendinous junctions, nonpathologic variations encountered at traditional and nontraditional muscle sites, the pathophysiology of myonecrosis and regeneration, and approaches to distinguish muscular dystrophies from inflammatory myopathies and other necrotizing myopathies. Here, we provide a brief overview of what every neuropathologist needs to know concerning the muscle biopsy.

P.145Optimisation of a high–throughput digital script for multiplexed immunofluorescent analysis of sarcolemmal dystrophin - associated protein complex (DPC) and myofibre regeneration in entire transverse sections of muscle biopsies in Duchenne muscular dystrophy

P.145Optimisation of a high–throughput digital script for multiplexed immunofluorescent analysis of sarcolemmal dystrophin - associated protein complex (DPC) and myofibre regeneration in entire transverse sections of muscle biopsies in Duchenne muscular dystrophy

Muscle Expression of Type I and Type II Interferons Is Increased in Juvenile Dermatomyositis and Related to Clinical and Histologic Features.

To evaluate the expression of type I interferon (IFNα/β)- and type II IFN (IFNγ)-inducible genes in muscle biopsy specimens from patients with juvenile dermatomyositis (DM) and to correlate their expression levels with histologic and clinical features. Expression levels of IFN-inducible genes and proinflammatory cytokines were assessed by quantitative polymerase chain reaction in muscle biopsy specimens from patients with juvenile DM (n = 39), patients with Duchenne's muscular dystrophy (DMD), and healthy controls. Muscle biopsy sections were stained and scored for severity of histopathologic features. The charts of patients with juvenile DM were reviewed for clinical features at the time of sampling and long-term outcomes. Muscle expression levels of IFNα/β-inducible genes (type I IFN score), IFNγ, IFNγ-inducible genes (type II IFN score), and tumor necrosis factor (TNF) were significantly higher in juvenile DM patients not receiving glucocorticoid therapy before muscle biopsy (n = 27) compared to DMD patients (n = 24) (type I IFN score, P < 0.0001; type II IFN score, P < 0.001; TNF, P < 0.05) and healthy controls (n = 4) (type I IFN score, P < 0.01; type II IFN score, P<0.01; TNF, P < 0.05). Immunofluorescence staining of muscle biopsy sections from untreated juvenile DM patients showed increased immunoreactivity for IFNγ and HLA class II molecules compared to controls. Type I and type II IFN scores were correlated with typical histopathologic features of juvenile DM muscle biopsy samples, such as infiltration of endomysial CD3+ cells (type I IFN score, r = 0.68; type II IFN score, r = 0.63), perimysial CD3+ cells (type I IFN score, r = 0.59; type II IFN score, r = 0.66), CD68+ cells (type II IFN score, r = 0.46), and perifascicular atrophy (type I IFN score, r = 0.61; type II IFN score, r = 0.77). Juvenile DM patients with a high type I IFN score, a high type II IFN score, and high TNF expression levels showed more severe disease activity at biopsy (P < 0.05). In addition, juvenile DM patients with a high type II IFN score at biopsy reached clinically inactive disease significantly later than patients with low type II IFN score (log rank chi-square value 13.53, P < 0.001). The increased expression of IFN-inducible genes in the muscle in juvenile DM patients and their association with histologic and clinical features further support a pathogenic role for both type I and type II IFNs in juvenile DM.

Comparison between treatment naive juvenile and adult dermatomyositis muscle biopsies: difference of inflammatory cells phenotyping

BackgroundDifferent inflammatory cells (i.e., CD4, CD8, CD20 and CD68) are involved in pathogenesis of DM muscle. In this context, the aim of this study was to assess and compare these inflammatory cell phenotyping in muscle samples of treatment naive juvenile and adult patients with dermatomyositis.MethodsThis is a cross-sectional study, in which 28 untreated juvenile and 28 adult untreated dermatomyositis patients were included. Immunohistochemical analysis was performed on serial frozen muscle sections. Inflammatory cell phenotyping was analyzed quantitatively in endomysium, perimysium, and perivascular (endomysium and perimysium) area.ResultsMean age at disease onset was 7.3 and 42.0 years in juvenile and adult dermatomyositis, respectively. Both groups had comparable time duration from symptom’s onset to biopsy performance. CD4 and CD8 positive cells distributions were similar in both groups in all analyzed area, except for more predominance of CD4 in perimysium at juvenile muscle biopsies. The CD20 and CD68 positive cells were predominantly observed in adult muscle biopsy sections, when compared to juvenile samples, except for similar distribution of CD20 in perivascular endomysium, and CD68 in perimysium.ConclusionsThese data show that the differences between juvenile and adult dermatomyositis may be restricted not only to patients’ age, but also to different inflammatory cell distribution, particularly, in new-onset disease. Further studies are necessary to confirm the present study data and to analyze meaning of the different inflammatory cell phenotyping distribution finding in these both diseases.

Distinct lipid droplet characteristics and distribution unmask the apparent contradiction of the athlete's paradox

ObjectiveIntramyocellular lipid (IMCL) storage negatively associates with insulin resistance, albeit not in endurance-trained athletes. We investigated the putative contribution of lipid droplet (LD) morphology and subcellular localization to the so-called athlete's paradox. MethodsWe performed quantitative immunofluorescent confocal imaging of muscle biopsy sections from endurance Trained, Lean sedentary, Obese, and Type 2 diabetes (T2DM) participants (n = 8/group). T2DM patients and Trained individuals were matched for IMCL content. Furthermore we performed this analysis in biopsies of T2DM patients before and after a 12-week exercise program (n = 8). ResultsWe found marked differences in lipid storage morphology between trained subjects and T2DM: the latter group mainly store lipid in larger LDs in the subsarcolemmal (SS) region of type II fibers, whereas Trained store lipid in a higher number of LDs in the intramyofibrillar (IMF) region of type I fibers. In addition, a twelve-week combined endurance and strength exercise program resulted in a LD phenotype shift in T2DM patients partly towards an ‘athlete-like’ phenotype, accompanied by improved insulin sensitivity. Proteins involved in LD turnover were also more abundant in Trained than in T2DM and partly changed in an ‘athlete-like’ fashion in T2DM patients upon exercise training. ConclusionsOur findings provide a physiological explanation for the athlete's paradox and reveal LD morphology and distribution as a major determinant of skeletal muscle insulin sensitivity.

P.393 - Computational alignment of duplex immunohistochemically-stained muscle sections in support of therapies for Duchenne muscular dystrophy

Continuous expression of utrophin protein by a utrophin modulator could be a disease modifying treatment for Duchenne muscular dystrophy (DMD) patients regardless of their dystrophin mutation. At least 3 biomarkers (a fibre identification biomarker, a regeneration biomarker, and utrophin biomarker) are needed to separate utrophin expression resulting from therapeutic intervention with a utrophin modulator from the pathophysiologic utrophin expression associated with muscle fibre regeneration. Technical challenges of multiplex assay development and analytical validation for 3 or more biomarkers limit the utility of such assays in clinical trials. Having successfully completed the analytical validation of utrophin-laminin α2 (merosin) and developmental myosin heavy chain (MHCd)-laminin α2 duplex immunohistochemical-Computational Tissue Analysis (IHC-cTA™) based assays, we have developed a fibre-based image analysis software to co-register consecutive and non-consecutive serial biopsy sections. The co-registration assay was developed utilising DMD, Becker muscular dystrophy (BMD), and control muscle biopsy sections obtained from the Wellstone Muscular Dystrophy Cooperative Research Center stained with each duplex assay highlighted above. Co-registration quality was numerically evaluated, and visually assessed by a veterinary pathologist. We demonstrate that the cTA™ approach reproducibly detects biomarker signal features (e.g., mean signal intensities), tissue morphometrics (e.g., fibre minimum diameter), and fibre classification (e.g., utrophin+/MHCd-) in whole-slide images of muscle cryosections at an individual muscle fibre resolution. This facilitates understanding of architectural and functional relationships between multiple biomarkers throughout biopsy specimens, and may provide valuable assessment of therapeutic efficacy in on-going and future clinical trials.

Immunohistochemical localization of histidine-rich glycoprotein in human skeletal muscle: preferential distribution of the protein at the sarcomeric I-band.

Histidine-rich glycoprotein (HRG) is a relatively abundant plasma protein that is synthesized by parenchymal liver cells. Using Western blot analysis and immunoperoxidase techniques, we have previously shown the presence of HRG in human skeletal muscle. This paper reports the results of immunofluorescence experiments carried out on sections of human normal skeletal muscle biopsies to investigate the subcellular localization of HRG. The HRG localization was also compared with that of skeletal muscle AMP deaminase (AMPD1), since we have previously described an association of the enzyme with the protein. The obtained results give evidence for a preferential localization of HRG at the I-band level, where it shows the same distribution of actin and where AMPD1 is present in major concentration.

Effects on muscle tissue remodeling and lipid metabolism in muscle tissue from adult patients with polymyositis or dermatomyositis treated with immunosuppressive agents

BackgroundPolymyositis (PM) and dermatomyositis (DM) are autoimmune muscle diseases, conventionally treated with high doses of glucocorticoids in combination with immunosuppressive drugs. Treatment is often dissatisfying, with persisting muscle impairment. We aimed to investigate molecular mechanisms that might contribute to the persisting muscle impairment despite immunosuppressive treatment in adult patients with PM or DM using gene expression profiling of repeated muscle biopsies.MethodsPaired skeletal muscle biopsies from six newly diagnosed adult patients with DM or PM taken before and after conventional immunosuppressive treatment were examined by gene expression microarray analysis. Selected genes that displayed changes in expression were analyzed by Western blot. Muscle biopsy sections were evaluated for inflammation, T lymphocytes (CD3), macrophages (CD68), major histocompatibility complex (MHC) class I expression and fiber type composition.ResultsAfter treatment, genes related to immune response and inflammation, including inflammasome pathways and interferon, were downregulated. This was confirmed at the protein level for AIM-2 and caspase-1 in the inflammasome pathway. Changes in genes involved in muscle tissue remodeling suggested a negative effect on muscle regeneration and growth. Gene markers for fast type II fibers were upregulated and fiber composition was switched towards type II fibers in response to treatment. The expression of genes involved in lipid metabolism was altered, suggesting a potential lipotoxic effect on muscles of the immunosuppressive treatment.ConclusionThe anti-inflammatory effect of immunosuppressive treatment was combined with negative effects on genes involved in muscle tissue remodeling and lipid metabolism, suggesting a negative effect on recovery of muscle performance which may contribute to persisting muscle impairment in adult patients with DM and PM.

A Curious Case of Proximal Muscle Weakness with Eosinophilic Polymyositis.

Eosinophilic polymyositis (EPM) is part of a rare disorder, eosinophilic myopathies (EM), which is a form of polymyositis characterized by the presence of eosinophils in muscle biopsy sections and occasionally blood eosinophilia. Herein, we are presenting an interesting case of eosinophilic polymyositis presenting with muscle pain with no other organ systems involved.

Congenital muscular dystrophy with inflammation: Diagnostic considerations.

Background and Purpose:Muscle biopsy features of congenital muscular dystrophies (CMD) vary from usual dystrophic picture to normal or nonspecific myopathic picture or prominent fibrosis or striking inflammatory infiltrate, which may lead to diagnostic errors. A series of patients of CMD with significant inflammatory infiltrates on muscle biopsy were correlated with laminin α2 deficiency on immunohistochemistry (IHC).Material and Methods:Cryostat sections of muscle biopsies from the patients diagnosed as CMD on clinical and muscle biopsy features from 1996 to 2014 were reviewed with hematoxylin and eosin(H&E), enzyme and immunohistochemistry (IHC) with laminin α2. Muscle biopsies with inflammatory infiltrate were correlated with laminin α2 deficiency.Results:There were 65 patients of CMD, with inflammation on muscle biopsy in 16. IHC with laminin α2 was available in nine patients, of which six showed complete absence along sarcolemma (five presented with floppy infant syndrome and one with delayed motor milestones) and three showed discontinuous, and less intense staining.Conclusions:CMD show variable degrees of inflammation on muscle biopsy. A diagnosis of laminin α2 deficient CMD should be considered in patients of muscular dystrophy with inflammation, in children with hypotonia/delayed motor milestones.

Inhibition of muscle fibrosis results in increases in both utrophin levels and the number of revertant myofibers in Duchenne muscular dystrophy.

Duchenne Muscular Dystrophy is characterized by: near absence of dystrophin in skeletal muscles; low percentage of revertant myofibers; up-regulation of utrophin synthesis; and a high degree of muscle fibrosis. In patient quadriceps femoris biopsies (n = 6, ages between 3-9 years) an inverse correlation was observed between the levels of collagen type I - representing fibrosis - and the levels of utrophin. This correlation was independent of the patient's age and was observed in the entire muscle biopsy sections. In the mdx mice diaphragm (n = 6/group), inhibition of fibrosis by halofuginone resulted in increases in the levels of utrophin. The utrophin/fibrosis relationships were not limited to collagen type I, but also applied to other constituents of the fibrosis machinery. The inverse correlation was found also in old mdx mice with established fibrosis. In addition, inhibition of collagen type I levels was associated with increases in the numbers of revertant myofibers, both as single myofibers and in clusters in the diaphragm and the gastrocnemius. In summary, our results demonstrate an inverse correlation between the level of muscle fibrosis and the level of utrophin and that of the number of revertant myofibers. These findings may reveal common links between the fibrotic and utrophin-synthesis pathways and offer new insights into the regulation of utrophin synthesis.

Clinico pathological study of adult dermatomyositis: Importance of muscle histology in the diagnosis.

Aims:To study the histological features on muscle biopsy and correlate them with clinical features, other laboratory data in adult patients to make a diagnosis of dermatomyositis (DM), applying the European Neuromuscular center (ENMC) criteria.Materials and Methods:Adult patients who fulfilled clinical, laboratory, and muscle biopsy findings according to ENMC criteria for DM during the period 2010–2013 were included in the study. Cryostat sections of muscle biopsy were reviewed with emphasis on Perifascicular atrophy (PFA), perivascular/endomysial inflammation. Muscular dystrophies and metabolic myopathies were excluded by appropriate immunohistochemistry and special stains.Results:The diagnosis of adult DM was made in 45 patients out of 170 clinically suspected idiopathic inflammatory myopathies. These included 33 definite, 4 probable, 7 possible sine dermatitis, and 1 amyopathic DM. All patients with definite DM had typical rash and proximal muscle weakness and muscle biopsy showed PFA with or without inflammation. Thirteen patients had quadriparesis, neck muscle weakness, dysphagia/dysphonia at presentation. Patients with probable DM had rash and showed perivascular/endomysial inflammation with no PFA. Possible DM sine dermatitis showed PFA with perivascular/endomysial infiltrates. One patient of amyopathic DM had typical heliotrope rash and characteristic skin biopsy.Conclusions:Histological features are important for the diagnosis of DM. Relying on PFA for diagnosis of definite DM underestimates the true frequency of DM.

Frequencies of myohistological mitochondrial changes in patients with mitochondrial DNA deletions and the common m.3243A>G point mutation.

Frequencies of typical myohistological changes such as ragged red fibers (RRF) and cytochrome c oxidase (COX)-deficient fibers have been suggested to be dependent on underlying mitochondrial DNA (mtDNA) defect. However, there are no systematic studies comparing frequencies of myohistological changes and underlying genotypes. The histopathological changes were analysed in 29 patients with genetically confirmed mitochondrial myopathies. Genotypes included multiple mtDNA deletions due to POLG1 mutations (n = 11), single mtDNA deletion (n = 10) and mtDNA point mutation m.3243A>G (n = 8). Histochemical reactions, including Gomori-trichome, COX/SDH (succinate dehydrogenase) and SDH as well as immunohistological reaction with COX-antibody against subunit I (COI) were carried out in muscle biopsy sections of all patients. The COX-deficient fibers were observed most frequently in all three patient groups. The frequencies of myopathological changes were not significantly different in the different genotypes in all three histochemical stains. However, there was a tendency to lower means and variations in patients with point mutation. Only COI-negative fibers were histochemically negative for COX activity in all patient groups. Frequency of COI-negative fibers was significantly lower in patients with mtDNA point mutation than in patients with deletions. This suggests that impact of point mutation on protein synthesis is less than that of deletions.

FRI0500 Evaluation of the Role of Fractalkine Chemokine CX3CL1 and Its Receptor CX3CR1 in Inflammatory Myopathies

BackgroundIn inflammatory myopathies (IM), including polymyositis (PM), dermatomyositis (DM) and inclusion body myositis (IBM), serum creatinine kinase (CKs) can be not always reliable to evaluate disease activity. Thus, new biomarkers...

P.1.17 Immunostaining of the sarcolemma with a new monoclonal antibody against alpha-dystroglycan core and its relevance to diagnosis

Alpha-dystroglycan ( α DG) is an extracellular, glycosylated protein attached to the outer plasma membrane by its interaction with the transmembrane protein, beta-dystroglycan. Genetic mutations that alter the glycosylation state of α DG cause a number of inherited disorders, including Fukuyama MD and certain congenital and limb-girdle MDs. Many of the pathogenic mutations are in proteins that carry out glycosylation of α DG and not in the DG gene itself. These enzymes are usually located in the Golgi where proteins are modified before export to the extracellular space. Amino-acid mutations in α DG itself can also cause congenital MD when sugar attachment to the α DG backbone is affected. Antibodies against dystroglycans immunostain the sarcolemma in a similar manner to dystrophin antibodies. It would be useful to the muscle pathologist to have monoclonal antibodies (mAbs) that recognize specific glycosylated forms of α DG associated with different mutations or disease states, since such mAbs would be useful for diagnosis using muscle biopsy sections. There are problems of reproducibility with existing mAbs against α DG, but it is still unclear whether those problems are attributable to the antibodies themselves or to the nature of the glycosylated epitopes on α DG. To determine whether it is possible to obtain improved mAbs for diagnostic use, we have begun a collaborative programme, supported by LGMD2I and CureCMD, to produce new mAbs against glycosylated and non-glycosylated forms of α DG. As a first step, we now describe a new mAb raised against bacterial recombinant α DG core sequence, which gives good staining of the sarcolemma in human muscle biopsy sections. We have mapped the epitope recognized by this mAb to short sequence that appears to be accessible to antibody in BOTH glycosylated and non-glycosylated forms of α DG.

P.17.14 Myohistological mitochondrial changes in patients with mtDNA singular deletions, multiple deletions and A3243G point mutation

Chronic progredient external opthalmoplegia (CPEO) and the MELAS syndrome are the most common disorders that are associated with mitochondrial changes. CPEO is either associated with singular or multiple mtDNA deletions, whereas, MELAS is usually caused by the A3243G point mutation on mtDNA. The basic diagnostic criteria for these diseases are histopathological changes in muscle biopsy. So far, a systematic study comparing myopathological changes in these three groups has not yet been reported. We analysed muscle biopsies from 29 patients (16 males, 13 females) with mitochondrial diseases to investigate whether the genetic background influences the incidence of histopathological changes. 10 patients had singular mtDNA deletions and 11 patients had multiple deletions due to POLG1 nuclear mutations. Additionally, 8 patients harboured the MELAS A3243G point mutation. Freeze-dried sections of muscle biopsies were stained for histochemical reactions with Gomori trichrome, COX/SDH and SDH stainings. Furthermore, immunohistological reaction with COX antibody was also carried out. In all three groups, the COX-negative fibers were observed most frequently. The frequency of RRF was about a third of the COX-negative fibers. Dark blue COX-negative fibers were significantly higher than the hyperreactive fibers in SDH staining. The parallel analysis of individual pathological fibres showed that, in all three groups, all COX negative fibers had pathological changes also in other stainings and immunohistology. The results confirm that the COX/SDH double staining is the most sensitive method in the diagnosis compared to the other two stainings. Nevertheless, these changes could have been occurred due to the high overlap between the three groups in each individual cases.

Cell stress molecules in the skeletal muscle of GNE myopathy

BackgroundMutations of the UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine-kinase (GNE)-gene are causally related to GNE myopathy. Yet, underlying pathomechanisms of muscle fibre damage have remained elusive. In sporadic inclusion body myositis (sIBM), the pro-inflammatory cell-stress mediators αB-crystallin and inducible nitric oxide synthase (iNOS) are crucial markers of the disease pathology.Methods10 muscle biopsies from GNE myopathy patients were analyzed for mRNA-expression of markers of cell-stress, inflammation and β-amyloid and compared to non-myopathic controls. Using double-labeling immunohistochemistry, serial sections of skeletal muscle biopsies were stained for amyloid precursor protein (APP), major histocompatibility complex (MHC)-I, αB-crystallin, neural cell adhesion molecule (NCAM), interleukin (IL)-1β, β-amyloid, iNOS, and phosphorylated neurofilament (P-neurofilament) as well as hematoxylin/eosin histochemistry. Corresponding areas of all biopsies with a total of 2,817 muscle fibres were quantitatively assessed for all markers.ResultsmRNA-expression of APP, NCAM, iNOS, TNF-α and TGF-β was higher in GNE myopathy compared to controls, yet this was not statistically significant. The mRNA-expression of APP and αB-crystallin significantly correlated with the expression of several pro-inflammatory and cell-stress-associated markers as NCAM, IL-1β, TGF-β, CCL-3, and CCL4. By immunohistochemistry, αB-crystallin and iNOS were co-upregulated and the number of fibres positive for αB-crystallin, NCAM, MHC-I and iNOS significantly correlated with each other. A large fraction of fibres positive for αB-crystallin were double positive for iNOS and vice-versa. Moreover, several fibres with structural abnormalities were positive for αB-crystallin and iNOS. Notably, particularly normal appearing fibres displayed an overexpression of these molecules.ConclusionsThe cell-stress molecules αB-crystallin and iNOS are overexpressed in GNE myopathy muscle and may identify early disease mechanisms. The data help to better understand the pathology of GNE myopathy.

Influence of Pre-analytical Variables on VEGF Gene Expression and Circulating Protein Concentrations

The extended role of vascular endothelial growth factor (VEGF) in human pathophysiology led us to evaluate pre-analytical parameters possibly influencing its levels in peripheral blood and tissues. The effects on VEGF protein levels and mRNA expression were measured after storage delay (blood and tissue), use of different types of anticoagulants (blood), and after different numbers of freeze-thaw cycles (blood). Blood from healthy donors was sampled simultaneously in ethylene diamine tetraacetic acid (EDTA), acid citrate dextrose (ACD-A), hirudin, and serum separation tubes. For each anticoagulant, VEGF was measured by enzyme-linked immunosorbent assay (ELISA) with different conditions of delay at 4°C before centrifugation (2 h, 4 h, or 48 h) and of different numbers of freeze-thaw cycles (1, 2, and 10). The transcripts coding for the VEGF165 isoform were quantified in peripheral blood mononuclear cells by RT-PCR. Muscle biopsy samples were frozen with delays of 15, 30, or 60 min after surgery. VEGF expression was quantified on immunofluorescence stained slides. The period of storage and the number of freeze-thaw cycles correlated with an increase in the levels of circulating VEGF (for each anticoagulant but not for serum) and its expression in PBMCs. VEGF expression measured from muscle biopsy sections was higher with freezing delays, with a peak at 30 and 60 min as compared to 15 min. The most reliable conditions for measuring both circulating VEGF and its gene expression are to reduce time between blood collection and centrifugation, and to avoid multiple freeze-thaw cycles. Serum collection tubes with no additive and no separator were less sensitive to the pre-analytical variations analyzed in this study. Freezing delay had a significant influence on VEGF protein expression in tissue samples.

Quantification of dystrophin immunofluorescence in dystrophinopathy muscle specimens

Duchenne muscular dystrophy (DMD) is usually associated with absent or nearly absent dystrophin expression at the sarcolemmal membrane. Quantification of very low levels of dystrophin signal in immunofluorescent studies of muscle biopsy sections presents a technical challenge. This is particularly true in the setting of proof-of-principle drug trials, in which the detection and quantification of what may be significant changes in levels of expression is important, even if absolute dystrophin levels remain low. We have developed a method of image analysis that allows reliable and semi-automated immunofluorescent quantification of low-level dystrophin expression in sections co-stained for spectrin. Using a custom Metamorph script to create a contiguous region spectrin mask, we quantify dystrophin signal intensity only at pixels within the spectrin mask that presumably represent the sarcolemmal membrane. Using this method, we analysed muscle biopsy tissue from a series of patients with DMD, Becker muscular dystrophy, intermediate muscular dystrophy and normal control tissue. Analysis of serial sections on multiple days confirms reproducibility, and normalized dystrophin:spectrin intensity ratios (expressed as a percentage of normal control tissue) correlate well with the dystrophin expression levels as determined by Western blot analysis. This method offers a robust and reliable method of biomarker detection for trials of DMD therapies.