Fiber Atrophy Research Articles

Fatty infiltration of the shoulder: diagnosis and reversibility

Fatty degeneration is a degenerative condition of the tendon-muscle unit of rotator cuff muscles, characterized by atrophy of muscle fibers, fibrosis, and fatty accumulation within and around the muscles. Many classification may be useful to stage this pathology, especially on Computed Tomography (CT) and magnetic resonance imaging (Mari) findings. Stem cell-based therapies for repair and regeneration of tendons and muscles may be used to promote healing and to make this condition reversible. Diagnosis and management of this condition is mandatory as in patients undergoing rotator cuff repair, it may influence outcomes, increase the likelihood of re-tearing, and evolve negatively.

Maslinic acid derived from olive fruit in combination with resistance training improves muscle mass and mobility functions in the elderly.

Maslinic acid, derived from olive fruit, reduces pro-inflammation cytokines, which are involved in muscle fiber atrophy. Therefore, the maslinic acid ingestion may enhance the muscular response to resistance training through anti-inflammatory action. We therefore conducted a parallel, double-blind, randomized, placebo-controlled trial that examined whether a combination of maslinic acid supplementation and resistance training improve mobility functions in community-dwelling elderly persons. Over a 12-week period, 36 participants underwent moderate resistance training and are assigned to the maslinic acid supplementation (n = 17, 60 mg/day) or the placebo (n = 19) group. At baseline and at 12-weeks, we assessed body composition, grip strength, walking speed, leg strength, mobility functions, and knee pain scores. Following the 12-weeks, skeletal muscle mass, segmental muscle mass (right arm, left arm, and trunk) and knee pain score of the right leg were significantly improved in the maslinic acid group, while there was no change or parameters had worsened in the placebo group. Grip strength of the better side significantly increased only in the maslinic acid group. These results suggest that maslinic acid supplementation combined with moderate resistance training may increase upper muscle mass and grip strength, and reduce knee pain, could be effective for preventing mobility-related disability in elderly persons. Clinical trial registration number: UMIN000017207.

Sex differences in COPD-related quadriceps muscle dysfunction and fibre abnormalities.

In chronic obstructive pulmonary disease (COPD), lower limb dysfunction is associated with reduced exercise capacity, increased hospitalizations and mortality. We investigated sex differences in the prevalence of quadriceps dysfunction and fibre abnormalities in a large COPD cohort, controlling for the normal sex differences in health. We compared existing data from 76 male and 38 female COPD patients where each variable was expressed as a function of gender-specific normal values (obtained from 16 male and 14 female controls). Female COPD patients had lower quadriceps muscle strength and peak workload on a maximal incremental cycle ergometry protocol compared to male patients. Female patients had a smaller type II fibre cross-sectional area (CSA) compared to male patients, suggesting a greater female preponderance to fibre atrophy, although this result was largely driven by a few male patients with a large type II fibre CSA. Female patients had significantly higher concentrations of a number of plasma pro-inflammatory cytokines including tumour necrosis factor alpha and interleukin 8 (IL8), but not lower levels of physical activity or arterial oxygenation, compared to males. Our data confirm results from a previous small study and suggest that female COPD patients have a greater prevalence of muscle wasting and weakness. Larger studies investigating sex differences in COPD-related muscle atrophy and weakness are needed, as the results will have implications for monitoring in clinical practice and for design of clinical trials evaluating novel muscle anabolic agents.

Inspiratory Muscle Training in Patients with Prolonged Mechanical Ventilation: Narrative Review.

Patients with impending respiratory failure often require mechanical ventilation to optimize gas exchange. Although this form of assisted ventilation is required for survival, its persistent use results in diaphragm weakness and muscle fiber atrophy. There is strong evidence that mechanical ventilation alters the structure and function of the diaphragm, resulting in prolonged dependence on assisted ventilation and long-term consequences such as a delayed functional recovery, reduced quality of life and increased risk of mortality. This review summarizes the mechanisms underlying diaphragm dysfunction due to prolonged mechanical ventilation, highlights the role of inspiratory muscle exercise as a strategy to counter diaphragm weakness, and identifies the parameters of an evidence-supported exercise prescription for difficult to wean patients.

THE ULTRASTRUCTURAL STUDY OF THE SPINAL CORD AND THE DELTOID MUSCLE OF THE CLINICAL CASE OF THE VERDNIG-HOFFMANN SYNDROME

The Werdnig-Hoffmann syndrome is an infantile form of hereditary spinal progressive muscle atrophy with an autosomal recessive mode of inheritance with a frequency of 1 per 10,000 population. The data on the complex ultramicroscopic study of the spinal cord and deltoid muscle of a clinical case of Verdnig-Hoffmann syndrome in a newborn male child who died at the age of 1 month are given. Rubella virus patterns of the RNA were isolated in serum and spinal cord tissue samples. Changes in the structure of the spinal cord and deltoid muscle are described. An ultrastructural study showed the presence of a virus in the tissue of the spinal cord and vascular endothelial cells of the muscle. In the tissue of the spinal cord against the destruction of neurons was detected rubella virus. Viral particles were localized both in the cytoplasm of preserved oligodendrocytes and diffusely in destructively altered tissue of the spinal cord. The number of cells in the spinal cord tissue was reduced, the structure of their mitochondria was disturbed, and vacuolization of the cytoplasm was detected. For myelin fibers there is inherent heterogeneity of the thickness of the membranes, uneven distribution, deformation of the contours, and variability of diameters. Myelin fibers stratified, fragmented, osmiophilia lost. In the study of muscle samples prevailed destructively modified muscle fibers. At the same time, against the background of an unevenly pronounced atrophy of muscle fibers, the reproduction of the rubella virus in the cytoplasm of capillary endotheliocytes and pericytes of muscle vessels was detected. The etiological role of the rubella virus in the onset of the clinical symptoms constituting spinal muscular atrophy syndrome as a variant of congenital rubella has been suggested. .

Delayed myonuclear addition, myofiber hypertrophy, and increases in strength with high-frequency low-load blood flow restricted training to volitional failure.

The purpose of the present study was to investigate muscle hypertrophy, strength, and myonuclear and satellite cell (SC) responses to high-frequency blood flow-restricted resistance exercise (BFRRE). Thirteen individuals [24 ± 2 yr (mean ± SD), 9 men] completed two 5-day blocks of 7 BFRRE sessions, separated by a 10-day rest period. Four sets of unilateral knee extensions to voluntary failure at 20% of one repetition maximum (1RM) were conducted with partial blood flow restriction (90-100 mmHg). Muscle samples obtained before, during, 3 days, and 10 days after training were analyzed for muscle fiber area (MFA), myonuclei, SC, and mRNA and miRNA expression. Muscle size was measured by ultrasonography and magnetic resonance imaging and strength with 1RM knee extension. With the first block of BFRRE, SC number increased in both fiber types (70%-80%, P < 0.05), whereas type I and II MFA decreased by 6 ± 7% and 15 ± 11% ( P < 0.05), respectively. With the second block of training, muscle size increased by 6%-8%, whereas the number of SCs (type I: 80 ± 63%, type II: 147 ± 95%), myonuclei (type I: 30 ± 24%, type II: 31 ± 28%), and MFA (type I: 19 ± 19%, type II: 11 ± 19%) peaked 10 days after the second block of BFRRE, whereas strength peaked after 20 days of detraining (6 ± 6%, P < 0.05). Pax7- and p21 mRNA expression were elevated during the intervention, whereas myostatin, IGF1R, MyoD, myogenin, cyclinD1 and -D2 mRNA did not change until 3-10 days postintervention. High-frequency low-load BFRRE induced robust increases in SC, myonuclei, and muscle size but modest strength gains. Intriguingly, the responses were delayed and peaked 10-20 days after the training intervention, indicating overreaching. NEW & NOTEWORTHY In line with previous studies, we demonstrate that high-frequency low-load blood flow-restricted resistance exercise (HF-BFRRE) can elicit robust increases in satellite cell and myonuclei numbers, along with gains in muscle size and strength. However, our results also suggest that these processes can be delayed and that with very strenuous HF-BFRRE, there may even be transient muscle fiber atrophy, presumably because of accumulated stress responses. Our findings have implications for the prescription of BFR exercise.

Hispaglabridin B, a constituent of liquorice identified by a bioinformatics and machine learning approach, relieves protein-energy wasting by inhibiting forkhead box O1.

Liquorice is the root of Glycyrrhiza glabra, which is a popular food in Europe and China that has previously shown benefits for skeletal fatigue and nutrient metabolism. However, the mechanism and active ingredients remain largely unclear. The aim of this study was to investigate the active ingredients of liquorice for muscle wasting and elucidate the underlying mechanisms. RNA-Seq and bioinformatics analysis were applied to predict the main target of liquorice. A machine learning model and a docking tool were used to predict active ingredients. Isotope labelling experiments, immunostaining, Western blots, qRT-PCR, ChIP-PCR and luciferase reporters were utilized to test the pharmacological effects in vitro and in vivo. The reverse effects were verified through recombination-based overexpression. The liposoluble constituents of liquorice improved muscle wasting by inhibiting protein catabolism and fibre atrophy. We further identified FoxO1 as the target of liposoluble constituents of liquorice. In addition, hispaglabridin B (HB) was predicted as an inhibitor of FoxO1. Further studies determined that HB improved muscle wasting by inhibiting catabolism in vivo and in vitro. HB also markedly suppressed the transcriptional activity of FoxO1, with decreased expression of the muscle-specific E3 ubiquitin ligases MuRF1 and Atrogin-1. HB can serve as a novel natural food extract for preventing muscle wasting in chronic kidney disease and possibly other catabolic conditions.

Prolonged exercise training improves the acute type II muscle fibre satellite cell response in healthy older men.

Skeletal muscle stem cells, termed satellite cells, play a crucial role in repair and remodelling of muscle in response to exercise An age-related decline in satellite cell number and/or function has been hypothesized to be a key factor in the development of sarcopenia and/or the blunted muscle fibre adaptive response to prolonged exercise training in older persons We report that performing prolonged exercise training improves the acute type II muscle fibre satellite cell response following a single bout of resistance exercise in older men. The observed improvement in muscle satellite function is associated with an increase in muscle fibre capillarization following exercise training suggesting a possible functional link between capillarization and satellite cell function. Age-related type II muscle fibre atrophy is accompanied by a fibre type-specific decline in satellite cell number and function. Exercise training restores satellite cell quantity in older adults; however, whether it can restore the impaired satellite cell response to exercise in older adults remains unknown. Therefore we assessed the acute satellite cell response to a single exercise session before and after prolonged exercise training in older men. Fourteen older men (74±8years) participated in a 12-week exercise training programme (resistance exercise performed twice per week, high intensity interval training once per week). Before and after training, percutaneous biopsies from the vastus lateralis muscle were taken prior to and following 24 and 48h of post-exercise recovery. Muscle fibre characteristics were evaluated by immunohistochemistry and mRNA expression by RT-PCR. Whereas no changes were observed in type II muscle fibres, type I muscle fibre satellite cell content increased significantly at 24 and 48h after a single bout of resistance exercise before the exercise training programme (P<0.01). Following the exercise training programme, both type I and type II muscle fibre satellite cell content increased significantly at 24 and 48h after a single bout of resistance exercise (P<0.05). The greater acute increase in type II muscle fibre satellite cell content at 24 h post-exercise recovery after training was correlated with an increase in type II muscle fibre capillarization (r=0.671, P=0.012). We show that the acute muscle satellite cell response following exercise can be improved by prolonged exercise training in older men.

Endoplasmic reticulum stress and unfolded protein response profile in quadriceps of sarcopenic patients with respiratory diseases.

Impaired muscle strength and mass (sarcopenia) are common in patients with respiratory cachexia, namely chronic obstructive pulmonary disease (COPD) and in lung cancer (LC)-cachexia. Misfolded/unfolded proteins in endoplasmic reticulum (ER) induce the compensatory unfolded protein response (UPR). Expression of ER stress and UPR markers may be differentially upregulated in vastus lateralis (VL) of patients with respiratory sarcopenia associated with either a chronic condition (COPD) or subacute (LC)-cachexia. In VL specimens from 40 COPD patients (n = 21, sarcopenic, fat-free mass index [FFMI] 16 kg/m2 and n = 19, nonsarcopenic, FFMI 18 kg/m2 ), 13 patients with LC-cachexia (FFMI 17 kg/m2 ), and 19 healthy controls (FFMI 19 kg/m 2 ), expression markers of ER stress, UPR (protein kinase-like ER kinase [PERK], activating transcription factor [ATF] 6, and inositol-requiring enzyme [IRE] 1-α), oxidative stress, autophagy, proteolysis, and apoptosis (reverse transcription polymerase chain reaction and immunoblotting), and fiber atrophy (histology) were assessed. Atrophy and muscle wasting and weakness were seen in both groups of sarcopenic patients. Compared to healthy controls, in muscles of LC-cachexia patients, expression of ER stress markers and UPR (three arms) was significantly upregulated, while in sarcopenic COPD, expression of a few ER stress markers and IRE1-α arm was upregulated. ER stress and an exaggerated UPR were observed in the VL muscle of patients with respiratory sarcopenia. The three branches of UPR were similarly upregulated in muscles of cancer cachectic patients, whereas in sarcopenic COPD patients, only IRE1 was upregulated. The differential profile of muscle UPR in chronic and subacute respiratory conditions offers a niche for the design of specific novel therapeutic approaches.

Ventilator-induced diaphragm dysfunction in critical illness.

Mechanical ventilation (MV) is life-saving for patients with acute respiratory failure but also causes difficult liberation of patients from ventilator due to rapid decrease of diaphragm muscle endurance and strength, which is termed ventilator-induced diaphragmatic damage (VIDD). Numerous studies have revealed that VIDD could increase extubation failure, ICU stay, ICU mortality, and healthcare expenditures. However, the mechanisms of VIDD, potentially involving a multistep process including muscle atrophy, oxidative loads, structural damage, and muscle fiber remodeling, are not fully elucidated. Further research is necessary to unravel mechanistic framework for understanding the molecular mechanisms underlying VIDD, especially mitochondrial dysfunction and increased mitochondrial oxidative stress, and develop better MV strategies, rehabilitative programs, and pharmacologic agents to translate this knowledge into clinical benefits.

Oral Tumors Having the Origins in Multiple Tissues, Non-differentiated or Differentiated

The lesions in the oral cavity must be seen in the light of pathological and correlated system processeswith systemic illnesses because systemic illnesses cause oral manifestations and inversely - oral affections(Alvin Gardner). Many times, when symptoms and signs occur, the disease is in an advanced phase, the interest of the oral cavity being the expression of a generalized illness. Extremely varied tumors in shape and evolution come from multiple tissues undifferentiated or differentiated, often in a complication of different structures, which imparts to them a histological polymorphism. They can be found and traced in their evolution during a dental examination, more easily than those developed at the organs. An early detection of precancerous states and neoplasia can be made, and clinical and paraclinical data are corroborated in the dynamics of the evolutionary process, with the observation that, in the presence of benign histological aspects, evolution may be serious due to functional turbulence lymphangioma of the tongue with muscle fiber atrophy, epithelial ulceration and superadded inflammation with oral phlegmon), haemorrhages (oral mucosal hemangioma). We studied 120 patients with oral tumors originating in multiple non-differentiated tissues or differentiated, over a 5-year period, January 2012-December 2016. Malignant ganglion involvement includes a broad pathology requiring rigorous, clinical, paraclinical, histological and immunohistochemical examination to achieve effective therapeutic management. The degree of malignancy should be specified in all cases where this is possible with the help of available systems as it is of prognostic and predictive importance.

Endurance exercise protects skeletal muscle against both doxorubicin-induced and inactivity-induced muscle wasting.

Repeated bouts of endurance exercise promotes numerous biochemical adaptations in skeletal muscle fibers resulting in a muscle phenotype that is protected against a variety of homeostatic challenges; these exercise-induced changes in muscle phenotype are often referred to as "exercise preconditioning." Importantly, exercise preconditioning provides protection against several threats to skeletal muscle health including cancer chemotherapy (e.g., doxorubicin) and prolonged muscle inactivity. This review summarizes our current understanding of the mechanisms responsible for exercise-induced protection of skeletal muscle fibers against both doxorubicin-induced muscle wasting and a unique form of inactivity-induced muscle atrophy (i.e., ventilator-induced diaphragm atrophy). Specifically, the first section of this article will highlight the potential mechanisms responsible for exercise-induced protection of skeletal muscle fibers against doxorubicin-induced fiber atrophy. The second segment will discuss the biochemical changes that are responsible for endurance exercise-mediated protection of diaphragm muscle against ventilator-induced diaphragm wasting. In each section, we highlight gaps in our knowledge in hopes of stimulating future research in this evolving field of investigation.

Evidence of functional deficits at the single muscle fiber level in experimentally-induced renal insufficiency

Chronic kidney disease patients present with metabolic and functional muscle abnormalities, called uremic myopathy, whose mechanisms have not yet been fully elucidated. We investigated whether chronic renal insufficiency (CRI) affects skeletal muscle contractile properties at the cellular level. CRI was induced surgically in New Zealand rabbits (UREM), with sham-operation for controls (CON), and samples were collected at 3 months post-surgery, following euthanasia. All protocols had University Ethics approval following national and European guidelines. Sample treatments and evaluations were blinded. Maximal isometric force was assessed in 382 permeabilized psoas fibers (CON, n = 142, UREM, n = 240) initially at pH7, 10 °C (‘standard’ conditions), in subsets of fibers in acidic conditions (pH6.2, 10 °C) but also at near physiological temperature (pH7, 30 °C and pH6.2, 30 °C). CRI resulted in significant smaller average cross sectional areas (CSAs) by ∼11% for UREM muscle fibers (vs CON, P < 0.01). At standard conditions, UREM fibers produced lower absolute and specific forces (i.e. normalized force per fiber CSA) (vs CON, P < 0.01); force increased in 30 °C for both groups (P < 0.01), but the disparity between UREM and CON remained significant. Acidosis significantly reduced force (vs pH7, 10 °C P < 0.01), similarly in both groups (in UREM by −48% and in CON by −43%, P > 0.05). For the first time, we give evidence that CRI can induce significant impairments in single psoas muscle fibers force generation, only partly explained by fiber atrophy, thus affecting muscle mechanics at the cellular level.

Intensified mitophagy in skeletal muscle with aging is downregulated by PGC-1alpha overexpression in vivo

Mitochondrial dysfunction plays an important role in the etiology of age-related muscle atrophy known as sarcopenia. PGC-1α is positioned at the center of crosstalk in regulating mitochondrial quality control, but its role in mitophagy in aged skeletal muscle is currently unclear. The present study investigated the effects of aging and PGC-1α overexpression via in vivo DNA transfection on key mitophagy protein markers, as well as mitochondrial dynamics related proteins, metabolic function and antioxidant capacity in mouse muscle. C57BL/6J mice at the age of 2 mo (young, Y; N = 14) and 24 mo (old, O; N = 14) were transfected in vivo with either PGC-1α DNA (OE, N = 7) or GFP (N = 7) into the tibialis anterior (TA) muscle followed by electroporation. PINK1 and Parkin protein contents were 3.6 and 1.4-fold higher (P < 0.01), whereas mitochondrial ubiquitination (Ub) increased 1.5-fold (P < 0.05), in O vs. Y mice. PGC-1 OE suppressed PINK and Parkin protein levels by 50–60% (P < 0.01), and decreased Ub by 20% (P < 0.05) in old mice. Aging significantly increased the protein content of LC3II (30%, P < 0.05), p62 (42%, P < 0.05), RheB (5.5-fold, P < 0.01), Beclin-1 (3-fold, P < 0.01) and Mfn2 (~4-fold, P < 0.01) in the TA muscle. However, these age-related increases in mitophagy markers were attenuated by PGC-1α OE. Furthermore, aging dramatically increased Fis-1 protein content by 14-fold (P < 0.01), along with a severe reduction of citrate synthase activity (64%, P < 0.01) and cytochrome c oxidase subunit IV (COXIV) protein content (85%, P < 0.01). PGC-1α OE mitigated the age effects on Fis-1 and Drp-1 (P < 0.05). Moreover, PGC-1α OE enhanced mitochondrial oxidative function and antioxidant enzyme activities, and decreased lipid peroxidation and inner membrane damage found in old mice (P < 0.01). In summary, our data demonstrate that mitophagy protein expression in skeletal muscle was enhanced at old age driven possibly by increased mitochondrial dysfunction, damage, and fission. PGC-1α OE was effective in ameliorating mitochondrial deficits but did not restore muscle fiber atrophy.

Systemic bone loss, impaired osteogenic activity and type I muscle fiber atrophy in mice with elastase-induced pulmonary emphysema: Establishment of a COPD-related osteoporosis mouse model.

Although it is suggested that chronic obstructive pulmonary disease (COPD) and bone are related, almost all of the pathological mechanisms of COPD-related osteoporosis remain unknown. There is a mouse model showing a deterioration of bone quality after cigarette smoke exposure; however, in smoking exposure models, various factors exist that affect bone metabolism, such as smoking and body weight loss (muscle and fat mass loss). We considered it appropriate to use an elastase-induced emphysema model to exclude factors influencing bone metabolism and to investigate the influence of pulmonary emphysema on bone metabolism. The purpose of this study was to establish a COPD/emphysema-related osteoporosis mouse model by using the elastase-induced emphysema model. The lumbar vertebrae and femurs/tibiae exhibited trabecular bone loss and impaired osteogenic activity in 24-week-old male elastase-induced emphysema model mice. In addition, the model mice showed atrophy of type I muscle fibers without atrophy of type II muscle fibers. We believe that the mice described in this experimental protocol will be accepted as a COPD/emphysema-related osteoporosis mouse model and contribute to further investigations.

Muscle Biopsy and Electromyography Correlation.

Introduction: In myopathies, the correlation of individual electromyographic and histopathologic findings remains poorly explored, as most previous studies have focused on the ability of muscle biopsy and electromyography to distinguish the neuropathic vs. myopathic nature of the underlying neuromuscular disease.Methods: We identified 100 patients who had a muscle biopsy and electromyography performed on identical muscles. We used a detailed grading system ranging from 0- normal to 4- severe; and graded 16 histopathologic findings in each biopsy. Electromyography findings were also graded from 0 to 4 according to the standard protocol in our EMG laboratory. We used Kendall's tau for non-parametric ordinal correlation analysis.Results: Fibrillation potentials correlated with atrophic, necrotic, and regenerating fibers, fibers harboring vacuoles, fiber splitting, fibers reacting for non-specific esterase, fibers with congophilic inclusions, inflammation (endoymysial and perimysial), and increased endomysial connective tissue. Short-duration motor unit potentials correlated with atrophic, necrotic, and regenerating fibers, increased endomysial connective tissue, and perimysial inflammation. Long-duration motor unit potentials correlated with fiber-type grouping. Increased phases of motor unit potentials correlated with atrophic fibers, increased endomysial connective tissue, and fibers reacting for non-specific esterase; while increased turns correlated with atrophic and regenerating fibers, increased endomysial connective tissue and target formations. Rapid recruitment correlated with regenerating fibers, perimysial inflammation, and increased endomysial connective tissue.Discussion: By demonstrating a clear correlation of various electromyographic and histopathologic findings, this study improves interpreting electrodiagnostic testing in myopathies, and serves as the basis to further assess the correlation between clinical, electromyographic, and histopathologic findings.

The Signaling Network Resulting in Ventilator-induced Diaphragm Dysfunction.

Mechanical ventilation (MV) is a life-saving measure for those incapable of adequately ventilating or oxygenating without assistance. Unfortunately, even brief periods of MV result in diaphragm weakness (i.e., ventilator-induced diaphragm dysfunction [VIDD]) that may render it difficult to wean the ventilator. Prolonged MV is associated with cascading complications and is a strong risk factor for death. Thus, prevention of VIDD may have a dramatic impact on mortality rates. Here, we summarize the current understanding of the pathogenic events underlying VIDD. Numerous alterations have been proven important in both human and animal MV diaphragm. These include protein degradation via the ubiquitin proteasome system, autophagy, apoptosis, and calpain activity-all causing diaphragm muscle fiber atrophy, altered energy supply via compromised oxidative phosphorylation and upregulation of glycolysis, and also mitochondrial dysfunction and oxidative stress. Mitochondrial oxidative stress in fact appears to be a central factor in each of these events. Recent studies by our group and others indicate that mitochondrial function is modulated by several signaling molecules, including Smad3, signal transducer and activator of transcription 3, and FoxO. MV rapidly activates Smad3 and signal transducer and activator of transcription 3, which upregulate mitochondrial oxidative stress. Additional roles may be played by angiotensin II and leaky ryanodine receptors causing elevated calcium levels. We present, here, a hypothetical scaffold for understanding the molecular pathogenesis of VIDD, which links together these elements. These pathways harbor several drug targets that could soon move toward testing in clinical trials. We hope that this review will shape a short list of the most promising candidates.

Pattern of myogenesis and vascular repair in early and advanced lesions of juvenile dermatomyositis

Regenerative processes that counteract perifascicular muscle atrophy and capillary loss in juvenile dermatomyositis (JDM) are not well characterized. We aimed to analyze the pattern of myo-regeneration in relation to vascular damage and repair in muscle specimens from JDM patients. Myogenic regulatory factors that are sequentially expressed during myogenesis were studied by immunohistochemistry. Capillary density, numbers of CD34+ endothelial progenitor cells within the endomysium and molecules implicated in angiogenesis were evaluated by double-immunofluorescence techniques. Myogenic regulatory factors were significantly up-regulated in JDM muscle exhibiting a different pattern in early and advanced lesions. In early lesions Pax7+ satellite cells and both MyoD+ and Myogenin+ myogenic cells were moderately increased. In lesions with advanced perifascicular atrophy Pax7+ satellite cells were numerous, but absence of MyoD+ in the context of increased Myogenin+ expression suggested a dysregulation of the myogenic regenerative pathway. The overall capillary density in JDM was decreased, but regions of capillary loss in advanced lesions alternated with focal increase of hyperplastic endothelial cells in early lesions. Up-regulation of endoglin in hyperplastic endothelial cells in conjunction with overexpression of TGF-β1 and VEGF suggested activation of neovascularization. Conversely, CD34+ endothelial progenitor cells were not increased arguing against relevant contribution to vascular repair. Our results demonstrate substantial induction of myogenesis in JDM. While the early phase of myogenesis appears to be associated with endothelial cell activation, an altered expression of MRFs in perifascicular regions with capillary depletion suggests an impairment of myogenic differentiation that may contribute to perifascicular muscle fiber atrophy in JDM.

CONGENITAL MYOPATHIES: NEMALINE AND TITINOPATHIES: P.236Congenital fiber type disproportion with mutations in tropomyosin 3 (TPM3) gene presenting as respiratory failure

Congenital fiber type disproportion(CFTD) is a rare subtype of congenital myopathy. CFTD is clinically heterogenous and histologically marked by hypotrophy of type I fibers compared with type 2 fibers. CFTD has been related with mutations in ACTA1, SEPN1, RYR1 and TPM3 genes. Particularly, TPM3 mutation was identified to the most frequent cause of CFTD and was also detected in cap myopathy and nemaline myopathy. We report autosomal dominant TPM3 missense mutations with CFTD in a family over two-generations. The two patients, the brother and sister, experienced first symptoms of muscle weakness in infancy with delayed motor milestones and followed a slowly progressive course. They presented generalized muscular hypotrophy, neck flexor muscle and distal limb muscle weakness, elongated face, retrognathia, high arched palate and scoliosis. Respiratory function became critical in two patients despite relatively good limb strength. The brother presented in respiratory arrest during sleep. The sister did not complain of difficulty on walking and climbing stairs but presented in respiratory failure needing ventilator. The finding of electromyography was compatible with myopathy and muscle biopsy showed type 1 fiber atrophy with predominance in the absence of other notable pathological findings such as nemaline rods and cap structures. TPM3 missense mutation c.502C>T (p.R168C) in exon 5 was identified by a target NGS. We confirmed CFTD caused by TPM3 mutation in this family. CFTD patients with mutation in TPM3 have been previously reported that many patients required nocturnal noninvasive ventilatory support despite remaining ambulant and several patients of these abruptly presented in respiratory failure. All patients in our family also showed sudden respiratory failure with relatively spared limb weakness. Therefore, it is clinically important for monitoring respiratory function regularly in CFTD patients with TPM3 mutation.

CONGENITAL MYOPATHIES (CNM): P.148Centronuclear myopathy with BIN1-like myopathology and DNM2 mutation

A limited number of genetically proven cases of BIN1-CNM have been described. DNM2-CNM is more frequent and the main biopsy characteristics is fibers with radiating sarcomeric strands along with nuclear centralization. To present a Brazilian case of DNM2 mutation and muscle biopsy with main features compatible with BIN1-CNM histopathology. Case report. A 58-year-old woman was born as a ``weak child'' with the ``eyes closed''. She had reduced spontaneous movements, delayed motor milestones and a motor limitation in follow other children in motor activities. Although motor weakness she was able to graduate in the university. Additional and more recent complains were hypersomnia and cognitive impairment. Consultation revealed: bilateral symmetrical ptosis and external ophthalmoplegia; motor deficit predominant at pelvic than scapular gilder; symmetric atrophy and weakness in distal lower limb. MFM scale had total score of 65.62% (D1=35.89%; D2=86.11%; D3=85.71%) and FVC was 32%. Recent Montreal cognitive assessment (MoCA) was 22/30. Cerebrospinal fluid showed protein of 82 mg/dL and Pandy positive. Biceps brachii biopsy showed several fibers with nuclear clustering centrally located and myofibers with one central nucleus. Type 1 fiber atrophy, type 2 hypertrophy and few fibers with radiating sarcomeric strands were also seen, thus predicting a CNM with BIN1 mutation. Surprisingly muscle MRI was compatible with DNM2-CNM and a cerebral MRI disclosed meningioma. A panel of new generation sequencing for myopathies showed a pathogenic variant in Ch19:10.904.508C>T (c.1105C>T) diagnosing a DNM2-CNM related. After a successful neurosurgery, the patient never acquired spontaneous ventilation, as was suggestive by MFM and FVC, remained in intensive care unit for four months, had multiples episodes of septicemia and died. Our case expands histopathological phenotypes of DNM2-CNM and reinforce the features of pelvis and legs MRI in DNM2 mutation.