Generation of Skeletal Muscle Organoids from Human Pluripotent Stem Cells

Various protocols have been proven effective in the directed differentiation of mouse and human pluripotent stem cells into skeletal muscles and used to study myogenesis. Current 2D myogenic differentiation protocols can mimic muscle development and its alteration under pathological conditions such as muscular dystrophies. 3D skeletal muscle differentiation approaches can, in addition, model the interaction between the various cell types within the developing organoid. Our protocol ensures the differentiation of human embryonic/induced pluripotent stem cells (hESC/hiPSC) into skeletal muscle organoids (SMO) via cells with paraxial mesoderm and neuromesodermal progenitors' identity and further production of organized structures of the neural plate margin and the dermomyotome. Continuous culturing omits neural lineage differentiation and promotes fetal myogenesis, including the maturation of fibroadipogenic progenitors and PAX7-positive myogenic progenitors. The PAX7 progenitors resemble the late fetal stages of human development and, based on single-cell transcriptomic profiling, cluster close to adult satellite cells of primary muscles. To overcome the limited availability of muscle biopsies from patients with muscular dystrophy during disease progression, we propose to use the SMO system, which delivers a stable population of skeletal muscle progenitors from patient-specific iPSCs to investigate human myogenesis in healthy and diseased conditions. Key features • Development of skeletal muscle organoid differentiation from human pluripotent stem cells, which recapitulates myogenesis. • Analysis of early embryonic and fetal myogenesis. • Provision of skeletal muscle progenitors for in vitro and in vivo analysis for up to 14 weeks of organoid culture. • In vitro myogenesis from patient-specific iPSCs allows to overcome the bottleneck of muscle biopsies of patients with pathological conditions.

Myopathies of endocrine origin: A review for physicians

Myopathies are a common manifestation of endocrine disorders. Endocrine myopathies are often overlooked while considering differential diagnoses in patients with musculoskeletal symptoms. The hindrance to mobility and the musculoskeletal discomfort owing to these myopathies are important causes of disability and depreciated quality of life in these patients. Endocrine myopathies occur due to the effects of endogenous or iatrogenic hormonal imbalance on skeletal muscle protein and glucose metabolism, disrupting the excitation-contraction coupling. Abnormalities of the pituitary, thyroid, parathyroid, adrenal, and gonadal hormones have all been associated with myopathies and musculoskeletal symptoms. Endocrine myopathies can either be the complication of a secondary endocrine disorder or a presenting symptom of a missed underlying disorder. Therefore, an underlying endocrine abnormality must always be excluded in all patients with musculoskeletal symptoms. This review presents a compilation of various endocrine myopathies, their etiopathogenesis, clinical presentation, diagnostic modalities, and treatment protocols.

Bioprinted Notch ligand to function as stem cell niche improves muscle regeneration in dystrophic muscle

299In Duchenne muscular dystrophy, dystrophic muscle phenotypes are closely associated with the exhaustion of muscle stem cells. Transplantation of muscle stem cells has been widely studied for improving muscle regeneration, but poor cell survival and self-renewal, rapid loss of stemness, and limited dispersion of grafted cells following transplantation have collectively hindered the overall success of this strategy. Optimized mechanisms for maintaining and improving stem cell function are naturally present in the microenvironment of the stem cell niche in healthy muscles. Therefore, one logical strategy toward improving stem cell function and efficiency of stem cell transplantation in diseased muscles would be the establishment of a microenvironment mimicking some key aspects of healthy native stem cell niches. Here, we applied inkjet-based bioprinting technology to engineer a mimicked artificial stem cell niche in dystrophic muscle, comprising stem cell niche regulating factors (Notch activator DLL1) bioprinted onto 3D DermaMatrix construct. The recombinant DLL1 protein, DLL1 (mouse): Fc (human) (rec), was applied here as the Notch activator. Bioprinted DermaMatrix construct was seeded with muscle stem cells in vitro, and increased stem cell maintenance and repressed myogenic differentiation process was observed. DLL1 bioprinted DermaMatrix construct was then engrafted into dystrophic muscle of mdx/scid mice, and the improved cell engraftment and progression of muscle regeneration was observed 10 days after engraftment. Our results demonstrated that bioprinting of Notch activator within 3D construct can be applied to serve as muscle stem cell niche and improve the efficacy of muscle stem cell transplantation in diseased muscle.

Proteomic and morphological insights and clinical presentation of two young patients with novel mutations of BVES (POPDC1)

Popeye domain containing protein 1 (POPDC1) is a highly conserved transmembrane protein essential for striated muscle function and homeostasis. Pathogenic variants in the gene encoding POPDC1 (BVES, Blood vessel epicardial substance) are causative for limb-girdle muscular dystrophy (LGMDR25), associated with cardiac arrhythmia. We report on four affected children (age 7-19 years) from two consanguineous families with two novel pathogenic variants in BVES c.457C>T(p.Q153X) and c.578T>G (p.I193S). Detailed analyses were performed on muscle biopsies from an affected patient of each family including immunofluorescence, electron microscopy and proteomic profiling. Cardiac abnormalities were present in all patients and serum creatine kinase (CK) values were variably elevated despite lack of overt muscle weakness. Detailed histological analysis of skeletal muscle, however indicated a myopathy with reduced sarcolemmal expression of POPDC1 accompanied by altered sarcolemmal and sarcoplasmatic dysferlin and Xin/XIRP1 abundance. At the electron microscopic level, the muscle fiber membrane was focally disrupted. The proteomic signature showed statistically significant dysregulation of 191 proteins of which 173 were increased and 18 were decreased. Gene ontology-term analysis of affected biological processes revealed - among others - perturbation of muscle fibril assembly, myofilament sliding, and contraction as well as transition between fast and slow fibers. In conclusion, these findings demonstrate that the phenotype of LGMDR25 is highly variable and also includes younger children with conduction abnormalities, no apparent muscular problems, and only mildly elevated CK values. Biochemical studies suggest that BVES mutations causing loss of functional POPDC1 can impede striated muscle function by several mechanisms.

Activity-based training with the Myosuit: a safety and feasibility study across diverse gait disorders

BACKGROUND

Physical activity is a recommended part of treatment for numerous neurological and neuromuscular disorders. Yet, many individuals with limited mobility are not able to meet the recommended activity levels. Lightweight, wearable robots like the Myosuit promise to facilitate functional ambulation and thereby physical activity. However, there is limited evidence of the safety and feasibility of training with such devices.

METHODS

Twelve participants with diverse motor disorders and the ability to walk for at least 10 m were enrolled in this uncontrolled case series study. The study protocol included five training sessions with a net training time of 45 min each. Primary outcomes were the feasibility of engaging in training with the Myosuit, the occurrence of adverse events, and participant retention. As secondary outcomes, we analyzed the walking speed using the 10-m Walk Test (10MWT) and for three participants, walking endurance using the 2-min Walk Tests.

RESULTS

Eight out of 12 participants completed the entire study protocol. Three participants withdrew from the study or were excluded for reasons unrelated to the study. One participant withdrew because of an unsafe feeling when walking with the Myosuit. No adverse events occurred during the study period for any of the participants and all scheduled trainings were completed. For five out of the eight participants that completed the full study, the walking speed when using the Myosuit was higher than to their baseline walking speed.

CONCLUSIONS

Activity-based training with the Myosuit appears to be safe, feasible, and well-tolerated by individuals with diverse motor disorders.

Differentially expressed marker genes and glycogen levels in pectoralis major of Ross308 broilers with wooden breast syndrome indicates stress, inflammation and hypoxic conditions

The occurrence of wooden breast (WB) in broiler production is increasing, but onset of its development is only described in part. In this study, we determined the regulation of marker genes related to oxidative stress in Ross308 broilers categorized as no-, mild- or severe-WB, on days 21 and 30 of production. The biochemical parameters, lactate dehydrogenase and pro- and macro-glycogen, were also determined. On day 21, breast meat from birds affected severely by WB had increased mRNA abundances of heat-shock protein 70, heme-oxygenase 1, cyclooxygenase 2, tumor necrosis factor 1, and hypoxia inducible factors as well as higher pH and lower dry matter contents. On day 30, breast meat from both mild and severely affected birds had increased mRNA for heme oxygenase 1, lactate dehydrogenase, and hypoxia inducible factor. Moreover, pro- and micro-glycogen, as well as the total pool of glycogen, were decreased compared with the non-WB birds. In conclusion, this study indicates oxidative stress, inflammation and hypoxic conditions in WB.

POGLUT1 biallelic mutations cause myopathy with reduced satellite cells, α-dystroglycan hypoglycosylation and a distinctive radiological pattern

Protein O-glucosyltransferase 1 (POGLUT1) activity is critical for the Notch signaling pathway, being one of the main enzymes responsible for the glycosylation of the extracellular domain of Notch receptors. A biallelic mutation in the POGLUT1 gene has been reported in one family as the cause of an adult-onset limb-girdle muscular dystrophy (LGMD R21; OMIM# 617232). As the result of a collaborative international effort, we have identified the first cohort of 15 patients with LGMD R21, from nine unrelated families coming from different countries, providing a reliable phenotype-genotype and mechanistic insight. Patients carrying novel mutations in POGLUT1 all displayed a clinical picture of limb-girdle muscle weakness. However, the age at onset was broadened from adult to congenital and infantile onset. Moreover, we now report that the unique muscle imaging pattern of "inside-to-outside" fatty degeneration observed in the original cases is indeed a defining feature of POGLUT1 muscular dystrophy. Experiments on muscle biopsies from patients revealed a remarkable and consistent decrease in the level of the NOTCH1 intracellular domain, reduction of the pool of satellite cells (SC), and evidence of α-dystroglycan hypoglycosylation. In vitro biochemical and cell-based assays suggested a pathogenic role of the novel POGLUT1 mutations, leading to reduced enzymatic activity and/or protein stability. The association between the POGLUT1 variants and the muscular phenotype was established by in vivo experiments analyzing the indirect flight muscle development in transgenic Drosophila, showing that the human POGLUT1 mutations reduced its myogenic activity. In line with the well-known role of the Notch pathway in the homeostasis of SC and muscle regeneration, SC-derived myoblasts from patients' muscle samples showed decreased proliferation and facilitated differentiation. Together, these observations suggest that alterations in SC biology caused by reduced Notch1 signaling result in muscular dystrophy in LGMD R21 patients, likely with additional contribution from α-dystroglycan hypoglycosylation. This study settles the muscular clinical phenotype linked to POGLUT1 mutations and establishes the pathogenic mechanism underlying this muscle disorder. The description of a specific imaging pattern of fatty degeneration and muscle pathology with a decrease of α-dystroglycan glycosylation provides excellent tools which will help diagnose and follow up LGMD R21 patients.

Salidroside mitigates skeletal muscle atrophy in rats with cigarette smoke-induced COPD by up-regulating myogenin and down-regulating myostatin expression

OBJECTIVES

The present study aimed at investigating the therapeutic effect of Salidroside on skeletal muscle atrophy in a rat model of cigarette smoking-induced chronic obstructive pulmonary disease (COPD) and its potential mechanisms.

METHODS

Male Wistar rats were randomized, and treated intraperitoneally (IP) with vehicle (injectable water) or a low, medium or high dose of Salidroside, followed by exposure to cigarette smoking daily for 16 weeks. A healthy control received vehicle injection and air exposure. Their lung function, body weights and gastrocnemius (GN) weights, grip strength and cross-section area (CSA) of individual muscular fibers in the GN were measured. The levels of TNF-α, IL-6, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) in serum and GN tissues as well as myostatin and myogenin expression in GN tissues were measured.

RESULTS

In comparison with that in the healthy control, long-term cigarette smoking induced emphysema, significantly impaired lung function, reduced body and GN weights and CSA values in rats, accompanied by significantly increased levels of TNF-α, IL-6 and MDA, but decreased levels of SOD and GSH in serum and GN tissues. Furthermore, cigarette smoking significantly up-regulated myostatin expression, but down-regulated myogenin expression in GN tissues. Salidroside treatment decreased emphysema, significantly ameliorated lung function, increased antioxidant, but reduced MDA, IL-6 and TNF-α levels in serum and GN tissues of rats, accompanied by decreased myostain, but increased myogenin expression in GN tissues.

CONCLUSION

Salidroside mitigates the long-term cigarette smoking-induced emphysema and skeletal muscle atrophy in rats by inhibiting oxidative stress and inflammatory responses and regulating muscle-specific transcription factor expression.

Altered myogenesis and premature senescence underlie human TRIM32-related myopathy

TRIM32 is a E3 ubiquitin -ligase containing RING, B-box, coiled-coil and six C-terminal NHL domains. Mutations involving NHL and coiled-coil domains result in a pure myopathy (LGMD2H/STM) while the only described mutation in the B-box domain is associated with a multisystemic disorder without myopathy (Bardet-Biedl syndrome type11), suggesting that these domains are involved in distinct processes. Knock-out (T32KO) and knock-in mice carrying the c.1465G > A (p.D489N) involving the NHL domain (T32KI) show alterations in muscle regrowth after atrophy and satellite cells senescence. Here, we present phenotypical description and functional characterization of mutations in the RING, coiled-coil and NHL domains of TRIM32 causing a muscle dystrophy. Reduced levels of TRIM32 protein was observed in all patient muscle studied, regardless of the type of mutation (missense, single amino acid deletion, and frameshift) or the mutated domain. The affected patients presented with variable phenotypes but predominantly proximal weakness. Two patients had symptoms of both muscular dystrophy and Bardet-Biedl syndrome. The muscle magnetic resonance imaging (MRI) pattern is highly variable among patients and families. Primary myoblast culture from these patients demonstrated common findings consistent with reduced proliferation and differentiation, diminished satellite cell pool, accelerated senescence of muscle, and signs of autophagy activation.

COL6A1 mutation leading to Bethlem myopathy with recurrent hematuria: a case report

Background

Collagen VI-related myopathies are a spectrum of muscular diseases with features of muscle weakness and atrophy, multiple contractures of joints, distal hyperextensibility, severe respiratory dysfunction and cutaneous alterations, attributable to mutations in the COL6A1, COL6A2, and COL6A3 genes. However, no case of collagen VI mutations with hematuria has been reported. We report a 14-year-old boy who had both Bethlem myopathy and recurrent hematuria and who carried a known de novo COL6A1 missense mutation c.877G > A (p.G293R).

Case presentation

The patient was a 14-year-old boy presenting with muscle weakness from 3 years of age without any family history. Six months before admission, he developed recurrent gross hematuria, three bouts in total, with the presence of blood clots in the urine. Next-generation sequencing of his whole-exome was performed. The result of sequencing revealed a de novo heterozygous G-to-A nucleotide substitution at position 877 in exon 10 of the COL6A1 gene. After treatment, the hematuria healed, but the muscle weakness failed to improve.

Conclusions

Hematuria in Bethlem myopathy can be caused by COL6 mutations, which may be related to the aberrant connection between collagen VI and collagen IV.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1263-0) contains supplementary material, which is available to authorized users.

IP3 receptor blockade restores autophagy and mitochondrial function in skeletal muscle fibers of dystrophic mice

Duchenne muscular dystrophy (DMD) is characterized by a severe and progressive destruction of muscle fibers associated with altered Ca²⁺ homeostasis. We have previously shown that the IP₃ receptor (IP₃R) plays a role in elevating basal cytoplasmic Ca²⁺ and that pharmacological blockade of IP₃R restores muscle function. Moreover, we have shown that the IP₃R pathway negatively regulates autophagy by controlling mitochondrial Ca²⁺ levels. Nevertheless, it remains unclear whether IP₃R is involved in abnormal mitochondrial Ca²⁺ levels, mitochondrial dynamics, or autophagy and mitophagy observed in adult DMD skeletal muscle. Here, we show that the elevated basal autophagy and autophagic flux levels were normalized when IP₃R was downregulated in mdx fibers. Pharmacological blockade of IP₃R in mdx fibers restored both increased mitochondrial Ca²⁺ levels and mitochondrial membrane potential under resting conditions. Interestingly, mdx mitochondria changed from a fission to an elongated state after IP₃R knockdown, and the elevated mitophagy levels in mdx fibers were normalized. To our knowledge, this is the first study associating IP₃R1 activity with changes in autophagy, mitochondrial Ca²⁺ levels, mitochondrial membrane potential, mitochondrial dynamics, and mitophagy in adult mouse skeletal muscle. Moreover, these results suggest that increased IP₃R activity in mdx fibers plays an important role in the pathophysiology of DMD. Overall, these results lead us to propose the use of specific IP₃R blockers as a new pharmacological treatment for DMD, given their ability to restore both autophagy/mitophagy and mitochondrial function.

Local Texture Anisotropy as an Estimate of Muscle Quality in Ultrasound Imaging

This study introduces local pattern texture anisotropy as a novel parameter to differentiate healthy and disordered muscle and to gauge the severity of muscle impairments based on B-mode ultrasound images. Preliminary human results are also presented. A local pattern texture anisotropy index (TAI) was computed in one region of interest in the short head of the biceps brachii. The effects of gain settings and box sizes required for TAI computation were investigated. Between-day reliability was studied in patients with sporadic inclusion body myositis (n = 26). The ability of the TAI to discriminate dystrophic from healthy muscle was evaluated in patients with Duchenne muscular dystrophy and healthy controls (n = 16). TAI values were compared with a gray-scale index (GSI). TAI values were less influenced by gain settings than were GSI values. TAI had lower between-day variability (typical error = 2.3%) compared with GSI (typical error = 2.3% vs. 8.3%, respectively). Patients with Duchenne muscular dystrophy had lower TAIs than controls (0.76 ± 0.06 vs. 0.87 ± 0.03, respectively, p <0.05). At 40% gain, TAI values correlated with percentage predicted elbow flexor strength in inclusion body myositis (R = 0.63, p <0.001). The TAI may be a promising addition to other texture-based approaches for quantitative muscle ultrasound imaging.

Cortical involvement in myopathies: Insights from transcranial magnetic stimulation

OBJECTIVE

There is increasing evidence that an involvement of central nervous system (CNS) can occur in several myopathies. Transcranial magnetic stimulation (TMS) may represent a valuable tool for investigating important neurophysiological and pathophysiological aspects of cortical involvement in neuromuscular disorders. In this review paper we aimed to perform a systematic search of the studies employing TMS techniques in subjects suffering from myopathies.

METHODS

A literature search was conducted using PubMed and Embase. We identified and reviewed 9 articles matching the inclusion criteria. One hundred twenty patients were included in these studies, which have applied TMS in patients with muscle disorders.

RESULTS

To date, a few studies using TMS have been performed in myopathic patients and detected subclinical abnormalities in cortical reactivity and plasticity. The most consistent finding was a decrease in intracortical inhibition, which likely represents a non-specific compensatory mechanism of the CNS in an attempt to overcome the muscle deficit through an increase of the motor cortex output to deficient muscles.

CONCLUSIONS

Application of TMS to characterize the pathophysiology of the CNS in these subjects appears to be safe and may lead to the development of valuable biomarkers. Well-defined motor cortical excitability patterns can be identified in the different muscle diseases, even if preliminary findings should be confirmed in future studies in larger cohorts of patients.

SIGNIFICANCE

TMS studies may shed new light on the physiological and pathophysiological mechanisms underlying the cortical involvement in muscle disorders.

Gene co-expression network analysis of dysferlinopathy: Altered cellular processes and functional prediction of TOR1AIP1, a novel muscular dystrophy gene

Dysferlinopathy, caused by a dysferlin gene mutation, is a clinically heterogeneous autosomal recessive muscle disease characterized by progressive muscle degeneration. The dysferlin protein's functions and dysferlinopathy disease pathogenesis are not fully explored, and there is no specific treatment available that can alter the disease progression. This study uses publicly available dysferlinopathy patient microarray data to construct a gene co-expression network and investigates significant cellular pathways and their key players in dysferlinopathy pathogenesis. Extracellular matrix deposition, inflammation, mitochondrial abnormalities and protein degradation were found to be important in dysferlinopathy. Out of the hub genes, OXR1 and TIMP1 were selected through literature search as candidate genes for possible biomarker and molecular therapeutic target studies. A recently identified muscular dystrophy gene TOR1AIP1 was detected as a hub gene in dysferlinopathy. Co-expression and protein sequence feature analysis were adopted to predict TOR1AIP1's function. Our results suggest that LAP1 protein encoded by TOR1AIP1 may play a role in protein degradation possibly through transcriptional regulation in muscle tissue. These findings extend dysferlinopathy pathogenesis by presenting key genes and also suggest a novel function for a poorly characterized gene.

Muscle imaging in muscle dystrophies produced by mutations in the EMD and LMNA genes

Identifying the mutated gene that produces a particular muscle dystrophy is difficult because different genotypes may share a phenotype and vice versa. Muscle MRI is a useful tool to recognize patterns of muscle involvement in patients with muscle dystrophies and to guide the diagnosis process. The radiologic pattern of muscle involvement in patients with mutations in the EMD and LMNA genes has not been completely established. Our objective is to describe the pattern of muscle fatty infiltration in patients with mutations in the EMD and in the LMNA genes and to search for differences between the two genotypes that could be helpful to guide the genetic tests. We conducted a national multicenter study in 42 patients, 10 with mutations in the EMD gene and 32 with mutations in the LMNA gene. MRI or CT was used to study the muscles from trunk to legs. Patients had a similar pattern of fatty infiltration regardless of whether they had the mutation in the EMD or LMNA gene. The main muscles involved were the paravertebral, glutei, quadriceps, biceps, semitendinosus, semimembranosus, adductor major, soleus, and gastrocnemius. Involvement of peroneus muscle, which was more frequently affected in patients with mutations in the EMD gene, was useful to differentiate between the two genotypes. Muscle MRI/CT identifies a similar pattern of muscle fatty infiltration in patients with mutations in the EMD or the LMNA genes. The involvement of peroneus muscles could be useful to conduct genetic analysis in patients with an EDMD phenotype.

Computer-based assessment for facioscapulohumeral dystrophy diagnosis

The paper presents a computer-based assessment for facioscapulohumeral dystrophy (FSHD) diagnosis through characterisation of the fat and oedema percentages in the muscle region. A novel multi-slice method for the muscle-region segmentation in the T1-weighted magnetic resonance images is proposed using principles of the live-wire technique to find the path representing the muscle-region border. For this purpose, an exponential cost function is used that incorporates the edge information obtained after applying the edge-enhancement algorithm formerly designed for the fingerprint enhancement. The difference between the automatic segmentation and manual segmentation performed by a medical specialists is characterised using the Zijdenbos similarity index, indicating a high accuracy of the proposed method. Finally, the fat and oedema are quantified from the muscle region in the T1-weighted and T2-STIR magnetic resonance images, respectively, using the fuzzy c-mean clustering approach for 10 FSHD patients.

Nitric oxide and muscle repair: multiple actions converging on therapeutic efficacy

Muscular dystrophies comprise an heterogeneous group of diseases characterised by primary wasting of skeletal muscle, in the most severe forms leading to progressive paralysis and death. Current therapies for these conditions are extremely limited and based on corticosteroids that bear significant side effects. Several studies have proposed possible alternative strategies, ranging from cell and gene therapy to more classical pharmacological approaches. Nitric oxide is a gaseous messenger involved in many mechanisms responsible for preserving muscle function and stimulating muscle repair. We herein review the most recent pre-clinical and clinical findings that open new prospective for the development of nitric oxide as a therapeutic tool for muscular dystrophies.