Angiogenesis as a novel therapeutic strategy for Duchenne muscular dystrophy through decreased ischemia and increased satellite cells

Estrogen-related Receptor Signaling in Skeletal Muscle Fitness

Skeletal muscle is a highly plastic tissue that can alter its metabolic and contractile features, as well as regenerative potential in response to exercise and other conditions. Multiple signaling factors including metabolites, kinases, receptors, and transcriptional factors have been studied in the regulation of skeletal muscle plasticity. Recently, estrogen-related receptors (ERRs) have emerged as a critical transcriptional hub in control of skeletal muscle homeostasis. ERRα and ERRγ - the two highly expressed ERR sub-types in the muscle respond to various extracellular cues such as exercise, hypoxia, fasting and dietary factors, in turn regulating gene expression in the skeletal muscle. On the other hand, conditions such as diabetes and muscular dystrophy suppress expression of ERRs in the skeletal muscle, likely contributing to disease progression. We highlight key functions of ERRs in the skeletal muscle including the regulation of fiber type, mitochondrial metabolism, vascularization, and regeneration. We also describe how ERRs are regulated in the skeletal muscle, and their interaction with important muscle regulators (e. g. AMPK and PGCs). Finally, we identify critical gaps in our understanding of ERR signaling in the skeletal muscle, and suggest future areas of investigation to advance ERRs as potential targets for function promoting therapeutics in muscle diseases.

VEGF overexpressed mesoangioblasts enhance urethral and vaginal recovery following simulated vaginal birth in rats

Vaginal birth causes pelvic floor injury which may lead to urinary incontinence. Cell therapy has been proposed to assist in functional recovery. We aim to assess if intra-arterial injection of rat mesoangioblasts (MABs) and stable Vascular Endothelial Growth Factor (VEGF)-expressing MABs, improve recovery of urethral and vaginal function following simulated vaginal delivery (SVD). Female rats (n = 86) were assigned to either injection of saline (control), allogeneic-MABs (MABs^allo), autologous-MABs (MABs^auto) or allogeneic-MABs transduced to stably expressed VEGF (MABs^allo-VEGF). One hour after SVD, 0.5 × 10⁶ MABs or saline were injected into the aorta. Primary outcome was urethral (7d and 14d) and vaginal (14d) function; others were bioluminescent imaging for cell tracking (1, 3 and 7d), morphometry (7, 14 and 60d) and mRNAseq (3 and 7d). All MABs injected rats had external urethral sphincter and vaginal function recovery within 14d, as compared to only half of saline controls. Functional recovery was paralleled by improved muscle regeneration and microvascularization. Recovery rate was not different between MABs^allo and MABs^auto. MABs^allo-VEGF accelerated functional recovery and increased GAP-43 expression at 7d. At 3d we detected major transcriptional changes in the urethra of both MABs^allo and MABs^allo-VEGF-injected animals, with upregulation of Rho/GTPase activity, epigenetic factors and dendrite development. MABS^allo also upregulated transcripts that encode proteins involved in myogenesis and downregulated pro-inflammatory processes. MABs^allo-VEGF also upregulated transcripts that encode proteins involved in neuron development and downregulated genes involved in hypoxia and oxidative stress. At 7d, urethras of MABs^allo-VEGF-injected rats showed downregulation of oxidative and inflammatory response compared to MABS^allo. Intra-arterial injection of MABs^allo-VEGF enhances neuromuscular regeneration induced by untransduced MABs and accelerates the functional urethral and vaginal recovery after SVD.

PI(4,5)P2-dependent regulation of endothelial tip cell specification contributes to angiogenesis

Dynamic positioning of endothelial tip and stalk cells, via the interplay between VEGFR2 and NOTCH signaling, is essential for angiogenesis. VEGFR2 activates PI3K, which phosphorylates PI(4,5)P₂ to PI(3,4,5)P₃, activating AKT; however, PI3K/AKT does not direct tip cell specification. We report that PI(4,5)P₂ hydrolysis by the phosphoinositide-5-phosphatase, INPP5K, contributes to angiogenesis. INPP5K ablation disrupted tip cell specification and impaired embryonic angiogenesis associated with enhanced DLL4/NOTCH signaling. INPP5K degraded a pool of PI(4,5)P₂ generated by PIP5K1C phosphorylation of PI(4)P in endothelial cells. INPP5K ablation increased PI(4,5)P₂, thereby releasing β-catenin from the plasma membrane, and concurrently increased PI(3,4,5)P₃-dependent AKT activation, conditions that licensed DLL4/NOTCH transcription. Suppression of PI(4,5)P₂ in INPP5K-siRNA cells by PIP5K1C-siRNA, restored β-catenin membrane localization and normalized AKT signaling. Pharmacological NOTCH or AKT inhibition in vivo or genetic β-catenin attenuation rescued angiogenesis defects in INPP5K-null mice. Therefore, PI(4,5)P₂ is critical for β-catenin/DLL4/NOTCH signaling, which governs tip cell specification during angiogenesis.

Vascular therapy for Duchenne muscular dystrophy (DMD)

Duchenne muscular dystrophy (DMD) is a progressive disease characterized by the wasting of the muscles that eventually lead to difficulty moving and, ultimately, premature death from heart and respiratory complications. DMD deficiency is caused by mutations in the gene encoding dystrophin, which prevents skeletal muscle, cardiac muscle, and other cells from producing the functional protein. Located on the cytoplasmic face of the plasma membrane of muscle fibers, dystrophin serves as a component of the dystrophin glycoprotein complex (DGC), mechanically reinforces the sarcolemma, and stabilizes the DGC, preventing it from contraction-mediated muscle degradation. In DMD muscle, dystrophin deficiency leads to progressive fibrosis, myofiber damage, chronic inflammation, and dysfunction of the mitochondria and muscle stem cells. Currently, DMD is incurable, and treatment involves the administration of glucocorticoids in order to delay disease progression. In the presence of developmental delay, proximal weakness, and elevated serum creatine kinase levels, a definitive diagnosis can usually be made after an extensive review of the patient's history and physical examination, as well as confirmation through muscle biopsy or genetic testing. Current standards of care include the use of corticosteroids to prolong ambulation and delay the onset of secondary complications, including respiratory muscle and cardiac functions. However, different studies have been carried out to show the relationship between vascular density and impaired angiogenesis in the pathogenesis of DMD. Several recent studies on DMD management are vascular targeted and focused on ischemia as a culprit for the pathogenesis of DMD. This review critically discusses approaches-such as modulation of nitric oxide (NO) or vascular endothelial growth factor (VEGF)-related pathways-to attenuate the dystrophic phenotype and enhance angiogenesis.

Re-examination of therapeutic management of muscular dystrophies using a vascular smooth muscle-centered approach

In contrast to the long-standing focus on the pathophysiology of skeletal muscles in the hunt for a cure for Duchenne muscular dystrophy (DMD), we opine that the malfunctioning of dystrophin produced by vascular smooth muscle is a major contributor to the pathology of the illness. We believe that a biological response modifier glucan (BRMG), which has been shown in clinical studies of DMD to boost the expression of vascular smooth muscle dystrophin and provide anti-fibrotic and anti-inflammatory effects, may play a key role in reducing the pathogenesis of DMD. According to the evaluation of biomarkers, this BRMG, which is safe and side-effect-free, reduces the pathogenesis of DMD. We describe the possible mechanisms of action by which this BRMG helps in alleviating the symptoms of DMD by targeting smooth muscle dystrophin, in addition to its advantages over other therapeutic modalities, as well as how it can serve as a valuable adjunct to existing therapies. We suggest that using BRMG adjuncts that target smooth muscle dystrophin would be a potential therapeutic approach that prolongs the lifespan and extends the duration of ambulation from the onset of DMD. Further studies are needed to validate this hypothesis.

Single cell sequencing maps skeletal muscle cellular diversity as disease severity increases in dystrophic mouse models

Duchenne muscular dystrophy (DMD) is caused by out-of-frame mutations in the DMD gene resulting in the absence of a functional dystrophin protein, leading to a devastating and progressive lethal muscle-wasting disease. Little is known about cellular heterogeneity as disease severity increases. Advances in single-cell RNA sequencing (scRNA-seq) enabled us to explore skeletal muscle-resident cell populations in healthy, dystrophic, and severely dystrophic mouse models. We found increased frequencies of activated fibroblasts, fibro-adipogenic progenitor cells, and pro-inflammatory macrophages in dystrophic gastrocnemius muscles and an upregulation of extracellular matrix genes on endothelial cells in dystrophic and severely dystrophic muscles. We observed a pronounced risk of clotting, especially in the severely dystrophic mice with increased expression of plasminogen activator inhibitor-1 in endothelial cells, indicating endothelial cell impairment as disease severity increases. This work extends our understanding of the severe nature of DMD which should be considered when developing single or combinatorial approaches for DMD.

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scRNA-seq reveals cell differences in healthy, dystrophic, and severely dystrophic muscles

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Increased frequency of activated fibroblasts and FAP cells in dystrophic environments

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Co-existence of pro- and anti-inflammatory signatures in dystrophic environments

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Endothelial cell impairment is evident in severely dystrophic environment

Skeletal muscle and metabolic flexibility in response to changing energy demands in wild birds

Phenotypically plastic responses of animals to adjust to environmental variation are pervasive. Reversible plasticity (i.e., phenotypic flexibility), where adult phenotypes can be reversibly altered according to prevailing environmental conditions, allow for better matching of phenotypes to the environment and can generate fitness benefits but may also be associated with costs that trade-off with capacity for flexibility. Here, we review the literature on avian metabolic and muscle plasticity in response to season, temperature, migration and experimental manipulation of flight costs, and employ an integrative approach to explore the phenotypic flexibility of metabolic rates and skeletal muscle in wild birds. Basal (minimum maintenance metabolic rate) and summit (maximum cold-induced metabolic rate) metabolic rates are flexible traits in birds, typically increasing with increasing energy demands. Because skeletal muscles are important for energy use at the organismal level, especially to maximum rates of energy use during exercise or shivering thermogenesis, we consider flexibility of skeletal muscle at the tissue and ultrastructural levels in response to variations in the thermal environment and in workloads due to flight exercise. We also examine two major muscle remodeling regulatory pathways: myostatin and insulin-like growth factor -1 (IGF-1). Changes in myostatin and IGF-1 pathways are sometimes, but not always, regulated in a manner consistent with metabolic rate and muscle mass flexibility in response to changing energy demands in wild birds, but few studies have examined such variation so additional study is needed to fully understand roles for these pathways in regulating metabolic flexibility in birds. Muscle ultrastrutural variation in terms of muscle fiber diameter and associated myonuclear domain (MND) in birds is plastic and highly responsive to thermal variation and increases in workload, however, only a few studies have examined ultrastructural flexibility in avian muscle. Additionally, the relationship between myostatin, IGF-1, and satellite cell (SC) proliferation as it relates to avian muscle flexibility has not been addressed in birds and represents a promising avenue for future study.

The Protective Effects of γ-Tocotrienol on Muscle Stem Cells Through Inhibiting Reactive Oxidative Stress Production

Pseudotrophic muscular dystrophy is a common clinical skeletal muscle necrotic disease, among which Duchenne muscular dystrophy (DMD) is the predominant. For such diseases, there is no clinically effective treatment, which is only symptomatic or palliative treatment. Oxidative stress and chronic inflammation are common pathological features of DMD. In recent years, it has been found that the pathophysiological changes of skeletal muscle in DMD mice are related to muscle stem cell failure. In the present study, we established a DMD mice model and provided tocotrienol (γ-tocotrienol, GT3), an antioxidant compound, to explore the relationship between the physiological state of muscle stem cells and oxidative stress. The results showed that the application of GT3 can reduce ROS production and cellular proliferation in the muscle stem cells of DMD mice, which is beneficial to promote the recovery of muscle stem cell function in DMD mice. GT3 treatment improved the differentiation ability of muscle stem cells in DMD mice with increasing numbers of MyoD⁺ cells. GT3 application significantly decreased percentages of CD45⁺ cells and PDGFRα⁺ fibro-adipogenic progenitors in the tibialis anterior of DMD mice, indicating that the increased inflammation and fibro-adipogenic progenitors were attenuated in GT3-treated DMD mice. These data suggest that increased ROS production causes dysfunctional muscle stem cell in DMD mice, which might provide a new avenue to treat DMD patients in the clinic.

Hypoxia and Hypoxia-Inducible Factor Signaling in Muscular Dystrophies: Cause and Consequences

Muscular dystrophies (MDs) are a group of inherited degenerative muscle disorders characterized by a progressive skeletal muscle wasting. Respiratory impairments and subsequent hypoxemia are encountered in a significant subgroup of patients in almost all MD forms. In response to hypoxic stress, compensatory mechanisms are activated especially through Hypoxia-Inducible Factor 1 α (HIF-1α). In healthy muscle, hypoxia and HIF-1α activation are known to affect oxidative stress balance and metabolism. Recent evidence has also highlighted HIF-1α as a regulator of myogenesis and satellite cell function. However, the impact of HIF-1α pathway modifications in MDs remains to be investigated. Multifactorial pathological mechanisms could lead to HIF-1α activation in patient skeletal muscles. In addition to the genetic defect per se, respiratory failure or blood vessel alterations could modify hypoxia response pathways. Here, we will discuss the current knowledge about the hypoxia response pathway alterations in MDs and address whether such changes could influence MD pathophysiology.

VEGFR-1/Flt-1 inhibition increases angiogenesis and improves muscle function in a mouse model of Duchenne muscular dystrophy

Duchenne muscular dystrophy is characterized by structural degeneration of muscle, which is exacerbated by localized functional ischemia due to loss of nitric oxide synthase-induced vasodilation. Treatment strategies aimed at increasing vascular perfusion have been proposed. Toward this end, we have developed monoclonal antibodies (mAbs) that bind to the vascular endothelial growth factor (VEGF) receptor VEGFR-1 (Flt-1) and its soluble splice variant isoform (sFlt-1) leading to increased levels of free VEGF and proangiogenic signaling. The lead chimeric mAb, 21B3, had high affinity and specificity for both human and mouse sFlt-1 and inhibited VEGF binding to sFlt-1 in a competitive manner. Proof-of-concept studies in the mdx mouse model of Duchenne muscular dystrophy showed that intravenous administration of 21B3 led to elevated VEGF levels, increased vascularization and blood flow to muscles, and decreased fibrosis after 6-12 weeks of treatment. Greater muscle strength was also observed after 4 weeks of treatment. A humanized form of the mAb, 27H6, was engineered and demonstrated a comparable pharmacologic effect. Overall, administration of anti-Flt-1 mAbs in mdx mice inhibited the VEGF:Flt-1 interaction, promoted angiogenesis, and improved muscle function. These studies suggest a potential therapeutic benefit of Flt-1 inhibition for patients with Duchenne muscular dystrophy.

Combined gene therapy via VEGF and mini-dystrophin synergistically improves pathologies in temporalis muscle of dystrophin/utrophin double knockout mice

Duchenne muscular dystrophy (DMD) is a severe X-linked inherited muscular disorder characterized by the loss of dystrophin. We have previously shown that monogene therapy using the mini-dystrophin gene improves muscle function in DMD. However, chronic inflammation plays an important role in progressive muscle degeneration in DMD as well. Vascular endothelial growth factor (VEGF) has been used to enhance muscle vasculature, reduce local inflammation and improve DMD muscle function. Temporalis muscles are the key skeletal muscles for mastication and loss of their function negatively affects DMD patient quality of life by reducing nutritional intake, but little is known about the pathology and treatment of the temporalis muscle in DMD. In this work, we tested the hypothesis that the combined delivery of the human mini-dystrophin and human VEGF genes to the temporalis muscles using separate recombinant adeno-associated viral (rAAV) vectors will synergistically improve muscle function and pathology in adult male dystrophin/utrophin double-knockout (mdx/utrn+/-) mice. The experimental mice were divided into four groups including: dystrophin + VEGF combined, dystrophin only, VEGF only and PBS control. After 2 months, gene expression and histological analysis of the temporalis muscles showed a synergistic improvement in temporalis muscle pathology and function coincident with increased restoration of dystrophin-associated protein complexes and nNOS in the dystrophin + VEGF combined group. We also observed significantly reduced inflammatory cell infiltration, central nucleation, and fibrosis in the dystrophin + VEGF combined group. We have demonstrated the efficacy of combined rAAV-mediated dystrophin and VEGF treatment of temporalis muscles in a DMD mouse model.

Measuring the effects of exercise in neuromuscular disorders: a systematic review and meta-analyses

Background: The benefit and safety of exercise training for patients with neuromuscular disorders (NMDs) has long been a contentious topic. This is, in part, due to recognised challenges associated with rare diseases including small and heterogenous patient populations. We performed a systematic review and meta-analyses to evaluate the effectiveness and safety of interventional exercise and establish minimal clinically important differences (MCID) in outcomes to facilitate clinical interpretation. Methods: We searched six databases from inception to Mar 2018. Aerobic, strength, and combined (aerobic and strength) intervention were eligible. Meta-analyses compared outcomes at baseline with those after at least six weeks (before-after exercise within individuals). A further meta-analysis compared outcomes before-after exercise between groups (exercise training versus usual care). Disease heterogeneity was explored using a random effect model. This study was registered (PROSPERO, CRD42018102183). An interactive database was developed to facilitate full interrogations of data. Results: We identified 130 articles describing 1,805 participants with 35 different forms of NMD. Of these studies, 76 were suitable for meta-analyses. Within group and between group meta-analyses detected an increase in peak aerobic capacity (p=0·04), and peak power (p=0·01). Six-minute walk test (p=0·04), sit-to-stand (STS) (repetitions) (p=0·03), STS (seconds) (p=0·04), rise from supine (p=0·008), SF-36 (p=0·0003), fatigue severity (p=<0·0001), citrate synthase (p=0·0002), central nuclei (p=0·04), type 1 (p=0·002) and type II muscle fibre area (p=0·003), were only able to detect change within group meta-analyses. Substantial I 2 statistic heterogeneity was revealed for STS (seconds) ( I²=58·5%; p=0·04) and citrate synthase ( I²=70·90%; p=0·002), otherwise heterogeneity for all outcomes was low. No study-related serious adverse events were reported nor significant increases in creatine kinase. Conclusions: Exercise training in patients with NMDs appears to cause no harm across a range of outcomes. With the emergence of new therapeutic strategies, defining MCID is vital in informing future clinical trial design.

HIF-hypoxia signaling in skeletal muscle physiology and fibrosis

Hypoxia refers to the decrease in oxygen tension in the tissues, and the central effector of the hypoxic response is the transcription factor Hypoxia-Inducible Factor α (HIF1-α). Transient hypoxia in acute events, such as exercising or regeneration after damage, play an important role in skeletal muscle physiology and homeostasis. However, sustained activation of hypoxic signaling is a feature of skeletal muscle injury and disease, which can be a consequence of chronic damage but can also increase the severity of the pathology and worsen its outcome. Here, we review evidence that supports the idea that hypoxia and HIF-1α can contribute to the establishment of fibrosis in skeletal muscle through its crosstalk with other profibrotic factors, such as Transforming growth factor β (TGF-β), the induction of profibrotic cytokines expression, as is the case of Connective Tissue Growth Factor (CTGF/CCN2), or being the target of the Renin-angiotensin system (RAS).

Atherosclerosis and the Capillary Network; Pathophysiology and Potential Therapeutic Strategies

Atherosclerosis and associated ischemic organ dysfunction represent the number one cause of mortality worldwide. While the key drivers of atherosclerosis, arterial hypertension, hypercholesterolemia and diabetes mellitus, are well known disease entities and their contribution to the formation of atherosclerotic plaques are intensively studied and well understood, less effort is put on the effect of these disease states on microvascular structure an integrity. In this review we summarize the pathological changes occurring in the vascular system in response to prolonged exposure to these major risk factors, with a particular focus on the differences between these pathological alterations of the vessel wall in larger arteries as compared to the microcirculation. Furthermore, we intend to highlight potential therapeutic strategies to improve microvascular function during atherosclerotic vessel disease.

Hypoxia-inducible factor-prolyl hydroxylase inhibitor ameliorates myopathy in a mouse model of chronic kidney disease

Muscle wasting and diminished physical performance contribute to the morbidity and mortality of chronic kidney disease (CKD), for which no curative therapy exists. Accumulating evidence indicates that impaired angiogenesis occurs in the muscles of CKD models. Therefore, proangiogenesis therapy is considered a potentially effective strategy for limiting CKD-associated myopathy. Hypoxia-inducible factor (HIF)-prolyl hydroxylase inhibitor (HIF-PHI) stabilizes HIF and enhances muscle angiogenesis during acute ischemia; however, little evidence was available from CKD models. Here, we assessed whether pharmacological activation of HIF by MK-8617 (MK), a novel orally active HIF-PHI, improves CKD-associated myopathy. Mice were divided into sham or CKD groups, and CKD mice were subdivided into CKD + vehicle or MK treatment groups (1.5, 5, or 12.5 mg/kg for 12 wk). In CKD mice, skeletal muscle mass, mitochondrial amount, and exercise capacity decreased compared with sham mice. Compared with the CKD + vehicle group, low (1.5 mg/kg) and medium (5 mg/kg) doses of MK, but not the high dose (12.5 mg/kg), significantly restored these changes and was accompanied by incremental increases in HIF-1α. Furthermore, increased capillary density and area were observed in a MK dose-dependent manner, which is likely related to an improved VEGF response in the skeletal muscle of CKD mice. In addition, macrophage and proinflammatory cytokines, including monocyte chemoattractant protein 1, TNF-α, and IL-6, significantly increased in the high-dose MK group. These results indicate that HIF-PHI provides a potential therapeutic strategy to improve CKD-associated myopathy.

Tempol treatment shows phenotype improvement in mdx mice

Considering potential Tempol effects on mdx muscle fibers, in this study we evaluated its effects on relevant dystrophic phenotypic characteristics, such as muscle degeneration, inflammatory process and angiogenesis, which as yet have not been investigated. Mdx mice were randomly assigned into three groups: mdxS, the control group receiving intraperitoneal (i.p.) injections of saline solution (100μL); mdxP, positive control group receiving prednisolone (1mg/kg) by oral gavage; and mdxT, treated group receiving i.p. injections of tempol (100 mg/kg). C57BL/10 mice were also used as controls. Tempol treatment promoted gain in muscle strength and reduced myonecrosis and inflammatory response in the dystrophic diaphragm (DIA) and biceps brachii (BB) muscles. No evidence of Tempol's beneficial performance on angiogenesis in DIA and BB mdx muscles was found. The findings presented here show that Tempol treatment improves dystrophic phenotype, supporting its use as a potential therapeutic strategy in DMD.

Biochemical Changes in Blood of Patients with Duchenne Muscular Dystrophy Treated with Granulocyte-Colony Stimulating Factor

Introduction

In addition to the “gold standard” of therapy—steroids and gene therapy–there are experimental trials using granulocyte-colony stimulating factor (G-CSF) for patients with Duchenne muscular dystrophy (DMD). The aim of this study was to present the biochemical changes in blood after repeating cycles of granulocyte-colony stimulating factor G-CSF therapy in children with DMD.

Materials and Methods

Nineteen patients, aged 5 to 15 years, with diagnosed DMD confirmed by genetic tests, participated; nine were in wheelchairs, and ten were mobile and independent. Patients had a clinical assessment and laboratory tests to evaluate hematological parameters and biochemistry. G-CSF (5μg/kg/day) was given subcutaneously for five days during five nonconsecutive months over the course of a year.

Results

We found a significant elevation of white blood cells, and the level of leucocytes returned to norm after each cycle. No signs of any inflammatory process were found by monitoring C-reactive protein. We did not detect significant changes in red blood cells, hemoglobin, and platelet levels or coagulation parameters. We found a significant elevation of uric acid, with normalization after finishing each treatment cycle. A significant decrease of the mean value activity of aspartate transaminase (AST) and alanine transaminase (ALT) of the G-CSF treatment was noted. After each five days of therapy, the level of cholesterol was significantly lowered. Also, glucose concentration significantly decreased after the fourth cycle.

Conclusions

G-SCF decreased the aminotransferases activity, cholesterol level, and glucose level in patients with DMD, which may be important for patients with DMD and metabolic syndrome.

Injectable basic fibroblast growth factor-loaded alginate/hyaluronic acid hydrogel for rejuvenation of geriatric larynx

Increase in the geriatric population has led to an increase in the number of elderly patients with laryngeal atrophy and dysfunction. Symptoms of voice change, dysphagia, and aspiration pneumonia negatively influence patient's health status, quality of life, and life span. Injection laryngoplasty used to treat laryngeal dysfunctions does not recover intrinsic functions of the larynx. Thus, we fabricated an injectable basic fibroblast growth factor (bFGF)-loaded alginate (ALG)/hyaluronic acid (HA) hydrogel for inducing rejuvenation of geriatric laryngeal muscles. Optimal in situ-forming bFGF-loaded ALG/HA hydrogel for injection laryngoplasty was prepared and the release profile of bFGF was analyzed. For in vivo analysis, the bFGF-loaded ALG/HA hydrogel was injected into the laryngeal muscles of 18-month-old Sprague-Dawley rats. The rejuvenation efficacy of bFGF-loaded ALG/HA hydrogel in geriatric laryngeal muscle tissues 4- and 12-weeks post-injection was evaluated by quantitative polymerase chain reaction (qPCR), histology, immune-fluorescence staining and functionality analysis. The bFGF-loaded ALG/HA hydrogel induced an increase in the expression of myogenic regulatory factor-related genes, hypertrophy of muscle fiber, proliferation of muscle satellite cells, and angiogenesis and decreased interstitial fibrosis. Administration of the bFGF-loaded ALG/HA hydrogel caused successful glottal gap closure. Thus, the bFGF-loaded ALG/HA hydrogel could be a promising candidate for laryngoplasty aimed at rejuvenating geriatric larynx. STATEMENT OF SIGNIFICANCE: In this manuscript, optimal in situ-forming bFGF-loaded ALG/HA hydrogel for injection laryngoplasty was prepared and the release profile of bFGF was analyzed. Herein, we introduced the materials and methods of injection laryngoplasty for geriatric rat experiment. In addition, we studied effects of bFGF-loaded ALG/HA hydrogel on the therapeutic rejuvenation of geriatric rat larynx. The bFGF-loaded ALG/HA hydrogel induced an increase in the expression of myogenic regulatory factor-related genes, hypertrophy of muscle fiber, proliferation of muscle satellite cells, and angiogenesis and decreased interstitial fibrosis. Furthermore, our functional analysis through the high-speed camera setup demonstrated that the administration of the bFGF-loaded ALG/HA hydrogel induced successful glottal gap closure. Thus, the bFGF-loaded ALG/HA hydrogel could be a promising candidate for injection laryngoplasty with therapeutic effects.

Targeting angiogenesis in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) represents one of the most devastating types of muscular dystrophies which affect boys already at early childhood. Despite the fact that the primary cause of the disease, namely the lack of functional dystrophin is known already for more than 30 years, DMD still remains an incurable disease. Thus, an enormous effort has been made during recent years to reveal novel mechanisms that could provide therapeutic targets for DMD, especially because glucocorticoids treatment acts mostly symptomatic and exerts many side effects, whereas the effectiveness of genetic approaches aiming at the restoration of functional dystrophin is under the constant debate. Taking into account that dystrophin expression is not restricted to muscle cells, but is present also in, e.g., endothelial cells, alterations in angiogenesis process have been proposed to have a significant impact on DMD progression. Indeed, already before the discovery of dystrophin, several abnormalities in blood vessels structure and function have been revealed, suggesting that targeting angiogenesis could be beneficial in DMD. In this review, we will summarize current knowledge about the angiogenesis status both in animal models of DMD as well as in DMD patients, focusing on different organs as well as age- and sex-dependent effects. Moreover, we will critically discuss some approaches such as modulation of vascular endothelial growth factor or nitric oxide related pathways, to enhance angiogenesis and attenuate the dystrophic phenotype. Additionally, we will suggest the potential role of other mediators, such as heme oxygenase-1 or statins in those processes.

Supplementation with a selective amino acid formula ameliorates muscular dystrophy in mdx mice

Duchenne muscular dystrophy (DMD) is one of the most common and severe forms of muscular dystrophy. Oxidative myofibre content, muscle vasculature architecture and exercise tolerance are impaired in DMD. Several studies have demonstrated that nutrient supplements ameliorate dystrophic features, thereby enhancing muscle performance. Here, we report that dietary supplementation with a specific branched-chain amino acid-enriched mixture (BCAAem) increased the abundance of oxidative muscle fibres associated with increased muscle endurance in dystrophic mdx mice. Amelioration of the fatigue index in BCAAem-treated mdx mice was caused by a cascade of events in the muscle tissue, which were promoted by endothelial nitric oxide synthase (eNOS) activation and vascular endothelial growth factor (VEGF) expression. VEGF induction led to recruitment of bone marrow (BM)-derived endothelial progenitors (EPs), which increased the capillary density of dystrophic skeletal muscle. Functionally, BCAAem mitigated the dystrophic phenotype of mdx mice without inducing dystrophin protein expression or replacing the dystrophin-associated glycoprotein (DAG) complex in the membrane, which is typically lost in DMD. BCAAem supplementation could be an effective adjuvant strategy in DMD treatment.

COMP-Angiopoietin-1 accelerates muscle regeneration through N-cadherin activation

Angiopoietin-1 modulates vascular stability via Tie2 on endothelial cells. In our previous study, we also showed it acts as an inhibitor of cardiomyocyte death. However, it remains poorly understood how Ang1 regulates myogenesis during muscle regeneration. Here we found that COMP-Ang1 (cAng1) enhances muscle regeneration through N-cadherin activation. Muscle fiber regeneration after limb muscle damage by ischemic injury was enhanced with cAng1 treatment. Mechanistically cAng1 directly bound to N-cadherin on the myoblast surface in a Ca²⁺ dependent manner. The interaction enhanced N-cadherin activation via N-cadherin/p120-catenin complex formation, which in turn activated p38MAPK (but not AKT or ERK) and myogenin expression (but not myoD) as well as increasing myogenin⁺ cells in/ex vivo. After transplantation of GFP-expressing myoblasts (GFP-MB), we showed an increased generation of GFP⁺ myotubes with adenovirus cAng1 (Adv-cAng1) injection. Adv-cAng1, however, could not stimulate myotube formation in N-cadherin-depleted GFP-MB. Taken together, this study uncovers the mechanism of how cAng1 promotes myoblast differentiation and muscle regeneration through the N-cadherin/p120-catenin/p38MAPK/myogenin axis.

Decellularized Diaphragmatic Muscle Drives a Constructive Angiogenic Response In Vivo

Skeletal muscle tissue engineering (TE) aims to efficiently repair large congenital and acquired defects. Biological acellular scaffolds are considered a good tool for TE, as decellularization allows structural preservation of tissue extracellular matrix (ECM) and conservation of its unique cytokine reservoir and the ability to support angiogenesis, cell viability, and proliferation. This represents a major advantage compared to synthetic scaffolds, which can acquire these features only after modification and show limited biocompatibility. In this work, we describe the ability of a skeletal muscle acellular scaffold to promote vascularization both ex vivo and in vivo. Specifically, chicken chorioallantoic membrane assay and protein array confirmed the presence of pro-angiogenic molecules in the decellularized tissue such as HGF, VEGF, and SDF-1α. The acellular muscle was implanted in BL6/J mice both subcutaneously and ortotopically. In the first condition, the ECM-derived scaffold appeared vascularized 7 days post-implantation. When the decellularized diaphragm was ortotopically applied, newly formed blood vessels containing CD31⁺, αSMA⁺, and vWF⁺ cells were visible inside the scaffold. Systemic injection of Evans Blue proved function and perfusion of the new vessels, underlying a tissue-regenerative activation. On the contrary, the implantation of a synthetic matrix made of polytetrafluoroethylene used as control was only surrounded by vWF⁺ cells, with no cell migration inside the scaffold and clear foreign body reaction (giant cells were visible). The molecular profile and the analysis of macrophages confirmed the tendency of the synthetic scaffold to enhance inflammation instead of regeneration. In conclusion, we identified the angiogenic potential of a skeletal muscle-derived acellular scaffold and the pro-regenerative environment activated in vivo, showing clear evidence that the decellularized diaphragm is a suitable candidate for skeletal muscle tissue engineering and regeneration.

Increased plasma lipid levels exacerbate muscle pathology in the mdx mouse model of Duchenne muscular dystrophy

Background

Duchenne muscular dystrophy (DMD) is caused by loss of dystrophin expression and leads to severe ambulatory and cardiac function decline. However, the dystrophin-deficient mdx murine model of DMD only develops a very mild form of the disease. Our group and others have shown vascular abnormalities in animal models of MD, a likely consequence of the fact that blood vessels express the same dystrophin-associated glycoprotein complex (DGC) proteins as skeletal muscles.

Methods

To test the blood vessel contribution to muscle damage in DMD, mdx^4cv mice were given elevated lipid levels via apolipoprotein E (ApoE) gene knockout combined with normal chow or lipid-rich Western diets. Ambulatory function and heart function (via echocardiogram) were assessed at 4 and 7 months of age. After sacrifice, muscle histology and aortic staining were used to assess muscle pathology and atherosclerosis development, respectively. Plasma levels of total cholesterol, high-density lipoprotein (HDL), triglycerides, and creatine kinase (CK) were also measured.

Results

Although there was an increase in left ventricular heart volume in mdx-ApoE mice compared to that in mdx mice, parameters of heart function were not affected. Compared with wild-type and ApoE-null, only mdx-ApoE KO mice showed significant ambulatory dysfunction. Despite no significant difference in plasma CK, histological analyses revealed that elevated plasma lipids in chow- and Western diet-fed mdx-ApoE mice was associated with severe exacerbation of muscle pathology compared to mdx mice: significant increase in myofiber damage and fibrofatty replacement in the gastrocnemius and triceps brachii muscles, more reminiscent of human DMD pathology. Finally, although both ApoE and mdx-ApoE groups displayed increased plasma lipids, mdx-ApoE exhibited atherosclerotic plaque deposition equal to or less than that of ApoE mice.

Conclusions

Since others have shown that lipid abnormalities correlate with DMD severity, our data suggest that plasma lipids could be primary contributors to human DMD severity and that the notoriously mild phenotype of mdx mice might be attributable in part to their endogenously low plasma lipid profiles. Hence, DMD patients may benefit from lipid-lowering and vascular-targeted therapies.

Electronic supplementary material

The online version of this article (10.1186/s13395-017-0135-9) contains supplementary material, which is available to authorized users.

ANG1 treatment reduces muscle pathology and prevents a decline in perfusion in DMD mice

Vascular endothelial growth factor (VEGF) and other pro-angiogenic growth factors have been investigated to enhance muscle tissue perfusion and repair in Duchenne muscular dystrophy (DMD). Current understanding is limited by a lack of functional data following in vivo delivery of these growth factors. We previously used dynamic contrast-enhanced computed tomography to monitor disease progression in murine models of DMD, but no study to date has utilized this imaging technique to assess vascular therapy in a preclinical model of DMD. In the current study, we locally delivered VEGF and ANG1 alone or in combination to dystrophic hind limb skeletal muscle. Using functional imaging, we found the combination treatment as well as ANG1 alone prevented decline in muscle perfusion whereas VEGF alone had no effect compared to controls. These findings were validated histologically as demonstrated by increased alpha-smooth muscle actin-positive vessels in muscles that received either VEGF+ANG1 or ANG1 alone compared to the sham group. We further show that ANG1 alone slows progression of fibrosis compared to either sham or VEGF treatment. The findings from this study shed new light on the functional effects of vascular therapy and suggest that ANG1 alone may be a candidate therapy in the treatment of DMD.

Skeletal Muscle Microvasculature: A Highly Dynamic Lifeline

Skeletal muscle is highly irrigated by blood vessels. Beyond oxygen and nutrient supply, new vessel functions have been identified. This review presents vessel microanatomy and functions at tissue, cellular, and molecular levels. Mechanisms of vessel plasticity are described during skeletal muscle development and acute regeneration, and in physiological and pathological contexts.

Role of Growth Factors in Modulation of the Microvasculature in Adult Skeletal Muscle

Post-natal skeletal muscle is a highly plastic tissue that has the capacity to regenerate rapidly following injury, and to undergo significant modification in tissue mass (i.e. atrophy/hypertrophy) in response to global metabolic changes. These processes are reliant largely on soluble factors that directly modulate muscle regeneration and mass. However, skeletal muscle function also depends on an adequate blood supply. Thus muscle regeneration and changes in muscle mass, particularly hypertrophy, also demand rapid changes in the microvasculature. Recent evidence clearly demonstrates a critical role for soluble growth factors in the tight regulation of angiogenic expansion of the muscle microvasculature. Furthermore, exogenous modulation of these factors has the capacity to impact directly on angiogenesis and thus, indirectly, on muscle regeneration, growth and performance. This chapter reviews recent developments in understanding the role of growth factors in modulating the skeletal muscle microvasculature, and the potential therapeutic applications of exogenous angiogenic and anti-angiogenic mediators in promoting effective growth and regeneration, and ameliorating certain diseases, of skeletal muscle.

Effect of Periodic Granulocyte Colony-Stimulating Factor Administration on Endothelial Progenitor Cells and Different Monocyte Subsets in Pediatric Patients with Muscular Dystrophies

Muscular dystrophies (MD) are heterogeneous group of diseases characterized by progressive muscle dysfunction. There is a large body of evidence indicating that angiogenesis is impaired in muscles of MD patients. Therefore, induction of dystrophic muscle revascularization should become a novel approach aimed at diminishing the extent of myocyte damage. Recently, we and others demonstrated that administration of granulocyte colony-stimulating factor (G-CSF) resulted in clinical improvement of patients with neuromuscular disorders. To date, however, the exact mechanisms underlying these beneficial effects of G-CSF have not been fully understood. Here we used flow cytometry to quantitate numbers of CD34+ cells, endothelial progenitor cells, and different monocyte subsets in peripheral blood of pediatric MD patients treated with repetitive courses of G-CSF administration. We showed that repetitive cycles of G-CSF administration induced efficient mobilization of above-mentioned cells including cells with proangiogenic potential. These findings contribute to better understanding the beneficial clinical effects of G-CSF in pediatric MD patients.

Stem cells isolated from human dental pulp and amniotic fluid improve skeletal muscle histopathology in mdx/SCID mice

INTRODUCTION

Duchenne muscular dystrophy (DMD), caused by a lack of the functional structural protein dystrophin, leads to severe muscle degeneration where the patients are typically wheelchair-bound and die in their mid-twenties from cardiac or respiratory failure or both. The aim of this study was to investigate the potential of human dental pulp stem cells (hDPSCs) and human amniotic fluid stem cells (hAFSCs) to differentiate toward a skeletal myogenic lineage using several different protocols in order to determine the optimal conditions for achieving myogenic commitment and to subsequently evaluate their contribution in the improvement of the pathological features associated with dystrophic skeletal muscle when intramuscularly injected into mdx/SCID mice, an immune-compromised animal model of DMD.

METHODS

Human DPSCs and AFSCs were differentiated toward myogenic lineage in vitro through the direct co-culture with a myogenic cell line (C2C12 cells) and through a preliminary demethylation treatment with 5-Aza-2'-deoxycytidine (5-Aza), respectively. The commitment and differentiation of both hDPSCs and hAFSCs were evaluated by immunofluorescence and Western blot analysis. Subsequently, hDPSCs and hAFSCs, preliminarily demethylated and pre-differentiated toward a myogenic lineage for 2 weeks, were injected into the dystrophic gastrocnemius muscles of mdx/SCID mice. After 1, 2, and 4 weeks, the gastrocnemius muscles were taken for immunofluorescence and histological analyses.

RESULTS

Both populations of cells engrafted within the host muscle of mdx/SCID mice and through a paracrine effect promoted angiogenesis and reduced fibrosis, which eventually led to an improvement of the histopathology of the dystrophic muscle.

CONCLUSION

This study shows that hAFSCs and hDPSCs represent potential sources of stem cells for translational strategies to improve the histopathology and potentially alleviate the muscle weakness in patients with DMD.

VEGF induces stress fiber formation in fibroblasts isolated from dystrophic muscle

Treatment with vascular endothelial growth factor (VEGF) to reduce ischemia and enhance both endogenous muscle repair and regenerative cell therapy in Duchenne muscular dystrophy (DMD) has been widely proposed in recent years. However, the interaction between angiogenesis and fibrosis, a hallmark feature of DMD, remains unclear. To date, it has not been determined whether VEGF exerts a pro-fibrotic effect on DMD-derived fibroblasts, which may contribute to further disease progression. Thus, the purpose of this study was to investigate the effect of exogenous VEGF on fibroblast cultures established from a murine model of DMD. Primary fibroblast cultures were established from gastrocnemius and diaphragm muscles of 10 week-old mdx/utrn+/- mice. Quantitative polymerase chain reaction (qPCR) was employed to assess changes in transcript expression of alpha-smooth muscle actin (Acta2), type-1 collagen (Col1a1), connective tissue growth factor (Ctgf/ccn2) and fibronectin (Fn1). Immunofluorescence and Western blot analysis was further employed to visualize changes in protein expression of alpha-smooth muscle actin (α-SMA), CTGF/CCN2 and fibronectin. mRNA levels of Col1a1, Ctgf/ccn2, and FN did not increase following treatment with VEGF in fibroblasts derived from either diaphragm or gastrocnemius muscles. Acta2 expression increased significantly in diaphragm-derived fibroblasts following treatment with VEGF. Morphological assessment revealed increased stress fiber formation in VEGF-treated fibroblasts compared to the untreated control fibroblasts. The findings from this study suggest that further investigation into the effect of VEGF on fibroblast function is required prior to the utilization of the growth factor as a treatment for DMD.

Treatable renal failure found in non-ambulatory Duchenne muscular dystrophy patients

Duchenne muscular dystrophy (DMD) is a progressive muscular disorder in which respiratory and heart failures are the main causes of death. Intensive intervention in respiratory and cardiac function has dramatically improved the prognosis; however, dysfunction in other multiple organs may emerge in the later stages of the disease. We report the case of four non-ambulatory DMD patients who presented with renal failure. Common findings included decreased fluid intake, use of diuretics, and presence of chronic heart failure. The levels of serum cystatin C (CysC), a marker of kidney function unaffected by reduced muscle mass, were elevated in all four patients. In two patients, renal failure improved by increasing fluid intake, and discontinuing or reducing the dose of diuretics. The findings suggest that non-ambulatory DMD patients are at a risk of reduced kidney perfusion, which potentially leads to prerenal failure. Therefore, in DMD patients, dehydration signs and CysC levels should be monitored.

Structural and Functional Alterations of Skeletal Muscle Microvasculature in Dystrophin-Deficient mdx Mice

Duchenne muscular dystrophy (DMD) is a progressive neuromuscular disease, caused by an absence of dystrophin, inevitably leading to death. Although muscle lesions are well characterized, blood vessel alterations that may have a major impact on muscle regeneration remain poorly understood. Our aim was to elucidate alterations of the vascular network organization, taking advantage of Flk1(GFP/+) crossed with mdx mice (model for human DMD where all blood vessels express green fluorescent protein) and functional repercussions using in vivo nuclear magnetic resonance, combining arterial spin-labeling imaging of perfusion, and (31)P-spectroscopy of phosphocreatine kinetics. For the first time, our study focused on old (12-month-old) mdx mice, displaying marked chronic muscle lesions, similar to the lesions observed in human DMD, in comparison to young-adult (3-month-old) mdx mice displaying only mild muscle lesions with no fibrosis. By using an original approach combining a specific animal model, state-of-the-art histology/morphometry techniques, and functional nuclear magnetic resonance, we demonstrated that the microvascular system is almost normal in young-adult in contrast to old mdx mice, displaying marked microvessel alterations, and the functional repercussions on muscle perfusion and bioenergetics after a hypoxic stress vary depending on stage of pathology. This original approach clarifies disease evolution and paves the way for setting up new diagnostic markers or therapeutic strategies.

Nicotinic receptor-dependent and -independent effects of galantamine, an acetylcholinesterase inhibitor, on the non-neuronal acetylcholine system in C2C12 cells

We previously reported that satellite cells possess the ability to produce angiogenic factors, including fibroblast growth factor (FGF)-2 and vascular endothelial growth factor (VEGF) in vivo. However, whether C2C12 cells possess a non-neuronal cholinergic system (NNCS) or non-neuronal ACh (NNA) remains to be studied; therefore, we investigated the system using C2C12 cells and its regulatory mechanisms. C2C12 cells synthesized ACh, the level of which was comparable with that of cardiomyocytes, and the synthesis was augmented by the acetylcholinesterase inhibitor galantamine. The ChAT promoter activity was upregulated by nicotine or galantamine, partly through nicotinic receptors for both agents as well as through a non-nicotinic receptor pathway for galantamine. Further, VEGF secretion by C2C12 cells was also increased by nicotine or galantamine through nicotinic receptors as well as partly through non-nicotinic pathways in the case of galantamine. These results suggest that C2C12 cells are equipped with NNCS or NNA, which is positively regulated through nicotinic or non-nicotinic pathways, particularly in the case of galantamine. These results provide a novel concept that myogenic cells expressing NNA can be a therapeutic target for regulating angiogenic factor synthesis.

MicroRNAs modulated by local mIGF-1 expression in mdx dystrophic mice

Duchenne muscular dystrophy (DMD) is a X-linked genetic disease in which the absence of dystrophin leads to progressive lethal skeletal muscle degeneration. It has been demonstrated that among genes which are important for proper muscle development and function, micro-RNAs (miRNAs) play a crucial role. Moreover, altered levels of miRNAs were found in several muscular disorders, including DMD. A specific group of miRNAs, whose expression depends on dystrophin levels and whose deregulation explains several DMD pathogenetic traits, has been identified. Here, we addressed whether the anabolic activity of mIGF-1 on dystrophic muscle is associated with modulation of microRNAs expression. We demonstrated that some microRNAs are strictly linked to the dystrophin expression and are not modulated by mIGF-1 expression. In contrast, local expression of mIGF-1 promotes the modulation of other microRNAs, such as miR-206 and miR-24, along with the modulation of muscle specific genes, which are associated with maturation of regenerating fibers and with the stabilization of the differentiated muscle phenotype. These data suggest that mIGF-1, modifying the expression of some of the active players of muscle homeostasis, is able, even in absence of dystrophin expression, to activate circuitries that confer robustness to dystrophic muscle.

Cell Therapy for Stress Urinary Incontinence

Urinary incontinence (UI) is the involuntary loss of urine and is a common condition in middle-aged and elderly women and men. Stress urinary incontinence (SUI) is caused by leakage of urine when coughing, sneezing, laughing, lifting, and exercise, even standing leads to increased intra-abdominal pressure. Other types of UI also exist such as urge incontinence (also called overactive bladder), which is a strong and unexpected sudden urge to urinate, mixed forms of UI that result in symptoms of both urge and stress incontinence, and functional incontinence caused by reduced mobility, cognitive impairment, or neuromuscular limitations that impair mobility or dexterity. However, for many SUI patients, there is significant loss of urethral sphincter muscle due to degeneration of tissue, the strain and trauma of pregnancy and childbirth, or injury acquired during surgery. Hence, for individuals with SUI, a cell-based therapeutic approach to regenerate the sphincter muscle offers the advantage of treating the cause rather than the symptoms. We discuss current clinically relevant cell therapy approaches for regeneration of the external urethral sphincter (striated muscle), internal urethral sphincter (smooth muscle), the neuromuscular synapse, and blood supply. The use of mesenchymal stromal/stem cells is a major step in the right direction, but they may not be enough for regeneration of all components of the urethral sphincter. Inclusion of other cell types or biomaterials may also be necessary to enhance integration and survival of the transplanted cells.

Pregnancy-induced amelioration of muscular dystrophy phenotype in mdx mice via muscle membrane stabilization effect of glucocorticoid

Duchenne muscular dystrophy (DMD), the most common and severe type of dystrophinopathy, is an X-linked recessive genetic disease caused by the absence of dystrophin, which leads to fragility and vulnerability of the sarcolemma to mechanical stretching with increased membrane permeability. Currently, glucocorticoids such as prednisolone are the only medication available for DMD. However, molecular pathways responsible for this effect are still unclear. In addition, it remains unclear whether sex-related factors, including pregnancy and the postpartum period, affect the phenotype of dystrophinopathy. Here, we report the amelioration of muscle membrane permeability in the diaphragm muscle of pregnant and postpartum, but not in nulliparous, mdx mice, an animal model for DMD, during the physiological surge of corticosterone, the most abundant glucocorticoid in rodents. Cultures of single muscle fibers and myotubes isolated from mdx mouse diaphragm demonstrate resistance to hypo-osmotic shock when treated with corticosterone but not with estradiol or progesterone. This corticosterone-mediated resistance was diminished by an antagonist of corticosterone, indicating that the glucocorticoid-glucocorticoid receptor axis plays a role in this membrane stabilization effect on muscle. Moreover, subcutaneous injection of corticosterone into mdx mice showed decreased membrane permeability. This is the first report to demonstrate that pregnancy-related resistance to muscle fiber damage in mdx mice due to the membrane stabilization effect of corticosterone. We also propose that this membrane stabilization effect is exerted through annexin A1 up-regulation as the molecular mechanisms of glucocorticoid effects on DMD muscle. Furthermore, single muscle fiber culture studies provide a sensitive chemical screening platform for muscular dystrophies.