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Aim: The purpose of this study is to evaluate the safety and pharmacokinetics of the novel morpholino oligomer NS‐089/NCNP‐02 which can induce exon 44 skipping, in patients with DMD. Additionally, we aimed to identify markers predictive of therapeutic efficacy and determine the optimal dosing for future studies. Methods: This is an open‐label, dose‐escalation, two‐center phase I/II trial in ambulant patients with DMD, presence of an out‐of‐frame deletion, and a mutation amenable to exon 44 skipping. Part 1 is a stepwise dose‐finding stage (4 weeks) during which NS‐089/NCNP‐02 will be administered intravenously at four dose levels once weekly (1.62, 10, 40, and 80 mg/kg); Part 2 is a 24‐week evaluation period based on the dosages determined during Part 1. The primary (safety) endpoints are the results of physical examinations, vital signs, 12‐lead electrocardiogram and echocardiography tests, and adverse event reporting. Secondary endpoints include expression of dystrophin protein, motor function assessment, exon 44 skipping efficiency, plasma and urinary NS‐089/NCNP‐02 concentrations, and changes in blood creatine kinase levels. Discussion: Exon‐skipping therapy using ASOs shows promise in selected patients, and this first‐in‐human study is expected to provide critical information for subsequent clinical development of NS‐089/NCNP‐02. [ABSTRACT FROM AUTHOR]

Duchenne muscular dystrophy (DMD) is caused by mutations in the gene encoding dystrophin, which results in dysfunctional signaling pathways within muscle. Previously, we identified microRNA-486 (miR-486) as a muscle-enriched microRNA that is markedly reduced in the muscles of dystrophin-deficient mice ([Dmd.sup.mdx5Cv] mice) and in DMD patient muscles. Here, we determined that muscle-specific transgenic overexpression of miR-486 in muscle of [Dmd.sup.mdx5Cv] mice results in reduced serum creatine kinase levels, improved sarcolemmal integrity, fewer centralized myonuclei, increased myofiber size, and improved muscle physiology and performance. Additionally, we identified dedicator of cytokinesis 3 (DOCK3) as a miR-486 target in skeletal muscle and determined that DOCK3 expression is induced in dystrophic muscles. DOCK3 overexpression in human myotubes modulated PTEN/AKT signaling, which regulates muscle hypertrophy and growth, and induced apoptosis. Furthermore, several components of the PTEN/AKT pathway were markedly modulated by miR-486 in dystrophin-deficient muscle. Skeletal muscle-specific miR-486 overexpression in [Dmd.sup.mdx5Cv] animals decreased levels of DOCK3, reduced PTEN expression, and subsequently increased levels of phosphorylated AKT, which resulted in an overall beneficial effect. Together, these studies demonstrate that stable overexpression of miR-486 ameliorates the disease progression of dystrophin-deficient skeletal muscle., Introduction Mammalian skeletal muscle is a dynamic organ capable of repairing itself following injury or atrophy arising from prolonged disuse. The skeletal muscle-regenerative process is a well-regulated process involving a [...]

Forkhead box O (Foxo) transcription factors induce muscle atrophy by upregulating the muscle-specific E3 ubiquitin ligases MuRF-1 and atrogin- 1/MAFbx, but other than Akt, the upstream regulators of Foxos during [...]

Abstract Background Duchenne muscular dystrophy (DMD) is an X-linked myopathy resulting from the production of a nonfunctional dystrophin protein. MicroRNA (miRNA) are small 21- to 24-nucleotide RNA that can regulate both individual genes and entire cell signaling pathways. Previously, we identified several mRNA, both muscle-enriched and inflammation-induced, that are dysregulated in the skeletal muscles of DMD patients. One particularly muscle-enriched miRNA, miR-486, is significantly downregulated in dystrophin-deficient mouse and human skeletal muscles. miR-486 is embedded within the ANKYRIN1(ANK1) gene locus, which is transcribed as either a long (erythroid-enriched) or a short (heart muscle- and skeletal muscle-enriched) isoform, depending on the cell and tissue types. Results Inhibition of miR-486 in normal muscle myoblasts results in inhibited migration and failure to repair a wound in primary myoblast cell cultures. Conversely, overexpression of miR-486 in primary myoblast cell cultures results in increased proliferation with no changes in cellular apoptosis. Using bioinformatics and miRNA reporter assays, we have identified platelet-derived growth factor receptor β, along with several other downstream targets of the phosphatase and tensin homolog deleted on chromosome 10/AKT (PTEN/AKT) pathway, as being modulated by miR-486. The generation of muscle-specific transgenic mice that overexpress miR-486 revealed that miR-486 alters the cell cycle kinetics of regenerated myofibers in vivo, as these mice had impaired muscle regeneration. Conclusions These studies demonstrate a link for miR-486 as a regulator of the PTEN/AKT pathway in dystrophin-deficient muscle and an important factor in the regulation of DMD muscle pathology.

Satellite cells are myogenic stem cells responsible for the postnatal regeneration of skeletal muscle. Here we report the successful in vitro induction of Pax7-positive satellite-like cells from mouse embryonic stem (mES) cells. Embryoid bodies were generated from mES cells and cultured on Matrigel-coated dishes with Dulbecco's modified Eagle medium containing fetal bovine serum and horse serum. Pax7o-positive satellite-like cells were enriched by fluorescence-activated cell sorting using a novel anti-satellite cell antibody, SM/C-2.6. SM/C-2.6-positive cells efficiently differentiate into skeletal muscle fibers both in vitro and in vivo. Furthermore, the cells demonstrate satellite cell characteristics such as extensive self-renewal capacity in subsequent muscle injury model, long-term engraftment up to 24 wk, and the ability to be secondarily transplanted with remarkably high engraftment efficiency compared to myoblast transplantation. This is the first report of transplantable, functional satellite-like cells derived from mES cells and will provide a foundation for new therapies for degenerative muscle disorders. [ABSTRACT FROM AUTHOR]

Muscular dystrophies (MDs) are a group of heterogeneous genetic disorders caused by mutations in the genes encoding the structural components of myofibres. The current state-of-the-art treatment is oligonucleotide-based gene therapy that restores disease-related protein. However, this therapeutic approach has limited efficacy and is unlikely to be curative. While the number of studies focused on cell transplantation therapy has increased in the recent years, this approach remains challenging due to multiple issues related to the efficacy of engrafted cells, source of myogenic cells, and systemic injections. Technical innovation has contributed to overcoming cell source challenges, and in recent studies, a combination of muscle resident stem cells and gene editing has shown promise as a novel approach. Furthermore, improvement of the muscular environment both in cultured donor cells and in recipient MD muscles may potentially facilitate cell engraftment. Artificial skeletal muscle generated by myogenic cells and muscle resident cells is an alternate approach that may enable the replacement of damaged tissues. Here, we review the current status of myogenic stem cell transplantation therapy, describe recent advances, and discuss the remaining obstacles that exist in the search for a cure for MD patients. [ABSTRACT FROM AUTHOR]

Clenbuterol (CLE: 4-amino-α(t-butyl-amino)methyl-3,5-diehlorobenzyl alcohol) is well known as the potent β2-adrenergic agonist and nonsteroidal anabolic drug, thus generally used for the sports doping and asthma therapy. However, the administration effects of CLE on immune-responsive systems have not been elucidated. Therefore, the administration effects of CLE on the number of white blood cells were studied in rats. Male adult rats were divided into the control and CLE-administered groups to compare the number of total white blood cells, neutrophil, monocyte, lymphocytes, eosinophil, and basophil. The administration (dose = 1.0 mg · kg-1 body weight · day-1) of CLE was maintained for 30 days. The administration of CLE did not change the number of total white blood cells during the experimental period. However, the administration of CLE decreased drastically the number of lymphoeytes and eosinophil, while increased significantly the number of monocyte and neutrophil during the experimental period. There was no significant change in the number of basophil during the experimental period. These results suggest that the administration of CLE induces drastic redistribution of circulating white blood cells without changing the number of total white blood cells, and these redistribution responses of circulating white blood cells during the administration of CLE are sustained for at least 30 days. [ABSTRACT FROM AUTHOR]

Antisense oligonucleotide (ASO)-based exon skipping therapy is thought to be promising for Duchenne muscular dystrophy (DMD). For the screening or assessing patient eligibility before administering ASO to patients, in vitro testing using myoblasts derived from each DMD patient is considered crucial. We previously reported state-of-the-art technology to obtain patient primary myoblasts from MYOD1-induced urine-derived cells (UDCs) as a model of DMD. We hypothesize that the myoblasts may potentially reflect specific pathological phenotypes, leading to a path for precision medicine in DMD patients. Here, we describe a detailed protocol for both acquiring MYOD1-induced myoblasts from UDCs and evaluating the correction of DMD mRNA and protein levels after exon-skipping in the cells., (© 2023. The Author(s), under exclusive license to Springer Science+Business Media, LLC, part of Springer Nature.)

Skeletal muscle can adjust to changes in physiological and pathological environments by regenerating using myogenic progenitor cells or adapting muscle fiber sizes and types, metabolism, and contraction ability. To study these changes, muscle samples should be appropriately prepared. Therefore, reliable techniques to accurately analyze and evaluate skeletal muscle phenotypes are required. However, although technical approaches to genetically investigating skeletal muscle are improving, the fundamental strategies for capturing muscle pathology are the same over the decades. Hematoxylin and eosin (H&E) staining or antibodies are the simplest and standard methodologies for assessing skeletal muscle phenotypes. In this chapter, we describe fundamental techniques and protocols for inducing skeletal muscle regeneration by using chemicals and cell transplantation, in addition to methods of preparing and evaluating skeletal muscle samples., (© 2023. Springer Science+Business Media, LLC, part of Springer Nature.)

Caveolins, encoded by the Cav gene family, are the main components of caveolae. Caveolin-3 ( Cav3 ) is specifically expressed in muscle cells. Mutations in Cav3 are responsible for a group of muscle diseases called caveolinopathies, and Cav3 deficiency is associated with sarcolemmal membrane alterations, disorganization of T-tubules, and disruption of specific cell-signaling pathways. However, Cav3 overexpression increases the number of sarcolemmal caveolae and muscular dystrophy-like regenerating muscle fibers with central nuclei, suggesting that the alteration of Cav3 expression levels or localization influences muscle cell functions. Here, we used mouse C2C12 myoblasts in which Cav3 expression was suppressed with short hairpin RNA and found that Cav3 suppression impaired myotube differentiation without affecting the expression of MyoD and Myog . We also observed an increase of intracellular Ca 2+ levels, total calpain activity, and Ca 2+ -dependent calmodulin kinase II (CaMKII) levels in Cav3 -depleted myoblasts. Importantly, those phenotypes due to Cav3 suppression were caused by the ryanodine receptor activation. Furthermore, pharmacological inhibition of CaMKII rescued the impairment of myoblast differentiation due to Cav3 knockdown. Our results suggest that Cav3 regulates intracellular Ca 2+ concentrations by modulating ryanodine receptor activity in muscle cells and that CaMKII suppression in muscle could be a novel therapy for caveolinopathies.