Stem cells and plasticity of skeletal muscle cell differentiation: potential application to cell therapy for degenerative muscular diseases

Regulatory role of RNA N6-methyladenosine modifications during skeletal muscle development

Functional cells in embryonic myogenesis and postnatal muscle development undergo multiple stages of proliferation and differentiation, which are strict procedural regulation processes. N⁶-methyladenosine (m⁶A) is the most abundant RNA modification that regulates gene expression in specific cell types in eukaryotes and regulates various biological activities, such as RNA processing and metabolism. Recent studies have shown that m⁶A modification-mediated transcriptional and post-transcriptional regulation plays an essential role in myogenesis. This review outlines embryonic and postnatal myogenic differentiation and summarizes the important roles played by functional cells in each developmental period. Furthermore, the key roles of m⁶A modifications and their regulators in myogenesis were highlighted, and the synergistic regulation of m⁶A modifications with myogenic transcription factors was emphasized to characterize the cascade of transcriptional and post-transcriptional regulation during myogenesis. This review also discusses the crosstalk between m⁶A modifications and non-coding RNAs, proposing a novel mechanism for post-transcriptional regulation during skeletal muscle development. In summary, the transcriptional and post-transcriptional regulatory mechanisms mediated by m⁶A and their regulators may help develop new strategies to maintain muscle homeostasis, which are expected to become targets for animal muscle-specific trait breeding and treatment of muscle metabolic diseases.

MSX1 gene polymorphisms and non-syndromic cleft lip with or without palate (NSCL/P): A meta-analysis

OBJECTIVE

Non-syndromic cleft lip, with or without cleft palate (NSCL/P), is a common craniofacial birth defect, the risk of which is influenced from multiple genetic loci. Association study outcomes between single nucleotide polymorphisms (SNPs) near the muscle segment homeobox gene 1 (MSX1) and NSCL/P have been inconsistent. This compels a meta-analysis to obtain more precise estimates.

METHODS

From 15 publications, we examined 12 SNPs under six groups (SG), based on linkage disequilibrium. Pooled odds ratios and 95% confidence intervals were calculated under the standard genetic models. The pooled effects were subjected to subgroup, outlier, sensitivity, and funnel plot (publication bias) analyses.

RESULTS

Three of the six SGs showed significant associations. SG1 and SG4 effects indicated reduced risks. SG1 outcomes were attributed to outlier treatment, which the Asian outcomes validated. In contrast, increased risks were observed in SG3. All these significant outcomes were deemed robust by sensitivity analysis with no evidence of publication bias.

CONCLUSIONS

Our study shows eight MSX1 SNPs associated with risk of NSCL/P. SG1 and SG4 carriers are protected (up to 23%), but SG3 carriers are 1.3-fold susceptible. Outlier treatment unmasked the significant associations in SG1. Non-heterogeneity and robustness helped elevate the level of evidence in our significant findings.

Exosomes secreted by urine-derived stem cells improve stress urinary incontinence by promoting repair of pubococcygeus muscle injury in rats

Background

Previous studies revealed that urine-derived stem cells (USCs) could promote myogenesis after the impairment of the sphincter muscles. However, the effects of exosomes secreted by USCs (USCs-Exo) were not elucidated. Exosomes are nanosized membrane vesicles secreted by the cells. They have been proved to be effective in protecting against tissue injury and therapeutic in tissue repair. USCs are ideal sources of exosomes because of the noninvasive obtaining method and self-renewal abilitiy. This study aimed to show the therapeutic effects of USCs-Exo on improving stress urinary incontinence (SUI).

Methods

Rat SUI models were established in this study using vaginal balloon inflation, and urodynamic and histological examination were carried out after exosome application. The proliferation and differentiation of muscle satellite cells (SCs) were evaluated using EdU, Cell Counting Kit 8, immunofluorescence staining, and Western blot analysis. mRNAs and proteins related to the activation of SCs were detected by reverse transcriptase quantitative polymerase chain reaction (RT-qPCR) and Western blot analysis.

Results

After exosome injection, the urodynamic parameters significantly improved and the injured muscle tissue recovered well. The activation, proliferation, and differentiation of SCs were promoted. The phosphorylation of extracellular-regulated protein kinases (ERK) was enhanced. When ERK was inhibited, the promoting effect of USCs-Exo treatment disappeared.

Conclusion

The findings of this study elucidated the functional roles of USCs-Exo in satellite cell ERK phosphorylation and identified a novel agent for skeletal muscle regeneration, providing a basis for further exploring a cell-free correction for SUI.

Electronic supplementary material

The online version of this article (10.1186/s13287-019-1182-4) contains supplementary material, which is available to authorized users.

Thyroid hormone signaling and deiodinase actions in muscle stem/progenitor cells

Thyroid hormone (TH) regulates such crucial biological functions as normal growth, development and metabolism of nearly all vertebrate tissues. In skeletal muscle, TH plays a critical role in regulating the function of satellite cells, the bona fide skeletal muscle stem cells. Deiodinases (D2 and D3) have been found to modulate the expression of various TH target genes in satellite cells. Regulation of the expression and activity of the deiodinases constitutes a cell-autonomous, pre-receptor mechanism that controls crucial steps during the various phases of myogenesis. Here, we review the roles of deiodinases in skeletal muscle stem cells, particularly in muscle homeostasis and upon regeneration. We focus on the role of T3 in stem cell functions and in commitment towards lineage progression. We also discuss how deiodinases might be therapeutically exploited to improve satellite-cell-mediated muscle repair in skeletal muscle disorders or injury.

Acetoacetate Accelerates Muscle Regeneration and Ameliorates Muscular Dystrophy in Mice

Acetoacetate (AA) is a ketone body and acts as a fuel to supply energy for cellular activity of various tissues. Here, we uncovered a novel function of AA in promoting muscle cell proliferation. Notably, the functional role of AA in regulating muscle cell function is further evidenced by its capability to accelerate muscle regeneration in normal mice, and it ameliorates muscular dystrophy in mdx mice. Mechanistically, our data from multiparameter analyses consistently support the notion that AA plays a non-metabolic role in regulating muscle cell function. Finally, we show that AA exerts its function through activation of the MEK1-ERK1/2-cyclin D1 pathway, revealing a novel mechanism in which AA serves as a signaling metabolite in mediating muscle cell function. Our findings highlight the profound functions of a small metabolite as signaling molecule in mammalian cells.

Molecular mechanisms of skeletal muscle development, regeneration, and osteogenic conversion

Both skeletal muscle and bone are of mesodermal origin and derived from somites during embryonic development. Somites differentiate into the dorsal dermomyotome and the ventral sclerotome, which give rise to skeletal muscle and bone, respectively. Extracellular signaling molecules, such as Wnt and Shh, secreted from the surrounding environment, determine the developmental fate of skeletal muscle. Dermomyotome cells are specified as trunk muscle progenitor cells by transcription factor networks involving Pax3. These progenitor cells delaminate and migrate to form the myotome, where they are determined as myoblasts that differentiate into myotubes or myofibers. The MyoD family of transcription factors plays pivotal roles in myogenic determination and differentiation. Adult skeletal muscle regenerates upon exercise, muscle injury, or degeneration. Satellite cells are muscle-resident stem cells and play essential roles in muscle growth and regeneration. Muscle regeneration recapitulates the process of muscle development in many aspects. In certain muscle diseases, ectopic calcification or heterotopic ossification, as well as fibrosis and adipogenesis, occurs in skeletal muscle. Muscle-resident mesenchymal progenitor cells, which may be derived from vascular endothelial cells, are responsible for the ectopic osteogenesis, fibrogenesis, and adipogenesis. The small GTPase M-Ras is likely to participate in the ectopic calcification and ossification, as well as in osteogenesis during development. This article is part of a Special Issue entitled "Muscle Bone Interactions".

Full-length dysferlin expression driven by engineered human dystrophic blood derived CD133+ stem cells

The protein dysferlin is abundantly expressed in skeletal and cardiac muscles, where its main function is membrane repair. Mutations in the dysferlin gene are involved in two autosomal recessive muscular dystrophies: Miyoshi myopathy and limb-girdle muscular dystrophy type 2B. Development of effective therapies remains a great challenge. Strategies to repair the dysferlin gene by skipping mutated exons, using antisense oligonucleotides (AONs), may be suitable only for a subset of mutations, while cell and gene therapy can be extended to all mutations. AON-treated blood-derived CD133+ stem cells isolated from patients with Miyoshi myopathy led to partial dysferlin reconstitution in vitro but failed to express dysferlin after intramuscular transplantation into scid/blAJ dysferlin null mice. We thus extended these experiments producing the full-length dysferlin mediated by a lentiviral vector in blood-derived CD133+ stem cells isolated from the same patients. Transplantation of engineered blood-derived CD133+ stem cells into scid/blAJ mice resulted in sufficient dysferlin expression to correct functional deficits in skeletal muscle membrane repair. Our data suggest for the first time that lentivirus-mediated delivery of full-length dysferlin in stem cells isolated from Miyoshi myopathy patients could represent an alternative therapeutic approach for treatment of dysferlinopathies.

Reawakening atlas: chemical approaches to repair or replace dysfunctional musculature

Muscle diseases are major health concerns. For example, ischemic heart disease is the third most common cause of death. Cell therapy is an attractive approach for treating muscle diseases, although this is hampered by the need to generate large numbers of functional muscle cells. Small molecules have become established as attractive tools for modulating cell behavior and, in this review, we discuss the recent, rapid research advances made in the development of small molecule methods to facilitate the production of functional cardiac, skeletal, and smooth muscle cells. We also describe how new developments in small molecule strategies for muscle disease aim to induce repair and remodelling of the damaged tissues in situ. Recent progress has been made in developing small molecule cocktails that induce skeletal muscle regeneration, and these are discussed in a broader context, because a similar phenomenon occurs in the early stages of salamander appendage regeneration. Although formidable technical hurdles still remain, these new advances in small molecule-based methodologies should provide hope that cell therapies for patients suffering from muscle disease can be developed in the near future.

Notch1-mediated signaling regulates proliferation of porcine satellite cells (PSCs)

Notch signaling is an evolutionarily conserved cell-cell communication mechanism involved in the regulation of cell proliferation, differentiation and fate decisions of mammalian cells. In the present study, we investigated the possible requirement for Notch signaling in the proliferation and differentiation of porcine satellite cells. We show that Notch1, 2 and 3 are expressed in cultured porcine satellite cells. Knock-down of NOTCH1, but not NOTCH2 and NOTCH3, decreases the proliferation of porcine satellite cells. In contrast, enhancement of NOTCH1 expression via treatment of porcine satellite cells with recombinant NF-κB increases the proliferation of porcine satellite cells. The alteration of porcine satellite cell proliferation is associated with significant changes in the expression of cell cycle related genes (cyclin B1, D1, D2, E1 and p21), myogenic regulatory factors (MyoD and myogenin) and the Notch effector Hes5. In addition, alteration of Notch1 expression in porcine satellite cells causes changes in the expression of GSK3β-3. Taken together, these findings suggest that of the four notch-related genes, Notch1is likely to be required for regulating the proliferation and therefore the maintenance of porcine satellite cells in vivo, and do so through activation of the Notch effector gene Hes5.

Small molecules that recapitulate the early steps of urodele amphibian limb regeneration and confer multipotency

In urodele amphibians, an early step in limb regeneration is skeletal muscle fiber dedifferentiation into a cellulate that proliferates to contribute new limb tissue. However, mammalian muscle cannot dedifferentiate after injury. We have developed a novel, small-molecule-based method to induce dedifferentiation in mammalian skeletal muscle. Muscle cellularization was induced by the small molecule myoseverin. Candidate small molecules were tested for the induction of proliferation in the cellulate. We observed that treatment with the small molecules BIO (glycogen synthase-3 kinase inhibitor), lysophosphatidic acid (pleiotropic activator of G-protein-coupled receptors), SB203580 (p38 MAP kinase inhibitor), or SQ22536 (adenylyl cyclase inhibitor) induced proliferation. Moreover, these proliferating cells were multipotent, as confirmed by the chemical induction of mesodermal-derived cell lineages. Microarray analysis showed that the multipotent, BIO-treated cellulate possessed a markedly different gene expression pattern than lineage-restricted C2C12 myoblasts, especially for genes related to signal transduction and differentiation. Sequential small molecule treatment of the muscle cellulate with BIO, SB203580, or SQ22536 and the aurora B kinase inhibitor, reversine, induced the formation of cells with neurogenic potential (ectodermal lineage), indicating the acquirement of pluripotency. This is the first demonstration of a small molecule method that induces mammalian muscle to undergo dedifferentiation and rededifferentiation into alternate cell lineages. This method induces dedifferentiation in a simple, stepwise approach and has therapeutic potential to enhance tissue regeneration in mammals.

Fibroblasts have plasticity and potential utility for cell therapy

Fibroblasts exist in the interstices of various organs as a component of connective tissue and are one of several types of somatic cells that have been well established in culture. They have been reported to undergo myogenic conversion and to induce the expression of genes associated with pluripotency. However, their own plasticity with regard to direct differentiation has scarcely been described. Here, we show that human fibroblasts are able to differentiate directly to all three germ layer derivatives. The results indicate that human dermal fibroblasts have more plasticity than has been generally thought and that fibroblasts have potential utility as a source for cell therapy.

Stem cell therapies to treat muscular dystrophy: progress to date

Muscular dystrophies are heritable, heterogeneous neuromuscular disorders and include Duchenne and Becker muscular dystrophies (DMD and BMD, respectively). DMD patients exhibit progressive muscle weakness and atrophy followed by exhaustion of muscular regenerative capacity, fibrosis, and eventually disruption of the muscle tissue architecture. In-frame mutations in the dystrophin gene lead to expression of a partially functional protein, resulting in the milder BMD. No effective therapies are available at present. Cell-based therapies have been attempted in an effort to promote muscle regeneration, with the hope that the host cells would repopulate the muscle and improve muscle function and pathology. Injection of adult myoblasts has led to the development of new muscle fibers, but several limitations have been identified, such as poor cell survival and limited migratory ability. As an alternative to myoblasts, stem cells were considered preferable for therapeutic applications because of their capacity for self-renewal and differentiation potential. In recent years, encouraging results have been obtained with adult stem cells to treat human diseases such as leukemia, Parkinson's disease, stroke, and muscular dystrophies. Embryonic stem cells (ESCs) can be derived from mammalian embryos in the blastocyst stage, and because they can differentiate into a wide range of specialized cells, they hold potential for use in treating almost all human diseases. Several ongoing studies focus on this possibility, evaluating differentiation of specific cell lines from human ESCs (hESCs) as well as the potential tumorigenicity of hESCs. The most important limitation with using hESCs is that it requires destruction of human blastocysts or embryos. Conversely, adult stem cells have been identified in various tissues, where they serve to maintain, generate, and replace terminally differentiated cells within their specific tissue as the need arises for cell turnover or from tissue injury. Moreover, these cells can participate in regeneration of more than just their specific tissue type. Here we describe multiple types of muscle- and fetal-derived myogenic stem cells, their characterization, and their possible use in treating muscular dystrophies such as DMD and BMD. We also emphasize that the most promising possibility for the management and therapy of DMD and BMD is a combination of different approaches, such as gene and stem cell therapy.

Identification and characterization of a non-satellite cell muscle resident progenitor during postnatal development

Satellite cells are resident myogenic progenitors in postnatal skeletal muscle involved in muscle postnatal growth and adult regenerative capacity. Here, we identify and describe a population of muscle-resident stem cells, which are located in the interstitium, that express the cell stress mediator PW1 but do not express other markers of muscle stem cells such as Pax7. PW1(+)/Pax7(-) interstitial cells (PICs) are myogenic in vitro and efficiently contribute to skeletal muscle regeneration in vivo as well as generating satellite cells and PICs. Whereas Pax7 mutant satellite cells show robust myogenic potential, Pax7 mutant PICs are unable to participate in myogenesis and accumulate during postnatal growth. Furthermore, we found that PICs are not derived from a satellite cell lineage. Taken together, our findings uncover a new and anatomically identifiable population of muscle progenitors and define a key role for Pax7 in a non-satellite cell population during postnatal muscle growth.

Autoregulatory loop of Msx1 expression involving its antisense transcripts

The Msx1 homeogene plays an important role in epithelial-mesenchymal interactions leading organogenesis. Msx1 gene is submitted to bidirectional transcription generating a long non-coding antisense (AS) RNA potentially involved in Msx1 expression regulation. RT-Q-PCR and RNA-FISH studies indicated that transient overexpression of the Msx1 AS transcript in 705IC5 mouse odontoblasts decreased the abundance of endogenous Msx1 S mRNA at the post-transcriptional level. Conversely, Msx1 overexpression increased the AS RNA level probably by activating AS transcription. In vivo mapping by RT-PCR evidenced both Msx1 RNAs in all adult mouse tissues tested raising the issue of Msx1 function during adulthood. The expression patterns of the two RNAs were similar, confirming the tight S/AS relationship. In particular, both Msx1 mRNAs and Msx1 protein were similarly distributed in eyes, and were found in regions with a common ectodermic origin and in cells potentially involved in regeneration. In conclusion, we report that Msx1 S RNA is negatively controlled by its AS RNA at a post-transcriptional level, and that the AS RNA is retrocontrolled positively by Msx1. The tight link between Msx1 S and AS RNAs constitutes a regulatory loop resulting in a fine-tuned expression of Msx1 which appears to be significant for adult homeostasis.

Psidium guajava: a review of its traditional uses, phytochemistry and pharmacology

Psidium guajava, is an important food crop and medicinal plant in tropical and subtropical countries is widely used like food and in folk medicine around of the world. This aims a comprehensive of the chemical constituents, pharmacological, and clinical uses. Different pharmacological experiments in a number of in vitro and in vivo models have been carried out. Also have been identified the medicinally important phyto-constituents. A number of metabolites in good yield and some have been shown to possess useful biological activities belonging mainly to phenolic, flavonoid, carotenoid, terpenoid and triterpene. Extracts and metabolites of this plant, particularly those from leaves and fruits possess useful pharmacological activities. A survey of the literature shows P. guajava is mainly known for its antispasmodic and antimicrobial properties in the treatment of diarrhoea and dysentery. Has also been used extensively as a hypoglycaemic agent. Many pharmacological studies have demonstrated the ability of this plant to exhibit antioxidant, hepatoprotection, anti-allergy, antimicrobial, antigenotoxic, antiplasmodial, cytotoxic, antispasmodic, cardioactive, anticough, antidiabetic, antiinflamatory and antinociceptive activities, supporting its traditional uses. Suggest a wide range of clinical applications for the treatment of infantile rotaviral enteritis, diarrhoea and diabetes.