Inflammation and microenvironment play a crucial role in muscle regeneration. IL (interleukin)-6, as a multifunctional cytokine is involved in the processes. However, the causative effect of IL-6 in ...muscle regeneration remains unclear. In a mouse model of cardiotoxin-induced muscle injury/regeneration, infiltrated monocytes/macrophages produce a high level of IL-6 started on 1 day (24 h) after injury. In IL-6 knock-out (−/−) mice, the muscle regeneration procedure was impaired along with decreased myogenic determination factor (MyoD) and myogenin mRNA level and increased interstitial fibrosis. The IL-6−/− mice exhibited less macrophage infiltration, lower inflammatory cytokine (IL-1β, inducible NO synthase, Transforming growth factor (TGF)-β1, and IL-10) and chemokine (CCL2, CCL3, and CCL5) expression, and inhibited myoblast proliferation. In vitro, IL-6 deficiency or Signal Transducer and Activator of Transcription 3 (STAT3) knockdown in activated macrophage attenuated the expression of CCL2, CCL3, but not CCL5, which resulted in less macrophage migration. Moreover, inflammatory macrophages promoted myoblast proliferation in an IL-6-dependent manner. Finally, adoptive transfer IL-6+/+ BM cells into IL-6−/− mice rescued the impaired regeneration with improved MyoD and myogenin expression. Taken together, IL-6 expression and the activated STAT3 signaling pathway in monocytes/macrophages is a critical mediator of macrophage migration and myoblast proliferation during muscle regeneration.
Background: Interleukin-6 (IL-6), as a multifunctional cytokine, was involved in the inflammation microenvironment of muscle regeneration.
Results: In mice lacking IL-6, less macrophage recruitment and decreased myoblast proliferation impairs muscle regeneration.
Conclusion: In monocytes/macrophages, activation of the IL-6/STAT3 pathway is critical to macrophage migration and myoblast proliferation during muscle regeneration.
Significance: IL-6/STAT3 pathway is essential for muscle regeneration.
Sporadic inclusion body myositis (sIBM) is the most common idiopathic inflammatory myopathy, and several reports have suggested that mitochondrial abnormalities are involved in its etiology. We ...recruited 9 sIBM patients and found significant histological changes and an elevation of growth differential factor 15 (GDF15), a marker of mitochondrial disease, strongly suggesting the involvement of mitochondrial dysfunction. Bioenergetic analysis of sIBM patient myoblasts revealed impaired mitochondrial function. Decreased ATP production, reduced mitochondrial size and reduced mitochondrial dynamics were also observed in sIBM myoblasts. Cell vulnerability to oxidative stress also suggested the existence of mitochondrial dysfunction. Mitochonic acid-5 (MA-5) increased the cellular ATP level, reduced mitochondrial ROS, and provided protection against sIBM myoblast death. MA-5 also improved the survival of sIBM skin fibroblasts as well as mitochondrial morphology and dynamics in these cells. The reduction in the gene expression levels of Opa1 and Drp1 was also reversed by MA-5, suggesting the modification of the fusion/fission process. These data suggest that MA-5 may provide an alternative therapeutic strategy for treating not only mitochondrial diseases but also sIBM.
Abstract Graphene-based nanomaterials have received much attention in biomedical applications for drug/gene delivery, cancer therapy, imaging, and tissue engineering. Despite the capacity of 2D ...carbon materials as a nontoxic and implantable platform, their effect on myogenic differentiation has been rarely studied. We investigated the myotube formation on graphene-based nanomaterials, particularly graphene oxide (GO) and reduced graphene oxide (rGO). GO sheets were immobilized on amine-modified glass to prepare GO-modified glass, which was further reduced by hydrazine treatment for the synthesis of rGO-modified substrate. We studied the behavior, including adhesion, proliferation, and differentiation, of mouse myoblast C2C12 on unmodified, GO-, and rGO-modified glass substrates. According to our analyses of myogenic protein expression, multinucleate myotube formation, and expression of differentiation-specific genes ( MyoD , myogenin , Troponin T , and MHC ), myogenic differentiation was remarkably enhanced on GO, which resulted from serum protein adsorption and nanotopographical cues. Our results demonstrate the ability of GO to stimulate myogenic differentiation, showing a potential for skeletal tissue engineering applications.
Muscle stem cells are a potent cell population dedicated to efficacious skeletal muscle regeneration, but their therapeutic utility is currently limited by mode of delivery. We developed a cell ...delivery strategy based on a supramolecular liquid crystal formed by peptide amphiphiles (PAs) that encapsulates cells and growth factors within a muscle-like unidirectionally ordered environment of nanofibers. The stiffness of the PA scaffolds, dependent on amino acid sequence, was found to determine the macroscopic degree of cell alignment templated by the nanofibers in vitro. Furthermore, these PA scaffolds support myogenic progenitor cell survival and proliferation and they can be optimized to induce cell differentiation and maturation. We engineered an in vivo delivery system to assemble scaffolds by injection of a PA solution that enabled coalignment of scaffold nanofibers with endogenous myofibers. These scaffolds locally retained growth factors, displayed degradation rates matching the time course ofmuscle tissue regeneration, and markedly enhanced the engraftment of muscle stem cells in injured and noninjured muscles in mice.
Mangosteen, a fruit mainly produced in Southeast Asia, has been used as food and as an antipyretic and for treating skin diseases. The xanthones contained in mangosteen have many physiological ...activities including melanin suppression and anticancer activities, but little is known about the physiological effects of the most abundant xanthone, α-mangostin (α-MG) on myoblasts. In this study, we applied α-MG to C2C12 cells that had been induced to differentiate using 2% HS, and analyzed the physiological action of α-MS and the underlying mechanism in the context of myogenic differentiation. α-MG increased the survival rate of C2C12 cells in a concentration-dependent manner. Analysis of the morphological changes in the cells showed that α-MG significantly enhanced the myogenic differentiation of C2C12 myoblasts, whereas the mitochondrial number was only slightly affected. Expression analysis of differentiation-related proteins in C2C12 cells revealed that α-MG promoted the expression of MyoD and Myogenin. Thus, the present study revealed that α-MG improves the survival and myogenic differentiation of C2C12 myoblasts.
•α-Mangostin (α-MG) increased C2C12 cell survival.•α-MG significantly enhanced the myogenic differentiation of C2C12 myoblasts.•α-MG promoted the expression of MyoD and Myogenin proteins.
•Mesenchymal stem cell exosomes promoted myogenesis and angiogenesis in vitro.•Mesenchymal stem cell exosomes accelerated muscle regeneration in a mouse injury model.•Mesenchymal stem cell exosomes ...had low concentrations of repair-related cytokines.•Many repair-related microRNAs were identified in mesenchymal stem cell exosomes.•MicroRNA-494 in mesenchymal stem cell exosomes enhanced myogenesis and angiogenesis.
Mesenchymal stem cell (MSC) transplantation is used for treatment of many diseases. The paracrine role of MSCs in tissue regeneration is attracting particular attention. We investigate the role of MSC exosomes in skeletal muscle regeneration. MSC exosomes promote myogenesis and angiogenesis in vitro, and muscle regeneration in an in vivo model of muscle injury. Although MSC exosomes had low concentrations of muscle-repair-related cytokines, a number of repair-related miRNAs were identified. This study suggests that the MSC-derived exosomes promote muscle regeneration by enhancing myogenesis and angiogenesis, which is at least in part mediated by miRNAs such as miR-494.
In this study, we designed a cell-adhesive poly(ethylene glycol) (PEG)-based hydrogel that simultaneously provides topographical and electrical stimuli to C2C12 myoblasts. Specifically, PEG ...hydrogels with microgroove structures of 3 μm ridges and 3 μm grooves were prepared by micromolding; in situ polymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) was then performed within the micropatterned PEG hydrogels to create a microgrooved conductive hydrogel (CH/P). The CH/P had clear replica patterns of the silicone mold and a conductivity of 2.49 × 10–3 S/cm, with greater than 85% water content. In addition, the CH exhibited Young’s modulus (45.84 ± 7.12 kPa) similar to that of a muscle tissue. The surface of the CH/P was further modified via covalent bonding with cell-adhesive peptides to facilitate cell adhesion without affecting conductivity. An in vitro cell assay revealed that the CH/P was cytocompatible and enhanced the cell alignment and elongation of C2C12 myoblasts. The microgrooves and conductivity of the CH/P had the greatest positive effect on the myogenesis of C2C12 myoblasts compared to the other PEG hydrogel samples without conductivity or/and microgrooves, even in the absence of electrical stimulation. Electrical stimulation studies indicated that the combination of topographical and electrical cues maximized the differentiation of C2C12 myoblasts into myotubes, confirming the synergetic effect of incorporating microgroove surface features and a conductive PEDOT component into hydrogels.
Caspase-2, -9, and -3 are reported to control myoblast differentiation into myotubes. This had been previously explained by phosphatidylserine exposure on apoptotic myoblasts inducing differentiation ...in neighboring cells. Here we show for the first time that caspase-3 is activated in the myoblasts undergoing differentiation. Using RNAi, we also demonstrate that differentiation requires both cytochrome c and Apaf-1, and by using a new pharmacological approach, we show that apoptosome formation is required. We also show that Bid, whose cleavage links caspase-2 to the mitochondrial death pathway, was required for differentiation, and that the caspase cleavage product, tBid, was generated during differentiation. Taken together, these data suggest that myoblast differentiation requires caspase-2 activation of the mitochondrial death pathway, and that this occurs in the cells that differentiate. Our data also reveal a hierarchy of caspases in differentiation with caspase-2 upstream of apoptosome activation, and exerting a more profound control of differentiation, while caspases downstream of the apoptosome primarily control cell fusion.
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Mimicking the nanofibrous structure similar to extracellular matrix and conductivity for electrical propagation of native myocardium would be highly beneficial for cardiac tissue ...engineering and cardiomyocytes-based bioactuators. Herein, we developed conductive nanofibrous sheets with electrical conductivity and nanofibrous structure composed of poly(l-lactic acid) (PLA) blending with polyaniline (PANI) for cardiac tissue engineering and cardiomyocytes-based 3D bioactuators. Incorporating of varying contents of PANI from 0wt% to 3wt% into the PLA polymer, the electrospun nanofibrous sheets showed enhanced conductivity while maintaining the same fiber diameter. These PLA/PANI conductive nanofibrous sheets exhibited good cell viability and promoting effect on differentiation of H9c2 cardiomyoblasts in terms of maturation index and fusion index. Moreover, PLA/PANI nanofibrous sheets enhanced the cell-cell interaction, maturation and spontaneous beating of primary cardiomyocytes. Furthermore, the cardiomyocytes-laden PLA/PANI conductive nanofibrous sheets can form 3D bioactuators with tubular and folding shapes, and spontaneously beat with much higher frequency and displacement than that on cardiomyocytes-laden PLA nanofibrous sheets. Therefore, these PLA/PANI conductive nanofibrous sheets with conductivity and extracellular matrix like nanostructure demonstrated promising potential in cardiac tissue engineering and cardiomyocytes-based 3D bioactuators.
Cardiomyocytes-based bioactuators have been paid more attention due to their spontaneous motion by integrating cardiomyocytes into polymer structures, but developing suitable scaffolds for bioactuators remains challenging. Electrospun nanofibrous scaffolds have been widely used in cardiac tissue engineering because they can mimic the extracellular matrix of myocardium. Developing conductive nanofibrous scaffolds by electrospinning would be beneficial for cardiomyocytes-based bioactuators, but such scaffolds have been rarely reported. This work presented a conductive nanofibrous sheet based on polylactide and polyaniline via electrospinning with tunable conductivity. These conductive nanofibrous sheets performed the ability to enhance cardiomyocytes maturation and spontaneous beating, and further formed cardiomyocytes-based 3D bioactuators with tubular and folding shapes, which indicated their great potential in cardiac tissue engineering and bioactuators applications.
Myogenesis is a multistep process that requires a spatiotemporal regulation of cell events resulting finally in myoblast fusion into multinucleated myotubes. Most major insights into the mechanisms ...underlying fusion seem to be conserved from insects to mammals and include the formation of podosome-like protrusions (PLPs) that exert a driving force toward the founder cell. However, the machinery that governs this process remains poorly understood. In this study, we demonstrate that MTM1 is the main enzyme responsible for the production of phosphatidylinositol 5-phosphate, which in turn fuels PI5P 4-kinase α to produce a minor and functional pool of phosphatidylinositol 4,5-bisphosphate that concentrates in PLPs containing the scaffolding protein Tks5, Dynamin-2, and the fusogenic protein Myomaker. Collectively, our data reveal a functional crosstalk between a PI-phosphatase and a PI-kinase in the regulation of PLP formation.
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