Mesenchymal stromal cells (MSCs) are the leading cell candidates in the field of regenerative medicine. These cells have also been successfully used to improve skeletal muscle repair/regeneration; ...however, the mechanisms responsible for their beneficial effects remain to be clarified. On this basis, in the present study, we evaluated in a co-culture system, the ability of bone-marrow MSCs to influence C2C12 myoblast behavior and analyzed the cross-talk between the two cell types at the cellular and molecular level. We found that myoblast proliferation was greatly enhanced in the co-culture as judged by time lapse videomicroscopy, cyclin A expression and EdU incorporation. Moreover, myoblasts immunomagnetically separated from MSCs after co-culture expressed higher mRNA and protein levels of Notch-1, a key determinant of myoblast activation and proliferation, as compared with the single culture. Notch-1 intracellular domain and nuclear localization of Hes-1, a Notch-1 target gene, were also increased in the co-culture. Interestingly, the myoblastic response was mainly dependent on the paracrine release of vascular endothelial growth factor (VEGF) by MSCs. Indeed, the addition of MSC-derived conditioned medium (CM) to C2C12 cells yielded similar results as those observed in the co-culture and increased the phosphorylation and expression levels of VEGFR. The treatment with the selective pharmacological VEGFR inhibitor, KRN633, resulted in a marked attenuation of the receptor activation and concomitantly inhibited the effects of MSC-CM on C2C12 cell growth and Notch-1 signaling. In conclusion, this study provides novel evidence for a role of MSCs in stimulating myoblast cell proliferation and suggests that the functional interaction between the two cell types may be exploited for the development of new and more efficient cell-based skeletal muscle repair strategies.
MicroRNAs (miRNAs) are a class of small non-coding RNAs that repress the expression of their target genes post-transcriptionally. MiRNAs participate in the regulation of a variety of biological ...processes, including development and diseases. However, the functional role and molecular mechanism by which miRNAs regulate skeletal muscle development and differentiation are not fully understood. In this report, we identified miR-23a as a key regulator of skeletal muscle differentiation. Using bioinformatics analyses, miR-23a is predicted to target multiple adult fast myosin heavy chain (Myh) genes, including Myh 1, 2 and 4. Luciferase reporter assays show that miR-23a directly targets the 3′ untranslated regions (UTRs) of these mRNAs. Interestingly, the expression level of mature miR-23a is inversely correlated with myogenic progression in mouse skeletal muscle. Both gain- and loss-of-function studies using C2C12 myoblasts demonstrate that miR-23a inhibits myogenic differentiation. These findings therefore reveal a novel role of miR-23a in regulating myogenic differentiation via inhibiting the expression of fast myosin heavy chain isoforms.
Circular RNAs (circRNAs) are an indispensable element of post‐transcriptional gene regulation, influencing a variety of biological processes including myogenic differentiation; however, little is ...known about the function of circRNA in goat myogenic differentiation. Using RNA‐sequencing data from our laboratory, we explored the influences of circUSP13, as a candidate circRNA, on myoblast differentiation since its expression is higher in myoblasts of lamb (first day of age) than that of the fetus (75th day of pregnancy). In in vitro experiments, circUSP13 significantly promoted differentiation and inhibited apoptosis in goat primary myoblasts. Mechanistically, circUSP13 localized with miR‐29c in the cytoplasm of goat myoblasts to regulate IGF1 expression. We further demonstrated that circUSP13 sponges miR‐29c, promoting IGF1 expression that upregulated the expression of MyoG and MyHC. Thus, our results identified circUSP13 as a molecular marker for breeding programs of mutton production, as well as the circUSP13‐miR‐29c‐IGF1 axis as a potential therapeutic target for combating muscle wasting.
Myoferlin (MyoF), which is a calcium/phospholipid-binding protein expressed in cardiac and muscle tissues, belongs to the ferlin family. While MyoF promotes myoblast differentiation, the underlying ...mechanisms remain poorly understood. Here, we found that MyoF not only promotes C2C12 myoblast differentiation, but also inhibits muscle atrophy and autophagy. In the present study, we found that myoblasts fail to develop into mature myotubes due to defective differentiation in the absence of MyoF. Meanwhile, MyoF regulates the expression of atrophy-related genes (Atrogin-1 and MuRF1) to rescue muscle atrophy. Furthermore, MyoF interacts with Dishevelled-2 (Dvl-2) to activate canonical Wnt signaling. MyoF facilitates Dvl-2 ubiquitination resistance by reducing LC3-labeled Dvl-2 levels and antagonizing the autophagy system. In conclusion, we found that MyoF plays an important role in myoblast differentiation during skeletal muscle atrophy. At the molecular level, MyoF protects Dvl-2 against autophagy-mediated degradation, thus promoting activation of the Wnt/β-catenin signaling pathway. Together, our findings suggest that MyoF, through stabilizing Dvl-2 and preventing autophagy, regulates Wnt/β-catenin signaling-mediated skeletal muscle development.
ABSTRACTTraumatic strain injury in skeletal muscle is often associated with fluid accumulation at the site of rupture, but the role of this injury exudate (EX) in cellular responses and healing is ...unknown. We aimed to characterize the EX sampled from human hamstring or calf muscles following a strain injury (n = 12). The cytokine and growth‐factor profile, gene expression, and transcriptome analysis of EX‐derived cells were compared with blood taken simultaneously from the same individuals. Cellular responses to the EX were tested in 3‐dimensional (3D) culture based on primary human fibroblasts and myoblasts isolated from hamstring muscles. The EX contained a highly proinflammatory profile with a substantial expression of angiogenic factors. The proinflammatory profile was present in samples taken early postinjury and in samples aspirated several weeks postinjury, suggesting persistent inflammation. Cells derived from the EX demonstrated an increased expression of fibrogenic, adipogenic, and angiogenesis‐related genes in comparison with blood cells. The injury EX stimulated fibroblast proliferation 2‐fold compared with plasma, whereas such an effect was not seen for myoblasts. Finally, in 3D cell culture, the EX induced an up‐regulation of connective tissue‐related genes. In summary, EX formation following a muscle‐strain injury stimulates fibroblast proliferation and the synthesis of connective tissue in fibroblasts. This suggests that the EX promotes an acute tissue‐healing response but potentially also contributes to the formation of fibrotic tissue in the later phases of tissue repair.—Bayer, M. L., Bang, L., Hoegberget‐Kalisz, M., Svensson, R. B., Olesen, J. L., Karlsson, M. M., Schjerling, P., Hellsten, Y., Hoier, B., Magnusson, S. P., Kjaer, M. Muscle‐strain injury exudate favors acute tissue healing and prolonged connective tissue formation in humans. FASEB J. 33,10369–10382 (2019). www.fasebj.org
Ageing and chronic diseases lead to muscle loss and impair the regeneration of skeletal muscle. Thus, it's crucial to seek for effective intervention to improve the muscle regeneration. Tid1, a ...mitochondrial co-chaperone, is important to maintain mitochondrial membrane potential and ATP synthesis. Previously, we demonstrated that mice with skeletal muscular specific Tid1 deficiency displayed muscular dystrophy and postnatal lethality. Tid1 can interact with STAT3 protein, which also plays an important role during myogenesis. In this study, we used GMI, immunomodulatory protein of Ganoderma microsporum, as an inducer in C2C12 myoblast differentiation. We observed that GMI pretreatment promoted the myogenic differentiation of C2C12 myoblasts. We also showed that the upregulation of mitochondria protein Tid1 with the GMI pre-treatment promoted myogenic differentiation ability of C2C12 cells. Strikingly, we observed the concomitant elevation of STAT3 acetylation (Ac-STAT3) during C2C12 myogenesis. Our study suggests that GMI promotes the myogenic differentiation through the activation of Tid1 and Ac-STAT3.
Myocytes withdraw from the cell cycle to differentiate during muscle development. Given the capacity of microRNAs (miRNAs) to regulate gene expression during development, we screened for miRNAs that ...were associated with muscle development. S-Poly(T) Plus analysis of 273 miRNAs in porcine longissimus dorsi muscles revealed 14 miRNAs that were strongly upregulated with age of postnatal muscle development
, including miR-195 and miR-497. These two miRNAs were also strongly upregulated at late differentiation stages of mouse skeletal myoblast C2C12 cells, and demethylation treatment induced significant upregulation of miR-195/497. Manipulation of miR-195/497 expression resulted in dramatic changes in the proliferation and differentiation of C2C12 cells. We identified high-mobility group AT-hook 1 (
) mRNA as a highly conserved target of miR-195/497 in C2C12 myoblasts. Overexpression of miR-195/497 or
silencing in C2C12 cells promoted myogenic differentiation. Moreover, we showed that miR-195/497 repressed
, which in turn downregulated one of the HMGA1 downstream targets
, whose inhibitory effect on myogenic differentiation is well established. Our study revealed a subset of potential development-associated miRNAs and suggests a novel regulatory axis for myogenesis in which miR-195/497 promote myogenic differentiation by repressing the HMGA1-Id3 pathway.
For several tissue engineering applications, in particular food products, scaling up culture of mammalian cells is a necessary task. The prevailing method for large scale cell culture is the stirred ...tank bioreactor where anchor dependent cells are grown on microcarriers suspended in medium. We use a spinner flask system with cells grown on microcarriers to optimize the growth of bovine myoblasts. Freshly isolated primary cells were seeded on microcarriers (Synthemax
®
, CellBIND
®
and Cytodex
®
1 MCs). In this study, we provide proof of principle that bovine myoblasts can be cultured on microcarriers. No major differences were observed between the three tested microcarriers, except that sparsely populated beads were more common with CellBIND
®
and Synthemax
®
II beads suggesting a slower initiation of exponential growth than on Cytodex
®
. We also provide direct evidence that bovine myoblasts display bead-to-bead transfer. A remarkable pick up of growth was observed by adding new MCs. Bovine myoblasts seem to behave like human mesenchymal stem cells. Thus, our results provide valuable data to further develop and scale-up the production of bovine myoblasts as a prerequisite for efficient and cost-effective development of cultured meat. Applicability to other anchorage dependent cells can extend the importance of these results to cell culture for medical tissue engineering or cell therapy.
Facioscapulohumeral dystrophy (FSHD) is a muscular hereditary disease with a prevalence of 1 in 20,000 caused by a partial deletion of a subtelomeric repeat array on chromosome 4q. However, very ...little is known about the pathogenesis as well as the molecular and biochemical changes linked to the progressive muscle degeneration observed in these patients. Several studies have investigated possible pathophysiological pathways in FSHD myoblasts and mature muscle cells but some of these reports were apparently in contradiction. The discrepancy between these studies may be explained by differences between the sources of myoblasts. Therefore, we decided to thoroughly analyze affected and unaffected muscles from patients with FSHD in terms of vulnerability to oxidative stress, differentiation capacity and morphological abnormalities. We have established a panel of primary myoblast cell cultures from patients affected with FSHD and matched healthy individuals. Our results show that primary myoblasts are more susceptible to an induced oxidative stress than control myoblasts. Moreover, we demonstrate that both types of FSHD primary myoblasts differentiate into multi‐nucleated myotubes, which present morphological abnormalities. Whereas control myoblasts fuse to form branched myotubes with aligned nuclei, FSHD myoblasts fuse to form either thin and branched myotubes with aligned nuclei or large myotubes with random nuclei distribution. In conclusion, we postulate that these abnormalities could be responsible for muscle weakness in patients with FSHD and provide an important marker for FSHD myoblasts.
PDF
