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Aging of cultured human myotubes

ABSTRACT: Aging of skeletal muscle tissue is characterized by loss of metabolic and contractile competence. It is thought that this phenomenon is driven via extrinsic and intrinsic factors. In order to identify age-dependent changes intrinsic to the muscle cell, microarray transcriptional profiles and measurements of glucose metabolism were performed in primary cultured human myotubes at different time points over seven weeks. Aging in culture tended to reduce myotube glucose metabolism, oxidative and storage capacities, despite elevation of glucose transport. The mitochondrial membrane potential slightly increased, whereas peroxidation of cell membrane lipids declined and membrane integrity was preserved. Transcriptional analysis revealed a fall in genes involved in glucose metabolism and oxidative phosphorylation, while stress defense genes were elevated. Expression of numerous genes coding for muscle contractile proteins and calcium-regulating proteins, was gradually decreased during aging of cultured myotubes. Transcripts of genes involved in cell growth, matrix and motility markedly rose while those involved in cell adhesion dropped. In conclusion, aging myotubes in culture exhibit a loss of glucose metabolic capacity. They are characterized by a shift from a contractile to a growth-survival, matrix-remodeling phenotype. This pattern of changes, linked to intrinsic factors, displays significant similarities with aging of muscle from primates and human subjects. Keywords = aging Keywords = muscle cell biopsy Keywords = myotubes Keywords = glucose Keywords: time-course

ORGANISM(S): Homo sapiens

PROVIDER: GSE1144 | GEO | 2004/05/31

SECONDARY ACCESSION(S): PRJNA87267

REPOSITORIES: GEO

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Project description:Background: Sarcopenia is a common and progressive skeletal muscle disorder characterized by atrophic muscle fibers and contractile dysfunction. Accumulating evidence shows that the number and function of satellite cells (SCs) decline and become impaired during aging, which may contribute to impaired regenerative capacity. A series of myokines/ small extracellular vesicles (sEVs) released from muscle fibers regulate metabolism in muscle and extramuscular tissues in an autocrine/paracrine/endocrine manner during muscle atrophy. It is still unclear whether myokines/sEVs derived from muscle fibers can affect satellite cell function during aging. Methods: Aged mice were used to investigate changes in the myogenic capacity of SCs during aging-induced muscle atrophy. The effects of atrophic myotube-derived sEVs on satellite cell differentiation were investigated by biochemical methods and immunofluorescence staining. Small RNA sequencing was performed to identify differentially expressed sEV microRNAs (miRNAs) between the control myotubes and atrophic myotubes. The target genes of the miRNA were predicted by bioinformatics analysis and verified by luciferase activity assays. The effects of identified miRNA on the myogenic capacity of SCs in vivo were investigated by intramuscular injection of adeno-associated virus (AAV) to overexpress or silence miRNA in skeletal muscle. Results: Our study showed that the myogenic capacity of SCs was significantly decreased (50%, n = 6, P < 0.001) in the tibialis anterior muscle of aged mice. We showed that atrophic myotube-derived sEVs inhibited satellite cell differentiation in vitro (n = 3, P < 0.001) and in vivo (35%, n = 6, P < 0.05). We also found that miR-690 was the most highly enriched miRNA among all the screened sEV miRNAs in atrophic myotubes [Log2 (Fold Change) = 7, P<0.001], which was verified in the atrophic muscle of aged mice (3-fold, n = 6, P < 0.001) and aged humans (2.8-fold, n = 10, P < 0.001). miR-690 can inhibit myogenic capacity of SCs by targeting myocyte enhancer factor 2, including Mef2a, Mef2c, and Mef2d, in vitro (n=3, P < 0.05) and in vivo (n=6, P < 0.05). Specific silencing of miR-690 in the muscle can promote satellite cell differentiation (n = 6, P < 0.001) and alleviate muscle atrophy in aged mice (n = 6, P < 0.001). Conclusions: Our study demonstrated that atrophic muscle fiber-derived sEV miR-690 may inhibit satellite cell differentiation by targeting myocyte enhancer factor 2 during aging.

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Aging of cultured human myotubes

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