Skeletal Muscle HIF-1α Expression Is Dependent on Muscle Fiber Type

Oxygen homeostasis is an essential regulation system for cell energy production and survival. The oxygen-sensitive subunit α of the hypoxia inducible factor-1 (HIF-1) complex is a key protein of this system. In this work, we analyzed mouse and rat HIF-1α protein and mRNA expression in parallel to energetic metabolism variations within skeletal muscle. Two physiological situations were studied using HIF-1α–specific Western blotting and semiquantitative RT-PCR. First, we compared HIF-1α expression between the predominantly oxidative soleus muscle and three predominantly glycolytic muscles. Second, HIF-1α expression was assessed in an energy metabolism switch model that was based on muscle disuse. These two in vivo situations were compared with the in vitro HIF-1α induction by CoCl2 treatment on C2C12 mouse muscle cells. HIF-1α mRNA and protein levels were found to be constitutively higher in the more glycolytic muscles compared with the more oxidative muscles. Our results gave rise to the hypothesis that the oxygen homeostasis regulation system depends on the fiber type

Caractérisation de trois nouveaux gènes impliqués dans le développement et les adaptations fonctionnelles du muscle squelettique (BTBD1, SMHS1 et myoduline)

Ce travail de thèse a été focalisé sur la caractérisation moléculaire et fonctionnelle de trois nouveaux gènes exprimés préférentiellement dans le muscle squelettique et impliqués soit dans le déterminisme musculaire pour BTBD1, soit dans les adaptations fonctionnelles du muscle lors de changement d'activité pour SMHS1 et la myoduline. L'étude de BTBD1, protéine liant la DNA topoisomérase 1 (Topo1), a montré qu'il s'agissait d'une protéine spécifiquement impliquée dans la différenciation du muscle squelettique. En effet, la surexpression d'une forme tronquée de BTBD1 dans des cellules myoblastiques, entraîne un dysfonctionnement de la différenciation musculaire, mais pas de l'adipogenèse, associée semble t'il à une dérégulation de l'activité de Topo1. L'expression des gènes de SMHS1 et de la myoduline est altérée dans les phénomènes d'atrophie et/ou d'hypertrophie musculaire du rat. Dans le cas de SMHS1, nous avons démontré son implication dans les adaptations du muscle squelettique à un changement métabolique, et cela en parallèle avec le gène de HIF-1a. La myoduline a pu être caractérisée comme étant une protéine membranaire du système musculo-tendineux. De plus, nous avons démontré in vitro, que la surexpression de la myoduline par des cellules musculaires a pour conséquence de favoriser la capacité invasive de cellules endothéliales. La myoduline semble donc posséder les caractéristiques d'un facteur pro-angiogénique, qui pourrait être restreint aux muscles squelettiques. Au final, ce travail de thèse a donc permis d'avancer la caractérisation de ces trois gènes (BTBD1, SMHS1 et la myoduline) et ouvre de nouvelles perspectives pour une meilleure compréhension des mécanismes de différenciation et de modification de la plasticité musculaire.The objective of this study was to characterise from molecular and functional points of view, three novel genes preferentially expressed in skeletal muscle and involved in muscular determination for BTBD1, or in skeletal muscle adaptations during activity modification for SMHS1 and myodulin. The study of BTBD1, a DNA topoisomerase 1 (Topo1) interacting protein, described it as an essential and specific protein for the skeletal muscle differentiation. Indeed, a truncated BTBD overexpression in myoblasts induces a myogenesis disruption, but these cells are able to promote adipogenesis. This effect may be linked to a Topo1 activity alteration. SMHS1 and myodulin gene expression is altered in rat skeletal muscle atrophy and hypertrophy. For SMHS1, it has been demonstrated that its expression level, concomitant to HIF-1a gene expression, is involved in skeletal muscle adaptations to metabolism switch. Myodulin is a membrane protein expressed in the myotendinous system. Moreover, it has been demonstrated that in vitro, myodulin overexpression by muscle cells promotes invasive capacity of endothelial cells. This protein seems to have pro-angiogenic properties which may be restricted to skeletal muscle. Based on this study, three novel genes (coding for BTBD1, SMHS1 and myodulin) have been therefore molecularly and functionally characterised, and new perspectives are now opened for a better understanding of muscular differentiation and plasticity modification.NICE-BU Sciences (060882101) / SudocSudocFranceF

Control of Muscle Fibro-Adipogenic Progenitors by Myogenic Lineage is Altered in Aging and Duchenne Muscular Dystrophy

International audienceFibro-adipogenic progenitors (FAPs), a muscle-resident stem cell population, have recently emerged as important actors of muscle regeneration by interacting with myogenic progenitors (MPs) to promote the formation of new muscle fibers. However, FAPs are also considered as main contributors of intramuscular fibrotic and fat depositions, resulting in a poor quality of muscles and a defective regeneration in aging and Duchenne Muscular Dystrophy disease (DMD). Therefore, the understanding of the control of FAP fate is an important aspect of muscle repair and homeostasis, but little is known in humans. We wondered the extent to which human FAP proliferation, adipogenesis and fibrogenesis can be regulated by human myogenic progenitors (MPs) in physiological and pathological contexts

Enhancement of Myogenic and Muscle Repair Capacities of Human Adipose–derived Stem Cells With Forced Expression of MyoD

Muscle disorders such as Duchenne muscular dystrophy (DMD) still need effective treatments, and mesenchymal stem cells (MSCs) may constitute an attractive cell therapy alternative because they are multipotent and accessible in adult tissues. We have previously shown that human multipotent adipose–derived stem (hMADS) cells were able to restore dystrophin expression in the mdx mouse. The goal of this work was to improve the myogenic potential of hMADS cells and assess the impact on muscle repair. Forced expression of MyoD in vitro strongly induced myogenic differentiation while the adipogenic differentiation was inhibited. Moreover, MyoD-expressing hMADS cells had the capacity to fuse with DMD myoblasts and to restore dystrophin expression. Importantly, transplantation of these modified hMADS cells into injured muscles of immunodepressed Rag2−/−γC−/− mice resulted in a substantial increase in the number of hMADS cell–derived fibers. Our approach combined the easy access of MSCs from adipose tissue, the highly efficient lentiviral transduction of these cells, and the specific improvement of myogenic differentiation through the forced expression of MyoD. Altogether our results highlight the capacity of modified hMADS cells to contribute to muscle repair and their potential to deliver a repairing gene to dystrophic muscles

Muscle regeneration with intermuscular adipose tissue (IMAT) accumulation is modulated by simulated microgravity

Communication orale également présentée à: 36. Annual International Gravitational Physilogy Meeting ; Ljubljana (Slovénie) - (2015-06-07 - 2015-06-12)Muscle regeneration with intermuscular adipose tissue (IMAT) accumulation is modulated by simulated microgravity. 11. Journée de l’École Doctorale en Sciences du Mouvement Humain « SANTE ET PERFORMANCE

Muscle regeneration with intermuscular adipose tissue (IMAT) accumulation is modulated by simulated microgravity

Muscle regeneration with intermuscular adipose tissue (IMAT) accumulation is modulated by simulated microgravity. 11. Journée de l’École Doctorale en Sciences du Mouvement Humain « SANTE ET PERFORMANCE