Résumé :
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With age, there is a gradual decline in the effectiveness of the regenerative response of skeletal muscle to damage which is accompanied by muscle fiber atrophy and a general loss of muscle mass and function. Age-related muscle wasting, like the decline in the regenerative capacity may be due to the decrease in the number of muscle precursor cells (satellite cells) as well as to an age-related decline in satellite cell function. It has been suggested that the decreased level of the circulating trophic factors that occurs with age could also contribute to the decrease in muscle mass, force and regenerative capacity described in the elderly. The aim of this study was to identify secreted muscle proteins essential for the maintenance of the regenerative capacity of the resident satellite cells and to characterize differences in the global pattern of protein expression observed in a model of muscle ageing: the replicative senescence of human satellite cells in vitro. Conditioned medium from differentiating primary cultures at an early passage and at senescence were analyzed by a proteomic approach using 3 different expression profiling strategies: 1) 2D gel electrophoresis/mass spectrometry (2DE/MS); 2) Luminex based assay; 3) mass spectrometry (MS) based approach. A time course of myoblast secretion at early passage and late passage in “Differentiation medium” revealed a 3 to 4-fold decrease in the total amount of protein secreted during the senescence process associated with considerable qualitative and quantitative changes in the secretome. Preliminary data from 2DE/MS & Luminex expression profiling has enabled us to identify 44 molecules differentially “secreted” during muscle ageing in vitro: senescent myoblasts expressed a similar panel of inflammatory cytokines as previously reported for senescent fibroblasts associated with an upregulation of key regulators of matrix remodelling. Results of the MS based approach will be obtained in the near future.
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