Project description:Aging animals undergo a variety of changes in molecular processes. Among these, the cellular circadian clock has been shown to change as animals age. Moreover, there is evidence that also core circadian clock proteins could influence the ageing behavior of vertebrates. To investigate the interplay between aging and the circadian clock, we studied circadian mRNA expression in skeletal muscles from young (8 weeks) and aged (80 weeks) mice. In order to detect differences in circadian patterns, we used microarray-based transcriptome-wide time series of mRNA expression, containing 16 independent measurements for both young and aged animals. Each individual time point consists of total RNA from hind limb skeletal muscles from 3 different animals. Young and aged mice where entrained to 12 hr/12 hr light-dark conditions. From these mice, hind limb skeletal muscles were extracted at different times of day, in order to measure circadian mRNA expression patterns.
Project description:Aging animals undergo a variety of changes in molecular processes. Among these, the cellular circadian clock has been shown to change as animals age. Moreover, there is evidence that also core circadian clock proteins could influence the ageing behavior of vertebrates. To investigate the interplay between aging and the circadian clock, we studied circadian mRNA expression in skeletal muscles from young (8 weeks) and aged (80 weeks) mice. In order to detect differences in circadian patterns, we used microarray-based transcriptome-wide time series of mRNA expression, containing 16 independent measurements for both young and aged animals. Each individual time point consists of total RNA from hind limb skeletal muscles from 3 different animals.
Project description:Skeletal muscle dysfunction in survivors of pneumonia is a major cause of lasting morbidity that disproportionately affects older individuals. We found that skeletal muscle recovery was impaired in aged compared with young mice after influenza A virus-induced pneumonia. In young mice, recovery of muscle loss was associated with expansion of tissue-resident skeletal muscle macrophages and downregulation of MHC II expression, followed by a proliferation of muscle satellite cells. These findings were absent in aged mice and in mice deficient in Cx3cr1. Transcriptomic profiling of tissue-resident skeletal muscle macrophages from aged compared with young mice showed downregulation of pathways associated with phagocytosis and proteostasis, and persistent upregulation of inflammatory pathways. Consistently, skeletal muscle macrophages from aged mice failed to downregulate MHCII expression during recovery from influenza A virus induced pneumonia and showed impaired phagocytic function in vitro. Like aged animals, mice deficient in the phagocytic receptor Mertk showed no macrophage expansion, MHCII downregulation or satellite cell proliferation and failed to recover skeletal muscle function after influenza A pneumonia. Our data suggest that a loss of phagocytic function in a CX3CR1+ tissue-resident skeletal muscle macrophage population in aged mice precludes satellite cell proliferation and recovery of skeletal muscle function after influenza A pneumonia.
Project description:SILAC based protein correlation profiling using size exclusion of protein complexes derived from Mus musculus tissues (Heart, Liver, Lung, Kidney, Skeletal Muscle, Thymus)
Project description:SILAC based protein correlation profiling using size exclusion of protein complexes derived from seven Mus musculus tissues (Heart, Brain, Liver, Lung, Kidney, Skeletal Muscle, Thymus)
Project description:Arrestin Domain Containing 2 and 3 (Arrdc2/3) are genes whose mRNA contents are decreased in young skeletal muscle following mechanical overload. Arrdc3 is linked to the regulation of signaling pathways in non-muscle cells that could influence skeletal muscle size. Despite a similar amino acid sequence, Arrdc2 function remains undefined. The purpose of this study was to further explore the relationship of Arrdc2/Arrdc3 expression with changes in mechanical load in young and aged muscle and define the effect of Arrdc2/3 expression on myotube diameter. In young and aged mice, mechanical load was decreased using hindlimb suspension while mechanical load was increased by reloading previously unloaded muscle or inducing high force contractions. Arrdc2 and Arrdc3 mRNAs were overexpressed in C2C12 myotubes using adenoviruses. Myotube diameter was determined 48 h post-transfection and RNA sequencing was performed on those samples. Arrdc2 and Arrdc3 mRNA content was higher in the unloaded muscle within 1 day of disuse and remained higher up through 10 days. The induction of Arrdc2 mRNA was more pronounced in aged muscle than young muscle in response to unloading. Reloading previously unloaded muscle of young and aged mice restored Arrdc2 and Arrdc3 levels to ambulatory levels. Increasing mechanical load beyond normal ambulatory levels lowered Arrdc2 but not Arrdc3 mRNA in young and aged muscle. Arrdc2, not Arrdc3, overexpression was sufficient to lower myotube diameter in C2C12 cells in part by altering the transcriptome favoring muscle atrophy. These data are consistent with Arrdc2 contributing to disuse atrophy, particularly in aged muscle.
Project description:Comprehensive analyses of mRNA expression were performed using three different cell populations isolated from skeletal muscle of young and aged mice to investigate age-related changes of each cell population.