No abstract

Our data show stage-specific remodeling of human dystrophin-deficient muscle, with inflammatory pathways predominating in the presymptomatic stages and acute activation of TGFbeta and failure of metabolic pathways later in the disease.

Disuse atrophy is a common clinical phenomenon that significantly impacts muscle function and activities of daily living. The purpose of this study was to implement genome-wide expression profiling to identify transcriptional pathways associated with muscle remodeling in a clinical model of disuse. Skeletal muscle biopsies were acquired from the medial gastrocnemius in patients with an ankle fracture and from healthy volunteers subjected to 4-11 days of cast immobilization. We identified 277 misregulated transcripts in immobilized muscles of patients, of which the majority were downregulated. The most broadly affected pathways were involved in energy metabolism, mitochondrial function, and cell cycle regulation. We also found decreased expression in genes encoding proteolytic proteins, calpain-3 and calpastatin, and members of the myostatin and IGF-I pathway. Only 26 genes showed increased expression in immobilized muscles, including apolipoprotein (APOD) and leptin receptor (LEPR). Upregulation of APOD (5.0-fold, P < 0.001) and LEPR (5.7-fold, P < 0.05) was confirmed by quantitative RT-PCR and immunohistochemistry. In addition, atrogin-1/MAFbx was found to be 2.4-fold upregulated (P < 0.005) by quantitative RT-PCR. Interestingly, 96% of the transcripts differentially regulated in immobilized limbs also showed the same trend of change in the contralateral legs of patients but not the contralateral legs of healthy volunteers. Information obtained in this study complements findings in animal models of disuse and provides important feedback for future clinical studies targeting the restoration of muscle function following limb disuse in humans.

Corticosteroids have been used for decades to modulate inflammation therapeutically, yet there is a paucity of data on their effects in humans. We examined the changes in cellular and molecular immune system parameters, or “immunome”, in healthy humans after systemic corticosteroid administration. We used multiplexed techniques to query the immunome in 20 volunteers at baseline, and after intravenous hydrocortisone (HC) administered at moderate (250 mg) and low (50 mg) doses, to provide insight into how corticosteroids exert their effects. We performed comprehensive phenotyping of 120 lymphocyte subsets by high dimensional flow cytometry, and observed a decline in circulating specific B and T cell subsets, which reached their nadir 4–8 hours after administration of HC. However, B and T cells rebounded above baseline 24 hours after HC infusion, while NK cell numbers remained stable. Whole transcriptome profiling revealed down regulation of NF-κB signaling, apoptosis, and cell death signaling transcripts that preceded lymphocyte population changes, with activation of NK cell and glucocorticoid receptor signaling transcripts. Our study is the first to systematically characterize the effects of corticosteroids on the human immunome, and we demonstrate that HC exerts differential effects on B and T lymphocytes and natural killer cells in humans.