Project in brief
Skeletal muscle fibers are multinucleated cells, such that each nucleus supports a certain area of the cytoplasm and its organelles. Muscle fibers show hypertrophy with resistance training, and atrophy with disuse. Consequently, nuclear domains are altered depending on use, or lack thereof, e.g., satellite cells may provide new nuclei during fiber enlargement. This project will study the relationship between muscle fiber area and nuclei, satellite cell, and capillary number in 19 healthy men subjected to long-term simulated spaceflight. Nine of these subjects concurrently perform resistance exercise (Supine Squat and Calf Raise; 4 sets of 7 or 14, respectively, maximal coupled concentric and eccentric actions) using YoYo™ technology. Additionally, muscle samples are obtained pre and post 5 wk concurrent aerobic and resistance training, and resistance training only, using YoYo™ technology. In muscle biopsies obtained from m. vastus lateralis and/or m. soleus, serial cross-sections of samples are stained using enzyme- and immuno-histochemical methods, and analyzed with morphometric techniques. Muscle fiber types and capillary supply are assessed by means of ATPase activity, and staining for contractile myosin heavy chain isoforms. Basement fiber and capillary membranes are recognized with use of antibodies against laminin isoforms. Muscle fiber nuclei and satellite cell numbers are determined with use of multi-stained sections for laminin, N-CAM, Pax7 and Dapi using established techniques.
This study will disclose important morphological changes in skeletal muscle displaying different phenotypes following long-term simulated spaceflight. More importantly, the efficacy of a resistance exercise paradigm, designed for in-flight use, to counteract any effect is investigated. Information on the potential interference of aerobic exercise on concurrently performed resistance training adaptations on fiber size and satellite cell and capillary supply will aid in defining in- flight exercise prescriptions.
Our research group focuses on questions exploring mechanisms that regulate skeletal muscle size. More specifically studies are devoted to investigate the role of satellite cells in atrophy and hypertrophy of healthy, trained, diseased, disused or aged human skeletal muscle.
Research in the field
- Thornell LE. Sarcopenic obesity: satellite cells in the aging muscle. Curr Opin Clin Nutr Metab Care 14: 22-27, 2011.
- Lindström M, Pedrosa-Domellöf F, Thornell LE. Satellite cell heterogeneity with respect to expression of MyoD, myogenin, Dlk1 and c-Met in human skeletal muscle: application to a cohort of power lifters and sedentary men. Histochem Cell Biol 134: 371-385, 2010.
- Thornell LE, Lindstöm M, Renault V, Klein A, Mouly V, Ansved T, Butler-Browne G, Furling D. Satellite cell dysfunction contributes to the progressive muscle atrophy in myotonic dystrophy type 1. Neuropathol Appl Neurobiol 35: 603-613, 2009.
- Thornell L-E, Lindström M, Renault V, Mouly V, Butler-Browne GS. Satellite cells and training in the elderly. Scand J Med Sci Sports 13: 48-55, 2003.