Skeletal muscle unweighting: spaceflight and ground-based models

Abstract

Long-term manned spaceflight requires that flight crews be exposed to extended periods of unweighting of antigravity skeletal muscles. This exposure will result in adaptations in these muscles that have the potential to debilitate crew members on return to increased gravity environments. Therefore, the development of countermeasures to prevent these unwanted adaptations is an important requirement. The limited access to microgravity environments for the purpose of studying muscle adaptation and evaluating countermeasure programs has necessitated the use of ground-based models to conduct both basic and applied muscle physiology research. In this review, the published results from ground-based models of muscle unweighting are presented and compared with the results from related spaceflight research. The models of skeletal muscle unweighting with a sufficient body of literature included bed rest, cast immobilization, and unilateral lower limb suspension. Comparisons of changes in muscle strength and size between these models in the context of the limited results available from spaceflight suggest that each model may be useful for the investigation of certain aspects of the skeletal muscle unweighting that occur in microgravity.

Swimming Paramecium in magnetically simulated enhanced, reduced, and inverted gravity environments

“…This gravity simulation technique provides an alternative to currently used ''microgravity'' simulation techniques such as the rotating wall vessel (RWV) suspension technique. For example, it can also be used for investigations of 3D tissue engineering (34,35) and microgravity-induced changes in osteoblast growth (36), gene expression (37), skeletal muscle adaptation (38), and cell signaling (39) without the shear stress associated with the RWV. More generally, this noninvasive technique can be used to apply forces to the whole bodies of populations of cells, and thus, can serve as an alternative to ''point-like'' methods like atomic force microscopy (40) and magnetic tweezers (41) that apply local stresses to single cells.…”

Caspase-3 Regulation of Diaphragm Myonuclear Domain during Mechanical Ventilation–induced Atrophy

“…Furthermore, atrophy of MHC type I and MHC type IIa fibers corresponds with previous data demonstrating deficits in force production after 12 h of MV (4). This rapid rate of MVinduced diaphragmatic atrophy greatly exceeds the time course of atrophy observed in locomotor muscles during periods of disuse (43). For example, it would take at least 96 h to achieve the same level of atrophy in unloaded locomotor muscle as observed in the diaphragm after 12 h of MV (44).…”

Cellular mechanisms and local progenitor activation to regulate skeletal muscle mass

“…Skeletal muscle atrophy is characterized by a decrease in the size of pre-existing muscle fibers and is observed in many physiological and pathological conditions such as microgravity, critical illness, HIV, cancer cachexia and aging (Sever et al 1996;Miro et al 1997;Baracos 2001;Mitch and Price 2001;Singh et al 2001;Adams et al 2002Adams et al , 2003Di Giovanni et al 2004;Price et al 2006). It has been demonstrated that muscle atrophy is regulated by the crosstalking of well known pathways such as the calpain system, the lysosomal and the ubiquitin-proteasome pathways.…”