Skeletal muscle culture under spaceflight conditions

Abstract

The response of intact skeletal muscle to spaceflight involves a complex interplay between muscle function, myofiber type, neuronal innervation, and various circulating factors that modulate muscle behavior and function. It is important to note that alterations in extrinsic (e.g., mechanical loading of the musculoskeletal system), systemic (e.g., neuromuscular activity, circulating factors), and intrinsic (e.g., myofiber tension, myofiber protein balance) factors all interact to drive the specific responses observed in intact skeletal muscle exposed to microgravity during spaceflight. As such, while tissue culture analogs are used to study the effects of microgravity exposure on skeletal muscle cells, any conclusions drawn from these studies must be interpreted with the understanding that such analogs only partially represent the conditions experienced by intact skeletal muscle in vivo during spaceflight. This chapter provides an overview of the various types of tissue culture models which have been used to investigate the cellular and biochemical responses of skeletal muscle cells to actual microgravity exposure or terrestrial analogs of spaceflight conditions. These experimental models have utilized individual muscle cells, multi-cellular myotubes, and/or more complex, 3-D organoid skeletal muscle tissue culture analogs as a means of understanding the effects of microgravity on intact skeletal muscle tissue in vivo. By cataloging these responses while manipulating specific experimental conditions in a defined fashion, skeletal muscle tissue culture analogs can be used to develop causal relationships between particular stimuli (or lack there-of) and specific cellular responses observed during spaceflight. In addition, the knowledge gained utilizing such microgravity tissue culture analogs has direct application in understanding the etiology of various terrestrial musculoskeletal disease states.