Calcium-dependent deceleration of the cell cycle in muscle cells by simulated microgravity.
Of all our mechanosensitive tissues, skeletal muscle is the most developmentally responsive to physical activity. Conversely, restricted mobility due to injury or disease results in muscle atrophy. Gravitational force is another form of mechanical input with profound developmental consequences. The mechanical unloading resulting from the reduced gravitational force experienced during spaceflight results in oxidative muscle loss. We examined the early stages of myogenesis under conditions of simulated microgravity (SM). C2C12 mouse myoblasts in SM proliferated more slowly (2.23× less) as a result of their being retained longer within the G2/M phase of the cell cycle (2.10× more) relative to control myoblasts at terrestrial gravity. Blocking calcium entry via TRP channels with SKF-96365 (10-20 μM) accumulated myoblasts within the G2/M phase of the cell cycle and retarded their proliferation. On the genetic level, SM resulted in the reduced expression of TRPC1 and IGF-1 isoforms, transcriptional events regulated by calcium downstream of mechanical input. A decrease in TRPC1-mediated calcium entry thus appears to be a pivotal event in the muscle atrophy brought on by gravitational mechanical unloading. Hence, relieving the constant force of gravity on cells might prove one valid experimental approach to expose the underlying mechanisms modulating mechanically regulated developmental programs.
Space Biology Group, ETH Zürich, Zürich, Switzerland.
Tatiana
T
Benavides Damm
Stéphane
S
Richard
Samuel
S
Tanner
Fabienne
F
Wyss
Marcel
M
Egli
Alfredo
A
Franco-Obregón
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology*; D049109:Cell Proliferation; D002478:Cells, Cultured; D007093:Imidazoles / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis; D051379:Mice; D009133:Muscular Atrophy / Q000503:physiopathology; D050052:TRPC Cation Channels / Q000096:biosynthesis / Q000502:physiology; D050051:Transient Receptor Potential Channels / Q000187:drug effects; D018474:Weightlessness Simulation
D007093:Imidazoles; D050052:TRPC Cation Channels; D050051:Transient Receptor Potential Channels; C519530:insulin-like growth factor-1, mouse; C096351:transient receptor potential cation channel, subfamily C, member 1; D007334:Insulin-Like Growth Factor I; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D002118:Calcium