Astronauts are exposed to harsh conditions, including cosmic radiation and microgravity. Spaceflight elongates human telomeres in peripheral blood, which shorten upon return to Earth and approach baseline levels during postflight recovery. Astronauts also encounter muscle atrophy, losing up to 20% loss of muscle mass on spaceflights. Telomere length changes in muscle cells of astronauts remain unexplored. This study investigates telomere alterations in grounded mice experiencing radiation exposure and muscle atrophy, via a hindlimb unloading spaceflight mimicking model. We find telomere lengthening is present in muscle stem cells and in myofiber nuclei, but not in muscle-resident endothelial cells. We further assessed telomere length in the model following hindlimb unloading recovery. We find that telomere length failed to return to baseline values. Our results suggest a role for telomeres in muscle acclimatization, which is relevant for the well-being of astronauts in space, and upon their return to Earth.

宇航员暴露在恶劣的条件下，包括宇宙辐射和微重力。太空飞行延长了外周血液中的人类端粒，这些端粒在返回地球后会缩短，并在飞行后恢复期间接近基线水平。宇航员还会遭遇肌肉萎缩，在太空飞行中肌肉质量损失高达 20%。宇航员肌肉细胞端粒长度的变化仍未被探索。这项研究通过模拟后肢卸载太空飞行模型，研究了经历辐射暴露和肌肉萎缩的接地小鼠的端粒变化。我们发现端粒延长存在于肌肉干细胞和肌纤维核中，但不存在于肌肉驻留内皮细胞中。我们进一步评估了后肢卸载恢复后模型中的端粒长度。我们发现端粒长度未能恢复到基线值。我们的结果表明端粒在肌肉适应中发挥作用，这与宇航员在太空中以及返回地球后的福祉相关。