Lim Shiyin, Veres Joanna E, Almeida Eduardo A C, O'Connell Grace D
Department of Mechanical Engineering, University of California, Berkeley, California, United States of America.
Department of Bioengineering, University of California, Berkeley, California, United States of America.
PLoS One. 2025 May 13;20(5):e0301316. doi: 10.1371/journal.pone.0301316. eCollection 2025.
Rodents provide a useful analog for understanding the effects of spaceflight on the human body, offering opportunities for investigations into the relationship between microgravity and the musculoskeletal system. In particular, rodents have often been utilized to improve our understanding of the effects of spaceflight on the spine, including intervertebral disc and vertebral body health. However, there are a number of experimental factors that differ between existing works, including mission duration, animal housing, and anatomical location of interest, making it difficult to draw holistic conclusions. Additionally, the quadrupedal nature of the murine spine results in different biomechanical loading than in a bipedal organism. Thus, the objective of this study was to more fully define the bulk properties of the murine lumbar spine model after 28 days of spaceflight. Additionally, the proximal tibia was analyzed to provide insight into the skeletal site-specificity of gravitational unloading in space. Results indicated that the effects of spaceflight on vertebral body bone microarchitecture, intervertebral disc biochemistry, and intervertebral disc joint mechanics were statistically insignificant, while large and significant bone loss was observed in the proximal tibia of the same animals. We hypothesize that this may be due to site-specific loading changes in space. Specifically, vigorous ambulatory behaviors observed in this experiment after initial acclimation to spaceflight may increase axial load-bearing in the lumbar spine, while maintaining microgravity induced mechanical unloading in the tibia. In total, this work shows that the rodent spine, unlike the weight bearing tibia in the same mice, is not affected by gravitational unloading, suggesting the tissue degenerative effects of spaceflight are site- and load-specific and not systemic. This study also highlights the importance of considering experimental variables such as habitat acclimation, physical activity, and experiment duration as key factors in determining musculoskeletal and spine health outcomes during spaceflight.
啮齿动物为理解太空飞行对人体的影响提供了一个有用的类比模型，为研究微重力与肌肉骨骼系统之间的关系提供了机会。特别是，啮齿动物常被用于增进我们对太空飞行对脊柱影响的理解，包括椎间盘和椎体健康。然而，现有研究之间存在一些不同的实验因素，包括任务持续时间、动物饲养条件以及感兴趣的解剖位置，这使得难以得出全面的结论。此外，鼠类脊柱的四足特性导致其生物力学负荷与双足生物不同。因此，本研究的目的是更全面地确定太空飞行28天后小鼠腰椎模型的整体特性。此外，对近端胫骨进行分析，以深入了解太空失重状态下骨骼部位特异性的情况。结果表明，太空飞行对椎体骨微结构、椎间盘生物化学和椎间盘关节力学的影响在统计学上不显著，而在同一批动物的近端胫骨中观察到了大量且显著的骨质流失。我们推测这可能是由于太空中特定部位的负荷变化所致。具体而言，在本实验中，动物在最初适应太空飞行后观察到的剧烈行走行为可能会增加腰椎的轴向承重，同时在胫骨中维持微重力诱导的机械卸载。总体而言，这项研究表明，与同一小鼠中负重的胫骨不同，啮齿动物的脊柱不受失重的影响，这表明太空飞行对组织的退化作用是部位和负荷特异性的，而非全身性的。这项研究还强调了将栖息地适应、身体活动和实验持续时间等实验变量作为确定太空飞行期间肌肉骨骼和脊柱健康结果的关键因素的重要性。
