Vico L, Lafage-Proust M H, Alexandre C
LBTO Laboratoire de Biologie du Tissu Osseux, GIP Exercise, Faculté de Médecine, Saint Etienne, France.
Bone. 1998 May;22(5 Suppl):95S-100S. doi: 10.1016/s8756-3282(98)00017-9.
Spaceflight data obtained on bone cells, rodents, and humans are beginning to shed light on the importance of gravitational loading on the skeletal system. The space environment is a relevant model to explore the bone cell response to minimal strains. However, whether there is a direct effect of gravity on the cell rather than changes related to lack of convection forces in cell cultures performed in microgravity is unknown. In vitro studies carried out using osteoblastic cell cultures in space show changes in cell shape, suggesting that cell attachment structures as well as cytoskeleton reorganization might be involved. Valuable information is expected from in vitro models of an increase or decrease in mechanical stress in order to identify the different pathways of mechanoreception and mechanotransduction in the osteoblastic lineage. Results obtained from both humans and rodents after spaceflights indicated that bone mass changes are site specific rather than evenly distributed throughout the skeleton, thus emphasizing the need to perform measurements at different bone sites: weight- and non-weight-bearing bones, and cancellous and cortical envelopes. Bone mass measurements and biochemical parameters of bone remodeling are currently under evaluation in cosmonauts. Histomorphometric studies of bones from rats after space missions of various periods provided the time course of the cancellous bone cellular events: transient increase in resorption and sustained decrease in bone formation. The underlying bone loss occurred first in weight-bearing bones and later in less weight-bearing bones. During the postflight period, time required to recover the lost bone was greater than the mission length. Thus, the postflight period deserves more attention than it is currently receiving. On earth, the rat tail-suspension model is currently used to mimic spaceflight-induced bone loss. Data from the model confirmed the impairment of osteoblastic activity and showed an alteration in osteoblast recruitment with skeletal unloading. However, this model needs to be further validated.
在骨细胞、啮齿动物和人类身上获取的航天数据，正开始揭示重力负荷对骨骼系统的重要性。太空环境是探索骨细胞对微小应变反应的一个相关模型。然而，重力对细胞是否有直接影响，而非与微重力条件下细胞培养中缺乏对流力相关的变化，目前尚不清楚。在太空中使用成骨细胞培养进行的体外研究显示细胞形状发生了变化，这表明细胞附着结构以及细胞骨架重组可能参与其中。预计从机械应力增加或减少的体外模型中能获得有价值的信息，以便确定成骨细胞谱系中机械感受和机械转导的不同途径。人类和啮齿动物在航天后的结果表明，骨量变化是部位特异性的，而非均匀分布于整个骨骼，因此强调了在不同骨部位进行测量的必要性：承重和非承重骨，以及松质骨和皮质骨包膜。目前正在对宇航员的骨量测量和骨重塑的生化参数进行评估。对不同时期太空任务后大鼠骨骼的组织形态计量学研究提供了松质骨细胞事件的时间进程：吸收短暂增加，骨形成持续减少。潜在的骨质流失首先发生在承重骨，随后发生在承重较小的骨骼。在飞行后阶段，恢复流失骨质所需的时间比任务时长更长。因此，飞行后阶段值得比目前更多的关注。在地球上，目前使用大鼠尾部悬吊模型来模拟航天诱导的骨质流失。该模型的数据证实了成骨细胞活性受损，并显示骨骼卸载时成骨细胞募集发生改变。然而，这个模型需要进一步验证。
