Adequate mechanical stimulation is essential for cellular health and tissue maintenance, including articular cartilage, which lines the articulating bones in joints. Chondrocytes, which are the sole cells found in articular cartilage, are responsible for matrix synthesis, maintenance and degradation. It is generally believed that chondrocytes require mechanical stimuli through daily physical activity for adequate cartilage homeostasis. However, to date, the molecular mechanisms of cellular force sensing (mechanotransduction) are not fully understood. Among other mechanisms, the cytoskeleton is thought to play a key role. Despite that gravity is a very small force at the cellular level, cytoskeletal adaptations have been observed under altered gravity conditions of a parabolic flight in multiple cell types. In this study, we developed a novel hardware which allowed to chemically fix primary bovine chondrocytes at 7 time points over the course of a 31-parabola flight. The samples were subsequently stained for the microtubules and vimentin network and microscopic images were acquired. The images showed a large heterogeneity among the cells in morphology as well as in the structure of both networks. In all, no changes or adaptions in cytoskeleton structure could be detected over the course of the parabolic flight.

充分的机械刺激对于细胞健康和组织维护至关重要，包括关节软骨在关节中排列的关节软骨。软骨细胞是在关节软骨中发现的唯一细胞，负责基质的合成，维持和降解。通常认为，软骨细胞需要通过日常体育活动来进行机械刺激，以实现足够的软骨稳态。然而，迄今为止，细胞力感测（机械转导）的分子机理尚未完全被理解。在其他机制中，细胞骨架被认为发挥关键作用。尽管重力在细胞水平上是很小的力，但是在多种细胞类型中，在抛物线飞行的重力改变的条件下，已经观察到细胞骨架的适应性。在这个研究中，我们开发了一种新型硬件，可以在31抛物线飞行过程中的7个时间点化学固定原代牛软骨细胞。随后对样品进行微管和波形蛋白网络染色，并获得显微图像。图像在细胞形态和两个网络的结构中均显示出很大的异质性。总之，在抛物线飞行过程中，未检测到细胞骨架结构的变化或适应。