Figure 3.

3T3 fibroblasts were exposed to hypergravity in upright and upside down (usd) orientation. The total force per cell increases linearly with the number of deflected pillars of cells exposed to 1 g, 5.4 g, 10 g, and 19.5 g in an upright orientation (A). The ratio results in the traction force per deflected pillar for cells in upright (B) and usd orientation are shown (C). Dunn test of multiple comparisons after a significant Kruskal–Wallis test was performed (*p ≤ 0.05; **p ≤ 0.01; ***p ≤ 0.001). The traction force decreases from 1 g to 5.4 g and increases from 5.4 g to 19.5 g. This effect is independent from the cell-spreading area (D, upright orientation). Two of four randomly chosen data sets are shown. Each data point represents one analyzed cell. In the usd orientation, the biggest difference is between 5.4 g (E) and 19.5 g (F). Red depicts a pillar array, green depicts an actin filament, and blue depicts a nucleus. Compared with experiments under 1-g gravity conditions, cells in upright orientation exert less force on pillars at 5.4 g and 10 g (G). The gray range is the defined force limit for cell traction forces under 1-g conditions. This limit is set by the minimal and maximal averaged cell force of the six micropillars at 1 g in Fig. 2B. To see this figure in color, go online.