Fig. 4

Mechanical stimulations of mesenchymal stromal cells-derived cartilage micropellets with different shapes of pressure signal. A Representative constant pressure signal with an amplitude of 3.5 kPa, square and sinusoidal pressure signals with an amplitude of 3.5 kPa and a frequency of 1 Hz that stimulated 21-day micropellets for 30 min. B Average diameter of micropellets studied in each group (n = 15 micropellets). C Average sinking of micropellets in their cones at the beginning (Initial) and end (Final) of 30 min stimulations depending on the shape of the pressure signal (n = 15 micropellets). D Average amplitude of the cyclic oscillations of the micropellet top and bottom ends depending on the shape of the pressure signal (n = 15 micropellets). E Fold change expression of SOX9, AGG and COL IIB in micropellets 3 h after stimulations with different pressure signals compared to non-stimulated control (NS) (n = 7–9 groups of 6 micropellets). Statistical analysis used one-way ANOVA test (*: p < 0.05, **: p < 0.01, ***: p < 0.001) or paired t test (###: p < 0.001, ####: p < 0.0001) for B, C and D. Statistical analysis used Wilcoxson signed rank test for E, and results are expressed as *: p < 0.05, **: p < 0.01