Fig. 2

Mechanical stimulations of mesenchymal stromal cells-derived cartilage micropellets with square pressure signals. A Representative square-wave pressure signal generated by the device. B Experimental design to study the impact of mechanical stimulations with different pressure signal parameters on gene expression in micropellets. C Fold change expression of SOX9, aggrecan (AGG) and type IIB collagen (COL IIB) transcripts in micropellets after 21 days of differentiation compared to day 1 (n = 13 groups of 6 micropellets). D Fold change expression of SOX9, AGG and COL IIB in micropellets after stimulations with different durations (upper panel), frequencies (middle panel) and amplitudes (lower panel) compared to non-stimulated control (NS), at day 21 (n = 4–9 groups of 6 micropellets). E Histological staining of proteoglycans by Safranin O and fast green counterstaining in 21-day micropellets depending on pressure amplitude. Statistical analysis used Wilcoxson signed rank test, and results are expressed as *: p < 0.05, ****: p < 0.0001