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Fig. 3 | Stem Cell Research & Therapy

Fig. 3

From: Cell number in mesenchymal stem cell aggregates dictates cell stiffness and chondrogenesis

Fig. 3

Initial cell number does not impact oxygen and nutrition diffusion. Mathematical modeling for oxygen diffusion (a), glucose consumption (b), and TGF-b1 concentration (c) within pellets at day 7 of chondrogenic differentiation. Top left in ac: heatmap on slices through the spherical cell pellet at steady state (red, high concentration; blue, low concentration). Top right in ac: size comparison of the spherical aggregates for pellets with different initial cell number. Bottom left in ac: temporal concentration development in the center of a 500 k sphere. Steady state is reached within minutes; hence, a steady state analysis is justified. Bottom right in ac: concentration profiles across the spherical aggregates at steady state. d Ratio of cell number within the pellets normalized to initial cell number at different time points. Cells within pellets with lower initial cell number show higher proliferation potential, which is in agreement with the higher concentration of glucose within low-ACN pellets. Statistical analysis is based on a one-way ANOVA tool of OriginPro. Error bar represents standard deviation and different aggregates in one group are compared to 70 k in the same group (*p < 0.05, **p < 0.01, ***p < 0.001). (e) HIF-1α expression in pellets at day 7 of chondrogenic differentiation confirms the modeling data that cells in all conditions experience similar oxygen tension

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