Quantification of proliferating (top) and dying (bottom) cell nuclei as well as of extra-cellular matrix density (center).

The images (top) depict cross-sections taken at different time points (T3 = 17d, T4 = 24d) of spheroids grown under different nutrient conditions ([G], [O2]). The colors indicate cell nuclei (blue), extra-cellular matrix (EMC) (green) and proliferation (red, left) or cell death (red, right). The curves (bottom) represent the radial profiles of the fraction of proliferating and dying cells, and the ECM density (intensity of ColIagen IV staining), inferred from averages over images from several spheroids growing under the same conditions. Bars indicate the standard deviation. With ECM density we denote the fluorescence value of Collagen IV, which varied in the interval [0, 1].