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].上方图像展示了在不同营养条件（[G]、[O₂]）下培养的多细胞球体（spheroid）在两个时间节点（T3=17天、T4=24天）的横截面。图中色彩分别标记：细胞细胞核（蓝色）、细胞外基质（extracellular matrix，缩写EMC）（绿色），以及细胞增殖（左侧红色）或细胞死亡（右侧红色）。下方曲线为增殖细胞占比、死亡细胞占比以及细胞外基质密度（IV型胶原蛋白（Collagen IV）染色强度）的径向分布曲线，该曲线通过对同一培养条件下多个多细胞球体的图像取平均后推算得到。图中的误差棒代表标准差。此处所称的细胞外基质密度指的是IV型胶原蛋白的荧光强度值，其取值区间为[0, 1]。