Fig. 3. a. Percentage of FBs and CMs in 2D and 3D culture systems. In both cases, no statistical significance was found with the nominal values of 80% CM and 20% FBs, respectively. n = 5 images belonging to N = 3 biologically independent samples were used for 3D quantifications and n = 6 images belonging to N = 3 biologically independent samples were used for 2D quantifications. A preliminary assessment where the considered populations were composed of either CMs or FBs was made (Fig. S5a†). At day 0, vimentin positivity was used to distinguish between cellular populations. Vimentin positive cells were considered to be FBs, and vimentin negative cells to be CMs (Fig. S5b†). b. Quantification of population percentages at day 5. Percentages of CMs and FBs were quantified after 5 days of culture and compared to the expected nominal values of the cocultures indicated in the graphs' titles. At least n = 5 images belonging to N = 3 biologically independent samples were considered in quantifications. At day 5, cTROP expressing cells were considered as CMs, and cells negative for cTROP were considered as FBs (Fig. S5c†). One sample t-test or Wilcoxon signed rank test were adopted to assess differences between a sample population, Gaussian or not respectively, and a theorical value. Statistical significance was indicated by *p < 0.05, **p < 0.01, ***p < 0.001 and ****p < 0.0001.