## Appendix A PLGA: Poly(lactic-co-glycolic acid)
This makes it difficult to determine with certainty the total surface available for growing cells. Consequently, finding the optimal seeding density in these cases is more based on empirical tests than on precise calculations. Growth kinetics of ASC52 telo on _BR44_ is similar to other MCs culture, consisting of slow initial growth, followed by an exponential growth phase until cells reach a stationary level after, determined by the surface/nutrient availability, after a week [70]. In our previous paper, we study primary human ASCs growth parameters in _UrSuppe_ on commercial MC. We observed that the number of cells fluctuated around a specific maximum value determined by the system [37]. One of the most important preliminary results obtained after these experiments is that the undifferentiated state of the ASC52 telo cells is very well preserved when growing on biodegradable MC. This is independent of the cell culture system since this was observed both in static and dynamic (stirred flask) conditions. In static or dynamic conditions, we found that cells grown in 3D on _BR44_ showed a better \"gene expression profile for stemness\" than the same cells cultured on traditional 2D surfaces(as shown in Figure 10B). We also observed that the secretion profile of ASC52 telo cells depends on the cultivation system (standard static 2D vs. dynamic 3D) and the MC type on which the cells grow (_BR44_ vs. ProNectin-F, see Table 5, Figure 11, and Figure S14). These observation are in accordance to previous papers that indicates that 3D environment mimic the in vivo conditions and are able to better preserve stemmnes [71]. Interestingly, when these cells expand on MCs in a dynamic system, the adipokines profile is less complex. This could mean that the cells remain more immature, thus better preserving their stemness. This observation agrees with the results obtained by RT-qPCR. We also noted that the type of MC used to grow the cells also influences the type of metabolism adopted during the culture period. So, we concluded that although the system based on an agitated bioreactor, microcarrier, and a defined serum-free medium may seem very artificial, the cells like it and maintain the same or a superior undifferentiated status compared to cells grown in standard 2D conditions. We thought of explaining this phenomenon with the following hypothesis. Except for blood and endothelial cells, all the other cells are normally never in contact with serum. They are in contact with the interstitial fluid, which has a lower concentration of proteins than serum and is specific for each tissue or organ due to a unique composition of secreted polypeptides and metabolic molecules [12; 13]. Paradoxically, it is similar in composition to a serum-free medium, which is generally not as complex as serum and is specific to the cell type of interest. Furthermore, cells are organized in 3D structures, and they experience movements and hydrodynamic and shear stresses: Fluids flow through, contractions, movements, and motor activity are widespread actions in the animal kingdom. Thus, it may be possible that the conditions created in an agitated bioreactor somehow recreate the natural situation experienced by the cells in the body better than in a standard 2D cell culture vessel. In conclusion, _BR44_ is a suitable MC for the cultivation of ASC52 telo in a defined xeno- and serum-free medium. Regenerative applications require high biomass that should be obtained using a defined system. Now that we have suitable biodegradable MCs and a chemically defined medium for human ASCs, we are ready to check whether we can reproduce these results with primary human cells. Furthermore, the _UrSuppe_ medium could help study ex vivo the biology in healthy and dysfunctional states of adipocytes and their precursors in defined and controlled cell culture conditions.