Figure 2: Bioreactor concepts for the cocultivation of human mesenchymal stem/stromal cells (hMSCs) and beta cells. Beta cells and hMSCs can be cocultivated using either a direct mode or an indirect mode. Therefore, the cells can be present as aggregates or as encapsulated cells or attached to a carrier. In direct cocultivation, one medium and one aeration rate must be chosen for both cells, whereas indirect cocultivation allows each cell type to be supplied with a cell-specific medium and aeration rate. Abbreviations: STR: stirred tank reactor; FBR: fixed-bed reactor; FLBR: fluidized-bed reactor.