A xeno-free microcarrier-based stirred culture system for the scalable expansion of human mesenchymal stem/stromal cells isolated from bone marrow and adipose tissue

Human mesenchymal stem/stromal cells (MSC) are promising candidates for cell-based therapies and the development of microcarrier-based cultures in scalable bioreactors with well-defined xenogeneic-free components represent important milestones towards the clinical-scale production of these cells. In this work, we optimized our previously developed xeno-free microcarrier-based system for the scalable expansion of human MSC isolated from bone marrow (BM MSC) and adipose-derived stem/stromal cells (ASC). By adapting the agitation/feeding protocol at the initial cell seeding/cultivation stage in spinner flasks, we were able to maximize cell expansion rate and final cell yield. Maximal cell densities of 3.6 x 10(5) and 1.9 x 10(5) cells/mL were obtained for BM MSC (0.60 +/- 0.04 day(-1)) and ASC (0.9 +/- 0.1 day(-1)) cultures, upon seven and eight days of cultivation, respectively. Ready-to-use microcarriers Synthemax (R) II and Enhanced Attachment (R) supported identical expansion performance of BM MSC, turning those effective alternatives to the precoated plastic microcarriers used in our xeno-free scalable culture system. Importantly, expanded MSC maintained their immunophenotype and multilineage differentiation potential. Moreover, secretome analysis suggested a priming effect of stirred culture conditions on cytokine production by MSC. This culture system yielded considerable final cell densities that can be scaled-up to controlled large-scale bioreactors allowing a more efficient, safe and cost-effective MSC production for clinical settings.