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Suspension cultures, in which human mesenchymal stem cells are cultivated on microcarriers in scalable single-use stirred bioreactor types, have been shown to be a promising alternative to planar flask cultures. However, stirred single-use bioreactors were originally developed for production processes with robust, permanent cell lines. Human mesenchymal stem cells are adherent primary cells and thus expanding them in such bioreactor systems imposes more stringent requirements on bioreactor systems. For low-serum conditions (5%) and different types of stirred single-use bioreactors, a suspension criteria-based approach for expanding human adipose tissue-derived mesenchymal stem cells (hASCs) from milliliter to pilot scale was successfully developed. For process scale-up, experimental and numerical investigations were performed to (i) predict optimum impeller speeds, (ii) determine the main engineering parameters (local shear stress, turbulent dissipation rate, Kolmogorov microscale), and (iii) verify suspension criteria NS1 and NS1u for rapid process transfer from 100 mL to 2 L and 35 L cultures. Using optimized medium-microcarrier combinations as well as NS1 and NS1u as scale-up factors, total hASC quantities between 3 × 107 (100 mL scale) and 1 × 1010 (35 L scale) were obtained. The cell quantities obtained are the highest reported to date for scalable single-use bioreactors under low-serum conditions. [ABSTRACT FROM AUTHOR]

The fluid flow and suspension characteristics inside small-scale, stirred, single-use bioreactors were investigated experimentally and by means of computational fluid dynamics. The required impeller speeds for homogenous suspension were determined for two microcarrier types. The shear stress level and turbulence distribution were predicted using a numerical model, which was verified by particle image velocimetry measurements. In subsequent cultivations of primary mesencymal adipose-derived stem cells, up to 31.4-fold expansion in cell number was achieved for serum concentrations as low as 5 %. [ABSTRACT FROM AUTHOR]

The article presents a study which discusses expansion of mesenchymal adipose-tissue derived stem cells in a single-use bioreactor under low-serum conditions. Topics discussed include increase in demand of human mesenchymal stem cells (hMSCs), use of preliminary tests in disposable-spinners to determine microcarrier (MC) types for serum reduced expansions, and flow cytometry tests revealing marker profiles following cell expansion and harvest.