The Effect of Drag Force and Flow Rate on Mesenchymal Stem Cells in Packed-Bed Perfusion Bioreactor

Abstract

Packed-bed bioreactors provide larger surface area to volume ratio compared to the static culture on flasks. Therefore, these systems offer ideal production environment for large-scale culture of mesenchymal stem cells (MSCs), but the effect of fluid dynamics on the cell-behavior of MSCs is not fully elucidated. In this study, packed-bed perfusion reactor loaded with different size of polymethyl methacrylate carriers was used to apply different rates of shear stress and drug forces at constant flow rate. The cell viability, cell-expansion, apoptosis and protein secretion levels were analyzed for both unmodified and Vascular Endothelial Growth Factor-positive (VEGF +) MSCs. The superficial stress was estimated to between 0.21-0.25 N/m 2. The results showed that the shear stress reduced the VEGF secretion, and Caspase-3 was activated at high drag force, which cause the reduction of the cell numbers in the bioreactor. The reduction of cytoskeletal actin structures seemed to play the central role in this adverse effect of the non-planar shear stress. The expression reduction of VEGF might also have critical impacts on the tissue engineering applications, in which the formation of vascular construct is essential.