Characterization and impact of the hydrodynamics on the performance of umbilical-cord derived stem cells culture in stirred tank bioreactors

Abstract : Mesenchymal stem cells (MSC) are becoming increasingly involved in the regenerative medicine field, particularly to treat diseases that are not effectively curable with the current therapies. Two scientific barriers are nevertheless responsible for MSC use and commercialization limitations. On one side, large amounts of cells are needed to reach the high cell dose requirements. On the other side, cells being the final product themselves, directly injected into the patient, their quality have to be controlled (stem cell phenotype, differentiation capability). MSC cultivation on microcarriers in a stirred bioreactor seems to meet these challenges. However, a precise knowledge about the impact of the technologies and the hydrodynamics generated, on the physiological cell response, is necessary to improve the scale-up of MSC cultures in bioreactors. In this context, present work is dedicated to the study of the impact of the agitation mode (orbital or mechanical) on the cell attachment, expansion and detachment on various microcarrier types, in the case of MSC derived from the Wharton’s jelly (WJ-MSC) of umbilical cords. To quantify more precisely cell distribution and expansion on microcarriers, an automatic and in situ counting method was developed, which need no detachment step. This allowed the identification of commercial microcarriers suitable for WJ-MSC cultures, which were then compared to home-made microcarriers, synthesized by a partner laboratory, in terms of cell attachment and expansion, and detachment efficiency. In parallel to these works, the impact of the impeller design on the microcarrier suspension in stirred tank bioreactors was investigated. Based on a dimensional analysis and CFD simulations, it resulted in the establishment of two models relating the minimal agitation rate to ensure all particle suspension (Njs) with the impeller geometrical characteristics (design, size, off-bottom clearance) and the material properties of both the solid and the liquid phases. CFD models validation allowed then to develop a strategy to optimize the geometrical configuration of an impeller, dedicated to MSC cultures on microcarriers in a minibioreactor. Parameters characterizing the hydromechanical stress encountered by the solid phase were wisely chosen and integrated into CFD simulations. Based on a design of experiments, and the hydrodynamics data recovered from simulations, response surfaces were built and a multiobjective optimization was achieved in order to determine the geometry minimizing the particle stress, and also by adhered cells. WJ-MSC cultures in minibioreactors equipped with impellers displaying various geometries were finally validated, with a preliminary comparison of the impact of these geometries on the cell expansion
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Submitted on : Tuesday, May 7, 2019 - 3:52:51 PM
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Céline Loubière. Characterization and impact of the hydrodynamics on the performance of umbilical-cord derived stem cells culture in stirred tank bioreactors. Chemical and Process Engineering. Université de Lorraine, 2018. English. ⟨NNT : 2018LORR0220⟩. ⟨tel-02122902⟩

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