Clinical-scale expansion of adipose-derived stromal cells starting from stromal vascular fraction in a single-use bioreactor: proof of concept for autologous applications.

Adipose-derived stromal cells (ASCs) are adult multipotent cells increasingly used for cell therapy due to their differentiation potential, their paracrine effect and their convenience. ASCs are currently selected from stromal vascular fractions (SVFs) of adipose tissue and expanded in 2D flasks following good manufacturing practices. This process is limited in surface area, labour-intensive and expensive, especially for autologous applications requiring selection and expansion steps for every patient. Closed and automated bioreactors offer an alternative for scalable and cost-effective production of ASCs. This study investigated a single-use stirred-tank bioreactor that can expand ASCs from SVFs on microcarriers. A preliminary microcarrier screening in static and spinner flask conditions was performed to evaluate the best candidate for adhesion, amplification and harvest. The selected microcarrier was used for process development in the bioreactor. The first experiments showed poor selectivity and growth of the ASCs from the SVF (n  =  2). The process was then adjusted by two means: (1) decreasing the platelet lysate in the medium for enhancing cell adherence; and (2) adding a shear protectant (Pluronic F68). Following these modifications, we demonstrated that the number of population doublings of ASCs from SVFs was not significantly different between the bioreactor and the 2D controls (n  =  3). In addition, the ASC characterization after culture showed that cells maintained their clonogenic potential, phenotype, differentiation potential and immunosuppressive capacities. This study provides the proof of concept that isolation and amplification of functional ASCs from SVFs can be performed in a stirred-tank bioreactor combined with microcarriers.