Induced pluripotent stem cells (iPSCs) have the potential to revolutionize healthcare by providing a personalized view to model disease, screen for new drugs, and regenerate tissues. Human iPS cells derived from blood, skin or urine can self-renew and be differentiated into virtually any cell type of the human body. Yet, to reach the full potential of iPSCs for a wide range of healthcare applications, especially those that are clinical, require the reliable production of large numbers of cell equivalents where the process does not influence downstream application. However, large cell numbers are also required for other (stem) cell types (e.g. mesenchymal, CAR-T) tissue engineering and therapeutic applications.
As an example, the number of cells required for heart failure treatment ranges from 106 to 109 cells. The most widely used culture strategies involve 2D methods that need large surfaces (1015 cells can be grown on ≈106 m2) and often use animal-derived products (e.g. Matrigel), proving challenging for their eventual manufacture at scale and later commercialization. Stirred suspension bioreactors (SSBs) are a highly appealing tool to overcome the limitations of 2D culture dishes for the expansion and directed differentiation of iPSCs. These systems facilitate large-scale expansion due to the effective space utilization rate resulting in yields of 106–107 mammalian cells/mL.
SSBs maintain a controlled, homogeneous culture environment with improved mass transfer (gas, nutrients, wastes) compared to static 2D culture further contributing to increased yields with the potential for online monitoring. A large range of cell types can benefit from this culture method to promote their expansion, but the method by which cells are deployed impacts the outcome. For example, iPSCs are suspended as aggregates or seeded on microcarriers composed of covalent polymers (e.g. dextran, polystyrene or PNIPAAm with biopolymers or ECM- proteins) based on irreversible bonding strategies in SBB culture, thus they can be exposed to high levels of fluid shear force, resulting in decreased cell viability and heterogeneous stem cell populations. Moreover, their bioreactor culture can generate large aggregates that promote increased cell death and spontaneous differentiation. However, other cell types, such as mesenchymal stem cells, can be cultured on the carrier surface, but the common materials are polymer microcarriers that do no reflect the mechanics of native tissues, nor can they be further adapted to do so.
Therefore, the objective of the project is to develop microparticles based on dynamic polymer materials, where the polymers are held together through dynamic and reversible bonding strategies, to enable the bioreactor culture of a range of cell types. We will use microfabrication methods to fabricate the particles. We will then explore bioreactor cell culture of mesenchymal and induced pluripotent stem cells on the formed microparticles where appropriate and their downstream processing. The final objective is to seek patent protection of the developed microparticle technologies in the ERC POC to open opportunities for their eventual commercialization.
