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Abstract
Stem cell therapies are under development to treat a wide range of debilitating diseases, but their widespread translation depends on the ability to manufacture clinically effective cell products through bioprocesses that are controllable, scalable, and economical. Synthetic biomaterials may be uniquely enabling in the production of stem cell therapies, as they can be designed to precisely control soluble and insoluble components of the in vitro stem cell microenvironment. In this thesis, we describe the development of synthetic biomaterial-based approaches to 1) Improve the efficiency of stem cell expansion and 2) Understand and manipulate culture parameters that influence stem cell phenotype and therapeutic function. In the first portion of this work, we describe a biomaterial strategy for stabilizing and delivering thermally labile growth factors for efficient, cost-effective expansion of human pluripotent stem cells (hPSCs). Specifically, we developed mineral-coated microparticles (MCMs) for sustained release of basic fibroblast growth factor (bFGF), a soluble factor critical for hPSC survival, proliferation, and pluripotency. We found that MCMs protected bFGF activity at physiological temperatures, resulting in four-fold higher retention in biological activity compared to free soluble bFGF. Optimizing the process for generating bFGF-MCMs and the dosing of bFGF-MCMs enabled long-term expansion of hPSCs (over 25 passages) in a pluripotent state while reducing the amount of bFGF required by greater than 80% compared to conventional culture strategies. For the second portion of this work, we developed a novel approach based on engineered labile culture substrates that enabled control over spatial and temporal dynamics of cell aggregation. We then applied this platform to understand how the method and kinetics of aggregation influenced the three-dimensional microenvironment within hPSC and mesenchymal stem/stromal cell (MSC) aggregates. We found that the kinetics of aggregation affected structural features including cell packing density, extracellular matrix deposition, and porosity within aggregates, which in turn had implications for the lineage-specific differentiation of hPSCs and the therapeutic function of MSCs. In summary, this thesis describes two synthetic biomaterial-based approaches to control soluble and insoluble aspects of the microenvironment during stem cell biomanufacturing. These studies highlight opportunities for biomaterials to facilitate translation of cell therapies by improving biomanufacturing processes and underscore the importance of understanding variables introduced by specific bioprocesses that may influence the ultimate potency of a cell therapy product.
