3D microenvironments for cell expansion

Current challenge

Efficient systems for proliferation and high-density cell growth are essential for creating the biomass needed for the cultivated meat industry at an economically viable price and scale. Because many cell types used by the cultivated meat industry are anchorage-dependent, their growth requires a solid surface such as microcarriers or the use of cell aggregates. However, both of these approaches present challenges for scale-up and achieving high cell densities in stirred tank bioreactors. The presence of microcarriers can increase shear stress and damage, while aggregates must be carefully controlled to prevent overgrowth. Similarly, adapting cells to suspension growth comes with its own sets of challenges regarding mass transfer of oxygen and nutrients. Innovative, scalable solutions are therefore needed that can permit high-density cell growth in environments with minimized shear stress.

Proposed solution

The growth and differentiation of cells in 3D microenvironments offers several advantages over suspension-based bioreactors. First, cells are confined to microenvironments inside permeable biomaterials within 200µm of nutrient access. This prevents the possibility of necrotic cores forming, as in aggregate growth. Second, cell confinement and encapsulation protects them from exposure to shear stress. Therefore, media mixing can be performed more aggressively because it exerts minimal physical effect on the cells. Third, cells have been reported to achieve densities of up to 5×108 cells per milliliter, which is significantly higher than stirred-tank suspension systems or growth on microcarriers. Fourth, the creation of microenvironments using coaxial extrusion to produce tubular structures is scalable and can be performed using low-cost, food-safe biomaterials, including materials like alginate that are already being explored for use in scaffolding. Fifth, differentiation can occur within the same microenvironments and may be enhanced by 3D growth facilitating cell polarity, alignment, and other self-organization traits. The use of 3D microenvironments to culture cell types used in cultivated meat warrants further investigation.

Anticipated impact

The successful demonstration of 3D microenvironments for the cell types used in cultivated meat could fundamentally change the approach of the overall bioprocess, as proliferation and differentiation could occur in a single environment. Because of the inherently self-contained nature of cells grown within 3D microenvironments, it is theoretically possible that even the seed train scale-up process can be avoided or shortened, which could drastically shorten the overall production cycle and improve efficiencies.

Furthermore, fewer transitions for cells may also reduce shock and streamline the bioprocess overall. The possibility also exists for simplified creation of whole-tissue, structured products that can be constructed via additive manufacturing of the differentiated cells within the microenvironments themselves, rather than relying on cell-laden scaffolds. This would open up a whole new approach for the fabrication of complex, multi-cell-type tissues.