Developing 3D tissue systems
The finals phase for creating cultured meat involves bringing all the research together to create large (>100µm in diameter) pieces of tissue that can be made of mass produced cells without the need of serum, where the scaffold is suitable for cells and humans. These cells would go onto mature into adult muscle tissue that has comparable taste, structure, and nutritional value to conventionally-grown meat. This is the step that integrates all the previous steps in the research process. There are several methods available to create large pieces of tissue and keeping in alive in culture (Cerino, 2015. Madden 2015, Miller 2012). This is however not enough, we will need incorporate adipose cells (Hsiao 2015), and exercise the muscle cell to gain protein content and improve and the structure of the tissue (Nikolić 2012, Mun 2013).
In 2012 Jordan S. Miller published a method to produce a vascular network into a hydrogel. By 3D printing a sacrificial filament network made of carbohydrate glass, a mold could be produced. When the lattice mold was encapsulated with a hydrogel-cell suspension the carbohydrate scaffold was dissolved using water which left smooth elliptical intervessel junctions that supported fluidic connection between adjoining vascular channels. These channels were seeded with endothelial cells (HUVECs) which resulted in the lining of the entire network. Next this network was perfused with human blood and was cultured for 9 days. Optical sections showed a higher concentration of cells compared to gels without channels (Miller 2012).
This technique could also be implemented for the production of in vitro meat, with some enhancements. For example an edible hydrogel should be used if the constructs are to be used for consumption, which should also be capable to undergo electrical stimulation for better distribution of the extra cellular matrix (ECM) (Rahimi 2012) and in vitro exercise to boost protein content of the cells (Nataša Nikolić 2012).
Besides satellite cells, adipose cells should be co-cultured to improve the experience to be on par with conventional meat. When using this system this becomes possible by mixing these cells with the satellite cells into the hydrogel. What the effect of the adipose cells is on the satellite cells is still a topic of research. When using a setup depicted in figure 8 the limitation of oxygen and nutrient diffusion could be overcome. Moreover, this system allows for a pulsating flow through the tissue, which mimics the normal physiological condition in the body. This has been shown to positively affect proliferation during culturing (Mun 2013).
Figure 9. Schematic drawing of in vitro beef culture system using a sacrificial blood vessel mold made from carbohydrate. Using this system allows for “large” 3D tissue production which is desirable when upscaling production.
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