The goal of this portion of the project was to synthetically differentiate stem cells into bone; this would act as the 'output' for our final system. Since stem cells can by tricky to genetically engineer, we chose to build our circuit in human endothelial kidney (HEK) cells. In the final system, HEK cells will secrete a diffusible morphogen to differentiate co-cultured stem cells. We used Bone Morphogenetic Protein 2 (BMP2) as our osteogenic signaling molecule; it is one of the central regulators of osteoblast differentiation in mammalian cells (1) and has been shown to induce transdifferentiation in multiple stem cell types (2, 3, 4). Here, we work with myoblastic progenitor (C2C12) and mesenchymal (C3HT101/2) stem cells, two cell lines which have been shown capable of osteoblast differentiation (5, 6).
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