Model Systems to Analyze Cell:ECM and Cell:Cell Interactions

Studies of in vivo structures have been made possible through ex vivo cell culture systems. The long-standing, two-dimensional (2D) culture system that has allowed for cell functionality testing is being replaced by more advantageous three-dimensional (3D) systems which provide a more accurate physiological response (i.e. in vivo tissue formation, cellular differentiation, signal transduction, etc). One such 3D technology that allows for a widely tunable extracellular matrix (ECM) is a hydrogel. Collagen hydrogels have aided in the advancements of drug delivery, tissue engineering and repair, and understanding cellular processes such as cell migration and wound healing by providing an in vivo like milieu. Previously, our lab has observed a novel physiological response when cells were cultured on the surface of a Collagen I hydrogel. When place on the surface of the gel, the cells migrate to form a ring-like structure, we have termed a toroid. These toroids can be thought of as self-organizing tissue structures. However, toroids never form when cells are embedded within the collagen gel. Interestingly, the developing toroid mimics the shape of the well in which it is formed (i.e. circle, square, rectangle, etc).
Our recent studies expand on these findings by modeling cell-cell and cell-ECM interactions through the creation of single- and multi-cellular environments, as well as, quantifying the molecular mechanisms and remodeling occurring during toroid formation. To date, we have used 9 formulations of matrices and at least 10 cell types including several types of stem cells, cancer cells, cardiac fibroblasts (NHFs), and microvascular endothelial cells.
In summary, we have created a novel method to examine cellular differentiation which resembles processes found in development and disease. This method creates toroids which appear universal in creation with the caveat that cancer cells do not form toroids. Our system allows for tunability and reproducibility to investigate stem cell interactions and programming. By using this new culture model, we are uniquely positioned to explore (1) the understanding of early stem cell development, (2) the role of stem cell signaling pathways in toroid formation, and (3) a novel system suitable for creating disease treatments using stem cells.

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