Date of Award

Spring 2019

Document Type

Open Access Thesis

Department

Biomedical Science

First Advisor

Jay D. Potts

Abstract

Evidence has arisen over the past several years that use of a three- dimensional (3D) culture system provides a distinct advantage over two- dimensional (2D) systems when cellular interactions are examined in a more natural environment. Changes in morphology, speed, and directionality of cells tested in both planar and 3D matrices have all demonstrated that using 3D system is advantageous. The changes to the cellular migration patterns were shown to be dependent on several variables within the surrounding substrate including cellular content, physical environment, and the matrix chemical milieu. We have taken advantage of using collagen hydrogels as a 3D scaffold for culturing cells for an extended period of time which has led to intriguing discoveries. One such discovery is that independent of cell type, cells which were placed on top of the hydrogel formed a ring structure we termed a toroid. These toroids take the shape of the well in which they are cultured. These toroidal cells appear long, thin, and are reminiscent of spokes on a wheel. However, when cells were mixed into the collagen hydrogel, a gel contraction was observed, but the cells remained homogenous throughout and no toroid was formed. In our studies, stem cells, lens epithelial cells, cardiac fibroblasts, microvascular endothelial cells, and cancer cells, were used individually or in combination. Cells were placed on the top of collagen hydrogels to observe their behavior in this new multicellular environment. We observed that when the different cell types were mixed together they formed a tighter toroid than normal. We also investigated the movement of cells during the toroid formation. To that end, β1 integrin, a member of the integrin family of membrane receptors important for cellular adhesion and recognition, was overexpressed in cells using a plasmid tagged with Green Fluorescent Protein (GFP). We were successful at expressing GFP tagged β1 integrin in cells and observing them in the collagen matrix. Our observations will contribute to the understanding of toroid formation and form the foundation of future computational modeling experiments examining cellular behaviors in response to different microenvironments.

Available for download on Monday, May 11, 2020

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