Investigation Of The Interactions That Guide Vasculogenesis And Angiogenesis In Three Dimensional Environments
Tissues require that their cellular components interact to gain functional structure and to survive. Fully dissecting the myriad signals experienced by individual cells in the microenvironment in vivo is an ongoing research challenge. Elucidating the guiding mechanisms for cell communication may enable the rational design and manipulation of living systems on the tissue scale. In the context of tissue engineering, particular interest is allocated to the control of the cell-microenvironment interactions to build healthy thick implantable tissues. During vasculogenesis - the self-organization of vascular networks - individual cells undergo morphogenesis and assemble interconnected networks of capillaries formed of endothelial cells (EC). In addition, this primitive network sprouts new vessels and further remodels (angiogenesis) resulting in a hierarchical vascular structure in warm blooded organisms. The self-organizing, self-remodeling, nature of vascular morphogenesis makes it a suitable platform to study the relative importance of different fundamental mechanisms of communication between cells. Two schools of thought have emerged regarding the fundamental guidance mechanisms in vascular morphogenesis: chemical soluble signaling and mechanical signaling. However, the systems used in the studies associated with these propositions have limited relevance as they do not recapitulate physiological conditions for important cellular events that take place during in vivo vascular morphogenesis. In this sense, we argue that progress on the outstanding questions requires new approaches and tools. In this work, I have studied the behavior of individual cells during vasculogenesis in a 3D collagen environment, as well as the characteristics of multi-cellular lumenal invasions from a monolayer of ECs on a collagen scaffold during angiogenesis. The hypothetical framework is based on the reported ability of ECs to generate both chemical and mechanical signals and our methods exploit the random placement of cells as well as the structural heterogeneity of the culture systems developed. I then extend my efforts toward an application of directed vascular growth in scaffolds for tissue engineering. One of the most challenging limitations in tissue engineering to date is the proper oxygenation and nourishment of the thick tissues of interest. Specifically, growing prevascularized tissues requires fluid access to capillary-sized vessels whose inlets are not spatially distributed in a controllable fashion. I identified and exploited the interactions of ECs undergoing vasculogenesis with lumenized angiogenic invasions in a microfluidic setup. I report that this approach produces capillaries with continuous connections (anastomosis) between an EC-lined channel (which can be connected to a flow source) and capillary vessels within a tissue, providing extended access for nourishment into the bulk of a tissue culture.
In Vitro 3D Tissue Engineering; Angiogenesis; Vasculogenesis
Stroock, Abraham Duncan
Olbricht, William Lee; King, Cynthia A.
Ph. D., Chemical Engineering
Doctor of Philosophy
dissertation or thesis