Three dimensional micromechanical signaling between cells and their extracellular matrix

Alaina Michele Pizzo, Purdue University

Abstract

The next generation of therapeutic strategies to achieve improved tissue replacement and regeneration relies on the ability to mimic the extracellular matrix (ECM) component of native tissues. However, it is not known how cells sense, prioritize, and respond to the complex array of environmental cues at the cell-ECM interface. To address this gap in the knowledge, the focus of this work was on the biophysical signaling capacity of the ECM. The central hypothesis was that fundamental cell behaviors such as cell morphology, proliferation, cell-matrix adhesion formation, and matrix remodeling are regulated by microstructural composition and mechanical properties of the cell's local three-dimensional (3D) ECM environment. The tissue system for this study consisted of cells within 3D engineered ECMs prepared from type I collagen. The microstructural composition of the engineered ECMs was controlled by varying the polymerization conditions or by the addition of specific ECM molecules. To determine if the cell response to specific biophysical properties (e.g., microstructural composition and mechanical properties) of their 3D ECM is cell-type specific, both low-passage human dermal fibroblasts and coronary artery smooth muscle cells were compared. In order to visualize the dynamic events associated with cell-ECM interactions in 4D (x, y, and z, and time), confocal microscopy was used in a combined reflection-epifluorescence mode with a custom-built environmental chamber to maintain long-term tissue culture conditions. These confocal images provided the basis for quantification of 3D cell inorphometry, time- and spatial-dependent changes in the 3D local strain state of a cell and its ECM, and spatial distribution of β1 integrin (a cell-matrix adhesion molecule). Scanning electron microscopy was also used to verify that the addition of specific ECM molecules, such as type III collagen, affects the hierarchical assembly of engineered type I collagen ECMs. In general, it was found that specific changes in the 3D microstructural composition and mechanical properties of a cell's extracellular microenvironment affect fundamental cell behaviors. Results from this study are significant because they show that specific physical properties of a cell's ECM microenvironment contribute to tissue remodeling events in vivo and to the design and engineering of functional tissue replacements.

Degree

Ph.D.

Advisors

Voytik-Harbin, Purdue University.

Subject Area

Biomedical research|Mechanical engineering

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