Dynamic assessment of cell-matrix mechanical interactions in three-dimensional culture.

Cell-matrix mechanical interactions play a defining role in a range of biological processes such as developmental morphogenesis and wound healing. Despite current agreement that fibroblasts exert mechanical forces on the extracellular matrix (ECM) to promote structural organization of the collagen architecture, the underlying mechanisms of force generation and transduction to the ECM are not completely understood. Investigation of these processes has been limited, in part, by the technical challenges associated with simultaneous imaging of cell activity and fibrillar collagen organization. To overcome these limitations, we have developed an experimental model in which cells expressing proteins tagged with enhanced green fluorescent protein are plated inside fibrillar collagen matrices, and high magnification time-lapse differential interference contrast and fluorescent imaging is then performed. Using this system, focal adhesion movement and reorganization in isolated cells can be directly correlated with collagen matrix deformation and changes in the mechanical behavior of fibroblasts can be assessed over time.