To stick or not to stick: Investigating cell adhesion dynamics and cell function using nanometric topography.

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In organs and tissues of the human body, cells adhere to a complex scaffold-like protein mesh called the extracellular matrix (ECM). The ECM provides cells with many stimuli and signals that cells need to behave normally allowing tissues of the body to function. However, increasingly human cells contact artificial materials due to tissue damage and the use of biomaterials. Central in many bioengineering applications is the attachment of human cells to artificial materials, but the factors important in successful cell-material interactions are still not well understood, which limits the design of new functional biomaterials. Using techniques harnessed from the microelectronic industry, it became possible to produce structures with precisely defined surfaces for cell-biological studies, thus allowing the reaction of cells to defined topographic features to be observed. Our previous research described in the proposal has identified that the topography of a material can be altered to enhance cell attachment, movement and tissue development. When a cell attaches to a surface, it results in activation of important signaling molecules required by the cells to survive and function. Cells attach to surfaces through specialized sites called focal adhesions (FAs), and research is highlighting that these adhesions are very important sites in cells. FAs are not only responsible for relaying the attachment event to other areas within the cell, but they also mature to form fibrillar adhesions, which are sites where cells deposit and arrange the scaffold-like protein mesh (extracellular matrix). It is now known that not all cells possess the same ability to attach, and in the proposal we will compare two the response of two such cell types: dermal fibroblasts (skin) and gingival fibroblasts (gum tissue). Of particular relevance is that in healing of these tissues, gingival tissue heals without scar formation, but skin doesn’t. Despite decades of research, the mechanisms underlying these observations are still largely unknown, but altered adhesion is postulated to be important. Our aim in this proposal is to probe the differences in adhesion capacity of each cell type by altering the topography of the culture substrata at the nano- and micro-metric scale. Changes in substratum topography are a very powerful modulator of cell adhesion. Specifically we will: 1) quantify the influence of nanometric scale topographies on attachment, adhesion assembly and integrin recruitment in human gingival and dermal fibroblasts, and 2) assess how changes in focal and fibrillar adhesion formation by nanometric scale topographies alter intracellular signaling, proliferation, and gene expression in dermal and gingival fibroblasts. We anticipate that dermal and gingival fibroblasts will show significant differences in levels of adhesion to nanotopographies, which will result in altered patterns of signaling within the cells. Overall, we expect that topographies that increase gingival fibroblast adhesion will result in signaling patterns and gene expression associated with scarring and conversely, topographies which limit dermal fibroblast adhesion formation will induce a tissue remodeling phenotype. The results of the study will directly address how and cell adhesion turns external stimuli into signals that regulate cell behaviour, which will be important for all areas of cell biology. Furthermore, we anticipate that the information produced by our program could in the long term be used in cell and tissue engineering applications, where our lack of understanding of cell-material interactions are limiting the development of functional engineered tissue substitutes and the longevity of biomaterials.