Tissue engineering is a broad field geared toward improving or replacing biological material and comprises an immense collection of biological nuances to consider before strategies for clinical applications can be fully realized. Physical and biochemical signals are responsible for making up a cell\u27s microenvironment to guide morphology and function through cell-extracellular matrix signaling, cell-cell signaling, and soluble signaling. In particular, a deeper understanding of these cell-extra cellular matrix factors guiding stem cell adhesion, spreading, and differentiation is crucial to harnessing the potential to develop tissue for regenerative purposes. Mounting evidence suggests that physical cues are a key to understanding the potential of stem cells and significant efforts have been made to begin to parse the effects of cell-matrix interactions, yet little is known about the interplay in guiding cell signaling. The work presented here focuses on utilizing novel methods and materials to deconstruct individual cell-matrix interactions and gain a deeper understanding of the cooperative signaling behaviors for mesenchymal and embryonic stem cells.
Micropatterning studies utilizing dip pen nanolithography showed that physical signals in the microenvironment are vital to regulating mesenchymal stem cell adhesion. Matrix elasticity, ligand density, and adhesion topography were individually altered to observe single cell adhesion and spreading with matrix elasticity proving to regulate the adhesion and spreading of the cells. Photolithography based studies detailing cell spreading and matrix elasticity showed that when confining single cells into different geometric shapes and sizes on a matrix of tunable elasticity, cell shape and size ultimately became responsible for stem cell lineage commitment over matrix elasticity. Signaling pathway inhibition experiments utilizing nocodazole and Y-27632 suggested that RhoA is a key regulator of cell response to the cooperative effect of these tunable substrate variables. Embryonic stem cells were then micropatterned on novel UV/ozone modified polystyrene to detail and observe the physical effects on single embryonic stem cells. Micropatterned cells were able to be cultured for up to 48 hours on patterns while forming stress fibers and focal adhesions similar to somatic cells, thereby demonstrating their responsiveness to extracellular matrix cues while maintaining expression of pluripotency transcription factor Oct4. The results from this work validate the immense importance of physical signaling and the effects on mesenchymal and embryonic stem cells. By understanding the effects of physical signaling in conjunction with biochemical signaling in controlling cell spreading and lineage commitment, tissue engineering is able to draw one step closer to potential applications for repairing and replacing biological function
