(789g) Stem Cell Response to Spatially and Temporally Displayed Surface Topography

Stem cells are highly sensitive to chemical, mechanical and topographical cues in their local microenvironment.  Cellular response to these factors include changes in cellular and nuclear morphology.  Topographical cues alone have been shown to strongly influence nuclear organization and alter cell alignment, cytoskeletal arrangement, motility, proliferation, and even gene regulation.  Despite these advances, topographic presentation in previous studies has been primarily static and thus poorly representative of dynamic biological processes such as during tissue development and disease. As one example, cellular alignment is a critical parameter in musculoskeletal myogenesis, and musculoskeletal disorders are often associated with abnormalities in the muscle structure alignment.  In this work, we used strain responsive wrinkling patterns on PDMS substrates to enable tunable dynamic changes in pattern size and shape, high replication fidelity and feature resolution (UVO), shape versatility and complete reversibility.  Lamellar wrinkling patterns were fabricated by uniaxially stretching PDMS sheets and exposing them to ultraviolet/ozone, which created a stiffer skin, leading to lamellar patterns.  These patterns completely disappeared when the substrate was stretched back to the initial strain.  We showed that hMSCs responded to pattern switching by altering their shape and alignment, leading to reversible changes in nuclear area, orientation angle and aspect ratio.  Pattern generation was controlled spatially by selectively exposing the PDMS surface to UVO through a mask.  Using this methodology, we reported novel spatial control of reversible cellular alignment.  We also reversibly controlled pattern orientation angle and pattern order by sequential biaxial stretching prior to UVO treatment, which allowed us to reversibly control cellular alignment angle and cellular order for the first time.