Figure 6. Results from long-term study.

Green-fluorescent protein (GFP) transfected dermal fibroblasts were statically seeded on silk fibers and grown to near confluency over 5 days prior to daily loading, which was applied every day thereafter until day 14. Confocal scans were taken daily of GFP-labeled cells (green) overlaid on silk fibers (red). Data shown for day 4, prior to stretch, and days 5, 11, and 14 following stretch. Images are shown as an average projection through a z-stack of 10μm sections (ranging from 300–450μm total depth) or below as an isometric 3D rendering of the same overlaid stacks. Live/dead staining for day 1 after seeding as comparison to non-labeled techniques. Scale bar = 300μm for projections and isometric views. For comparison, H&E staining shown for the terminal time point (14 days) in stretched (top) or static (bottom) conditions, scale bar = 100 μm. Black arrows point to silk fibers, white arrows point to cells. Mechanical test data (Stress vs. Stretch λ) corresponding to the 30^th loading curve of the cyclic stretch condition at each time point is shown.