Figure 4. Early changes in collagen spatial organization.

(A) The fiber direction gradient increases from the initial time point, suggesting fibers closer to the cell structure become increasingly oriented perpendicular to the cell surface over time. Significant differences relative to the initial time point were only detected in 0% Matrigel at 9, 11, and 12 hrs (p = 0.0001). (B) The rate of fiber rotation over the first 12 hours of culture in regions 40 μm from the cell surface was significantly faster in 0% Matrigel compared to 50%. (C) No significant changes in the directional variance gradient were observed over the first 12 hours indicating a lack of local anisotropy developing within the fiber network at the initial stages following seeding. (D) The spatial gradient of fiber density significantly increased over time in all groups, indicating some level of cell-mediated gel compaction regardless of Matrigel composition. Data are represented as mean +/− SD.