Vector field simulations of anisotropy gradients.

A-C. Top-down view of the initial fibril directions for each element. Directions were randomly sampled from the element’s collagen EFD. Local matrix alignment is indicated by ellipsoidal glyphs above each representative image with the color indicating the anisotropy (blue: low; red: high). D-F. Microvessels were seeded on the left end of a rectilinear domain. Growth was either simulated in a relatively isotropic matrix (baseline) or a matrix characterized by a positive or negative anisotropy gradient. Microvessels for all models failed to reach the far region on the right. EFD simulations, on the other hand, predicted vascularization of the far region for both gradient models. G. Differences were also observed for growth in the middle region. Here, only a negative gradient resulted in increased vascularization, differing from the EFD simulations where both gradients resulted in increased growth in the middle region. (*: pp (TIF)