Soft Matter and Complex Systems Seminar

The fundamental challenge of tissue engineering is to create a functional vascular network that provides oxygen and nutrients to cells. Effectively constructing such networks requires understanding the processes involved in vascular network formation and identifying the factors influencing its growth. From an experimental perspective, we focus on well-controlled systems consisting of individual plastic microbeads coated with endothelial cells or bead matrices, ie. groups of individual microbeads with adjustable spacing between them. The microbeads are placed in hydrogel, mimicking an extracellular matrix, supplemented with nutrients, fibroblasts, and vascular endothelial growth factors (VEGF) at controlled concentrations.

Numerical tools have been developed for image segmentation of microscopic images with the ability to characterize networks through numerous parameters. One notable observation is that the onset time, marked by the initial growth of capillaries from a microbead, gets shorter with higher concentrations of VEGF. Additionally, higher concentrations of VEGF result in more branched networks, although they do not significantly affect the speed of growth of individual sprouts. The mean bifurcation angle shows weak dependence on VEGF concentration, typically varying between 60 and 75 degrees. This suggests that the sprout tips tend to follow local VEGF gradients. At high VEGF concentrations, we observe exponential distributions of segment lengths, indicating stochastic branching. To simulate growth of capillary networks in vasculogenesis we began to work on a cellular Potts model, consisting off two key factors governing network formation: elastic interactions due to hydrogel deformation by endothelial cells and chemotaxis associated with the diffusion and reaction of VEGF proteins with endothelial cells.