Project Summary / Abstract Angiogenesis – the growth of new blood vessels from an existing vasculature – is an essential process that takes place in disease such as tumor metastasis, ordinary physiological functions such as wound healing, and tissue engineering research for efficient transport of nutrients. The technological needs of modern medicine require manipulation of the microvasculature to inhibit or promote angiogenesis, but we cannot achieve this goal yet as our understanding of angiogenesis does not explain vascular guidance across tissue compartments. Although significant advances have been made in the characterization of molecules, pathways, and reactions, the process by which growing neovessels navigate complex tissue structures is poorly understood. Our driving hypothesis is that biophysical signals originating from neovessel interaction with the surrounding matrix, are sufficient to deter directed neovessel growth. Additionally, we also hypothesize that the integration of biophysical signals along with biochemical cues lead to unique vessel behavior, and this integration process is highly nonlinear. To address the problem of angiogenic guidance across tissue structure, a collagen-based organ culture of angiogenesis is used to mimic extracellular boundaries, coupled with an imaging pipeline to record time-dependent phenomena, and a computational model for further testing of proposed mechanisms. In Aim 1, we will examine extracellular matrix structural characteristics that modulate neovessel growth across a boundary. Quantitative 4D microscopy will be used to measure collagen fiber orientations and density simultaneously with neovessel growth past the boundary. Computational modelling based on proposed mechanisms of guidance will be conducted and compared with experimental results to further test our hypothesis. In Aim 2, macrophages will be added to the cultures at different positions to study their modulation of angiogenesis in conjunction with biophysical mechanisms from Aim 1. The addition of these cells advances our culture system closer to in vivo angiogenesis, and helps elucidate further mechanisms of angiogenic control. Quantitative 4D microscopy will be used to measure extracellular structural parameters, neovessel growth, and macrophage position and migration. The proposed mechanisms of neovessel migration will be further tested using computational modelling to determine the effect of macrophages vascular invasion within our mechanistic understanding. Together, these studies will characterize the relationship between growing blood vessels and their surrounding environment along with modulation by stromal macrophages. This research will provide new insight to angiogenic mechanisms driving guided neovessel growth and provide new research avenues to further understand angiogenesis. 1