Simulation of Angiogenesis in Three Dimensions: Development of the Retinal Circulation.

A theoretical model is used to describe the three-dimensional development of the retinal circulation in the human eye, which occurs after the initial spread of vasculature across the inner surface of the retina. In the model, random sprouting angiogenesis is driven by a growth factor that is produced in tissue at a rate dependent on oxygen level and diffuses to existing vessels. Vessel sprouts connect to form pathways for blood flow and undergo remodeling and pruning.

Simulation of angiogenesis in three dimensions: Application to cerebral cortex.

The vasculature is a dynamic structure, growing and regressing in response to embryonic development, growth, changing physiological demands, wound healing, tumor growth and other stimuli. At the microvascular level, network geometry is not predetermined, but emerges as a result of biological responses of each vessel to the stimuli that it receives. These responses may be summarized as angiogenesis, remodeling and pruning.

Angiogenesis: an adaptive dynamic biological patterning problem.

Formation of functionally adequate vascular networks by angiogenesis presents a problem in biological patterning. Generated without predetermined spatial patterns, networks must develop hierarchical tree-like structures for efficient convective transport over large distances, combined with dense space-filling meshes for short diffusion distances to every point in the tissue. Moreover, networks must be capable of restructuring in response to changing functional demands without interruption of blood flow.

Simulated two-dimensional red blood cell motion, deformation, and partitioning in microvessel bifurcations.

Movement, deformation, and partitioning of mammalian red blood cells (RBCs) in diverging microvessel bifurcations are simulated using a two-dimensional, flexible-particle model. A set of viscoelastic elements represents the RBC membrane and the cytoplasm. Motion of isolated cells is considered, neglecting cell-to-cell interactions.

Effects of pulsation frequency and endothelial integrity on enhanced arterial transmural filtration produced by pulsatile pressure.

The role of the endothelium in regulating transmural fluid filtration into the artery wall under pulsatile pressure and the effects of changes in pulsatile frequency on filtration have received little attention. Previous experiments (Alberding JP, Baldwin AL, Barton JK, and Wiley E. Am J Physiol Heart Circ Physiol 286: H1827-H1835, 2004) demonstrated significantly increased filtration after initial onset of pulsatile pressure compared with that predicted by using parameters measured under steady pressure.

Onset of pulsatile pressure causes transiently increased filtration through artery wall.

Convective fluid motion through artery walls aids in the transvascular transport of macromolecules. Although many measurements of convective filtration have been reported, they were all obtained under constant transmural pressure. However, arterial pressure in vivo is pulsatile.