In particular, it has been implicated as a mitogen, chemoattractant, an inducer of secretion of MMPs (Folkman, 2007) or even a survival factor (Leeet al, 2007). pairs under diverse conditions. We found that secreted collagen IV and soluble vascular endothelial growth factor have considerable guidance effect on ECs at the level of two interacting cells. Cell interaction rules extracted from the experiments of cell pairs were used to mathematically predict branching patterns characteristic of developing multicellular blood vessels. This integrative analysis method can be extended to other systems involving complex multicellular interactions. Keywords:angiogenesis, dielectrophoresis, endothelium, microfluidics, modelling == Introduction == Cellcell interactions leading to tissue development and remodeling frequently involve a small number of cells. This raises an important question of whether the information obtainedex vivoon the cell population level, that is, on the basis of averaged measurements of hundreds or even millions of cells, is relevant to understanding many of the physiological and pathophysiological processes. Although potentially more pertinent information could be obtained from single cell level analyses, the corresponding SD-208 experiments under the usual cell culture conditions are often hard to interpret due to variable initial population states and difficulties in dealing with poorly controlled cell distributions. Therefore, the development of tools allowing an increased degree of control of cell localization and the microenvironment holds great promise for extending our knowledge of a plethora of cell signalling events. Current microfabrication technologies offer a convenient means to precisely control cellcell and cellECM (extracellular matrix) interactions (El-Aliet al, 2006). For instance, single cells and cell pairs have been precisely patterned to study the effect of cellcell contact on cell proliferation (Nelson and Chen, 2002,2003) and the effects of the size and shape of ECM islands on cell fate (Chenet al, 1997). Controlled cell patterning on larger scales has been achieved by differential chemical treatment of the cell adhesion substratum (Kaneet al, 1999;Irimia and Karlsson, 2003;Suhet al, 2004;Veisehet al, 2004) or by using properties of SD-208 laminar flow (Takayamaet al, 1999;Khademhosseiniet al, 2004). Dielectrophoretic (DEP) force provides a particularly flexible and robust means for precise cell manipulation and patterning (Wanget al, 1997). When cells in a medium are exposed to an electric field, both the cells and the surrounding medium become electrically polarized. If the electric field is not uniform, the force acting on the part of the cell exposed to a stronger field intensity is expected to be greater than the force acting on the remainder of the cell. The unbalanced forces can drive the cell towards the maximum (positive DEP) or minimum (negative DEP) of the electric field depending on the properties of the cell and the surrounding medium. Both positive and negative DEP force can be used to manipulate cells (Voldmanet al, 2001;Nelson and Chen, 2003;Greyet al, 2004;Linet al, 2006). For instance, thousands of single cells in a single microfabricated device could be precisely patterned using an electrode array generating positive DEP force on the basis of points-to-lid’ geometry (Grayet al, 2004). Microfabricated devices can be used to precisely define an extracellular chemical microenvironment with high temporal and spatial resolution (El-Aliet al, 2006;Melin and Quake, 2007). For example, taking advantage of the fact that flows in microchannel networks are laminar, one can generate a precisely defined chemical gradient and temperature steps for cell stimulation (Lucchettaet al, 2005;Weibel and Whitesides, 2006;Paliwalet al, 2007). Unfortunately, active cell patterning is rarely combined with the continuous medium control afforded by the SD-208 microfabricated devices, limiting one’s ability to precisely set both the initial experimental conditions and the cell microenvironment in the ensuing experimentation. One research area of cell biology that can especially benefit from the simultaneous control of the initial cell positions and cell medium during Rabbit Polyclonal to GPR25 experimentation is the analysis of endothelial cell (EC) biology in the context of formation of new blood vessels. The corresponding processes of angiogenesis and vasculogenesis are among the most heavily investigated due to SD-208 their importance in development, tissue repair and tumourigenesis. Among many factors regulating angio- and vasculogenesis, vascular endothelial growth factor (VEGF) and proteins of the ECM appear to have especially prominent functions (Ferrara, 2004;Adams and Alitalo, 2007). Although the VEGF family includes many members, for convenience, the initially identified VEGF (VEGF-A) is still frequently referred to simply as VEGF (the convention also followed in this study). VEGF binds to several receptors: VEGFR-1, -2, -3 and neuropilin. Binding of VEGF to VEGFR-2 promotes survival and migration of ECs and secretion of matrix metalloproteinases (MMPs), and mediates the permeability of blood vessels (Matsumoto and Claesson-Welsh, 2001). Disruption of VEGF-mediated signal transduction can lead to the arrest of angiogenesis, making VEGF inhibitors promising candidates for cancer therapy (Ferrara, 2004;Herbst and Sandler, 2004). ECM can also contribute to the formation of new vessels by.