Figure 1

Mechanical and biophysical interactions in the stem cell niche. The native microenvironment, or niche, in which a stem cell resides can be highly complex, consisting of various cell types, extracellular matrix (ECM) molecules, and growth factors. Proteoglycans and ECM proteins bind and immobilize otherwise soluble growth factors, providing functional sites for cell binding as well as mechanical stability of the space surrounding a stem cell in its niche. ECM fibers and neighboring niche cells provide mechanical support and stimuli (short red arrows) to influence stem cell fate. The degree of 'crosslinking' of the various ECM molecules also affects the pore size in the niche, dictating the rate of diffusion of soluble factors as well as the ability of niche cells to infiltrate nearby space. Finally, flow through local vasculature (long red arrows) mechanically shears endothelial and other cells (green), which may in turn affect nearby stem cells.