Controlling the mechanical properties of three-dimensional matrices via non-enzymatic collagen glycation

Abstract

The mechanical properties of the extracellular matrix play an important role in maintaining cellular function and overall tissue homeostasis. Recently, a number of hydrogel systems have been developed to investigate the role of matrix mechanics in mediating cell behavior within three-dimensional environments. However, many of the techniques used to modify the stiffness of the matrix also alter properties that are important to cellular function including matrix density, porosity and binding site frequency, or rely on amorphous synthetic materials. In a recent publication, we described the fabrication, characterization and utilization of collagen gels that have been non-enzymatically glycated in their unpolymerized form to produce matrices of varying stiffness. Using these scaffolds, we showed that the mechanical properties of the resulting collagen gels could be increased 3-fold without significantly altering the collagen fiber architecture. Using these matrices, we found that endothelial cell spreading and outgrowth from multi-cellular spheroids changes as a function of the stiffness of the matrix. Our results demonstrate that non-enzymatic collagen glycation is a tractable technique that can be used to study the role of 3D stiffness in mediating cellular function. This commentary will review some of the current methods that are being used to modulate matrix mechanics and discuss how our recent work using non-enzymatic collagen glycation can contribute to this field.

Keywords: angiogenesis; biomaterials; endothelial cell; glycation; matrix stiffness; three-dimensional.

Figure 1. Methods commonly used to modulate matrix stiffness. The mechanical properties of both synthetic and natural matrices are commonly tuned by altering the number of cross-links and/or the density of the scaffold. Mixed matrices comprised of both synthetic and natural materials can be used to create hybrid in vitro environments that mimic the properties of in vivo tissues.

Figure 2. Bovine aortic endothelial cells embedded within glycated collagen gels. Collagen solutions that had been glycated with 0, 50 or 100 mM ribose were neutralized, mixed with endothelial cells and allowed to polymerize. Cells were allowed to spread for 24 h and then were fixed and stained for actin (green) and DAPI (blue). Cells and the surrounding collagen were imaged using confocal microscopy. Scale is 20 μm.