The temporal and spatial dynamics of microscale collagen scaffold remodeling by smooth muscle cells.

Smooth muscle cells (SMCs) and collagen scaffolds are widely used in vascular tissue engineering but their interactions in remodeling at the microscale level remained unclear. We characterized microscale morphologic alterations of collagen remodeled by SMCs in six dimensions: three spatial, time, multichannel and multi-position dimensions. In live imaging assays, computer-assisted cell tracking showed locomotion characteristics of SMCs; reflection and fluorescent confocal microscopy and spatial reconstruction images of each time point showed detailed morphologic changes of collagen fibers and spatial collagen-SMC interactions. The density of the collagen around the SMCs was changed dynamically by the leading edges of the cells. The density of the collagen following 24h of cell-induced remodeling increased 51.61+/-9.73% compared to unremodeled collagen containing cells for 1h (P<0.0001, n=40) (NS vs. collagen without cells). Fast Fourier transform analysis showed that the collagen fibers' orientation changed from random (alignment index=0.047+/-0.029, n=40) after 1h into concordant with that of the SMCs (alignment index=0.379+/-0.098, P<0.0001, n=40) after 24h. Mosaic imaging extended the visual field from a single cell to a group of cells in one image without loss of optical resolution. Direct visualization of alignment of actin fibers and collagen fibers showed the molecular machinery of the process of scaffold remodeling. This is a new approach to better understanding the mechanism of scaffold remodeling and our techniques represent effective tools to investigate the interactions between cells and scaffold in detail at the microscale level.