Force-driven evolution of mesoscale structure in engineered 3D microtissues and the modulation of tissue stiffening

Force-driven evolution of mesoscale structure in engineered 3D microtissues and the modulation of tissue stiffening

Ruogang Zhao, Christopher S. Chen, Daniel H. Reich,Biomaterials, Vol. 35, Issue 19, June 2014, Pg 5056–5064

http://www.sciencedirect.com/science/article/pii/S0142961214001604

Abstract:

The complex structures of tissues determine their mechanical strength.
In engineered tissues formed through self-assembly in a mold,
artificially imposed boundary constraints have been found to induce
anisotropic clustering of the cells and the extracellular matrix in
local regions. To understand how such tissue remodeling at the
intermediate length-scale (mesoscale) affects tissue stiffening, we used
a novel microtissue mechanical testing system to manipulate the
remodeling of the tissue structures and to measure the subsequent
changes in tissue stiffness. Microtissues were formed through cell
driven self-assembly of collagen matrix in arrays of micro-patterned
wells, each containing two flexible micropillars that measured the
microtissues' contractile forces and elastic moduli via magnetic
actuation. We manipulated tissue remodeling by inducing myofibroblast
differentiation with TGF-β1, by varying the micropillar spring constants
or by blocking cell contractility with blebbistatin and collagen
cross-linking with BAPN. We showed that increased anisotropic compaction
of the collagen matrix, caused by increased micropillar spring constant
或升高细胞contraction force, contributed to tissue stiffening.
Conversely, collagen matrix and tissue stiffness were not affected by
inhibition of cell-generated contraction forces. Together, these
measurements showed that mesoscale tissue remodeling is an important
middle step linking tissue compaction forces and tissue stiffening.