Micromechanics of fibroblast contraction of a collagen-GAG matrix.

The contractile force developed by fibroblasts has been studied by measuring the macroscopic contraction of porous collagen-GAG matrices over time. We have identified the microscopic deformations developed by individual fibroblasts which lead to the observed macroscopic matrix contraction. Observation of live cells attached to the matrix revealed that matrix deformation occurred as a result of cell elongation. The time dependence of the increase in average fibroblast aspect ratio over time corresponded with macroscopic matrix contraction, further linking cell elongation and matrix contraction. The time dependence of average fibroblast aspect ratio and macroscopic matrix contraction was found to be the result of the stochastic nature of cell elongation initiation and of the time required for cells to reach a final morphology (2-4 h). The proposed micromechanics associated with observed buckling or bending of individual struts of the matrix by cells may, in part, explain the observation of a force plateau during macroscopic contraction. These findings indicate that the macroscopic matrix contraction measured immediately following cell attachment is related to the extracellular force necessary to support cell elongation, and that macroscopic time dependence is not directly related to microscopic deformation events. Copyright 2001 Academic Press.