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A New Technique for Calculating Individual Dermal Fibroblast Contractile Forces Generated within Collagen-GAG Scaffolds

Brendan A. Harley ^*, Toby M. Freyman , Matthew Q. Wong ^* and Lorna J. Gibson 

^* Department of Mechanical Engineering, and Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts; and Boston Scientific, Natick, Massachusetts

Correspondence: Address reprint requests to Prof. L. J. Gibson, Tel.: 617-253-7107; E-mail: ljgibson{at}mit.edu.

Cell-mediated contraction plays a critical role in many physiological and pathological processes, notably organized contraction during wound healing. Implantation of an appropriately formulated (i.e., mean pore size, chemical composition, degradation rate) three-dimensional scaffold into an in vivo wound site effectively blocks the majority of organized wound contraction and results in induced regeneration rather than scar formation. Improved understanding of cell contraction within three-dimensional constructs therefore represents an important area of study in tissue engineering. Studies of cell contraction within three-dimensional constructs typically calculate an average contractile force from the gross deformation of a macroscopic substrate by a large cell population. In this study, cellular solids theory has been applied to conventional column buckling relationships to quantify the magnitude of individual cell contraction events within a three-dimensional, collagen-glycosaminoglycan scaffold. This new technique can be used for studying cell mechanics with a wide variety of porous scaffolds that resemble low-density, open-cell foams. It extends previous methods for analyzing cell buckling of two-dimensional substrates to three-dimensional constructs. From data available in the literature, the mean contractile force (F_c) generated by individual dermal fibroblasts within the collagen-glycosaminoglycan scaffold was calculated to range between 11 and 41 nN (F_c = 26 ± 13 nN, mean ± SD), with an upper bound of cell contractility estimated at 450 nN.