Biomechanics of fibroblast-compacted collagen gels investigated under fibrillar framework

Abstract

Collagen hydrogel spontaneously contracts as fibroblasts are embedded within, a phenomenon widely harnessed in the studies of wound healing process and the creation of engineered tissues. In this study, the mechanical behavior of the cell-collagen gels is distinguished into active contraction process and passive load-deformation process. To investigate the biomechanics in these processes, a fibrillar framework is constituted; which is composed of the single fibrillar force response, the fibrillar network model, and the effects of alterations to the fibrillar network. Quantitative and statistical analysis of these three physical aspects of the framework are conducted, which include the estimation of the number and states of the fibrillar constituents, the probability of the ratio of fibrillar end-to-end distance to the contour length, and the alteration of the statistical parameters for the fibrillar network due to deformation. Through these analyses and the regressions to experimental data, the following results and conclusions are achieved. 1) The traction force exerted by individual fibroblasts during the active contraction can be evaluated by a putative principle, the stationary state of the instantaneous Hamiltonian of the cellular mechanotransduction system; which underlies the cellular response to the change of its mechanical environment 2) The various nonlinear behaviors of the gels in the passive load-deformation process originate from the characteristics of the fibrillar network. These results and conclusions present the most updated understanding to this 3D tissue model.