Growth plate chondrocyte deformation in situ and a biphasic inclusion model for cells within hydrated soft tissues

This dissertation addresses some fundamental aspects of mechanical stimulation of the chondrocytes within the growth plate. The motivation of these studies is to better understand the mechanical mechanisms involved in the autoregulation and functional adaptation of soft tissues. The ultimate goal of this basic science research is to provide a basis for tissue modulation and tissue engineering through mechanical stimulation and manipulation.;The intrinsic biphasic material properties of live growth plate tissue were determined from in vitro experiments on growth plate explants in a bovine animal model. The cellularity of the growth plate was then used to investigate the mechanical coupling of the chondrocytes with their extracellular matrix. Specifically, the mechanical contribution of the chondrocytes' cytoskeleton was established by testing explants after inhibiting the polymerization of the actin filament network with cytochalasin-D.;A new quantitative technique utilizing laser scanning optical microscopy was developed for determining the deformation of living cells in growth plate as the tissue is deformed. A study monitoring the deformation of growth plate chondrocytes in situ provided information regarding the relative mechanical properties of the chondrocytes in the different histological zones of the growth plate and their surrounding extracellular matrix.;Finally, a model was developed in order to determine the mechanical environment of cells within hydrated soft tissues. The model treats the chondrocytes as mechanical inclusions within the extracellular matrix with the cell and extracellular matrix modeled as biphasic materials with distinct material properties. The solution was applied to confined compression, a standard explant loading configuration. Specific mechanical perturbations that may be involved in the process of mechanical signal transduction were addressed (e.g., flow fields, membrane stretch, pressure and volume change).