Fibroblasts in three dimensional matrices: cell migration and matrix remodeling

Abstract

Fibroblast-collagen matrix culture has facilitated the analysis of cell physiology under conditions that more closely resemble an in vivo-like environment compared to conventional 2-dimensional (2D) cell culture. Furthermore, it has led to significant progress in understanding reciprocal and adaptive interactions between fibroblasts and the collagen matrix, which occur in tissue. Recent studies on fibroblasts in 3-dimensional (3D) collagen matrices have revealed the importance of biomechanical conditions in addition to biochemical cues for cell signaling and migration. Depending on the surrounding mechanical conditions, cells utilize specific cytoskeletal proteins to adapt to their environment. More specifically, cells utilize microtubule dependent dendritic extensions to provide mechanical structure for matrix contraction under a low cell-matrix tension state, whereas cells in a high cell-matrix tension state utilize conventional acto-myosin activity for matrix remodeling. Results of collagen matrix contraction and cell migration in a 3D collagen matrix revealed that the use of appropriate growth factors led to promigratory and procontractile activity for cultured fibroblasts. Finally, the relationship between cell migration and tractional force for matrix remodeling was discussed.

Figure 1

Comparison of in vitro collagen matrix remodeling. After one hour of collagen polymerization with fibroblasts, the matrices were either immediately released from the culture dish (floating matrix) or cultured under attached conditions (attached matrix). In the Restrained (stressed) matrix, isometric tension was developed overnight, after which the matrix was released to initiate remodeling.

Figure 2

Membrane ruffling of fibroblast in 3D collagen matrix. The dendritic extensions of fibroblasts in 3D collagen matrices expanded in response to PDGF and retracted in response to LPA stimulation (Upper panel). Membrane ruffling was induced at the margin of the membrane in both PDGF- and LPA-stimulated fibroblasts (Low panel), which provides mechanical activity for the floating matrix. Rho kinase and mDia interacted with PAK1 for PDGF and LPA-mediated matrix contraction, respectively. See Figure 3 and 10 in (Rhee and Grinnell, 2006) for more detail.

Figure 3

Different roles of microtubules in fibroblast spreading on collagen-coated coverslips compared to collagen matrices. The actin cytoskeleton was visualized and images by fluorescence microscopy. Fibroblasts cultured for 4 h on collagen-coated coverslips (2D) spread into an elongated, flattened morphology. Disrupting microtubules with nocodazole (+Noc) inhibited cell polarization but not spreading. Fibroblasts cultured inside of collagen matrices for 4 h (3D) spread by protrusion of dendritic extension. Dendritic extensions in 3D collagen matrices were not observed in cells that were cultured with Noc. See figure 1 in (Rhee et al., 2007) for more detail.