Cell–Matrix Entanglement and Mechanical Anchorage of Fibroblasts in Three-dimensional Collagen Matrices

Abstract

Fibroblast-3D collagen matrix culture provides a physiologically relevant model to study cell-matrix interactions. In tissues, fibroblasts are phagocytic cells, and in culture, they have been shown to ingest both fibronectin and collagencoated latex particles. Compared with cells on collagen-coated coverslips, phagocytosis of fibronectin-coated beads by fibroblasts in collagen matrices was found to be reduced. This decrease could not be explained by integrin reorganization, tight binding of fibronectin beads to the collagen matrix, or differences in overall bead binding to the cells. Rather, entanglement of cellular dendritic extensions with collagen fibrils seemed to interfere with the ability of the extensions to interact with the beads. Moreover, once these extensions became entangled in the matrix, cells developed an integrin-independent component of adhesion. We suggest that cell-matrix entanglement represents a novel mechanism of cell anchorage that uniquely depends on the three-dimensional character of the matrix. INTRODUCTIONCompared with collagen-coated material surfaces such as plastic or glass, fibroblasts exhibit unique features when they interact with three-dimensional collagen matrices (Cukierman et al., 2002;Grinnell, 2003). The stiffness of fibroblasts is similar to that of three-dimensional (3D) collagen fibrils in the matrix (Wakatsuki et al., 2000). As a result, the interaction between cells and the matrix can lead not only to changes in cell shape but also to matrix remodeling and contraction (Grinnell, 1994;Brown et al., 1998;Tranquillo, 1999;Petroll and Ma, 2003;Vanni et al., 2003;Wakatsuki and Elson, 2003). By contrast, the difference in stiffness between cells and rigid material surfaces such as glass and plastic is so great (Wakatsuki et al., 2000;Callister, 2001) that cell shape change predominates even if the material surface has been modified to make it somewhat flexible (Balaban et al., 2001;Beningo and Wang, 2002).Fibroblasts interact with and attach to collagen matrices primarily through integrin ␣2␤1 but also with other integrins, including ␣1␤1, ␣11␤1, and ␣v␤3 (Klein et al., 1991;Schiro et al., 1991;Carver et al., 1995;Cooke et al., 2000;Tiger et al., 2001;Jokinen et al., 2004). Attached cells, rather than forming flattened, lamellar extensions as occurs on impenetrable glass or plastic surfaces, range in shape from dendritic to stellate to bipolar, depending on matrix stiffness and tension (Grinnell, 2003). Similar morphological features have been described for cells in tissues (Breathnach, 1978;Doljanski, 2004;Goldsmith et al., 2004;Langevin et al., 2005). In part, differences in morphology between cells in twodimensional (2D) versus 3D culture may result from the symmetric adhesive interactions in 3D matrices versus the forced asymmetry of 2D surfaces (Beningo et al., 2004).In tissues, fibroblasts are phagocytic cells (McGaw and Ten Cate, 1983;Everts et al., 1996Everts et al., , 2003, and in culture they have been shown to ingest both fibronectin (FN) and collagen-coated late...

Migration of tumor cells in 3D matrices is governed by matrix stiffness along with cell-matrix adhesion and proteolysis

“…Recent advances in multiple particle-tracking rheology (23,24) as well as the use of nested collagen matrices (25,26) to probe tension in the proximity of cells have shown great promise in improving our understanding of cell-matrix interactions at these length scales.…”

Fibroblast mechanics in 3D collagen matrices☆

“…When fibroblasts interact with collagen matrices -unlike planar surfaces --the cells can penetrate into the substance of the matrix and become entangled with matrix fibrils (Figure 1) [17]. Cells interacting with collagen matrices exhibit distinct patterns of signaling and migration [18][19][20][21] and remodel matrices both locally and globally [5,6,[22][23][24]] to achieve tensional homeostasis [25,26].…”

Microtubule function in fibroblast spreading is modulated according to the tension state of cell–matrix interactions

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