Collagen Fibril Flow and Tissue Translocation Coupled to Fibroblast Migration in 3D Collagen Matrices

Abstract

In nested collagen matrices, human fibroblasts migrate from cell-containing dermal equivalents into surrounding cell-free outer matrices. Time-lapse microscopy showed that in addition to cell migration, collagen fibril flow occurred in the outer matrix toward the interface with the dermal equivalent. Features of this flow suggested that it depends on the same cell motile machinery that normally results in cell migration. Collagen fibril flow was capable of producing large-scale tissue translocation as shown by closure of a ϳ1-mm gap between paired dermal equivalents in floating, nested collagen matrices. Our findings demonstrate that when fibroblasts interact with collagen matrices, tractional force exerted by the cells can couple to matrix translocation as well as to cell migration. INTRODUCTIONCell migration depends on the multistep process of cell extension, adhesion, exertion of backward tractional force, and tail retraction (Lauffenburger and Horwitz, 1996;Mitchison and Cramer, 1996;Galbraith and Sheetz, 1997;Beningo et al., 2001;Ridley et al., 2003). The extensive body of research underlying the multistep model is based on studies with tissue cells on extracellular matrix (ECM)-coated planar surfaces including rigid materials such as glass or plastic coverslips as well as flexible materials such as polyacrylamide. On ECM-coated planar surfaces, cells can modulate their cytoskeletal function and adhesion strength in response to surface mechanics (Balaban et al., 2001;Discher et al., 2005;Ingber, 2006;Vogel and Sheetz, 2006). However, adsorbed or covalently attached ECM molecules tend to be held in register with each other with little capacity to undergo cell-mediated mechanical and molecular reorganization.Type 1 collagen is the major protein component of fibrous connective tissues. These connective tissues provide mechanical support and frameworks throughout the body, and fibroblasts are the cell type primarily responsible for their biosynthesis and remodeling. Three-dimensional (3D) matrices prepared with type I collagen exhibit mechanical properties that resemble connective tissue (Barocas et al., 1995;Wakatsuki et al., 2000;Roeder et al., 2002;Silver et al., 2002;Ahlfors and Billiar, 2007). Unlike ECM-coated material surfaces, fibroblasts can mechanically remodel collagen matrices both locally and globally (Brown et al., 1998;Tomasek et al., 2002;Grinnell, 2003;Petroll, 2004; Tranquillo, 1999Such mechanical remodeling of connective tissue ECM is believed to be important for tissue homeostasis (Silver et al., 2002;Wiig et al., 2003;Goldsmith et al., 2004;Langevin et al., 2004), aging (Varani et al., 2004), repair (Tonnesen et al., 2000Tomasek et al., 2002;Grinnell, 2003), fibrosis (Eckes et al., 2000;Desmouliere et al., 2005), and tumorigenesis (Beacham and Cukierman, 2005;Gaggioli et al., 2007;Yamada and Cukierman, 2007).Cells interacting with 3D collagen matrices exhibit distinct patterns of cell signaling (Cukierman et al., 2002;Wozniak et al., 2003;Beningo et al., 2004;Rhee et al., 2007) and increa...

Mapping proteolytic cancer cell-extracellular matrix interfaces

“…However, novel multimodal imaging technology, such as confocal fluorescence and reflection, multiphoton-excited fluorescence and second harmonic detection, or scanning electron microscopy, now permits the reconstruction of proteolytic cell-matrix interactions in time and space. When embedded within 3D ECM, such as fibrillar fibrin or collagen lattices, or when seeded onto a 3D dermis slice ex vivo, many cell types including fibroblasts and cancer cells polarize and start to migrate [7,9,22,[30][31][32]. Cell surface adhesion receptors such as integrins, and ECM-degrading proteases can focally interact with the substrate in different cellular locations that convey specific functions, including (i) the leading edge and protruding pseudopodia with anterior zones of ECM degradation, (ii) the mid region that glides along the substrate and cleaves lateral ECM structures, and (iii) the retracting trailing edge that weakens adhesion bonds and supports forward movement of the cell (Fig.…”

Effects of Migrating Cell-Induced Matrix Reorganization on 3D Cancer Cell Migration

“…We hypothesize that mechanics-based factor can in fact be the most universal explanation to all our observations. In particular, we have noticed that occasionally, when some part of the periphery of the outer gel detached from the dish wall, cells ceased migration into that region, akin to the case of floating gel, 33 while they continued radial migration into other regions. A recent numerical modeling of cell migration in 3D gel that explicitly took into account cell contractility mechanisms also shows that cells in a uniform gel tend to move towards a constrained boundary.…”

“…52 For genuine 3D cell culture, hydrogel models have been typically built with hydrated collagen, which is a major protein component of connective tissues. 34 Such models have been increasingly adopted in 3D cell culture systems and cell migration assays, 17,33,50 as these 3D collagen matrix models provide a more physiologically relevant and controlled environments for migrating cells, 53 and also allow for cell-induced remodeling to the matrix through extracellular matrix (ECM) protein synthesis, proteolytic degradation and matrix contraction.…”

“…For example, the contraction of collagen matrix is closely associated with the invasive migration of wild-type and transformed fibroblasts in 3D gel system. 30,33 Collagen fibrils are pulled by migrating cells through contraction, 24 and the local deformation of fibrillar collagen depend on the cytoskeleton dynamics, 36 focal adhesion, 37 and cell contractility. 46 Secondly, physical remodeling may induce long term and significant changes to the matrix.…”

Mechanical Forces in Cutaneous Wound Healing: Emerging Therapies to Minimize Scar Formation

“…[68][69][70] Fibroblasts grown in mechanically loaded three-dimensional collagen lattices resembling connective tissue develop dendritic extensions that enable them to migrate and remodel their matrices. [71][72][73][74] Simply subjecting fibroblasts to microdeformations caused by suction, as one would observe with vacuum-assisted wound closure, results in increased fibroblast proliferation and up-regulation of typical genes expressed by fibroblasts (e.g., type 1 collagen alpha 1, fibroblast growth factor 2, TGF-b1). 75 Using an in vitro model to investigate the effects of cyclically stretching …”