Role of the α1β1 integrin complex in collagen gel contraction in vitro by fibroblasts

Abstract

Matrix remodeling, critical to embryonic morphogenesis and wound healing, is dependent on the expression of matrix components, their receptors, and matrix proteases. The collagen gel assay has provided an effective model for the examination of the functional role(s) of each of these groups of molecules in matrix remodeling. Previous investigations have indicated that collagen gel contraction involves the beta 1 integrin family of matrix receptors and is stimulated by several growth factors, including TGF-beta, PDGF, and angiotensin II. In particular, collagen gel remodeling by human cells involves the alpha 2 beta 1 and, to a lesser extent, the alpha 1 beta 1 integrin complexes. The present studies were undertaken to determine the role of the alpha 1 integrin chain, a collagen/laminin receptor, in collagen gel contraction by rodent and avian fibroblasts. A high degree of correlation was found between the expression of the alpha 1 beta 1 integrin complex and the relative ability of cells to contract collagen gels. Further studies using antibodies and antisense oligonucleotides against the alpha 1 integrin indicated a significant role for this integrin chain in contraction of collagen gels by rat cardiac fibroblasts. In addition, antibodies to the alpha 1 integrin chain inhibited migration of these fibroblasts on a collagen substratum, suggesting that at least one role of this integrin is in migration of cells in collagen gels. These results indicate that the alpha 1 beta 1 integrin complex plays a significant role in cellular interactions with interstitial collagen that are involved in matrix remodeling such as is seen during morphogenesis and wound healing.

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

“…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), and blocking antibodies against integrin ␣2␤1 slowed down the time course of fibroblast adhesion and spreading on collagen matrices consistent with previous findings.…”

“…Surprisingly, this treatment did not cause cells to detach from collagen matrices although essentially 100% of the cells were removed from collagencoated coverslips. This difference in trypsin sensitivity suggested that the cells might be anchored to collagen matrices at least in part by an integrin-independent mechanism.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), and blocking antibodies against integrin ␣2␤1 slowed down the time course of fibroblast adhesion and spreading on collagen matrices consistent with previous findings.Divalent cations also have been implicated in integrin activity (Gailit and Ruoslahti, 1988;Leitinger et al, 2000), and in the presence of 10 mM EDTA, cell adhesion to collagen matrices was almost completely inhibited. Yet, once the cells were attached, treatment with 10 mM EDTA was unable to release cells from collagen matrices, even though cells on collagen-coated coverslips detached completely.…”

“…In collagen matrices, integrin ␣2␤1 has been implicated in fibroblast adhesion although other integrins may also be important, 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). Addition of blocking antibodies against ␣2␤1 (10 g/ml) inhibited human fibroblast adhesion to collagen-coated but not FN-coated coverslips (our unpublished data).…”

“…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).…”

“…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).…”