Fibronectin Growth Factor-Binding Domains Are Required for Fibroblast Survival

Abstract

Fibronectin (FN) is required for embryogenesis, morphogenesis, and wound repair, and its Arg–Gly–Asp-containing central cell-binding domain (CCBD) is essential for mesenchymal cell survival and growth. Here, we demonstrate that FN contains three growth factor-binding domains (FN-GFBDs) that bind platelet-derived growth factor-BB (PDGF-BB), a potent fibroblast survival and mitogenic factor. These sites bind PDGF-BB with dissociation constants of 10–100 nm. FN-null cells cultured on recombinant CCBD (FNIII8–11) without a FN-GFBD demonstrated minimal metabolism and underwent autophagy at 24 hours, followed by apoptosis at 72 hours, even in the presence of PDGF-BB. In contrast, FN-null cells plated on FNIII8–11 contiguous with FN-GFBD survived without, and proliferated with, PDGF-BB. FN-null cell survival on FNIII8–11 and noncontiguous arrays of FN-GFBDs required these domains to be adsorbed on the same surface, suggesting the existence of a mesenchymal cell-extracellular matrix synapse. Thus, fibroblast survival required GF stimulation in the presence of a FN-GFBD, as well as adhesion to FN through the CCBD. The findings that fibroblast survival is dependent on FN-GFBD underscore the critical importance of pericellular matrix for cell survival and have significant implications for cutaneous wound healing and regeneration.

Shrink Wrapping Cells in a Defined Extracellular Matrix to Modulate the Chemo-Mechanical Microenvironment

“…In this paper we have not introduced growth factors beyond what might be present in the FBS used during culture. However, growth factors such as platelet derived growth factor (PDGF), which through binding to FN is known to regulate its bioactivity, 20 could easily be incorporated. Thus, we envision that using SHELL to immobilize specific growth factors around cells could further modulate cell behavior, and in the case of 3D fibrin gels may produce a cell response that we could observe.…”

Extracellular Matrix-Inspired Growth Factor Delivery Systems for Skin Wound Healing

“…47 Indeed, the signaling of many growth factors is regulated by the dynamic interactions between growth factors, ECM proteins, adhesion receptors, and growth factor receptors. 31,48,49 Interestingly, the formation of molecular complexes between growth factors and ECM proteins such as fibronectin 50,51 and vitronectin 20,46 can considerably enhance growth factor signaling. In particular, ECM protein-growth factor complexes can induce the formation of clusters between growth factor-receptors and integrins.…”

Fibronectin Interaction and Enhancement of Growth Factors: Importance for Wound Healing

“…30,33,53 For example, using either FNIII 9-10 or FNIII [8][9][10][11] for the a5b1 cell-binding domains and FNIII 1 , FNIII [12][13][14] , or FNIII 12-15 for a GFbinding domain, synergistic effects on human dermal fibroblasts were only demonstrated when the celland GF-binding domains were coupled or presented on the same surface. These results strongly support the contention that GF and FN synergy under these conditions requires the cell-binding and GF-binding domains in close proximity outside the cell and may be organized, in part, by FN domains from adjacent FN molecules in a FN fibril.…”

“…22,29 FN as a reservoir for GF Increasing evidence shows that GFs can bind to multiple sites in FN. 30,31 Thus, FN can serve as a reservoir for GFs increasing their local bioavailability. HGF binds FN and forms complexes with the HGF receptor (HGFR) and integrins, leading to enhanced cell migration.…”

“…In addition, we have shown that FN-GF-binding domains (FNIII 1 , FNIII [13][14] , and IIICS) enhance PDGF-BB survival signals in FN-null fibroblasts, only when they were surface bound. 30 These FN domains contain sequence similarities that bind PDGF-BB 31 as well as FGF-2, and TGF-b1 (Lin et al, manuscript in preparation). These observations are similar to substrate-bound EGF being more potent than soluble EGF.…”