Multivalent Integrin-Specific Ligands Enhance Tissue Healing and Biomaterial Integration

Abstract

Engineered biointerfaces covered with biomimetic motifs, including short bioadhesive ligands, are a promising material-based strategy for tissue repair in regenerative medicine. Potentially useful coating molecules are ligands for the integrins, major extracellular matrix receptors that require both ligand binding and nanoscale clustering for maximal signaling efficiency. We prepared coatings consisting of well-defined multimer constructs with a precise number of recombinant fragments of fibronectin (monomer, dimer, tetramer, and pentamer) to assess how nanoscale ligand clustering affects integrin binding, stem cell responses, tissue healing, and biomaterial integration. Clinical-grade titanium was grafted with polymer brushes that presented monomers, dimers, trimers, or pentamers of the α5β1 integrin–specific fibronectin III (7 to 10) domain (FNIII7–10). Coatings consisting of trimers and pentamers enhanced integrin-mediated adhesion in vitro, osteogenic signaling, and differentiation in human mesenchymal stem cells more than did surfaces presenting monomers and dimers. Furthermore, ligand clustering promoted bone formation and functional integration of the implant into bone in rat tibiae. This study establishes that a material-based strategy in which implants are coated with clustered bioadhesive ligands can promote robust implant-tissue integration.

Nanopatterning Reveals an ECM Area Threshold for Focal Adhesion Assembly and Force Transmission that is regulated by Integrin Activation and Cytoskeleton Tension

“…Several studies have shown that ECM ligand spacing regulates FA and stress fiber assembly, cell spreading and migration, and adhesive forces (Massia and Hubbell, 1991 Coussen et al, 2002;Koo et al, 2002;Jiang et al, 2003;Arnold et al, 2004;Cavalcanti-Adam et al, 2007;Petrie et al, 2010;Selhuber-Unkel et al, 2010). However, whether the geometric organization of the ECM ligand regulates FA assembly and force transmission has not been addressed.…”

“…Previous work has shown that both ECM rigidity and ligand spacing influence FA and stress fiber assembly, cell spreading, migration speed, and adhesive forces (Massia and Hubbell, 1991;García et al, 1998a;Maheshwari et al, 2000;Wang et al, 2001;Coussen et al, 2002;Koo et al, 2002;Jiang et al, 2003;Arnold et al, 2004;Griffin et al, 2004;Engler et al, 2006;CavalcantiAdam et al, 2007;Petrie et al, 2010;Selhuber-Unkel et al, 2010). For instance, different average minimal RGD ligand spacings are required for spreading (440 nm) and FA assembly (140 nm) (Massia and Hubbell, 1991).…”

“…These focal adhesion (FA) complexes consist of integrins and actins vertically separated by a ,40 nm core that includes cytoskeletal elements, such as vinculin, talin and a-actinin, and signaling molecules, including FAK, src, and paxillin Zamir and Geiger, 2001;Kanchanawong et al, 2010). Integrin clustering is a crucial step in the adhesive process promoting recruitment of cytoskeletal components, activation of signaling molecules, and enhancing adhesive force (Miyamoto et al, 1995a;Miyamoto et al, 1995b;Maheshwari et al, 2000;Roca-Cusachs et al, 2009;Bunch, 2010;Petrie et al, 2010). These integrin-based FAs serve as mechanosensors converting environmental mechanical cues into biological signals (Geiger et al, 2009).…”

Hydrogels that mimic developmentally relevant matrix and N-cadherin interactions enhance MSC chondrogenesis

“…It has recently been shown that cells can exert traction forces through cadherin cell-cell contacts (42,43), so hydrogel mechanics and the loading environment may need to be considered in the utility of such materials. It has also been shown that cluster presentation of certain mimetic peptides, such as those containing an integrin-binding Arg-Gly-Asp (RGD) domain, significantly increases their binding efficacy (44,45). Therefore, the local presentation (e.g., clustering and tether length) may be optimized independent of hydrogel mechanics to further mimic and present the molecule for cellular interactions.…”

From Self-Assembled Monolayers to Coatings: Advances in the Synthesis and Nanobio Applications of Polymer Brushes

“…In comparison, the fragment had better osteointegration in vivo than the RGD sequence, suggesting that integrin specificity is relevant, as different integrins bind to RGD and FMIII7-10. Additionally, the importance of integrin clustering was shown using monomer, dimer, trimer, and pentamers of FMIII7-10 [189]. Studies have yet to be done to investigate if polymer brush coatings can enhance osteointegration under diseased states such as osteoporosis.…”