Integrin binding specificity regulates biomaterial surface chemistry effects on cell differentiation

Abstract

Biomaterial surface chemistry has profound consequences on cellular and host responses, but the underlying molecular mechanisms remain poorly understood. Using self-assembled monolayers as model biomaterial surfaces presenting well defined chemistries, we demonstrate that surface chemistry modulates osteoblastic differentiation and matrix mineralization independently from alterations in cell proliferation. Surfaces were precoated with equal densities of fibronectin (FN), and surface chemistry modulated FN structure to alter integrin adhesion receptor binding. OH-and NH 2-terminated surfaces up-regulated osteoblast-specific gene expression, alkaline phosphatase enzymatic activity, and matrix mineralization compared with surfaces presenting COOH and CH 3 groups. These surface chemistry-dependent differences in cell differentiation were controlled by binding of specific integrins to adsorbed FN. Function-perturbing antibodies against the central cell binding domain of FN completely inhibited matrix mineralization. Furthermore, blocking antibodies against ␤1 integrin inhibited matrix mineralization on the OH and NH 2 surfaces, whereas function-perturbing antibodies specific for ␤3 integrin increased mineralization on the COOH substrate. These results establish surface-dependent differences in integrin binding as a mechanism regulating differential cellular responses to biomaterial surfaces. This mechanism could be exploited to engineer materials that control integrin binding specificity to elicit desired cellular activities to enhance the integration of biomaterials and improve the performance of biotechnological culture supports.cell adhesion ͉ signaling ͉ osteoblast ͉ mineralization B iomaterial surface chemistry modulates in vitro and in vivo cellular responses, including adhesion, survival, cell cycle progression, and expression of differentiated phenotypes (1-8). These cell-material interactions regulate cell and host responses to implanted devices, biological integration of biomaterials and tissue-engineered constructs, and the performance of cell arrays and biotechnological cell culture supports (9-12). For instance, anionic and neutral hydrophilic surfaces increase macrophage͞ monocyte apoptosis and reduce macrophage fusion to modulate inflammatory responses to implanted materials (8). The effects of biomaterial surface properties on cellular responses are generally attributed to material-dependent differences in adsorbed protein species, concentration, and͞or biological activity. Nonetheless, the molecular mechanisms modulating these substrate-dependent, complex higher-order cellular activities remain poorly understood. This lack of a fundamental understanding of cell-material interactions hinders progress toward the development of synthetic materials that elicit desired cellular responses. Using self-assembled monolayers (SAMs) presenting well defined chemistries as model biomaterial surfaces, we previously showed that surface chemistry modulates the structure and activity of adsorbed fibronectin (FN) (13)...

Material‐Driven Fibronectin Assembly Promotes Maintenance of Mesenchymal Stem Cell Phenotypes

“…[ 40 ] Proper conformation of adsorbed proteins directs integrin binding, focal adhesion assembly, and cell differentiation. [ 19,41,42 ] We have previously reported the amount of FN adsorbed on PEA and PMA to be similar at ≈340 ng cm −2 for both polymers. [ 22 ] However, FN distribution and conformation differ signifi cantly with interconnected FN nanonetworks on PEA whereas globular aggregates appeared on PMA (Figure 1 ).…”

“…The conformation and distribution of this protein layer will determine integrin binding and the organization of focal adhesions, which in turn will infl uence cell signaling and hence fate. [16][17][18][19][20] Acrylates are common biomaterials with tunable physical properties. [ 21 ] In this work we used substrates that slightly differ in surface chemistry, varying only one methyl group in the side chain-poly(ethyl acrylate) (PEA) and poly(methyl acrylate) (PMA).…”

Design and Characterization of a Synthetically Accessible, Photodegradable Hydrogel for User-Directed Formation of Neural Networks

“…(3)(4)(5) However, other tissue engineering applications necessitated the development of scaffolds that introduced biochemical signals to promote or direct desired cell function, and this led to significant advances in bioconjugation methods to tether proteins and small molecules, conferring functionalization and signaling to embedded cells. Such approaches have been exploited to design materials that preferentially differentiate stem cells into different lineages, (6,7) increase production of extracellular matrix (ECM) components, (8) direct cell migration, (9)(10)(11) and control extension of axons. (11,12) However, in vivo signals are not presented in such a static manner, but rather, complex spatially and temporally regulated presentation of biological cues drive many fundamental processes.…”

Growth substrate induced functional changes elucidated by FTIR and Raman spectroscopy in in–vitro cultured human keratinocytes

“…It is known that biomaterial surfaces effect significant responses in the cell, but the underlying molecular mechanisms generating these responses remain poorly understood [16]. Noninvasive spectroscopic measurements of cellular function in in-vitro cultured cell lines require substrates such as quartz, ZnSe and MirrIR (Ag/SnO 2 coated glass for FTIRM from Kevley Technologies) etc.…”