Induction of Cell Polarization and Migration by a Gradient of Nanoscale Variations in Adhesive Ligand Spacing

Abstract

Cell interactions with adhesive surfaces play a vital role in the regulation of cell proliferation, viability and differentiation, and affect multiple biological processes. Since cell adhesion depends mainly on the nature and density of the adhesive ligand molecules, spatial molecular patterning, which enables the modulation of adhesion receptor clustering, might affect both the structural and signalling activities of the adhesive interaction. We herein show that cells plated on surfaces that present a molecularly defined spacing gradient of an integrin RGD ligand, can sense small but consistent differences in adhesive ligand spacing of about 1 nm across the cell diameter, which is approximately 61 m when the spacing includes 70 nm. Consequently, these positional cues induce cell polarization, and initiate cell migration and signalling. We propose that differential positional clustering of the integrin transmembrane receptors is used by cells for exploring and interpreting their environment, at high spatial sensitivity.Adhesion of tissue cells to the extracellular matrix depends on the activation of specific transmembrane receptors; e.g. integrins, which leads to the assembly of specialized adhesion sites known as focal adhesions (FA). 1 Activation and spatial organization of integrins are mainly controlled by epitopes containing a RGD (R = arginine, G = glycine, D = aspartate) sequence, that are present on a variety of adhesive extracellular matrix (ECM) proteins. Recent studies indicated that beyond the chemical specificity of the adhesive epitope, 2 many physical features of the adhesive surface, including its topography, 3 rigidity, 4 and precise epitope spacing, 5 are critical for guiding receptor-mediated adhesion formation and signalling. Specifically, it was demonstrated that cyclic RGDfK peptides linked to nanogold particles 6 which were arranged in pattern on substrates and interspaced by 58 or 73 nm, influence cell adhesion, 5 spreading, focal adhesion assembly, and migration 7,8 in very different ways. In these studies, control experiments demonstrated that only the specific functionalization of nanogold particles with cyclic RGD induced integrin clustering and such focal adhesion formation upon interaction with cells such as 3T3-fibroblasts or -* Corresponding author: spatz@mf.mpg.de. + Both authors contributed equally to this work. 19 On the molecular length scale, these methods enable quantification of an average molecular concentration, which gradually varies along the adhesive surface; however, they are too "noisy" to quantify the densities themselves, and density variations capable of inducing cell polarization. NIH Public AccessWe herein demonstrate a novel surface patterning technique for the generation of nanoparticle spacing gradients, which is based on controlled modulation of the selfassembly of diblock copolymer micelles. Due to the self-assembly of macromolecules, large-scale surface areas are easily processed by this technique. After successful biofunctionalization of the nano...

Deflection induced cellular focal adhesion and anisotropic growth on vertically aligned silicon nanowires with differing elasticity

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Rapid Reversible Photoswitching of Integrin‐Mediated Adhesion at the Single‐Cell Level

“…Furthermore, they are also consistent with UV-vis spectrometry data, showing a switching effi ciency of 47%. Cells can sense tiny variations in their environment [ 23 ] and their adhesion structures exhibit extremely fast molecular turnover rates of a few minutes, [ 24 ] so that our switching effi ciency should modulate cell adhesion at many different timescales.…”

Tissue Engineering for Tissue and Organ Regeneration

“…Finally, intracoronary infusion of bone marrow cells was performed in 33 patients with dilated cardiomyopathy (DCM) by using an over-the-wire balloon catheter. Three month follow-up demonstrated an improvement in left ventricular pump function while a modest improvement in Brain Natriuretic Peptide (BNP) levels was reported after 1 year [6]. Importantly, the conditions chosen in the present clinical trial were representative of different conditions (acute, chronic phase) encountered in the clinic.…”

“…In fact, when autologous skeletal myoblasts were injected into the heart of patients suffering from ischemic cardiomyopathy, the modest functional improvement obtained was impaired by the arising of arrhythmia events, thus requiring the adoption of a pacemaker [5]. On the other side, intracoronary administration of bone marrow mesenchymal stem cells resulted in minimal improvements in cardiac contractile function in patients with dilated cardiomyopathy [6]. These mild results were mostly ascribed to a paracrine effect exerted on host tissue, rather than to a direct contribution of stem cells to the contractile activity.…”