Substrate-Bound Protein Gradients to Study Haptotaxis

Abstract

Cells navigate in response to inhomogeneous distributions of extracellular guidance cues. The cellular and molecular mechanisms underlying migration in response to gradients of chemical cues have been investigated for over a century. Following the introduction of micropipettes and more recently microfluidics for gradient generation, much attention and effort was devoted to study cellular chemotaxis, which is defined as guidance by gradients of chemical cues in solution. Haptotaxis, directional migration in response to gradients of substrate-bound cues, has received comparatively less attention; however, it is increasingly clear that in vivo many physiologically relevant guidance proteins – including many secreted cues – are bound to cellular surfaces or incorporated into extracellular matrix and likely function via a haptotactic mechanism. Here, we review the history of haptotaxis. We examine the importance of the reference surface, the surface in contact with the cell that is not covered by the cue, which forms a gradient opposing the gradient of the protein cue and must be considered in experimental designs and interpretation of results. We review and compare microfluidics, contact printing, light patterning, and 3D fabrication to pattern substrate-bound protein gradients in vitro. The range of methods to create substrate-bound gradients discussed herein makes possible systematic analyses of haptotactic mechanisms. Furthermore, understanding the fundamental mechanisms underlying cell motility will inform bioengineering approaches to program cell navigation and recover lost function.

Controlled microfluidics to examine growth-factor induced migration of neural progenitors in the Drosophila visual system

“…Our migration data is significant because RBG glia were initially only believed able to migrate into the eye disk via physical mechanisms of haptotaxis, i.e. crawling along a substrate (Haeger et al, 2015; Ricoult et al, 2015). However, more recent work suggested abilities of RBG to migrate toward differentiating photoreceptors without using a continuous physical substratum (Rangarajan et al, 1999).…”

Different integrins mediate haptotaxis of T lymphocytes towards either lower or higher adhesion zones

“…Adhesive haptotaxis is therefore directly explained by a tug of war in the cell adherence zone, areas with lower grip destabilizing spontaneously under traction in favor to areas with a higher grip (17). In contrast, amoeboid cells migrate at high speed with low adhesion and low traction forces transferred to the substrate(23- 25). A tug of war mechanism, with an interplay of strong adhesion and high traction, is therefore not applicable to amoeboid cells, and the existence of adhesive haptotaxis for leukocytes remains an open question.…”

How cells respond to environmental cues – insights from bio-functionalized substrates

“…Passive diffusion of a chemoattractant across a porous membrane has also been used to create local gradients in the absence of flow (Dupin et al, 2013). Furthermore, imprinting of protein gradients on rigid substrates (Ricoult et al, 2015;Wu et al, 2011) or controlled stenciling and/or photo-immobilization techniques (Bélisle et al, 2009(Bélisle et al, , 2012Strale et al, 2016) has revealed the molecular basis for haptotaxis, the migration of cells along an ECM gradient. In addition, the use of 3D matrix hydrogels containing smooth gradients of crosslinking density (i.e.…”