Asymmetric nanotopography biases cytoskeletal dynamics and promotes unidirectional cell guidance

Abstract

Many biological and physiological processes depend upon directed migration of cells, which is typically mediated by chemical or physical gradients or by signal relay. Here we show that cells can be guided in a single preferred direction based solely on local asymmetries in nano/microtopography on subcellular scales. These asymmetries can be repeated, and thereby provide directional guidance, over arbitrarily large areas. The direction and strength of the guidance is sensitive to the details of the nano/microtopography, suggesting that this phenomenon plays a context-dependent role in vivo. We demonstrate that appropriate asymmetric nano/microtopography can unidirectionally bias internal actin polymerization waves and that cells move with the same preferred direction as these waves. This phenomenon is observed both for the pseudopoddominated migration of the amoeboid Dictyostelium discoideum and for the lamellipod-driven migration of human neutrophils. The conservation of this mechanism across cell types and the asymmetric shape of many natural scaffolds suggest that actin-wave-based guidance is important in biology and physiology.cell migration | actin waves | contact guidance | Dictyostelium discoideum | neutrophils D irected cell migration is essential for many critical biological and physiological processes (1), such as embryonic development (2), wound healing (3), immune response (4), and angiogenesis (5). Guidance of cells can be achieved through external gradients in properties such as chemical concentration (6, 7), substrate rigidity (8), and adhesion (9). The total distance over which gradients can guide cells is limited by the finite dynamic range of cellular sensing [i.e., guidance by a gradient between the front and back of each cell requires that the overall signal change significantly with the cell's position (Fig. 1A)]. Cells can overcome this limitation by relaying chemotactic signals, but chemical relay of directional information requires intricate orchestration and timing of signals (7, 10, 11). Shear flow is another approach to guiding cells unidirectionally over large distances, but shear flow is an active process that requires constant fluid flow at a controlled rate and viscosity (12, 13). Surface nanotopography, such as ridges and grooves (14-17) or aligned collagen fibers (18), can act as a primitive and ubiquitous guidance cue, but the symmetric structures used in prior studies only provided bidirectional guidance.Although previous work has implicated cytoskeletal structures [in particular, the alignment of stress fibers (16)] in similar contact guidance processes, we have recently shown that nanotopography also steers the dynamics of the cell's scaffolding by biasing actin polymerization waves (17). Intracellular dynamics involving the self-assembly of actin and actin's associated proteins into 3D, traveling waves that propel a cell forward through a sustained cycle of polymerization and depolymerization have recently been found to be ubiquitous in cell migration (19)(20)(21)(22). Given ...

Progress and perspectives in signal transduction, actin dynamics, and movement at the cell and tissue level: lessons fromDictyostelium

“…This suggested that actin waves are more likely to play a physiologically relevant role in the PIP3-dependent process of macropinocytosis, the uptake of fluid by cells, where actin coats vesicles that become internalized. However, recently Sun et al [54] show compelling evidence that actin waves do indeed play a role in cell migration. They created structured surfaces with asymmetrically sloped nanoridges.…”

Geometrical Determinants of Neuronal Actin Waves

“…This suggests that actin waves, as already proposed in the seminal work of Ruthel and Banker (Ruthel and Banker, 1999), might create tension and exert pulling forces along neurites, which are important players implied in neurite growth and axonal specification (Lamoureux et al, 2002; Franze and Guck, 2010). As compared to non-neuronal actin waves [e.g., actin ruffles (Goicoechea et al, 2006), circular waves (Bernitt et al, 2015) and planar waves (Sun et al, 2015)], neuronal actin waves have remained poorly studied for many years, and the wave generation mechanism still remains elusive. Several in-depth studies published in recent years have however provided new insights into the role and characteristics of these propagative structures.…”

Quantifying topography-guided actin dynamics across scales using optical flow

“…when cells encounter obstacles 10 . It has also been established that ridges of width comparable to fibers in the extracellular matrix (ECM) can alter actin dynamics significantly 9,11,12 and bias the localization of focal adhesions 13,14 . Thus, in vivo, the topography of the ECM, such as collagen networks 15,16 , is likely to modulate actin dynamics.…”

“…In prior work we have shown that actin waves can be nucleated near, and guided along, periodic nanotopography, in a phenomenon termed esotaxis. Actin-wave guidance has been observed in cell types that exhibit distinct physiological functions and migration phenotypes, including Dictyostelium discoideum 11,12 , neutrophil-like HL60 cells 12 , B cells 9 , and breastcancer cell lines 17 . However, there are clear differences in the responses of each of these cell types to nanotopography.…”

“…However, there are clear differences in the responses of each of these cell types to nanotopography. For example, although both D. discoideum and HL60 cells exhibit esotaxis, these two types of cells have been found to move preferentially in different directions on specific nanoscale asymmetric sawtooth textures 12 . Furthermore, different breast-cancer cell lines preferentially move in different directions on asymmetric sawtooth nanotopography 17 .…”