Ring-Shaped Microlanes and Chemical Barriers as a Platform for Probing Single-Cell Migration

Abstract

Quantification and discrimination of pharmaceutical and disease-related effects on cell migration requires detailed characterization of single-cell motility. In this context, micropatterned substrates that constrain cells within defined geometries facilitate quantitative readout of locomotion. Here, we study quasi-one-dimensional cell migration in ring-shaped microlanes. We observe bimodal behavior in form of alternating states of directional migration (run state) and reorientation (rest state). Both states show exponential lifetime distributions with characteristic persistence times, which, together with the cell velocity in the run state, provide a set of parameters that succinctly describe cell motion. By introducing PEGylated barriers of different widths into the lane, we extend this description by quantifying the effects of abrupt changes in substrate chemistry on migrating cells. The transit probability decreases exponentially as a function of barrier width, thus specifying a characteristic penetration depth of the leading lamellipodia. Applying this fingerprint-like characterization of cell motion, we compare different cell lines, and demonstrate that the cancer drug candidate salinomycin affects transit probability and resting time, but not run time or run velocity. Hence, the presented assay allows to assess multiple migration-related parameters, permits detailed characterization of cell motility, and has potential applications in cell biology and advanced drug screening.Migrating cells play a pivotal role in morphogenesis 1 , immune responses 2 , and cancer metastasis 3 . Their style of motion, often assigned as crawling, is powered by complex cytoskeletal rearrangements that deform and propel the cell. On solid surfaces, eukaryotic cells extend protrusions, which attach to the substrate and are then actively retracted, thus dragging the cell forward. The formation of the leading protrusion of a migrating cell, the lamellipodium, is driven by actin polymerization, while adhesion and contraction are predominantly regulated by integrin-based focal adhesions and the actomyosin apparatus 4,5 . Coupling of focal adhesion complexes to the cytoskeletal network in turn reinforces actin assembly and hence lamellipodia extension 6 . The complex interplay between actomyosin contractility and focal adhesions, which are capable of sensing and transducing chemical and mechanical cues in the extracellular environment, renders the cell sensitive to external stimuli such as the composition and rigidity of the extracellular matrix (ECM) and the underlying substrate 7,8 .In recent studies, various theoretical models for cell migration have been proposed and implemented. These implementations range from molecular level approaches, which describe cell migration in terms of internal reaction diffusion dynamics 9-11 to coarse grained approaches in which individual cells are resembled by sets of pixels 12-14 or interacting, self-propelled geometrical objects [15][16][17] . Many of these models are able to reproduce the basic ...

Quasi-periodic migration of single cells on short microlanes

“…This behavior is quantified by the dominant oscillation frequency, the spatial distribution of cell positions and the persistent velocity of polarized migrating cells as a function of microlane length. The finding of quasi oscillatory pole-to-pole migration with repetitive depolarization-repolarization cycles is in agreement with previous measurements of the typical persistence length of directed migration on microtracks or microchannels, which was reported to be about 400 μm and hence larger than the length of the microlanes studied here [7,32,33,41]. At the poles of the microlanes, actin polymerization in the leading protrusion is quenched which is most likely due to the reduced capability to form focal adhesions in the PEGylated area.…”

“…There, a universal relation between persistence and cell velocity was shown to hold [7]. Other micropatterns with non-trivial geometries give rise to novel migratory behavior: circular adhesion islands lead to rotational migration of small cohorts of cells [36], ratchet geometries induce directed migration [37][38][39], cells confined in dumbbell-shaped micropatterns undergo repeated stochastic transitions characterized by intricate nonlinear migratory dynamics [40], and microlanes with gaps show emergence of stochastic cell reversal and transits [41]. In addition, migration patterns may change upon interference with the cytoskeleton.…”

Quasi-periodic migration of single cells on short microlanes

“…There, we also show snapshots of the 396 leading edge of simulated cells for a direct comparison between experiment and 397 simulation. Both in experiment and simulation, we find that the lamellipodium splits or microchannels, which was reported to be about 400 µm and hence larger than the 432 length of the microlanes studied here [7,32,33,41]. At the poles of the microlanes, 433 actin polymerization in the leading protrusion is quenched which is most likely due to 434 the reduced capability to form focal adhesions in the PEGylated area.…”

Non-Markovian data-driven modeling of single-cell motility

“…Some cells divide, die, or occasionally leave the microlane during the recording period, resulting in a broad distribution of trajectory lengths. The experimental methods have been described before [36].…”

“…Our study employs one-dimensional cell migration on microcontact printed tracks [34,35]. Specifically, we analyze a large data set of human breast cancer cells on homogeneous circular tracks, which is a setup we previously introduced and which has the advantage that long, one-dimensional time traces of many cells can be monitored without mutual interference [36]. The single-cell analysis reveals stationary statistics as well as almost perfect Gaussian velocity distributions with significant cell-to-cell variations.…”