A Stable Chemokine Gradient Controls Directional Persistence of Migrating Dendritic Cells

Abstract

Navigation of dendritic cells (DCs) from the site of infection to lymphoid organs is guided by concentration gradients of CCR7 ligands. How cells interpret chemokine gradients and how they couple directional sensing to polarization and persistent chemotaxis has remained largely elusive. Previous experimental systems were limited in the ability to control fast de novo formation of the final gradient slope, long-lasting stability of the gradient and to expose cells to dynamic stimulation. Here, we used a combination of microfluidics and quantitative in vitro live cell imaging to elucidate the chemotactic sensing strategy of DCs. The microfluidic approach allows us to generate soluble gradients with high spatio-temporal precision and to analyze actin dynamics, cell polarization, and persistent directional migration in both static and dynamic environments. We demonstrate that directional persistence of DC migration requires steady-state characteristics of the soluble gradient instead of temporally rising CCL19 concentration, implying that spatial sensing mechanisms control chemotaxis of DCs. Kymograph analysis of actin dynamics revealed that the presence of the CCL19 gradient is essential to stabilize leading edge protrusions in DCs and to determine directionality, since both cytoskeletal polarization and persistent chemotaxis are abrogated in the range of seconds when steady-state gradients are perturbed. In contrast to Dictyostelium amoeba, DCs are unable to decode oscillatory stimulation of soluble chemokine traveling waves into a directional response toward the wave source. These findings are consistent with the notion that DCs do not employ adaptive temporal sensing strategies that discriminate temporally increasing and decreasing chemoattractant concentrations in our setting. Taken together, in our experimental system DCs do not depend on increasing absolute chemokine concentration over time to induce persistent migration and do not integrate oscillatory stimulation. The observed capability of DCs to migrate with high directional persistence in stable gradients but not when subjected to periodic temporal cues, identifies spatial sensing as a key requirement for persistent chemotaxis of DCs.

Loss of Myo19 increases metastasis by enhancing microenvironmental ROS gradient and chemotaxis

“…These cells showed high migration speed and metastatic potential (Nakamura et al, 2002 ), which were suitable for subsequent tracking and analysis. Consistent with what we observed in transwell assay, rose plot and positive forward migration index (FMI) of cell motion (Frattolin et al, 2021 ; Parr et al, 2019 ; Quast et al, 2022 ) revealed that cells migrated directionally towards higher concentration of H 2 O 2 (Fig. 4F,G ).…”

Dendritic Cell-Based Immunotherapy: The Importance of Dendritic Cell Migration

“…Through this internalization process, DCs generate a self-generated chemokine gradient. However, when chemokine gradients are low, DCs are difficult to perceive, whereas high gradients lead to receptor saturation, hindering cells from sensing spatial differences [71][72][73]. Stable gradients of CCL19 are crucial for stabilizing directionality because disruption of these gradients leads to impaired cytoskeletal polarization and persistent chemotaxis.…”