Matrix Confinement Plays a Pivotal Role in Regulating Neutrophil-generated Tractions, Speed, and Integrin Utilization

Abstract

Background: Neutrophils must generate well regulated forces to migrate within the confined, three-dimensional space of diseased tissues. Results: Spatial confinement induces a switch to integrin-independent motility, but integrins regulate three-dimensional traction force generation. Conclusion: Physical confinement is sufficient to induce integrin-independent motility. Significance: Spatially confined double hydrogels are a biomimetic system that may allow for ex vivo testing of neutrophilspecific therapeutics.

Mean deformation metrics for quantifying 3D cell–matrix interactions without requiring information about matrix material properties

“…Such behavior is indicative of a contractile, integrin-dependent mode of motility as opposed to a pushing, or integrin-independent mechanism (38). These observations are consistent with recent findings showing that integrins continue to play a significant regulatory role for traction generation and motility under confinement in the presence of ligands (39). Using the simple MDM, we detect statistically significant differences between naïve and LPS-activated human neutrophils.…”

“…Confocal image stacks of 512 × 512 × 128 voxels (108 × 108 × 38 μm 3 ) were recorded every 2-3 min with a z-step of 0.30 μm. To ensure physiological imaging conditions within the imaging chamber, temperature was controlled at 37°C as previously described (17,39). For reflectance microscopy, an APO 40× water immersion objective (NA = 1.15; Nikon) with z-step = 0.25 μm was used to obtain typical imaging volumes of 167 × 167 × 81 voxels (52 × 52 × 20 μm 3 ).…”

“…Neutrophils were isolated from healthy human volunteers using previously established protocols (39). Institutional review board approval was obtained from the Rhode Island Hospital's Committee on Protection of Human Subjects to allow donation of venous blood.…”

Leading from the Back: The Role of the Uropod in Neutrophil Polarization and Migration

“…Studies have shown that in vivo talin is not required for neutrophil motility (Lammermann et al, 2013); however in 3D in vitro gels, neutrophil directed migration to a gradient of chemoattractant was impaired in talin-deficient neutrophil-like cells (Yamahashi et al, 2015). Interestingly, in a more recent study, Toyjanova et al showed that spatial confinement of neutrophils is sufficient to cause a switch to integrin-independent motility (Toyjanova et al, 2015), It has also been shown that in similar confined environments mesenchymal cancer cells are capable of adopting a fast moving amoeboid-like mode of migration (Liu et al, 2015b). This finding might provide insight into the mesenchymal to amoeboid transition seen in some migrating cancer cells (Friedl and Wolf, 2003), and raises interesting questions about the role of a uropod-like rear in the more rapid migration of cancer cells.…”

Leukocyte transendothelial migration: A local affair

“…Actin polymerization in the leukocyte elicits pulling and pushing forces that support the movement through the confined endothelial pore. [63][64][65] The docking structure A widely observed phenomenon associated with leukocyte TEM is the formation of endothelial membrane protrusions rich in Filamentous (F)-actin that surround transmigrating leukocytes. These endothelial structures were first described by Barreiro and colleagues who defined them as docking structures.…”