title: Microfluidic system for measuring neutrophil migratory responses to fast switches of chemical gradients.
abstract: Experimental systems that provide temporal and spatial control of chemical gradients are required for probing into the complex mechanisms of eukaryotic cell chemotaxis. However, no current technique can simultaneously generate stable chemical gradients and allow fast gradient changes. We developed a microfluidic system with microstructured membranes for exposing neutrophils to fast and precise changes between stable, linear gradients of the known chemoattractant Interleukin-8 (IL-8). We observed that rapidly lowering the average concentration of IL-8 within a gradient, while preserving the direction of the gradient, resulted in temporary neutrophil depolarization. Fast reversal of the gradient direction while increasing or decreasing the average concentration also resulted in temporary depolarization. Neutrophils adapted and maintained their directional motility, only when the average gradient concentration was increased and the direction of the gradient preserved. Based on these observations we propose a two-component temporal sensing mechanism that uses variations of chemokine concentration averaged over the entire cell surface and localized at the leading edge, respectively, and directs neutrophil responses to changes in their chemical microenvironment.
authors.affiliation: BioMEMS Resource Center, Center for Engineering in Medicine and Surgical Services, Massachusetts General Hospital, Shriners Hospital for Children, and Harvard Medical School, Boston, MA 02114, USA. dirimia@hms.harvard.edu
authors.forename: Daniel
authors.initials: D
authors.lastname: Irimia
authors.forename: Su-Yang
authors.initials: SY
authors.lastname: Liu
authors.forename: William G
authors.initials: WG
authors.lastname: Tharp
authors.forename: Azadeh
authors.initials: A
authors.lastname: Samadani
authors.forename: Mehmet
authors.initials: M
authors.lastname: Toner
authors.forename: Mark C
authors.initials: MC
authors.lastname: Poznansky
mesh_terms: D002633:Chemotaxis / Q000187:drug effects*; D004867:Equipment Design; D006801:Humans; D016209:Interleukin-8 / Q000737:chemistry / Q000494:pharmacology*; D008297:Male; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation*; D009504:Neutrophils / Q000737:chemistry / Q000187:drug effects* / Q000502:physiology
chemical_list: D016209:Interleukin-8