Inflammation-on-a-chip – High-throughput microscale arrays for human neutrophil swarming

Recorded On: 02/07/2018

Neutrophil swarms protect healthy tissues by sealing off sites of infection. In the absence of swarming, microbial invasion of surrounding tissues can result in severe infections. Recent observations in animal models have shown that swarming requires rapid neutrophil responses and well-choreographed neutrophil migration patterns. However, in animal models, physical access to the molecular signals coordinating neutrophil activities during swarming is limited. Here, we report the development and validation of large microscale arrays of targets for the study of human neutrophils during swarming ex vivo. We characterized the synchronized growth of thousands of swarms at once, towards live-microbe and microbe-like synthetic particles simulating infections.  We took advantage of the synchronized swarming in small volumes to analyze in detail the mediators released at different phases of human-neutrophil swarming against various targets. We found that the mediators coordinating human-neutrophil swarming form a complex network, with multiple levels of redundancy, which includes more than 40 signaling proteins, i.e. stimulatory of neutrophil activity, proteolytic enzymes and enzyme inhibitors, activators of other immune and non-immune cells (monocytes, lymphocytes, endothelial cells, adipocytes, etc).  We identified only one mediator that limits the growth of neutrophil swarms, LAX4, which is a lipid and has been associated before with the restoration of immune homeostasis.  We compared the swarming behavior of neutrophils from patients following major trauma and healthy individuals and found various deficiencies that resolve over time.  Overall, we report a new platform technology for studying neutrophil swarming, a behavior that is relevant to various disease and physiologic processes, and which could serve as discovery and validation platform for novel anti-inflammatory and anti-microbial treatments. 

Daniel Irimia

Harvard Medical School - Massachusetts General Hospital

microfluidics, neutrophils, inflammation, sepsis

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