Reconstructing Cell-Cell Interactions in Diverse Inflammatory Environments - SUMMARY Neutrophils, the most abundant innate immune cell type, play a critical role in clearing infections, healing wounds, and repairing damaged tissues. Our laboratory seeks to understand how diverse inflammatory signals regulate the neutrophil response to inflammation using engineered in vitro platforms designed to mimic in vivo biology with human cells. Specifically, we are interested in determining how (i) secreted inflammatory signals, (ii) multicellular interactions, and (iii) the extracellular matrix regulate neutrophil behavior with the long-term goal of identifying targets to modulate neutrophil recruitment and function to treat infections and neutrophil-associated diseases. To properly function, neutrophils must integrate the unique set of cues released by each inflammatory environment into a specific, directed, and tightly regulated response. Defective neutrophil recruitment, excessive neutrophil infiltration, or improperly controlled neutrophil function contributes to chronic infections, tissue damage, and the progression of diseases including cancer, cardiovascular disease, autoimmune disease, and fibrosis. The individual steps of the neutrophil response (activation, extravasation, migration, and antimicrobial function) are coordinated by a wide variety of secreted proinflammatory signals released by the activated vasculature, tissue resident cells, circulating cells, and pathogens; however, the different mechanisms through which each of these soluble signals and cell populations regulate neutrophil recruitment and function are undefined. Importantly, how neutrophil behavior varies in response to differing inflammatory cues and how neutrophils integrate multiple cues into a directed response remain unanswered questions. This knowledge gap exists due to the limitations of the current experimental platforms, which fail to capture the complex milieu of signals, multicellular interactions, or three-dimensional architecture of the in vivo environment. To address this challenge, we have recently developed a novel inflammation-on-a-chip device that includes key aspects of the inflammatory environment including a model blood vessel, primary human immune cells, extracellular matrix, and a source of live pathogen or proinflammatory cytokine to investigate the primary human neutrophil response in a physiologically relevant in vitro model. Over the next five years, we will exploit the modularity of our inflammation-on-a-chip device to develop a comprehensive understanding of how individual inflammatory stimuli (pathogens, pathogen-associated molecular patterns, damage-associated molecular patterns, cytokines) and interactions with varied inflammatory cell populations (endothelial cells, pericytes, macrophages, platelets) regulate neutrophil function. We will identify key signaling molecules and signaling network hubs that broadly regulate the neutrophil response or are uniquely important for the neutrophil response to individual stimuli. This work builds toward our long-term goal of identifying therapeutic targets to control neutrophil behavior for the treatment of inflammatory diseases and will advance the study of inflammation by further developing our modular, multicellular, physiologically relevant experimental model for investigating the innate immune response.
