Microfluidics to define leukocyte migration patterns

Leukocyte migration into tissues is characteristic of inflammation. In this thesis, we design and validate microfluidic devices that allow for precise quantification of leukocyte migration patterns. Our microfluidic platform can quantify migration patterns using single-cell quantitative metrics that include the percentage of cells migrating, their directionality, persistence and migratory speed. We used these microfluidic platforms to perform mechanistic studies on bi-directional migration and also to screen for anti-inflammatory mediators. We also studied the effects of the neuronal guidance cue Netrin-1 on CD4+ T cell migration and validated our in vitro findings using a humanized SCID mouse model. We found that Netrin-1 augmented leukocyte infiltration and skin inflammation and that its effects were functionally associated with the expression of the promigratory Netrin-1 receptor neogenin on lymphoctyes. We used a maze device to study migration signatures of both T cells and neutrophils and identified two dominant migratory patterns which we called exploratory migration patterns and highly directional end-target directed responses. Finally, we explored novel mechanisms by which leukocytes can cause tissue damage through the formation of neutrophil extracellular traps (NETs). We found that NETs perturb blood flow in microcapillaries-on-a-chip, despite the presence of anti-coagulants and show that the impedance of blood flow can be reversed within seconds using DNase. The work presented in this thesis shows that microfluidic devices have significant potential to be adapted as tissue-chips that mimic the tissue microenvironment. Chip design can be used to study therapeutic interventions in a wide variety of diseases and clinical conditions