Understanding Immune-Stromal Interactions in Tissue Homeostasis and Inflammation

SUMMARY In tissues, immune cells are well-organized spatially and perform specific functions to dictate tissue homeostasis and inflammation. Yet, it is rarely understood how the organization and functions of immune cells are regulated by their surrounding tissue stroma. The overall vision of the lab is to elucidate the impacts and mechanisms of the interactions between immune and non-immune cell types, in order to understand general principles of how immune functions are regulated within tissues. This may ultimately lead us to program immune responses to restore tissue homeostasis from disease. The lab has discovered that macrophages and fibroblasts, two cell types that are commonly present in mammalian tissues, self-assemble into a tissue-like system that maintains a stable and robust population composition. These homeostatic features rely on paracrine communication of growth factors and direct contact between these cells. This macrophage-fibroblast system provides a unique, accessible and modular platform to discover immune functions in the cellular context of stromal cells and to dissect the underlying mechanisms. Our published and preliminary data formulate the overall hypothesis of the lab: distinct cellular responses emerge from the interactions between macrophages and fibroblasts. The goal of the lab in the next five years is to identify the cellular and molecular bases of the interactions between macrophages and fibroblasts and to characterize how these interactions regulate immune responses during tissue homeostasis or inflammation. We aim to elucidate general principles that regulate functions and organization of immune cells in tissues, by developing new methods to study their interactions and interactive partners, discovering interaction receptors to perturb them, and defining cellular functions dependent on such interactions. To reach this goal, 3 directions will be pursued in my lab: 1) develop fucosyl-labeling, a new cell- based chemical genetic approach, to identify cell-cell interactions, 2) identify molecules responsible for the physical association between macrophages and fibroblasts, leveraging candidate-based genetic approaches, 3) determine how the interactions between macrophages and fibroblasts impact their cellular responses under inflammatory conditions using transcriptome profiling, imaging and immunological assays. Research proposed in this application is innovative because it presents a comprehensive strategy to directly tackle the mechanistic nature of immune-stromal interactions, combined with exploration of a new research paradigm and the development of cutting-edge technologies that will have a fundamental impact in basic cell biology and immunology. The proposed research is significant because it will identify the cellular mechanisms that regulate immune functions critical for maintaining tissue homeostasis and regulating inflammatory responses. My lab will advance our knowledge of inter-cellular processes that may lead to inflammatory disorders and define new possible therapeutic targets. The reagents, tools and experimental systems developed here will benefit the broad scientific community to explore multi-cellular interactions.