Biology of Lymphangiogenesis in the Adult Lung

PROJECT SUMMARY/ABSTRACT The lung’s lymphatic system plays a critical role in lung health by maintaining fluid homeostasis and by serving as a conduit for immune cell trafficking. Despite the importance of this network however, there are significant knowledge gaps in the basic biology of this system and its key cellular constituent, the lymphatic endothelial cell

(LEC). For one, very little is known regarding the origin and replacement of lung LECs in adult life and how different origins and micro-anatomical locations of LECs might be associated with different roles, specifically in immune responses. Indeed, whether lung LECs comprise a heterogeneously and functionally distinct set of cell

subtypes or a largely homogenous population is unknown. After instillation of flu into the mouse left lung lobe, we observed a local and vigorous lymphangiogenic reaction manifested by early vessel dilation followed by expansion of the lymphatic network itself. This is associated with a significant 1.5-2-fold increase of LECs at 7

days post-infection (dpi) and a significant 2-3-fold increase at 21 dpi, a time when the virus is cleared. Edu labeling demonstrated that 20% of LECs are proliferating at 7 dpi vs.