Spatially Resolved Heterogeneity of Lymphatic Vasculature in the Adult Lung

BACKGROUND: Lung lymphatic drainage of interstitial fluid is essential for preventing pulmonary edema, a condition characterized by the accumulation of extravascular fluid that impedes respiratory gas exchange and can be fatal. Beyond fluid regulation, lung lymphatics also serve as conduits for immune cell trafficking, supporting both surveillance and mounting of host immune responses during lung infection. Despite their essential roles, the cellular and functional heterogeneity of lung lymphatic endothelial cells (LECs) remains poorly defined. METHODS: Leveraging single-nucleus sequencing technology, we investigated LEC heterogeneity in the homeostatic adult mouse lung. RESULTS: We identified Stab2 (stabilin-2), a class H scavenger receptor, as a unique marker of a distinct subset of LECs in lymphatic vessels adjacent to pulmonary veins and in alveolar regions. A separate, distinct subset of LECs is defined by expression of Pkhd1l1 (polycystic kidney and hepatic disease 1-like-1), a component of stereocilia, and these lymphatic vessels are localized to the bronchovascular bundle. CONCLUSIONS: Our findings suggest that lung LECs are not a uniform population but instead comprise molecularly distinct and spatially organized lymphatic vessels, possibly with specialized functions. These results lay the groundwork for further studies geared toward understanding the roles of cellular origin in lung LEC heterogeneity, whether lymphatics in other organs have analogous spatial organization, and whether these disparate cells and vessels have functional differences in fluid homeostasis and immune regulation during pulmonary disease pathogenesis.