Single-cell RNA-seq of the mouse lymph node lymphatic vasculature: Droplet-seq

Lymph nodes (LNs) serve as hubs for the interaction and communication between tissue-derived and blood-derived immune cells. Here we analyzed mouse lymph node (LN) lymphatic endothelial cells (LEC) at single cell resolution. Clustering identifies five well-delineated subsets, including two medullary sinus subsets not recognized previously as distinct. Nearest neighbor alignments in trajectory space position the major subsets in a sequence that recapitulates known and suggests novel features of LN lymphatic organization, providing a transcriptional map of the lymphatic endothelial niches and of the transitions between them. Differences in gene expression reveal specialized programs for (1) subcapsular ceiling endothelial interactions with the capsule connective tissue and cells, (2) subcapsular floor regulation of lymph borne cell entry into the LN parenchyma and antigen presentation, and (3) medullary subset specialization for pathogen interactions and LN remodeling. LEC of the subcapsular sinus floor and medulla, which represent major sites of cell entry and exit from the LN parenchyma respectively, respond robustly to oxazolone inflammation challenge with enriched signaling pathways that converge on both innate and adaptive immune responses. Overall design: Male and female 6- to 8-week-old BALB/cJ or 8- to 12-week-old C57BL/6J peripheral LNs (inguinal, axillary and brachial) were processed by the 10x Genomics workflow and used for scRNA-seq.