(A) Number of statistically significant ligand-receptor pairs (LRPs, from CellPhoneDB (Efremova et al., 2020), STAR Methods) between pairs of ChP cell types, across ventricles in adult (top) and aged (bottom, embryo in Figure S7A). Significant pairs of cell types based on a randomization test marked as: *p≤0.05, **p≤0.01, ***p≤0.001. (B) Differential LRPs across ventricles or ages. Middle bar: cell types expressing the ligand (color coded). Right/left bars: cell types expressing the corresponding receptor. Edge width: Number of LRPs in each cell type pair that are specific to the specific ventricle (top) or age (bottom). Edge color: cell-type (middle bar). (C-E) Selected ventricle-dependent and age-dependent LRPs. Median expression level in expressing cells (color) and proportion of expressing cells (circle size) in major cell population, across all ventricles (color coded) and ages (top: E16.5; middle: adult; bottom: aged). Dashed square: ventricle-dependent expression, solid line: age-dependent. Aging-dependent IL-1β-IL1R1 signaling (in E). (F) IL-1β immunostained macrophage in vessel like structures connecting ChP and brain parenchyma in aged brain. Inset: IL-1B macrophage. (G)
Left: Whole mount aged hindbrain. Dotted lines outline 4V ChP. Right: IL1R1 immunostained endothelial cells (PECAM1) . Arrowheads: IL1R1+ blood vessels originating from the brain parenchyma and entering the ChP. See also Figure S7.