ILC2s promote initiation of angiogenesis by boosting angiogenic sprouting. (A) GOBP enrichment results based on the following pairwise comparisons: endothelial cells in ILC2-transferred group versus PBS group. (B) A comparison of AUCell scores for tip cells among top-scored (0.1%, 0.5%, 1%, and 5%) endothelial cells between ILC2s transfer group and PBS group, analyzed by two-sided, paired Student’s t test. *P = 0.0103. (C) Immunofluorescence of peri-ischemic region at day 5 after MCAO and ILC2s transfer (images taken at 40×). White arrowheads: tip cells and endothelial cells with filopodia. Scale bars, 50 µm (10 µm for zoomed out). (D) Immunofluorescence of peri-ischemic region at day 5 after MCAO and ILC2s transfer (images taken at 20×). Red arrowheads: connected tip cell fronts. Scale bars, 100 µm (10 µm for zoomed out). (E and F) Morphometric quantification of angiogenic sprouting and by calculating the number of tip cells and endothelial cells with filopodia per 40× view (E), as well as number of connected tip cell fronts (F). Number of views = 5 per group. Each view from one mouse brain. The bar plots were analyzed by two-sided, unpaired Student’s t test. All data represent biological replicates from two independent experiments. ***P = 0.0004; ****P < 0.0001. (G) Tip cells (white arrows) present near ILC2s (yellow arrows) peri-ischemic region at day 5 after MCAO and ILC2s transfer (images taken at 40×). Scale bars, 100 µm (20 µm for zoomed out).