Blocking platelet activation mitigates Pdpn^−/− vascular defects. (A) Overview of strategy to block platelet activation: the pregnant dam was treated once daily (green arrows) by oral gavage, and embryos were harvested at E12.5 (blue arrow). (B) Platelet aggregation analysis from treated pregnant dams before embryo harvest. (C) Gross images of embryo heads, showing hemorrhages (arrows). Numbers represent embryos with bleeding (red)/total embryos (white). (D) Confocal images of forebrain vasculature and bleed areas (arrows). IB4, vessel; TER119, red cells. (E) Bar graph represents quantification of all diencephalon vascular sprouts from PNVP; n, number of embryos. (F) Bar graphs represent percentage of eMks with high, medium, or low ANGPT-1 threshold levels after a 30-minute treatment with either vehicle or 30 μmol aspirin + 10 μmol ticagrelor and then a 30-minute static adhesion on plates containing PDPN, COL-1, or both. Below are corresponding confocal images of representative eMks. Data represent means ± standard error of the mean; n, number of experimental repeats, with 3 technical repeats each. Scale bars, 500 μm (D) and 10 μm (F). **P < .01.