Plasma factor Xa levels and expression of heparanase in murine endothelial cells. (A) Active factor X levels were examined in plasma of End.p53-WT and End.p53-KO mice, aged 12 weeks (adult) or 12 months (aged), as described in “Methods.” Graphs show individual values as well as the mean ± SEM per group. **P < .01 and ***P < .001. Primary endothelial cells were isolated from lungs of adult and aged WT mice and examined for the expression of (B) heparanase (Hpse), (C) Egr1, and (D) the endothelial marker Cd31 (n = 4 biological replicates per group). (E) Representative western blot membrane. Vena cava segments were obtained from adult and aged End.p53-WT and End.p53-KO mice, cryoembedded and examined for the expression of Egr1 (F) or Hpse (G; green signal) and Cd31 (red signal) using immunofluorescence. Representative confocal microscopy images are shown. Scale bars represent 10 µm.