Ang1 promotes the EC population but reduces the HSC and VSMC populations during Flk-1⁺ MPC differentiation. Flk-1⁺ MPCs were purified on E4.5 and cultured on OP9 cells. Control or Ang1 was administered on days 0, 2, and 4, and analyses were performed on days 1.5, 3, and 6. (A,C,E) Representative FACS analyses of the populations of CD31⁺/CD144⁺ ECs, CD45⁺ HSCs, and α-SMA⁺ VSMCs. Numbers indicate percentages of ECs, HSCs and VSMCs. (B,D,F) Comparison of percentages of CD31⁺/CD144⁺ ECs, CD45⁺ HSCs, and α-SMA⁺ VSMCs over time (n = 5). *P < .01 compared with control.