Overexpression of the 8 TFs in HUVECs conveys an arterial-like behavior upon their implantation in a Matrigel plug in vivo. Overexpression of the 8 TFs in HUVECs results in a more significant arteriogenic capacity in a subcutaneous Matrigel implant. (A-D) Fluorescent micrographs of Matrigel implants containing HUVECs (revealed by the Cherry signal in red; indicated by white arrowheads) transduced with a control vector (A,C) or with the combination of the 8 TFs (B,D). Panels A-B represent the ex vivo nonsectioned Matrigel explant, and panels C-D represent frozen cross sections. (E-G) Frozen cross sections from Matrigels containing control HUVECs (E; white bars in G) or HUVECs transduced with the 8 TFs (F; black bars in G) stained with αSMA (green), and the corresponding quantification (G) showing the percentage of HUVEC-containing (revealed by the Cherry signal) vessels coated with αSMA⁺ cells (*P < .05 vs control). (H-J) Cross section from a Matrigel containing HUVECs transduced with 8 TFs stained with human-specific CD31 (red) and αSMA (green) and the corresponding overlay (J). An autofluorescent erythrocyte is indicated by a dashed ellipse. (K-M) Cross sections from a Matrigel containing control HUVECs (K; white bar in M) or HUVECs transduced with 8 TFs (L; black bar in M) stained with αSMA (green) and the corresponding quantification (M), showing the relative αSMA⁺ area (^#P = .08 vs control). (N-P) Cross sections from a Matrigel containing control HUVECs (N; white bar in P) or HUVECs transduced with 8 TFs (O; black bar in P) stained with Sirius red (visualized under polarized light) and the corresponding quantification (P), showing the relative Sirius red–positive area (*P < .05 vs control). Dashed white lines indicate the inner edge of the fibrous Matrigel capsule. 4,6 Diamidino-2-phenylindole (blue) is used as nuclear counterstain in panels E, F, and H-L. Scale bars: 100 μm in A-D, 10 μm in E-F and H-J, and 200 μm in K-L and N-O.