Chemotactic activity of rh-sCD146 in vitro and in vivo. (A) Microscopic examination of Matrigel plugs maintained for 12 days in normal mice. Matrigel plugs containing 0.1 μg/μL PBS (control), 0.1 μg/μL c-myc peptide, or 0.1 μg/μL rh-sCD146 were injected in the same mouse. Capillary-like structures were observed in the Matrigel plugs in the presence of rh-sCD146 (arrows) but not in control or c-myc–containing plugs. (B) Immunostainings were performed with anti-CD45, anti-CD34, anti–α-SMA, anti–MOMA-2, anti-CD31, and anti-CD117 antibodies on sections of Matrigel plugs filled with rh-sCD146 and maintained for 12 days in normal mice. Nuclei were labeled with DAPI (blue). Colabelings were also performed with CD31/CD146, CD117/CD31, CD117/CD146, CD117/CD33, and CD117/CD45. The merge pictures are given. Yellow areas correspond to a colabeling. In some pictures, these areas are better indicated with an arrow. (C) EPC characterization. EPCs were characterized by flow cytometry analysis for their expression of CD31, CD146, CD117, CD33, and CD45. Markers are represented in clear and control isotypes in dark. (D) Chemotactic effect of rh-sCD146 on EPCs in vitro. rh-sCD146, c-myc, immunodepleted rh-sCD146 (Ip rh-sCD146), control immunodepletion (IpC), and VEGF were tested. Results are the mean ± SEM values of 4 different experiments. *P < .05, **P < .01, ***P < .001, experimental versus control. (E) Immunostaining of Matrigel plugs maintained for 12 days in nude mice injected with late EPCs. Control Matrigel plugs containing 0.1 μg/μL c-myc peptide and Matrigel plugs containing 0.1 μg/μL rh-sCD146 were injected in the same mouse. Immunostaining was performed in Matrigel plugs with anti–human CD31 (red) antibody. Cell nuclei were labeled with DAPI (blue).