In vivo proangiogenic effects of EPC-derived MV. Formation of vessels after 7 days by HMECs preincubated (30 minutes at 37°C) with 30 μg/mL of MVs and then injected subcutaneously in Matrigel in SCID mice. (A) Quantitative evaluation of angiogenesis induced by MVs or by RNase-treated MVs. Angiogenesis was evaluated as the percentage of vessel area, and data are expressed as mean (± 1 SD) of 6 experiments. Analysis of variance with Newmann-Keuls test was performed; *P < .05 MVs versus control; §P < .05 RNase MVs versus MVs. (B) Representative micrographs of hematoxylin and eosin staining of Matrigel plugs obtained by Zeiss Axioskop (Jena, Germany) using ×100 and ×250 objectives. We considered as patent vessels those connected with the murine vasculature as shown by the presence of erythrocytes in the lumen (arrows). (Scale bar, 20 μm). (C) Representative confocal micrographs (Zeiss LSM 5 Pascal confocal Laser scanning microscope equipped with an Helium/Neon 543 mm laser, an Argon 450-530 mm laser, and an EC planar NEOFluar 40×/1.3 oil DIC objective lens; acquisition software, Zeiss LSMS version 3.2) showing the expression of human HLA class I antigen and human CD31 by HMEC-formed vessels within the implanted Matrigel (scale bar, 10 μm).