sHLA-G1 inhibits FGF2-mediated HUVEC capillary tubule-like formation. (A) In vitro tubule-like capacity of HUVECs. HUVECs were seeded on Matrigel in the absence (UT, untreated) or presence of FGF2 (10 ng/mL) and after the addition of sG1 or sG1mono (1 μg/mL). Photographs of each well were taken after 24 hours, and angiogenesis was quantified as described in “Materials and methods.” Data are representative of 5 separate experiments, each performed in triplicate. After sG1 treatment, the branches and tubules formed were less developed than in sG1mono-treated or untreated HUVECs. (B) Branches from each cell were counted from 1 representative field per well. Data indicate the mean ± SEM of 3 wells and are representative of 5 independent experiments. Images were visualized using a Nikon Eclipse E-800 microscope equipped with a Plan Apo 4×/0.2 NA objective. Images were acquired using a Nikon DXM-1200F camera with Nikon ACT-1 software, and were processed using Morphoexpert software version 2.5 (Explora Nova). ^***P < .001, ANOVA.