Figure 3: ASC-conditioned media (ASC-CM) enhanced human umbilical vein endothelial cell (HUVEC) tube formation. Conditioned media were collected from cultured ASCs at passages 2, 4, and 6 from donors of different ages and used in a HUVEC tube formation assay. After 11 days of culture, HUVEC tube-like structures were visualized with CD31 immunostaining and photographed. (A) Representative photomicrographs of HUVEC tube-like structures in cultures treated with ASC-CM from passage 2 from donors aged 5 months (5M), 7 months (7M), 1 year (1Y), 11 years (11Y), 26 years (26Y), 60 years (60Y), 71 years (71Y), 75 years (75Y), and 82 years (82Y). Unconditioned medium was the negative control (NC), and medium containing 10 ng/ml VEGF-A was the positive control (PC). (B) Representative photomicrographs of HUVEC tube-like structures in cultures treated with ASC-CM from passage (P)2, 4, and 6 from donors aged 26 years (26Y). Scale bar: 200 μm.