Fig. 4

Internalization of USC-Exo by HUVECs promotes their angiogenic activities. a PKH26-labeled USC-Exo uptake by HUVECs was assessed by confocal microscopy. Scale bar, 20 μm. b Representative image of the Ki67 staining results after USC-Exo stimulation. Proliferative cells were stained red with Ki67. Scale bar, 20 μm. c After cultivation with USC-Exo, the number of CD31 Ki67 double-positive cells significantly increased. d Representative images of HUVEC tube formation in vitro after USC-Exo treatment. e Quantitative evaluation of the number of total loops, branch points, and total tube length after treating HUVECs with USC-Exo. f Representative images of HUVEC migration in the PBS and USC-Exo treatment groups in the scratch assay. g The percentage of migration area calculated for the USC-Exo or PBS treatment groups shown in f. The data are presented as the means ± SD; n = 6 per group. *p < 0.05, **p < 0.01 compared among different treatment groups