FIG. 6.

Effect of hypoxia on angiogenic factor expression in amniotic fluid-derived stem (AFS) cells. AFS cells were cultured in hypoxic conditions (5% O₂) for 48 h then induced into endothelial cells by cultured in endothelial growth media-2 for 1 week. (A) Vascular endothelial growth factor (VEGF) mRNA level was significantly increased in response to hypoxia as measured by real-time RT-PCR. AFS cells produce low levels VEGF as measured by ELISA; however, AFS cells cultured in hypoxia significantly increased VEGF production. (B) After 1 week of culture in endothelial differentiation medium, the hypoxia-pretreated AFS cells (48 h, 5% O₂) showed up-regulation of VEGF in both mRNA and protein levels compared to the cells untreated with hypoxia. (C) Characterization of additional angiogenic cytokine expression in AFS cells using RT-PCR. AFS cells were positive for HGF, bFGF, and PGF, but did not express the genes of Ang-1 and eNOS. (D) Real-time RT-PCR confirmed the PGF and HGF mRNA levels were increased in hypoxia culture. The Ang-1 and eNOS showed very low expression, and the expression of bFGF was not changed by hypoxia treatment.