Hypoxic conditioning enhances the angiogenic paracrine activity of human adipose-derived stem cells

• Published in: Stem cells and development Vol. 22; no. 10; p. 1614
• Main Authors: Hsiao, Sarah T, Lokmic, Zerina, Peshavariya, Hitesh, Abberton, Keren M, Dusting, Gregory J, Lim, Shiang Y, Dilley, Rodney J
• Format: Journal Article
• Language: English
• Published: United States 15.05.2013
• Subjects: Adipose Tissue - cytology; Animals; Cell Hypoxia - drug effects; Culture Media, Conditioned - pharmacology; Humans; Male; Mice; Mice, Inbred C57BL; Neovascularization, Physiologic - drug effects; Oxygen - pharmacology; Paracrine Communication - drug effects; Ribonuclease, Pancreatic - genetics; Ribonuclease, Pancreatic - metabolism; Stem Cells - cytology; Stem Cells - drug effects; Stem Cells - metabolism; Vascular Endothelial Growth Factor A - genetics; Vascular Endothelial Growth Factor A - metabolism; Vascular Endothelial Growth Factor C - genetics; Vascular Endothelial Growth Factor C - metabolism
• ISSN: 1557-8534
• DOI: 10.1089/scd.2012.0602

Human adipose-derived stem cells (ASCs) secrete cytokines and growth factors that can be harnessed in a paracrine fashion for promotion of angiogenesis, cell survival, and activation of endogenous stem cells. We recently showed that hypoxia is a powerful stimulus for an angiogenic activity from ASCs in vitro and here we investigate the biological significance of this paracrine activity in an in vivo angiogenesis model. A single in vitro exposure of ASCs to severe hypoxia (<0.1% O2) significantly increased both the transcriptional and translational level of the vascular endothelial growth factor-A (VEGF-A) and angiogenin (ANG). The angiogenicity of the ASC-conditioned medium (ASC(CM)) was assessed by implanting ASC(CM)-treated polyvinyl alcohol sponges subcutaneously for 2 weeks in mice. The morphometric analysis of anti-CD31-immunolabeled sponge sections demonstrated an increased angiogenesis with hypoxic ASC(CM) treatment compared to normoxic control ASC(CM) treatment (percentage vascular volume; 6.0%±0.5% in the hypoxic ASC(CM) vs. 4.1%±0.7% in the normoxic ASC(CM), P<0.05). Reduction of VEGF-A and ANG levels in the ASC(CM) with respective neutralizing antibodies before sponge implantation showed a significantly diminished angiogenic response (3.5%±0.5% in anti-VEGF-A treated, 3.2%±0.7% in anti-ANG treated, and 3.5%±0.6% in anti-VEGF-A/ANG treated). Further, both the normoxic and hypoxic ASC(CM) were able to sustain in vivo lymphangiogenesis in sponges. Collectively, the model demonstrated that the increased paracrine production of the VEGF-A and ANG in hypoxic-conditioned ASCs in vitro translated to an in vivo effect with a favorable biological significance. These results further illustrate the potential for utilization of an in vitro optimized ASC(CM) for in vivo angiogenesis-related applications as an effective cell-free technology.