RESEARCH ARTICLE Hypoxia Enhances Proliferation of Human Adipose-Derived Stem Cells via HIF-1ɑ Activation

Background Adipose tissue-derived stem cells (ASCs) have been recently isolated from human subcuta-neous adipose tissue. ASCs may be useful in regenerative medicine as an alternative to bone marrow-derived stem cells. Changes in the oxygen concentration influence physiolog-ical activities, such as stem cell proliferation. However, the effects of the oxygen concentra-tion on ASCs remain unclear. In the present study, the effects of hypoxia on ASC proliferation were examined. Methods Normal human adipose tissue was collected from the lower abdomen, and ASCs were pre-pared with collagenase treatment. The ASCs were cultured in hypoxic (1%) or normoxic (20%) conditions. Cell proliferation was investigated in the presence or absence of inhibitors of various potentially important kinases. Hypoxia inducible factor (HIF)-1α expression and MAP kinase phosphorylation in the hypoxic culture were determined with western blotting. In addition, the mRNA expression of vascular endothelial growth factor (VEGF) and fibro