Hypoxia-inducible factor-1α–mediated upregulation of CD99 promotes the proliferation of placental mesenchymal stem cells by regulating ERK1/2

Figure 1 Effect of hypoxia on human placenta-derived mesenchymal stem cell proliferation. A: Western blotting of hypoxia-inducible factor 1α (HIF-1α) in human placenta-derived mesenchymal stem cells (hP-MSCs) exposed to hypoxia for 6, 12, 24, 48, 72, or 96 h with normalization against glyceraldehyde-3-phosphate dehydrogenase (GAPDH); B: Proliferation of hP-MSCs under hypoxia and normoxia. Data are means ± SD (n = 4); C: Growth of hP-MSCs under hypoxia and normoxia as visualized by optical microscopy (× 4 magnification; scale bars, 100 μm); D: Proliferation rates of hP-MSCs determined by 5-ethynyl-20-deoxyuridine flow cytometry in triplicate and repeated in three independent experiments. OD: Optical density; FITC: Fluorescein isothiocyanate.