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

Figure 2 Hypoxia promotes cell cycle progression in human placenta-derived mesenchymal stem cells. A: Cell cycle phase distribution of human placenta-derived mesenchymal stem cells (hP-MSCs) cultured under hypoxia and normoxia for 48 h and assayed by flow cytometry; B: Graph of the cell cycle distribution. Data are means ± SD (n = 3); Student’s t-test; C: Western blotting of cyclin E1, cyclin A2, CDK2, and p21 in hP-MSCs exposed to hypoxia for 24, 48, or 72 h; D: Cyclin E1, cyclin A2, CDK2, and p21 expression levels normalized against glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Data are means ± SD (n = 3). ^aP < 0.05 and ^bP < 0.01.