Figure 4From: Erythropoietin and the effect of oxygen during proliferation and differentiation of human neural progenitor cellsMetabolic activity of hNPCs. Effect of oxygen tension on the metabolic activity of differentiating hNPCs. Cells differentiated for 24 h or 72 h either at 20% (A, C, E, black bars) or 3% O2 (B, D, E, white bars). EPO was applied with the onset of differentiation at various concentrations (10 - 300 IU/ml). Treatment with EPO resulted in a significant increase of the absorbance from 25 IU/ml onwards at 20% O2 (n = 3-7) and 100 IU/ml at 3% O2 (n = 3-6) indicating a higher metabolic activity of cells after one day of differentiation (A, B). Samples treated with EPO and differentiated for 3 days showed similar absorbance levels at 20% (n = 3-4) and 3% oxygen (n = 3-4), whereas the increase of absorbance levels after EPO treatment were not any longer significant. Cultivation of untreated cells at low oxygen concentration resulted in a 2.4 fold increase of the absorbance after one day of differentiation and a 1.7 fold increase after 3 days of differentiation (E), indicating a higher metabolic activity (n = 4-6), compared to controls. (F) includes the metabolic activity of proliferating cells for comparison with differentiated cells (E). * p < 0.05, **p < 0.01.Back to article page