Figure 5.

Kinetics of expression of Oct4‐, Nanog‐, and Notch1‐specific messages in hESCs during short‐ and long‐term hypoxic exposure by real‐time RT‐PCR. The CLS1 and CLS2 hESCs lines were grown in the normoxic conditions of ambient air or in short‐term hypoxia of 5% oxygen concentration. CLS1‐LT and CLS2‐LT cell lines, that have previously been maintained in long‐term (>18 months) hypoxic conditions corresponding to 5% oxygen, have also been sub‐cultured in 5% oxygen for 4 weeks. For the analysis in normoxic conditions, the differentiated and undifferentiated parts of the colonies were separated from feeder layer. In hypoxic conditions, whole, feeder‐free, colonies were analysed. The expression levels were normalized to the undifferentiated cells from control cultures at the first week. The error bars denote standard error of mean and they are shown only in positive direction. Asterisks indicate a significant difference (P < 0.05). undif, undifferentiated; dif, differentiated; hESC, human embryonic stem cell.