Oxygen levels in the lab can permanently alter human embryonic stem (ES) cells, specifically inducing X chromosome inactivation in female cells, according to Whitehead Institute researchers
Human ES cells have been routinely created and maintained at atmospheric levels of oxygen, which is about 20%. Cells in the body are usually exposed to only 1-9% oxygen.
"When human ES cells are isolated at 20% oxygen, they are stressed and they inactivate one X chromosome in female cells," says Founding Whitehead Member Rudolf Jaenisch. "This argues that the conventional way to make human ES cells is not optimal. We're not saying our method is the only way or the best possible way, but it is better than the conventional method."
These results are published in this week's online issue of Cell.
Scientists are interested in human ES cells because they have the ability to mature into almost any cell type in the body, a trait known as pluripotency. Theoretically, this potential could be used to treat diseases or injuries.
"Also, human ES cells are the only tool we have to study the beginning of human development," says Maisam Mitalipova, Director of the Whitehead Human Stem Cell Facility and designer of the study reported in Cell.
But human ES cells, even from the same cell lines, have been yielding different results in experiments. Inconsistent results may call into question an experiment's methods or conclusions.