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Since 2007, a new type of human stem cell has been available for research study. The inducible pluripotent stem cell, or iPS cell, can go on to develop into any cell type of the body. Its source is a reprogrammed adult cell, not an embryonic cell (ES). When iPS cells were first created, many within scientific laboratories and certainly those external to the bench thought iPS cells would be the solution to the thorny issues surrounding the harvesting of embryonic sources of stem cells. They may in fact prove to be so.

But until researchers can find a way to determine the quality of an iPS line – as compared to the gold standard ES cell line – research is bound to be muddied by inherent differences between them. Before investing the time and money into studying the potential of iPS cell lines, a tool is needed to hedge some bets – to make an a priori assessment of the quality and characteristics of any iPS cell line.

Earlier this month, researchers at the ӳ����ý published a in Cell describing a means of scoring the quality of at least 12 iPS cell lines. Referencing back to ES cells, they created a system to measure the quality and indeed the ability of iPS cells to differentiate into a particular cell type. In this case, they selected cell lines that would make motor neurons. Some were indistinguishable from the ES gold standard. But others performed very differently than ES cells. (Read the news story ). “This is why the state of iPS research has been so confusing,” says co-author Alexander Meissner, assistant professor at Harvard University and senior associate member at the ӳ����ý. “It depends on what cell lines you chose to pick for your investigation.”

This analysis does not seek to resolve if either ES cells or iPS cells are the preferred stem cell. But having a scorecard method available to scout the candidates should help even the playing field.