Two new studies by Harvard stem cell labs have shown that human induced pluripotent stem cells (iPSCs) are the equivalent of human embryonic stem cells for the purpose of reconstructing certain key types of cells, including neurons.

IPS cells are derived by reprogramming adult cells, and are distinct from embryonic stem cells, which are derived from a fertilized human embryo.

Kevin Eggan, associate professor of stem cell and regenerative biology, and his team derived a set of 16 new iPSC lines and tested these cell lines for “pluripotency.” This term refers to the ability of a particular stem cell to differentiate into any cell type in the body.

According to the study, published in “Nature Biotechnology” earlier this month, all 16 of the iPSC lines eventually passed a test for pluripotency and developed into functional motor neurons similar in efficiency to those produced by embryonic cells.

A cutting-edge test for pluripotency developed by the lab of Assistant Professor of Stem Cell and Regenerative Biology Alexander Meissner corroborated Eggan’s results, showing that iPSC lines are comparable in functionality to embryonic stem cell lines.

Using this new assay, Meissner’s group tested and compared the pluripotencies of 12 of the new iPSC lines generated by Eggan’s lab against 20 embryonic stem cell lines.

The researchers established a baseline with which biologists can compare new cell lines, allowing them to analyze differences in variation and to predict the differentiation efficiency of each line. The study was published early this month in the journal “Cell.”

Meissner said that the study showed considerable internal variation within both the iPSC and human embryonic stem cell lines, but found no systematic difference between the two types of cells.

“The assay lets us now conclude that there is no fundamental problem with iPS cells, and we can differentiate which cell lines [within both types] are good and which are bad,” Meissner said.

He added that the new assay method, which is patent-pending, allows for a faster, more efficient way to test new cell lines.

The current accepted test for pluripotency in new human cell lines is known as a “teratoma assay,” which is relatively slow, inaccurate, and cost-intensive, according to Meissner.

A teratoma assay can take up to two months and can only test one cell line at a time. Under the new assay method, which takes about two weeks, researchers can test many cell lines at once, Meissner said.