Court lifts cloud over embryonic stem cells

Researchers are keen to compare induced pluripotent stem cells (pictured) with their embryonic cousins.

SILVIA RICCARDI/SPL

The US Supreme Courts decision last week to throw out a lawsuit that would have blocked federal funding of all research on human embryonic stem cells cleared the gloom that has hung over the field for more than three years. Yet the biggest boost from the decision might go not to work on embryonic stem (ES) cells, but to studies of their upstart cousins, induced pluripotent stem (iPS) cells, which are created by reprogramming adult cells into a stem-cell-like state.

At first glance, iPS-cell research needs no help. Researchers flocked to the field soon after a recipe for deriving the cells from adult mouse cells was announced in 2006, partly because this offered a way to skirt the thorny ethical issues raised by extracting cells from human embryos. But the real allure of iPS cells was the promise of genetically matched tissues. Adult cells taken from a patient could be used to create stem cells that would, in turn, generate perfectly matched specialized tissues replacement neurons, say for cell therapy. Although the number of published papers from iPS-cell research has not yet caught up with that of ES-cell work (see Inducing a juggernaut), US funding for each approach is now roughly matched at about US$120 million a year.

C. T. Scott et al. Cell 145, 820826 (2011)

But, as iPS cells crop up in ever more labs, ES cells generally cheaper, better behaved and backed by an extra decades worth of data promise to have an important supporting role. Ever since iPS cells were described, researchers have been trying to understand just how similar they are to ES cells. iPS cells begin with different patterns of gene expression, and they can also acquire mutations during the reprogramming process, which means that every iPS cell must be thoroughly evaluated before it can be used in any study. Human ES cells will always be the standard to which other cells will be compared, says Roger Pedersen, who studies how stem cells retain embryo-like states at the University of Cambridge, UK.

Federally supported ES-cell research was shut down in the United States on 23August 2010, a year after a lawsuit was filed by two opponents of human ES-cell research, and remained frozen for more than two weeks (see Fifteen years of controversy). Many investigators shied away from the field for fear of having to shut down again. The Supreme Courts move has reassured investigators such as Candace Kerr, who studies early development of the brain at the University of Maryland School of Medicine in Baltimore. As a young scientist working towards tenure, she felt particularly vulnerable to the threat of ES-cell funding being stopped. So she switched to iPS cells in 2010, while the lawsuit was working its way through the US court system. With the litigation over, she says she need not hesitate or fear adding to her work with experiments using ES cells, which she finds much easier to prompt into neurons than iPS cells. I am excited and relieved by this decision, she says.

The tussles over whether or not US federal funds can be used for research involving human embryonic stem cells have a long history.

November 1998 Paper announces the isolation of embryonic stem (ES) cells from human embryos.

August 2001 US President George W. Bush restricts federal funding for work on human ES cells to a few extant lines.

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Court lifts cloud over embryonic stem cells