Live-cell fluorescence imaging identifies bona fide reprogrammed cells.

The next tools for reprogramming cells to an embryonic-like state might just be a camera and a set of fluorescently tagged antibodies.

Researchers imaged more than a million human cells in vitro as they changed from skin tissue cells, known as fibroblasts, into colonies of induced pluripotent stem (iPS) cells. As expected, many similar-looking colonies appeared, but only very few consisted of fully reprogrammed iPS cells. After assessing which were which, researchers led by Thorsten Schlaeger and George Daley of the Harvard Stem Cell Institute in Cambridge, Massachusetts went back and worked out how to predict which colonies would produce high-quality iPS cell lines by analyzing the images.

Robert Blelloch, who studies reprogramming at the University of California San Francisco, sees immediate practical applications. "It means that you can focus down on the most promising colonies and not assay everything." Currently, he says, many evaluations of techniques to boost reprogramming rates lump some partially reprogrammed cells together with fully reprogrammed ones. With better markers of pluripotency, he says, "you can look at the dish and count" and be more confident of your results.

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