Stem cells might be easier to commercialize as tools for drug development, an area in which the new technology seems especially promising. But iPS cells still hold many unknowns: they are not as well studied as embryonic stem cells, and there is not yet any standard by which they can be measured. That is one reason no one is yet willing to claim that iPS cells will make embryonic stem cells obsolete; indeed, the inconsistency of iPS cells is one of the biggest research hang-ups at the moment. Researchers don’t quite understand why, but even cells from the same batch can behave very differently. Some are easy to turn into other tissues; some are stubborn. And the rapidly growing repertoire of methods for making iPS cells is adding to the variability.
Only a year ago, researchers had to use a virus to insert the four proteins required to turn an adult cell into an iPS cell. The virus also inserted little bits of itself into the cell’s genome, an invasion that not only prevents therapeutic use but makes lab studies much less reliable. Newer methods use proteins or chemicals, while some techniques still use viruses. Before they can use the cells generated in all these different ways, scientists need to study and document their characteristics. “We just finished initial characterization of a group of 12 lines we made. And then we made some more,” says Jeanne Loring, director of the Center of Regenerative Medicine at Scripps. “So we’re suffering from the same thing everyone else is.” In other words: “Oh my God, we have more lines than we know what to do with.”
But Harvard’s Melton, for one, thinks these problems are only temporary. “This is all solvable in the short term–in the next year or so,” he says. After that, the trick will be figuring out how to prompt the cells to differentiate in the desired ways. There are more than 200 different kinds of cells in the body, and although iPS cells have the potential to turn into any of them, actually getting them to do so is a different story. “How do you tell a cell to become a pancreatic beta cell? How do you tell it to become a four-grain basal cell or a motor neuron?” he says. Scientists have already figured out how to make some neurons and blood cells, to name a few. But they cannot yet efficiently make such important types as pancreatic beta cells, the insulin producers that are destroyed in diabetes. Still, says Melton, “we’re getting closer.”
Though it seems a long way off, scientists still hold out the possibility that iPS-cell technology could one day be used for treatment. “The near-term value for iPS cells is in disease modeling, pathway identification, and drug screening and development,” says George Daley, a stem-cell biologist at Harvard University and Children’s Hospital in Boston. “But I don’t give up hope that we will generate cells that will have therapeutic relevance.”
For now, though, iZumi and other companies are focusing sharply on what they think will be the most immediate use of iPS cells: as tools for understanding some of our most devastating diseases and finding better ways to treat them. The new technology, they hope, will fundamentally change the repetitive, variations-on-a-theme approach to drug development that has hindered pharmaceutical progress in recent years. The discoveries it makes possible could one day transform medicine into something we’re only just beginning to imagine.
Lauren Gravitz is a freelance writer based in Los Angeles, CA.