Stem cell biology and its complications

New York Times: “A few years ago, two groups of researchers . . . discovered that all they had to do was add four genes and a cell would reprogram itself back to its original state when it was a stem cell in an embryo. Like an embryonic stem cell, that reprogrammed cell seemed to be able to then turn into the many kinds of specialized cells in the body, an ability called pluripotent. What has happened since that discovery, scientists say, is that stem cell biology turned out to be more complicated than they anticipated. Besides the stem cells from embryos, there are so-called adult stem cells found in all tissues but with limited potential because they can only turn into cells from their tissue of origin. And there are these newer cells made by reprogramming mature cells. Now researchers are trying to figure out whether stem cells made by this reprogramming process really are the same as ones taken from embryos.”