Who Needs Stem Cells? Reprogramming One Adult Cell Directly into Another

We were all taught that undifferentiated embryonic cells progressively become differentiated adult cells — and that there is no turning back. Yet, we’ve known for 40 years that if the nucleus of an adult cell is placed into an enucleated egg, the genes of that adult cell are reprogrammed to an embryonic state (although such transfer has not been accomplished successfully in human cells). Then, in 2007, genes were introduced into complete adult cells — first mouse, then human — that reprogrammed adult cells into the equivalent of embryonic stem cells (JW Nov 29 2007).

Harvard researchers identified three genes that always are turned on in pancreatic β-cells. They inserted these genes into a viral vector that homed to pancreatic exocrine cells…