Like an out of control youth, embryonic stem cells can wreak havoc with tissue damage and tumor formation. Their inability to make appropriate, mature cells that can function in an adult body is also a problem.

Scientists at UCLA have found that cells derived from pluripotent stem cells are developmentally very immature, and do not resemble the adult cell types that they would theoretically replace in a transplant. The immaturity was seen in cell derivatives from both embryonic stem cells and induced pluripotent stem (iPS) cells. The data indicate that pluripotent stem cells such as embryonic stem cells are inappropriate substitutes for adult stem cells in patient treatment...