Stem cells have been an endless source of fascination and controversy since Dolly the sheep was cloned in 1996. This month’s announcement of a cloned human embryo from a single skin cell came on the heels of Sir John B. Gurdon and Dr. Shinya Yamanaka’s receipt of the 2012 Nobel for Physiology and Medicine for their work with induced pluripotent stem cells. Pluripotent stem cells can be embryonic or induced. Embryonic stem cells (ESCs) can generally be obtained from human embryos or by cloning embryos through somatic cell nuclear transfer (SCNT), as was done for Dolly. Gurdon and Yamanaka demonstrated that pluripotent cells may also be formed by reprogramming adult cells to an embryonic state, resulting in induced pluripotent stem (iPS) cells without having to use eggs or cloning, or destroy embryos. However derived, pluripotent cells are capable of differentiating into virtually any cell type in the human body. This imbues them with great promise for scientific breakthroughs and medical advances, but also raises serious ethical, legal and safety concerns about their use
