A long term study of human stem cell types has shown that tissue-derived human stem cells performed poorly and are more likely to die prematurely than their human embryo-derived stem cell counterparts.The research, lead by leading stem cell scientist Robert Lanza, M.D., compared the growth and differentiation characteristics of what are called induced pluripotent stem cells (iPSC) with those of human embryonic stem cells (hESC). Induced pluripotent stem cells are derived from adult tissue taken from certain organs of the body, including the liver or bone marrow, while hESC are derived from the cell mass of four- to five-day old human embryos. Both are capable of growing into most any organ cell, though iPSC are somewhat limited in the types of cells they can become.

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