Adult versus Embryonic Stem Cells
As the debate escalated, opponents of embryonic stem cell research mined emerging scientific evidence suggesting that adult stem cells could be used in therapy. Although they show up prior to birth, adult stem cells are developmentally older, specialized cells that exist in many places in the body, biding their time before they replace old and damaged cells and the diseased tissues in which they reside. The principal difference between adult and embryonic stem cells lies in their potential to become different types of cells and tissue. Embryonic stem cells have enormous potential—they can become any cell or organ in the body. Adult stem cells, by contrast, are restricted in what they can become. As they mature, their ability to change becomes increasingly limited until they are a fully matured cell, such as a skin cell or a neuron.
Preliminary results from some adult stem cell research laboratories in late 1999 and early 2000 hinted that adult stem cells were every bit as powerful as their embryonic counterparts. Political and religious groups used this data to make the case that embryonic stem cell research was unnecessary. But other laboratories were unable to repeat the experiments, and a burst of new data refuted the original claims. As a result, few stem cell researchers today will say that adult stem cells are the sole answer for curing disease and physical dysfunction. Indeed, experts say the opposite—embryonic stem cells have tremendous therapeutic potential.
The final answers won’t come any time soon. Cures may come from other disciplines of biology and some diseases may prove too stubborn to treat. Human stem cell research is in its infancy and is extremely fluid: results published in last year’s scientific journals are quickly refuted this year. Biology yields its secrets grudgingly, and it is quite possible that a decade or more will pass before anything resembling a general theory of stem cell biology is articulated, and then only if research is allowed to proceed under open conditions. Our knowledge of human development relies on investigating both types of cells: prohibiting one line of research and not another is like asking Einstein to understand relativity without gazing at the stars or asking da Vinci to understand flight without watching birds.