The Providence Journal steals some bases in its stem-cell–related editorial today:
But amniotic stem cells, though plentiful, may not be able to develop into the full range of cell types that embryonic stem cells provide. Because they are only a few days old, embryonic cells are extremely flexible in terms of what they might become. Adult stem cells, championed as a good-enough alternative by foes of embryonic-stem-cell research, hold promising but probably limited uses (for instance, helping repair bone fractures). Difficult to extract, they are taken from living people, and considered unlikely to help with complex ailments. Amniotic cells look better, but may still fall short of what embryonic stem cells can do. …
Anthony Atala, the author of the study on amniotic fluid, has said it is “essential” that the National Institutes of Health make research dollars available for embryonic stem-cell research. He sees the amniotic-fluid approach as complementary to it, not as a replacement. For one thing, embryonic-stem-cell research is further along, and closer to being tested in humans. In moving toward possible cures, time is of the essence.
Firstly, it is imprecise to talk about “what embryonic stem cells can do.” Embryonic stem cells are not doing anything, yet. They may be “closer to being tested in humans” than once they were, but they aren’t there. Which leads to: Secondly, adult stem cells are being tested, even used, and have been for years.
I could be incorrect, but as I understand the biology, the adult stem cells are limited mainly in their ability to become only a handful of cell types, not in the practical applications that they could fill once they’ve been repurposed. But stem cells taken from different parts of the adult’s body have different ranges, so they aren’t, as a group, limited to the capabilities of any particular type.
Though I am certainly not a scientist of any sort, during my campaign I did quite a bit of research on the issue because it was a frequent debate topic.
You are correct in saying that adult stem cells; at least those derived from bone marrow, are not pluripotent. That is to say that they are not applicable across a range of tissue or disease applications. The other failing is that adult stem cells do not possess a full cell life. Thus the chance to divide throughout a complete cycle in the way that embryonic cells would is lacking, as well.
Embryonic stem cells have yet to yield a single cure. Over 60 cures can be attributed to adult cells, however. Both blood cord applications (an adult based technique that appears pluripotent) and, the more recently discovered, germ cell techniques currently hold the most promise. The major drawbacks in the embryonic applications, as your cited article notes, have been rejection in test subjects and tumor growth: neither a desirable outcome.
I will not say that I am positively against embryonic stem cell research, particularly when it comes to existing lines, but it seems to me that money well spent is money spent on methods that hold the most promise and the greatest potential return on investment.