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.