For me the stem cells are some sort of a magical Wolverine regeneration sauce. Never understood why they even work.
The biggest problem is that you'd like a whole tank of stem cells that you could dip some injured person into and have them come out fully repaired, but getting stem cells to multiply without turning into anything in particular is a challenge so we have to cultivate them in very small quantities and it's relatively slow and expensive to do that.
I'll have a pilsener, please.
But yeah, they're almost magic, except we understand it. Which is probably why large sectors of the religious public finds them so abhorrent: they take away yet another arrow from the inscrutable Fate they worship, they lift another bit of veil from the mystery of our existence. And it's a shame, because the objective need for strict regulation will be hampered by constant calls for pointless bans.
No, that's completely and totally not it. Folks oppose embryonic stem cell research because they believe both that embryos are human beings and that innocent human beings should not be killed. That's it.
Note that Mr. Bush continued to fund adult stem cell research, and continued to fund research on existing stem cell lines; what he didn't do was continue to fund the destruction of more embryos.
You may disagree with the idea that an embryo is a human being, and you may disagree that innocent human beings should not be killed, but you mayn't be uncharitable to your opponents.
Essentially, rather than stopping the cells from making "what I want to be when I grow up" decisions, you're taking a grown-up cell and forcing it to forget all the decisions that its predecessors ever made. It's a bit more difficult.
In general, those decisions are recorded on the nuclear DNA by "tagging" it with methyl groups, like customizing a dictionary by using paper clips to bond together the pages that are least frequently accessed. You can look up the words you frequently need much faster, but you lose the ability to look up anything else in the clipped-together pages.
If you take one of those dictionaries, and remove all the paper clips, it's back to being a completely generalist reference, almost just like a new dictionary, that had never been customized in the first place. The most notable difference is that the old dictionary might have accumulated some damage over the years.
Furthermore, there is a differentiation hierarchy. Some cells only make a few decisions. So even if you can't suck fresh stem cells out of embyros or umbilical cords, there is the possibility that you could liposuction some adipose tissue, separate out the least-differentiated cells, and inject them into other tissues. Those cells could possibly repair bone, cartilage, and ligaments. Or you could crack open baby teeth, or suck out bone marrow, and produce different types of cells. With nerve cells, though, you're out of luck, because there's really no reservoir of cells that can be harvested.
So you take some of those liposuctioned fat cells, chemically treat them to remove all the clips from their respective dictionaries, and try to make them switch to nerve cells by attaching new clips to different pages. Those cells will be cells with your own DNA, but it might just be old, damaged DNA that can't make certain proteins correctly any more.
Our adult cells communicate with their immediate neighbors through some pretty complex chemical signalling, and stem cells are receptive to that. It's one of the reasons stem cells are able to cooperatively develop from one single cell into a complex multi-cellular organism. Each stem cell carries the complete blueprints for a human being, it just needs to access and activate them based on the signals from it's neighbors.
In fact, pregnant mothers have been found to have fetal stem cells in their blood stream, which target areas of injury and are thought to be repairing them, even within the brain.
I in no way intend this to be an argument against embryonic stem cells. I just find it to be extraordinarily interesting and an intriguing avenue for further development.
More info here: https://en.wikipedia.org/wiki/Induced_pluripotent_stem_cell
(1) Your body has to create brand new stem cells for your baby, right? Why can't we do this same procedure in the lab?
(2) When stem cells are injected, how much does it matter if it's your own stem cells, a relative's stem cells, or a random person's stem cells?
For instance, as an embryo, you start as a single cell, it divides, eventually some of those cells need to start specializing, but until then they all have the potential to be any type.