Interesting Stem Cell Development

by hilzoy

From the Washington Post:

"A type of cell that floats freely in the amniotic fluid of pregnant women has been found to have many of the same traits as embryonic stem cells, including an ability to grow into brain, muscle and other tissues that could be used to treat a variety of diseases, scientists reported yesterday.

The cells, shed by the developing fetus and easily retrieved during routine prenatal testing, are easier to maintain in laboratory dishes than embryonic stem cells -- the highly versatile cells that come from destroyed human embryos and are at the center of a heated congressional debate that will resume this week.

Moreover, because the cells are a genetic match to the developing fetus, tissues grown from them in the laboratory will not be rejected if they are used to treat birth defects in that newborn, researchers said. Alternatively, the cells could be frozen, providing a personalized tissue bank for use later in life. (...)

"They grow fast, as fast as embryonic stem cells, and they show great pluripotentiality," meaning they can become many kinds of tissues, said study leader Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine in Winston-Salem, N.C. "But they remain stable for years without forming tumors," he added, something that embryonic cells are not very good at.

Atala and other scientists emphasized that they don't believe the cells will make embryonic stem cells irrelevant.

"There's not going to be one shoe that fits all," said Robert Lanza, scientific director at Advanced Cell Technology in Worcester, Mass. "We're going to have to see which ones are most useful for which clinical conditions."

George Daley, a Harvard stem cell researcher, echoed that sentiment. "They are not a replacement for embryonic stem cells," he said. (...)

In the laboratory, the amniotic cells can mature into all of the major types of cells, dividing at the impressive clip of once every 36 hours yet never showing signs of aging and never becoming tumors -- even after living for more than two years in the lab.

With co-workers from Wake Forest and from Children's Hospital in Boston, Atala coaxed the cells to become brain cells and injected them into the skulls of mice with diseased brains. The new cells filled in diseased areas and appeared to make new connections with nearby healthy neurons.

When coaxed to become bone cells and seeded onto a gelatin scaffold that was then implanted in a mouse, the cells calcified and turned into dense, healthy bone.

Under other conditions they became muscle, fat, blood vessel and liver cells.

Atala said that if 100,000 women donated their amniotic cells to a bank, that would provide enough cells of sufficient genetic diversity to provide immunologically compatible tissues for virtually everyone in the United States. With more than 4 million U.S. births a year, it would not take long to collect that many specimens, he said -- especially because the cells can be found not only in amniotic fluid but also in the placenta, which is discarded after birth."

(The original Nature Biotech article is here.)

If this works out -- and, needless to say, that's a big if -- it would be wonderful news. This isn't just because it would be a source of stem cells that have some of the properties of embryonic stem cells but don't require the destruction of embryos. It's also important that its source -- amniotic fluid -- is so readily available, and from so many different kinds of people. Embryonic stem cells derived from excess IVF embryos are only as diverse as couples seeking IVF, and there have been a lot of questions both about how diverse in all the usual ways those couples are, and also about what the fact that they all have one thing in common -- infertility -- means for the resulting stem cell lines. By contrast, pretty much everyone has babies. Moreover, taking samples of amniotic fluid is something a lot of people do anyways, and since amniocentesis is often beneficial and desirable for prospective parents, if it turns out that some group can't afford it, members of that group might be happy to voluntarily undergo amniocentesis in exchange for the right to derive stem cells from the amniotic fluid.

One of the moral questions raised by the prospect of stem cell therapies is: if we were to design a bank of stem cells, what lines would it include? Stem cells, like organs, have to be a good enough genetic match for the person they will be transplanted into. If a stem cell bank included the lines that would match the greatest number of people, then in the USA and Europe, it would turn out, in practice, that the vast majority of people who could get a good match would be white. If, on the other hand, we tried to provide good matches for roughly equal percentages of all ethnic groups, then the bank would be able to help fewer people. (I discuss this question here.)

This problem exists in part because the range of embryonic stem cell lines available from IVF embryos is limited, and deriving embryonic stem cells using somatic cell nuclear transfer is difficult, and likely to be quite expensive. (It also involves women donating eggs -- not, I am told, a pleasant process.) As Atala says, If we can derive stem cell lines from amniotic fluid, and if those lines can do some of the work that embryonic stem cells do, then we would have a vast, cheap and diverse source of useful stem cells. That would mean that we could construct a larger bank, and thus that the problem of the banks genetic diversity would be a lot more tractable -- at least for those diseases that could be treated by these cells.

However, as Robert Lanza said in the Post article, "There's not going to be one shoe that fits all (...) We're going to have to see which ones are most useful for which clinical conditions." -- If there's one thing I wish that everyone understood about stem cells, it's that they are not all the same. Adult stem cells are extremely different from embryonic stem cells, and if this research holds up, these new stem cells will undoubtedly be different from both. (Moreover, different lines of stem cells differ from one another -- they are not at all interchangeable.) There may be some diseases that amniotic stem cells can be used to treat; there will probably be some that still require embryonic stem cells.

Moreover, there's one thing that this research does not suggest we might use these amniotic stem cells to replace. Unfortunately, that's somatic cell nuclear transfer. SCNT promises to be extraordinarily useful for research, for reasons I detailed here. (Scroll down until you see a paragraph beginning 'The Main Issue', in bold.) Absent some reason to think that we could use amniotic cells not just to derive stem cell lines, but to do something very much like cloning, this won't replace SCNT.

But if this research holds up, it's very, very good news.

Comments

[Anderson]

Look for the Roman Catholic Church to declare the personhood of amniotic fluid.

[cleek]

as usual, i have nothing intelligent to say, so i'll just remark that there is a town in NC called Stem , pop 238.

[Sebastian Holsclaw]

I don't really understand why the RC church would object. It doesn't interfere with the fetus.

[Yukoner]

Sebastian,
As I understand it, taking amniotic fluid poses a measurable risk of causing an abortion.

[Sebastian Holsclaw]

Measurable, or significant? That is the question that makes me crazy. Lots of risks are measurable, and lots of lawsuits happen because of that fact. But that doesn't make them significant. :)

[Yukoner]

To follow up, I understand that the process of sampling amniotic fluid results in an unintended abortion in 1 out of 200 instances. This is what my wife and I were told when we were expecting children and, given my wife's age, were offered the test to determine whether the fetus had a variety congenital abnormalities. Given that the risks of those abnormalities being present were considerably lower than 1 in 200, the decision not to have the test was easy.

I don't know what the Catholic Church thinks of the apparently now routine prenatal sampling of amniotic fluid, but given that its primary purpose is to determine whether to abort the fetus and that it induces abortions itself, I cannot imagine that the Church would look favourably on it.

[dutchmarbel]

I also didn't have amnotic fluid samples taken due to the risc.
It seems slightly weird to promote something that might cause an abortion with 20 weeks to save an embryo.

[heet]

Late in commenting but two things -
1. Very interesting writeup, hilzoy. I've thought for a while that the pressure from moral objection will make for some interesting science.

2. The decision to do an amnio depends on some complicated computations (for my math challenged mind, anyhow). The include such factors as - What is the false positive rate for the alternative tests? Spontaneous abortion risk for those tests? What is the rate of spontaneous abortion at the gestation age? What treatment, if any, are you prepared to carry out if the test is positive for whatever you are looking for? What is the chance the treatment works? Kills the fetus? Will the information help the parents down the road to decide on conceiving another child?

The bottom line is - does the risk outweigh the benefit (of course). For example, if you suspect Down's (from imaging and mother age) but the amnio results won't alter the the course, you'd be crazy to put the fetus at risk.