issue guide: Stem Cell Research

Background & Facts

see also the skinny, pro & con, links

What stem cells are and what the big scientific deal is

Stem cells are “blank slate” or root cells that spawn and develop into adult cells. All stem cells share two characteristics: they can divide and create new cells indefinitely (as opposed to most of our grown-up cells which have limited splitting potential); and they can morph into different types of cells. (A more detailed primer can be found at NIH.)

Stem cells make up early embryos but can also be found on the gonad region of older embryos (the area that develops into reproductive organs), on umbilical cords and in you (for example, in your bone marrow where stem cells create a steady stream of new blood cells).

While stem cells hold great potential for understanding disease (such as cancer), what most excites researchers is their potential to be used in therapies to cure certain diseases, most notably Parkinson's, Alzheimer's and diabetes. In those therapies, stem cells could be used to replace or take over the role of the poorly functioning, or nonfunctioning, cells that cause the disease - and in essence become a cure.

Not all stem cells are created equal

Some stem cells show greater potential to cure disease than others; although, with recent research, there's growing debate on how much difference in potential there really is (see adult stem cells below).

Scientists break down the potential of stem cells into three levels:

  • Pluripotent stem cells can give rise to any type of cell in the body (except those needed to develop a fetus).

  • Multipotent stem cells can develop into a small number of different cell types.

  • The third class are fertilized eggs. They're considered totipotent, meaning that their potential is total, since they give rise to all the different types of cells in the body.

Depending on where stem cells come from they have different potentials and different limits for federally funded research:

  • Embryonic Stem (ES) Cells are the stem cells that all the fuss is about. ES cells are cells from the very first stage of the embryo – when it is 3-5 days old and has divided into about 200 cells. ES cells have generally been thought to be pluripotent and so offer great development potential.

  • Embryonic Germ (EG) Cells are taken from the “gonadal ridge” of aborted fetuses five-nine weeks old. They are the cells that would have gone on to form sperm or egg cells in an adult. Like ES cells, they are thought to have great potential. Unlike ES cells, federally funded research using EG cells is not barred, although donations of fetuses have to follow other federal guidelines (WH).

  • Adult stem cells are found in different parts of adults (or children, for that matter). Unlike embryonic stem and germ cells, they are already somewhat specialized, so while they give rise to different types of cells, they have less potential to become any type of cell. With that said, recent studies suggest that adult stem cells may hold more potential than earlier thought – but while some adult stem cells have shown potential to morph into any cell, the stem cell lines they create may have shorter lives.

  • Umbilical cord blood stem cells have similar potential to adult stem cells.

The promise – what and when will stem cells save the day, if ever

Today, the only stem cells that are actively and successfully used to treat illness are adult stem cells. Adult stem cells in bone marrow - which create blood cells - can be transferred to cancer patients whose own supply of healthy bone marrow has dwindled (NIH). New techniques are also used to treat other blood diseases (NIH) and some diabetes and kidney cancer patients.

It is the future of stem cell research, however, that gets scientists jazzed. By studying stem cells, scientists hope to get a better understanding of how developmental diseases and cancers work. Even more exciting to the medical community are the promises of using stem cells to treat disease. Some of the most commonly sited examples are Parkinson's, Alzheimer's and diabetes. In those diseases, where a patient's cells stop functioning properly, stem cells could be used as tissue grafts to take over the role of non-functioning cells.

Although most medical scientists agree stem cell reasearch holds great promise, what's not clear is when the promises of that research will become reality. There are a few hurdles. Embryonic stem cells haven't proved easy tools to work with, as there have been problems in getting the cells to differentiate properly, as well as problems in making sure that they do not multiply in an undifferentiated way, in effect, turning into a cancer.

So when can we expect results? No one really says. Even advocates of embryonic stem cell research say major cures may be 5 - 10 years away (WP).
Another researcher - this one from Harvard - suggests that current patients will likely not benefit from stem cell research, with some diabetes patients being a possible exception (WP).

Embryonic vs. Adult

Most agree that embryonic stem cells show more potential than adult stem cells - including the National Institute of Health - but recent research with adult stem cells show they may be gaining ground.

For example, researchers have induced blood-forming stem cells in bone marrow to differentiate into brain and kidney cells, and induced neural cells to differentiate into blood cells. (Cornell) Recent experiments at Tufts University also suggest that adult stem cells may be able to morph into any kind of cell. (WP)

But again, like the question of when there will be a successful cure, it's almost impossible to say exactly how much more potential embryonic stem cells have, although some - such as the Berman Bioethics Institute at John's Hopkins argue it's considerable.

(Note on the NIH - although they're a government agency, they've been fairly open in their disagreement with the administration on the question of stem cell research.)

The law on research and federal funding

Dickey amendment

Bush's well publicized decision in 2001 to limit federally funded research on stem cells did not come out of the blue. What's lost in much of the talk about stem cell research is that his decision was in large part a clarification of a policy put into place in 1995. In that year, Congress added the “Dickey amendment” to its budget saying federal funds cannot be used for “research in which a human embryo or embryos are destroyed, discarded or knowingly subjected to risk of injury or death.” The Dickey amendment has been tacked onto spending bills every year since. (WH)

Before Bush came to office, the Clinton administration was looking at ways to fund the popular research - and still remain within the law. Their solution was to allow federally funded research on embryonic stem cells as long as the funding was not used to do the actual destroying - in other words, stem cell lines that were bought from private companies were okay to fund research on. This didn't go down well with some social conservatives and ethicists; they objected that there's not much difference between destroying embryos and, in essence, paying a private company to do it for you.

Bush's compromise (or straddle, depending on your view)

Bush stepped into office before the Clinton policy could go into effect - and put the kibosh on it. Instead, he proposed the current policy as a compromise between the researchers and the ethicists; in that proposal federal funds could be used to do research on embryonic stem cells that were already in existence - that is, where the embryo had already been destroyed. But federal funds could not be used on cell lines from embryos destroyed after the policy went into effect. The reasoning was that federal funds wouldn't be encouraging the destruction of any more embryos.

Stem cell lines

Once stem cells are removed (from the embryo, bone marrow, etc.),they can be used to create stem cell "lines" - cell cultures that can be grown indefinitely in the laboratory. Once a stem cell line is established, it is essentially immortal, and a researcher using the line will not have to go through the rigorous procedure necessary to isolate stem cells again.

Even though as many as 78 cell lines could qualify for fed funded research (WH), only 22 have made it through the red tape and development hurdles to be available by the end of 2004 (Pew). Recent studies suggest that many of those lines may also be contaminated with sialic acid (AP) or may be mutating (WP).

How much is being spent

  • Embryonic stem cell research by the feds:

    • $25 million in 2003 (WP) or $17 million out of $20 billion of all funding for biomedical research (WH)

  • Adult stem cell research by the feds:

    • $191 million in 2003 (WP)

  • Embryonic stem cell research by private companies spent

    • About $70 million in 2002 (WH)

  • States: California plans to spend $3 billion over 10 years on embryonic stem cell research (or about $300 million a year) (NYT) Three other states that have set aside funds for embryonic stem cell research as well: Connecticut ($100 million); New Jersey ($150 million) and Illinois ($10 million) (NYT)

New developments

In May 2005, a bioethics panel appointed by Bush suggested four ways to access embryonic stem cells without destroying an embryo: using fertilized eggs that had lost their ability to grow, essentially becoming “dead” embryos; interfering with a cloning process to create embryonic stem cells without ever creating an embryo; removing stem cells from embryos without harming the embryos; and the last, tinkering with adult cells to get them to revert to full potential stem cell status.

The methods were proposed as ways to satisfy ethicists who have concerns about destroying viable embryos. (WP) Nonetheless, some ethicists find these methods problematic: for example, in the first method, they say it's not always possible to determine which embryos have stopped growing; the second method brings up its own ethical questions of creating quasi-human creations. (WH) The new methods are also currently scientific stretches so they'd need more time and research before producing results, although progress continues to be made, in particular in coaxing stem cells out of adult cells.

A fifth approach - fusing an adult cell with an existing embryonic stem cell to create individualized stem cell lines - is also being developed and could satisfy ethicists from all sides (WP). Also, in 2006, researchers successfully grew a heart valve using stem cells from the amniotic fluid in the womb (Reuters).

Proposals in Congress

The House, in 2005, and the Senate, in 2006, passed a bill that would open up stem cell research to lines of cells created after 2001, provided those cells a) came from in vitro clinics and b) were originally meant for fertility purposes but now no longer have the potential to be used for that purpose so would otherwise be discarded. (WP) The president, however, vetoed the bill and Congress wasn't able to override the veto. (WP)

Updated November 30, 2007.

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