Intelligently debate stem cell research with the facts.
By Tiffiny Carlson
No one wants to get into a debate about stem cell research, with the heady cloud of controversy surrounding it, only to end up looking like an uneducated halfwit. No matter which side you’re on, you should at least get the basic facts right.
What is a stem cell, anyway?
Here’s the low-down: The body is made up of billions of cells doing all sorts of different jobs: blood cells, brain cells, nerve cells, skin cells and on and on and on. Stem cells, on the other hand, are undifferentiated: they are, in effect, blank canvasses. Some day soon, most researchers believe, they will unlock the genetic code that will enable them to coax a stem cell to become almost any kind of cell they want it to be.
And this is why researchers were so excited when James Thompson, at the University of Wisconsin- Madison, was able to derive the first human embryonic stem cell line in 1998. Before this breakthrough, the existence of stem cells was known (adult stem cells derived from bone marrow have been used to treat leukemia in humans since 1968), but up until that point no one had been able to successfully isolate human embryonic stem cells which could then be studied.
The existence of stem cells was first posited in 1908, but it wasn’t until 1963 when Canadian researchers Ernest A. McCulloch and James E. Till were able to prove that the hematopoietic (blood-forming) cells in mammals (mice to be exact) were in fact indefinitely self-renewing (i.e., were stem cells).
With all of the huge embryonic and adult stem cell advancements made in the past ten years, it’s no wonder researchers are salivating with excitement over regenerative medicine being so close to becoming a reality.
How do adult stem cells and embryonic stem cells really differ?
The core difference between adult stem cells and embryonic stem cells is that embryonic stem cells are derived from human embryos, whereas adult stem cells are derived from mature body tissue (typically from bone marrow, umbilical blood, and olfactory cells).
Embryonic stem cells for use in research and therapy are extracted from the mass of cells inside the blastocyst of a newly developing embryo, then placed in a nourishing medium and carefully monitored to ensure that they remain healthy, continue to divide and do not differentiate.
Adult stem cells, on the other hand, are found in mature tissue in the body. Their job is to maintain and repair the organ and/or tissue in which they are found. Think of them as backup players on the body’s football team.
Are adult stem cells as powerful as embryonic stem cells?
The simple answer: no. The ability of embryonic stem cells, once isolated, to be grown indefinitely and to theoretically become a range of cells is called their pluripotency, from the Latin for “most” (as in most cells but not all) and “powerful.” Adult stem cells, in contrast, are multipotent: they can be turned into just a small range of differentiated cells. According to most researchers, since adult stem cells are already situated in their respective organs and tissues, the possibility of their being as fluidly unspecialized as embryonic stem cells is doubtful.
In 2006, however, researchers discovered that through genetic reprogramming, adult stem cells can be induced to be pluripotent. It is not yet clear what properties these induced pluripotent stem cells (iPSCs) share (or do not share) with embryonic stem cells or how safe they are; altering their genetic structure risks rendering the cells highly carcinogenic. But in 2008, Sheng Ding and colleagues showed that pluripotency could be induced chemically and without changing the cell’s genetic structure. Researchers all over the world are working feverishly to determine if these iPSCs will make a suitably safe and ethically unambiguous alternative to embryonic stem cells.
Why do many people object to using embryonic stem cells for therapy or research?
Human embryonic stem cells are derived from among the 30 to 35 cells in the inner cell mass of a five-day-old blastocyst selected from the excess embryos typically discarded during in vitro fertilization. Because the integrity of the embryo is compromised, this process essentially kills it. Many religious people and some bioethicists object that this constitutes killing a potential human being. Researchers counter that these embryos would have been destroyed anyway, while the stem cell that lives on has the potential to improve the lives of millions directly through therapy and indirectly through research.
A common additional objection to the use of embryonic stem cells is that their promise is just that: promise. They argue that money used to support embryonic stem cell research could be better spent on proven therapies, including even adult stem cell therapy. Research, however, is essential to the discovery or perfection of new treatments, even in adult stem cell therapy: recent studies have shown that mature human ependymal stem cells (from the lining of the spinal cord) have been transplanted to the spinal cords of paralyzed rats, enabling them to regenerate damaged neural pathways and restore some function. But researchers argue that outlawing embryonic stem cell research in the US when so many important discoveries are being made so rapidly around the world is short-sighted, irresponsible and contrary to the spirit of scientific inquiry.
Must an embryo be destroyed for embryonic stem cells to be extracted?
Yes and no. The first human embryonic stem cells for research were taken, with the consent of their donors, from surplus embryos generated during the in vitro fertilization process. Since then, and especially since President Bush banned federal funding of research using new stem cell lines in 2001, most researchers in the US have been working with the descendent cells from those 22 early lines. But in March of 2009, President Obama lifted the ban on new stem cell lines, and just last December, the National Institutes of Health approved the first 13 new lines, clearing the way for researchers to receive millions of federal dollars in the coming year.
Meanwhile, researchers are still hard at work looking for extraction methods that may one day leave the rest of the embryo intact. In 2006, Advanced Cell Technology, a biotech company based in Massachusetts, showed it was possible to remove a single embryonic stem cell from an embryo before it was implanted into a women’s fetus. Don’t hold your breath, though. This research is still in its infancy.
For further accurate and upto- date stem cell information, visit any of the following sites:
- The National Institutes of Health’s Stem Cell Information site: stemcells.nih.gov/info/basics/
- Stem Cells: What they are and what they do: www.mayoclinic. com/health/stem-cells/ CA00081
- Stem Cells at the National Acadamies: www.nas.edu/stemcells
Tiffiny Carlson writes frequently for Action.
