The “Breaking News” alert came to my phone last night: on Monday, President Obama is planning to sign an executive order reversing the restrictions on embryonic stem cell research put in place by President Bush in 2001. This comes as a surprise to no one, as Obama made it clear that he was opposed to these restrictions throughout the 2008 presidential campaign.
The occasion of this reversal of federal policy seems to be a good time to talk a bit about stem cells. The President’s decision is sure to provoke intense debate, and this debate can only be healthy if it is based on fact, not emotion.
Let’s start with the basics. What is a stem cell?
As I discussed in a prior post, a stem cell is a primitive cell that is capable of generating more “daughter” cells with more specific function as well as making more copies of themselves. Every organ and tissue in your body contains stem cells. As the most mature cells die, they are replaced by cells derived from these “organ stem cells,” which also continuously replenish themselves. Stem cells such as these are often referred to as “adult stem cells” because they are found in adult humans. There are also “umbilical cord stem cells” which are found in the blood in the umbilical cords of newborn babies and many oncologists believe that there are “cancer stem cells” that drive the growth and spread (“metastasis”) of tumors.
The controversial cells are called “embryonic stem cells” because they are derived not from adults but from human embryos. In the process of obtaining embryonic stem cells, the embryo is destroyed.
Why all the excitement about stem cells? Because stem cells are so primitive, and their job in the body is to produce cells with a more specific function, it is believed that stem cells can be coaxed into producing virtually any other tissue type. This means that the therapeutic implications of stem cell biology are limitless.
Doctors could grow new organs to replace defective ones, and if they used the patient’s own stem cells, there would be no need to take medicines to prevent rejection. Diabetics could get a new pancreas that works instead of injecting themselves with insulin. Patients with spinal cord injuries could walk again.
So why the controversy?
Arguments about the ethics of stem cell research arise from questions about the source of the stem cells. Although “adult” stem cells can be obtained from an adult person, who can give informed consent for the procedure and who will (most likely) not be harmed by the procedure, embryonic stem cells require the destruction of an embryo. Those who believe an embryo is a human life entitled to the same protections as a child or adult argue that this amounts to murder and believe that it is unethical to murder an embryo to help treat disease in an adult.
Opponents of embryonic stem cell research believe that adult stem cells provide appropriate material for study and should be the sole focus of stem cell research.
Do they have a valid point? Maybe, but maybe not. So-called “adult stem cells” are not as primitive as embryonic stem cells. They already have some characteristics of the organ from which they are derived (liver, kidney, bone marrow…). So to make them turn into a different tissue is more complicated and more difficult. These “adult stem cells” have to first lose the characteristics of the tissue they came from and then gain the characteristics of the tissue they are being turned into. So far, doctors have been unable to accomplish this task on a large scale. Embryonic stem cells, because they are the most primitive stem cells available, should be easier to turn into the tissue of choice.
Since 2001, federally funded scientists have been forbidden to work with embryonic stem cells that were not already in existence. This has significantly limited progress in developing stem cell-based therapies. Despite this, the ban has not been all bad. As with all clouds, there was a silver lining. The limitations imposed by President Bush forced scientists to be creative. One novel source of stem cells that may not have been developed otherwise, is called “induced pluripotent stem cells,” abbreviated iPS. These are cells that do not start as stem cells but are manipulated in the lab to act like stem cells. Many scientists are as excited about the potential of iPS as they are about other stem cell types.
Clearly this is a very complex topic, and I have oversimplified a lot. The bottom line is that I am excited that the order President Obama is signing will not only open the door to new stem cell research, but may also signal a new era in science policy – an era where scientific decisions are made based on science, rather than on ideology.
The Stem Cell Thing
Stem Cells, or “A Rose By Any Other Name…”
Cancer Stem Cells and Familial Cancer Risk for Breast Cancer