For years, Dr. Clive Svendsen at the University of Wisconsin has sought to use human stem cells as biological pumps that can be implanted inside the human body where they will pump out drugs to cure diseases. Svendsen is particularly interested in GDNF – a neurotrophic chemical that may help prevent or slow the degeneration of neurons – for dealing with diseases like Parkinson’s or ALS.
Now, Dr. Charles Murtaugh at the University of Utah has entered the game. Just as Svendsen wants to insert stem cells into the brain or muscle to produce GDNF, Murtaugh wants to insert stem cells into the pancreas to produce insulin so diabetes sufferers will no longer have to carry around mechanical pumps. The pumps will be inside, instead, using the body’s resources to operate as little biological engines.
This would solve at least one of the challenges facing other approaches to creating insulin producing cells. A team led by Dr. Lawrence Chan at Baylor recently used genetic engineering techniques to transform liver cells into insulin producers in mice. The problem: they used gene therapy via a retrovirus to change the cells, a technique that has occasionally resulted in death when tested in humans. Dr. Murtaugh’s approach would get around the problem by genetically engineering the stem cells outside the body and then re-implanting them.
The idea of biological pumps is one of the more exciting ideas floating around in stem cell land, because you could potentially use them for just about any drug that can be coded for by DNA. So long as you can insert the gene for the protein in question into the stem cell, it will produce whatever protein you want. But I want to use them here to raise a second point.
Stem-cell-based biological pumps are an excellent example of the argument that there is very little difference in terms of skills and instrumentation required for medical therapies and for other, non-medical purposes in the realm of stem cells. Once Svendsen has developed a genetically modified neural stem cell capable of producing GDNF after being successfully implanted in the human brain, there is essentially no barrier to using the same technology to permanently implant stem cells in the brain capable of generating other DNA-derivable proteins that aren’t related to disease.
This raises a fundamental challenge to the logic under which stem cells currently are being sold. Stem cell research, according to the arguments put forward by researchers and the Obama Administration, is all about curing diseases. On the other hand, if stem cell techniques can be used for purposes other than medical therapies, then we enter into a much more complex moral, ethical and policy terrain. The question then becomes: to what ends should we put stem cells?
In recent decades, courts in various parts of the United States required
that recidivist criminals be implanted with Norplant, in certain cases,
in order to ensure they would have no more children. Prisons reportedly
use mental health drugs to maintain docile prison populations. What would
a state bent on ensuring social order do with the capacity to permanently
alter people’s internal body chemistry in ways that suited the state’s purposes?
What would a society bent on ensuring its own safety insist that the state
do? What might individuals seeking better athletic or cognitive performance
be willing to buy if it were sold? And if we can do it, how would we prevent
it from being sold, somewhere in the world?
I have not yet been convinced that this observation is sufficient to call
for halting all stem cell use. The medical benefits of stem cells may turn
out to be significant (if, as Michael Crow, ASU president, observes in the
Spring 2009 Issues
in Science and Technology, we can figure out how to better link
health research to health outcomes).
What I do suggest, however, is that we begin a public dialogue today about the proper ends to which we put stem cells.
About the Author: Clark Miller is associate director of CSPO.
