Stem cell research applications and outcomes

Stem Cell Ethics

Debating the Ethics of Stem Cells

The term 'stem cells' can mean different things to different people. For some, it conjures images of medical miracles providing solutions for heart disease, diabetes, and dementia. For others, it terrifies with a future filled with cloned humans. Still others cringe at the thought of mass producing cultured human embryos for the sole purpose of providing organs and tissues for a paying public. As with most complex issues, news media coverage tends to exaggerate easily understood concepts at the expense of the overall truth and the public accordingly remains ignorant of the subtleties surrounding this debate. This seems to add fuel the emergence of polarized camps and a shrinking of a common middle ground. To better define this middle ground, this essay will discuss both sides of this debate and argue instead that the vast majority of people would likely support an intermediate approach to stem cell research because it makes the most sense once the subtleties are understood.

Background

Stem Cells can be divided into several categories based on the technology used to generate them and the source from which the stem cells are derived (Ritz 5). Embryonic stem (ES) cells are derived from fertilized human embryos at a very early stage of development, at what is called the blastocyst stage of human development. Adult stem (AS) cells are typically derived from the bone marrow or umbilical cord blood, but recent research has shown that many tissues throughout the body contain small numbers of stem cells which are still too rare to harvest in significant numbers. A third kind of stem cell, one generated within the laboratory by forced expression of gene products that turn back the clock to a more primative cell type, is called an induced pluripotent stem (iPS) cell (Leeb et al. 10; Power and Rasko, 710-711). iPS are generating a lot of excitement because they can be created from adult cells taken from a skin biopsy and instructed to become various cell types, such as bone, liver, or brain cells.

Of these three types of stem cells, only ES cells have raised ethical concerns because they are derived from otherwise viable human embryos. The use of ES cells for producing organs and tissues on a mass scale would require harvesting cells from viable human embryos on a mass scale. In addition, this technology could potentially open the door to human cloning. For this reason, some have called for total ban on the use of ES cells for research and medicine.

Stem Cell Debate

The fear that stem cell research could lead to the mass production of human embryos to create a reliable source of organs and tissues (therapeutic cloning) was voiced by Antiniou, in response to the UK government approving the use of ES cells in research and medicine. ES cells are derived from a human oocyte (egg) that has been fertilized with human sperm in the laboratory (Ritz 5). As the embryo develops, an inner mass of cells is generated through repeated cell divisions; cells which can potentially give rise to any cell type in the adult body. It is this pluripotency, or the ability to produce a large number of different cell types, that has caused some researchers and clinicians to become excited about the potential medical uses that this technology might offer; however, this is also the reason for Antiniou's concern (397). The vision of tissue and organ factories exploiting the fate of unborn human beings is, in his view, just cause for reversing the decision by the UK government.

To support his view, Antiniou discusses the potential promises of AS cells (398). AS cells are derived from bone marrow and umbilical cord blood, and have begun to show promise in providing some of the same medical miracles that ES cells seem to promise, but without the ethical concerns. In light of the potential promise that AS cell technology seem to offer, Antiniou has no qualms about stating that the use of embryonic stem cells is tantamount to treating human embryos as a biological product, much like penicillin is. The solution offered by Antiniou is to ban human cloning globally before allowing the use of embryonic stem cells in research and medicine. Unfortunately, his view of AS cells and what they promise is a little simplistic.

Those that would oppose a ban on ES cell research take a different approach to the ethics debate. Leeb and colleagues, and Power and Rasko, avoid taking a position in terms of ethics by describing in detail the various subtleties surrounding stem cell research technologies. This approach leaves the ethics debate to informed readers and policy makers, while unfortunately providing information that is too complex for non-scientists to fully comprehend. These authors acknowledge the potential value inherent in the pluripotency of ES cells, while at the same time moderating this excitement with significant drawbacks that may not be so easily overcome. For example, tissues and organs generated from ES cells would still trigger an immune response from many recipient patients, as is the case currently for transplant patients receiving organs and tissues from adult donors (Leeb et al. 9; Power and Rasko, 709). As with todays transplant patients, those receiving heterologous (immune incompatible) ES cell-derived organs and tissues would also have to take immune suppressing drugs for the rest of their lives. The only advantage ES cells seem to provide in this case is a larger supply of tissues and organs.

Another major concern surrounding ES cells is their ability to produce teratomas, which are tumors of various types (Leep et al. 9; Power and Rasko, 709). The often-cited advantage of ES cells, their pluripotency, also seems to render these cells capable of generating inappropriate cell types that can grow in an uncontrolled manner. Because the growth characteristics of these cells are so unpredictable and hard to control, the clinical use of ES cells is extremely rare.

Although there are ways to get around these obstacles, they have yet to be implemented on a large enough scale to make a significant difference in medicine. Any impact that ES cells may be capable of making through therapeutic cloning is therefore still far off into the future. In the meantime, significant advances are being made in two other areas of stem cell research that may make the use of ES cells for medical therapies largely unnecessary.

AS cells are immune from the same ethical concerns that surround ES cells, because they are harvested from consenting adults (Leeb et al. 10; Power and Rasko 707). The harvesting of bone marrow, although painful, can produce a significant number of hematopoietic stem cells that can generate many of the cell types found in the blood, including red blood cells and various immune cells. Also found in bone marrow and umbilical cord blood are mesenchymal stem cells, which can generate bone cells, fat cells, skin cells, brain cells, and muscle cells. AS cells probably represent the best approach for future clinical applications, because the medical and research community has been using these cells in various ways for decades and they pose little to no cancer risk.

The use of iPS cells for medical therapies is also free of ethical concerns. iPS cells are generated in a culture dish by infecting skin fibroblast cells with four viruses that carry the genes necessary to revert them to a pluripotent stem cell (Leeb et al. 10; Power and Rasko, 710-711). However, iPS cells pose some of the same challenges that ES cells pose. First, the use of viruses to transform these cells into stem cells represents a possible disease risk for patients. In addition, two of the genes used to transform these cells are known to promote cancer. These limitations must therefore be overcome before iPS cells are medically viable.