Stem cells are set apart from other types of cells primarily by two characteristics: self-renewal (the ability to divide indefinitely) and potency (the ability to become different types of specialized cells, such as a muscle cell or a skin cell). These qualities make stem cells interesting to researchers today, and it’s easy to understand why: studying these cells enables scientists to learn more about cell properties and to create model cell or organ systems in which they may test new treatments. Even more exciting is the potential stem cells have in regenerative medicine—stem cells have the ability to facilitate repair mechanisms in diseased organs, to be used as a tool for drug development, and to have applications within transplantation medicine.
Indeed, there are many reasons to get excited looking forward in the field of stem cell research, but, as is always true with new scientific technologies, we cannot let ourselves get distracted by the possibilities without first evaluating the ethical implications.
The issue comes down to one method used to procure a certain type of stem cell. Embryos created through in vitro fertilization (IVF) that the couple using IVF ultimately do not need can later be donated to research with the consent of the parents. Human embryonic stem cells (hESCs) can then be taken from the inner cell mass of blastocysts (embryos which are three to five days old) and be used for research. However, in this process, the embryo is destroyed, ending the life of a human being.
While the numerous possibilities of embryonic stem cell research (ESCR) are enticing, we must remember that every human life is just as valuable as the next. Thus, killing a human being for the purpose of procuring stem cells cannot be justified.
Some may argue that leftover embryos created for the purposes of IVF are simply going to be discarded anyway, and therefore it is worthwhile to at least gain scientific knowledge from their short lives. But I reject this argument for two reasons. First, it is important that we respect each human being as an end, rather than treating them as a means. Certainly, the application of this justification for ESCR to other living humans that will likely die soon fails miserably. Consider terminally ill patients and prisoners on death row. The fact that they may pass away soon or are scheduled to be executed does not justify experimentation on them that would intentionally end their lives. Second, it is simply not true that the only fate that awaits these embryos is that they will be discarded. Organizations such as Nightlight Christian Adoptions offer parents the opportunity to adopt and implant the remaining embryos not used in IVF, giving them an opportunity to grow and develop into adulthood.
But even for those who aren’t convinced that ESCR is unethical, there is another, more pragmatic reason we should not pursue this route. As anyone who works in a research field knows, funds are limited. This being the case, it’s important that we direct the funds we have toward the method of stem cell research which shows the most promise. At the moment, it is very clear that this method is not ESCR.
As of right now, no successful therapies have been created with hESCs, in part due to the multitude of challenges they present. For example, hESCs pose the possibility of immune rejection. Because the recipient of a hESC therapy is not genetically similar to the embryo donor, the donor cells may activate an immune response causing the body to destroy them. Injecting hESCs into humans also carries with it the risk of creating malignant cancers due to hESCs’ rapid growth. Finally, while pluripotency, or the ability to create any type of cell in the body, is a valuable trait because of its versatility and would be an advantage of using hESCs, it is really only a useful attribute if we know and understand how to control cell differentiation. For many tissues, however, controlling such differentiation remains only a current area of research. Pluripotency holds no value if we cannot regulate it.
These challenges have prevented ESCR from creating any fruitful results to this date, but in the meantime another type of stem cell research has been very successful. Adult stem cells differ from hESCs in that they are present in tissues such as muscle, bone marrow, and the brain and are responsible for regenerating those tissues after they are damaged due to injury, disease, or old age. However, they don’t have pluripotency as hESCs do. Adult stem cells are instead described as “multipotent,” or having the ability to create a limited number of different cell types.
To give one example, a hematopoietic cell is an adult stem cell for blood and has the ability to create any of the several different types of cells present in our blood (ranging from red blood cells to the various types of white blood cells). However, it does not have the ability to create a skin cell or a muscle cell as a pluripotent stem cell does. On the other hand, because adult stem cells do not proliferate as well as hESCs, they are less likely to create tumors. Moreover, because they can be retrieved from the same person who is receiving the therapy, immune rejection is not a problem.
In contrast to ESCR, investigators have had enormous success in using adult stem cells for research in the lab and as treatments. Leukemia, lymphoma, sickle cell anemia, and certain metabolic conditions can be treated with adult stem cells, and there have been major strides in the treatments of other diseases (such as heart disease) in clinical trials using adult stem cells.
These advances in the field of adult stem cell research, however, still have not silenced some proponents of ESCR, who argue that we should be exploring every option we have and are worried that there are limits to what we can do with multipotent stem cells. Such concerns have led investigators to search for a pluripotent option that is less ethically unsound than hESCs. In 2006, researchers at Kyoto University in Japan found success. They were able to create “induced pluripotent stem cells” (iPSCs) by reprogramming adult cells to act like hESCs. They reported that these cells “were similar to hES cells in morphology, proliferation, surface antigens, gene expression, epigenetic status of pluripotent cell-specific genes, and telomerase activity.” In short, they were able to induce hESC-like behavior in cells derived from adults, instead of embryos. This iPSC method does not require the destruction of human life, creates cells that have the powerful pluripotent qualities of hES cells, and do not have the risk of immune rejection.
Scientists are looking forward to the multitude of purposes these iPSCs could serve. Already they are being used to understand and model diseases, develop and screen candidate drugs, and deliver cell-replacement therapy to support regenerative medicine.
The creation of iPS cells is an exciting advancement in the world of stem cell research, and with this pluripotent option in addition to the extant therapies of adult stem cells, there are really no practical reasons that we should ever want or need to explore the possibilities of ESCR. However, while these alternatives are exciting, it is important for us to remember that even if they didn’t exist, medical advances at the cost of human lives are unjustifiable. If ESCR ever happens to produce desirable results in the future, it would still be wrong to pursue this method of obtaining stem cells, for the very important reason that all human lives are valuable, even those in their earliest stages of development.
“The Power of Stem Cells,” California Institute for Regenerative Medicine, accessed September 15, 2016, https://www.cirm.ca.gov/patients/power-stem-cells#5.
Junying Yu and James Thomson, “Embryonic Stem Cells,” National Institutes of Health, accessed September 15, 2016, http://stemcells.nih.gov/info/Regenerative_Medicine/2006Chapter1.htm.
“Stem Cell Basics,” National Institutes of Health, accessed September 15, 2016, http://stemcells.nih.gov/info/basics/4.htm.
“Stem Cell Research: Stem Cell Therapy,” Johns Hopkins Medicine, accessed September 15, 2016, http://www.hopkinsmedicine.org/stem_cell_research/cell_therapy/; “Stem Cell FAQ,” International Society for Stem Cell Research, accessed September 15, 2016, http://www.isscr.org/visitor-types/public/stem-cell-faq.
Kazutoshi Takahashi, Koji Tanabe, Mari Ohnuki, Megumi Narita, Tomoko Ichisaka, Kiichiro Tomoda, and Shinya Yamanaka, "Induction of Pluripotent Stem Cells from Adult Human Fibroblasts by Defined Factors," Cell 131, no. 5 (2007): 861-872.