Written by Gisela Ismaili
Edited by Tasniah Jahan
Stem cell therapy has been a highly discussed topic in the medical world for the last 30 years since scientists discovered ways to derive embryonic stem cells from the early stages of the mouse embryo. The potential use of stem cells in treating various diseases has brought hope to countless patients who are suffering from serious illnesses. This kind of therapy can provide new treatments for genetic disorders, autoimmune diseases, and many degenerative diseases. Stem cells are human cells that can differentiate into specialized cells such as nerve cells, blood cells, muscle cells, etc. There are several sources of stem cells: embryonic stem cells, adult stem cells, and perinatal stem cells. Each type of cell is obtained at different stages of life. For instance, embryonic stem cells are cells derived from an early-stage embryo called the blastocyst and are between 3 to 5 days old prior to implantation. At this stage, the blastocyst consists of about 150 cells. Embryonic stem cells are considered pluripotent and have an extensive ability to differentiate and specialize into any somatic cell type. Their immense versatility to regenerate and repair any diseased cell can be transformative for the field of medicine.
Although stem cell therapy seems like a light of hope amongst numerous life-threatening diseases, there is ethical and political controversy associated with stem cells. The center of the debate revolves around the fact that embryonic stem cells are extracted from human embryos, leading to questions about the ethical aspect of this research. Since human embryonic stem cell (hESC) research involves the destruction of human embryos, in the United States, the question of when human life begins has been highly controversial and closely linked to debates over abortion (Lo & Parham).
Contrasting standpoints surround the ethical dilemmas of embryonic stem cell research. In the article, "Ethical Issues in Stem Cell Research," the author states that ''Some people believe that an embryo is a person with the same moral status as an adult or a live-born child. They believe that ‘human life begins at conception’ and that an embryo is therefore a person. According to this view, an embryo has interests and rights that must be respected. From this perspective, taking a blastocyst and removing the inner cell mass to derive an embryonic stem cell line is tantamount to murder''. Others believe that an embryo at the stage of a blastocyst is just a clump of cells and can be used freely for research purposes. The authors also state that ''Opposition to hESC research is often associated with opposition to abortion and with the ‘pro-life’ movement. However, such opposition to stem cell research is not monolithic. A number of pro-life leaders support stem cell research using frozen embryos that remain after a woman or couple has completed infertility treatment and that they have decided not to give to another couple''.
All the controversies associated with embryonic stem cell research are completely reflected in the legislation of different countries around the world. According to “Ethical and Safety Issues of Stem Cell-Based Therapy,” in many countries including the United Kingdom, the use of hESCs for research is allowed, while other countries retain more extreme stances, as is the case of Italy where there is a prohibition on all hESC-based research.
Apart from the ethical implications, there are also safety issues regarding embryonic stem cell therapy use in clinical settings. “The pluripotency of hESCs is a double-edged sword; the same plasticity that permits hESCs to generate hundreds of different cell types also makes them difficult to control after in vivo transplantation. When undifferentiated hESCs are transplanted, teratomas, tumors that contain all three germ layers, could develop. Studies have revealed that appearance of teratoma is between 33-100% in hESC-transplanted immunodeficient mice, depending on the implantation site, cell maturation, purity, and implantation techniques” (Volarevic, et al). The only way to avoid the development of tumors and teratoma after hESC transplantation is to differentiate them into desired and mature cell types before injection and screen them for the presence of undifferentiated cells (Volarevic, et al).
In such instances, questions such as ''Why aren't adult stem cells used instead of embryonic stem cells?'' arise. Adult stem cells are found in adult tissues such as bone marrow and fat and have a limited capacity to give rise to various cells of the body. There are several reasons why this type of stem cell therapy cannot replace embryonic stem cells. For instance, adult stem cells may not be as versatile and durable as embryonic stem cells, thus making them unable to be manipulated to produce all cell types, which limits their potential to treat diseases. Furthermore, they are more likely to contain abnormalities due to exposure to environmental hazards, such as toxins, or from errors acquired by the cells during replication.
Thus far, the only FDA-approved stem cell therapy is blood stem cell transplantation, which is used to treat patients suffering from blood-related cancers. Scientists are persistently testing other forms of cell therapy that could be used in the future to treat degenerative diseases such as heart failure. Additionally, in recent years, stem cell research has considerably progressed and offers promise for life-changing treatments in clinical therapies for type 1 diabetes, multiple sclerosis, Parkinson's disease, etc.
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References:
Lo, B., & Parham, L. (2009). Ethical issues in stem cell research. Endocrine reviews, 30(3), 204–213. https://doi.org/10.1210/er.2008-0031
Volarevic, V., Markovic, B. S., Gazdic, M., Volarevic, A., Jovicic, N., Arsenijevic, N., Armstrong, L., Djonov, V., Lako, M., & Stojkovic, M. (2018). Ethical and Safety Issues of Stem Cell-Based Therapy. International journal of medical sciences, 15(1), 36–45. https://doi.org/10.7150/ijms.21666
Mayo Foundation for Medical Education and Research. (2022, March 19). Answers to your questions about Stem Cell Research. Mayo Clinic. Retrieved March 5, 2023, from https://www.mayoclinic.org/tests-procedures/bone-marrow-transplant/in-depth/stem-cells/art-20048117