This blog post examines how stem cell technology is used in regenerative medicine and the ethical and scientific issues that arise from its use.
Among the topics related to regenerative medicine recently covered by the National Geographic Channel, stem cell technology has attracted the most attention. Stem cells can be used to “cultivate” patient-specific organs in a laboratory for transplantation. Since the organs produced in this way are genetically identical to the patient, there is almost no immune rejection, and in theory, they have unlimited regenerative potential. For this reason, stem cells are attracting intense interest in various life science fields, including biochemistry and medicine. Stem cells are defined as “undifferentiated cells that can develop into any type of tissue” and are also called totipotent cells. Undifferentiated cells are cells that have not yet been assigned a specific function, and a typical example is the embryo at the blastocyst stage, which is formed through repeated cell division in the uterus. The process by which these cells are assigned specific functions is called “differentiation,” and the form that the cells differentiate into is determined by where the various transcription factors in the egg enter during cell division. For example, if a transcription factor that activates the genes necessary for differentiation into skin cells is present in undifferentiated cells, those cells will differentiate into skin cells. Stem cell technology aims to artificially differentiate cells into the desired cells or tissues by utilizing this property.
Stem cells can be broadly divided into embryonic stem cells, adult stem cells, and induced pluripotent stem cells (iPS cells). Embryonic stem cells are classified into fertilized embryo stem cells and nuclear replacement embryo stem cells depending on the method of cell extraction. Fertilized embryo stem cells are obtained by separating the inner cell mass from the blastocyst of a fertilized egg and have the potential to differentiate into almost all cells in the body. In 1998, James Thomson and John Gurkha’s research team in the United States isolated human embryonic stem cells for the first time in the world, and full-scale research began. However, ethical controversies arose because embryos must be destroyed to obtain cells from fertilized eggs, which is considered “destruction of life.” In addition, using cells from genetically different individuals may cause immune rejection, and there is a risk of cancer cells developing during the differentiation process. Nuclear replacement embryonic stem cells are obtained by extracting the nucleus of a patient’s somatic cell, inserting it into an egg from which the nucleus has been removed, and developing it to the blastocyst stage. This method uses a principle similar to that used to create Dolly the cloned sheep. Although ethical controversies are reduced because fertilized eggs are not used, the debate over the use of eggs remains. Since the patient’s own cells are used, the possibility of immune rejection is low, but the technology is difficult and there is a risk of cancer.
Adult stem cells are undifferentiated cells that exist in small quantities in tissues that have already undergone some differentiation, such as adult skin, bone marrow, and umbilical cord. They have multipotency, meaning that, for example, stem cells obtained from skin can only differentiate into skin tissue, and stem cells obtained from bone marrow can only differentiate into blood cells. Research began in 1961 when Tille and McClure discovered hematopoietic stem cells in bone marrow. Adult stem cells do not raise ethical issues because they do not use embryos, and there is no immune rejection when using autologous cells. However, they exist in very small quantities, making it difficult to obtain large quantities, and their differentiation potential is limited.
Induced pluripotent stem cells (iPS cells) are cells that have been returned to an undifferentiated state by introducing specific genes into cells that have already differentiated. In 2007, a research team led by Shinya Yamanaka in Japan succeeded in creating iPS cells by introducing four reprogramming factors into mouse skin cells, and was awarded the Nobel Prize in Physiology or Medicine for this achievement. Initially, gene carriers such as retroviruses were used, but due to side effects such as the insertion of viral genes into cells, non-viral methods using plasmids or proteins are now mainly used. iPS cells have the same potential as embryonic stem cells, but are free from ethical issues and immune rejection reactions, unlike adult stem cells. However, their reprogramming efficiency is low, and because they are artificially produced cells, there is a possibility of genetic instability. As of 2025, research is actively underway to improve efficiency and safety through chromatin structure regulation, chemical treatment, and fusion with gene editing technology (CRISPR). In fact, there have been reports of cases where the efficiency of neural stem cells was improved by 100 to 3000 times through reprogramming.
The most important issues in stem cell research are bioethics and immune rejection. The use of fertilized eggs to obtain embryonic stem cells is considered by many to be the destruction of new life. Immune rejection is also a major problem, as the immune system may attack tissues that are not the patient’s own, causing the transplant to fail. For this reason, patient-specific organ production and the use of autologous stem cells are attracting attention.
In terms of applicability, stem cells have great potential for treating diseases that are difficult to cure, such as Parkinson’s disease, spinal cord injury, type 1 diabetes, and spina bifida. In fact, positive results have been reported in some animal experiments and early clinical trials, and there are cases where bladder function has been restored by transplanting a bladder cultured from adult stem cells of patients with bladder dysfunction, and research is underway to apply insulin-producing cells made from iPS cells to the treatment of diabetes patients. In addition, it has great potential for use in various fields such as infertility treatment, disease modeling, and new drug development. Research is also actively underway to analyze the onset of diseases by dedifferentiating diseased cells and establish strategies for their prevention and treatment.
The economic impact is also significant. Once stem cell technology is commercialized, new markets will be created in the fields of personalized medicine, organ replacement, and rehabilitation medicine, and innovation will occur throughout the pharmaceutical and biotechnology industries. This is likely to lead to reduced medical costs, job creation, and enhanced global healthcare competitiveness.
In conclusion, stem cells are classified into embryonic stem cells, adult stem cells, and dedifferentiated stem cells, each with its own advantages and disadvantages. Although two key issues remain—bioethics and immune rejection—the speed of technological advancement makes it increasingly likely that these issues will be resolved. Stem cell research has the potential to have a major impact on various fields, such as medicine, pharmacy, cell biology, and biotechnology, as well as the economy as a whole, and will establish itself as a core technology of the future that will revolutionize human health and longevity.
