In this blog post, we’ll explore the characteristics and types of stem cells—which can differentiate into various cell types—as well as the potential and limitations of stem cell-based therapies.
What diseases remain difficult to cure or have treatment limitations even with modern medical technology? There are likely many, such as cancer and HIV. Would you believe it if someone claimed that all these intractable diseases could be treated using a single technology? The technology attracting attention for this very reason is stem cell technology. However, stem cells have not yet been established as a universal cure for all diseases; while stem cell therapies are already being used for some conditions, many treatments are still in the research and clinical trial phases.
Stem cells play a crucial role in producing the various cells that make up our bodies. The human body is composed of hundreds of different types of cells that perform the tasks necessary for our daily lives. These cells perform various functions, such as enabling us to move our bodies to write, allowing us to breathe, and repairing damaged tissue when we accidentally fall and injure our legs. In this context, the role of stem cells is to produce the various cells responsible for these functions. In other words, they act as a “supplier” that generates new cells. When stem cells divide, they can either regenerate themselves or differentiate into other types of cells. For example, stem cells found in muscle tissue can produce more stem cells, or they can differentiate into muscle cells that express proteins such as myosin and actin. Stem cells possess the unique ability to maintain themselves while differentiating into the necessary cell types.
Given this ability to generate new cells, research has been conducted on using stem cells as the raw material for cell therapies to treat various intractable diseases. In other words, the idea is that by administering stem cells or cells differentiated from stem cells to patients, the regenerative and differentiation capabilities of stem cells can be harnessed to restore damaged tissues or functions and help patients regain their health. For example, in the case of a patient with severe skin damage, one approach would be to transplant appropriately differentiated cells into the affected area to aid in the recovery of damaged skin tissue. However, administering stem cells to treat diseases such as cancer does not mean that the stem cells themselves cure the cancer, nor is stem cell therapy applied in the same way for every disease. Since the stem cells naturally present in our bodies are not always capable of providing the full therapeutic potential needed to treat diseases or tissue damage, research is underway to secure sufficient numbers of the necessary cells, properly differentiate them, and utilize them for treatment. The goal is to supplement the body’s natural regenerative capacity and restore damaged tissue. Based on this principle, researchers are exploring the potential of stem cell therapy for a wide range of diseases.
Stem cells can be broadly categorized into adult stem cells, embryonic stem cells, and induced pluripotent stem cells. Various tissues and organs in our bodies contain tissue-specific stem cells capable of differentiating into cells specific to each tissue. These stem cells are called adult stem cells. Adult stem cells are found in specific tissues or organs, where they play a role in maintaining those tissues and replacing damaged cells. For example, hematopoietic stem cells, which produce blood, generate blood cells, and adult stem cells in each tissue can differentiate into various cell types associated with their respective tissues. There are also stem cells known as “embryonic stem cells.” These stem cells originate from early embryos and can differentiate into cells that form various tissues and organs during human development. In other words, they have the potential to transform into many different types of human cells. As the name suggests, “embryonic stem cells” are stem cells derived from the very early stages of human development. To put it simply, the difference between these two types of stem cells is that adult stem cells found in the skin are primarily specialized in maintaining skin tissue and producing related cells, whereas embryonic stem cells can differentiate into various cells that make up the human body, such as skin, blood, brain, and liver cells. Finally, “induced pluripotent stem cells” have attracted the attention of many scientists because they can be created by reprogramming already-differentiated adult cells in the laboratory to possess pluripotency similar to that of embryonic stem cells. Induced pluripotent stem cells are significant because they can be obtained by reprogramming adult cells without directly using embryos. Researchers use specific transcription factors and other tools to reset the gene expression profile of adult cells, thereby generating iPSCs. While both embryonic stem cells and iPSCs possess pluripotency—the ability to differentiate into a wide variety of cell types—adult stem cells generally differentiate only into a limited set of cell types associated with their native tissue.
Of course, several challenges remain before treatments using stem cells with such high differentiation potential can become widespread. The use of embryonic stem cells raises ethical concerns related to the use of embryos, while for pluripotent stem cells—including iPSCs and embryonic stem cells—issues such as the technology to precisely differentiate them into the desired cell types, safety, and the potential for tumor formation must be addressed. Above all, the efficacy and safety of stem cell therapies must be sufficiently proven for each specific disease and treatment method. In fact, the stem cell products currently approved by regulatory agencies and in use in the United States are primarily umbilical cord blood-derived hematopoietic stem cell products used for hematological disorders; stem cell therapies for various other conditions, such as stroke, cardiovascular disease, and neurological disorders, have not yet been fully established. Therefore, it is difficult to conclusively assert that stem cells can necessarily treat all diseases that are difficult to treat with modern medicine. Nevertheless, stem cell research demonstrates the potential to replace or regenerate damaged cells and tissues, advance our understanding of diseases, and develop new treatments. In the future, if these scientific, technological, and ethical challenges are resolved and safety and efficacy are sufficiently verified, stem cell therapy could offer new possibilities for treating various diseases where current treatments have limitations, such as stroke, heart disease, Basarab-Deussy disease, cancer, Huntington’s disease, and spinal cord injury. While stem cells are not a panacea capable of curing all diseases at once, they are undoubtedly an important technology that opens up new medical possibilities for restoring the damaged human body and treating diseases.
