Stem cells are divided into adult stem cells, embryonic stem cells, and induced pluripotent stem cells, each of which has different advantages, disadvantages, and ethical issues. Once these are addressed, stem cells could be the key to curing incurable diseases.
Stem cells are a word that anyone interested in life sciences has probably heard at least once: they’re being touted as the key to solving many incurable diseases, and their importance is growing every day. But few people know much about stem cells, and even fewer can explain them, so in this article, we’ll cover what they are, how they’re differentiated, and what their limitations are.
Early-stage cells undergo several processes to develop into mature cells with different characteristics, one of which is differentiation. Once differentiated, cells have the right characteristics to function in their respective tissues. Through this process, early-stage cells develop into the cells that make up various tissues, such as bone, skin, blood vessels, and more. Among the many cells in your body, there are also undifferentiated cells that have not yet undergone the differentiation process, which are called stem cells. Because they have not yet differentiated, stem cells have the ability to differentiate into various body tissues when the right conditions are met.
Stem cells can be broadly categorized into adult stem cells, embryonic stem cells, and induced pluripotent stem cells (iPS cells). Adult stem cells are stem cells that are present in certain mammalian tissues and can differentiate into a limited number of tissues, although they cannot differentiate into all tissues. These stem cells are called multipotent stem cells. Examples of adult stem cells include hematopoietic stem cells in the bone marrow and mesenchymal stem cells in the liver. Hematopoietic stem cells are responsible for producing red blood cells and various white blood cells, and mesenchymal stem cells are responsible for making bones and the connective tissue that surrounds them, muscle. These multipotent stem cells differentiate as needed. In fact, blood cells that differentiate in the bone marrow do so in response to signals from neighboring cells or the circulatory system.
Embryonic stem cells are stem cells found in early embryos that have the ability to form an entirely new individual. In humans, a clump of cells called a blastocyst forms during the early stages of an embryo, and the cells in this blastocyst have the ability to differentiate into all the different types of cells that make up the body. Embryonic stem cells can be isolated from this blastocyst and, under the right conditions, can multiply almost indefinitely and, given the right signals, differentiate in specific ways. These stem cells are called pluripotent stem cells. However, the process of obtaining embryonic stem cells is fraught with ethical issues. Obtaining embryonic stem cells requires the destruction of the blastocyst, which is the stage at which it has the potential to develop into a living organism, which raises ethical questions. There is also the issue that embryonic stem cells and the tissue they are derived from can trigger an immune response in the recipient when transplanted. However, this can be overcome by replacing the nucleus of the fertilized egg with the nucleus of the recipient’s somatic cell.
Fortunately, a new method of creating pluripotent stem cells has been developed that solves both of these problems. Instead of isolating embryonic stem cells from a blastocyst, Professor Shinya Yamanaka and his team at Kyoto University in Japan used a patient’s own skin cells to create pluripotent stem cells. These stem cells are called induced pluripotent stem cells (iPS cells). After examining the differences in genes expressed by embryonic stem cells and non-stem cells, the team identified genes that are uniquely expressed at high levels in embryonic stem cells. Determining that these genes were essential for the undifferentiated state of the stem cells and for embryonic stem cell function, the team introduced them into a patient’s skin cells to create induced pluripotent stem cells, which, because they are derived from the patient’s skin cells, do not trigger an immune response and have already been used for cell therapy in animals with diseases, and will soon be used in humans.
As we’ve seen, there are three main types of stem cells: adult stem cells, embryonic stem cells, and induced pluripotent stem cells, each with their own advantages and disadvantages. Adult stem cells have the advantage of not triggering an immune response, but the disadvantage is that they have a limited range of differentiation. Embryonic stem cells, which have been studied to address this issue, have the advantage of a broader range of differentiation, but have the disadvantage of being able to trigger an immune response and ethical issues. Induced pluripotent stem cells have been researched to address the disadvantages of embryonic stem cells while retaining their advantages. However, both embryonic stem cells and induced pluripotent stem cells are unstable and have the potential to develop into cancer.
There are other issues that need to be addressed. One is that when stem cells are cultured, they often differentiate into cells with different functions. In order to inject stem cells into the blood and induce them to reach and differentiate into the desired targets, a fairly large amount of stem cells are required. However, with current technology, it’s difficult to get the desired amount of stem cells, because even if you get a small amount of stem cells, most of them will differentiate into cells with different functions during differentiation.
Despite these drawbacks, many people are interested in stem cells because they hold a lot of promise and offer hope for curing incurable diseases. If we can find a way to overcome the shortcomings of each type of stem cell, as well as their common shortcomings, stem cells could be the key to curing incurable diseases. The progress from the discovery of stem cells to the development of induced pluripotent stem cells makes stem cell research even more promising. With enough people interested in the field, stem cells may one day be the key to curing incurable diseases.
