By Erica Lynn
Over the years, stem cell research has been a topic of interest in the scientific community, as it has the potential to provide new treatment for a myriad of diseases. However, stem cells must first be explained.
Humans start out as a single cell: the fertilized egg. Through the process of differentiation, this one cell divides into many cells that each have a specific function [3]. An example of differentiated cells are red blood cells that have the specific function of carrying oxygen through the blood. Stem cells, however, are cells that have not gone through the differentiation process and therefore, still have the ability to differentiate into many types of specialized cells in the body [4]. This ability makes them useful in replacing cells that have been damaged or destroyed.
There are two main types of stem cells: embryonic stem cells and adult stem cells. Embryonic stem cells are derived from unused embryos that are a result of in-vitro fertilization procedures [5]. These are procedures in which mature eggs are retrieved from ovaries and fertilized by sperm in a lab to produce fertilized eggs that can develop into embryos and eventually into organisms. Embryonic stem cells are pluripotent; they can differentiate into any type of cell of an organism [5]. Adult stem cells, on the other hand, are multipotent, meaning they can only differentiate into a few closely related types of cells. Adult stem cells often come from fully developed tissues such as the brain, skin, and bone marrow [5]. An example of adult stem cells are neural stem cells, which can only become cells within the brain and spinal cord [10].
One of the diseases that stem cells are used as part of the treatment for is leukemia. Leukemia is the cancer of the blood or bone marrow, and it results in an abnormally high level of poorly functioning white blood cells [9]. These white blood cells multiply uncontrollably and prevent healthy white blood cells from growing and functioning normally. As a result, the immature white blood cells are not only unable to fight infection but also unable to reduce the body’s ability to produce red blood cells and platelets that are needed to keep one’s body healthy [1]. A method to treat leukemia is to use hematopoietic stem cells (HSC). These are adult stem cells that originate from bone marrow and produce blood cells [5]. When a leukemia patient has had chemotherapy and/or radiotherapy that destroys their diseased white blood cells, the destroyed cells need to be replaced with healthy white blood cells [11]. This is where hematopoietic stem cells are utilized. HSCs can be delivered into the patient’s body in one of two ways: through stem cell infusion or direct injection. Stem cell infusion allows the patient to receive the stem cells through an IV drip, which directly releases the cells into the bloodstream [7]. Direct infusion involves putting stem cells into a needle and injecting it at the site of damage, which is the bone marrow in this case [7]. After the HSCs have entered the bloodstream, they travel to the patient’s bone marrow and begin to differentiate, forming new healthy white blood cells that are able to replace the destroyed ones [8].
The stem cells can be harvested from the patients themselves or from a matching donor. A stem cell transplant harvested from the patient is referred to as an autologous stem cell transplant. In this procedure, the stem cells are taken from the patient’s own blood before chemo/radiotherapy and frozen until they are needed [8]. The process of an autologous stem cell transplant involves taking medications to increase the patient’s number of stem cells so that they would move from the bone marrow to the blood. A needle would then be inserted into the vein to draw out the blood with the stem cells. Finally, the stem cells are filtered out of the blood with a machine, the remaining blood is returned to the body, and the stem cells are frozen for use after chemo/radiotherapy [3]. The benefits of this type of transplant is that the patient would not need to worry about their body reacting negatively to the stem cells since the cells are from themselves. If the stem cells are from a donor, this is called an allogeneic stem cell transplant. To find a matching donor, the patient undergoes a human leukocyte antigen (HLA) test, where the patient’s blood and tissues are compared to that of the donor's [8]. A drawback of an allogeneic stem cell transplant is that the body may reject the stem cells since they are not from the patient’s body. This can occur if the body’s immune system detects that the antigens on the stem cells as foreign and attacks the cells.
Despite how promising and exciting stem cell research is, there are ethical issues involved, especially in the uses of embryonic stem cells. Embryonic stem cells are obtained from unused embryos, which are the result of carrying out in-vitro fertilization. Embryonic stem cells can differentiate into any type of cell in the body. In comparison, adult stem cells can only differentiate into closely related cells; therefore, embryonic stem cells are useful in replacing any cell in the body. Since harvesting embryonic cells leads to the embryo’s death, critics of embryonic stem cell research argue that this is equivalent to taking a human life [3]. However, induced pluripotent stem cells (iPSC) have reduced the need for embryonic stem cells, relieving some of the ethical concerns. iPSCs are cells that have already differentiated but are reprogrammed by scientists to return to undifferentiated states. This allows them to be able to divide and become any cell in the body, making them become pluripotent stem cells that have the same abilities as embryonic stem cells [12]. Thus, stem cells harvested from embryos are no longer needed to get pluripotent stem cells.
Research on stem cells can increase our understanding of diseases, be used to test new drugs, and offer new medical treatments for a variety of problems and diseases including Alzheimer’s, Parkinson’s, Stagradt’s disease, heart disease, stroke, burn, spinal cord injury, and even cancer [6]. This area of research is one of the most promising ones and can result in a significant reduction of human illness and fatality.
References:
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