What are Stem Cells?
In the broadest sense, stem cells are undifferentiated cells in the body. This means that they have no specific responsibility, structure or function. (Kohn, 2013). According to (MNT Editorial Team, 2017), “Stem cells are able to differentiate into specialized cell types”.
Stem cells come from 2 sources. These are embryos that are formed during the stage of pregnancy knows as the blastocyst phase which takes place between 5 and 9 days upon conception. These stem cells are known as embryonic stem cells.
The second type is the Adult tissue (adult stem cells).

What are the Characteristics of Stem Cells?
Stem cells have 2 very prevalent characteristics which distinguish them from all other cells in the human body.
These 2 characteristics are that
They Are Not Specialized
Stem cells do not have any tissue specific structures that allow them to perform or carry out functions that would make them specialized. An example is that stem cells cannot work together to pump blood around the body like the cardiac muscle cell would. Neither can it transport impulses across synapses like the nerve cell would. But, stem cells do give rise to specialized cells, including cardiac muscle cells as well as nerve cells; among others.
They Give Rise to Specialized Cells
The process in which stem cells give rise to specialized cells is known as differentiation. During this process, the stem cell undergoes several different stages as it becomes increasingly differentiated. Different signals inside and outside the cells trigger each step of the differentiation process. The internal signals being controlled by their genes which are scattered across different strands of DNA and carry specific instructions that trigger every single step of the differentiation process. However, the external signals include chemicals that are secreted by other cells. The combining of such signals causes the DNA of the cell undergoing the process to acquire marks that are called epigenetic marks (which show the genes are to be expressed).
Scientists continue to attempt to understand these different signals that influence differentiation and how they trigger each individual step of the process. (U.S Department of Human and Health Services, n.d.)

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What is the Difference Between Embryonic Stem Cells and Adult Stem Cells?
Adult stem cells are less versatile than embryonic stem cells. This is in the sense that embryonic stem cells have greater potential to differentiate than adult stem cells because they can end up developing into any cell that is needed in the human body. This basically means that embryonic stem cells are pluripotent while adult stem cells are not.
Adult stem cells usually develop into a limited number of cell types which illustrates their relative inability in terms of versatility in comparison to embryonic stem cells. However, recent studies show that adult stem cells have more plasticity (adaptability to changes in its environment) which translates to adult stem cells being able to differentiate more than initially thought.
But, that does not translate to the fact shown through study that it’s evident that embryonic stem cells are much more equipped to differentiate better and more diversely than adult stem cells. (Murnaghan, 2018)
Another difference is their sources. As seen in the name, embryonic stem cells come from the embryo. However, these stem cells are produced when the embryo is between 3 and 5 days old. This point in the embryos life is called the blastocyst phase. (Mayo Clinic, 2013)
The adult stem cells however have more sources than the embryonic stem cells. They have 4 main sources of production. These are human umbilical tissue, the bone marrow, cord blood (According to a publication by (New York Blood Center, 2015) this is the blood that remains in the placenta and is attached to the umbilical upon birth of a child) and fat tissue. (Riordan, 2017)

What Makes Stem Cells Suitable for Therapeutic Use?
Embryonic stem cells can possibly be used to make more specialized tissues that have become worn out or lost completely due to disease and/or injury. This is due to the ability of stem cells to differentiate into any cell upon necessity for that process to occur. For tissues that require constant replacement (like the small intestine lining which is replaced about every 4 days), stem cells would most likely be replaced directly. Presently, researchers are looking for and formulating ways in which stem cells could possibly be used to treat diseases such as diabetes, Parkinson’s disease, spinal cord injury, heart disease, vision and hearing loss and many more.
Embryonic stem cells are suitable for therapeutic use as they can be used for the screening of future drugs. Certain cancer cells are already used for the screening and testing of cancer drugs. This means that growing embryonic stem cells into heart, liver and/or nerve cells among others can prove to be very useful in the long run in relation to testing drugs that can be used to treat diseases that affect organs that those cells are specialized to work into. (Springer Nature, 2018)

How are They Obtained?
Due to the main types of stem cells being structurally different and different in terms of origin, the obtaining of embryonic stem cells is different from obtaining adult stem cells.
According to a publication by (The Center for Bioethics & Human Dignity, 2009), “Typically, they are derived from human embryos—often those from fertility clinics who are left over from assisted reproduction attempts (e.g., in vitro fertilization). When stem cells are obtained from living human embryos, the harvesting of such cells necessitates destruction of the embryos.”
In contrast, adult stem cells are obtained in completely different manners and due to their different sources, they have different modes of being retrieved.
First and foremost, according to a publication by (Boston Children’s Hospital, 2018), adult stem cells are retrieved from the body itself. This is in the sense that adult stem can be isolated in a multitude of manners, but this solely depends on the tissue. For example, “blood stem cells can be taken from a donor’s bone marrow, from blood in the umbilical cord when a baby is born, or from a person’s circulating blood.”
Another source is amniotic fluid which covers the fetus over the course of the gestation period, containing cells which include mesenchymal stem cells which can make various tissues like muscle and skeletal cells. Usually pregnant women decide to have amniotic fluid to check for chromosome defects in the child (this is called amniocentesis). And that’s another way in which adult stem cells can be obtained. (Boston Children’s Hospital, 2018)

Use of Stem Cells in the Treatment of Stargard’s Disease
Stem cells are used in the treatment of disorders like Stargard’s Disease as well or at the very least in theory can assist in treating those who have this disease. Stargard’s disease is a genetic disorder that mainly affects the retina and can cause blindness during childhood or adolescence. Investigations have suggested that the capacity for stem cells to differentiate into a vast array of cells can assist the fight against this disease due to their capability to possibly differentiate into rods and cones (the cells that are prevalent in the human eye). (Advancells, 2017)
ONE OTHER CONDITION where stem cells are used for therapy
Another condition that can be assisted in terms of medicinal progression by stem cells is Alzheimer’s Disease (abbreviated as AD). Research done by Jessica Young showed that therapeutic measures such as gene therapy, may be a good measure in the battle against Alzheimer’s disease.
In the study, Young and her team retrieved skin cells from patients who have AD and people with no signs of dementia. This being because people have the same genome which means that the AD patients would have the same genetic mutation in their skin cells as their brain cells. The researchers then reprogrammed the skin cells to act as stem cells which shows that they are induced pluripotent stem cells, which will develop into any cell type. Therefore, their research in theory shows that it is possible to create neurons that can possibly regenerate the part of the brain which is affected by AD. (“Stem-cell study points to new approach to Alzheimer’s disease: An experimental compound reduced production of toxic proteins implicated in brain-cell death in Alzheimer’s disease,” 2018)

Ethical Implications on the use of stem cells
According to (Websteen.nl Webdesign – Huizen, 2014), there are 2 main ethical and moral implications related to the use of stem cells (otherwise known as stem cell therapy). These are “Respect for Human Life” and “Status of the Human Embryo”.
Regarding respecting life, the reason stem cell therapy is viewed as an ethical issue is that an embryo (a potential human life) is destroyed during the process of retrieving stem cells. However, the counterargument is that the benefits that are to be unearthed such as the curing of different diseases illustrates another mode of showing respect to human life. Other concerns rest on that belief that creating embryos just for research and deriving stem cells might lead to human life becoming de-sensitized and to potentially become commercializing or instrumentalizing the human body to an extent and subsequently to the human life.
According to the same study, the status of the embryo is another ethical implication. This is somewhat regarded as a delicate question because of different peoples view on how an embryo is to be regarded. Some people view embryos merely as cell masses which hold no more value than any other cell or tissue. However, some see the human embryo as a full human life in the sense that they see the human embryo as having similar status as a human being that has been born. Additionally, there is a view that’s gradualist. They see the status of the embryo as progressive as it continues to mature. This emphasizes the capability of the embryo to become a fully-fledged human life, which means that the embryo receives a form of “human life”.
In conclusion, the strides being made in science and medicine to further health care is commendable as a proper source of cells that don’t have to be synthesized has been found. The steps forward that will be made will be great in the furtherance of worldwide medicine as we know it. However, its acceptance on a global scale will remain to be seen.

Advancells. (2017, September 21). Stem Cells Therapy for Macular Dystrophy (Stargardt’s Dystrophy). Retrieved from https://www.advancells.com/blog/stem-cells-therapy-for-macular-dystrophy/
Boston Children’s Hospital. (2018). Where Do We Get Adult Stem Cells? | Boston Children’s Hospital. Retrieved from http://stemcell.childrenshospital.org/about-stem-cells/adult-somatic-stem-cells-101/where-do-we-get-adult-stem-cells/
The Center for Bioethics ; Human Dignity. (2009, August). An Overview of Stem Cell Research | The Center for Bioethics ; Human Dignity. Retrieved from https://cbhd.org/stem-cell-research/overview
Kohn, C. A. (2013, September 10). What are stem cells? Video file. Retrieved from https://www.youtube.com/watch?v=evH0I7Coc54
Mayo Clinic. (2013, March 23). Stem cells: FAQs about stem cell research. Retrieved from https://www.mayoclinic.org/tests-procedures/bone-marrow-transplant/in-depth/stem-cells/art-20048117
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Murnaghan, I. (2018, May 1). Adult vs. Embryonic Stem Cells. Retrieved from http://www.explorestemcells.co.uk/adultvsembryonicstemcells.html
New York Blood Center. (2015). Cord blood q;a. Retrieved from http://www.nationalcordbloodprogram.org/qa/www.nationalcordbloodprogram.org/qa/
Riordan, N. H. (2017). Sources of Adult Stem Cells. Retrieved from https://www.cellmedicine.com/sources-of-adult-stem-cells/
Springer Nature. (2018). How can stem cells advance medicine? Retrieved from https://www.nature.com/stemcells/2007/0706/070614/full/stemcells.2007.23.html
Stem-cell study points to new approach to Alzheimer’s disease: An experimental compound reduced production of toxic proteins implicated in brain-cell death in Alzheimer’s disease. (2018, March 1). Retrieved from https://www.sciencedaily.com/releases/2018/03/180301144157.htm
U.S Department of Human and Health Services. (n.d.). Stem cells basics ii. Retrieved from https://stemcells.nih.gov/info/basics/2.html
Websteen.nl Webdesign – Huizen. (2014). Stem Cell Therapy Ethics – Biomedinvo4all. Retrieved from http://www.biomedinvo4all.com/en/research-themes/stem-cell-therapy/stem-cell-therapy-ethics