1Running Head: STEM CELLS AND THEIR USES IN MEDICINE

Stem Cells and Their Uses in Medicine

Fatimah Alslman

Saginaw Valley State University

2STEM CELLS AND THEIR USES IN MEDICINE

Stem Cells and Their Uses in Medicine

Stem cells are a type of undifferentiated cells that can

differentiate to specialized cells. They are found in

multicellular organisms. There are two main types of stem cells.

The first type is found in the inner cell mass of the blastocyst,

which is made up of the embryonic stem cells. The second type is

found in adults tissues and that is called the adult stem cells.

Stem cells are important for their special properties that can

serve the medical field.

Stem cells have special properties that make them different

from all other cell types in the body. The first property is

self-renewal, which is the ability of stem cells to divide to

give undifferentiated stem cells for a long time, and this

property is more active in the embryonic stem cells. The second

property is that stem cells are not specialized, which means that

they have no specific structure that can make them capable to do

3STEM CELLS AND THEIR USES IN MEDICINE

specialized functions. For example, stem cells cannot carry

oxygen throughout the body as red blood cells do, and they cannot

be relaxed or contracted as muscle cells. The third and the most

essential property of stem cells is potency which is the

potential of stem cells to differentiate into specialized cells.

When a stem cell is going to differentiate, it moves from one

stage to another, and as it moves, it gets closer to being a

specialized cell. Also, the potency of stem cells can give rise

to other specialized cells in case of diseases or other tissue

damage.

Furthermore, differentiation potential differs between stem

cells, and it classifies stem cells into five types depending on

their differentiation potential (see Figure1). First are

totipotent stem cells, which are found in the blastocyst phase of

the embryonic early development, and they can differentiate into

embryonic and placenta cell types. Second are pluripotent stem

cells, which are derived from totipotent stem cells, and they can

differentiate into all cell types; embryonic stem cells are

considered pluripotent. Third are multipotent stem cells, which

4STEM CELLS AND THEIR USES IN MEDICINE

can differentiate into other cell types, but are more limited

than pluripotent stem cells. Fourth are oligopotent stem cells,

which can differentiate into only a few cell types. Fifth are

unipotent stem cells, which can differentiate into only one cell

type. These unique properties of stem cells make them an

attractive subject for medical researchers (Crosta, 2008).

5STEM CELLS AND THEIR USES IN MEDICINE

Figure1. Types of stem cells depending on their differentiation

potential. Adapted from Sartina, E. Stem Cells.

Embryonic stem cells are found in the blastocyst phase of

the embryonic development. In the beginning, a sperm cell

fertilizes an egg cell to produce the zygote, which starts to

divide to form a human embryo. The embryonic stem cells are

6STEM CELLS AND THEIR USES IN MEDICINE

derived from a four to six-days-old human embryo before

implantation, which usually consists of 50 to 150 cells and is

called the blastocyst. The blastocyst consists of an outer cell

mass that forms the placenta and an inner cell mass that

differentiates into all cell types in the human body.

Furthermore, these embryonic stem cells give rise to the three

primary germinal layers: endoderm, mesoderm, and ectoderm.

Endoderm consists of the gut, liver, and lungs. Mesoderm consists

of the skeleton, heart, muscle, and blood. Ectoderm consists of

the skin and the nervous system.

Embryonic stem cells are usually derived from in vitro

fertilized embryos. Embryonic stem cells are isolated from the

inner cell mass of the blastocyst. Then, scientists place them in

a culture dish that contains the necessary nutrients for them to

grow and divide. Also, they will maintain the surrounding

conditions that can keep them unspecialized. These embryonic stem

cells divide and replicate in the culture dish to give a huge

number of replicated embryonic stem cells which can be stimulated

to give differentiated cells later on.

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On the other hand, adult stem cells are found in many

different tissues in the human body. They can be found in the

brain, bone marrow, blood, liver, and skin; consequently,

sometimes they are called somatic stem cells. Also, they can

differentiate into only a few number of cell types; therefore,

they are considered multipotent. Adult stem cells are rare, and

are found in few numbers in every tissue except the bone marrow,

which is the richest tissue of adult stem cells. These adult stem

cells remain unspecialized for a long time until they are

activated by a disease or other tissue injury. Although it is

more difficult to grow adult stem cells in a culture dish and

keep them unspecialized, it is possible to isolate them from the

human body, and there are many evidences that they can be used in

medical treatments.

Embryonic stem cells and adult stem cells have many

differences between them. They both have advantages and

disadvantages. The major difference between embryonic and adult

stem cells is the number of differentiated cell types they can

differentiate into. Embryonic stem cells are considered

8STEM CELLS AND THEIR USES IN MEDICINE

pluripotent; therefore, they can differentiate into all cell

types. Conversely, adult stem cells are considered multipotent;

so, they can only differentiate into a few number of cell types.

Also, another important difference between embryonic and adult

stem cells is the risk of having a transplant rejection after

transplanting them to a patient. Adult stem cells are believed to

have less risk of a transplant rejection. That is because they

are derived from a patient to be expended and differentiated into

a specific cell type in a culture, and then they are transplanted

to the same patient, which will decrease the risk of a transplant

rejection. Thus, adult stem cells are less likely to be rejected

by the immune system than the embryonic stem cells.

Stem cell treatments have been a remarkable change in the

medical field. Researchers and scientists believed that stem

cells have a powerful potential. One of the reasons that make

stem cells an interesting subject for scientists is their ability

to differentiate into the a specific cell type if they were

directed to differentiate in a controlled culture by a certain

way. However, one of the most important uses of stem cells is

9STEM CELLS AND THEIR USES IN MEDICINE

tissues regeneration, where scientists isolate stem cells and

place them in a controlled culture and stimulate them to give the

desired cell type to grow a specific tissue, which can be

transplanted to the patient later on. There are many possible

stem cell treatments that can help patients with chronic diseases

such as heart failure treatment, spinal cord injury treatment,

cerebral palsy treatment, cancer treatments, blood diseases

treatment, and others (see Figure2).

10STEM CELLS AND THEIR USES IN MEDICINE

Figure 2: The possible stem cells treatments. Adapted from European

Federation of Pharmaceutical Industries and Associations. Stem

Cells.

A bone marrow transplant is one of the most successful stem

cell treatments these days. The bone marrow transplant, or the

cord blood transplant as it is called sometimes, can help

patients who have blood diseases such as leukemia, sickle cell

anemia, and aplastic anemia. In the bone marrow transplant

procedure, stem cells are removed from the patient’s bone marrow

by a needle then they will be frozen until the patient is done

with chemotherapy or radiation therapy. After that, these stem

cells are put back in the patient’s bone marrow. That is called

the autologous bone marrow transplant where stem cells are taken

from the same patient. Conversely, allogeneic bone marrow

transplant is a procedure where stem cells are isolated form

another person who is called the donor. These healthy stem cells

are going to be transplanted to the patient as soon as he is done

with his chemotherapy or radiation therapy. Umbilical cord blood

transplant procedure is almost the same as the previous

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procedures. The only difference is that stem cells are extracted

from a newborn umbilical cord blood after birth. After that,

these stem cells are put in the patient’s bone marrow. Finally,

these transplanted stem cells work to give rise to normal blood

cells in the patient’s body. The bone marrow transplant has made

a dramatic change in treating many blood diseases.

Stem cells promise to make a huge impact in organs and

tissues regeneration. There have been many experiments where stem

cells are used to regenerate a whole organ or a specific tissue

to replace damage once in the patient’s body. Recently,

scientists developed a new technique that helps burn victims. It

works by using a device that sprays stem cells on the burn skin

to regenerate the new skin. This device is called the skin-cell

gun, and it has been used since 2008 in many patients. In this

procedure, stem cells are isolated from the patient, and they are

put in aqueous solution so they can be sprayed on the burned skin

by the gun. It takes only few days to see the new regenerated

skin, unlike the skin grafting where it takes two to three weeks.

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Stem cells have been a turning point in the medical history.

Their special properties have made them an interesting subject to

researchers and scientists. Also, they made a huge change in many

patients’ lives. Stem cells are the body’s prime cells; they can

create other cell types, tissues and organs. Stem cells hold many

promises for the medical future. One day, every person may have a

bank where he keeps his regenerated organs for future uses.

References

Crosta, P. (2008,September). Stem Cells Information Section.

Medical News Today. Retrieved from

http://www.medicalnewstoday.com/info/stem_cell/

Edward, L. (2011). Skin-cell spray gun drastically cuts healing time for burns.

Retrieved from http://phys.org/news/2011-02-skin-cell-gun-

drastically.html

European Federation of Pharmaceutical Industries and

Associations. Stem Cells. Retrieved from

http://www.efpia.eu/topics/innovation/stem-cells

13STEM CELLS AND THEIR USES IN MEDICINE

National Institute of Health. (2012). Bone Marrow Transplant.

Retrieved from

http://www.nlm.nih.gov/medlineplus/ency/article/003009.htm

Sartina, E. Stem Cells. Retrieved from

https://www.healthtap.com/user_questions/735484-what-is-the-

difference-between-embryonic-stem-cells-and-umbillical

United States Department of Health and Human Services. (2009).

Stem Cell basics. Retrieved from

http://stemcells.nih.gov/info/basics/Pages/Default.aspx