Term 3 Blog Post 1: Stem Cells - What Possiblities Could Be Opened?

Recently, I did some research on the topic: Stem Cells. I wrote a report about it, and also used it as an ACE assignment, here's what I've come up with:

Wong Jin Fu Shaun

7 July 2010

1O4 (30)


Stem Cells – What possibilities could be opened?

What are stem cells?

Stem cells are found in all multi-cellular organisms. They are a class of undifferentiated cells that are able to differentiate into specialised cell types. Usually, stem cells come from two broad sources, which are those from the adult tissue and the embryonic stem cells. (Embryos formed during the blastocyst*(refer to embryonic stem cells) phase of embryological development). Also, both types are generally characterised by their potency to differentiate into different cell types. (Bone, skin, muscle, etc.)

Adult stem cells:

Adult stem cells exist throughout the body after embryonic development and are found inside of different types of tissue. These stem cells have been found in tissues such as the brain, bone marrow, blood, blood vessels, skeletal muscles, skin, and the liver. They usually remain in a non-dividing state for many years, as they are only activated by disease or tissue injury. Adult stem cells can also divide indefinitely, enabling them to renew a range of cell types from the originating organ or even regenerate the entire original organ.

Embryonic stem cells:

Embryonic stem cells are taken from a few days old human embryo that is in the blastocyst phase of development. The embryos are usually extras that have been created in clinics where several eggs are fertilised in a test tube, but only one is implanted into a woman. When a male's sperm fertilises a female's ovum, a single cell called a zygote is formed. The single zygote cell then begins a series of divisions, forming 2, 4, 8, 16 cells, etc. After four to six days - before implantation in the uterus - this mass of cells is called a blastocyst. The blastocyst consists of an inner cell mass (embryoblast) and an outer cell mass (trophoblast). The outer cell mass becomes part of the placenta, and the inner cell mass is the group of cells that will differentiate to become all the structures of an adult organism. This latter mass is the source of embryonic stem cells - totipotent cells (cells with total potential to develop into any cell in the body).

For a normal pregnancy, the blastocyst stage continues until implantation of the embryo in the uterus, at which point the embryo is referred to as a fetus. However, when extracting embryonic stem cells, the blastocyst stage acts as a signal as to when to isolate stem cells by placing the "inner cell mass" of the blastocyst into a culture dish containing a nutrient-rich broth. Lacking the necessary stimulation to differentiate into specialised cell types, they begin to divide and replicate while still maintaining their ability to become any cell type in the human body. Eventually, these undifferentiated cells can be stimulated to create specialized cells, when “instructed to” by scientists.


A human embryonic stem cell colony on mouse embryonic fibroblast feeder layer.
(^Taken from Wikipedia)

Stem cell cultures:
Stem cells are either extracted from adult tissue or from a dividing zygote in a culture dish. Once extracted, scientists place the cells in a controlled culture that prohibits them from further specializing or differentiating but usually allows them to divide and replicate. The process of growing large numbers of embryonic stem cells has been easier than growing large numbers of adult stem cells, but progress is being made for both cell types.

Stem cell lines:

Once stem cells have been allowed to divide in a controlled culture, the collection of healthy, dividing, and undifferentiated cells is called a stem cell line. These stem cell lines are subsequently managed and shared among researchers. Once under control, the stem cells can be stimulated to specialize as directed by a researcher - a process known as directed differentiation. Embryonic stem cells are able to differentiate into more cell types than adult stem cells.

Potency:

As mentioned earlier, stem cells are categorised by their potential to differentiate into other types of cells. Embryonic stem cells are the most potent since they must become every type of cell in the body of a baby. After much research, the full classification includes:

1. Totipotent - the ability to differentiate into all possible cell types. (For example, the zygote formed at egg fertilization and the first few cells that result from the division of the zygote.)

2. Pluripotent - the ability to differentiate into almost all cell types. (For example, *embryonic stem cells.)

3. Multipotent - the ability to differentiate into a closely related family of cells. Examples include hematopoietic* stem cells that can become red and white blood cells or platelets. )

*A hematopoietic stem cell is a cell isolated from the blood or bone marrow that can renew itself and differentiate to a variety of specialized cells.

4. Oligopotent - the ability to differentiate into a few cells.

5. Unipotent - the ability to only produce cells of their own type, but have the property of self-renewal required to be labeled a stem cell. Examples include adult muscle stem cells.

*Embryonic stem cells are considered pluripotent instead of totipotent because they do not have the ability to become part of the extra-embryonic membranes or the placenta, unlike the zygote.

Identification of stem cells:

Although there is not complete agreement among scientists of how to identify stem cells, most tests are based on the properties of making sure that stem cells are undifferentiated and capable of self-renewal. One way to identify stem cells in a lab, and the standard procedure for testing bone marrow or hematopoietic stem cell (HSC), is by transplanting one cell to save an individual without HSCs. If the stem cell produces new blood and immune cells, it demonstrates its potency.

To test whether human embryonic stem cells are pluripotent, scientists allow the cells to differentiate spontaneously in cell culture, manipulate the cells so they will differentiate to form specific cell types.

Research with stem cells:

There are several reasons why scientist and researchers are interested in stem cells. Although stem cells do not serve any one function, many have the ability to serve any function after they are “instructed” to specialize. Every cell in the body, for example, is derived from first few stem cells formed in the early stages of embryological development. Therefore, stem cells extracted from embryos can be used to become any desired cell type. This makes stem cells powerful enough to regenerate damaged tissue under the right conditions.

Organ and tissue regeneration:

Tissue regeneration is probably the most important possible use of stem cell research. Currently, organs must be donated and transplanted, but the demand for organs far exceeds supply. Stem cells could potentially be used to grow a particular type of tissue or organ if directed to differentiate in a certain way. Stem cells that lie just beneath the skin, for example, can be used to regenerate new skin tissue that can be given to burn victims.

Brain disease treatment:

Additionally, replacement cells and tissues may be used to treat brain disease such as Parkinson's and Alzheimer's by replenishing damaged tissue, bringing back the specialized brain cells that keep unneeded muscles from moving.

Cell deficiency therapy:

Since the nervous system, the pancreas and the heart all regenerate too poorly to restore itself after serious injury, healthy heart cells developed in a laboratory may one day be transplanted into patients with heart disease, repopulating the heart with healthy tissue and thus saving them. Similarly, people with diabetes may receive pancreatic cells to replace the insulin-producing cells that have been lost or destroyed by the patient's own immune system. However, the only current therapy is a pancreatic transplant, and it is unlikely to occur due to a small supply of pancreases available for transplant.

Blood disease treatments:

Adult hematopoietic stem cells found in blood and bone marrows have been used for years to treat diseases such as leukemia, sickle cell anemia, and other immunodeficiencies*. These cells are capable of producing all blood cell types, such as red blood cells that carry oxygen to white blood cells that fight disease. Even then difficulties arise in the extraction of these cells through the use of invasive bone marrow transplants. However hematopoietic stem cells have also been found in the umbilical cord and placenta. I found out that this has led some scientists to call for an umbilical cord blood bank to make these powerful cells more easily obtainable and to decrease the chances of a body's rejecting therapy.

*A immunodeficiency is a immunological disorder in which some part of the body's immune system is inadequate and resistance to infectious diseases is reduced.

General scientific discovery:

Stem cell research is also useful for learning about human development. Undifferentiated stem cells eventually differentiate partly because a particular gene is turned on or off. Stem cell researchers may help to clarify the role that genes play in determining what genetic traits or mutations we receive. Cancer and other birth defects are also affected by abnormal cell division and differentiation. New therapies for diseases may be developed if we better understand how these agents attack the human body.

Another reason why stem cell research is being pursued is to develop new drugs. Scientists could measure a drug's effect on normal tissue by testing the drug on tissue grown from stem cells rather than testing the drug on human volunteers.

Stem cell controversy:

Despite all of the possibilities that stem cells might promise, there have been debates surrounding stem cell research. The main concern however, surrounds embryonic stem cell research, which of course is most expected. The main reason is that it requires the destruction of a human blastocyst. That is, a fertilized egg was not given the chance to develop into a fully-developed human.

Chimeras:

There is also the issue of the creation of chimeras. A chimera is an organism that has both human and animal cells or tissues. This is because, very often in stem cell research, human cells are inserted into animals (like mice or rats) and allowed to develop. This creates the opportunity for researchers to see what happens when stem cells are implanted. Many people, however, object to the creation of an organism that is "part human".

Conclusion:

Putting aside the legal issues and debates, stem cells would be very useful to mankind if we are able to fully apply it. The death rate of countries would drop rapidly, and many diseases that we are unable to cure now, would be then. Perhaps this might be a stepping stone towards living forever, where stem cells would be industrially produced and people would receive such treatments to replace their old and dying cells, making them young forever!

Bibliography:


http://en.wikipedia.org/wiki/Stem_cell

http://stemcells.nih.gov/info/scireport/chapter5.asp

wordnetweb.princeton.edu/perl/webwn

http://www.bionetonline.org/english/content/sc_cont1.htm

http://www.news-medical.net/health/What-are-Stem-Cells.aspx

http://www.cellmedicine.com/description.asp

http://www.wisegeek.com/what-is-stem-cell-research.htm

http://alzheimers.about.com/od/research/f/stemcells_alz.htm

http://www.cordblood.com/cord_blood_banking_with_cbr/banking/stem_cells.asp

http://www.yourdictionary.com/answers/where/where-do-stem-cells-come-from.html

http://arthritis.about.com/od/stemcell/g/stemcell.htm

http://www.leaderu.com/focus/stemcell.html