- What are stem cells?
- What do stem cells do?
- How do stem cells do their jobs (differentiate)?
- Are there limits to the cell types into which a stem cell can differentiate?
- What are the different stem cell types?
- What are the risks?
- How can we use stem cells?
- A couple of terms
What are stem cells?
Stem cells are cells in your body that have two major capabilities: self-renewal and potency:
- Self-renewal: Can divide by itself to make more stem cells
- Potency: Can differentiate – or turn into – other cell types, or specialized cells (e.g. muscle fiber cells, nerve cells, etc. as shown in the picture)
(Picture source: http://publications.nigms.nih.gov/insidethecell/chapter3.html)
Notice how the stem cells in the center of the picture are embryonic stem cells. We'll touch on these different types later.
What do I mean by cell types? Well, our organs and tissues are made up of different types of cells. While all cells have common functions such as cellular respiration – releasing energy from the food we eat, each specific type of cell has its specific properties. There are cardiovascular cells that beat to allow the heart to pump blood, nerve cells that are elongated to efficiently send electrical messages from the brain, muscle fiber cells that are cylindrical and thin to allow for muscle contraction. Stem cells can turn into one or more of these types of specialized cells.
Notice how the stem cells in the center of the picture are embryonic stem cells. We'll touch on these different types later.
What do I mean by cell types? Well, our organs and tissues are made up of different types of cells. While all cells have common functions such as cellular respiration – releasing energy from the food we eat, each specific type of cell has its specific properties. There are cardiovascular cells that beat to allow the heart to pump blood, nerve cells that are elongated to efficiently send electrical messages from the brain, muscle fiber cells that are cylindrical and thin to allow for muscle contraction. Stem cells can turn into one or more of these types of specialized cells.
What do stem cells do?
The essential job of stem cells is to replace other cells in
our bodies. Have you ever wondered how your skin heals after a paper cut or
scrape? The answer is stem cells, which have the ability to move to the areas
of the body that need healing. After injury or disease, a squadron of stem
cells mobilizes to restore your wound or immune system. Stem cells are
necessary because specialized cells do not divide.
Stem cells were also responsible for developing you from a
zygote – a fertilized cell formed after a union of the sperm and egg from your
parents – to your human body today. On a similar level of importance, stem
cells keep us alive. The amount of stem cells in our bodies decrease with age;
when we run out of stem cells, we die.
How do stem cells do their jobs (differentiate)?
Differentiation is a gradual process of turning on and off
specific genes in the cell for the cell to specialize. All cells in your body
have the same DNA. The only difference between specific cell types is which
genes are activated. To specialize, signals from the environment trigger the
necessary genes in the stem cell.
Diagram showing different aspects that can affect stem cells:
Are there limits to the cell types into which a stem cell can differentiate?
YES. Different stem cells have different potencies, meaning
they have different amounts of cell types into which they can specialize:
- Totipotent – can form an entire organism on its own. (The only example is a fertilized egg.)
- Pluripotent – can form any specialized cell type in the body (except the placenta). (Example: embryonic stem cells)
- Multipotent – can form a few cell types, usually ones related to each other. (Example: many adult stem cell types such as hematopoietic stem cells that can make red blood cells, white blood cells, and platelets)
- Unipotent – can form only one cell type. (Example: a few adult stem cell types such as skin and liver stem cells)
Diagram of different potencies (basically, totipotent and pluripotent stem cells can become any of the kinds of specialized stem cells, while multipotent stem cells have to stay within related groups; induced pluripotent stem cells are multipotent stem cells altered to become like pluripotent stem cells):
(Picture source: http://philschatz.com/anatomy-book/contents/m46036.html)
What are the different stem cell types?
The different types of stem cells are designated by their
sources:
- Embryonic stem cells – from embryos from in-vitro fertilization clinics; pluripotent
- Fetal stem cells – from aborted fetuses; multipotent – not pluripotent but higher potency than adult stem cells
- Adult stem cells – from theoretically every organ of the human body; multipotent and unipotent
- Induced pluripotent stem cells – altered (genetic reprogramming with viruses) from adult stem cells; pluripotent
Note the different potencies, and keep this in mind when you are evaluating information from stem cell clinics. Adult stem cells are not pluripotent like embryonic stem cells.
Diagram showing different stem cell types:
What are the risks?
What other cells are good at self-renewal? Cancer cells. When a stem cell is damaged or altered, it can become a cancer stem cell, a stem cell without necessary limitations in its processes of division. If there is even one cancer cell that evades built-in suicide measures and the immune system, a new tumor can be formed.
Diagram showing different stem cell types:
(Picture source: https://www.pall.com/main/biopharmaceuticals/frequently-asked-questions-cell-therapy.page)
What are the risks?
What other cells are good at self-renewal? Cancer cells. When a stem cell is damaged or altered, it can become a cancer stem cell, a stem cell without necessary limitations in its processes of division. If there is even one cancer cell that evades built-in suicide measures and the immune system, a new tumor can be formed.
How can we use stem cells?
This bit of information is not as important in relation to
clinics, but it is still useful to know. Because of the flexible self-renewal
and potency properties of stem cells as well as their ability to move to areas of
the body in need, researchers have been using them for various advancements:
- Regenerative medicine – Sometimes there are insufficient stem cells to heal injuries, or old age causes a lack of stem cells. As well, the demand for donated organs is greater than the supply. Regenerative medicine can help both of these problems and involves differentiation of stem cells to use in our bodies.
- Developmental studies – Stem cells are being used to study the early development of humans, which cannot be accomplished in humans.
- Disease modeling – Mutations can be introduced into stem cells to allow for the study of diseases and their mechanisms in the body.
- Drug discovery – Stem cells are being used to make cells or tissues on which to test drugs.
- Toxicity screening - Stem cells are being used to make cells on which to test safety of drugs.
- Drug delivery – Because stem cells can “home in” on the damaged tissues that need them, they are being used to deliver medicine.
Basically, stem cells have quite a potential to help us (but we have to be aware of limitations).
A couple of terms
Here are some general terms with which you may need to familiarize:
- Autologous – Stem cells used to treat the patient are from the patient.
- Allogeneic – Stem cells used to treat the patient are from a donor.
Now that you know the basics, it's time to see what Stemedix claims to offer.
Source: Knoepfler, P. (2013). Stem cells: An insider's guide. Singapore: World Scientific Publishing Pte.
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