STEM CELL RESEARCH
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Introduction
The body is made up of about 200 different kinds of specialized cells such as muscle cells, nerve
cells, fat cells and skin cells. All cells in the body come from stem cells. A stem cell is a cell that
is not yet specialized. The process of specialization is called differentiation. Once the
differentiation pathway of a stem cell has been decided, it can no longer become another type
of cell on its own.
Stem cells can:
•
self-renew to make more stem cells
•
differentiate into a specialized cell type
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History of stem cell research
1998 - Researchers first extract stem cells from human embryos
1999 - First Successful human transplant of insulin-making cells
2001 - President Bush restricts federal funding for embryonic stem-cell research
2002 -Juvenile Diabetes Research Foundation International creates $20 million fund-raising
effort to support stem-cell research
2004 - Harvard researchers grow stem cells from embryos using private funding
Definition
A cell that has the ability to continuously divide and differentiate (develop) into various other
kind(s) of cells/tissues.
Types of stem cells
Embryonic stem cells
Embryonic stem cells come from a five to six-day-old embryo. They have the ability to form
virtually any type of cell found in the human body.
Source of Embryonic stem cells:


Embryos created in vitro fertilization
Aborted embryos
Adult stem cells
Adult stem cells are undifferentiated cells found among specialized or differentiated cells in a
tissue or organ after birth. Based on current research they appear to have a more restricted
ability to produce different cell types and to self-renew.
Source of adult stem cells:


Limited tissues (bone marrow, muscle, brain)
Discrete populations of adult stem cells generate replacements for cells
that are lost through normal wear and tear, injury or disease
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

Placental cord
Baby teeth
Characteristics of stem cells
 Stem cells can regenerate
◦
Unlimited self renewal through cell division
 Stem cells can specialize
◦
Under certain physiologic or experimental conditions stem cells then become
cells with special functions such as:

Beating cells of the heart muscle

Insulin-producing cells of the pancreas
Kinds of Stem Cells
 Totipotent
◦
Total potential to differentiate into any adult cell type
◦
Total potential to form specialized tissue needed for embryonic development
 Pluripotent
◦
Potential to form most or all 210 differentiated adult cell types
 Multipotent
◦
Limited potential
◦
Forms only multiple adult cell types

Oligodendrocytes

Neurons
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Stem cell type
Totipotent
Pluripotent
Multipotent
Description
Each cell can develop into a
new individual
Cells can form any (over 200)
cell types
Cells differentiated, but can
form a number of other
tissues
Examples
Cells from early (1-3 days)
embryos
Some cells of blastocyst (5 to
14 days)
Fetal tissue, cord blood, and
adult stem cells
Differences between Embryonic stem cells & Adult Stem Cells
Embryonic stem cells
Totipotent
Known Source
Large numbers can be harvested from embryos
May cause immune rejection
Adult Stem Cells
Multi or pluripotent
Unknown source
Limited numbers, more difficult to isolate
Less likely to cause immune rejection,
since the patient’s own cells can be used
Stem cell applications
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Tissue repair: Regenerate spinal cord, heart tissue or any other major tissue in the body.
•
Treatment of cancer: Studies show leukemia patients treated with stem cells emerge
free of disease. Injections of stem cells have also reduced pancreatic cancers in some
patients.
•
Treatment of Heart Disease: Adult bone marrow stem cells injected into the hearts are
believed to improve cardiac function in victims of heart failure or heart attack.
•
Treatment of Type I Diabetes: Embryonic Stems Cells might be trained to become
pancreatic islets cells needed to secrete insulin.
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