Stem Cell Technology
About the presenter
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Dr.B.Victor is a highly experienced postgraduate biology
teacher, recently retired from the reputed educational
institution St. Xavier’ s College, Palayamkottai, India627001.
He was the dean of sciences and assistant controller of
examinations.
He has more than 32 years of teaching and research
experience
He taught a diversity of courses ranging from preuniversity to post graduate classes.
Send your comments to : bonfiliusvictor@gmail.com
Presentation outline
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Stem cell
characteristics
Embryonic stem cells
(ESC)
Adult Stem cells (ASC)
Stem Cell Lines
Classification of stem
cells
Culture and
Stem cell therapy
Recent Developments
Diversity of Human Cells
Adult humans consist of more than 200 kinds of
cells.
They are nerve cells (neurons), muscle cells
(myocytes), skin (epithelial) cells, blood cells
(erythrocytes, monocytes, lymphocytes, etc.), bone
cells (osteocytes), and cartilage cells
(chondrocytes).
cells essential for embryonic development but not
incorporated into the body of the embryo, include
the extra-embryonic tissues, placenta, and
umbilical cord.
All of these cells are generated from a single,
totipotent cell, the zygote, or fertilized egg.
What is a stem cell?
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A stem cell is a "blank" cell/
precursor cell that can give rise to
multiple tissue types such as a skin,
muscle, or nerve cell.
 A stem cell is essentially the
building block of the human body.
Features of Stem Cells
1.
2.
3.
4.
5.
Stem Cells are very unique cells.
Stem Cells have the amazing ability to develop
into several distinct cell types in the body.
Stem Cells can be used as a repair system for the
body.
Stem Cells can theoretically divide without limit
in a living organism in order to replenish various
types of cells.
When a stem cell divides, each new cell has the
potential to either remain a stem cell or become
another type of cell with a more specialized
function (i.e. a muscle cell, a red blood cell, a
brain cell, etc.).
Three unique properties of stem cells
Stem cells are capable of dividing and
renewing themselves for long periods;
They are “unspecialized” and they can
give rise to specialized cell types.
A stem cell is "uncommitted," until it
receives a signal to develop into a
specialized cell.
Asymmetric division of
stem cells
Stem cells have the ability to
divide asymmetrically .
One portion of the cell
division becomes a
differentiated cell while the
other becomes another stem
cell.
1. Stem cells are unspecialized
A stem cell does not have any tissue-specific
structures that allow it to perform specialized
functions.
A stem cell cannot work with its neighbors to
pump blood through the body (like a heart
muscle cell);
It cannot carry molecules of oxygen through
the bloodstream (like a red blood cell); and
It cannot fire electrochemical signals to
other cells that allow the body to move (like a
nerve cell).
2.Stem cells are capable of dividing and
renewing themselves for long periods.
Stem cells may replicate many times.
When cells replicate themselves many times
it is called proliferation.
The stem cells that proliferate for many
months in the laboratory can yield millions
of cells.
Stem cells are capable of long-term selfrenewal.
3.Stem cells can give rise to
specialized cells
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When unspecialized stem cells give rise to
specialized cells, the process is called
differentiation.
There are signals inside and outside cells that
trigger stem cell differentiation.
The internal signals are controlled by a cell's
genes.
The external signals include chemicals secreted by
other cells, physical contact with neighboring cells,
and certain molecules in the microenvironment
4.Stem cells exist in both embryos
and adults.
In embryos, stem cells function to
generate new organs and tissues.
In adults, they function to replace
cells during the natural course of
cell turnover.
Distinguishing Features of
Progenitor/Precursor Cells and Stem Cells.
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A stem cell is an unspecialized cell that develops
into a variety of specialized cell types.
a stem cell divides and gives rise to one
additional stem cell and a specialized cell.
Example: a hematopoietic stem cell produce a
second generation stem cell and a neuron.
A progenitor cell (a precursor cell) is
unspecialized that is capable of undergoing cell
division and yielding two specialized cells.
Example: a myeloid progenitor/precursor cell
undergoing cell division to yield two specialized
cells (a neutrophil and a red blood cell).
Stem cell Classes
Embryonic Type stem cells
1.Embryonic Type
Embryonic Stem Cells
Embryonic Germ Cells
Adult type Stem cells
2. Adult Type
Umbilical Cord Stem Cells
Placental Stem Cells
Adult Stem Cells
Sources of embryonic type stem
cells
* Embryos - Embryonic stem cells are
obtained by harvesting living embryos which
are generally 5-7 days old. The removal of
embryonic stem cells invariably results in the
destruction of the embryo.
* Fetuses - Another kind of stem cell, called an
embryonic germ cell, can be obtained from
either miscarriages or aborted fetuses.
Sources of adult type stem cells
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Umbilical Cords, Placentas and Amniotic
Fluid - Adult type stem cells can be derived
from various pregnancy-related tissues.
Adult Tissues - In adults, stem cells are
present within the bone marrow, liver,
epidermis, retina, skeletal muscle, intestine,
brain, dental pulp and elsewhere.
Cadavers - Neural stem cells have been
removed from specific areas in post-mortem
human brains as late as 20 hours following
death.
Comparison of embryonic and
adult stem cells
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Advantages of Embryonic Stem Cell
1. Flexible - appear to have the
potential to make any cell.
2. Immortal - one embryonic stem cell
line can potentially provide an endless
supply of cells with defined
characteristics.
3. Availability - embryos from in vitro
fertilization clinics.
Disadvantages of Embryonic
Stem Cell
1. Difficult to differentiate uniformly and
homogeneously into a target tissue.
2. Immunogenic - embryonic stem cells
from a random embryo donor are likely
to be rejected after transplantation
3. Tumorigenic - capable of forming
tumors or promoting tumor formation.
4. Destruction of developing human life.
Advantages of Adult Stem Cell
1. Adult stem cells from bone marrow and
umbilical cords appear to be as flexible as the
embryonic type
2. Somewhat specialized - inducement may be
simpler.
3. Not immunogenic - recipients who receive the
products of their own stem cells will not
experience immune rejection.
4. Relative ease of procurement - some adult stem
cells are easy to harvest (skin, muscle, marrow,
fat)
5. Non-tumorigenic-tend not to form tumors.
6. No harm done to the donor.
Disadvantages of Adult stem cells
1. Limited quantity - can
sometimes be difficult to obtain in
large numbers.
2. Finite - may not live as long as
embryonic stem cells in culture.
3. Less flexible - may be more
difficult to reprogram to form
other tissue types
Why are adult stem cells preferable to
embryonic stem cells?
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Adult stem cells are naturally exist in our
bodies, and they provide a natural repair
mechanism for many tissues.
They belong in the microenvironment of an
adult body, while embryonic stem cells
belong in the microenvironment of the
early embryo, where they tend to cause
tumors and immune system reactions.
Superior features of ESCs
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Embryonic stem cells are easier to
identify, isolate and harvest.
There are more of them.
They grow more quickly and easily in
the lab than adult stem cells.
They can be more easily manipulated
(they are more plastic)
Classification based on level
of differentiation
Totipotent
Pluripotent
Multipotent
Unipotent stem cells
Types of Stem cells
Totipotent stem cells
1.
2.
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The fertilized egg is said to be totipotent
from the Latin totus, meaning “entire”..
It has the potential to generate all the
cells and tissues that make up an embryo.
It supports embryonic development in
utero.
Pluripotent stem cells
Pluripotent stem cells are descendants
of the totipotent stem cells of the
embryo.
These cells develop about four days
after fertilization
They can differentiate into any cell
type, except for totipotent stem cells
and the cells of the placenta.
Pluripotent stem cells
“Pluri” is derived from the Latin
plures means several or many.
Thus, pluripotent cells have the
potential to give rise to any type of
cell.
Pluripotent stem cells
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These cells cannot re-create a
complete organism but
differentiate to a large number of
mature tissue types, for example,
brain and muscle.
Multipotent stem cells
Multipotent stem cells are descendents of
pluripotent stem cells and antecedents of
specialized cells in particular tissues.
For example, hematopoietic stem cells,
which are found primarily in the bone
marrow, give rise to all of the cells found in
the blood,including red blood cells, white
blood cells, and platelets.
Unipotent stem cell
Unipotent stem cell, a term that is
usually applied to a cell in adult
organisms, means that the cells in
question are capable of differentiating
along only one lineage.
"Uni" is derived from the Latin word
unus, which means one.
Progenitor cells
Progenitor cells (or
unipotent stem cells) can
produce only one cell type.
For example, erythroid
progenitor cells
differentiate into only red
blood cells.
Blood is made in the Bone MarrowBlood Cell Development
“Terminally differentiated" cells
At the end of the long chain of cell
divisions are "terminally
differentiated" cells, such as a liver
cell or lung cell, which are
permanently committed to specific
functions.
Adult stem cells (ASC)
Adult stem cells or
somatic stem cells
Adult stem cells are undifferentiated cells.
They are found in small numbers in most
adult tissues.
They can also be extracted from umbilical
cord blood.
They are also called “somatic stem cells,”
They are multipotent in nature.
They give rise to a closely related family of
cells within the tissue.
An example is hematopoietic stem cells,
which form all the various cells in the
blood.
Adult stem cell plasticity and
transdifferentiation
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ability to differentiate
into multiple cell types is
called plasticity or
transdifferentiation.
Differentiation
pathways of adult stem cells
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Neural stem cells in the brain give rise to its three
major cell types: nerve cells (neurons) and two
categories of non-neuronal cells — astrocytes and
oligodendrocytes.
Epithelial stem cells in the lining of the digestive tract
occur in deep crypts and give rise to several cell types:
absorptive cells, goblet cells, Paneth cells, and
enteroendocrine cells.
Skin stem cells occur in the basal layer of the
epidermis and at the base of hair follicles.
The epidermal stem cells give rise to keratinocytes,
which migrate to the surface of the skin and form a
protective layer.
The follicular stem cells can give rise to both the hair
follicle and to the epidermis
The similarities and differences between
embryonic and adult stem cells
Embryonic stem cells can become all cell types of
the body because they are pluripotent.
Adult stem cells are generally limited to
differentiating into different cell types of their
tissue of origin.
However, some evidence suggests that adult stem
cell plasticity may exist, increasing the number
of cell types a given adult stem cell can become.
Human embryonic and adult stem
cells
A potential advantage of using stem cells from
an adult is that the patient's own cells could be
expanded in culture and then reintroduced into
the patient.
The use of the patient's own adult stem cells
would mean that the cells would not be rejected
by the immune system.
Embryonic stem cells from a donor introduced
into a patient could cause transplant rejection.
Umbilical cord stem cells
Blood from the placenta and umbilical
cord that are left over after birth is a rich
source of hematopoietic stem cells.
These so-called umbilical cord stem cells
have been shown to be able to differentiate
into bone cells and neurons, as well as the
cells lining the inside of blood vessels.
Importance of
Cord blood stem cells
Cord blood stem cells have been used to
treat 70 different diseases, including
leukemia, lymphoma, and inherited
diseases (of red blood cells, the immune
system, and certain metabolic
abnormalities).
Cord blood collection is a safe, simple
procedure that poses no risk to the
mother or newborn baby.
Embryonic Stem Cells (ESC).
Embryonic Stem Cells
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Embryonic Stem Cells are derived from
embryos that develop from eggs that have
been fertilized in vitro.
Embryonic Stem Cells are never derived
from eggs fertilized inside of a woman's
body.
The embryos from which Human Embryonic
Stem Cells are derived are typically four or
five days old and are a hollow microscopic
ball of cells called the blastocyst
Embryonic stem cells (ESC)
Embryonic stem cells (ESC), as their name
suggests, are derived from embryos.
Specifically, embryonic stem cells are derived
from embryos that develop from eggs that have
been fertilized in vitro —donated for research
purposes with informed consent of the donors.
They are not derived from eggs fertilized in a
woman's body.
Properties of Embryonic Stem
Cells
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a Derived from the inner cell mass of the
blastocyst.
a Capable of undergoing an unlimited number of
symmetrical divisions without differentiating
(long-term self-renewal).
Exhibit and maintain a stable, full (diploid), normal
complement of chromosomes (karyotype).
Pluripotent ES cells can give rise to differentiated
cell types that are derived from all three primary
germ layers of the embryo (endoderm, mesoderm,
and ectoderm).
Potential sources of stem cells are:
fetal tissue that becomes available after an abortion
excess embryos from assisted reproductive technologies
such as commonly used in fertility clinics
embryos created through in vitro fertilization specifically
for research purpose, and
embryos created asexually as a result of the transfer of a
human somatic cell nucleus to an egg with its own
nucleus removed.
Other sources of stem cells are those from umbilical cord
blood, and bone marrow.
In addition, neural stem cells, haematopoetic stem cells
and mesenchymal stem cells can be harvested from fetal
blood and fetal tissue.
Cell therapy.
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Treatment of neural diseases such as
Parkinson's disease, Huntington’s disease
and Alzheimer's disease.
Stem cells could be used to repair or replace
damaged neurons.
Repair of damaged organs such as the liver
and pancreas.
Treatments for AIDS.
Stem cell transplantation (SCT)
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Stem cell transplantation (SCT) is the term
now used in preference to bone marrow
transplantation (BMT).
When a patient's bone marrow fails to
produce new blood cells, for whatever
reason, he or she will develop anaemia, be
prone to frequent, persistent infections and
may develop serious bleeding problems.
In order to restore blood cell production a
patient may be given healthy stem cells.
Therapeutic cloning/ somatic cell
nuclear transfer
Scientists first remove the nucleus from a normal
egg cell of a woman. They then extract a nucleus
from a somatic cell - that is, any body cell other
than an egg or sperm—from a patient who needs an
infusion of stem cells to treat a disease or injury,
and insert the nucleus into the egg.
The egg, which now contains the patient's genetic
material, is allowed to divide and soon forms a
hollow sphere of cells called a blastocyst.
Cells from the inner cell mass are isolated and used
to develop new embryonic stem cell (ESC) lines.
Strategy for therapeutic cloning
and tissue engineering
Stem cells and cancer treatment
Intense chemotherapy damages a person’s bone
marrow, where the stem cells for blood reside.
Depleted of a fresh supply of blood cells, the
patient is left vulnerable to infection, anemia and
bleeding.
These side effects of chemotherapy are often
treated with a bone marrow transplant.
“Transplanting bone marrow tissue into a chemocancer patient may involve hundreds of thousands
or millions of cells – of which only two or three
may be actual stem cells.
It would be much more efficient if you could inject
a thousand purified stem cells,”
Therapeutic cloning for
tissue repair
One human organ, skin, is readily
cultured to provide replacement tissue
for burns victims.
Healthy skin cells from the patient can
be grown rapidly in vitro to provide
self-compatible skin grafts.
Is Stem Cell Research Ethical?
* Embryonic Stem Cells - always morally objectionable,
because the human embryo must be destroyed in order to
harvest its stem cells.
* Embryonic Germ Cells - morally objectionable when
utilizing fetal tissue derived from elective abortions, but
morally acceptable when utilizing material from spontaneous
abortions (miscarriages) if the parents give informed consent.
* Umbilical Cord Stem Cells - morally acceptable, since the
umbilical cord is no longer required once the delivery has
been completed.
* Placentally-Derived Stem Cells - morally acceptable, since
the afterbirth is no longer required after the delivery has
been completed.
* Adult Stem Cells - morally acceptable.
Sources Consulted
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Odorico, J.S., Kaufman, D.S., and Thomson, J.A. (2001).
Multilineage differentiation from human embryonic
stem cell lines. Stem Cells. 19, 193 -204.
Smith, A.G. (2001). Origins and properties of mouse
embryonic stem cells. Annu. Rev. Cell. Dev. Biol.
Thomson, J.A. and Marshall, V.S. (1998). Primate
embryonic stem cells. Curr. Top. Dev. Biol. 38, 133-165.
Chandross, K.J. and Mezey, E. (2001). Plasticity of
adult bone marrow stem cells. Mattson, M.P. and Van
Zant, G. eds. (Greenwich, CT: JAI Press).
Slack, J.M. (2000). Stem cells in epithelial tissues.
Science. 287, 1431-1433.
Sources Consulted
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Dzierzak, E., Medvinsky, A., and de Bruijn, M. (1998).
Qualitative and quantitative aspects of haematopoietic
cell development in the mammalian embryo. Immunol.
Today. 19, 228-236.
MacKey, M.C. (2001). Cell kinetic status of
haematopoietic stem cells. Cell. Prolif. 34, 71-83.
J. A. Thomson, et al., 'Embryonic stem cell lines derived
from human blastocysts', Science, no. 5391, vol. 282,
November 1998, pp. 1145–7.
B. E. Reubinoff, M. F. Pera, C-Y Fong, A. Trounson and A.
Bongso, 'Embryonic stem cell lines from human
blastocysts: somatic differentiation in vitro', Nature
Biotechnology, vol. 18, pp. 399–404, 01 April 2000.