Title: Stem Cell Technology
1Stem Cell Technology
Presented by
Dr.B.Victor, St.Xavier's College, Palayamkottai
627002 India
2About the presenter
- Dr.B.Victor is a highly experienced postgraduate
biology teacher, recently retired from the
reputed educational institution St. Xavier s
College, Palayamkottai, India-627001. - 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
pre- university to post graduate classes. - Send your comments to bonfiliusvictor_at_gmail.com
3Presentation outline
- 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
4Diversity 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.
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6What is a stem cell?
- 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.
7Features of Stem Cells
- 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.).
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9Three 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.
10Asymmetric 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.
111. 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).
122.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 self-renewal.
133.Stem cells can give rise to specialized cells
-
- 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
14 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.
15Distinguishing Features of Progenitor/Precursor
Cells and Stem Cells.
- 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).
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17Stem cell Classes
18Embryonic Type stem cells
19Adult type Stem cells
20Sources 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.
21Sources of adult type stem cells
- 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.
22 Comparison of embryonic and adult stem cells
- 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.
23Disadvantages of Embryonic Stem Cell
- Difficult to differentiate uniformly and
homogeneously into a target tissue. - Immunogenic - embryonic stem cells from a random
embryo donor are likely to be rejected after
transplantation - Tumorigenic - capable of forming tumors or
promoting tumor formation. - Destruction of developing human life.
24Advantages of Adult Stem Cell
- Adult stem cells from bone marrow and umbilical
cords appear to be as flexible as the embryonic
type - Somewhat specialized - inducement may be simpler.
- Not immunogenic - recipients who receive the
products of their own stem cells will not
experience immune rejection. - Relative ease of procurement - some adult stem
cells are easy to harvest (skin, muscle, marrow,
fat) - Non-tumorigenic-tend not to form tumors.
- No harm done to the donor.
25Disadvantages 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
26Why are adult stem cells preferable to embryonic
stem cells?
- 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.
27Superior features of ESCs
- 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)
28Classification based on level of differentiation
- Totipotent
- Pluripotent
- Multipotent
- Unipotent stem cells
29Types of Stem cells
30Totipotent stem cells
- 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.
31Pluripotent 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.
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33Pluripotent 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.
34Pluripotent stem cells
- These cells cannot re-create a complete organism
but differentiate to a large number of mature
tissue types, for example, brain and muscle.
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36Multipotent 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.
37Unipotent 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.
38Progenitor cells
- Progenitor cells (or unipotent stem cells) can
produce only one cell type. - For example, erythroid progenitor cells
differentiate into only red blood cells.
39Blood is made in the Bone Marrow-Blood Cell
Development
40Terminally 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.
41Adult stem cells (ASC)
42Adult 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.
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44Adult stem cell plasticity and transdifferentiatio
n
- This ability to differentiate into multiple cell
types is called plasticity or transdifferentiation
.
45Differentiation pathways of adult stem cells
- 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
46The 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.
47Human 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.
48Umbilical 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.
49Importance 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.
50Embryonic Stem Cells (ESC).
51Embryonic Stem Cells
- 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
52Embryonic 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.
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55Properties of Embryonic Stem Cells
- 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).
56Potential 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.
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58Cell therapy.
- Treatment of neural diseases such as Parkinson's
disease, Huntingtons 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.
59Stem cell transplantation (SCT)
- 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.
60Therapeutic 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 spermfrom 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.
61Strategy for therapeutic cloning and tissue
engineering
62Stem cells and cancer treatment
- Intense chemotherapy damages a persons 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
chemo-cancer 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,
63Therapeutic 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.
64Is 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.
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66Sources Consulted
- 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.
67Sources Consulted
- 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. 11457. - 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. 399404, 01 April 2000.
68Thank you