Stem Cell Technology

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Stem Cell Technology
Presented by
Dr.B.Victor, St.Xavier's College, Palayamkottai
627002 India
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About 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

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Presentation 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

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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.

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What 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.

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Features of Stem Cells

1. Stem Cells are very unique cells.
2. Stem Cells have the amazing ability to develop
   into several distinct cell types in the body.
3. Stem Cells can be used as a repair system for the
   body.
4. Stem Cells can theoretically divide without
   limit in a living organism in order to replenish
   various types of cells.
5. 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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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.

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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.

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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).

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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 self-renewal.

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3.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

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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.

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Distinguishing 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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Stem cell Classes
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Embryonic Type stem cells
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Adult type Stem cells
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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.

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Sources 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.

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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.

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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.

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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.

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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

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Why 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.

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Superior 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)

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Classification based on level of differentiation

• Totipotent
• Pluripotent
• Multipotent
• Unipotent stem cells

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Types of Stem cells
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Totipotent stem cells

1. The fertilized egg is said to be totipotent from
   the Latin totus, meaning entire..
2. It has the potential to generate all the cells
   and tissues that make up an embryo.
3. It supports embryonic development in utero.

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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.

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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.

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Pluripotent 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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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.

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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.

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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.

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Blood is made in the Bone Marrow-Blood Cell
Development
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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.

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Adult stem cells (ASC)
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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.

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Adult stem cell plasticity and transdifferentiatio
n

• This ability to differentiate into multiple cell
  types is called plasticity or transdifferentiation
  .

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Differentiation 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

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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.

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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.

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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.

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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.

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Embryonic Stem Cells (ESC).
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Embryonic 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

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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.

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Properties 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).

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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.

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Cell 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.

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Stem 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.

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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 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.

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Strategy for therapeutic cloning and tissue
engineering
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Stem 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,

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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.

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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.

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Sources 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.

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Sources 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
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  differentiation in vitro', Nature Biotechnology,
  vol. 18, pp. 399404, 01 April 2000.

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Thank you