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Embryonic Stem Cells and Therapeutic Cloning

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Title: Embryonic Stem Cells and Therapeutic Cloning


1
Embryonic Stem Cells and Therapeutic Cloning
2
Review Embryonic Development from the
Reproductive Cloning PPThe next few slides are
pictures to remind you of the various stages of
embryonic development
3
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4
A fertilized egg
Notice the nuclei from the egg and sperm fusing
5
4 day old embryos
6
5 day old embryo at the blastocyst stage
7
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8
So what happens from here?
  • In the adult, most cells are specialized for
    specialized tasks
  • Red blood cells carry oxygen
  • Neurons transmit electrical signals
  • Pancreatic cells secrete insulin
  • Cells of the embryo will then need to commit to
    a particular fate (decide which specialized cell
    type they will become).
  • This process is called differentiation
  • (Remember our cells only do this once! Once a
    brain cell has decided to become a brain cell, it
    can not change its mind and differentiate into
    a muscle cell. That is good for us and our
    brains!)

9
During development, most cells of the body
differentiate.
These books represent different chromosomes in
all your somatic cells. The stories within are
the genes. The words are the genetic code.
You may never read some stories. You may read
some stories only once. You might read other
stories over and over.
All the cells in your body contain the same exact
DNA. How your cells pick and choose the genes
that will be expressed or turned on via
transcription and translation is what makes cells
different.
10
So, what do stem cells have to do with all this?
  • Embryonic stem cells (ESC) are cells that have
    yet to differentiate
  • Derived from the inner cell mass of the
    blastocyst stage of the embryo

11
Embryonic Stem Cells can be cultured in different
laboratory environments to develop into a
specific cell type.
Liver cells
Nerve Cells
Culturedembryonicstem cells (developing an ESC
line)
Muscle Cells
Different types ofdifferentiated cells
Different cultureconditions
12
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13
Watch the
Stem Cell Animation
http//www.stemcellresearchfoundation.org/WhatsNew
/EmbryonicStemCells.htm
14
Medical Applications
15
Medical Applications
  • Repair a damaged tissue or group of cells that
    can't heal itself.
  • This might be accomplished by transplanting ESCs
    into the damaged area and directing them to grow
    new, healthy tissue.
  • It may also be possible to coax stem cells
    already in the body to work overtime and produce
    new tissue.
  • Tissue/Organ growth and transplants?

16
Medical Applications
  • Many of these therapies are still in the infant
    stages and we dont know what other challenges
    will be faced as this technology progresses.
  • For example How long will a stem cell therapy
    last? Will these cells behave themselves (act
    at the intended cell type and also not form
    tumors)?

17
What sort of diseases or disorders could stem
cell therapies be utilized for?just a brief list
  • Parkinsons Disease
  • Alzheimer's
  • Muscular Dystrophy
  • Paralysis
  • Diabetes
  • Genetic Disorders

18
Where would researchers get the embryos that are
the source of embryonic stem cells?
19
  • Fertility clinics
  • A couple undergoing fertility treatments using in
    vitro fertilization generally will produce many
    more embryos than needed to bring about a
    pregnancy
  • With a couples consent, embryos that would have
    been discarded as medical waste are utilized for
    research
  • See the next page about a recent study (June
    2007) that says many couples would donate their
    unused embryos for this research
  • Therapeutic cloning (SCNT) we will talk about
    this later.

20
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21
What is in Vitro Fertilization (IVF)?
  • IVF is the process of fertilization by manually
    combining an egg and sperm in a laboratory
    setting
  • There are a variety of ways this can be done

22
In vitro fertilizationSome procedures involved
with IVF manually inject the sperm into the egg,
and others simply allow fertilization to occur by
adding the sperm to the egg in the lab setting.

23
Why use IVF as a source of stem cells?
  • According to a survey conducted in 2003, there
    are approximately 400,000 unwanted pre-embryos in
    the United States. (Source Hoffman, D.I., et al.
    2003. Cryopreserved embryos in the United States
    and their availability for research. Fertility
    and Sterility 79 1063-1069.)
  • These may no longer be needed for fertility
    purposes and remain frozen or could be destroyed

24
Other types of stem cells and current stem cell
therapies
  • Adult Stem cells These stem cells (can give
    rise to a small number of different cell types)
    but are already "committed" to differentiating
    along a particular cellular development pathway
    (for example, the stem cells we all have in our
    bone marrow that can differentiate only into
    various types of blood cells). Current therapies
    utilize them from the bone marrow.
  • Umbilical Cord Blood (Core Blood) Stem cells
    similar to adult stem cells above but collected
    from the umbilical cord of a newborn.

25
Adult Stem Cells
You can also find these same type of stem cells
in the blood system Peripheral Blood Stem
Cells (PBSCs) Used to treat leukemia, other
cancers and various blood disorders Less
invasive than collecting bone marrow, but are
sparse!
The bone marrow is the spongy core found in the
bones and is a source of adult stem cells.
These stem cells are the precursor cells
responsible for the formation of the blood cells
(red blood cells, platelets, and white blood
cells).
26
Umbilical Cord Blood Stem Cells
Multipotent stem cell rich blood found in the
umbilical cord has proven useful in treating the
same types of health problems as those treated
using bone marrow stem cells
In 2005, there were more than 1,400 cord blood
transplantations in adults, according to NETCORD,
an international network that coordinates
umbilical cord blood banks
The process to collect and store a childs cord
blood doesnt come cheap. The company Cord
Blood Registry, for example, charges and
initial fee of 1975 and then it is 125 per
year for storage.
Why would a parent consider this blood collection
and why might it be considered to have advantages
over bone marrow stem cells?
27
Differences between embryonic stem cells and
adult stem cells -ESC can differentiate into any
cell type (totipotent/pluripotent) while adult SC
have already committed to a particular fate
(multipotent).
Some Challenges in Research -Adult stem cells
are often present in only minute quantities and
can therefore be difficult to isolate and purify.
-There is also evidence that they may not have
the same capacity to multiply as embryonic stem
cells do. -They do not have the development
potential that a ESC -Finally, adult stem cells
may contain more DNA abnormalitiescaused by
sunlight, toxins, and errors in making more DNA
copies during the course of a lifetime. -These
potential weaknesses might limit the usefulness
of adult stem cells.
28
Still so many questions about adult stem cells
  • How many kinds of adult stem cells exist, and in
    which tissues do they exist?
  • What are the sources of adult stem cells in the
    body? Are they "leftover" embryonic stem cells,
    or do they arise in some other way?
  • Why do they remain in an undifferentiated state
    when all the cells around them have
    differentiated?
  • Is it possible to manipulate adult stem cells to
    enhance their proliferation so that sufficient
    tissue for transplants can be produced?
  • Does a single type of stem cell existpossibly in
    the bone marrow or circulating in the bloodthat
    can generate the cells of any organ or tissue (a
    totipotent adult stem cell)?
  • What are the factors that stimulate stem cells to
    relocate to sites of injury or damage
  • Well talk about some new developments in adult
    stem cells later on

29
Therapeutic Cloning or Nuclear Transplantation
(SCNT Somatic Cell Nuclear Transfer)Stem
Cells
30
SCNT and Stem Cells
Notice that UNLIKE reproductive cloning, all
we are doing here is cloning embryonic cells
and then coercing them to differentiate into
specific cells the patient needs.
31
SCNT Process (1)
  • Remove the nucleus from an unfertilized egg cell
    (A).
  • (Because the egg cell is only 100 micrometers,
    or one-tenth of a millimeter wide, this is done
    under a microscope.)
  • Use a suction pipette (B) to hold the egg cell
    steady and a glass needle (C) to remove the
    cells nucleus.

http//www.pbs.org/wgbh/nova/sciencenow/3209/04-cl
on-nf.html
32
SCNT Process (2)
  • Gently push the glass needle through the tough
    shell that surrounds the egg cell.

Here, the glass needle is in the process of
removing the nucleus from within the egg. If you
look closely at the tip of the needle, you can
just make out the genetic material being drawn
out.
33
SCNT process (3)
  • The egg cells nucleus (A) has been released
    outside of the egg. This nuclear material will no
    longer be needed.
  • What remains is an enucleated egg (B). The
    nucleus, with the important genetic information,
    no longer remains but the enucleated egg still
    have certain molecules and other important
    factors that will ultimately help to establish
    embryonic stem cells.

34
SCNT process (4)
Inject the nucleus (at arrow) from a donor cell
into the enucleated egg cell.
(Such a donor cell might be a skin cell from a
disease sufferer whom doctors hope to treat using
the patients own stem cells grown in culture)
Ease the tip of the glass needle deep into the
enucleated egg cell. Then, deposit the donor
nucleus.
35
SCNT process (5)
  • After completing the nuclear transfer, the
    unfertilized egg cell is activated using a
    chemical or electrical treatment that stimulates
    cellular division.
  • The first division results in two cells (left
    image), the next makes four cells, and so on.
    This structure is now termed an embryo.

Now, at this point, if this was a sheep embryo
and we implanted it into a surrogate ewewhat
would we get?
36
SCNT process (6)
  • The proliferating cells form a structure called a
    blastocyst within days. It is roughly the same
    size as the egg cell.

The right-hand image shows the blastocyst
hatching
37
An embryonic stem cell line has now been
synthesized, the cells have the same DNA as the
donor. These cells can be customized they can
be made into any cell/tissue/organ of the body
and transplanted (in theory) to the donor without
immune rejection.
(The cells may have their genes corrected
before being transplanted to an individual.)
38
Therapeutic cloning (SCNT) Could the technique
fix a gene (alternative to gene therapy)?
  • Theoretically a person with a gene defect can
    have a transplant of new cells/tissue/organ that
    are customized for them (no immune rejection
    because the transplanted cells are their own
    cells) EXCEPT a good copy of the gene they are
    defective in has been inserted

39
First things firstCan we make ESCs into the
cells of specific organs?
  • Scientists at Imperial College London reported in
    2005 that they successfully coaxed embryonic stem
    cells to change into specialized lung cells.
    Researchers describe their study in the journal
    Tissue Engineering.
  • "Although it will be some years before we are
    able to build actual human lungs for
    transplantation, this is a major step towards
    deriving cells that could be used to repair
    damaged lungs," the study's lead author, Anne
    Bishop, said in a press statement.
  • Interesting and exciting, but again, still in
    infant stages

40
How big of a role does the media play in our
impressions on stem cell research?
  • Hint The answer is that the media plays a HUGE
    role!

41
The Media had a field day reporting onHwang
Woo-Suk
Hwang Woo-Suk was a professor and prominent
researcher in the College of Veterinary Medicine
at Seoul National University. In February 2004,
Hwang and his team announced that they had
successfully created embryonic stem cells with
the somatic cell nuclear transfer method, and
published their paper in Science (one of the most
prestigious scientific journals there is) in
March 2004. A second paper, published in May
2005, reported the creation of 11 stem cell lines
that genetically matched nine patients with
spinal cord injury, diabetes, and an immune
system disorder.
42
  • This, the first breakthrough of its kind, renewed
    hopes that such stem cells could someday lead to
    insights into many hereditary conditions as well
    as the creation of replacement tissues
    genetically matched to patients and treat
    degenerative diseases.
  • Hwang Woo-Suk even made TIME Magazines list of
    People Who Mattered 2004.
  • Those hopes, however, began to unravel in June
    2005, when someone sent a message to the "tip off
    " mailbox on the Web site of a long-running
    investigative TV news program in Seoul.
  • The writer said his conscience had been bothering
    him over problems he knew of with Hwang's
    research..

43
  • Reporters interviewed co-authors of the 2005
    paper and found that the majority had never
    actually seen the cloned embryonic stem cells.
  • The university in Seoul investigated and
    concluded that the data reported in both the 2004
    and 2005 Science papers was fabricated.
  • Science magazine retracted the papers.
  • Hwang Woo-Suk was accused of "research
    misbehavior and was dismissed from his position
    in 2006.

44
What did he really do, and what was fabricated?
  • Hwang did not have any proof to show that cloned
    embryonic stem cells were ever created, the
    panel said in a report, disputing the central
    claim in Hwangs 2004 paper in the journal
    Science.
  • In the paper, Hwang said he had cloned a human
    embryo and extracted stem cells from it. But the
    university cast doubt on whether an embryo was
    cloned, saying there is a high possibility it
    could have merely been a mutated egg, which could
    appear to have similar qualities of an embryo.
  • The 2004 paper was written on fabricated data to
    show that the stem cells match the DNA of the
    provider although they didnt, the report said.
  • The panel upheld Hwangs claims last year to have
    created the worlds first cloned dog, an Afghan
    hound named Snuppy. The journal Nature (another
    very prestigious scientific journal), which
    published Hwangs cloned-dog article, said
    results from its independent tests also showed
    Snuppy was indeed a clone. (This accomplishment
    not as noteworthy because many other animals have
    been closed previously).

45
What was the effect of this on our society?
  • Some say the reputation of science and stem cell
    research suffered, other arent so bleak.
  • AAAS Stem Cell Experts Assess the Impact of
    Hwang Fraud on Research, Public Trust

46
ESCs and Politics
  • Bush placed a federal ban on using federal
    funding to make any new human ES cell lines.
    (Only those lines made before 2001 can be used.)
  • California and New Jersey have facilities that
    use state and private funds.
  • Other states that can use state funds (with
    limits) Connecticut, Illinois, Indiana, and
    Maryland

47
July 2006 Stem Cell Research Enhancement Act
Passed by the Senate
  • The bill expands the number of stem cell lines
    that are eligible for federally funded research. 
    Currently, federal policy on human embryonic stem
    cell research permits only the use of stem cell
    lines derived before August 9, 2001 for federally
    funded research.
  • The Stem Cell Research Enhancement Act lifts that
    restriction. Stem cell lines shall be eligible
    for federally funded research regardless of the
    date on which they were derived.

48
July 2006 Stem Cell Research Enhancement Act
Passed by the Senate
VETO!!! By President Bush July 19, 2006
  • The bill expands the number of stem cell lines
    that are eligible for federally funded research. 
    Currently, federal policy on human embryonic stem
    cell research permits only the use of stem cell
    lines derived before August 9, 2001 for federally
    funded research.
  • The Stem Cell Research Enhancement Act lifts that
    restriction. Stem cell lines shall be eligible
    for federally funded research regardless of the
    date on which they were derived.

49
  • This veto was in 2006 and another one followed in
    June, 2007
  • See the next two CNN headlines to follow on the
    veto

50
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51
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52
You might be thinking
  • Whats the problem with using existing stem cell
    lines?
  • Those against stem cell research say
  • Still destroying an embryo for profit
  • Scientists say
  • Too little genetic diversity
  • Some cell lines contaminated
  • The existing cell lines have been grown with
    mouse feeder cells and therefore Under Food and
    Drug Administration rules, such transplants with
    existing cells would be classified as
    "xenotransplants," or transplants of animal
    tissue. These would be subject to strict
    requirements on both researchers and patients
  • Why not just use Adult Stem Cells?
  • The potential is not present in these type of
    cells than what is available in a totipotent or
    pluripotent cell like and ESC. We are still
    learning quite a bit about adult stem cells and
    their potentials. (See back to Adult Stem Cells)
  • Whats the big deal about not approving federal
    funds for stem cell research?
  • See next several slides.

53
Why Does Federal Funding Matter?
  • Regardless of the veto, stem cell research will
    continue, but federal funding would dramatically
    change the scope of this research and widen the
    circle of scientists involved.
  • This type of research requires big time and
    mostly large government organizations (such as
    the NIH) can provide that support.
  • According to the Presidents Council on
    Bioethics, While there are currently no
    federally legislated constraints on the use of
    private funds for this research, there is a
    consensus opinion in the scientific community
    that without NIH support for newly created ESC
    lines progress in this important realm of
    research will be severely constrained.
  • Federal regulations would be able to be enacted
    with rules for oversight.

54
Federal Funding(from TIME Magazine, The Stem
Cell Debate)
  • If President Bush Says...
  • YesThe floodgates would open. Right now most
    scientists steer clear of stem-cell research
    because they have to if any part of their lab
    receives federal money (and most do), they can't
    touch this research. If that changes, hundreds of
    labs across the country, including medical
    powerhouses like those at Harvard and M.I.T.,
    would probably begin work on stem cells.
    Scientists would be able to share findings freely
    and review one another's conclusions. The
    government could choose to regulate how embryos
    are cultivated, handled and ultimately destroyed.
    Treatments would probably come sooner. (Of
    course, there are no guarantees!)
  • NoResearch would proceed but only in the handful
    of labs willing to fund it on their own. These
    labs are subject to minimal oversight. They
    rarely consult with one another, research doesn't
    get peer-reviewed, and studies may be unknowingly
    (and unnecessarily) duplicated. Many of the
    nation's top scientists who would otherwise lead
    the research effort would remain on the
    sidelines. And commercial pressures could make
    private labs focus more on research that might
    turn a profit than on studies that advance
    general knowledge. Says James Thomson, the
    stem-cell pioneer "Industry and other countries
    will go forward. The field will progress without
    federal funding, but very, very slowly."

55
If that political debate isnt confusing
enoughlets throw stem cell research via SCNT
in!(from the AAAS, American Association for the
Advancement of Science)
  • Arguments Against Nuclear Transplantation
    Research
  • Proponents of a comprehensive ban on nuclear
    transplantation for research and reproductive
    purposes raise two main arguments. Religious
    conservatives argue that human embryos should be
    afforded a moral status similar to human beings
    and should not be destroyed, even in the course
    of conducting research. They also argue that
    permitting nuclear transplantation would open the
    door to reproductive cloning, because a ban only
    on implantation would be difficult to enforce. In
    this second argument, conservatives are joined by
    a coalition of environmental, women's health, and
    bioethics groups who are not unalterably opposed
    to nuclear transplantation, but believe that it
    should not be permitted until strict regulations
    are in place.
  • Arguments For Nuclear Transplantation Research
  • Proponents of a ban solely on reproductive
    cloning that would permit nuclear transplantation
    research, include a coalition of science
    organizations, patient groups, and the
    biotechnology industry. These groups argue that
    the moral status of a human embryo is less than
    that of a full human being, and must be weighed
    against the potential cures that could be
    produced by research using nuclear
    transplantation. They contend that a ban on
    implantation on the product of nuclear
    transplantation would be no more difficult to
    enforce than a ban on nuclear transplantation
    itself. They argue further that criminalizing
    scientific research, which has been done only
    very rarely in the past, would set a bad
    precedent.

56
  • Listen or read to find out more at
  • http//www.pbs.org/newshour/bb/health/jan-june07/s
    temcell_06-07.html

57
  • Materials for this presentation were provided by
  • Dr. Kelly Hogan, UNC
  • Meredith Norris, UNCC
  • Jennifer Warner, UNCC
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