Cloning - Download as PowerPoint

							CLONING




          Anne Simpson, Jan ‘03
“Who can quantify the indescribable source of emotion
   pleasurable and otherwise that children engender in
  their biological and social parents? It is this above all
 else which drives individuals to take extreme measures
    to achieve or avoid parenting in the modern world.”

Infertility in the Modern World; Present and Future Prospects, GR Bentley
“Why should another child die from leukemia
when if the technology is allowed we should be
     able to cure it in a few years time?”

     Simon Smith, The Human Cloning Foundation
Background

   First reproductive cloning in 1952 in Amphibia.

   First mammal cloned in 1996 in Edinburgh -
    Dolly the sheep.

    Sheep, cattle (1998), mice (1998), goats
    (1999) and pigs (2000) have all been cloned.
What is cloning?

   Embryo Splitting or “Cloning”
   Somatic Cell Nuclear Transfer (SCNT)
   Reproductive Cloning
   Therapeutic Cloning
Embryo splitting or “cloning”

   Separation of human embryo into 2 parts.
   Cells removed from fertilised ovum - have the
    potential to develop into a blastocyte
   If implanted can develop into a child.
   Genetically identical monozygotic twins
   The embryo can be spilt only a limited number
    of times, and a “clone’ is not produced.
Somatic Cell Nuclear Transfer
   Nuclear material removed from donor egg
   DNA inserted into the enucleated egg
   Reconstituted zygote formed, equivalent to a fertilised
    ovum.
   Potential to divide into a blastocyte
   If implanted, develops into child genetically identical to
    the nuclear donor - Reproductive cloning.
   In reproductive cloning the clone would be the identical
    twin of the donor
Schematic representation of
Somatic Cell Nuclear Transfer
Therapeutic cloning

   SCNT
   Blastocyte (embryo) cultured to produce an
    embryonic stem cell line
   Excludes most blastocyte cells, effectively
    destroying the embryo
   Undifferentiated embryonic stem (ES) cells can
    then be made to differentiate into precursor
    cells.
Stem Cells

   A stem cell is defined as:
       A cell that can proliferate indefinitely and
       differentiate into a wide variety of cell types
   Adult stem cells are found in bone marrow,
    isolated and encouraged to proliferate
   Nuclear reprogramming – obtain ES cells by
    directly dedifferentiating normal body cells in
    vitro
 “Few issues linked to genetic research have
raised as much controversial debate as the use
   of somatic cell nuclear transfer technology
(SCNT) to create embryos specifically for stem
                  cell research”

The Pros and Cons of Human Therapeutic Cloning in the Public
Debate, Journal of Biotechnology, Sep 2002
Benefits of Therapeutic Cloning

   Therapeutic cloning has the potential
    significantly to reduce human suffering and
    enhance human happiness.
   In it may lie the potential to overcome tissue
    rejection and the opportunity to increase
    understanding of cellular development
Ways in which cloning may be
expected to benefit mankind:

   Use of embryonic stem cells to treat degenerative and
    autoimmune conditions such as Alzheimer’s Disease,
    Parkinson’s Disease, diabetes, heart failure, arthritis
    etc. and to treat burns victims and spinal cord injuries.
   Infertility treatment
   Plastic, reconstructive and cosmetic surgery
   Leukaemia and other cancers
   Transplants – Kidney and liver
The Scientific and Ethical Debate

   Therapeutic cloning involves deliberate production of
    cloned human embryos so that through their
    destruction patients may receive treatment.

   Majority of scientific opinion opposed to the
    reproductive cloning of humans in view of the
    developmental, morphological and physiological
    problems observed in mammals that have been cloned
Ethical Questions
   Two questionable procedures –
        cloning of humans
        destruction of human embryos


   Main ethical arguments against therapeutic cloning
    centre on the moral status of the human embryo

   Most ethical questions concerning status of the human
    embryo been examined in the context of abortion
    Reproductive cloning-
    Low efficiency

   Low efficiency of reconstituted eggs developing
    to parturition.
    1 cloned animal to parturition, approx. 100
    eggs must be enucleated and reconstituted
    i.e. only 1% efficient

   Weak argument when considered that IVF
    requires harvesting of up to 40 eggs
Reproductive cloning -
Abnormalities risk

   Developmental abnormalities - large offspring
    syndrome – oversized offspring with
    disproportionately sized organs, respiratory
    and circulatory problems,
    May not be a risk in humans

   Incidence of congenital abnormalities in
    animals is as high as 35%.
    Developmental abnormality following natural
    sexual reproduction is 3%
Reproductive Cloning - Genetic
Engineering

   Cloning makes it easier to meddle with genes,
    another form of genetic engineering
   Risk of incompletely reprogrammed genes,
    could be minimised by the optimum culture
    conditions used in IVF.
Therapeutic Cloning –
Adult stem cells
   Many benefits of embryonic stem cells can be
    achieved using adult stem cells.
   Adult stem cells are demonstrating greater
    multipotency than expected
   Adult stem cells hard to isolate and have restricted
    proliferation potential.
    Range of cells they can be differentiated into is limited
   Risks of using blood stem cells from a cancer patient’s
    own bone marrow to restore their immune system –
    some might be cancerous
Therapeutic Cloning

   Cloned cells may be more vigorous and
    therefore at greater risk of becoming
    cancerous
   Studies using cloned blood stem cells in cows
    came from 100-day old fetuses
Embryo status

   Are embryos already human beings?
   Society still divided over how to regard the
    moral rights of and its duties towards the
    human embryo.
   Are human embryos entitled to protection from
    intentional destruction.
Ethical Dilemma

   Relief of suffering is not a sufficient argument
    to justify the means.
   Abortion legislation in most countries suggests
    the rights and choice of grown adults
    supercede the rights of the early embryo
“If the position were taken that embryos are not persons
  and may be destroyed, and that position turns out to be
  wrong, we will have endorsed the killing of thousands if
      not millions of human beings. If human embryos
    however are not persons, but we treat them as is they
  were the potential harm is that therapies might become
                    available more slowly.”

  What to call Human Cloning O’Mathuna, European Molecular Biology
                              Organisation
Middle Ground

   Bioethicists recommend aggressively pursuing
    adult stem cell research while upholding the
    highest ethical standards for medical research
Current International Regulations

   US expected to ban reproductive cloning,
    still debating whether to allow therapeutic cloning
   Australia recently passed bill allowing harvesting of
    stem cells from surplus IVF embryos.
    Reproductive and therapeutic cloning have been
    banned
Current International Regulations
cont.

   European countries - unanimous prohibition
    reproductive cloning
    No agreement on permission for research into
    therapeutic cloning.
   UK took the lead and voted in favour of regulations
    allowing therapeutic cloning
    UK law allows researchers to harvest stem cells from
    surplus IVF embryos and conduct therapeutic cloning
Human Fertilisation and
Embryology Act 1990

   “…to make provision in connection with human
       embryos; to prohibit certain practices in
      connection with embryos and gametes; to
         establish a Human Fertilisation and
              Embryology Authority…”
Human Fertilisation and
Embryology Authority

 “A statutory body which regulates licenses and
  collects data on fertility treatments such as IVF
    and donor insemination as well as human
            embryo research in the UK”.

 Set up in 1991
Human Fertilisation and
Embryology Authority

   Ensure high national standards, monitors all
    research, supervises controlled research,
    considers ethical implications in light of the
    national debate
   21 members appointed by UK Health Ministers
    based on personal knowledge and expertise,
    half of whom come from disciplines other than
    medicine or human embryo research
References
   Cloned stem cells may give new lease of life New Scientist
   What to call Human Cloning O’Mathuna, European Molecular Biology
    Organisation
   Reiss MJ, Ethical Dimensions of Therapeutic Human Cloning, Journal of
    Biotechnology, Sep 2002
   The Pros and Cons of Human Therapeutic Cloning in the Public Debate
    Journal of Biotechnology, Sep 2002
   Infertility in the Modern World; Present and Future Prospects, GR
    Bentley
   The Human Cloning Foundation
   www.howstuffworks.com
   Commentary on Human Cloning Byrne & Gurdon, Differentiation 2002
   www.hfea.gov.uk
   www.newscientist.com
INFERTILITY

   Management of Infertility
    Clinical Review 2002, BMJ
    BMJ 2002;325:28-32 (6July)


   The Initial Investigation and Management of
    the Infertile Couple
    RCOG, Evidence Based Clinical Guidelines,1998
    www.rcog.org.uk/guidelines