Animal Cloning
ES cells
Embryonic stem (ES) cells
Pluripotent stem cells derived from the inner cell mass of the blastocyst
Can be cultured, manipulated and then reinjected into blastocysts,
where they can go on to contribute to all parts of embryo.
In principle, ES cells
also
might be able
to generate
large quantities
of any desired cell
for transplantation
into patients.
Human embryonic stem cells (hES cells)
• hES cells represent the earliest stage of cells in human
development.
• hES cells may differentiate into any one of the 230
different cells in human body.
• hES cells may treat many human diseases.
hES cell development stages
Fertilized egg
Blastocyst (囊胚)
hES cells
Ectoderm
Mesoderm
Endoderm
Skin, Neural cells, etc.
Bone, Muscle,
Blood cells, etc.
Digestive organs,
Lung, etc.
治疗多种疾病
Treat many
diseases
人的胚胎干细胞
Human
Embryonic
Cells
hES may
differentiate
into any
human cells.
胚状体细胞
Embryoid
Bodies
Dopamine 神经原
Dopamine neurons
震颤性麻痹
Parkingson’s disease
树状神经原
Oligodendrocytes
脊髓损伤
Spinal cord injury
心肌细胞
Cardiomyocytes
心脏病
Heart disease
胰岛细胞
Islet beta cells
糖尿病
Diabetes
肝脏细胞
Hepatocytes
肝脏疾病
Liver diseases
成骨细胞
Osteoblasts
骨质疏松症
Osteoporosis
软骨细胞
Chondrocytes
骨关节炎
Osteoarthritis
其他细胞
Other cells
其他疾病
Other Diseases
Mouse embryonic stem cell
cultures
- LIF
LIF (leukaemia inhibitory factor)
maintains embryonic stem cells
in an undifferentiated state
ES cells spontaneously differentiate
when allowed to aggregate
in the absence of LIF
Human stem cell lines available
(August 28, 2001)
http://www.the-funneled-web.com/images/Embryonic%20stem%20cells.gif
Totipotent and
pluripotent cells
isolated directly
from the inner cell mass
of embryos
at the blastocyst stage.
Totipotent =
meaning that
its potential is total.
(IVF-IT surplus embryos
in case of humans)
pluripotent =
they can give rise
to many types of cells
but not all types of cells
(no fetus developed).
www.laskerfoundation.org/ news/weis/estemcell.html
Adult stem cells multipotent
but not totipotent
More about stem cells
Embryonic stem cells
Truly pluripotential
several countries
have sanctioned deriving
human ES-cell lines
from ‘surplus’ embryos
created through
in vitro fertilization
Adult stem cells
More restricted
pattern of differentiation
medical gain without ethical pain
Nuclear Transplantation
Nucleus comes from someone to be cloned
1. Enucleation of the cell
2. Nuclear transfer
removal of the nucleus
chromosomes are gently sucked out
with a sharp micropipette
A. electrofusion
whole donor cell
From the a mature unfertilized oocyte
(egg)
injected beneath the zona pellucida
Or from the cell in quiescent state
(inactive G0 phase of cell cycle) OR
metaphase II
and fusion of cells
(the outer membrane of the oocyte)
induced by electrical impulses
B. nuclear injection
oocyte
ENUCLEA
TION
cytoplast
naked nucleus
microinjected into cytoplast
http://www.brinkmann.com/pdf/cell_fusion.pdf
Electrofusion
fusion pulse
Cells brought close
together
Heterokaryon phase:
nuclei distinct
Fusion induced by electric pulse
fusion product
Genetic Reprogramming
If cell for cloning taken from adult organism
“de-differentiation” – rearranging the genome of the nucleus
to restore its totipotency so it can differentiate into different
types of cells and develop into a whole organism
must occur after nuclear transfer to successfully produce the
clone – required for the nuclei from adult cells to develop
normally
best completed in unfertilized oocytes (as plasma donors)
Re-programming never achieved
with same success as fertilization
Fig. 5 from Nature Reviews Genetics 3: 671
Development of the embryos from
cell with “alien” nucleus
May be induced by chemical treatments
Developing embryos are grown in a
culture to assess their viability
Implantation of Embryo
embryos are surgically transferred into the uteri of
suitable surrogate mothers
many embryos are transferred to each surrogate
mothers to ensure implantation
Therapeutic Cloning
Why human Therateutic cloning is unethical in USA?
1. Therapeutic cloning can only be justified by the utilitarian
calculus that values potential medical treatments over the
lives of the embryos who would be destroyed in order for the
research to proceed. However it is not ethical to sacrifice one
human life for the real or potential benefit of others.
2. It is unethical to view a human being - regardless of its
age-as a means to an end. Creation of human embryos
specifically for destructive research is opposed by our
community, and this is what is involved in therapeutic cloning.
3. Therapeutic cloning will undoubtedly lead to exploitation of women.
In order to create human clones for stem cell therapy, an enormous
number of women's eggs will need to be donated. To do so, women
may be treated with superovulatory drugs and must undergo an
invasive procedure. Complications may occur. Advanced cell
technology paid up to $4,000 to each woman who donated eggs for
their cloning experiments. It is likely that women of lower economic
status will be exploited in this way.
4. In addition to the ethical concerns above, therapeutic cloning should
be banned because it increases the likelihood of reproductive cloning.
Preventing the implanting and subsequent birth of cloned embryos
once they are available in the laboratory will be impossible. Already Dr
Severino Antinori of Italy has plans to produce the first cloned human.
The most effective way to prevent reproductive cloning is to stop the
process at the beginning, with the creation of cloned embryos. Since
the overwhelming community consensus is that reproductive cloning
should be banned, steps must be taken to ban therapeutic cloning as
well.
5. Embryonic stem cell research and therapeutic cloning should also be
banned in view of the existence of other promising and ethical
treatment options such as adult stem cell therapy (which has already
been successfully used in patients).
6. In conclusion, if destruction of excess embryos is allowed, does this
just apply to the embryos currently in storage, or to future 'excess'
embryos as well? The blatant irresponsibility of IVF clinics that have
allowed the accumulation of approximately 70,000 embryos to date will
have no incentive to change if future excess embryos are also fodder
for the laboratory.
Mammal Cloning Timeline
1984 – A live lamb was cloned from sheep
embryo cells
Megan and Morag
1986 – Early embryo cells were used to clone
a cow
1993 – Calves were produced by transfer of
nuclei from cultured embryonic cells
1995 – Two sheep, named Megan & Morag,
were cloned using embryo cells
Dolly
1996 – Birth of Dolly, the first organism to be
cloned from a fully differentiated adult cell
1997 – Transgenic sheep named Polly was
cloned containing a human gene
http://www.cnn.com/2001
/WORLD/europe/08/06/clo
ne.critics/index.html
Tetra
1998 – 50 mice were cloned in three
generations from a single mouse
1998 – 8 calves were cloned from a single
adult cow, but only 4 survived to their first
birthday
1999 – A female rhesus monkey named Tetra
was cloned by splitting early embryo cells.
2000 – Pigs and goats reported cloned from
adult cells
2002 – Rabbits and a kitten reported cloned
from adult cells
http://hs.houstonisd.org/
hspva/academic/Science/
Thinkquest/gail/text/bene
fits.html
Dolly with her surrogate mother
Dolly
• Born in July 1996 at the Roslin
Institute in Scotland
Dolly with her first
newborn, Bonnie
• First mammal to be cloned
from an adult mammal using the
nuclear transfer technique
• 277 attempts were made
before the experiment was
successful
•Dolly died in February 14, 2003
of progressive lung disease at
the age of 6; whereas normal
sheep can live up to 12 years of
age.
Mammal Cloning allows propagation of
endangered species
http://www.howst
uffworks.com/cloni
ng.htm/printable
January 8, 2001 Noah, a baby bull gaur, became the first
clone of an endangered animal.
Comparison of Cloning Success
Rates in Various Animals
Species
Number of
oocytes used
Number of
live offspring
Notes
Mouse
2468
31 (1.3%)
-
Bovine
440
6 (1.4%)
2 died
Sheep
417
14 (3.4%)
11 died
within 6
months
Pig
977
5 (0.5%)
-
Goat
285
3 (1.1%)
-
The table shows success rates of cloning when mature mammal cells were
used.
Yanagimachi, R. 2002. "Cloning: experience from the mouse and other animals." Molecular and Cellular Endocrinology. 21 March,
187.
Development and survival of cloned mouse
embryos
Majority of the embryos die before and after implantation. This figure shows
that the present cloning technique is highly inefficient.
Yanagimachi, R. 2002. "Cloning: experience from the mouse and other animals." Molecular and Cellular Endocrinology. 21 March,
187.
Clone Birth Defects
• Cloned offspring often suffer from large offspring syndrome,
where the clone and the placenta that nourished it are
unusually large.
• Cloned offspring often have serious inexplicable respiratory
or circulatory problems, which causes them to die soon after
birth.
• Clones tend to have weakened immune systems and
sometimes suffer from total immune system failure.
• Very few clones actually survive to adulthood.
Clones appear to age faster than normal.
Clones experience problems associated with old age, such as arthritis, while
they are still young.
This may be due to the fact that clones have shorter telomeres
The whole story about cloning is
not a reproductive story
The possibility of using cloning technology
to grow organs genetically identical
to our own for transplantation –
thereby avoiding rejection of foreign issues
http://medlib.med.utah.edu/We
bPath/CVHTML/CV001.html
http://easyweb.easynet.co.uk/~sfl/rlb3a.jpg