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Stem Cells and Animal Cloning
5. Stem Cell
Research
1. Human Genome
Project
2. Genetic
Testing
6. Animal Cloning
20-week fetus in
utero.
3. Genetic
Engineering
4. ARTs
Stem cells
are essentially
undifferentiated
cells…
They can become
many different
kinds of cells
A stem cell must be able to
do the following:
1. Produce
specialized
descendants
2. Retain ability to
reproduce
themselves
Two Classes of Stem Cells
A. Totipotent stem
cells
 Give rise to all cell
types
 Embryonic Stem
Cells: derived from
the inner cell mass
of the blastocyst.
 Cannot give rise to
an individual
organism
B. pluripotent stem cells
 Give rise to several
specialized cell types
 Adult Stem cells
 Adult Stem cells are
used by the body to
repair and regenerate
damaged organs and
tissues throughout life.
From
where
stem cells
are
isolated
All adult cells
including adult
stem cells
come
from one of 3
cell lineages:
1. Endoderm
2. Ectoderm
3. Mesoderm
Adult Stem Cells
1. Blood Stem Cells: Hematopoietic cells
are found in the bone marrow and give
rise to all red and white blood cells
2. Mesenchymal Cells: give rise to new
bone, cartilage, and connective tissue
3. Neuronal Stem Cells: nervous system
tissue (mostly produced during
embryonic development)
pluripotent Blood Stem Cell gives
rise to many different cell types
Adult Tissues and Organs Known
To Have Stem Cells
• Brain: can become 3 kinds of nerve cells and
even some blood cells
• Skin: replace all types of skin cells
• Bone Marrow: Blood, bone and cartilage
• Endothelium: Blood vessels and cardiomyocytes
• Skeletal Muscle: muscle growth
• Digestive System: Epithelial lining of the gut
• Pancreas: pancreatic β cells
• Liver: stem cells from bone marrow may repair
the liver
The Promise of Adult Stem Cells
•
1.
2.
3.
Advantages:
Can be used to cure some diseases
Directed differentiation possible
If isolated from the same patient, no tissue
rejection issues
4. No ethical issues
• Disadvantages:
1. Limited use
2. Currently difficult to isolate (except for bone
marrow)
Growing Body Parts From Cell
Cultures
• Biojewellry: Wedding rings grown from
each others bones!
• http://www.biojewelry.co.uk
Bone cell culture from a cow, inlaid with silver
In contrast, embryonic stem (ES)
cells are not limited in their potential
to become every cell type.
It is the versatility of these cells that
gives them the potential to have more
therapeutic applications than
adult stem cells
Stem Cells
• Embryonic stem cells
are the precursors to all
more specialized stem
cells
• They are found in the
inner cell mass of the
blastocyst
• 1998 the first culture of
embryonic stem cells
maintained in the
laboratory
Biology of Embryonic Stem Cells
• Blastocyst is made of the
trophoblast and the
inner cell mass
• There is no way to remove the
ICM without killing the embryo
• Once the ICM is separated
from the trophoblast, the
embryo can no longer
develop into a fetus
• Directed Differentiation
– Requires the trophoblast
– Otherwise, the ICM is like a child
who has lost its way home, with
no map to guide them
– Requires growth factos and
hormones to coax cell in to
becoming specialized tissues
Source of Embryonic Stem Cells
• Obtained from IVF (In Vitro Fertilization)
clinics
• Ethical issues
– Is it ever OK to use human embryos?
– When is it OK to use human embryos?
– What is done with all the frozen embryos
not used for implantation?
Cardiomyocyte differentiated from human
embryonic stem cells.
Stem Cell Therapy
• Most stem cell therapies are in the research stage with
mice and rats
• Treatments for humans would include:
• Leukemia (using patients bone marrow)
• Diabetes: a “cure” vs treatment (using patients adult stem cells to
create a population of cells that produce insulin)
• Cardiovascular disease: injecting stem cells into the
patient
• Neurological disorders:
–
–
–
–
–
Alzheimers
Tay-Sachs
Huntington’s Chorea
Spinal Chord injuries
Parkinsons
• Organ Factories?
• The problem of immune rejection depends on the
source of the stem cells
• Adult Stem Cell therapy:
– Not easy to isolate
– Unknowns in regard to repair of neural tissue
• Memory retention
• Psychology
• Umbilical Chord Stem Cells (UCS):
– Can replace bone marrow transplants
– Successfully used to treat leukemia in humans
• Growth Factors: might also cause cancers
• Wandering Stem Cells: Will stem cells always go
where they are intended?
• Stem Cell Cancer Induction Reality Check
Animal Cloning:
Species that have been cloned
•
•
•
•
•
•
Cattle
Goats
Pigs
Cat (CC the Copy Cat)
Sheep (Dolly)
Deer (Dewey)
Methods used to clone animals
Nuclear transfer
(SCNT)
Somatic Cell Nuclear Transfer
(SCNT)
• First done in 1951 with frogs
• The mystery of development and differentiation
from a single endowment of DNA
• The principle of Nuclear equivalence
– Nuclei of all cells are genetically identical
– But, different cells express different subsets of
genes
• Somatic cells
• Germ line cells
– Totipotency
• Capability of cells to direct development of entire organism
– Can pre-programmed chromosomes be used for
cloning whole organisms?
Somatic Cell Nuclear Transfer SCNT
• uses unfertilized eggs
• nucleus is removed
from the egg
• nucleus from a donor
cell is injected
Empty Egg Seeks
Nucleus for LTR
• Source of Nucleus is important:
– Embryonic stem cells: unprogrammed;
cloning blindly
– Adult cells: programmed
• know the characteristics
• “shop before you buy”
How Dolly
was made:
What happened
to Dolly?
• The main problems
associated with cloning
animals from adult
cells:
1. cloned lambs with
immature lungs
2. deformed kidneys
3. hearts with
thickened walls and
4. skeletal
abnormalities
Cloning Pets
• Reproductive Cloning: Cloning to produce an
individual
• Genetic Savings and Clone
– gene banking and cloning of exceptional pets
http://www.savingsandclone.com/
• PerPETuate Inc.
– http://www.perpetuate.net/
Reproductive Cloning:
When cloning results in an organism
Gizmo and Little Gizmo
Mango and Peaches
Therapeutic Cloning
Creating tissues and organs for individuals
• Requires a nucleus from YOU and an
enucleated egg cell (SCNT)
• Grow embryonic stem cells that are genetically
identical to the individual. The cells are grown
into tissue for repair of damaged organs
• It would create “perfect-match” tissue. No more
tissue rejection issues.
• Is generating a few cloned embryonic cells for
tissue repair from an adult the same as using a
zygote from invitro fertilization?
Therapeutic Cloning vs.
Reproductive Cloning
• Adult stem cell research (no problem)
• Embryonic stem cell research
– IVF embryos
– Therapeutic cloning
• Reproductive Cloning is relegated to the
cloning of non-human animals
Those opposed to
stem cell research
• Opposed to the use of Embryonic stem
cells
• Research underway to reprogram adult
cells for tissue repair so that they can
be as versatile as ES.