Download Stem Cell

Stem cell: a cell capable of
1) tissue plasticity - make different cell types
2) infinite self renewal through asymmetric division
stem cell
stem cell
skin
muscle
nerve
Properties of STEM cells
Plasticity
Self renewal
STEM CELLS
1. Source
2. Cloning
3. Plasticity
CLASSIC EXAMPLES of
STEM CELLS
• Embryonic stem cells (ESC)
• Bone marrow derived stem cells
Blastocyst
ICM = embryonic stem cells
ICM
•Fluid-filled cavity termed
blastocoele
•
Two regions identifiable
- outer trophoblast
- inner cell mass (ICM)
•
Blastocyst implants in
uterine wall
Trophoblast
Origin of vertebrate stem cells
USES of
EMBRYONIC STEM CELLS
1. Source of different types of human cells
for Transplantation:
for Cell Therapy or Tissue Engineering (organs).
Merit and ethics are controversial
2. Cloning:
3. Somatic nuclear transfer (therapeutic cloning):
USES of
EMBRYONIC STEM CELLS
1. Source of different types of human cells
for transplantation:
for Cell Therapy or Tissue Engineering.
Merit and ethics are controversial
2. Cloning:
to make ‘genetically identical’ new individuals
Achieved for animals – unlikely for humans.
3. Somatic nuclear transfer (therapeutic cloning):
to generate autologous cells for transplantation
Avoids problems of immune rejection of non-self
CLONING
1962 John Gurdon in the UK took (diploid) nucleus from
tissue of adult frog and implanted this into an unfertilised
egg that had the nucleus removed. The special influence
of the maternal cytoplasm caused the ‘differentiated’ adult
nucleus to give rise to a complete new frog
FIRST EXAMPLE OF ADULT CLONING. Shows mature
nucleus has capacity to revert to ‘equivalent’ ESC.
1996 Over 30 years later Dolly the sheep was cloned in
Scotland. Then cattle, pigs, cats pets – humans??
ISSUES
• Ethics (especially for humans)
• Genes vs environment
• Status/quality of ‘aged’ DNA
• Role of maternal cytoplasmic factors and mtDNA
USES of
EMBRYONIC STEM CELLS
1. Source of different types of human cells
for transplantation:
for Cell Therapy or Tissue Engineering.
Merit and ethics are controversial
2. Cloning:
to make ‘genetically identical’ new individuals
Achieved for animals – unlikely for humans.
3. Somatic nuclear transfer (therapeutic cloning):
to generate autologous cells for transplantation
Avoids problems of immune rejection of non-self
ADULT STEM CELLS
Bone marrow derived stem cell
classic source
Haematopoiesis
Stem Cell
(HSC)
ES cells
embryo
EG cells
Somatic Stem cells
adult
Multiple paths to new cell identities
Fluorescent Activated Cell Sorting
(FACS)
to isolate stem cells
based on many cell surface markers Sca1, CD34 etc
Stem cells can be derived from tissues throughout development
ES Cells
Blastocyst
ES cells
Embryo/Fetal
Germ cells
Fetal tissues
Umbilical Cord
Umbilical cord blood (UCB)
Supporting tissues (MSC)
UBC
Post-Natal Tissues
• Bone marrow (HSC)
• Blood vessels (ESC)
• Interstitial connective tissue (MSC)
• Other tissues
STEM CELLS
1. Source
2. Cloning
3.Plasticity
Myogenic Stem Cells
Satellite cell
Terry Partridge
Sources of myoblasts
within skeletal muscle
2 multipotential/stem cell
3
myonucleus
1
satellite cell
myofibre
(only part is shown)
myoblasts
myotubes
Plasticity
Resident C/T cells
pluripotent STEM cells (multi)
progenitor cells
Vascular
endothelial
smooth muscle
pericytes
Myofibroblasts
Ectopic cells (chickens)
Thymus (myoid cells)
Neural (multi)
Dermis
Circulating bone-marrow *(multi)
skeletal
cardiac
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Healthy donor bone-marrow
derived stem cells to repopulate
diseased host tissues
3. Correction
or replacement
of
DONOR
bone marrow
stem cells
Inject healthy donor stem cells
derived from another person.
These circulating donor stem
cells may repopulate any
damaged host tissue e.g heart
Issues of immune rejection
of foreign cells can be reduced
by using closely matched
donor and host cells.
2. Separation of
HOST specific
stem
cell type
Issues of immune
rejection
of foreign.
Possibilities to explain presence of bone-marrow derived (donor) nucleus
(cell) within a (host) cell or tissue. Illustrated for muscle
Bone-marrow
stem cell
1
(1) Muscle precursor cell with limited
proliferation
Conversion
A
(2) Ideal scenario = Muscle Stem cell
with capacity to form
many (cardio)myoblasts
2
Conversion
B
Asymmetric Cell division
Bone-marrow
stem cell
1
Conversion
(1) Muscle precursor cell with limited
proliferation
A
(2) Muscle Stem cell
2
X
Conversion
B
capacity to form many
(cardio)myoblasts
Asymetric Cell division
(3) Fusion of 2 cells
Fusion
+
3
C
Stem
cell
Hybrid
stem-muscle cell
with 2 or more nuclei
The stem cell has NOT become a muscle cell
Autograft of genetically corrected stem
cells: delivered through the circulation
3. Correction or
replacement of
defective gene in
host stem cell
4. Infusion of host’s
corrected stem cells to
replace or supplement
defective host cells
Use of own cells avoids
immune problems
and rejection
2. Separation of
specific type of
host stem cell
1. Remove patient’s
bone-marrow
Two studies show that few of the bone-marrow
derived nuclei located within muscle cells
actually express muscle-specific genes:
indicating fusion without lineage conversion
• Beth McNally (normal male) bone marrow (b/m)
reconstitution of female sarcoglycan (SG) deficient host mice:
The rare male b/m-derived nuclei within some myofibres
and heart muscle cells, showed NO expression of SG
Lapidos KA et al (2004)
• Anton Wernig male/GFP b/m reconstitution of female mdx
(dystrophin deficient) mice: ~80% of male b/m myonuclei
showed NO expression of skeletal muscle specific genes
Wernig G et al (2005) 3 labels: Y-probe, GFP, dystrophin
1
Donor nucleus (Y-FISH) without dystrophin
expression
WERNIG G et al (2005)
1, 2: SERIAL
SECTIONS
Current interest in blood vessel
derived circulating
STEM CELLS: mesangioblasts.
Sampaolesi M…. Cossu J (2006). Mesoangioblast stem cells ameliorate
muscle function in dystrophic dogs. Nature Nov 15.
Major problems in data interpretation due to lack of fundamental controls
Dogs injected with immunosuppressants alone (without stem cells) were not included. Yet….
Cyclosporine alone reduces severity of muscular dystrophy
Precise source of stem cells?
Poor correlation between increased dystrophin immunostaining (derived from the circulating stem cells) and
improved muscle function.
Potential issues with digital imaging and image enhancement
Confounded by high biological variation
Causes major confusion and distress for families of boys with DMD who are seeking a cure/treatment
Davies K, Grounds MD (2006) Treating muscular dystrophy with stem cells? Cell. Dec 29.
Grounds MD, Davies K (2007) The allure of stem cell therapy for muscular dystrophy. Neuromuscular
Disorders March.
KEY issues for research
•INDUCERS to recruit/convert stem
cells into specific lineages: critical
effects of environment (Plasticity)
•EXPANSION of cell numbers
(proliferation and stem cell renewal)
•Stem cell isolation/identification
Properties of STEM cells
Plasticity
Self renewal