Core Course # MM 704
(Cellular and Molecular Pathology)
Cell cycle (Cell division), Cell-cell interaction, growth
and their control
Aging
Apoptosis
Tissue injury and repair mechanisms
Cell regenerating potential (Role of Stem Cells)
Mediators, modulators and messengers
Antioxidants in health and disease
Outline of Lecture
Stem Cells
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Definition
Types
Identification Criteria
Trans-differentiation
Regenerative Medicine
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Definition
Types
Potentials e.g. Regeneration of Cells and Tissues
STEM CELLS
Stem Cells
Three general properties:
(1) are unspecialized
(2) capable of dividing and renewing themselves for long
periods (proliferation)
(3) can give rise to specialized cell types (differentiation)
Definition: Stem cells are primary cells present in all multicellular organisms that retain the ability or potential to renew
themselves through cell division and can differentiate into a
wide range of specialized cell types
Types of Stem Cells on the basis of their
Differentiation Potential
(1) Totipotent:
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have the potential to become any cell type in the body.
are produced from the fusion of an egg and sperm cell.
(2) Pluripotent:
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are derived from totipotent cells.
have the potential to make any differentiated cell in the body (but not all).
(3) Multipotent:
can only differentiate into a limited number of types or can produce only cells
of a closely related family of cells e.g. hematopoietic stem cells.
(4) Unipotent
cells can produce only one cell type, but have the property of self-renewal
which distinguishes them from non-stem cells.
Stem Cells and their Differentiation Potential
Types of Stem Cells on the basis of their
Source
Embryonic Stem Cells
Adult Stem Cells
Embryonic Stem Cells
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are derived from inner cell mass of
four or five days old embryos
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unique ability of unlimited expansion
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are a potential source for regenerative
medicine and tissue replacement after
injury or disease
Sources of Embryonic Stem Cells
1. Excess fertilized eggs from IVF (in-vitro fertilization) clinics
2. Therapeutic cloning (somatic cell nuclear transfer)
Tens of thousands of
frozen embryos are
routinely destroyed.
These surplus embryos
can be used to produce
stem cells.
The nucleus of a donated
egg is removed and
replaced with the nucleus
of a mature, "somatic cell"
(a skin cell, for example).
The resulting stem cells can
potentially develop into
specialized cells that are
useful for treating severe
illnesses.
Identification of Embryonic Stem Cells
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Long-term self-renewal
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Undifferentiated for long periods
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Presence of surface markers found only on undifferentiated
cells e.g. Oct-4
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Pluripotent state by allowing cells to differentiate
spontaneously in cell culture; manipulating cells so they will
differentiate to form specific cell types; or injecting cells into
an immuno-suppressed mouse to test for the formation of a
benign tumor called a teratoma
Trans-differentiation property (Plasticity)
Advantages:
 can become all cell types of the body
 can be relatively easily grown in culture
Disadvantages:
 Safety and effectiveness in humans is controversial
 They can grow out-of-control forming tumors
 They can change into unintended types of cells
 They can cause transplant rejection
Adult Stem Cells
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undifferentiated cells found among differentiated cells
in a tissue or organ
can renew themselves
can differentiate to yield major specialized cell types
of the tissue or organ
maintain and repair the tissue in which they are found
Types of Adult Stem Cells
Bone Marrow
Adipose Tissue
Cord Blood
Liver
Muscle
Brain
Placenta
Pancreas
Retina
Skin
Hematopoeitic Stem Cells
Mesenchymal Stem Cells or Stromal Cells
Identification of Adult Stem Cells
cKit
CD44
CD90
Western Blotting
Immuno-cytochemistry
Flow Cytometry
Cardiovasc Ther. 2012 Jun 15. doi: 10.1111/j.1755-5922.2012.00320.x
Trans-differentiation Potential of Adult Stem Cells
Advantages:
 No danger of immune rejection with cells from the
patient's own body
 Extremely low risk of tumor growth
 Easier to control than embryonic cells
 No significant ethical issues
Disadvantages:
 present in the body in very small numbers
 more limited in differentiation than embryonic cells
Induced Pluripotent Stem Cells (iPSCs)
 Adult cells genetically reprogrammed to an embryonic stem
cell–like state by introducing specific genes through viruses
 Mouse iPSCs were first reported in 2006, and human
iPSCs were first reported in late 2007
 Mouse and Human iPSCs demonstrate characteristics of
pluripotent stem cells, e.g. stem cell markers, generate cells
of all three germ layers
 Tissues derived from iPSCs will be a nearly identical match
to the cell donor and thus probably avoid rejection by the
immune system
 This discovery has created a powerful new way to “dedifferentiate” cells whose developmental fates had been
previously assumed to be determined
REGENERATIVE MEDICINE
Definition: A technique to replace, repair, maintain or
enhance tissue or organ functions by in vitro design while in
vivo usage
Why do we use Regenerative Medicine
Most human tissues do not regenerate spontaneously
Parkinson's disease
Spinal cord injury
IDDM
Multiple Sclerosis (MS)
Myocardial Infarction
Types of regenerative medicine
1. Cell Therapy
2. Tissue Engineering
Cells and Tissues in Regenerative Medicine
Reconstructive Surgery
1. a. growing suitable cells (e.g. adult stem cells) in laboratory
flasks
b. Injecting them directly into a tissue needing repair
or
into the blood stream (homing to the site of injury)
(Cell Therapy)
2. building an organ or tissue outside the body
e.g. scaffold-like structure (Tissue Engineering)
Cell Therapy
Transplantation of human or animal cells to replace or
repair damaged tissue and/or cells.
Applications
 to rebuild damaged cartilage in joints
 repair spinal cord injuries
 autoimmune diseases (AIDS)
 neurological disorders (Alzheimer‘s disease,
Parkinson's disease, etc).
Tissue Engineering
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The regeneration of
biological tissues through
the use of cells, with the
aid of supporting structures
and/or biomolecules.
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Culture, expansion and/or
differentiation of the cells
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Regenerated tissue
transplanted into the body
Scaffold: Characteristics
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The scaffold should mimic the structure and biological
function of native extra cellular matrix (ECM)
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The structures can vary from sponge like sheets and
fabrics to gels or highly complex structures
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Scaffolds are porous. The porosity of the scaffold and
interconnectivity of the pores enable cell penetration into
the structure as well as the transport of nutrients and
waste products
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Degradable structures fabricated from either natural
materials or synthetic polymers
(J.Cell.Mol.Med.
Vol. 11,654-69, 2007)
Skin Regeneration
(Nature Vol. 414,118-121, 2001)
Bone Regeneration
(Nature Vol. 414,118-121, 2001)
(J.Cell.Mol.Med. Vol. 11,654-69, 2007)
Cardiac Regeneration
Myogenic transdifferentiation of MSC at 4
weeks after cell transplantation
FITC actinin staining
Red PKH26 staining
DAPI Nuclear staining
Merge
Circulation Res. Vol 99, 776-784. 2006
Small Molecules and Stem Cells
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Direct Differentiation of ES Cells
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Direct Differentiation of MSCs
Differentiation of the Adult Stem Cells into Cardiac
like cells by Small Molecules
Cardiovasc Ther. 2012 Jun 15. doi: 10.1111/j.1755-5922.2012.00320.x
References
http://stemcells.nih.gov/info/Pages/Default.aspx
Cardiovasc Ther. 2012 Jun 15. doi: 10.1111/j.1755
5922.2012.00320.x
Circulation Res. Vol 99, 776-84. 2006
Nature Vol. 414,118-21, 2001
J.Cell.Mol.Med. Vol. 11,654-69, 2007