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STEM CELLS
A cell that has the ability to continuously divide and differentiate
(develop) into various other kind(s) of cells/tissues.
Stem Cell Characteristics:
Blank cells’ (unspecialized)
Capable of dividing and renewing themselves for long periods of
time (proliferation and renewal)
Have the potential to give rise to specialized cell types
(differentiation)
Self renewable: a cell that has the ability to continuously divide
Pluripotent: ability to develop into several different kinds of
cells/tissues
Repair: ability to return function to damaged cells in the living
organism
Stem cells are unique body cells.
• Stem cells have the ability to
– divide and renew themselves
– remain undifferentiated in form
– develop into a variety of specialized cell types
Stem cells are classified into three types.
Totipotent: growing into any other cell type
Pluripotent: growing into any cell type but a totipotent
cell
Multipotent: growing into cells of a closely related cell
family
Kinds of stem cells
• Embryonic stem cells: come from a five to six-day-old
embryo. They have the ability to form virtually any
type of cell found in the human body.
• Embryonic germ cells: are derived from the part of a
human embryo or foetus that will ultimately produce
eggs or sperm (gametes).
• Adult stem cells: are undifferentiated cells found
among specialised or differentiated cells in a tissue or
organ after birth. (Or) Stem cells found in adult
organisms, for instance in bone marrow, are called adult
stem cells.
• Based on current research they appear to have a more
restricted ability to produce different cell types and to
self-renew.
•Scientists have recently demonstrated that stem
cells, both embryonic and adult, with the right
laboratory culture conditions, differentiate into
specialized cells.
Embryonic stem cells
Embryonic Stem Cells (ESC): received from:
• Embryos created in vitro fertilization
• Aborted embryos
Source of ESC:
1. Blastocyst
• “ball of cells”
• 3-5 day old embryo
• Stem cells give rise to multiple specialized cell types
that make up the heart, lung, skin, and other tissues
2. Human ESC were only studied since 1998
• It took scientists 20 years to learn how to grow human
ESC following studies with mouse ESC
• How are embryonic stem cells harvested?
• Human ES cells are derived from 4-5 day old
blastocyst
• Blastocyst structures include:
• Trophoblast: outer layer of cells that surrounds
the blastocyst & forms the placenta
• Blastocoel: (“blastoseel”) the hollow cavity inside
the blastocyst that will form body cavity
• Inner cell mass: a group of approx. 30 cells at one
end of the blastocoel:
• Forms 3 germ layers that form all embryonic
tissues (endoderm, mesoderm, ectoderm)
Stages of Embryogenesis
Stages of Embryogenesis
Day 1
Fertilized egg
4/16/2014
Day 2
2-cell embryo
Day 11-14
Dr. Hariom Yadav
Tissue Differentiation
Day 3-4
Multi-cell embryo
Day 5-6
Blastocyst
Blastocyst Diagram
Development of specialized cells
Adult stem cells
• Adult Stem Cells (ASC): can be received from:
– Limited tissues (bone marrow, muscle, brain)
• Discrete populations of adult stem cells
generate replacements for cells that are lost
through normal wear and tear, injury or disease
– Placental cord
– Baby teeth
Continued..
• Adult or somatic stem cells have unknown origin in
mature tissues
– Unlike embryonic stem cells, which are defined by
their origin (inner cell mass of the blastocyst)
• Adult stem cells typically generate the cell types of the
tissue in which they reside
– Stem cells that reside in bone marrow give rise to RBC,
WBC and platelets
– Recent experiments have raised the possibility that
stem cells from one tissue can give rise to other cell
types
• This is known as PLASTICITY
• Ex: Blood cells becoming neurons, Liver cells stimulated
to produce insulin, Hematopoietic (blood cell producing)
stem cells that become heart cells
Applications
• Basic research – clarification of complex events that
occur during human development & understanding
molecular basis of cancer
• Molecular mechanisms for gene control
• Role of signals in gene expression & differentiation of the stem cell
• Stem cell theory of cancer
•
• Biotechnology(drug discovery & development) – stem
cells can provide specific cell types to test new drugs
– Safety testing of new drugs on differentiated cell lines
– Screening of potential drugs
• Cancer cell lines are already being used to screen potential antitumor drugs
• Availability of pluripotent stem cells would allow drug testing in a
wider range of cell types & to reduce animal testing
Continued..
• Cell based therapies:
– Regenerative therapy to treat Parkinson’s,
Alzheimer’s, ALS, spinal cord injury, stroke, severe
burns, heart disease, diabetes, osteoarthritis, and
rheumatoid arthritis
– Stem cells in gene therapy
– Stem cells as vehicles after they have been
genetically manipulated
– Stem cells in therapeutic cloning
– Stem cells in cancer
• The use of stem cells offers many currently realized and
potential benefits.
– Stem cells are used to treat leukemia and lymphoma.
– Stem cells may cure disease or replace damaged organs.
– Stem cells may revolutionize the drug development process.