2014 02 stem cell introduction 860461
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Stem Cell Basics
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Stem cell
remarkable potential to develop intomany different cell types
Serving as a sort of repair systemfor the body
divide without limits become another type of cell with a
more specialized function, such as amuscle cell, a red blood cell, or abrain cell.
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introduction This is a promising area of sciences how an organism develops from a
single cell how healthy cells replace damaged
cells in adult organisms. regenerative or reparative
medicine : investigate the possibility of cell-
based therapies to treat disease
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What are stem cells and why are they
important?
Stem cells have two importantcharacteristics that distinguish them fromother types of cells
#they are unspecialized cells #they can be induced to become cellswith special functions heart, pancreas
tow kind of cells from human andanimals
!mbryonic stem cell and adult stem cell There is a different functions and
characteristic
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"rom early mouse embryos , $ y.ago
%&&' it is isolated from human embryos :human embryonic stemcells
(y way of in vitro fertilization
procedures.
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Stem cells are important for living organismsbecause :
)n the blastocyst stem cells give multiplespecialized cell types
)n some adult tissues, adult stem cells generatereplacements for cells that are lost throughnormal wear and tear, in*ury, or disease.
)t has been hypothesized that stem cells may, atsome point in the future, become the basis for
treating diseases such as +arkinsons disease,diabetes, and heart disease.
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(y studding stem cell
they can learn about their essentialproperties and what makes them different
from specialized cell types it may become possible to use the cells
not *ust in cell-based therapies,
but also for screening new drugs andtoins and understanding birth defects.
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the fundamental properties ofstem cells, which include:
%-determining precisely how stemcells remain unspecialized and selfrenewing for many years and
-identifying the signals that
cause stem cells to becomespecialized cells.
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What are the unique properties of all
stem cells?
/ll stem cells have 0 generalproperties :
%. capable of dividing and renewingthemselves for long periods
. they are unspecialized
0. they can give rise to specialized celltypes.
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Scientists are trying to understand two
fundamental properties
1why can embryonic stem cells proliferate for a year or more in thelaboratory without differentiating, but most adult stem cells cannot
1what are the factors in living organisms that normally regulate stem cellproliferation and self-renewal2
the answers
understand how cell proliferationis regulated during normal embryonic development
during the abnormal cell division that leads to cancer
such information would enable scientists to grow embryonic andadult stem cells more efficiently in the laboratory.
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Stem cells are unspecialized.
There is no tissue-specific structures thatallow it to perform specialized functions
3owever, unspecialized stem cells can give riseto specialized cells, including heart muscle cells, blood cells, or nerve cells.
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Stem cells are capable of dividing and
renewing themselves for long periods
stem cells may replicate many times unlike musclecells, blood cells, or nerve cells
That can yield millions of cells in the laboratory
)f the resulting cells continue to be unspecialized,like the parent stem cells, the cells are said to becapable of long-term self-renewal.
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Stem cells can give rise to specialized
cells
4ifferentiation : unspecialized stem cells
specialized cells
The internal signals are controlled by a cells genes
They are interspersed across long strands of 45/, andcarry coded instructions for all the structures and functionsof a cell
trigger
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The eternal signals for cell differentiation include
chemicals secreted by other cells
physical contact with neighboring cells
and certain molecules in the microenvironment 6uestions remain: are the internal and eternal signals for cell differentiation similar
for all kinds of stem cells2
7an specific sets of signals be identified that promotedifferentiation into specific cell types2
the answers may lead to find new ways of controllingstem cell differentiation in the laboratory, thereby growingcells or tissues that can be used for specific purposes
cell-based therapies.
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/dult stem cells typically generate the cell types ofthe tissue in which they reside
)n bon marrow / blood-forming adult stem cell8hematopoietic stem cell 9 gives red, white, and
platelets. only ecently it is raised the possibility that stem cells from
one tissue may be able to give rise to cell types of acompletely different tissue
blood cell neurons ;liver cells heart muscle.
plasticity
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Stem Cell Basics
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Stem Cell Basics
The fertilized eggs are not derived fromeggs fertilized in a womans body theyare donated for research purposes withinformed consent of the donors by
(. 3ow are embryonic stem cells grownin the laboratory2
cellculture
)nner cell mass
)n nutrient culture medium
"eeder layer
subculturing
passage , after =month or more the
original 0$ cells of the inner cell massyield millions of embryonic stem cellscalled embryonic stem cell line
(y pluripotent 8 proliferation without
differentiation 9
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C. What laboratory tests are used to identify embryonic stem cells?
characterization : test the cells to see whether theyehibit the fundamental properties that make themembryonic stem cells
>any kind of testes :1 growing and subculturing the stem cellsfor many months microscope inspection for the healthy and
undifferentiated of cells. 1 using specific techni?ues to determine the presence
of surface markers that are found only on undifferentiated cells 1presence of a protein called @ct-A ; a transcription
factor ;it helps turn genes on and off at the right time ;it is an important part of the processes of cell differentiation andembryonic development.
1eamining the chromosomes under amicroscope ; the chromosomes are damaged 2;thenumber of chromosomes has changed 2;)t does not detectgenetic mutations in the cells.
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1determining whether the cells can be subcultured after freezing,thawing, and replating
1testing whether the human embryonic stem cells are pluripotentby :
%9 allowing the cells to differentiate spontaneously in cell culture
9 manipulating the cells so they will differentiate to form specific celltypes
09 in*ecting the cells into an immunosuppressed mouse to test for theformation of a benign tumor called a teratoma
1Teratomas typically contain a miture of many differentiated or partly differentiatedcell types
1an indication that the embryonic stem cells are capable of differentiating into multiple
cell types.
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scientists try to control the differentiation of embryonic stem cells They change the chemical composition of the culture medium ;
alter the surface of the culture dish ;
modify the cells by inserting specific genes ;
Through years of eperimentation scientists have established some basic
protocols or BrecipesB for the directed differentiation of embryonic stemcells into some specific cell types
)f scientists can reliably direct the differentiation of embryonic stem cellsinto specific cell types, they may be able to use the resulting,differentiated cells to treat certain diseases at some point in the future.4iseases that might be treated by transplanting cells generated from
human embryonic stem cells include +arkinsons disease, diabetes,
traumatic spinal cord in*ury, +urkin*e cell degeneration,4uchennes muscular dystrophy, heart disease, and vision andhearing loss.
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What are adult stem cells?
undifferentiated cell found among differentiatedcells in a tissue or organ
7an renew it self
7an differentiates to yield the ma*or specialized celltypes of the tissue or organ
The primary roles of adult stem cells in a livingorganism are to maintain and repair the tissue inwhich they are found.
somatic stem cell ,, Cnlike embryonic stem cells , the origin is unknown
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What are adult stem cells?
7an adult stem cell been used in transplant 2
adult blood forming stem cells from bone marrowhave been used in transplants for 0$ years
the ability to differentiate into a number of differentcell types
these cells may become the basis of therapies formany serious common diseases.
)n the %&=$shematopoietic stem cells
bone marrowstromal cells
Stromal cells are a mied cell population that generates bone,cartilage, fat, and fibrousconnective tissue
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A. Where are adult stem cells found and what do
they normally do?
most scientists believed that new nerve cells could not be generated in theadult brain.
)t was not until the %&&$s that scientists agreed that the adult brain doescontain stem cells that are able to generate the brains three ma*or celltypesDastrocytes and oligodendrocytes, which are non-neuronal cells,and neurons, or nerve cells.
adult stem cells have been identified in many organs and tissues
very small number ; reside in a specific area ;they may remain?uiescent 8non-dividing9 for many years
until they are activated by disease or tissue in*ury
laboratories are trying to find ways to grow adult stem cells in
cell culture manipulate them to generate specific cell types so they can be
used to treat in*ury or disease
+arkinsons patients ;type ) diabetes ;heart attack
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B. What tests are used for identifying adult stem
cells?
There is no agreement about identify E test S7 0 methods :18%9 labeling the cells in a living tissue with molecular markers and then
determining the specialized cell types they generate 1
1 89 removing the cells from a living animal
labeling them in cell culture
transplanting them back into another animal to determine whetherthe cells repopulate their tissue of origin 1
1809 isolating the cells
growing them in cell culture and manipulating them
often by adding growth factors or introducing new genes
to determine what differentiated cells types they can become. /S7 cam make a clone8 line of genetically identical cells9 in the tissue reside
by infecting adult stem cells with a virus that gives a uni?ue identifier to eachindividual cell, scientists have been able to demonstrate that individual adult stem cellclones have the ability to repopulate in*ured tissues in a living animal.
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C. What is known about adult stem
cell differentiation?
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4ifferentiation
transdifferentiation ; plasticity
3ematopoietic stem cells F.
mesenchymal stem cells8 bon marrow S79 F..
neural stem cells F..
!pithelial stem cells
Skin stem cells epidermis3air follicle
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transdifferentiation / plasticity
certain adult stem cell types are pluripotent
eamples of adult stem cell plasticity that have beenreported during the past few years:
3ematopoietic stem cells 0ma*or type of
brain ;skeletal muscle ;cardiac muscl;liver cell; (one marrow stromal cells may differentiate into : cardiac; skeletal muscle
(rain stem cells may differentiate into :
blood ; skeletal muscle 7urrent research is aimed at determining the mechanisms that underlie adult stem cellplasticity. )f such mechanisms can be identified and controlled, eisting stem cells froma healthy tissue might be induced to repopulate and repair a diseased tissue
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D. What are the key questions about adult stem
cells?
>any important ?uestions about adult stem cells remain to be answered They include:
3ow many kinds of adult stem cells eist, and in which tissues do they eist2
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V. What are the similarities and differences
between embryonic and adult stem cells?
!mbryonic stem cells are pluripotent
Garge numbers of embryonic stem cellscan be relatively easily grown in culture
large numbers of cells are needed for stem cellreplacement therapies
!mbryonic stem cells from a donorintroduced into a patient could causetransplant re*ection
/dult stem cells are generally limited 3owever, adult stem cell plasticity may eist
adult stem cells are rare in maturetissues
The use of own adult stem cell would
not be re*ected by immune system
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V. What are the potential uses of human stem cells
and the obstacles that must be o!ercome before
these potential uses will be reali"ed?
>ay of ways and many pf hurdles identify how undifferentiated stem cells become differentiated Scientists know that turning genes on and off is central to this process abnormal cell division and differentiation 7ancer and birth defects H other serious conditions
/ better understanding of the genetic and molecular controls of these processes how such diseases arise and new strategies for therapy arise hurdle : scientists do not yet fully understand the signals that turn
specific genes on and off to influence the differentiation of the stem cell.
used to test new drugs: safety differentiated , anti-tumor drugs screen drugs effectively but identical +erhaps the most important potential application of human stem cells is the generation
of cells and tissues that could be used for cell-based therapies Stem cell directed to differentiate into specific cell types for replacement cells and
tissues parkinson’s II Alzheimer's II spinal cord injury II stroke II burns IIheart I diabetes II osteoarthritis II rheumatoid arthritis
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#or e$ample it may be possible to direct the differentiation of embryonic stemc. or adult bon marrow cell into heart muscle cell % cell culture&
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)n type J diabetes can be treated "or successful cell-based treatment , stem c. must be : proliferate etensively and generate sufficient ?uantities
of tissue
4ifferentiate into the desired cell type8s9 Survive in recipient after transplant )ntegrate into the surrounding tissue after transplant "unction appropriately for the duration of the recipientKs
life /void harming the recipient in any way Tissuse shouldKnt be re*ected The promise of stem cell therapies is an eicting one Significant technical hurdles remain111
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'( support research for
embryonic stem cell line
+roduced by dr. Salim DAGHER
4epartment of 3ealthand 3uman Se
http://www.os.dhhs.gov/http://usa.gov/http://www.os.dhhs.gov/http://www.nih.gov/http://www.os.dhhs.gov/