stem cells Flashcards
stem cells and reproductive ethics
what are stem cells
founder cells that can self renew - one of their daughter cells is an exact copy and the other is a differentiated version
what can stem cells generate
tissues, organs and whole organisms
are stem cells found in tissues specialised
no they are unspecialised but they have the potential to differentiate in to cells that are specialised for theta specific tissue
what is the normal role of stem cells in the body
to maintain and renew the organ they are contained in throughout the life of the organism
what is totipotent and give an example
he cell that is capable of developing into any cell type. e.g. fertilised egg - can differentiate into any type of cell in the embryo or placenta
what is pluripotent and give an example
they have the potential to differentiate into almost any cell in the body - different to totipotent because they can produce entire organisms or placentas e.g. the cells in the blastocyst are pluripotent
what is multipotent and give an example
a multipotent stem cell can give rise to other types of cells but it is limited in its ability to differentiate
Examples of multipotent stem cells include those in the brain that give rise to different neural cells and glia or haematopoietic cells, which can give rise to different blood cell types, but they can’t create brain cells. Bone marrow also contains multipotent stem cells that give rise to all blood cell types but not other cells.
adult stem cell are considered multipotent
are also known as mesenchymal cells
what is unipotent and give an example
A unipotent stem cell refers to a cell that can differentiate along only one lineage
they can only differentiate into cells of their tissue type
they e.g. stem cells found in bone marrow can only produce blood cells or stem cells of the heart can only produced heart cells etc
what is a mature cell and give an example
the fully differentiated cell e.g. connective tissue, blood cells, cells of the nervous system
why are stem cells useful in research
- they have a high rate of proliferation
- they can be used for medical research to look at human characteristics without having to do human trials
how are stem cells useful in regenerative medicine
they replace, repair, restore and regenerate tissues
we can replace cells or tissues after injury with stem cells or stem cell derived tissue
what are the different names for adult stem cells
tissue specific
somatic
mesenchymal cells
give examples of where adult stem cells can be found
brain heart bone marrow umbilical chord at birth foetal tissues and organs after pregnancy termination
what is the difference between autologous and allogenic
they are processes of transplanting stem cells and they differ in where the stem cells come from
what is autologous transfer
take stem cells from an individual and return them to the same person
what is allogenic transfer
take stem cells from an individual and give them t a different person
as a cell becomes more differentiated, what happens to the rate of proliferation
proliferation rate decreases as a cell becomes more specialised
by what process do hematopoietic stem cells give rise to all other blood cells
haematopoiesis - the cells are derived from the mesoderm in the red bone marrow which is contained in the core of most bones
what can bone marrow transplant be used to treat
leukaemia
sickle cell anaemia
immune deficiencies
MS
where are embryonic stem cells isolated from
the blastocyst stage embryo
what is a knock out
removes a gene of interest
what is a knock in
replaces part of a gene and usually disrupts the gene as a consequence. Can use to mark cells
what is inducible excision
systems allows removal of un-needed components from vector and can also be used to induce temporal or lineage specific effects
what are genetically modified organisms called
transgenic
what are hematopoietic stem cells
stem cells that give rise to other blood cells. This process is called haematopoiesis. This process occurs in the red bone marrow, in the core of most bones. In embryonic development, the red bone marrow is derived from the layer of the embryo called the mesoderm.
how are murine embryonic stem cells used to make transgenic mice
- stem cell cultivation -embryonic stem cells are removed from the embryo of a normal mouse
- introduction of targeted gene - DNA containing a modified or deactivated gene is introduced. the stem cells that take up the new gene are allowed to proliferate
- stem cell injection - the modified stem cells are injected into the blastocyst and implanted in surrogate mother, which gives birth to a chimeric mouse that contains both normal and genetically modified genes
- breeding – the chimeric mouse is mated with a normal mouse - offspring include normal mice and mice with the new gene in every cell
how is fluorescent gene marker expression used in producing transgenic mice
they can be used to produce GFP+ mice
- stem cells are isolated and transplanted into a wild type mouse
- GFP+ tissues are derived from the transplanted cells
- the location of the GFP+ (and so stem cells) can be tracked
GFP+ can be made specific to tissues
what is GFP+
green fluorescent protein - it is a reporter protein
describe the main features of human embryonic stem cells
they are derived from the inner cell mass of the blastocyst
they self renew and expand indefinitely in culture
they are pluripotent - able too derive all cells from all 3 dermal layers
what are the 3 dermal layers
endoderm - lung, liver
mesoderm - blood, cardiomyocyte
ectoderm - neural, skin
what are the main ethical objections to the use of human embryonic stem cells
- they are taken from a very early stage blastocyst. when does the embryo become a life?
- many religions oppose
- there are a range of policies for the use of hESC across he world
what are some of the applications of embryonic stem cells
basic research drug testing - disease and patient specific cells toxicology - normal human cell supply drug discovery therapy
what are the current concerns over the use of hESC
scientific methods need to be refined - differentiation is often still mixed
potential for teratoma formation from undifferentiated hESC
to use as a therapy we would need a bank to tissue match otherwise there would be immune rejection issues
animal products are used in culture - infection risk
what is a teratoma
An often-benign tumour containing tissues of more than one germ layer, arising from totipotent cells, often occur in the ovary or testes
Might arise if pluripotent cells were left in therapies of differentiated cells.
tumours that may produce fully mature tissues forming e.g. teeth and hair
how can stem cells be used in cloning
- the nucleus is removed from a donor egg
- nucleus transplanted from the patients cell to the egg
what kind of transfer does non reproductive (therapeutic) cloning use
autologous
- blastocyst made using enucleated oocyte and a nucleus from patient cell
- these are then grown into pluripotent ES cells
- these are then differentiated into the cell of interest e.g. liver cells
what is reproductive cloning
the production of new individuals
- using an enucleated oocyte and a patient cell nucleus to make a blastocyst
- blastocyst is then implanted into the uterus
- birth of clone
compare the origin of adult and embryonic stem cells when used in therapy
adult - autologous or allogenic
embryonic - allogenic
compare the expansion of adult and embryonic stem cells when used in therapy
adult - poor
embryonic - limitless
compare the differentiation of adult and embryonic stem cells when used in therapy
adult - limited lineages
embryonic - all cells of the body
compare the ethics of adult and embryonic stem cells when used in therapy
adult - few issues
embryonic - pro life issues
which type of stem cells can be reprogrammed into induced pluripotent stem cells
adult stem cells
what type of genes are silenced in fully reprogrammed iPSC
exogenous
which type of gene expression is re-established in iPSC
endogenous
what is the double potential of induced pluripotent cells
they can be used for cell therapy and drug discovery
how are ALS neurons created from stem cells
- skin cells are taken from the ALS donors and put in a lab dish
- viruses insert four genes into the skin cells DNA, reprogramming the cells
- the skin cells form cell colonies similar to embryonic stem cells. these are induced pluripotent stem cells
- the iPSC are coaxed by signalling molecules into motor neurons. these can now be studied to see how ALS arises.
what are the advantages of induced pluripotent stem cells
they can be used to make person specific cell lines
no embryos are damaged
can make lines from people with genetic disease and study lineages e.g. ALS
what are the disadvantages of induced pluripotent stem cells
they are genetically modified
potential oncogenesis or damage to host genome
what is direct reprogramming -transdifferentiating
when somatic cells are made to form induced pluripotent stem cells which are then directed in their differentiation to produce the desired form of the somatic cell
do clones behave in the same way
no - it has been seen in cows all developed from the same cell line that certain cows are more dominant while others show more submissive behaviour
do clones always look the same
no - a cat clone had a different coat due to random X chromosome inactivation (a normal occurrence during development)
give an example of naturally occurring clones
identical twins – environmental influences and random phenomena play a significant role during development
what are some of the reasons for the low efficiency of cloning and the high incidence of abnormalities
- in fully differentiated cells a small subset of genes is turned on and expression of the rest of the genes is repressed. this often results in the epigenetic changes of chromatin such as acetylation of histones or methylation of DNA
- ## methylation helps regulate gene expression so increased methylation may interfere with the gene expression necessary for normal embryonic development
what is the main reason that researchers have been trying to clone human embryos
so they can produce stem cells to treat human diseases
what is the difference between the blastula and the blastocyst
the blastocyst is the same thing as the blastula but specific to humans
what is a progenitor cell
a cell that can differentiate into one of several cell types depending on external factors
what does a stem cell divide into
another stem cell and a progenitor cell
how could stem cells be used to treat type 1 diabetes
they could be used to produce insulin producing beta cells of the pancreas
what type of stem cell is pluripotent
embryonic
what is therapeutic cloning
when the main aim of cloning is to treat disease
how are induced pluripotent stem cells made
a retroviral vector is used to introduce 4 genes encoding transcription factors that convert adult stem cells into induced pluripotent stem cells
how do ES and IPS cells differ
there are some differences in gene expression and other cellular functions such as cell division
what are the 2 major uses of IPS cells
- disease study - cells form diseased patients have been reprogrammed to produce IPS cells which act as a model for studying the disease and potential treatments
- regenerative medicine - a patients own cells can be reprogrammed into IPS cells and used to replace non functional tissues such as pancreas beta cells
