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stem cells
foundation for every tissue and organ in the body that can develop into many cell types within the body during and post development
stem cell function
replace injured tissues and cell types that are lost naturally by unlimited cell division
what are the 2 main properties of stem cells?
self renewal and differentiation
self renewal
the ability to generate more stem cell through symmetric or asymmetric division
stem cell division
each daughter cell has potential to be a stem cell or become a specialized cell type
symmetric division
one cell divides into two identical undifferentiated cells
asymmetric division
one cell divides into one undifferentiated cell and one specialized committed daughter cell
depletion
stem cell pool is depleted to make two committed specialized daughter cells
totipotent
can produce an entire viable organism including extra embryonic cells
pluripotent
can produce derivatives from each primary embryonic lineage (germ layers) under certain conditions
multipotent
can produce multiple cell types within a single germ layer with a tissue specific function
unipotent
can only produce one cell type
progenitor cells
an undifferentiated cell with a limited ability to self renew
pacemaker cells
controls heartbeat
purkinje fibers
role in electrical conduction and propagation of impulse to the ventricular muscle, has potential to cause arrythmias
extraembryonic cells
cells that form tissues that assist in embryo development
potency
varying ability of cells to differentiate into specialized cell types
pluripotent cells in the blastocyst
inner mass cells and epiblast
multipotent cells in the blastocyst
trophectoderm, hypoblast, extraembryonic mesoderm and the yolk sac
gastrulation
creates the endoderm, ectoderm and mesoderm but reslts in the depletion of almost all pluripotent cells in the embryo
niche
a specific sub tissue location that physically and chemically supports stem cells in the body
germ layers
distinguishable groups of cells created by gastrulation in early development and each layer contributes to specific tissues in the body
teratoma
benign germ cell tumor
teratocarcinoma
malignant germ cell tumor
embryonal carcinoma
indvidual pluripotent cells that can divide indefinitely and differentiate into teratomas when injected into mice
Till and McCulloh’s stem cell theory
showed that multipotent stem cells exist in mouse bone marrow
developmental hourglass theory
post gastrulation embryos from different animals look similar
coculture system
2 different cell types are grown in the same culture dish and support each other's growth
chimera
a single organism that is composed of genetically distinct cells
how were embryonic stem cells discovered?
entero chromafftin cells were used to create the first pluripotency assay and improve cell culture conditions for embryonic cells by adding a layer of mouse embryonic fibroblasts
how were induced pluripotent stem cells created?
by reprogramming adult tissue specific cells into cells that act like ESCs by using isolated mice fibroblasts and transforming them into Yamanaka factors
yamanaka factors
transcription factors that can generate any cell type
oct4 sox2 kl4 and c-myc
pulse chase experiment
short term exposure of living tissues to BrdU will label cells that are actively undergoing cell division for detection later with anti BrdU antibodies
BrdU
bromodeoxyuridine, type of chemical nucleoside analogue used during DNA replication
where are the BrdU cells located?
they start at the intestinal crypt and migrate up the villi
bone marrow adult stem cells discovery
radiation delivered to a healthy mouse causing depletion of blood cells then transplanted healthy bone marrow into the irradiated mouse and found that the cells repopulated restoring the blood cells through self renewal and differentiation due to colonies in the spleen
colony or cell morphology
evaluating if a cell looks like a stem cell (least informative)
marker abundance
determining if cell is undifferentiated or not based on the presence of stem cell transcription factors
single cell cloning
isolate a single cell and dispense it into a culture vessel allowing it to grow into a colony of cells to see if it generates similar cells or not
serial transplantation
test ability of cell to repopulate niche then resample that niche and have it repopulate in another animal
tissue integration
see if a cell contributes to function of an organism and its survival (most informative way to identify a stem cell)
totipotent stem cell hierarchy
fertilized egg, zygote, morula
pluripotent stem cell hierarchy
blastocyst, ESCs from inner mass cell, germ cells
multipotent stem cell hierarchy
hemapoeitic, neural and mesenchymal stem cells
lineage committed stem cell hierarchy
blood cells, cells of the nervous system, connective tissue, bone, cartilage, etc