Stem Cells Flashcards
characteristics of stem cells
not terminally differentiated
can divide without limit
can undergo slow division
gives rise to once stem cell and another to be differentited
adult stem cells are
tissue specific
totipotency
give rise to all cells of an organism, including embyronic and extraembryonic tussue
ex: zygote
pluripotency
give rise to all cells of the embryo and subsequent adult tissues
ex: embryo/blastocyst
multipotency
give rise to different cell types of a given lineage
ex: adult stem cells/various tissues
founder stem cells
proportions of body parts determined early
each tissue has fixed number of founder cell populations
programmed to have fixed number of divisions
controlled by short range signals that operate for a few hundred cell diameters
define the size of the large final structure
transit amplifying cells
cells that divide frequently
transit from a cell with stem cell characteristics to a differentiated cell
leave the basal layer and incorporate into the layers above
limited number of divisions (finite)
part of growth control, committed
immortal strand hypothesis
some tissues stem cells selectively retain original DNA to prevent errors thus the daughter cell will retain stem cell characteristics. The original DNA is preserved in all generations of that cell, while the other duaghter has the new DNA
self renewal
stem cell can go and make a new “committed” cell or just keep making the same of its own type of stem cell
stem cells differentiate in stages
stages involve multiple factors that combine to produce epigenetic markers in the cell’s DNA that restrict DNA expression and thus the type of cell that the stem cell will differentate into
DNA expression can pass on to daughter cells through cell division or daughter cellls can retain stem cell status and ability for long temr renewal (imortal strand hypothesis)
embryonic stem cells are derived from
the blastocyst
can proliferate indefinately with unrestrictred developmental potential and when put back into the embryo can reassimilate well
develope into different cell types
if injected into an embryo later on or in a n adult, they di not receive proper signal and can become tumors
embryonic stem cells can cause
teratomas
teratomas
ability to differentiate into wide range of tissues, no axis or segmentation, no body plan generation, lacks organization similar to ES cells in vitro after differentation
ES cell differentation becomes
cartilage, bone, skin, nervs, gut/resp. lining, when injected into host animals
human ES cells may be derived at
high frequency from good quality embryos
serum containing medium plus mouse pr human embryonic geeder cells
serum free medium with serum replacmeent and basic FGF
LIF and related cytokines have no effect
ES cell therapies
reliable, establishes pluripotency
induce development of specialized cell types, solve rejection problems
success in mouse with SCID, DM, Parkinson’s, Spinal injury, demyleination, MI
human ES cells express genes found in pluripotent cell populations manu of which code for
proteins with important roles in early embryonic development
Transcription factors are essential for
establishment and maintenaince of pluripotent stem cells in the embryo
NANog, Oct4, Sox2, FoxD3 common ones
GCNF is required for early stages of pluripotnet cell diff.
cripto and GDF-3 are growth factors found in pluripotent cells
adult stem cells found in
tissues, repsond to demands of growth and repair
there are growth, organization and repair restrictions
adult stem cells are strictly controlled by
molecular restarints on gene expression, heritable during manu round of cell division
may relax these rules in altered envirornment, allowing for plasticity (low frequency)
cord blood
cells are undifferentiated, no gene manipualted, ethical?
adult stem cells have the capacity to
differentiate in vitro and in vivo into chondrocytes, myoblasts, osteoblasts, pancreatic beta cells and neuronal like cells, and can regenerate neuronal cells
adult stem cells have two sources
bone marrow derived mesenchymal cells (transplant)
adipose derived mesenchyma stem cells (liposuction)
harvested adult stem cells have
memory of developmental history
cannot coerce to express the characteristics of something totally differnt which limits use
hematopoietic and stromal stem cells both come from
bone marrow
differ in what they can become
HSCs become
blood components, come from bone marrow and peripheral blood as well as cord blood
MSCs become
CT, other tissues found in wharton’s jelly, bone marrow, adipose, tooth pulp
A touch of regenerative medicine
pluripotent cells either pt derived (iPS) or nonpatient derived (Embryonic) are differented in vitro
another option is to reprogram primary cells
regenerative medicine is tricky becayse of
many decisions-has to be pure form, have to have enough, which cell to tranplant, delivery, integratino, rejection, embryonic grafts may be used, some sites better than others
immune rejection is a problem in
adult stem cells
graft can be rejected, requires an identical genotype
somatic cell nuclear transfer
nulceus taken from somatic cell of pt and injected into oocyte of a donor replacing the oocyte nucleus which generates a blastocyte from the hybride oocyte and ES cells isolated
Can insert regulatory factors into fibroblast which
mskes it similar to ES cells
insert Oct3/4, sox2, myc, Klf4
allows them to differentiated into other cells
low yeild and not identical to ES cells
alternatives to human ES cells
induced pluripotent stem cells (iPS)
SCNT
SCNT
somatic cell nucleart transfer
cell is custome made, no tissue rejection, can help us study disesaes, omits embryo step
iPS prospect of introducing patient specific iPS cells for use in treatment
totipotent cells for blastocyst
placenta cell layer forms
then ES cells form (what will be most of the body)
therapeutic for spinal injuries, heart failure, Parkonson;s, DM, arthritis, osteoporotisi, liver failure
controversial because destroying embryos
recombinant DNA can introduce 4 tf into adult stem cells to give them properties of ES cells
recombinant DNA technologies may develop pluripotent stem cells starting from differentiated adult cells by introducing NAnog, Oct4, Sox2, and Lin28.
more research needed on iPS but cool b/c makes pt specific iPS cells and may correct incurable conditions
high ptietnal for teratomas
