Cell differentiation/Stem Cells Flashcards
stem cell characteristic
self renewing, undiffernentaited, can be tot, pleura, multi, olive, or unipotent, can be undimmed for special functions
cancer-divide slowly, multiple drug resistance, umbridled growth possible
adult vs embryonic stem cells?
adult
- need to be de-differentiated to induce pluripotent
- in partiuular regions, generally differentiated
embryoinic-ICM and pluripotent
how are stem cells indentifiend, isolated, and maintained
isolated-cultured-irradiated mouse fibroblast-grotth/support
idetifed-antibodies to markers CD3R on HSCs-flourensnce
Maintained -LIF-blocks MAPK pathway-prevents differentiation
stem cells in regen med
tissue repair
organ restoration
cancer stem cells
self renewal-can result in relapse of cancer if not destroyed
stem cell properties
unspecialized and can self renew
can be induced to differentiate into cells with special functions (differentiated cell)
self renewel
assymetric division=stead state conditions-makes differentiated and undifferenteatid cells
-undif stays in niche
Symmetric divisoin=when stem cells must expand-during dev or during injury
regulation of stem cell self renewel
cell intrinsic
- Tfs negatively rg expression of diffenrtiiton promoting genes
- dna binding protein (Ronin) supresses trx of differnation-inducing genes
cell extrinsic
-BMp and other stuff block MAPK pathway
stem cell niche
Chemical and mechanical environemnt
-microenvironemnt
Tissue injury results in respecification of niche-cancer can cause over differentiation
intesttinal crypty
1:1 ratio between stem and panted cells-need panted cells to divide
Adult stem cells
Can self renew and differentiate if not differentiated
IPS stem cells-pluripotent stem cells artificially derived from a non-pluripotent
maintain and repair tissue which they find-not pluripotent
Embryonic
Undifferniated from 5 day preimplantation embryo that is pluripotent
cancer stem cells (2 types)
drive tumorigenesis and rise to differtitted progeny
2 types of division
stochasttic-results in two stem cells or two daughter cells
Hierachical division-normal stem cell division
differentated defintioon
acquired specialized structure and function
can be cancer of cells that look just like cells that should normally be three
undifferentiated defintion
cell that has not yet acquired a special structure or function
-immature cancer is primitive and does not look like cells in tissue from which it arose
dedifferentiation
process by which partially or terminally differentiated cell reverts to an earlier dev stage
-holy grail of stem cell research
potency definition and 3 types +example
potential to differentiate
multi-access differentiate into number of cells that are related-hemopoeisis
oligopoent-can differentate into a few spefic ecells-lymphoid
unipotent-can only produce one type of cell-but have self renewal property-muscle cells
-differ from normal cells-self renewel
totipotent vs pluripotent
totipotent-stem cells that are produced from fusion of egg and sperm
-give rise to embryonic and extra embryonic tissues
pluripotent-totipotent cells that can differentiate into cells from any of three germ layers-ectoderm, endoderm, or mesoderm
zygote, embryo potency
zygote-totipotent
embryo-pluripotent (inner cell mass cells)
two type of stem cells in bone marrow
hematopoetic (blood)and stomal (bone, carlidge, fat, connective tissue)
Embryonic stem cells
aka ICM
obtained from 4-5 day old blastocyst
can be cultured in vitro under conditions preventing them from differentiating (need to stop them from differentiating)
-can be cultured to make a particular phenotype
How are stem cells cultured in vitro
Plate ICM cells on layer of fibroblast feeder cells
- these bottom cells are inactivated (irradiated) and provide source of growth and attachment factors for ES cells
- produces ground substance and fibers of ECm
plate ICM cells onto tissue culture medium containing factors (LIF) that inhibit differentiation
-LIF binds to hetermdimer which activates JAK/STAT signaling-blocks MAPK pathway that would result in differentiation
JAK/STAT and MAPK pathway and LIF
Lif binds to receptor that activates JAK/STAT which inhibits MAPK pathway-stops differentiation
How to identify stem cells
use cell surface markers directed against specific membrane receptors on the stem cells
- or flow cytometry for HSC using common markers
- analyize 10000s of cells, ells with fluorescent fingerprint-flicked into side tube
Common markers for HSC
hemapoetic stem cell
CD34 and Ckit
FACS
most common way to isolate stem cells
- flow cytometry
- analyize 10000s of cells, cells with fluorescent fingerprint-flicked into side tube
Diffeernation
process where cell becomes more specialized
differntation dramatically changes cells shape, size, etc.
changes are largely due to highly controlled mods in gene expresssion
How to stimulate cells to differentiate 3
changing chemical comp of culture
alter surface of dish (mechanical comp)
modify cells by introducing genes
How to maintain differentiated state (4 ways)
gene expression must be maintained
- TF who se gene is activated can bind to enhancer of own gene
- synthesize proteins to act on chromatin to leave gene accessible
- single molecule-cell can make both the molecule and its receptor
- Cells can interact with neighboring cells-stimulate each other to keep differentiated
Regenerative medicine
Use stem cells to repair or replace damaged tissues
- replace damaged tissues and organs
- figure out how
mouse with human ear
nude mouse (no immune system)
- stem cells from embryonic
- probably hard to put back with human immune system
Transplant stem cell-need these things
proliferate extensilvey and make sufficienct quantities of cells
differentiate into desired cell types
survive after transplant
function properly
avoid huryting recipient
generate tisseust aht will not be rejected
how to get human pluripotent stem cells (5)
- from morula stage f embryo
- from ICM of blastocyst
- from germ cells of fetus
- from adult (only one without moral issues)
- somatic cell nuclear transfer (creating ovum with donor nucleus)
IPS (indueced plurpotent stem cells) + important things about this type of stem cell
start of as adult, repgrom back (using nuclear transfer/cell/fusiongenetic reprogramming)
- CAN BE PATEINT MATCHED
- need 4 out of many candicacn genes to revert it back
challgenges to reprogramming
low effecny
genomic insertion
tumors
incomplete reprogrammng
alternative approaches to reprogramming
chemicals, alternative vectors (plasmids instead of retrovirus), microRNAs, stimulus triggered acquisition of pluripotency (did not work…)
iPS medical research
test drug on stem cells, create organs, repair tissues
Cancer cell theories new vs old
old-all cells are equally tumorgeneic and cancer is prliferative (too many cells reproducing)
new-cancer stem cells-properties of normal stem cells especially self-renewal and multi potency
- upreulation is due to disruption in reg system mech in stem cell renewal
- cancer is a stem cell disorder-not proliferation
CSCs imprtant facts (4)
likely causes relapses and metastasis
- self renewal strong-when attack, make more of stem cell during attack of differentiated cells
- asymmetric division
- divide slowly-plenty of time to repair radio/chemo damage
- multiple drug resistance transporters on cell surface
- remains in low frequency tho (i think this is good)
- unbridlged cell growth mutation-population that expressed genes from drug resistance and antiapop mechs will render chemo ineffective
chemo attacks
bulk of cells-should try to attack cancer stem cells
