Stem Cells Flashcards
stem cells
A primitive cell; can either self-renew or give rise to more specialized cell types • Single stem cells differentiate into multiple, functional cell types • Stem cells functionally reconstitute a given tissue in vivo
characteristics of stem cells
– Not terminally differentiated
– Can divide without limit
– Undergo slow division
– When divide gives rise to 1 cell with stem cell characteristics and the
other with the ability to be differentiated
potency
proliferative potential
totipotency
Ability to give rise to all cells of an organism, including embryonic and extraembryonic tissues (cells which support embryonic development)
ex of totipotency
zygote
pluripotency
Ability to give rise to all
cells of the embryo and subsequently
adult tissues.
ex of pluripotency
(embryonic stem cells)
multipotency
Ability to give rise to
different cell types of a given lineage.
ex of multipotency
adult stem cells
founder stem cells
• 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 large final structures
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 • Programmed to have limited number of divisions-> finite -part of strategy for growth control -committed
divisional asymmetry
asymmetric division may create 2 cells, one with stem cell characteristics and another with factors that give it the ability to differentiate
environmental asymmetry
Division makes 2 identical cells but
environment may influence/alter 1 cell
immortal strand hypothesis
• Some tissues’ stem cells selectively retain original DNA This daughter cell will retain stem cell characteristics • Original strand of DNA preserved in stem cells from generation to generation • Second cell gets the newly synthesized strand
embryonic stem cells
-Derived from the blastocyst stage of embryo
• Capable of proliferating indefinitely in culture
• Unrestricted developmental potential
• When put back in blastocyst they can integrate well with the embryo
• Develop into different cell types
*can become tumor
what can give rise to teratoma
ES cells
ES cell therapies
-successful treatment of animal models of disease
what TF are essential for establishment and maintenance of pluripotent stem cells
(Nanog, Oct4, Sox2 and FoxD3)
what are GF found in pluripotent cells
Cripto and GDF-3
what is required for early stages of pluripotent cell differentiation
GCNF
adult stem cells
Found in tissues; responds to demands of
growth/repair
-Strictly imposed by molecular restraints on gene
expression
-Restricted capacity and growth potential
• Harvested cells retain properties of the
original tissue type; have memory of its
developmental history
Hematopoietic and Stromal Stem Cell
• Both come from bone
marrow
• Differ in what they can be
differentiated as
HSC
blood components
MSCS
connective tissues, tissues
adult stem cell therapies
– Bone marrow derived mesenchymal stem cells
(BMSCs): transplant
– Adipose derived mesenchymal stem cells (AMSCs):
liposuction
what is as serious problem in adult stem cells
immune rejection
somatic nuclear transfer
nucleus taken from somatic cell of
patient and injected into oocyte of a donor replacing the ooctye
nucleus
– Blastocyst generated from this hybrid oocyte and ES cells isolated
what are key gene regulatory proteins that determine ES cell character
Oct3/4, Sox2, Myc and KIf4.
somatic cell nuclear transfer (SCNT)
– Combines cloning methods with embryonic stem cell technology
– Produces cells which are custom made for patient
– Solves tissue rejection problem as cells express the patient’s genes
– ES cells from patients with certain diseases; study disease development and
develop drugs
– Research has enabled reprogramming of adult cells while omitting embryo step
induced pluripotent stem cells (ips cells)
- reprogram differentiated adult cells back to plurpotency
- generates patient specific ips cells
what TF does ips cells use
oct 4, sox 2, nanog, lin28
what is a drawback to ips
very high potential for teratoma formation
somatic cell nuclear transfer
1) remove egg nucleus
2) add somatic cell nucleus of recipient
3) stimulate cell division process
4) extract ICM from blastocyst
5) culture pluripotent embryonic stem cells
Ethical restrictions with SCNT
1) stop at fusion: restricts therapeutic application
2) stop at blastocysts stage: restricts cloning but therapeutic research continues
challenges of SCNT in disease treatment
– Inefficient (may need hundreds of oocytes) – Technically demanding - needs to be available in many or all hospitals
source of oocytes in SCNT
Self,
Mother, Relative, Egg bank
