Stem cells Flashcards
1
Q
What is the definition of a stem cell?
A
A stem cell is a single cell that has self renewal capacity and potency (can differentiate into many cell types)
2
Q
what three levels of potency are there?
A
Totipotent: have unlimited capability. Can develop to all postembryonic tissues and organs.
Pluripotent: stem cells capable of giving rise to most tissues of an organism.
Multipotent: stem cells that are specialized to give rise to a few particular cell types.
3
Q
what are embryonic stem cells (ES cells)?
A
pluripotent cells that are derived from the inner cell mass of the blastocyst
Capable of developing into any of nearly 200 cell types that make up the body
taken from embryo 4-5 days old
3
Q
what are embryonic stem cells (ES cells)?
A
pluripotent cells that are derived from the inner cell mass of the blastocyst
Capable of developing into any of nearly 200 cell types that make up the body
taken from embryo 4-5 days old
4
Q
what are adult stem cells?
A
A tissue specific stem cell - undifferntiated cell that occurs in a differentiated tissue, renews itself and becomes specialised to yeild all the specialised cell types of the tissue from which it originated - multipotent
5
Q
when did yamanaka and yu first produce iPS cells ?
(ES like cells from human fibroblasts)
A
2006-2007
winning the nobel prize in 2012
6
Q
when did yamanaka and yu first produce iPS cells ?
(ES like cells from human fibroblasts)
A
2006-2007
winning the nobel prize in 2012
7
Q
what are the three types of divisions that stem cells can complete?
A
- Self renewal symmetric cell division: producing two identical stem cells
- Asymmetric cell division: producing one stem cell + one differentiated cell
- Terminal symmetric cell division: giving rise to two differentiated cells
8
Q
what ways can asymmetric stem cell division occur/be induced?
A
- asymmetric localisation of cell polarity regulators
- cell fate determinants can be segregated to the cytoplasm of one daughter cell
- regulated orientation of the mitotic spindle retains only one daughter in the stem cell niche (while the other migrates to another environemnet which induces differentiation)
9
Q
what are hematopoietic stem cells (HSC)?
A
multipotent primitive cells that can develop into all types of blood cells, including myeloid-lineage and lymphoid-lineage cells
starting off as long term-HSCs
10
Q
where can HSCs be found in the body?
A
n several organs, such as peripheral blood (PB), bone marrow (BM), and umbilical cord blood (UCB)
11
Q
where do HSCs originate?
A
in the vascular endothelium
- dorsal aorta, placenta and umbilical cord at birth
12
Q
what are neural stem cells (NSC)?
A
multipotent stem cells that give rise to oligodendrocytes, astrocytes and neurons
(neural stem cells in the brain)
13
Q
where can neural stem cells be found in the developing brain?
A
along the ventricles
14
Q
where can neural stem cells be found in the adult brain?
A
– Subventricular zone
– Subgranular zone of the dentate gyrus (hippocampus)
– Cerebellum
– Optic nerve
– Olfactory bulb
– Spinal chord
15
Q
why are neural stem cells not all equivalent?
A
some are latent and some are active
16
Q
what is the location of NSCs in the subventricular zone of the brain
A
at the border of the ventricle
17
Q
give one marker of adult stem cells
A
GFAP
18
Q
what areas of the rodent brain do neural stem cells give rise to new neurons for and how do they get there?
A
in the rodent olfactory bulb and in the granule layer of the rodent dentate gyrus
form a chain of stem cells
19
Q
how many new neurons are produced in the the olfactory bulb of rats every day?
A
10,000-80,000
1% new neurons every day
20
Q
up to what age are new neurons produced in the olfactoy bulb in humans?
A
up to 18 months
21
Q
what potential ideas are there about the function of new neurons in the olfactory?
A
- ongoing integration of new and different smells
- maximising discrimination of odors
22
Q
how many new neurons are produced in the dentate gyrus of the rat every day?
A
9000
0.1%
23
Q
how many new neurons are produced in the dentate gyrus of a human every day?
A
700-1400
0.2%
24
briefly what is the function of the dentate gyrus?
learning and memory
emotions and affective behaviour
25
what are the agreed upon functions of the new neurons produced in the dentate gyrus?
* pattern separation
* encoding time
* memory resolution
26
what are the proposed functions of new neurons in the dentate gyrus?
* increased memory capacity
* reduce interference between memories
* add information about time to memories
* add spatial separation information
* help memory encoding and retrieval during a critical period
* role in emotional control and affective behaviour
27
what things promote neurogenesis in the adult brain?
* exercise
* learning
* enriched environment
* seizures
* oestrogen
* odours
* calorie restriction
28
what things decrease neurogenesis in the adult brain?
* stress
* age
* inflammation
* alcohol
* lack of sleep
29
what injuries and disease have an effect on neurogenesis?
ischemia, epilepsy, meningitis, neurodegenerative diseases
30
what drugs anad treatments have an effect on neurogenesis?
opiates, antidepressants (prozac), irradiation
31
what are gut stem cells (GSC)?
give rise to progenitors in the gut epithelium
present at the base of the intestinal crypt
mutlipotent
32
what cells do GSCs give rise to?
one progenitor cell line produces paneth cells
the other progenitor gives rise to Goblet cells, endocrine cells, and columnar cells
33
what cell types do hematopoietic stem cells give rise too?
lymphoid cell line: T cell and B cells
Myeloid cell line: erythrocytes, platelets, granulocytes, macrophages
34
what is the stem cell niche?
Microenvironment around stem cells that provides support and signals regulating self-renewal and differentiation
35
what are the three main ways the niche affects the stem cells?
- direct contact
- soluble factors
- intermediate cell
36
what proteins are produced by the LIF signalling pathway?
| (leukemia inhibitory pathway)
SOX2
Nanog
Oct3/4
TEAD2
## Footnote
Binding to receptor results in activation of different pathways that go on to phosphorylate factors resulting in a change in transcription
37
briefly describe the notch signalling pathway?
when Notch is bound by its ligand Delta Jagged it activates it and causes a enzyme to cleave the outer domain. another enzyme then comes along to cleave the innter domain so that it can travevl to the nucelus and activate transcription of a part of the genome
38
briely describe the sonic hedghog signalling pathway
hedghog is secreted by a neighbouring cell and binds to the patch complex. this signalling down stream to Gll which in turn enters the nucelus binds to CBP and activates a number of genes including Wnt and BMP
39
what tissue/cell transplants have been made using stem cells?
- bone marrow for leukemia and chemotherapy
- nerve cells for parkinsons & alzheimers disease
- heart muscle cells for heart disease
- pancreatic islet cells for diabetes
40
what are the current clincal applications for culture pluripotent stem cells?
- identification of drug targets and test potential therapeutics
- toxicity testing
- study cell differentiation to undersand prevention and treatment of birth defects
- tissues/ cells for transplantation
40
what are the current clincal applications for culture pluripotent stem cells?
- identification of drug targets and test potential therapeutics
- toxicity testing
- study cell differentiation to undersand prevention and treatment of birth defects
- tissues/ cells for transplantation
41
what are the sources of adult stem cells?
* Brain
* muscle
* dental pulp
* liver
* skin
* gastrointestinal tract
* pancreas
* amniotic fluid
* umbilical cord
* salivary gland
* tendon
* heart
* cartilgae
* thymus
* adipose tissue
* blood
* cornea
* retina
42
give two ways to extract embryonic stem cells?
* in vitro fertilisation: ES cells collected at the cleavage/ blastocyst stage before implantation
* Somatic cell nuclear transfer: egg cell taken and nuclues removed, isolated donor nuclear material inserted into egg, then left to divide and ES cells are collected
43
what are induced pluripotent stem cells?
| iPSC
derived from skin or blood cells that have been reprogrammed back into an embryonic-like pluripotent state that enables the development of an unlimited source of any type of human cell needed for therapeutic purposes
44
what are two downsides to iPSCs?
- low efficacy
- genomic insults (mutations, insertions/deletions, chromosomal rearrangments)
45
how are induced pluripotent stem cells produced?
1. somatic cells are obtained from an adult organism
2. the reprogramming factors; Oct4, Sox2, Kl4 and c-Myc are introduced into the cultured somatic cells
3. the cells are grown under ES cells conditions. After 2-3 weeks iPS cells emerge
4. these induced pluripotent stem cells may be differentiated into various cell types for regenerative medicine applications
46
give three techniques to get pluripotent stem cells in a dish?
ES cell lines
somatic cell nuclear transfer
iPS cell lines
47
which stem cells dont have the risk of tumour formation
| ES cells from IVF, ES cells from SCNF, iPSC, adult stem cells
adult stem cells
48
what stem cells can produce all cell types?
| ES cells from IVF, ES cells from SCNF, iPSC, adult stem cells
ES cells from IVF
ES cells from SCNF
iPSC,
| not adult stem cells
48
what stem cells can produce all cell types?
| ES cells from IVF, ES cells from SCNF, iPSC, adult stem cells
ES cells from IVF
ES cells from SCNF
iPSC,
| not adult stem cells
49
what stem cell have easy/ large access?
| ES cells from IVF, ES cells from SCNF, iPSC, adult stem cells
ES cells from IVF
50
which type of stem cells arent genetically matched to the patient?
| ES cells from IVF, ES cells from SCNF, iPSC, adult stem cells
ES cells from IVF
51
which stem cells are likely to contain DNA abnormalities?
| ES cells from IVF, ES cells from SCNF, iPSC, adult stem cells
ES cells from SCNF,
iPSC,
adult stem cells
52
what is the proposed new definition of stem cell therapy?
stem cell therapy is a type of cell therapy in which therapeutic efficacy is exclusively attributed to the potency (function) of donor stem cells, presented in any quantity or purity
53
what problems are there with defining stem cell therapy?
* we can not rely just on the presence of stem cells in transplanted cell suspension/ tissue (ex: blood transfusion)
* we can not rely purely on degree of stem cell enrichment (purification) in transplanted cell suspension/ tissue (ex: HSC transplantation in leukemia with bone marrow transplant)
* we should solely rely on anticipated mechanism of therapeutic action, which should be exclusively attributed to stem cells, but not to progenitor or mature cells
54
whats the difference between allogenic and autologous bone marrow transplant?
allogenic - transplant of a donors bone marrow
autologous - reinfusion of patients own bone marrow (after freezing and chemo)
55
what are the differences between autologous and allogenic bone marrow transplants
* tissue matching is required in allogenic
* rejection and graft vs host shown by allogenic
* engraftment is faster in autologous compared to allogenic
* immune recognition is faster in autologous
* risk of disease only possible with allogenic
56
what are the steps to autologous stem cell therapy?
1. Collection - stem cells are collected from the patients bone marrow or blood
2. Processing - blood or bone marrow is processed in the lab to purify and concentrate the stem cells
3. Cryopreservation - blood or bone marrow is frozen to preserve it
4. Chemotherapy - high dose chemo and/or radiation therapy is given to the patient
5. Reinfusion - thawed stem cells are reinfused into the patients
57
how is stem cell therapy combined with gene therapy?
DIrect delivery: the therapeutic gene is packaged into a dilvery vehicle such as a retrovirus and injected into the patient
Cell based delivery: the therapeutic gene is packaged into a delivery vehicle such as a retrovirus and introduced into the adult stem cells that were isolated and propagated in the lab. The genetically modified cells are reintroduced into the patient
58
how is personalsied medicine using iPS cells carried out?
collect skin cells
reprogram into ES like iPS cells
correct mutation in the genetically identical iPS cells
genetically corrected iPS cell differentiate into blood stem cells and reinfused
59
what is the advantage and disadvantage o using gene therapy as a mode of delivery of stem cells?
advantages: ability to directly reprogram stem cells in situ through integration and expression of certain genes
disadvantages: highly dependent on development of safe and efficient delivery vectors that can also cross the blood brain barrier.
Precise control of gene expression might be a challenge
60
what are the advantages and disadvantages of proteins as a mode of delivery for stem cells?
advantages: direct and transient delivery of the therapeutic protein to the stem cell population
more ocntrol over the course of administration
disadvantages: blood brain barrier might prevent systemic administration of certain proteins , which might require more invasive techniques
even if systemic administration is possible there might be adverse side effects in other parts of the body
61
what are the advantages and disadvantages of small molecules as a mode of delivery for stem cells?
advantages: high throughput screening easily applied to identify groups of synthetic small molecules capable of modulating stem cell behaviour is desired
can be made to be highly specialised for targeting
high purity achieved through synthetic chemistry
many small molecules are capable of passing through the blood brain barrier
disadvantages:
adverse side effects of systemic delivery
62
give four strategies for restoring stem cell functions
(A) Stem cells, progenitors and daughter cells are affected by a genetic modification. Somatic cells located close to the niche are reprogrammed by factors into de novo stem cells.
(B) Stem cells, progenitors and daughter cells contain an epigenetic modification. Progenitors or differentiated cells can be dedifferentiated into stem cells, and the detrimental epigenetic marks would be erased.
(C) The stem cell transcriptional network is missing specific transcription factors that would be delivered specifically to the stem cells.
(D) Malfunction of the stem cells is due to an aged niche, which would be the target for the in vivo reprogramming.
63
after glial degeneration how is it rebuilt with stem cells
after demyelinating diseases causes glial degeneration, specific phenotype replacement is provided by the stem cells, replacing the specific interactions at cell level
64
give three types of neuronal degeneration that can be repaired by stem cells
Paracrine systems
Selective degeneration
Global degeneration
65
what is required for repair after neuronal degeneration of paracrine system?
Phenotype replacement
no pattern repair
66
give an example of a condition that would cause neuronal degeneration of paracrine systems
Parkinsons
67
give examples of conditions that woudl cause selective neuronal degeneration
ALS
Huntingtons
Ataxia
68
give examples of conditions that would cause global neuronal degeneration
trauma
stroke
69
what is required to repair selective neuronal degeneration?
replacement of a single phenotype
pattern repair: re-establishment of afferent-efferent connections
70
what is required for repair of global neuronal degeneration?
Replacment of multiple phenotypes
Pattern repair: local circuites (graft-graft) and long distance connections (graft-host)
71
what is parkinson disease?
| description?
symptoms?
a neurodegenerative movement disorder - causes degeneration of the neurons in the substantia nigra (which releases dopamine in the striatum) reducing dopamine release
affects 10 million worldwide
causes :
* tremor in the hands or feet
* trouble with walking
* muscle rigidity
* a slowing of physical movement up to a loss
72
what are the available treatments for Parkinson?
| give one issue of each
**Pharmacological/chemical therapy**: loses its efficacy in several years, side effects
**Deep brain stimulation**: variable effect: reduce motor symptoms, but serious adverse events are often associated with the surgical procedure
**Neural protection with trophic factors**: side effects
**Cell therapy**: with human foetal dopaminergic neurons (cells from several foetuses needed to treat one patient), inconsistent results due to variable sources of cells
73
what are the benefits of transplant of human embryonic mesencephlon to treat parkinsons?
* reverse some motor symptoms
* lower doses of medication (or discontinuation)
74
what are the limitations of transplantation of human embryonic mesencephalon for parkinsons
* immune rejection
* overgrowth, tumour formation
* developmental stage of graft
* 90% of cells die during transplant
* purity (no contamination with proliferating non-neural cells)
* A9 substancia nigra phenotype
* durability of the effects
* patient selection (only classical Parkinson, early in disease)
* graft-induced dyskinesia
* pathogenetic process can affect transplanted neurons
75
what ways can fibroblast be directly converted to neurons
* Fibroblasts + ASCL1, BRN2A, MYT1L neurons (Pfisterer et al 2011; Torper et al 2013)
* Human fibroblasts + SOX2 NSCs, able to differentiate into neurons, astrocytes, and oligodendroglia (Ring et al 2012)
* Human fibroblasts +miR 9/9*-124 neurons
+CTIP2, Dlx1/2, Myt1L medium spiny neurons (Victor et al 2014)
* Human fibroblasts with p53 deletion neurons (Zhou 2014)
* Mouse Embryonic fibroblasts +Brn4, Sox2, Klf4, c-Myc NSCs, transplanted in mouse model of PD rescued DA neurons, motor performance (Choi et al 2017)
76
what needs to be added to cord blood stem cells to convert them to neurons?
+ Sox2, c-myc
77
what are the challenges of direct conversion of differentiated cells to neurons
* ability to improve the reprogramming/direct conversion
* combine efficient differentiation protocols with the precise modification of specific genome sequences
* no proliferation step
78
what are the juridical and ethical issues to do with stem cells?
* what sources of stem cells should be used and to what extent?
* sources of embryonic stem cells?
* should stem cell research be restricted to certain areas of research with certain levels of benefits?
* what are the rights of those who donate materials for stem cell research?
* what happens once a stem cell line has been established?
* should cross species experiments be allowed?
