Stem cells and regenerative medicine Flashcards
(42 cards)
Are stem cells capable of self-renewal?
Yes by asymmetric or symmetric cell division - but I believe that as stem cells lose potency, some may lose the ability to self-renew
Name the 3 main sources of stem cells
Embryonic stem cells (ESCs) (pluripotent)
Adult stem cells (ASCs) - rare (multipotent)
Induced pluripotent stem cells (iPSCs)
What is the function of stem cells?
- Can differentiate into many different cell types
- capable of self-renewal via cell
division - provide new cells as an organism grows
- can replace cells that are
damaged/lost
Describe what we get ESCs from and their potency
Pluripotent (all types of cells)
Derived from embryos at the
blastocyst stage before implantation when the embryo is just a few days old, the stem cells reside in the inner cell mass, which will eventually give rise to the whole embryo in vivo culture, these cells can proliferate via multiple round of cell division before differentiating,
-Can give rise to all embryonic germline layers: ectoderm, mesoderm and endoderm
What does the ectoderm vs mesoderm proliferate into eventually?
ectoderm - neural and epithelial and sensory
mesoderm - skeletal muscle, blood vessels, cardiac muscle
endoderm - organs
Name the factors that can allow un-differentiation and so formation of iPSCs
OCT4
SOX2
KLF4
Myc
What can we use CRISPR for in the process of iPSC formation?
Repairing any pathological DNA mutations before allowing iPSCs to differentiate and then giving them to the patient
Describe the composition of a stem cell niche - so the signals involved
Supporting extracellular matrix in a supportive microenvironment.
-Has secreted cell signals (growth factors, cytokines etc.),
-physical parameters (shear stress, tissue stiffness and topography)
-environmental signals (metabolites, hypoxia, inflammation etc.)
Name the functions of stem cell niches
Regulate (dictate) stem cell fate (differentiation)
Why is there a lower risk of tumour formation in adult stem cells and iPSCs than in embryonic stem cells?
As ESCs have the highest growth potential, then iPSCs, then ASCs
Explain why ESCs have a higher risk of rejection in the patient
ASCs and iPSCs are usually taken from the host and so have a low risk of rejection, but ESCs are not taken from the host and so are genetically different
Describe the function of c-Myc
C-Myc is part of the yamananka cocktail and it relaxes chromatin structure - this allows OCT3/4 to access its genes
- from a later lecture they tell us that Myc is an oncogene (I think)
Compare the mutation rate/stability in the 3 different stem cell types
Embryonic stem cells have a low genetic mutation rate and high genetic stability - ASCs and iPSCS are less genetically stable
Describe the function of SOX2 and KLF4
Also co-operate with OCT3/4 to activate target genes
So explain how these TFs will undifferentiate the cell to make an iPSC
They will cause activation of genes that in turn code for TFs - this will ‘establish the pluripotent transcription factor network’. Results in the activation of the epigenetic processes (more open chromatin) that is in a pluripotent cell epigenome
What is a reporter gene and its use?
This is a gene that can be inserted into a stem cell to then track it in vivo (to study where the stem cells go and how they behave once they are back within the body of the model)- for example, this could be a fluorescent gene used in imaging
is non-invasive
Explain what it is that we try to do with stem cell therapies for CV disease
If you survive a heart attack (70% of people do) then you are likely to suffer from heart failure due to loss of cardiac myocytes as well as fibrosis and scarring - so we aim to replace lost cardiac muscle as well as improve blood supply with stem cells
stem cell therapies may also be able to treat cardiac myopathies or conduction defects
Describe how cardiac regeneration differs in different animal models
Zebrafish, some reptiles and neonatal mice can regenerate very large parts of the heart.
Why is improving neovascularisation after cardiac damage particularly important?
As improved circulation to injured area allows for paracrine effects which promotes endogenous cardiac stem cells
Explain how cardiac regeneration occurs in these animals
This is done by re-expression of developmental genes early after the injury such as WT1 and RILDH2 - this is particularly seen in the epicardium of the heart and is known as reactivation of the epicardium
As well as activation of the epicardium, there is activation of the endocardium, cardiomyocyte undifferentiation and formation of a fibrin clot that then degrades as cardiomyocytes proliferate and regenerate the heart
Describe the function of the epicardium in the process of cardiac regeneration
Provides cells and signals that promote cardiomyocyte proliferation
How is the fibrin clot different in cardiac regeneration in larger animals such as mammals?
The fibrin clot does NOT resolve, but instead remodels to form a fibrin scar which effects cardiac function
Describe the differences in cardiac regeneration in neonatal mice vs adult mice: immune components, revascularisation and cardiomyocyte proliferation
Infiltration of the injury by embryonic macrophages. There is also an increase in vascularisation and increased cardiomyocyte proliferation. In adult mice, there is infiltration by monocyte derived macrophages, limited revascularisation and NO cardiomyocyte proliferation
Describe the role of the lymphatic system in cardiac injury normally and what we can do to improve this
In a normal response, the lymphatic system would not clear excess tissue fluid and inflammatory immune cells enough and so there would be oedema and inflammation which causes poor cardiac repair and function but if we stimulate it with a modified IGF C there is increased lymphatic response and there is less oedema and inflammation
