Flashcards in Stem cells and neurogenesis Deck (35):
production of neurones and all neuronal helper cells
What type of stem cells do blastocysts contain ?
pluripotent stem cells - can become any type of stem cells
What are the other types of stem cells?
- can isolated pluripotent stem cells and this produces cultured pluripotent stem cells
- hematopoietic stem cells which go on to form blood cells
- neural stem cells (for production of neurones, oligodendrocytes and astrocytes) and tissue specific stem cells
- mesenchymal cells
What can increase neurogenesis and what can reduce it ?
more exercise and better diet can increase it and a lack of sleep can reduce it
Where do you get stem cells from to use for recovery ?
take stem cells from the damaged spinal cord and in vitro you try and differentiate them into the cells you want
can take stem cells from embryos but there are many ethical issues surrounding this
however we have stem cells in the spinal cord and this could be a useful method of obtaining them
What is the purpose of stem cell therapy?
you want to replace the lost neurones and oligodendrocytes
- also know hat astrocytes go on to make a glial scar to try and act as a protectant but actually it prevents regeneration occurring
What did transplantations of embryonic neural precursors do ?
improved motor function
- grafts show good survival and migration
used embryo-neural precursors or mesenchymal stem cells
- improved serotonin sprouting
behavioural testing showed good recovery such as improved grip test but adult mesenchymal cells were not as effective
- these benefits were still present after 42 days
What did adult mesenchymal cells do?
they did not express neuronal markers and so they created a permissive environment for recovery to occur
When were the mesenchymal stem cells or embryonic neural precursor cells transplanted?
2 weeks post injury and therefore this was an appropriate model
What do neural stem cell grafts differentiate into ?
differentiate into catecholaminergic neurones and innervate the SPNs
- can differentiate into serotonergic neurones when transplanted into the SC
also can differentiate into cholinergic neurones
What experiment was carried out to induce an autonomic effect to test the neural stem cell graft and what was the outcome?
colorectal distention was induced to increase BP to induce an autonomic response
- the neural stem cell graft reduced the BP indicating a reduction in autonomic dysreflexia
What was the experiment carried out with olfactory ensheathing cells and what was the outcome?
a man had a clean stab wound to his spine causing him to lose the ability to walk
- they took out olfactory bulb and looked at olfactory ensheathing cells and used them as treatment
- schwann cells bridge and olfactory ensheathing cells helped to make a functional recovery which was significant
paralysed man was able to walk again
Why does transplanting cells have limitations?
allodynia = inappropriate nociceptive responses
- transplanting cells in the hope they will be integrated, has major issues, it involves putting the patient through another operation and patients can end up suffering allodynia that is so bad that they cant even abide touch - could be due to inappropriate innervation
What are the stem cells within the SC region ?
cerebrospinal fluid contacting cells (CSFcCs) - unsure of their role but they may be involved in neurogenesis
preserved throughout species
What are the other importance cells within the SC region?
ependymal cells which surround the central canal and have the CSFcCs distributed in between them
What do ependymal cells do ?
they are multipoint and they differentiate into oligodendrocytes and astrocytes after injury
In an uninjured SC which cells can renew themselves?
What cells renew themselves in an injured SC?
oligodendrocytes and glial cells renew themselves and increase
ependymal cells increase in number and could differentiate into oligodendrocytes and astrocytes
What was seen in FoxJ1 rasless mice?
the mice all originally had the same of initial injury but the cavities formed in the FoxJ1 rasless mice varied hugely
- the glial scar is NOT formed as well
- it didn't form because it needed ependymal cells for this to occur - the astrocytes can also proliferate and contribute to the glial scar
What happens to endogenous stem cells after spinal cord injury in humans?
they are unregulated
- look for nestin +ve cells
- +ve correlation between time after injury and number of nestin +ve cells - as time increases response gets greater
What does nestin label and what differences were seen between patients?
labels neural progenitor cells and looked at their levels within the ependymal region
- amount of nestin +ve ependymal cells was less in those patients that didn't survive compared to those that did but it wasn't significant
What does eliminating endogeneous stem cell proliferation do ?
it is detrimental to sc repair
What increases due to modulation of the alpha-7 containing nicotinic receptor in cultured sc slices?
it increase ependymal cell proliferation and these become oligodendrocytes
How do you promote proliferation of ependymal stem cells?
give a nicotinic receptor agonist
- targetted alpha7 and it was a positive allosteric modulator
- important for enhancing neurogenesis
By increasing the number of receptors the amount of proliferation is increased, what cells are mainly increased?
boost the number of proliferating cells, majority being oligodendrocytes
What does modulation of nicotinic receptors in vivo do ?
it increases central canal cell proliferation
How was modulation of nicotinic receptors in vivo carried out?
injected drug intraperitoneally - colocalised with SOX2
- increases in both thoracic and lumbar regions but more substantially in the lumbar regions
What are some of the questions associated with ALS and stem cell therapy?
if we lose mn in ALS, they can be replaced with stem cells
where would the cells be put in in the sc
What happened when human iPSC were trasnplanted into ALS mouse models ?
it boosteed lifespan
- human iPS cells were differentiated into glial rich neural progenitors
- then these were transplanted into ALS mice after onset
- it improves motor response and prolongs lifespan, increases neurotrophic factors and activates AKT signals and astroglial differentiation in SC
When glial rich neural progenitors were transplanted into ALS mice models, what did most of them become?
most became astrocytes
although motor scores improved the scores were actually that different to controls
How was human iPSC translated through to humans?
- multiple injection sites since all motoneurons are affected, requires hours of surgery with exposure of the sc so its very invasive
What is the story of Ted Harada ?
stem cell trial patient
- before trial he had a steady decline in strength and muscle control thats typical of the disease
- after receiving infusions of neural stem cells in his spine he was able to get rid of his can and walk on his own
- grip strength in his hands had doubled
he isn't cured but his deterioration is greatly reduced
BUT OTHERS HAVE NOT DEMONSTRATED THE SAME IMPROVEMENTS
What is reasearch trying to determine about stem cells in spinal cord ?
endogeneous stem cell pop in spinal cord doesn't become neurones like in the brain and therefore they want to determine how to drive them down neuronal line instead of oligodendrocyte line for example
How long are grafts maintained?
after transplantation they are maintained up to 2.5 years