regeneration and repair of the central nervous system stuart bunt dept of anatomy and human biology,...
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Regeneration and repair of the central nervous system
Stuart BuntDept of Anatomy and Human
Biology, UWA
207 Introduction to Human Neuroanatomy
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The problem of CNS regeneration
• Spinal cord damage is a mortal condition (10-15 per million per year UK)
• Damage caused by stroke is permanent
Neurological conditions involving cell loss are irreversible (Alzheimer’s disease, Parkinson’s disease)
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Mortality associated with spinal injury
has only recently fallen
• 2500 BC “an ailment not to be treated”
• WW1 only 10% survived a year- 1% more than 20 years
• 1960s 35% died
• 1983 7.87x normal mortality. 20 yr old can expect to live 30 years
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What factors influence whether a cell regenerates?
External factors
NGF, BDNF
Substrate factors
laminin, In-1
Internal messengerskinases, proteases
Internal genetic state
Environmental factorsmacrophages, hydrogels, glia
receptors
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How can we tackle this problem?• Change the environment
– peripheral nerve graft– ensheathing glia– hydrogels– fetal tissue– proteases– blood substitutes
• BUT only a few fibres regenerate
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• Provide Growth Factors? – NGF only works on peripheral nerves– BDNF?– Genetically engineered cells?
• Improve the substrate?– laminin– osmotic pumps– artificial substrates
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Change the cell?
• Engineer more receptors
• Up-regulate internal messengers
• use different cells?– Fetal cells– Stem cells
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Will mammalian spinal cords make the right connections even
if we do get regeneration?
• No retinotopy in lizard regeneration?
• No retinotopy in regeneration along sciatic nerve?
• Retinal transplants do not form a retinotopic projection?
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What can and can’t regenerate?
• Adult fish can regenerate everything!
• Larval amphibia too, adults slowly?
• Reptiles slowly and without specificity
• Mammalian PNS
• Mammalian olfactory tract
• Mammalian nerves can only sprout abortively
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Are fish different?
• Why study preamniotes?
• Can differences give clues?
• Can we do novel experiments?
• How do their spinal cords regenerate?
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Why study “Lower Vertebrates”?
• They regenerate quickly and are simple to maintain.
• Embryos are readily available
• They have many tracts in common with mammals
• They show many of the growth factors, ECM components and even “collapsins” found in mammals
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Two approaches have been used
• 1. Assuming similar processes act in all species use them as a model system for testing the ability of fibres to regenerate under experimental conditions
• 2. To deliberately look for clues in the differences between the regenerating and non-regenerating species
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How different are they?
• They grow throughout life
• Level of myelin inhibitory factor low in adult animals? (or localised?)
• Glial response to injury different?
• Extracellular environment more condusive to regeneration?
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Are their neurons different?
• Added throughout life• Less need for growth
factors?• Less cell death after
axotomy• Do NOT all regenerate
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Inhibiting factors ARE present in fish CNS?
Regenerating fibres prefer the PNS?
(Bentley and Zottoli 1993)
cut site
Ventral rootFish optic nerve not permissive for adult nerves(Sivron et al 1994)
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Is the balance different ?
L1BNTF
NGF MIF-1
MAGECM
cell death
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What does a regenerated spinal cord look like?
• Which fibres regenerate?
• Do they grow back to their normal tracts?
• Do they find the correct targets?
• Is this process an extension of growth?
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Can Spinal Axons tell Right from Left?
?
R LL R L
R
R L?
?
Cut
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The problem of
order
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Spinal cord in culture
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Direct cell heaters• Work well in closed systems
• Ideal for imaging– as they allow DIC and
Fluorescence concurrently– Small amounts of media– Allow long term culture
Only heat cells
Must use objective heater with
immersion optics
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Closed stage system
Thermocouple
drain
inlet
Contacts for glass heaters
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Phase and Dark Field
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Artificial Substrates
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Saima Majeed
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