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Hello my name is
Michael Sofroniew from
UCLA. Welcome to
this Henry Stewart
Talk on Astrocyte Reactivity.
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Astrocytes are a main cell
type in the brain and
spinal cord where
they constitute
about 30-40% of the cells.
Astrocytes tile the entire
central nervous system
which we'll refer to as the CNS.
The image shows this tiling in
the mouse hippocampus
and cerebral cortex.
White dots represent
astrocyte nuclei
selectively stained for the
transcription factor Sox9
and shows that they are
evenly spaced throughout the
tissue. The green stain
is for GFAP which is
visible in the main
astrocyte branches in
the hippocampus but GFAP is not
detectably expressed by
cortical astrocytes
in healthy tissue.
Astrocytes are highly branched
cells and their branches
interact with multiple other
cell types, in particular
with neurons and synapses
where astrocytes contribute
many functions that
are essential for
maintaining and influencing
synapse function.
As shown in the schematic on
the right these functions
include taking up and
recycling neurotransmitters and
maintaining potassium
homeostasis.
Astrocytes also contact
blood vessels and
help to regulate
blood flow and
interstitial fluid levels
and lymphatic flow.
In addition, astrocytes form
an important border around
the entire surface of the brain
and spinal cord that separates
neural tissue from the non-neural
tissue of the meninges.
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In addition to
their functions in
the healthy central nervous
system astrocytes respond
to all forms of injury
and disease with
changes that are referred
to as astrocyte reactivity.
These responses include
many variable changes
in gene expression and protein
expression as well as changes in
cell structure and potentially
also cell proliferation.
In histological tissue
sections as seen in
the images on this slide,
increased staining
for the protein GFAP is
a prototypical sign of
astrocyte reactivity.
This slide shows examples
of astrocyte changes in
various human disorders or
mouse models including
stroke, traumatic injury,
neurodegenerative diseases like
Alzheimer's disease, tumors,
autoimmune inflammatory diseases
like multiple sclerosis,
and their models and infections.
