Increased GFAP immunoreactivity by astrocytes in response to contact with dorsal root ganglia cells in a 3D culture model

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Abstract

Failure of repair mechanisms in the injured CNS is widely
attributed to the inhibitory environment of the lesion site,
most notably the formation of the glial scar which forms a
physical and physiological barrier to axon regeneration. We developed an in vitro 3D cell culture model to investigate the
response of astrocytes to cells found at the inhibitory
interfaces formed following damage to the spinal cord.
CellTrackerTM labelled dissociated DRGs were seeded onto
astrocyte-populated collagen gels and maintained in culture
for 5 days. Astrocytes near the DRG interface showed marked
GFAP up-regulation and adopted a reactive morphology
which was observed up to 1mm away. Intensity of GFAP
fluorescence at this interface was 3 fold higher than that seen
away from the interface or in controls (astrocyte only gels).
Furthermore, the presence of DRG conditioned medium was
not capable alone of eliciting this response. In conclusion this
model may provide a useful tool for understanding reactive
astrogliosis in response to cells found at inhibitory interfaces
following spinal cord or dorsal root injury. The contact
between astrocytes and satellite cells may be enough to induce
astrocyte reactivity and formation of the gliotic scar, or this
contact may induce the secretion of a soluble factor which is not
released from DRG cultures under physiological conditions.