The Journal of Neuroscience, May 1, 2003, 23(9):3715
Cytoskeletal and Morphological Alterations Underlying Axonal
Sprouting after Localized Transection of Cortical Neuron Axons
In Vitro
Jyoti A.
Chuckowree and
James C.
Vickers
Discipline of Pathology, Faculty of Health Sciences, University of
Tasmania, Hobart, Tasmania, 7000, Australia
We examined the cytoskeletal dynamics that characterize neurite
sprouting after axonal injury to cortical neurons maintained in culture
for several weeks and compared these with initial neurite development.
Cultured neocortical neurons, derived from embryonic day 18 rats, were examined at 3 d in vitro (DIV) and at
various time points after axotomy at 21 DIV. The postinjury neuritic
response was highly dynamic, progressing through an initial phase of
retraction, followed by substantial axonal sprouting within 4-6 hr.
Postinjury sprouts were motile and slender with expanded growth
cone-like end structures. Microtubule markers were localized to sprout
shafts and the proximal regions of putative growth cones and
filamentous actin was distributed throughout growth cones, whereas
neurofilament proteins were restricted to sprout shafts. A similar
distribution of cytoskeletal proteins was present in developing
neurites at 3 DIV. Exposure of developing and mature, injured cultures
to the microtubule stabilizing agent taxol (10 µg/ml) caused growth inhibition, process distension, the transformation of growth cones into
bulbous structures, and abnormal neurite directionality. Microtubule
and neurofilament segregation occurred after taxol exposure in
developing neurites and postinjury sprouts. Exposure to the microtubule
destabilizing agent nocodazole (100 µg/ml) resulted in substantial
morphological alteration of developing neurons and inhibited neurite
growth and postinjury axonal sprouting. Our results indicate that the
axons of cortical neurons have an intrinsic ability to sprout after
transection, and similar cytoskeletal dynamics underlie neurite
development and postinjury axonal sprouting.
Key words:
Alzheimer's disease; axonal sprouting; axonal
transection;
III-tubulin; brain trauma; cortical neuron culture; cytoskeleton; growth cone; microtubules; neurite development; posttraumatic epilepsy; neurofilament; tau; taxol
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