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Macroglial alterations after isolated optic nerve sheath fenestration in rabbit
Max Villain1, Françoise Sandillon, Agnès Muller
1Unité INSERM 336, Développement, Plasticité et Vieillissement du Système Nerveux Central, Montpellier, France. u336@univ-montp2.fr
Purpose:
To study the modifications undergone by the macroglial cells after meningeal breach of the optic nerve in the rabbit, without optic neuropathy.
Methods:
The optic nerve sheath fenestration technique carried out in humans was adapted to rabbit without axonal injury in the optic nerve. The effects of meningeal fenestration on glial cells were examined by immunocytochemical procedures (day 15) using the antibodies against two astrocyte markers: glial fibrillary acidic protein (GFAP) and vimentin. Proliferation of glial cells was evaluated with single 5-bromodeoxyuridine (BrdU) labeling or double GFAP and BrdU labelings. Qualitative data on glial cells were evaluated with the electron microscope.
Results:
Optic nerve sheath fenestration on healthy adult rabbits resulted in a decrease of volume of the subarachnoid space located at the level of the meningeal scar, with a significant increase of the optic nerve area. The meninges presented a fibrous scar. In the optic nerve parenchyma, astrocytes appeared hypertrophic in the vicinity of the fenestration. The whole nerve contains numerous BrdU-labeled mitotic cells, a number of which double-labeled for both BrdU and GFAP belong to the astrocyte line. There was no loss of optic nerve axons.
Conclusions:
The inflammation produced by the surgical breach of the peri-optic meningeal sheaths induces a significant reactivity, including proliferation of astrocytes in the optic nerve. Reactive astrocytes may interact positively with axons and may modify the extracellular environment in the optic nerve.
Insights
Surgical breach of optic nerve meninges in rabbits causes astrocyte reactivity and proliferation without axonal damage. This inflammation-induced astrocyte response may positively influence optic nerve axons and their environment.
Area of Science:
- Neuroscience
- Ophthalmology
- Cell Biology
Background:
- Optic nerve injury can lead to secondary damage.
- Understanding glial cell responses is crucial for neuroprotection.
Purpose of the Study:
- To investigate macroglial cell modifications following optic nerve meningeal breach in rabbits.
- To assess astrocyte reactivity and proliferation without inducing optic neuropathy.
Main Methods:
- Adapted human optic nerve sheath fenestration technique in rabbits, ensuring no axonal injury.
- Immunocytochemistry using glial fibrillary acidic protein (GFAP) and vimentin antibodies.
- Evaluated glial cell proliferation via 5-bromodeoxyuridine (BrdU) labeling and electron microscopy.
Main Results:
- Meningeal fenestration led to reduced subarachnoid space and increased optic nerve area.
- Hypertrophic astrocytes and numerous BrdU-labeled mitotic cells, including astrocyte lineage cells, were observed.
- No optic nerve axon loss was detected.
Conclusions:
- Surgical breach of optic nerve meninges induces significant astrocyte reactivity and proliferation.
- Reactive astrocytes may play a beneficial role in optic nerve axon health and extracellular environment modulation.