Methods for Experimental Manipulations after Optic Nerve Transection in the Mammalian CNS
Summary
Optic Nerve transection is a widely used model of adult CNS injury. This model is ideal for performing a number of experimental manipulations that target the retina globally or directly target the injured neuronal population of retinal ganglion cells.
Abstract
Retinal ganglion cells (RGCs) are CNS neurons that output visual information from the retina to the brain, via the optic nerve. The optic nerve can be accessed within the orbit of the eye and completely transected (axotomized), cutting the axons of the entire RGC population. Optic nerve transection is a reproducible model of apoptotic neuronal cell death in the adult CNS 1-4. This model is particularly attractive because the vitreous chamber of the eye acts as a capsule for drug delivery to the retina, permitting experimental manipulations via intraocular injections. The diffusion of chemicals through the vitreous fluid ensures that they act upon the entire RGC population. Viral vectors, plasmids or short interfering RNAs (siRNAs) can also be delivered to the vitreous chamber in order to infect or transfect retinal cells 5-12. The high tropism of Adeno-Associated Virus (AAV) vectors is beneficial to target RGCs, with an infection rate approaching 90% of cells near the injection site 6, 7, 13-15. Moreover, RGCs can be selectively transfected by applying siRNAs, plasmids, or viral vectors to the cut end of the optic nerve 16-19 or injecting vectors into their target the superior colliculus 10. This allows researchers to study apoptotic mechanisms in the injured neuronal population without confounding effects on other bystander neurons or surrounding glia. RGC apoptosis has a characteristic time-course whereby cell death is delayed 3-4 days postaxotomy, after which the cells rapidly degenerate. This provides a window for experimental manipulations directed against pathways involved in apoptosis. Manipulations that directly target RGCs from the transected optic nerve stump are performed at the time of axotomy, immediately after cutting the nerve. In contrast, when substances are delivered via an intraocular route, they can be injected prior to surgery or within the first 3 days after surgery, preceding the initiation of apoptosis in axotomized RGCs. In the present article, we demonstrate several methods for experimental manipulations after optic nerve transection.
Protocol
Discussion
Optic nerve transection is a highly reproducible model of adult CNS neuron apoptosis. The experimental manipulations demonstrated in this manuscript permit the study of the mechanisms of RGC apoptosis after injury.
Intraocular injections are useful for global targeting of the retina. This procedure requires some practice, as it is critical not to injure the lens with the tip of the glass pipette. Lens damage has been shown to cause the release of growth factors, altering cell survival and rege…
Divulgazioni
The authors have nothing to disclose.
Acknowledgements
PDK is supported by a CIHR operating grant (MOP 86523)
Materials
| Material Name | Tipo | Company | Catalogue Number | Comment |
|---|---|---|---|---|
| Stereotaxic Frame | Stoelting, Kopf, WPI | |||
| Rat Gas Mask | Stoelting, Kopf, WPI | |||
| Anesthesia System | VetEquip | 901806 | ||
| Isoflurane (PrAErrane) | Baxter Corp | DIN 02225875 | ||
| Surgical Microscope | WPI, Zeiss, Leica | |||
| Alcaine Eye Drops | Alcon | |||
| Tears Naturale P.M. | Alcon | |||
| Fine tip Dumont forceps | Fine Science Tools | 11252-00 | ||
| 10 μl Hamilton Syringe (1701RN; 26s/2”/2) | Hamilton Syringe Co. | 80030 | ||
| 1/16 inch Compression Fittings | Hamilton Syringe Co. | 55751-01 | ||
| 1/16 inch OD, 0.010 inch ID, PEEK Tubing | Supelco, Bellefonte, PA | Z226661 | ||
| Dual RN Glass Coupler | Hamilton Syringe Co. | 55752-01 | ||
| Mineral Oil Priming Kit: includes syringe, needles, rubber septa | Hamilton Syringe Co. | PRMKIT |
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