Do Jiun L, Allahwerdy Salam, David Ryan C, Weinreb Robert N, Welsbie Derek S
Hamilton Glaucoma Center, Viterbi Family Department of Ophthalmology, Shiley Eye Institute, University of California San Diego;
Hamilton Glaucoma Center, Viterbi Family Department of Ophthalmology, Shiley Eye Institute, University of California San Diego.
J Vis Exp. 2020 Sep 6(163). doi: 10.3791/61748.
Retinal ganglion cell (RGC) axons converge at the optic nerve head to convey visual information from the retina to the brain. Pathologies such as glaucoma, trauma, and ischemic optic neuropathies injure RGC axons, disrupt transmission of visual stimuli, and cause vision loss. Animal models simulating RGC axon injury include optic nerve crush and transection paradigms. Each of these models has inherent advantages and disadvantages. An optic nerve crush is generally less severe than a transection and can be used to assay axon regeneration across the lesion site. However, differences in crush force and duration can affect tissue responses, resulting in variable reproducibility and lesion completeness. With optic nerve transection, there is a severe and reproducible injury that completely lesions all axons. However, transecting the optic nerve dramatically alters the blood brain barrier by violating the optic nerve sheath, exposing the optic nerve to the peripheral environment. Moreover, regeneration beyond a transection site cannot be assessed without reapposing the cut nerve ends. Furthermore, distinct degenerative changes and cellular pathways are activated by either a crush or transection injury. The method described here incorporates the advantages of both optic nerve crush and transection models while mitigating the disadvantages. Hydrostatic pressure delivered into the optic nerve by microinjection completely transects the optic nerve while maintaining the integrity of the optic nerve sheath. The transected optic nerve ends are reapposed to allow for axon regeneration assays. A potential limitation of this method is the inability to visualize the complete transection, a potential source of variability. However, visual confirmation that the visible portion of the optic nerve has been transected is indicative of a complete optic nerve transection with 90-95% success. This method could be applied to assess axon regeneration promoting strategies in a transection model or investigate interventions that target the axonal compartments.
视网膜神经节细胞（RGC）轴突在视神经乳头处汇聚，将视觉信息从视网膜传递至大脑。青光眼、创伤和缺血性视神经病变等病理状况会损伤RGC轴突，破坏视觉刺激的传递，并导致视力丧失。模拟RGC轴突损伤的动物模型包括视神经挤压和横断范式。这些模型各有其固有的优缺点。视神经挤压通常比横断的损伤程度轻，可用于检测轴突在损伤部位的再生情况。然而，挤压力量和持续时间的差异会影响组织反应，导致可重复性和损伤完整性的变化。视神经横断会造成严重且可重复的损伤，使所有轴突完全受损。然而，切断视神经会因破坏视神经鞘而显著改变血脑屏障，使视神经暴露于外周环境。此外，若不重新对接切断的神经末端，就无法评估横断部位以外的再生情况。此外，挤压或横断损伤会激活不同的退行性变化和细胞通路。本文所述方法融合了视神经挤压和横断模型的优点，同时减轻了缺点。通过显微注射向视神经施加静水压力可完全切断视神经，同时保持视神经鞘的完整性。将横断的视神经末端重新对接，以便进行轴突再生检测。该方法的一个潜在局限性是无法直观确认完全切断，这可能是变异性的一个潜在来源。然而，通过视觉确认视神经可见部分已被切断，表明视神经完全横断的成功率为90 - 95%。该方法可用于评估横断模型中促进轴突再生的策略，或研究针对轴突部分的干预措施。
