University of California, Institute for Memory Impairments and Neurological Disorders, Irvine, Calif, United States.
University of California Irvine, Department of Biomedical Engineering, Irvine, California, United States.
J Biomed Opt. 2018 Jun;23(6):1-6. doi: 10.1117/1.JBO.23.6.065007.
Spinal cord injury (SCI) causes permanent paralysis below the damaged area. SCI is linked to neuronal death, demyelination, and limited ability of neuronal fibers to regenerate. Regeneration capacity is limited by the presence of many inhibitory factors in the spinal cord environment. The use of poly(lactide-co-glycolide) (PLG) bridges has demonstrated the ability to sustain long-term regeneration after SCI in a cervical hemisection mouse model. Critically, imaging of regenerating fibers and the myelination status of these neuronal filaments is a severe limitation to progress in SCI research. We used a transgenic mouse model that selectively expresses fluorescent reporters (eGFP) in the neuronal fibers of the spinal cord. We implanted a PLG bridge at C5 vertebra after hemisection and evaluated in live animals' neuronal fibers at the bridge interface and within the bridge 8 weeks postimplant. These in vivo observations were correlated with in situ evaluation 12 weeks postimplantation. We sectioned the spinal cords and performed fluorescent bioimaging on the sections to observe neuronal fibers going through the bridge. In parallel, to visualize myelination of regenerated axons, we exploited the characteristics of the third-harmonic generation arising from the myelin structure in these fixed sections.
脊髓损伤 (SCI) 会导致损伤区域以下的永久性瘫痪。SCI 与神经元死亡、脱髓鞘和神经元纤维的再生能力有限有关。脊髓环境中存在许多抑制因子，限制了再生能力。聚（乳酸-共-乙醇酸）（PLG）桥的使用已经证明在颈半切小鼠模型中能够在 SCI 后维持长期的再生。至关重要的是，对再生纤维的成像以及这些神经元纤维的髓鞘状态是 SCI 研究进展的严重限制。我们使用了一种转基因小鼠模型，该模型在脊髓的神经元纤维中选择性地表达荧光报告基因（eGFP）。我们在半切后在 C5 椎骨植入 PLG 桥，并在植入后 8 周评估活体动物在桥界面和桥内的神经元纤维。这些体内观察结果与植入后 12 周的原位评估相关。我们对脊髓进行切片，并对切片进行荧光生物成像，以观察穿过桥的神经元纤维。同时，为了可视化再生轴突的髓鞘化，我们利用固定切片中髓鞘结构产生的三次谐波产生的特性。
