Hayashi Ayato, Pannucci Christopher, Moradzadeh Arash, Kawamura David, Magill Christina, Hunter Daniel A, Tong Alice Y, Parsadanian Alexander, Mackinnon Susan E, Myckatyn Terence M
Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, Campus Box 8238, 660 South Euclid Ave., St. Louis, MO 63110, USA.
Exp Neurol. 2008 Jun;211(2):539-50. doi: 10.1016/j.expneurol.2008.02.031. Epub 2008 Mar 25.
End-to-side (ETS) nerve repair remains an area of intense scrutiny for peripheral nerve surgeon-scientists. In this technique, the transected end of an injured nerve, representing the "recipient" is sutured to the side of an uninjured "donor" nerve. Some works suggest that the recipient limb is repopulated with regenerating collateral axonal sprouts from the donor nerve that go on to form functional synapses. Significant, unresolved questions include whether the donor nerve needs to be injured to facilitate regeneration, and whether a single donor neuron is capable of projecting additional axons capable of differentially innervating disparate targets. We serially imaged living transgenic mice (n=66) expressing spectral variants of GFP in various neuronal subsets after undergoing previously described atraumatic, compressive, or epineurotomy forms of ETS repair (n=22 per group). To evaluate the source, and target innervation of these regenerating axons, nerve morphometry and retrograde labeling were further supplemented by confocal microscopy as well as Western blot analysis. Either compression or epineurotomy with inevitable axotomy were required to facilitate axonal regeneration into the recipient limb. Progressively more injurious models were associated with improved recipient nerve reinnervation (epineurotomy: 184+/-57.6 myelinated axons; compression: 78.9+/-13.8; atraumatic: 0), increased Schwann cell proliferation (epineurotomy: 72.2% increase; compression: 39% increase) and cAMP response-element binding protein expression at the expense of a net deficit in donor axon counts distal to the repair. These differences were manifest by 150 days, at which point quantitative evidence for pruning was obtained. We conclude that ETS repair relies upon injury to the donor nerve.
端侧（ETS）神经修复仍然是周围神经外科科学家们密切关注的领域。在这项技术中，将受伤神经的横断端（即“接受者”）缝合到未受伤的“供体”神经的侧面。一些研究表明，接受神经的肢体可由来自供体神经的再生侧支轴突芽重新支配，这些轴突芽随后形成功能性突触。重要的、尚未解决的问题包括供体神经是否需要受损以促进再生，以及单个供体神经元是否能够投射出能够差异性地支配不同靶标的额外轴突。我们对66只表达不同神经元亚群中GFP光谱变体的活体转基因小鼠进行了连续成像，这些小鼠在接受了先前描述的无创、压迫性或神经外膜切开术形式的ETS修复后（每组22只）。为了评估这些再生轴突的来源和靶标神经支配，通过共聚焦显微镜以及蛋白质免疫印迹分析进一步补充了神经形态测量和逆行标记。需要压迫或不可避免地切断轴突的神经外膜切开术来促进轴突向接受神经的肢体再生。损伤程度逐渐增加的模型与接受神经的再支配改善相关（神经外膜切开术：184±57.6条有髓轴突；压迫：78.9±13.8条；无创：0条），雪旺细胞增殖增加（神经外膜切开术：增加72.2%；压迫：增加39%）以及环磷酸腺苷反应元件结合蛋白表达增加，但代价是修复远端供体轴突数量的净减少。这些差异在150天时显现出来，此时获得了修剪的定量证据。我们得出结论，ETS修复依赖于供体神经的损伤。
