In vivo imaging of dorsal root regeneration: rapid immobilization and presynaptic differentiation at the CNS/PNS border.
In vivo imaging of dorsal root regeneration: rapid immobilization and presynaptic differentiation at the CNS/PNS border.
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DOI：
10.1523/jneurosci.4638-10.2011
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发表时间：
2011-03-23
期刊：
影响因子：
--
通讯作者：
Son YJ
中科院分区：
文献类型：
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作者：
Di Maio A;Skuba A;Himes BT;Bhagat SL;Hyun JK;Tessler A;Bishop D;Son YJ
背根（DR）轴突在PNS中再生，但转向或停止在背根进入区（DREZ），即进入CNS的入口。早期的研究依赖于传统的跟踪技术或死后分析，将再生失败归因于生长抑制剂和缺乏内在的生长潜力。在这里，我们报告的第一个体内成像研究DR再生。在thy 1-YFPH小鼠中，荧光标记的大直径DR轴突通过DR挤压部位而不是横断部位伸长，并且沿着根部以> 1.5 mm/天的速度生长，几乎没有变化。令人惊讶的是，它们在DREZ遇到星形胶质细胞时很少转身，而是深入到CNS区域，在那里它们迅速停滞，然后保持完全不动或稳定，即使在条件损伤后，沿着根部沿着。停滞的轴突尖端和相邻的轴强烈免疫标记与突触标记。针对DREZ的超微结构分析，最近到达的轴突丰富，另外显示丰富的轴突轮廓表现出突触前的功能，如突触囊泡聚集在活动区，但不是突触后功能。这些数据表明，轴突既不排斥，也不连续抑制在DREZ的生长抑制分子，但迅速稳定，因为它们侵入中枢神经系统领域的DREZ，非神经元细胞上形成突触前末梢。我们的工作介绍了一个新的实验范式，DR再生的调查，并可能有助于诱导显着再生后，脊髓根损伤。
Dorsal root (DR) axons regenerate in the PNS but turn around or stop at the dorsal root entry zone (DREZ), the entrance into the CNS. Earlier studies that relied on conventional tracing techniques or postmortem analyses attributed the regeneration failure to growth inhibitors and lack of intrinsic growth potential. Here, we report the first in vivo imaging study of DR regeneration. Fluorescently labeled, large-diameter DR axons in thy1-YFPH mice elongated through a DR crush site, but not a transection site, and grew along the root at > 1.5 mm per day with little variability. Surprisingly, they rarely turned around at the DREZ upon encountering astrocytes, but penetrated deeper into the CNS territory, where they rapidly stalled and then remained completely immobile or stable, even after conditioning lesions that enhanced growth along the root. Stalled axon tips and adjacent shafts were intensely immunolabeled with synapse markers. Ultrastructural analysis targeted to the DREZ enriched with recently arrived axons additionally revealed abundant axonal profiles exhibiting presynaptic features such as synaptic vesicles aggregated at active zones, but not postsynaptic features. These data suggest that axons are neither repelled nor continuously inhibited at the DREZ by growth inhibitory molecules but are rapidly stabilized as they invade the CNS territory of the DREZ, forming presynaptic terminal endings on non-neuronal cells. Our work introduces a new experimental paradigm to the investigation of DR regeneration and may help to induce significant regeneration after spinal root injuries.