The dorsal root ganglion in Friedreich's ataxia
The dorsal root ganglion in Friedreich's ataxia
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DOI：
10.1007/s00401-009-0589-x
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发表时间：
2009-12-01
影响因子：
12.7
通讯作者：
Li, Danhong
中科院分区：
文献类型：
--
作者：
Koeppen, Arnulf H.;Morral, Jennifer A.;Li, Danhong
背根神经节（DRG）萎缩和背根（DR）变薄是弗里德赖希共济失调（FRDA）的标志。许多以前的作者还强调了DRG中较大神经元和较厚的有髓DR轴突的选择性脆弱性。这份报告是基于一个系统的复查DRG，DR和腹根（VR）在19个遗传学确诊的FRDA的情况下，免疫细胞化学和单双标记的免疫荧光抗体髓鞘，神经元和轴突的特异性蛋白; S-100 α作为卫星和雪旺细胞的标志物;层粘连蛋白;和铁反应蛋白铁蛋白，线粒体铁蛋白和ferroportin。轴突和髓鞘的共聚焦图像允许定量分析纤维密度和大小，以及DR和VR髓鞘形成的程度。一种新的技术，高清晰度X射线荧光（HDXRF）的聚乙二醇包埋固定组织，被用来“地图”铁在DRG。3例未固定的DRG冷冻组织可用于总铁的化学测定。在所有FRDA病例中，S-100 α阳性卫星细胞的增殖伴随着DRG中神经元的破坏。外周神经髓鞘蛋白22和磷酸化神经丝蛋白的双标记可视化证实了已知的大的有髓DR纤维的损失，但每单位面积的定量纤维计数没有变化。DR中有髓神经纤维与神经胶质阳性纤维的比率从0.55显著上升至0.66。在FRDA患者的VR中，纤维计数和髓鞘形成程度与正常人没有差异。轴突周长的汇总直方图揭示了DR中向更细纤维的转变，但VR中也有适度过量的较小轴突。FRDA的DR中雪旺细胞胞浆减少，而层粘连蛋白反应产物仍然突出。许多小轴突聚集在较少的雪旺细胞周围。在正常DRG中，铁蛋白定位于卫星细胞，而在FRDA中，这些细胞的增殖引起关于变性神经细胞的反应产物的宽边缘。未检测到线粒体铁蛋白。Ferroportin存在于正常卫星细胞和神经元的胞质中，以及DR和VR的大轴突中。在FRDA中，一些DRG神经元失去其胞质的ferroportin免疫反应，而卫星细胞的胞质仍ferroportin阳性。DR轴突的Ferroportin消失与大纤维的萎缩平行。DRG的HDXRF检测到铁荧光的区域性和弥漫性增加，其与卫星细胞中的铁蛋白表达相匹配。这些观察结果支持以下结论：卫星细胞和DRG神经元受到铁代谢异常的影响; DR中小轴突的再生和不适当的髓鞘形成是该疾病的特征。
Atrophy of dorsal root ganglia (DRG) and thinning of dorsal roots (DR) are hallmarks of Friedreich's ataxia (FRDA). Many previous authors also emphasized the selective vulnerability of larger neurons in DRG and thicker myelinated DR axons. This report is based on a systematic reexamination of DRG, DR and ventral roots (VR) in 19 genetically confirmed cases of FRDA by immunocytochemistry and single- and double-label immunofluorescence with antibodies to specific proteins of myelin, neurons and axons; S-100 alpha as a marker of satellite and Schwann cells; laminin; and the iron-responsive proteins ferritin, mitochondrial ferritin, and ferroportin. Confocal images of axons and myelin allowed the quantitative analysis of fiber density and size, and the extent of DR and VR myelination. A novel technology, high-definition X-ray fluorescence (HDXRF) of polyethylene glycol-embedded fixed tissue, was used to "map" iron in DRG. Unfixed frozen tissue of DRG in three cases was available for the chemical assay of total iron. Proliferation of S-100 alpha-positive satellite cells accompanied neuronal destruction in DRG of all FRDA cases. Double-label visualization of peripheral nerve myelin protein 22 and phosphorylated neurofilament protein confirmed the known loss of large myelinated DR fibers, but quantitative fiber counts per unit area did not change. The ratio of myelinated to neurofilament-positive fibers in DR rose significantly from 0.55 to 0.66. In VR of FRDA patients, fiber counts and degree of myelination did not differ from normal. Pooled histograms of axonal perimeters disclosed a shift to thinner fibers in DR, but also a modest excess of smaller axons in VR. Schwann cell cytoplasm in DR of FRDA was depleted while laminin reaction product remained prominent. Numerous small axons clustered around fewer Schwann cells. Ferritin in normal DRG localized to satellite cells, and proliferation of these cells in FRDA caused wide rims of reaction product about degenerating nerve cells. Mitochondrial ferritin was not detectable. Ferroportin was present in the cytoplasm of normal satellite cells and neurons, and in large axons of DR and VR. In FRDA, some DRG neurons lost their cytoplasmic ferroportin immunoreactivity, whereas the cytoplasm of satellite cells remained ferroportin positive. Ferroportin in DR axons disappeared in parallel with atrophy of large fibers. HDXRF of DRG detected regional and diffuse increases in iron fluorescence that matched ferritin expression in satellite cells. The observations support the conclusions that satellite cells and DRG neurons are affected by iron dysmetabolism; and that regeneration and inappropriate myelination of small axons in DR are characteristic of the disease.