Microglia (MG) are the first cells to react to the abnormal incoming signals that follow an injury of sensory nerves and play a critical role in the development and maintenance of neuropathic pain, a common sequel of nerve injuries. Here we present population data on cell number, soma size, and length of processes of MG in the caudal division of the spinal trigeminal nucleus (Sp5C) in control mice and at the peak of microgliosis (7 days) following unilateral transection of the infraorbital nerve (IoN). The study is performed combining several bias- and assumption-free imaging and stereological approaches with different immunolabeling procedures, with the objective of tackling some hard problems that often hinder proper execution of MG morphometric studies. Our approach may easily be applied to low-density MG populations, but also works, with limited biases, in territories where MG cell bodies and processes form dense meshworks. In controls, and contralaterally to the deafferented side, MG cell body size and shape and branching pattern matched well the descriptions of "resting" or "surveillant" MG described elsewhere, with only moderate intersubject variability. On the superficial laminae of the deafferented side, however, MG displayed on average larger somata and remarkable diversity in shape. The number of cells and the length of MG processes per mm3 increased 5 and 2.5 times, respectively, indicating a net 50% decrease in the mean length of processes per cell. By using specific immunolabeling and cell sorting of vascular macrophages, we found only a negligible fraction of these cells in Sp5C, with no differences between controls and deafferented animals, suggesting that blood-borne monocytes play at most a very limited role in the microgliosis occurring following sensory nerve deafferentation. In sum, here we present reliable morphometric data on MG in control and deafferented trigeminal nuclei using efficient methods that we propose may equally be applied to any morphometric population analysis of these cells under different physiological or pathological conditions.

中文翻译：

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多脱除脊髓三叉神经核中小胶质细胞的形态计量学评估。

小胶质细胞（MG）是对感觉神经损伤后的异常传入信号作出反应的第一批细胞，在神经病性疼痛（神经损伤的常见后遗症）的发生和维持中起着关键作用。在这里，我们提供了有关对照小鼠的脊柱三叉神经核（Sp5C）尾部分裂中的MG的细胞数量，体细胞大小和MG的过程长度以及在眶下神经单侧横断后小胶质细胞增生高峰期（7天）的种群数据（离子）。这项研究结合了几种无偏倚和无假设的成像和体视学方法以及不同的免疫标记程序，目的是解决一些经常阻碍MG形态计量学研究正常进行的难题。我们的方法很容易适用于低密度重症肌无力人群，但也行之有效，在MG细胞主体和过程形成密集网状结构的地区，偏差有限。在对照中，并且与去痛的一侧相对，MG细胞的体型，形状和分支模式与别处描述的“静止”或“监视” MG的描述非常匹配，只有个体间的适度变异性。然而，在脱除皱痕的一侧的表层，MG平均表现出更大的躯体和明显的形状多样性。每mm3的单元数和MG进程的长度分别增加了5倍和2.5倍，表明每个单元的平均进程长度净减少了50％。通过对血管巨噬细胞进行特异性免疫标记和细胞分选，我们发现Sp5C中这些细胞的比例可忽略不计，而对照组和失活动物之间没有差异，提示血源性单核细胞在感觉神经脱除神经元后发生的小胶质细胞增生中最多发挥非常有限的作用。总而言之，在这里，我们使用有效的方法，提供了对照和去势力的三叉神经核中MG的可靠形态学数据，我们提出的有效方法可以同样地应用于这些细胞在不同生理或病理条件下的任何形态学种群分析。