Division of Neurology, The Children's Hospital of Philadelphia (CHOP), Philadelphia, PA 19104, USA; University of Pennsylvania Perelman School of Medicine, Philadelphia, PA 19104, USA.
Department of Anesthesiology and Critical Care Medicine, CHOP Research Institute, Philadelphia, PA 19104, USA.
Neurosci Lett. 2023 Apr 23;803:137171. doi: 10.1016/j.neulet.2023.137171. Epub 2023 Mar 8.
Microglia, the resident immune cells of the brain, support normal brain function and the brain's response to disease and injury. The hippocampal dentate gyrus (DG) is important for microglial study due to its central role in many behavioral and cognitive functions. Interestingly, microglia and related cells are distinct in female vs. male rodents, even in early life. Indeed, postnatal day (P)-dependent sex differences in number, density, and morphology of microglia have been reported in certain hippocampal subregions at specific ages. However, sex differences in the DG have not yet been assessed at P10, a translationally relevant time point as the rodent neuroanatomical eqivalent of human term gestation. To address this knowledge gap, Iba1+ cells in the DG (which are enriched in the Hilus and Molecular Layer) in female and male C57BL/6J mice were analyzed for their number (via stereology) and density (via stereology and via sampling). Next, Iba1+ cells were classified into morphology categories previously established in the literature. Finally, the percent of Iba1+ cells in each morphology category was multiplied by total cell number to generate a total number of Iba1+ cells in each category. Results show no sex difference in Iba1+ cell number, density, or morphology in the P10 Hilus or Molecular Layer. The lack of sex difference in Iba1+ cells in P10 DG using commonly-employed methodologies (sampling, stereology, morphology classification) provides a baseline from which to interpret microglia changes seen after injury.
小胶质细胞是大脑中的固有免疫细胞，支持大脑的正常功能和对疾病与损伤的反应。海马齿状回（DG）在微胶质细胞研究中很重要，因为它在许多行为和认知功能中起着核心作用。有趣的是，雌性和雄性啮齿动物的小胶质细胞及其相关细胞存在差异，即使在生命早期也是如此。事实上，已经报道了在特定年龄的某些海马亚区中，产后第（P）天依赖的小胶质细胞数量、密度和形态的性别差异。然而，在 P10 时，DG 中尚未评估性别差异，P10 是一个具有转化意义的时间点，相当于人类足月妊娠的啮齿动物神经解剖学等效物。为了解决这一知识空白，分析了雌性和雄性 C57BL/6J 小鼠 DG 中的 Iba1+细胞（富含在门区和分子层）的数量（通过体视学法）和密度（通过体视学法和抽样法）。接下来，将 Iba1+细胞分类为文献中先前建立的形态类别。最后，将每个形态类别中的 Iba1+细胞的百分比乘以总细胞数，以生成每个类别中的总 Iba1+细胞数。结果表明，在 P10 门区或分子层中，Iba1+细胞的数量、密度或形态没有性别差异。在 P10 DG 中，使用常用方法（抽样、体视学法、形态分类）未观察到 Iba1+细胞的性别差异，为解释损伤后观察到的小胶质细胞变化提供了基线。
