Microglia Density and Morphology at P10 in the Early Postnatal Male and Female C57BL/6J Mouse Hippocampus

Max Wragan

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Project Summary

Microglia, the brain’s immune cells, play critical roles in the maintenance of the healthy brain and its response to disease and injury. Microglia maintain healthy brain development by facilitating synaptic pruning, learning, and memory. Further, microglia respond to brain injury by clearing debris and secreting inflammatory factors. Abnormal microglia response is a characteristic of many neurodevelopmental disorders, including cerebral palsy, schizophrenia, epilepsy, and autism. Interestingly, male and female microglia have innate sex differences and previous literature disagrees regarding the developmental time points at which males or females have greater microglia density. Additionally, certain time points like postnatal (P) day 10 have not been studied. Existing data studying sex-based differences in hippocampal microglial density also fails to study the subregions of the hippocampal dentate gyrus molecular layer and hilus independently. To address these knowledge gaps, we quantified microglia by recording Iba1+ cell densities and analyzed Iba1+ cell morphology for 40-micrometer coronal sections of male and female C57BL/6J mouse brains at the P10 time point. These densities were quantified bilaterally in the anterior hippocampus for the hippocampal subregions of the dentate gyrus molecular layer (DG Mol), dentate gyrus hilus (DG Hil), CA1 stratum radiatum (CA1), and CA3 stratum radiatum (CA3). We imaged these subregions using an Olympus light microscope (40x). Then we analyzed these images for Iba1+ cell density and morphology. The morphology was classified into one of four categories: Round or ameboid (round-ish soma, no processes), Stout (round-ish soma, short process), Thick (irregular soma with few, thick processes), or Thin (irregular soma with multiple thin processes). Our analysis reveals no sex-based differences in Iba1+ cell density in the DG Mol, DG Hilus, CA1, or CA3 for the 6 male and 7 female mice quantified. However, female mice did show a larger portion of microglia with Thick morphology in the DG Mol and DG Hilus relative to males, which instead showed more Thin cells.

To see my poster, please visit Penn Presents: https://presentations.curf.upenn.edu/poster/microglia-density-and-morpho...
https://vimeo.com/593325887