Reactive morphology of dividing microglia following kainic acid administration

Abstract

The microglial response to a pathological microenvironment is hallmarked by a change in cellular morphology. Following a pathological stimulus, microglia become reactive and simultaneously divide to create daughter cells. Although a wide array of microglial morphologies has been observed, the exact functions of these distinct morphologies are unknown, as are the morphology and reactivity status of dividing microglia. In this study, we used kainic acid to trigger microglial activation and cell division. Following a cortical kainic acid injection, microglial morphology and proliferation were examined at 3 days post-injection using immunohistochemistry for ionized calcium binding adapter molecule 1 (Iba1) to stain for microglia, and KI67 as a marker of cell division. Individual microglial cells were isolated from photomicrographs and skeletal and fractal analyses were used to examine cell size and spatial complexity. We examined the morphology of microglia in both wildtype and microglia-specific tumor necrosis factor (TNF)-α knockout mice. Data were analyzed using generalized linear mixed models or a two-way ANOVA. We found that dividing microglia had a more reactive morphology (larger cell body area, longer cell perimeter, and less ramification) compared to microglia that were not dividing, regardless of microglial release of TNF-α. However, we also observed dividing microglia with a complex, more ramified morphology. Changes in microglial morphology and division were greatest near the kainic acid injection site. This study uses robust and quantitative techniques to better understand microglial cell division, morphology, and population dynamics, which are essential for the development of novel therapeutics that target microglia.

Neuronal deletion of Gtf2i results in developmental microglial alterations in a mouse model related to Williams syndrome

“…Specifically, our findings show there is a significant microglial proliferation, an additional trait of activation (Green et al, 2022), and a significantly elevated transcripts level involved with activation and inflammation in P4 Gtf2i cKO mice, as compared to controls. Furthermore, the proportion of Iba1 + CD68 + cells significantly decreased in the cortices, alongside reduced CD68 protein levels in the M2 cortex of P4 Gtf2i cKO mice.…”

Biomaterial strategies for regulating the neuroinflammatory response

“…41 Perturbations to parenchymal tissue caused by injury or disease activate microglia, causing alterations in their gene expression and adoption of an amoeboid-like morphology. 42,43 Depending on Marian H. Hettiaratchi Dr. Marian Hettiaratchi is an Assistant Professor at the Knight Campus for Accelerating Scientific Impact at the University of Oregon. She received a BSc in chemical engineering with a biomedical specialization from the University of Calgary and PhD in biomedical engineering from the Georgia Institute of Technology and Emory University.…”

“…41 Perturbations to parenchymal tissue caused by injury or disease activate microglia, causing alterations in their gene expression and adoption of an amoeboid-like morphology. 42,43 Depending on signals perceived in the surrounding environment, stimulated microglia will transition to either a classically activated (M1) or alternatively activated (M2) state, similar to that of macrophages. While M1/M2 nomenclature is typically used to distinguish between pro- and anti-inflammatory phenotypes, respectively, recent studies have shown this system fails to capture the full spectrum of microglial phenotypes.…”

Repetitive mild traumatic brain injury elicits a reactive microglial morphology and elevates serum neurofilament light levels, independent of NLRP3 inflammasome inhibition

“…Microglial morphology was analysed in ImageJ as previously published [18,20,43]. In brief, three randomly selected microglia were isolated from z-stacked images (total of 6-9 cells per ROI, per mouse, Fig.…”

“…Quanti cation of microglial cell body size and process length are morphological outcomes commonly used to measure microglial reactivity [18,19]. After a TBI, microglia rapidly migrate to areas of damage and proliferate to increase their functional capacity [20]. Reactive microglia morphology is characterised by an enlarged cell body with shortened processes, with increased capacity for production of bioactive mediators, and heightened ability for chemotaxis compared to microglia that are not responding to a pathological stimulus.…”