Time course images of cellular injury and recovery in murine brain with high-resolution GRIN lens system

Abstract

Time course, in vivo imaging of brain cells is crucial to fully understand the progression of secondary cellular damage and recovery in murine models of injury. We have combined high-resolution gradient index lens technology with a model of diffuse axonal injury in rodents to enable repeated visualization of fine features of individual cells in three-dimensional space over several weeks. For example, we recorded changes in morphology in the same axons in the external capsule numerous times over 30 to 60 days, before and after induced traumatic brain injury. We observed the expansion of secondary injury and limited recovery of individual axons in this subcortical white matter tract over time. In another application, changes in microglial activation state were visualized in the penumbra region of mice before and after ischemia induced by middle carotid artery occlusion. The ability to collect a series of high-resolution images of cellular features of the same cells pre- and post-injury enables a unique opportunity to study the progression of damage, spontaneous healing, and effects of therapeutics in mouse models of neurodegenerative disease and brain injury.

Rapid and Reversible Development of Axonal Varicosities: A New Form of Neural Plasticity

“…In the same study, we further visualized their rapid induction in an mTBI mouse model, where the usage of Thy1-YFP transgenic mice was the key to clearly visualize such axonal change (Gu et al, 2017 ). Importantly, consistent with our results, there are several recent studies showing rather rapid induction of axonal varicosities in vivo in different types of mTBI mouse models (Marion et al, 2018 ; Vascak et al, 2018 ; Ziogas and Koliatsos, 2018 ; Pernici et al, 2019 ; Weber et al, 2019 ). Therefore, rapid and reversible formation of axonal varicosities in CNS neuron mechanosensation is likely a new form of neural plasticity that is related to mechanical injury.…”

“…Collectively, this experimental result confirmed that axonal varicosities indeed rapidly form upon mechanical impact in vivo in the mouse model of repetitive mTBI, suggesting that at least some axonal varicosities were induced by the primary injury in mTBI. Since 2018, several groups independently reported that axonal varicosities were induced from a few hours to 2 days after impact in the brain of different mTBI mouse models (Marion et al, 2018;Ziogas and Koliatsos, 2018;Pernici et al, 2019;Weber et al, 2019), consistent with the findings using rcTBI.…”

“…By combining the FPI model and in vivo imaging using highresolution gradient index lens technology, the Murray group was able to examine axonal changes in the same mouse and visualized axonal morphology from external capsule in both preinjury and post-injury stages for up to 60 days after injury. They found axonal varicosities and undulated axons 1 h post injury (Pernici et al, 2019(Pernici et al, , 2020. Administration of minocycline to reduce microglia activation for three days starting 1 or 72 h after injury inhibited axonal varicosity formation or promoted axon recovery, respectively (Pernici et al, 2020).…”

Cellular Analysis and Chemotherapeutic Potential of a Bi-Functionalized Halloysite Nanotube

“…Images were scanned in three dimensions with x- and y-dimensions of 248 μm (1024 × 1024-pixel resolution), with z-steps of 2 μm (z stack) to produce z stacks of 36 and 46 μm to ensure that all cells were captured within the volume. Pixel dwell time was set to 2 μL with pixel averaging of 5/scan to acquire z stack images [ 17 , 18 ].…”

Low brain endocannabinoids associated with persistent non-goal directed nighttime hyperactivity after traumatic brain injury in mice

“…The majority of experimental studies using a number of different controlled brain injuries in rodents focused on the very early period after TBI, in particular the cellular, inflammatory and molecular mechanisms that orchestrate beneficial shielding of non-injured tissue and repair, but also pro-inflammatory secondary damage [35][36][37] . In contrast to the substantial advance in the understanding of early post-TBI events, long-lasting, protracted changes of behavior are less well studied.…”