Nanoparticle‐microglial interaction in the ischemic brain is modulated by injury duration and treatment

Abstract

Cerebral ischemia is a major cause of death in both neonates and adults, and currently has no cure. Nanotechnology represents one promising area of therapeutic development for cerebral ischemia due to the ability of nanoparticles to overcome biological barriers in the brain. ex vivo injury models have emerged as a highthroughput alternative that can recapitulate disease processes and enable nanoscale probing of the brain microenvironment. In this study, we used oxygen-glucose deprivation (OGD) to model ischemic injury and studied nanoparticle interaction with microglia, resident immune cells in the brain that are of increasing interest for therapeutic delivery. By measuring cell death and glutathione production, we evaluated the effect of OGD exposure time and treatment with azithromycin (AZ) on slice health. We found a robust injury response with 0.5 hr of OGD exposure and effective treatment after immediate application of AZ. We observed an OGD-induced shift in microglial morphology toward increased heterogeneity and circularity, and a decrease in microglial number, which was reversed after treatment. OGD enhanced diffusion of polystyrene-poly(ethylene glycol) (PS-PEG) nanoparticles, improving transport and ability to reach target cells. While microglial uptake of dendrimers or quantum dots (QDs) was not enhanced after injury, internalization of PS-PEG was significantly increased. For PS-PEG, AZ treatment restored microglial uptake to normal control levels. Our results suggest that different nanoparticle platforms should be carefully screened before application and upon doing so; disease-mediated changes in the brain microenvironment can be leveraged by nanoscale drug delivery devices for enhanced cell interaction.

Brain Tissue-Derived Extracellular Vesicle Mediated Therapy in the Neonatal Ischemic Brain

“…We performed dose- and time-dependency experiments to evaluate the therapeutic potential of BEVs in a HI brain slice model. We observed an expected decrease in the percent cellular cytotoxicity over time in the healthy and OGD control conditions as the slices naturally recover from acute slicing, aligning with previous outcomes in our OGD slice model in rats [ 33 ]. Results from these studies suggest that 25 μg of BEVs is the minimum therapeutic dosage after 24 h exposure time.…”

“…To study EV therapeutic activity and its impact on cellular behavior, we performed oxygen glucose deprivation (OGD) in organotypic whole hemisphere (OWH) slices from the P10 rat brain to model HI in term-equivalent neonates [ 32 , 33 ]. OWH brain slices uniquely capture the 3D cytoarchitecture and regional complexity of the brain [ 33 , 34 ].…”

“…To study EV therapeutic activity and its impact on cellular behavior, we performed oxygen glucose deprivation (OGD) in organotypic whole hemisphere (OWH) slices from the P10 rat brain to model HI in term-equivalent neonates [ 32 , 33 ]. OWH brain slices uniquely capture the 3D cytoarchitecture and regional complexity of the brain [ 33 , 34 ]. OWH slices allow for the simultaneous assessment of different brain regions, such as the cortex, hippocampus, thalamus, and others, which are not present collectively in standard organoid, cortical, or hippocampal culture models [ 35 ].…”

“…Comparing cellular cytotoxicity values among ex vivo slices revealed several important trends. First, the percent cytotoxicity expectedly decreased over time in both the healthy and OGD control conditions as tissues recovered from acute slicing ( Figure 3 B) [ 33 ]. Second, 25 μg is the observed minimum therapeutic dosage beginning at 24 h exposure.…”

The Spatiotemporal Evolution of MRI-Derived Oxygen Extraction Fraction and Perfusion in Ischemic Stroke

“…Further investigations are needed to accelerate the opening of collateral circulation by a pharmacological method in patients with severe perfusion deficit and with lesions in deep white matter. Other auxiliary treatments such as modulation of neuroinflammation (Joseph et al, 2020), free radical toxicity, and apoptosis (Dirnagl et al, 1999) are also necessary to save the ischemic brain tissue and improve neurological functions.…”