Abstract WP478: Microglia Knockdown Reduces Inflammation and Improves Post-Stroke Cognitive Impairment in Diabetic Animals

Abstract

Unfortunately, over 40% of stroke victims have pre-existing diabetes which not only increases their risk of stroke up to 2-6 fold, but also worsens both functional recovery and the severity of cognitive impairment. Our lab has recently linked the chronic inflammation that persists in diabetic animals to their poor functional outcomes and exacerbated cognitive impairment, also known as post-stroke cognitive impairment (PSCI). Although we have shown that the development of PSCI in diabetes is associated with the upregulation and activation of pro-inflammatory microglia, we have not established a direct causation between the two. We tested the hypothesis that microglia depletion in the post-stroke recovery period prevents sustained inflammation and attenuates PSCI in diabetes. Methods: Diabetes was induced by a high fat diet (HFD) and low dose streptozotocin (STZ) combination. At 13 weeks of age, diabetic animals received bilateral intracerebroventricular (ICV) injections of short hairpin RNA (shRNA) lentiviral particles targeted at the colony stimulating factor 1 receptor (CSF1R), a key factor for microglia survival. After 14 days, animals were subjected to 60 min middle cerebral artery occlusion (MCAO) or sham surgery. Novel object recognition (NOR), and 2-trial Y-maze were utilized to evaluate cognitive function. Brains were analyzed by flow cytometry (B-D slice containing the prefrontal cortex through the hippocampus) and immunohistochemistry (B slice) 3 weeks post-MCAO. Results: CSF1R silencing resulted in a drastic 94% knockdown of residential microglia to relieve inflammation and decrease the macrophage infiltration by 74%. This also led to improved myelination of white matter in the brain and improved cognition in diabetic animals. Conclusion: Neuroinflammation, through microglial and macrophage polarization, is largely responsible for the development of PSCI in diabetes.

Inhibiting CSF1R alleviates cerebrovascular white matter disease and cognitive impairment

“…This approach, inhibition of CSF1R with GW2580, prevents microglial proliferation without affecting their survival (Neal et al, 2020;Olmos-Alonso et al, 2016), and is more translatable to a clinical setting given that complete elimination of microglia is unlikely to be desirable. Increased microglial numbers are also observed in the chronic post-stroke response in white matter and in this condition, depletion of microglia by shRNA targeting of Csf1r has protective effects on white matter integrity and cognitive abilities (Jackson et al, 2020). Collectively, the data suggests sustained microglial proliferation mediates white matter damage and contributes to vascular cognitive impairment.…”

“…Inhibition of CSF1R signaling restored white matter integrity to sham levels, providing evidence of a direct contribution of microglia to white matter disruption following chronic cerebral hypoperfusion. Other studies have similarly reported effects of GW2580 treatment to reduce microglial density in chronic disease models (Gerber et al, 2018;Gomez-Nicola et al, 2013;Martinez-Muriana et al, 2016;Neal et al, 2020;Olmos-Alonso et al, 2016) with some studies reporting a protective effect in models with white matter damage (Crespo et al, 2011;Garcia-Agudo et al, 2019;Gerber et al, 2018;Janova et al, 2018;Klein et al, 2015), including that observed in chronic stroke (Jackson et al, 2020). CSF1R/Csf1r is expressed by cells of the myeloid lineage and evidence for functional expression of CSF1R/Csf1r on non-myeloid cells is not compelling (Hume et al, 2020).…”