Astrocytes in the Neuropathology of Bipolar Disorder: Review of Current Evidence

(1) Background: Approximately one-third of patients with bipolar disorder (BD) do not experience sustained remission with current treatments. Presently, astrocytes, i.e., glial cells that act as key regulators of neuroinflammation, have been a target for therapeutic development. Research regarding their role in the neuropathology of BD is limited. We conducted a scoping review on evidence linking astrocytes to the pathology of BD. (2) Methods: The search was conducted in MEDLINE for studies published from inception to August 2022. Studies of interest were data-extracted and reported based on the Preferred Reporting Items for Systematic Reviews and Meta-analysis Protocols. (3) Results: Overall, 650 publications were identified, of which 122 full texts were evaluated and 12 included. Four were in vitro, seven were ex vivo, and one study was both in vitro and in vivo. In vitro investigations focused on plasma levels of neuroinflammatory biomarkers S100B and glial fibrillary acidic protein (GFAP). Ex vivo investigations were post-mortem brain studies assessing astrocytes in regions of interest (i.e., anterior cingulate cortex, dorsolateral prefrontal cortex) using phosphorylated GFAP and ASCT-1. The in vivo and in vitro study evaluated morphological and chemical variations of YKL-40 between cohorts. (4) Conclusions: Reports indicate an association between astrocyte dysfunction and BD although larger studies are required to validate this association.