Postmortem Studies of Neuroinflammation in Autism Spectrum Disorder: a Systematic Review

Although the neurobiological basis for autism spectrum disorder (ASD) has not yet been fully clarified, converging lines of evidence implicated a role of neuroinflammation in the etiological pathway of this disorder. The present article provided a systematic review of publications regarding the involvement of different components of neuroinflammation in postmortem brain samples of subjects diagnosed with ASD. A systematic search of PubMed, Embase, and Web of Science was conducted, which was supplemented by manual searching of reference lists of included articles. The screening for study and extraction of data were conducted by two independent authors after reviewing the abstract and full text. Of 356 articles identified in the literature search, 27 articles comprising 685 subjects (ASD = 313, controls = 351, schizophrenia = 10, epilepsy = 11) covering 19 brain regions met the eligibility criteria for this review. The search yielded 11 studies that estimated astrocyte-related changes, 8 studies that reported microglia-related changes, 2 studies that evaluated oligodendrocyte-related changes, 3 studies that examined changes in glial cells without differentiating cell types, 6 studies that evaluated the levels of cytokines and chemokines, and 7 studies that measured other inflammatory parameters in postmortem brain samples of subjects with ASD compared with controls. Although a few studies noted a lack of changes in neuroinflammatory markers in postmortem brain samples of ASD subjects, the majority of studies supported the presence of neuroinflammation in the neurobiological pattern of ASD as shown by activation of astrocytes and microglia together with abnormal levels of cytokines and chemokines.