The glial perspective of autism spectrum disorder convergent evidence from postmortem brain and PET studies

The present study aimed to systematically and quantitatively review evidence derived from both postmortem brain and PET studies to explore the pathological role of glia induced neuroinflammation in the pathogenesis of ASD, and discuss the implications of these findings in relation to disease pathogenesis and therapeutic strategies.

An online databases search was performed to collate postmortem studies and PET studies regarding glia induced neuroinflammation in ASD as compared to controls. Two authors independently conducted the literature search, study selection and data extraction. The discrepancies generated in these processes was resolved through robust discussions among all authors.

The literature search yielded the identification of 619 records, from which 22 postmortem studies and 3 PET studies were identified as eligible for the qualitative synthesis. Meta-analysis of postmortem studies reported increased microglial number and microglia density as well as increased GFAP protein expression and GFAP mRNA expression in ASD subjects as compared to controls. Three PET studies produced different outcomes and emphasized different details, with one reported increased and two reported decreased TSPO expression in ASD subjects as compared to controls.

Both postmortem evidences and PET studies converged to support the involvement of glia induced neuroinflammation in the pathogenesis of ASD. The limited number of included studies along with the considerable heterogeneity of these studies prevented the development of firm conclusions and challenged the explanation of variability. Future research should prioritize the replication of current studies and the validation of current observations.