Modeling the Effect of Diesel Particulate Matter on Human Induced Pluripotent Stem Cell Derived Cerebral Organoids and Mixed Neural Cultures

Background: Diesel particulate matter (DPM) exposure during fetal development has been implicated in the increased risk of autism spectrum disorders (ASD).¹ However, current methods dissecting the molecular effects of DPM on neural development are often performed in cell lines or non-human models instead of the multicellular environment of the developing human brain. To overcome this challenge, we used a combination of cerebral organoids and adherent differentiated neurons derived from human induced pluripotent stem cells (hiPSC) to study the effect of DPM on human neuronal development. Our data suggest a potential molecular model of DPM action in human brain development.

Objectives: To study the structural and molecular changes to neurons developing within cerebral organoids and mixed neural cultures to better model the impact of DPM on human brain development.

Methods: We used commercially derived hiPSC lines differentiated into cerebral organoids and mixed neural cultures. The cerebral organoids were treated with DPM for a length of ten days after reaching maturation and analysis of gene expression was determined using RNA-seq and immunocytochemistry. The differentiated mixed neural cultures were treated with DPM for 24 hours and analyzed by RNA-seq and immunocytochemistry.

Results: Genes shown to be downregulated (137 genes) in cerebral organoids treated with DPM based on gene ontology analysis (pval <0.05) showed an enrichment in biological processes including regulation of synaptic activity, regulation of Schwann cell differentiation, and axonal transport. Upregulated genes (453 genes) with a biological process enrichment based on gene ontology analysis (pval <0.05) include SNARE complex disassembly and TORC2 signaling. Analysis of cerebral organoids identified several genes differentially expressed of interest in ASD such as SGCE (a MECP2 binding target). Other differentially expressed genes include TBL1XR1 and KANSL1 that are implicated in intellectual disability disorders. As additional data is collected on the mixed neural cultures we expect to continue resolving mechanisms for DPM.

Conclusions: Diesel particulate matter is a known environmental factor that increases the risk of ASD. The use of hiPSCs derived cerebral organoids and mixed neural cultures show that they can be used to study the environmental effects of DPM on autism, and that organoids can be used as a 3-D model of exposure risk in neurodevelopmental disorders.

[1] Volk, H.E.; Lurmann, F.; Penfold, B.; Hertz-Picciotto, I.; McConnel, R (2013). Traffic related air pollution, pariculate matter, and autism. JAMA psychiatry. 70(1):71-77