differences in cell type-specific fractions due to changes in absolute cell number, or due to changes in the transcriptional activity of single cells. We do observe that OCD subjects have lower cell type expression profiles of medium spiny neurons, the predominant cell type in the striatum65, pointing us to future studies to discriminate between these two possibilities. Interestingly, we also observed increases in astrocyte and vascular cell type fractions in OCD subjects. Though there is limited evidence linking these cell types to OCD, it was recently demonstrated that altering astrocytic calcium-dependent signaling in mice produces an OCD-like compulsive grooming phenotype and striatal microcircuit deficits66. Furthermore, astrocytes and vascular cells interact at tight junctions to regulate blood-brain barrier function. An increase in these cell fractions might reflect a compensatory change due to the hypermetabolism commonly observed in both the OFC and striatum of OCD subjects25,67–69.
