Human myeloid progenitor glucocorticoid receptor activation causes genomic instability, type 1 IFN‐ response pathway activation and senescence in differentiated microglia; an early life stress model

One form of early life stress, prenatal exposure to glucocorticoids (GCs), confers a higher risk of psychiatric and neurodevelopmental disorders in later life. Increasingly, the importance of microglia in these disorders is recognized. Studies on GCs exposure during microglial development have been limited, and there are few, if any, human studies. We established an in vitro model of ELS by continuous pre‐exposure of human iPS‐microglia to GCs during primitive hematopoiesis (the critical stage of iPS‐microglial differentiation) and then examined how this exposure affected the microglial phenotype as they differentiated and matured to microglia, using RNA‐seq analyses and functional assays. The iPS‐microglia predominantly expressed glucocorticoid receptors over mineralocorticoid receptors, and in particular, the GR‐α splice variant. Chronic GCs exposure during primitive hematopoiesis was able to recapitulate in vivo ELS effects. Thus, pre‐exposure to prolonged GCs resulted in increased type I interferon signaling, the presence of Cyclic GMP‐AMP synthase‐positive (cGAS) micronuclei, cellular senescence and reduced proliferation in the matured iPS‐microglia. The findings from this in vitro ELS model have ramifications for the responses of microglia in the pathogenesis of GC‐ mediated ELS‐associated disorders such as schizophrenia, attention‐deficit hyperactivity disorder and autism spectrum disorder. Main Points Human iPSC‐ derived microglia express glucocorticoid receptor alpha. Chronic glucocorticoid exposure during primitive hematopoiesis causes genomic instability and senescence in differentiated microglia; correlation with early‐life stress.