ORF39-02 - Cell Type-Specific Glucocorticoid Responsiveness during Inflammation Revealed by Single-Cell RNA-Sequencing Analysis

Glucocorticoids are widely prescribed anti-inflammatory drugs, yet their clinical utility is limited by a diverse array of side effects. Glucocorticoids act on virtually all cell types due to the ubiquitous expression of the glucocorticoid receptor (GR). While the molecular mechanisms of GR activation have been studied extensively, how GR signaling is modulated in a cell type-specific manner remains poorly understood. Here, we used single-cell RNA sequencing to characterize the transcriptional landscape of zebrafish larval tail fin tissue under conditions of dexamethasone treatment and wounding. We identified wounding-specific cell populations within epidermal cells and neutrophils. The wounding-associated epidermal cells showed elevated expression of inflammatory markers accompanied by a proliferation signature, indicative of a transition from acute inflammation towards tissue regeneration. Notably, these epidermal cells exhibited a reduced transactivation response to dexamethasone, while wounding-specific neutrophils displayed enhanced dexamethasone-mediated transrepression. By correlating dexamethasone responsiveness with GR coregulator expression and by inferring transcription factor activity, we identified candidate regulatory mechanisms underlying differential GR responsiveness across cell types. Using this validated single-cell RNA-seq method, we further examined cell type-specific GR activation of a novel selective glucocorticoid. Taken together, our comprehensive single-cell expression atlas of glucocorticoid action during acute inflammation yielded unique mechanistic insights into cell type-specific glucocorticoid responsiveness in vivo. This work may support the development of novel glucocorticoids with improved therapeutic selectivity based on new GR cofactor profiles.