Divergent Epigenetic and Transcriptomic Remodelling during Monocyte Subset Differentiation in Systemic Lupus Erythematosus [RNA-seq]

Systemic Lupus Erythematosus (SLE) is an autoimmune disease characterized by systemic inflammation that involves various immune cell types. Monocytes play a central role in promoting and regulating inflammation. Peripheral blood classical monocytes subsequently differentiate into intermediate monocytes and then non-classical monocytes, assuming diverse roles and undergoing changes in their proportions during physiological immune responses and pathological conditions, including SLE. In this study, we obtained the epigenetic and transcriptomic profiles of these three monocyte subsets in an SLE cohort. We found different common and subset-specific alterations. While SLE classical monocytes had a stronger proinflammatory profile with an important interferon influence priming them towards macrophage differentiation, non-classical monocytes had a phenotype related to T cell differentiation regulation, with several indications pointing towards a Th17 promoting behavior. Integration of these bulk datasets with single-cell RNA-seq data of an SLE cohort shed light on the heterogeneity of our monocytes, confirming the interferon signature profile of classical monocytes and pointing towards intermediate and non-classical populations associated with exacerbated complement activation pathways, among others. Our results indicate a subversion of the epigenome and transcriptome in monocyte differentiation toward non-classical subsets in SLE, involving the STAT1 pathway and impacting function in relation to disease activity.