Distinguishing the endotypes of Chronic rhinosinusitis: the emerging roles of macrophages

INTRODUCTION: Chronic rhinosinusitis (CRS) is a heterogeneous inflammatory disorder characterized by different endotypes classically known as type 1/2/3 inflammation. Macrophages play a pivotal role in the pathogenesis of CRS. Under diverse inflammatory conditions, macrophages can polarize into different subsets and exert distinct functions across CRS endotypes. Recently, single-cell transcriptome analysis identified a series of macrophage subsets that have specific gene expression signatures associated with CRS endotypes. AREAS COVERED: A literature search was conducted using PubMed with keywords 'CRS,' 'endotype,' and 'macrophage' and related terms, focusing on studies published over the past 10 years. This review dissects macrophage heterogeneity across CRS endotypes, summarizes how diverse stimulus factors shape macrophage states, and updates their roles under endotypes, providing clues for the development of macrophage-based biomarkers for endotyping and targeted therapy. EXPERT OPINION: Effectively distinguishing CRS endotypes is meaningful for personalized therapies. An endotype-based interpretation of macrophage heterogeneity helps explain the divergent patterns of inflammation in CRS. In addition, the nasal tissue-resident macrophages attract growing interest as their contribution to olfactory loss in CRS.