Where Are They Now: Spatial and Molecular Diversity of Tissue-Resident Macrophages in the Kidney

Kidney resident macrophages (KRMs) are involved in homeostasis, phagocytosis, defense against infectious agents, response to insults, inflammation, and tissue repair. They also play critical roles in the pathogenesis and recovery from many kidney diseases such as acute kidney injury. KRMs historically have been studied as one homogenous population, but the wide-ranging roles and phenotypes observed suggest that there is greater heterogeneity than previously understood. Advancements in RNA sequencing technologies (single-cell RNA sequencing and spatial transcriptomics) have identified specific subsets of KRMs that are molecularly, functionally, and spatially distinct with dynamic changes after kidney injury. Multiple studies have identified unique markers that represent these subpopulations, permitting further characterization of the function and roles they play in the kidney. Understanding the diversity of KRM subpopulations will be key in the development of novel therapies used in treating kidney diseases and promoting kidney health.