Tissue-resident macrophages constitute a population of immune cells whose phenotype and functions are shaped by their developmental origin and by the niches they occupy. While the heterogeneity of these cells from one organ to another is now well recognized, the diversity that may exist within a single tissue has remained largely overlooked. The present study set out to address this gap by investigating Kupffer cells, the embryonically derived resident macrophages of the liver.
Using high-dimensional approaches—combining cytometry, single-cell RNA sequencing across several technologies (Smart-seq2, 10X, Rhapsody), mass spectrometry-based proteomics, and confocal imaging—the researchers identified two distinct subpopulations among murine Kupffer cells. Both share a common signature but differ in the expression of numerous genes and proteins. The major population, CD206lo ESAM−, was designated KC1, whereas a minor population, CD206hi ESAM+, was termed KC2. The latter is distinguished by a transcriptional signature geared toward metabolic processes, particularly fatty acid metabolism, both at baseline and in the context of diet-induced obesity and hepatic steatosis.
Functional characterization relied on two complementary strategies: the selective depletion of KC2 cells and the targeted knockout of the Cd36 gene, which encodes a fatty acid transporter highly expressed by this subpopulation. These experiments revealed a decisive contribution of KC2 cells, through CD36 expression, to the hepatic oxidative stress associated with obesity. Moreover, depletion of this metabolically endowed subpopulation prevents diet-induced obesity, underscoring the involvement of these cells beyond their immune role alone.
Ultimately, this work establishes that Kupffer cells are more heterogeneous than previously assumed and describes a subpopulation specifically wired for metabolic functions. The distinction between KC1 and KC2 invites a reconsideration of the Kupffer cell not as a homogeneous entity, but as a collection of subtypes with specialized roles, one of which directly participates in the regulation of hepatic metabolism and oxidative stress in the context of obesity.