Identification of Fibrosis-Associated ACP5+ Macrophages in the AKI-to-CKD Transition via Single-Cell RNA Sequencing

Background: The transition from acute kidney injury (AKI) to chronic kidney disease (CKD) represents a major clinical challenge, with few effective therapeutic strategies currently available. Macrophages are key mediators in this process, but the identity and function of specific pathogenic subpopulations remain unclear. Here, we identify a fibrosis-associated subpopulation of ACP5+ macrophages during AKI to CKD. Methods: We established a murine model of AKI to CKD transition by administering intraperitoneal injections of Aristolochic Acid I (AAI) every three days for two weeks, followed by a two-week remodeling phase. Kidney tissues from control, acute, and remodeling phases were collected and subjected to single cell RNA sequencing(scRNA-seq) using the 10X Genomics. After quality control and integration using scVI, we performed macrophage subclustering(Scanpy), pseudotime trajectories(Slingshot) and ligand-receptor(Cellchat2). ACP5+ macrophages were validated by immunofluorescence staining in both murine and human CKD kidneys. Functional inhibition of ACP5 was evaluated in AAI, IRI and UUO murine models. In vitro, BMDMs were treated with the ACP5 inhibitor to evaluate the effects on polarization and fibrotic signaling. Results: We profiled over 37,000 single cells and identified 15 major kidney cell types. Macrophage subclustering revealed a dynamic transition from inflammatory to fibrosis-associated phenotypes. Notably, we identified a distinct subpopulation of ACP5+ macrophages that expanded during the tissue remodeling phase. Immunostaining confirmed the accumulation of ACP5+ CD68+ macrophages in both murine and human CKD kidneys. Pharmacological inhibition of ACP5 significantly attenuated renal fibrosis, inflammation, and macrophage activation across AAI, IRI, and UUO models. In bone marrow–derived macrophages (BMDMs), ACP5 inhibition markedly suppressed TGFβ1–induced fibrogenic gene expression, suggesting a functional role in promoting pro-fibrotic polarization. Conclusion: This is the first study to identify ACP5+ macrophages as a scar-associated subpopulation that drives the AKI to CKD transition; targeting ACP5 effectively reduces fibrotic remodeling and immune activation, highlighting it as a promising therapeutic target to mitigate CKD progression following AKI. Funding: Government Support – Non-U.S.