Single-cell sequencing reveals peritoneal environment and insights into fibrosis in CAPD patients

Long-term peritoneal dialysis (PD) is associated with the development of perito-neal fibrosis (PF). Understanding the changes of immune environments and peri-toneal mesothelial cells (PMCs) may lead to the discovery of mechanisms of PF. Therefore, we used single-cell RNA sequencing to interrogate cell composition and transcriptome characteristics in dialysate of continuous ambulatory PD (CAPD) patients at different stages. Results showed that six major cell popula-tions were identified in overnight effluent dialysate. Two subsets of macrophages (Macro-c2-SSP1 and Macro-c5-FCN1&SSP1) and PMCs (HSPA1A + PMCs and RPL34 + PMCs) had the property of promoting fibrosis. Long-term patients had higher markers of cytotoxic CD8+T cells. Moreover, the expression levels of fibrosis-related genes were significantly increased and PMCs interacted closely with immune cells in the long-term group (p < 0.05). These data reveal new phe-notypes and functional characteristics of immune cells and PMCs in dialysate of CAPD patients with different stages, which provide potential mechanisms and therapeutic strategies for PF.