Single-cell and spatial profiling reveal an IL-10-associated iCAF-M2 macrophage communication axis in high-grade serous ovarian cancer ascites.

High-grade serous ovarian cancer (HGSOC) ascites represents a highly immunosuppressive tumour microenvironment characterized by complex stromal-immune interactions. In this study, we aimed to delineate the cellular communication networks shaping immune dysfunction within HGSOC ascites, identify key regulatory signalling pathways, characterize the fibroblast-macrophage axis at single-cell resolution, and evaluate the therapeutic potential of IL-10 blockade in reversing macrophage-mediated immunosuppression. Single-cell RNA sequencing data of eight ascites samples from six HGSOC patients (GSE146026) were analysed using Seurat for clustering and differential expression, followed by CellChat to infer ligand-receptor communication. Sub-clustering defined inflammatory CAFs (iCAF), myofibroblast CAFs (mCAF), and macrophage subtypes (M1/M2). GO/KEGG enrichment assessed functional pathways. Multiplex immunofluorescence validated spatial interactions of IL10+ iCAF and IL10RA+ macrophages in patient tissues. An immune-humanized patient-derived xenograft (PDX) mouse model was established to evaluate the therapeutic effect of IL-10 blockade. Single-cell transcriptomic analysis of HGSOC ascites revealed macrophages and cancer-associated fibroblasts as dominant cell populations within the tumour microenvironment. Cell-cell communication analysis identified IL-10-IL-10RA signalling as a prominent interaction pathway linking inflammatory CAFs (iCAFs) with M2-like macrophages. iCAFs displayed elevated IL-10 expression, while M2 macrophages showed increased IL-10RA/IL-10RB expression and were associated with exhausted immune states. Multiplex immunofluorescence confirmed spatial proximity between IL-10+ iCAFs and IL-10RA+ M2 macrophages in tumour tissues. In immune-humanized PDX models, IL-10 blockade with MK-1966 significantly suppressed tumour growth and reduced expression of M2 macrophage markers and proliferation-associated proteins. This study identifies an IL-10-dependent iCAF-M2 macrophage immunoregulatory circuit as a central mechanism driving immune suppression in HGSOC. Targeting the IL-10 pathway effectively reverses M2 polarization and suppresses tumour progression, highlighting IL-10 blockade as a promising therapeutic strategy in ovarian cancer.