Single-cell RNA-seq analysis reveals aberrant CSF1 expression in disease-causing synovial fibroblasts of pigmented villonodular synovitis

Abstract

Objectives: Although the role of the CSF1/CSF1R axis in pigmented villous synovitis (PVNS) has been confirmed, the cells that express CSF1 and CSF1R and the underlying mechanism remain unclear. Single-cell RNA sequencing (scRNA-seq) of PVNS obtained through biopsies depicted the cellular diversity of PVNS, revealed specific CSF1/CSF1R-expressing cells and further identified novel gene expression that is associated with the development of PVNS. Methods: scRNA-seq was performed on tissues obtained from the 6 biopsies of 3 patients with PVNS. Flow cytometry, immunofluorescence and western blot validated the transcriptional results, while co-culture systems revealed the cross talk between fibroblasts and macrophages. Results: 8 subsets of fibroblasts and 5 subsets of macrophages were identified from the synovium of patients with PVNS and were found to be related to distinct signaling pathways. The cellular components of localized and diffuse PVNS are overall similar. Moreover, the synovium and nodule of PVNS share similar composition. The specific cells expressing CSF1/CSF1R were also identified. Other than that, unique CXCL12+CSF1+ fibroblasts were revealed to attract macrophages as disease-causing synovial fibroblasts, leading to the formation of masses in PVNS. Conclusions: PVNS consists of macrophages, fibroblasts, T cells, endothelial cells and mast cells. Among them, the CSF1-expressing fibroblasts appeared to be tumor-like cells that attract macrophages, subsequently forming tumor-like mass in PVNS. This paves the path for novel treatments of PVNS by targeting CXCL12+CSF1+ fibroblasts and the CXCL12-CXCR4 axis.

Expanding the molecular spectrum of tenosynovial giant cell tumors

“…RNA-seq led to the reclassification of four “ HMGA2::NCOR2 giant cell tumors”. The transcriptional similarities between the CSF1 transcripts and newly identified transcripts suggest an analogous oncogenic activation pathway ( 28 ), illustrated by the efficacy of CSF1 inhibitors in both situations.…”

Comprehensive analysis of the oncogenic and immunological role of FAP and identification of the ceRNA network in human cancers

“…Considering as an essential source of CSF1, we inferred that fibroblasts may be recognized by CSF1R that mainly expressed on the macrophages, thus subsequently recruiting the macrophages. Fibroblast-macrophage interaction that centers around the CSF1-CSF1R signaling axis has already been proved essential in the occurrence and progression of various cancers [ 33 , 34 ]. Moreover, Qi et al found that FAP + CAFs and SPP1 + (secreted phosphoprotein 1) macrophages interacted with each other through chemerin, TGF-β, and IL-1, accompanied by stimulating the formation of immune-excluded desmoplastic structure and limiting the T cell infiltration [ 35 ].…”