Abstract Objectives Systemic sclerosis (SSc)-associated interstitial lung disease (SSc-ILD) is the leading cause of death amongst SSc patients. However, profibrotic factors in SSc-ILD has not been systematically assessed and their working mechanisms remain unclear. Methods We performed an integrated (scRNA-seq) analysis of 17 normal and 17 SSc-ILD lung tissues, using CellChat and Monocle3. Single-cell ATAC sequencing (scATAC-seq) profiles were analyzed by Signac. We performed ELISA to detect specific ligand serum levels using specimens of 55 SSc patients with (n = 32) or without (n = 23) ILD. Bleomycin-induced SSc-associated animal models of pulmonary fibrosis (n = 5) were constructed and used for tissue-level validation using immunofluorescence and immunohistochemistry. Results Integrative scRNA-seq profiles from 17 healthy control and 17 SSc-ILD lung tissues showed a higher intercellular communication flow in SSc-ILD. SPP1/CCL18-positive macrophages and COL1A2 mesenchymal cells positive for MIF or MDK constitute the majority of intercellular communication in SSc-ILD. ELISA showed serum levels of SPP1, MIF, and MDK were increased in SSc-ILD. SPP1 from macrophages generated self-autocrine feedback for CD44-positive macrophages and paracrine activity for ITGB1-positive COL1A2 mesenchymal cells. MIF from COL1A2 mesenchymal cells and SPP1 from macrophages provided co-stimulatory signalling for CD74/CD44-positive macrophages. MDK-SDC2 pairs-mediated autocrine signal accomplished self-management of COL1A2 mesenchymal cells. Moreover, scATAC-seq analysis showed SSc-ILD had higher chromatin accessibility for SPP1 (promoter region, intron 4, and intron 7) and SDC2 (promoter region). Conclusion Ligand-receptor pairs, including SPP1-CD44/ITGB1, MIF-CD74, and MDK-SDC2, constitute a major component of intercellular communication in SSc-ILD. It provided a panoramic view of the pathogenesis of SSc-ILD in a new dimension.
Hu et al. (Tue,) studied this question.