1588: Monocyte-derived Macrophages Accumulate in the Lungs in anti-MDA5+ Dermatomyositis with RP-ILD: Proinflammatory and Profibrotic Phenotype Revealed by Single-cell RNA Sequencing

Xiaoya Pei¹, Jia Shi², Yangzhong Zhou², Xiao Zhang², Xiaoman Wang¹, Mingwei Tang², Shuang Zhou², chanyuan wu², Jinmin Peng³, Mengtao Li⁴, xiaofeng Zeng², Jun Liu⁵, Houzao Chen¹ and Qian Wang², ¹State Key Laboratory of Medical Molecular Biology, Department of Biochemistry and Molecular Biology, Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, ²Department of Rheumatology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, ³Medical Intensive Care Unit, State Key Laboratory of Complex Severe and Rare Diseases, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences, Beijing, China, ⁴Peking Union Medical College Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, Beijing, China, ⁵State Key Laboratory of Protein and Plant Gene Research, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking University, Beijing, China

Background/Purpose: Anti-melanoma differentiation-associated gene 5-positive dermatomyositis (anti-MDA5+ DM) is a rare inflammatory autoimmune disease with impressively life-threatening rapid progressive interstitial lung disease (RP-ILD). The mechanism that leads to immune dysfunction and lung injury remains elusive.

Methods: We applied single-cell RNA sequencing to the peripheral blood mononuclear cells (PBMCs) from three anti-MDA5+ DM patients and cells in paired broncho-alveolar lavage fluid (BALF). The datasets of healthy controls are from GSE158055 (PBMC) and GSE14592 (BALF). Flow cytometry and Luminex assay were further applied to validate the results.

Results: A high-quality scRNA-seq dataset composed of 64,565 cells were generated from three anti-MDA5+ DM patients, revealing profound aberrations of various immune compartments and distinct immune responses both in peripheral blood and lungs. We found increased monocytes resembling myeloid-derived suppressor cells (MDSCs), which correlated with inflammatory markers in the blood ofanti-MDA5+ DM patients. While those MDSC-like monocytes showed enhanced activation of type I interferon signaling pathway, they were immune-paralyzed, with downregulation of cytokines and inflammatory gene expressions. In contrast, the lung microenvironmentofanti-MDA5+ DM exhibited overactivation of immune responses, with monocyte-macrophages in BALFs producing massive amounts of cytokines and chemokines. To be more specific, monocyte-derived alveolar macrophages (Mo-AMs) might be the major source triggering the cytokine storm in the lung, with cell ratios and inflammatory expression both significantly elevated inanti-MDA5+ DM patients. The prominent expression of chemokines of Mo-AMs suggested a feed forward loop of immune cell recruitment and inflammatory cascade. Besides, pseudo-time trajectory analysis revealed that recruited Mo-AMs adopt a fibrosis-associated phenotype during the process of differentiation.

Conclusion: Our study comprehensively depicts the dysregulated peripheral and lung immune landscape inanti-MDA5+ DM, and highlights the proinflammatory and profibrotic role of Mo-AMs in the pathogenesis and progression ofanti-MDA5+ DM with RP-ILD, implying that targeting Mo-AMs or blockade of monocyte influx to lung may present an effective strategy.








X. Pei: None; J. Shi: None; Y. Zhou: None; X. Zhang: None; X. Wang: None; M. Tang: None; S. Zhou: None; c. wu: None; J. Peng: None; M. Li: None; x. Zeng: None; J. Liu: None; H. Chen: None; Q. Wang: None.