Characterization of the pro-resolving eosinophil subset in human arthritis and its regulation by anti-rheumatic treatment

• Applicants: Professorin Dr. Aline Bozec, Ph.D.; Professor Dr. Georg Schett
• Subject Area: Rheumatology ; Clinical Immunology and Allergology
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 535009434

Rheumatoid arthritis (RA) is a severe inflammatory joint disease with defective resolution. Previously, we demonstrated that allergic asthma can induce resolution of arthritis and that abrogation of eosinophils by anti-IL-5 antibody used in asthma patients can induces flares in RA patients. We have shown that induction of a robust type 2 helper T cell (Th2)/eosinophil (Eos) immune response represents a strong pro-resolving signal in arthritis. Resolving eosinophils (rEos) are constantly present in the joints and contribute to tissue homeostasis, whereas induced eosinophils (iEos) only emerge in response to inflammation, such as during allergic responses in the airways, and exert pro-inflammatory, destructive features. We have also shown that upregulation of resolving eosinophils (rEos) switch classical macrophages into alternative activated macrophages as well as limit neutrophil influx in experimental models of arthritis. In this proposal, we will translate these murine findings into human disease and analyze the functional roles of eosinophils subsets in RA patients naïve or exposed to treatment. While innate immune cells like macrophages and neutrophils in RA have been well characterized following anti-rheumatic drug therapy, nothing is known about the changes of pro-resolving Eos in human arthritis, i.e. during active disease and remission. Our preliminary data using confocal microscopy highlighted that rEos, defined as EPX+ EAR1+ cells, appear specifically in the synovium of RA patients in remission stage. Within this research proposal, we will first phenotypically characterize eosinophil subsets by single cell RNA sequencing in blood of RA patients in the active phase of arthritis or in remission. Next, the expression profile, metabolic states and secretome of rEos and iEos will be delineated in RA patients treated with conventional anti-rheumatic drugs, such as methotrexate, targeted synthetic anti-rheumatic drugs such as JAK inhibitor and biological synthetic anti-rheumatic drugs such as TNF inhibitors. A special emphasis will be put on the comparison of RA patients responding to the drug and those non-responding. Finally, we plan to delineate the pro resolving function of eosinophils on macrophages polarization, which will be completed with the screening of patient’s synovial samples with CyTOF on slide technology and confocal microscopy to localize rEos and iEos within the inflammatory tissue as well as the expression of their associated proteins. Taken together, these results will clarify the cellular and molecular mechanism of rEos in RA patients and will thereby define pro-resolving target molecules in arthritis.

• DFG Programme: Research Grants