Rheumatoid arthritis autologous synovial fluid affects the plasticity and function of peripheral and induced T regulatory cells in vitro

• Published in: Immunology letters 2024-06, Vol.267, p.106859-106859, Article 106859
• Main Authors: Kommoju, Vallayyachari, Mariaselvam, Christina Mary, Bulusu, Sree Nethra, Michael, Benita Nancy Reni, Kavadichanda, Chengappa, Thabah, Molly Mary, Negi, Vir Singh
• Format: Article
• Language: English
• Subjects: CBA; Rheumatoid arthritis; Synovial fluid; Th1-like Tregs; Th17-like Tregs; Tregs
• ISSN: 0165-2478; 1879-0542
• DOI: 10.1016/j.imlet.2024.106859

•Tregs and Tregs expressing CXCR3 (Th1-like Tregs) and CCR6 (Th17-like Tregs) were higher in RA synovial fluid as compared to RA peripheral blood.•These Th1-like and Th17-like Treg cell percentages correlated positively with their subset specific cytokines in RA synovial fluid.•In vitro, autologous synovial fluid enhanced the conversion of RA peripheral Tregs (pTregs) and in vitro generated vimentin induced Tregs (iTregsVIM) to Th1-like and Th17-like Treg phenotypes.•Conversion of Tregs to Th1-like and Th17-like Treg phenotypes in the presence of inflammatory milieu compromises the stability as well as the function of pTregs.•A combination of IL-2, Tocilizumab and 5-Azacytidine reduces the conversion of iTregsVIM to Th-like and Th17-like Treg phenotypes but not individually.•Multiple mechanisms besides inflammatory milieu influences the stability of iTregsVIM that can be therapeutically relevant. The synovial fluid (SF) microenvironment in rheumatoid arthritis (RA) may alter the stability and function of Tregs. In the present study, we assessed cytokine levels and percentage of Tregs, Tregs expressing CXCR3 (Th1-like Treg), CCR6 (Th17-like Treg) in RA peripheral blood (PB) and RA-SF using fluorescence cytometry. Effect of autologous SF on plasticity and function of RA-PB Tregs (pTregs; CD4+CD25hiCD127Lo/−) and induced vimentin-pulsed Tregs (iTregsVIM) was assessed in vitro. Cytokines and percentage of Th1-like and Th17-like Tregs were higher in RA-PB than OA-PB; higher in RA-SF than osteoarthritis (OA)-SF. Compared to OA-SF exposed OA-pTregs, RA-SF exposed RA-pTregs showed higher percentage of Th1-like (11% vs 20%) and Th17-like (16% vs 36%) Tregs; higher T-bet (p = 0.0001), RORγ (p = 0.0001) and lower FOXP3 (p = 0.0001) gene expression; and diminished percentage suppression of autologous T effector cells (36% vs 74%). RA-SF exposed iTregsVIM showed increased percentage of Th1-like and Th17-like Tregs compared to iTregsVIM exposed to AB serum (8% vs 0.1%; 21% vs 0.1%). IL-2, Tocilizumab and 5-azacytidine reduced the conversion of iTregsVIM (8% vs 2.4%; 21% vs 6.9%), when used in combination. To conclude, microenvironment in the RA synovial fluid is possibly responsible for conversion of pTregs into Th-like Tregs and their functional loss. A blockade of cytokine receptors and methyl transferases could inhibit Tregs conversion, providing clinical relevance for future Tregs targeting therapies.