Interaction among activated lymphocytes and mesenchymal cells through podoplanin is critical for a high IL-17 secretion

Abstract

BackgroundDuring chronic inflammation, immune cells, notably Th17 cells, infiltrate the inflammatory site and interact with local mesenchymal cells. Applied to rheumatoid arthritis (RA), the aim is to study the interactions between synoviocytes and peripheral blood mononuclear cells (PBMC) with a focus on the Th17 pathway and to identify a mechanism which leads to high IL-17 secretion with an interest on podoplanin.MethodsPBMC from healthy donors and RA patients were co-cultured with RA synoviocytes during 48 h, in the presence or not of phytohemagglutinin. An antibody against podoplanin was used in co-culture. Cytokine production (IL-6, IL-1β and IL-17) was measured by ELISA and cell staining (CD3, CD4, IL-17 and podoplanin) by flow cytometry.ResultsIn control conditions, IL-6 and IL-1β production was increased in PBMC-synoviocyte co-culture compared to PBMC alone (p = 0.02). No additional effect was observed with PBMC activation. Flow cytometry analysis showed no difference in the percentage of Th17 cells in activated PBMC alone or with synoviocytes (p = 0.4), indicating that Th17 differentiation requires only T cell activation. Conversely, IL-17 production was highly increased in co-cultures with activated PBMC vs. activated PBMC alone (p = 0.002). Transwell experiments confirm that cell-cell contact was critical for IL-17 secretion. The incubation of either PBMC or synoviocytes with an anti-podoplanin antibody decreased IL-17 secretion by 60 % (p = 0.008).ConclusionsInteractions between resting PBMC and synoviocytes are sufficient to induce IL-6 and IL-1β production. Both PBMC activation and cell interactions are needed to induce a high IL-17 secretion. Podoplanin contributes at the level of both lymphocytes and synoviocytes.

Evaluation of Anti-inflammatory Effects of Steroids and Arthritis-Related Biotherapies in an In Vitro Coculture Model with Immune Cells and Synoviocytes

“…The benefits on clinical symptoms are well established, while the effect at cellular levels is less documented. Our in vitro system demonstrated in previous studies that cell interactions between mesenchymal cells including synoviocytes from RA patients or skin fibroblasts from psoriatic patients and immune cells resulted in massive pro-inflammatory cytokine production as observed in the in vivo situation (14, 15). Our system was used to evaluate the effect of current biotherapies at the cytokine production level.…”

“…Nevertheless, a high IL-17 secretion is only obtained in coculture with activated-PBMC. This model was validated by using an autologous system, that is PBMC and synoviocytes from the same RA patients (14). Using this model, the effect of treatments on cytokine production resulting from cell interactions could be studied (Figure 1).…”

“…These studies showed that cell interactions were critical for massive pro-inflammatory cytokine secretion. The use of an autologous system validated this model as mimicking the in vivo situation (14, 15). …”

Functional significance of the platelet immune receptors GPVI and CLEC-2

“…An increase in EAE severity is seen on deletion of podoplanin or platelet CLEC-2, and EAE is reduced upon overexpression of podoplanin on Th17 cells associated with an increased rate of resolution of inflammation, suggesting that podoplanin is a nonpathogenic marker of Th17 cells and that the podoplanin/CLEC-2 axis promotes resolution (129)(130)(131). In contrast, overexpression of podoplanin on Th17 T cells and fibroblasts correlates with increased inflammation and clinical severity in rheumatoid arthritis (132), showing that the beneficial role of podoplanin is disease dependent.…”

03.02 Evaluation of anti-inflammatory effects of steroids and arthritis-related biotherapies in an in vitro co-culture model with immune cells and synoviocytes

“…Nevertheless, a high IL-17 secretion is only obtained in coculture with activated-PBMC. This model was validated by using an autologous system, that is PBMC and synoviocytes from the same RA patients (14). Using FigUre 1 | Principle of the in vitro coculture model.…”