Background Pro-resolving mediators produced by macrophages eliminating apoptotic effector cells during the resolution of inflammation have been shown to stop inflammation, favor tissue repair and return to homeostasis. In immune-mediated inflammatory diseases such as rheumatoid arthritis (RA), one may believe that reintroducing pro- resolving mediators would allow the control of the disease. We have developed a cell culture system of macrophages and apoptotic cells that mimics this phase of resolution. The supernatant of this cell culture system called SuperMApo (SUPERnatant issued from Macrophage APOptotic cell culture) is enriched in pro-resolving factors including anti- inflammatory cytokines like TGF-b.
Objectives to evaluate the effects of SuperMApo in the treatment of collagen-induced arthritis (CIA).
Methods SuperMApo is obtained after 48h of culturing macrophages from peritoneal cavity with apoptotic cells obtained from thymus after X-ray irradiation. CIA was used as a model of RA. SuperMApo (200 μL of 5x concentrated SuperMApo, IV, for 2 days) was injected in score 8 CIA mice. The effect of SuperMApo was first evaluated on APC and T cells from naive mice in terms of phenotype, profile and properties such as maturation of APC before or after TLR-ligand stimulation and T cell polarization assays. Then, SuperMApo was evaluated in vivo in CIA mice.
Results Macrophages, cDC and pDC submitted to SuperMApo demonstrated robust insensitivity to TLR ligand-induced activation, particularly in terms of co-stimulatory molecules expression. Spleen cells cultured with SuperMApo demonstrated a strong Treg increase. This was confirmed using naive CD4+CD25– T cells cultured in the presence of SuperMApo showing Foxp3 expression. CIA mice received 2 injections of SuperMApo (over 48h) and demonstrated a significant long term decrease of CIA (joint score before and after SuperMApo: 8–10 and 1–4, respectively; sustained response to 60 days). This clinical improvement was associated with a higher suppressive function of Treg. Treg transfer from mice treated by SuperMApo to arthritic mice induced joint improvement. Finally, we tested SuperMApo effect on PBMC issued from 4 patients with RA, with and without TLR ligand activation. Our results were that monocytes from 3 patients showed a decreased inflammatory phenotype after overnight exposure to SuperMApo (CD80, CD86, CD40 and HLA-DR expression).
Conclusions these data demonstrated that macrophages eliminating apoptotic cells produced pro-resolving mediators affecting APC properties therefore allowing the control of arthritis in the CIA model.
Disclosure of Interest None declared