Immunomodulatory effects of dental pulp stem cells on lymphocytes and monocytes from patients with rheumatoid arthritis.

Objective: To investigate the immunomodulatory effects of dental pulp stem cells (DPSCs) on lymphocytes and monocytes from rheumatoid arthritis (RA) patients unresponsive to conventional synthetic disease-modifying anti-rheumatic drugs (csDMARDs).

Methods: Peripheral blood lymphocytes and monocytes were isolated from 12 RA patients unresponsive to csDMARDs. Lymphocytes were activated using anti-CD3/CD28 beads or with CpG ODN 2006, and monocytes with LPS. After 48 hours of co-culture with DPSCs, the expression of 7 immune checkpoints on DPSCs was analysed by flow-cytometry, and 17 cytokines were quantified in the supernatants.

Results: Co-culture of DPSCs with CD3/CD28-activated lymphocytes or LPS-activated monocytes increased the expression of PD-L1, PD-L2, CD155, and Galectin-9 on DPSCs. In contrast, lymphocytes activated with ODN 2006 did not alter immune checkpoint expression. CD80, CD86, and 4-1BBL expression was not induced under any condition. Co-culture with DPSCs reduced levels of sFas-L, IFNγ, sIL-6RA, MIP-1β, TNFα in supernatants of CD3/CD28-activated lymphocytes; and BAFF, sFas-L, IL-1β, sIL-6RA, IL-9, IL-17A, IL-18, IL-23, M-CSF, perforin, TNFα in supernatants of LPS-activated monocytes. IL-6 and IP-10 levels increased in all experimental conditions, while IL-9 increased in ODN 2006- and CD3/CD28-stimulated lymphocyte cultures. DPSCs showed differential effects depending on the activation status of lymphocytes and monocytes.

Conclusions: The overexpression of inhibitory immune checkpoints by DPSCs may contribute to their immunomodulatory effects. DPSCs modulated a broader range of cytokines in monocyte supernatants compared to lymphocytes.