Inhibition of Immunomediators in Periodontal Ligament-Derived MSCs by 25-Hydroxyvitamin-D3
Objectives: Human periodontal ligament-derived mesenchymal stromal cells (hPDL-MSCs) are important in the orchestration of periodontal tissue homeostasis and regeneration. This is mainly achieved by affecting the local immune response via their immunomodulatory abilities, which are activated by inflammatory cytokines, such as interferon (IFN)-γ, tumor necrosis factor (TNF)-α or interleukin (IL)-1β. These cytokines boost the expression of different, mainly immunosuppressive, immunomediators in hPDL-MSCs, such as indoleamine-2,3-dioxygenase 1 (IDO-1), programmed cell death ligand 1/2 (PD-L1/2), cyclooxygenase-2 (PTGS-2) and tumor necrosis factor-inducible gene 6 protein (TSG-6).
Studies already demonstrated that the biological active 1,25-diydroxyvitamin-D3 (1,25-(OH)2-D3) decreased the expression of different immunomediators in hPDL-MSCs. However, no studies examined the influence of 25-hydroxyvitamin-D3 (25-OH-D3), the most abundant 1,25-(OH)2-D3 precursor in the blood, on the immunomediator expression in hPDL-MSCs. Hence, this study investigated the effect of 25-OH-D3 on the expression of different immunomediators in cytokine-treated hPDL-MSCs.
Methods: Primary hPDL-MSCs from five different healthy individuals were treated with 100ng/ml IFN-γ or 10ng/ml TNF-α or 5ng/ml IL-1 β in the absence or presence of 25-OH-D3 (0.1-100nM) for 48 hours. Expression of IDO-1, PD-L1/2, PTGS-2 and TSG-6 were analysed on gene (qPCR) and protein (flow cytometry analysis, ELISA) levels. Additionally, IDO-1 enzymatic activity was determined photometrically.
Results: Expression levels of IDO-1, PD-L1/2, PTGS-2 and TSG-6 were significantly increased by IFN-γ, TNF-α and IL-1β, in the absence of 25-OH-D3. Adding 25-OH-D3 caused a concentration-dependent decline of cytokine-induced immunomediator expression levels at the gene and protein level. A significant decrease was observed starting from 10 nM 25-OH-D3. In the absence of any cytokines, 25-OH-D3 had no significant influence on immunomediator expression in hPDL-MSCs.
Conclusions: These data show that, beside 1,25-dihydroxyvitamin D3, 25-OH-D3 may also inhibit cytokine-boosted immunomediator expression in hPDL-MSCs. This suggests that 25-hydroxyvitamin-D3 also influences local immune responses and consequently may participate in fine-tuning local inflammatory events in periodontal tissues.