Immunoregulatory effects of human dental pulp-derived stem cells on T cells: comparison of transwell co-culture and mixed lymphocyte reaction systems

Background aims. Studies performed using human and animal models have indicated the immunoregulatory capability of mesenchymal stromal cells in several lineages. We investigated whether human dental pulp-derived stem cells (hDP-SC) have regulatory effects on phytohemagglutinin (PHA)-activated CD3(+) T cells. We aimed to define the regulatory mechanisms associated with hDP-SC that occur in mixed lymphocyte reaction (MLR) and transwell systems with PHA-CD3(+) T cells and hDP-SC at a ratio of 1:1. Methods. Proliferation, apoptosis and pro-and anti-inflammatory cytokines of PHA-CD3(+) T cells, the expression of Regulatory T cells (Treg) markers and some regulatory factors related to hDP-SC, were studied in Both transwell and MLR are co-cultures systems. Results. Anti-proliferative and apoptotic effects of hDP-SC were determined in co-culture systems. Elevated expression levels of human leukocyte antigen (HLA)-G, hepatocyte growth factor (HGF)-beta 1, intracellular adhesion molecule (ICAM-1)-1, interleukin (IL)-6, IL-10, transforming growth factor (TGF)-beta 1, vascular adhesion molecule (VCAM)-1 and vascular endothelial growth factor (VEGF) by hDP-SC were detected in the co-culture systems. We observed decreased expression levels of pro-inflammatory cytokines [interferon (IFN)-gamma, IL-2, IL-6 receptor (R), IL-12, Interleukin-17A (IL-17A), tumor necrosis factor (TNF)-alpha] and increased expression levels of anti-inflammatory cytokine [inducible protein (IP)-10] from PHA-CD3(+) T cells in the transwell system. Expression of Treg (CD4(+) CD25(+) Foxp3(+)) markers was significantly induced by hDP-SC in both co-culture systems. We observed apoptosis of PHA-CD3(+) T cells with 24 h using time-lapse camera photographs and active caspase labeling; it is likely that paracrine soluble factors and molecular signals secreted by hDP-SC led this apoptosis. Conclusions. We suggest that hDP-SC have potent immunoregulatory functions because of their soluble factors and cytokines via paracrine mechanisms associated with PHA-CD3(+) T cells, which could contribute to clinical therapies.