BioProject

Rising numbers of patients with cardiovascular diseases and limited availability of donor hearts require new and improved therapy strategies. More...

Rising numbers of patients with cardiovascular diseases and limited availability of donor hearts require new and improved therapy strategies. Human atrial appendage-derived cells (hAACs) are promising candidates for an allogeneic cell-based treatment. In this study, their inductive and modulatory capacity regarding immune responses and underlying key mechanisms were evaluated in vitro. For this, cryopreserved hAACs were analyzed either unstimulated or after stimulation with interferon-gamma by flow cytometry. This revealed the expression of characteristic mesenchymal stromal cell markers (CD29, CD44, CD73, CD166), but also highlighted a predominant negativity for CD90. A low immunogenic phenotype in an inflammatory milieu was shown by lacking expression of co-stimulatory molecules and upregulation of the inhibitory ligands PD-L1 and PD-L2, despite of de novo expression of HLA-DR. Co-cultures of hAACs with allogeneic peripheral blood mononuclear cells, proved the low immunogenic state by absence of induced CD4+ and CD8+ T cell proliferation and activation. However, elevated levels of IL-1β, IL-33 and IL-10 were detectable in those cell culture supernatants. In a second step, the immunomodulatory potential of hAACs was assessed in co-cultures with αCD3/αCD28-activated peripheral blood mononuclear cells. A strong inhibition of T cell proliferation and lowering of pro-inflammatory cytokines (IFNγ, TNFα, TNFβ, IL-17A, IL-2) were observable after pre-stimulation of hAACs with interferon-gamma. Transwell experiments confirmed that mostly soluble factors are responsible for these suppressive effects. We were able to identify indolamin-2,3-dioxygenase (IDO) as a potential key player through a genome-wide gene expression analysis and could demonstrate its involvement in lowered proliferation and induction of apoptosis in T cells. While the application of blocking antibodies against both PD-1 ligands did not affect the immunomodulation by hAACs, 1-Methyl-L-Tryptophan as specific inhibitor of IDO was able to restore proliferation and to lower apoptosis of T cells. In conclusion, hAACs represent a cardiac-derived mesenchymal stromal-like cell type with a high potential for application in allogeneic settings, since they do not trigger T cell responses and even increase their immunomodulatory potential in inflammatory environments. Overall design: Human atrial appendage-derived cells (hAACs) from three different donor were analyzed either untreated or stimulated with IFNγ. Less...