Abstract 1199: Endothelial Cell-Matrix Interactions Influence Induction of CD4+CD25+Foxp3+ T Regulatory Cells
Atherosclerosis is an inflammatory disease where dysfunctional endothelial cells (EC) interact with immune cells. CD4+CD25+Foxp3+ T regulatory cells (Treg), recently identified to maintain immune tolerance, control the development and progression of atherosclerosis. The exact mechanisms driving differentiation of Treg in atherosclerosis need to be further elucidated. Alterations in subendothelial matrix architecture are the first response to insults like hyperlipidemia and hyperglycemia. As interactions of EC with the physiologic three-dimensional (3D) extracellular matrix govern important biosecretory and mechanical EC functions we hypothesized that EC-matrix connectivity would influence EC-dependent induction of Treg.
Methods and Results The ability of human aortic EC grown 2D on tissue culture plates to induce Treg and expansion of effector T cells was compared with EC surface-adherent to 3D collagen-based matrices using RT-PCR, flow-cytometry, and ELISPOT. 3D-EC induced 6-fold lower IFN-γ- and IL-2-expressing effector T cells than 2D-EC (p<0.005), whereas induction of Treg was significantly augmented (15±1 vs. 8±1%; p<0.02). The ratio of immunosuppressive:immunoreactive T cells induced by 3D-EC exceeded the ratio induced by 2D-EC 3.5-fold, resulting in a 6-fold reduced T cell proliferation (p<0.001). Expression of programmed death ligand 1 (PDL1) did not differ between 3D- and 2D-EC whereas 3D-EC secreted significantly more IL-10 (512±32 pg/mL) and TGF-β (1042±32 pg/mL; p<0.05) than 2D-EC. Co-incubation with anti-TGF-β or anti-IL-10 suppressed Treg-induction by 3D-EC (11±2 and 10±1; p<0.05).
Conclusion Atherosclerosis is characterized by an imbalance between effector T cells and Treg. Induction of Treg depends on the cytokine milieu with IL-10, TGF-β, and PDL1 as driving forces. We now demonstrate that matrix architecture and EC-matrix interactions are pivotal regulators of EC immunogenicity: 3D environment dampens EC interaction with effector T cells and in vitro immunity to EC via upregulation of Tregs. Our findings might enhance our understanding how EC actively regulate immune responses and provide first insights that EC-matrix interactions might contribute to development and progression of atherosclerosis.