Y. Matsubara1, J. Liu1, L. Gonzalez1, A. Fereydooni1, J. Langford1, J. Gorecka1, S. Lee1, M. Gao1, X. Gao1, R. Taniguchi1, B. Yatsula1, A. Dardik1 1Yale university School of Medicine,Vascular Biology & Therapeutics,New Haven, CT, USA
Introduction:
Vascular remodeling during arteriovenous fistula (AVF) maturation is characterized by inflammation with infiltration of T-cells and macrophages. Although T-cells and M1 macrophages exacerbate classical inflammation, M2 macrophages play an important role in AVF maturation to reduce inflammation and promote wall thickening. Although T-cells induce cytokines to activate macrophages, little is known about T-cell regulation of macrophages during AVF maturation. We hypothesized that T-cells are necessary to activate M2 macrophages to promote vascular wall thickening during AVF maturation.
Methods:
We used the mouse aorta-inferior vena cava AVF model. Cyclosporine (5 mg/kg, subcutaneous injection daily) was used to suppress T-cell activity. T-cell and macrophage infiltration was assessed by immunofluorescence. Vascular wall thickening was assessed by elastin van Gieson stain. TGM2 and CD206 were assessed as markers of M2 macrophages and iNOS and TNF-α were assessed for M1 macrophages.
Results:
T-cells were present in the vascular wall at baseline with maximal infiltration at day 3 (day 0, 9.0 cells/hpf; day 3, 35.3 cells/hpf; day 7, 17.3 cells/hpf; day 21, 3.3 cells/hpf; n=3; p<0.05 (ANOVA)). Macrophages had maximal wall infiltration at day 7 (day 0, 1.0cells/hpf; day 3, 11.3 cells/hpf; day 7, 13.0 cells/hpf; day 21, 1.3 cells/hpf; n=3, p<0.05).
Cyclosporine significantly suppressed infiltration of both CD4+ T-cells (2.2 vs 8.75 cells/hpf; n=3; p<0.05 (t-test)) and CD8+ T-cells (5.1 vs 12.7 cells/hpf; n=3; p<0.05) compared with control vehicle (day 7). At day 21, there was less wall thickening in AVF treated with cyclosporine compared with control AVF (7.6 µm vs. 13.1 µm; n=4-5; p<0.01; t-test, Figure). Cyclosporine significantly inhibited accumulation of TGM2+ macrophages (3.0 vs 13.3 cells/hpf; n=3, p<0.01) and CD206+ macrophages (6.8 vs 14.5 cells/hpf; n=3; p<0.01), but not iNOS+ macrophages (1.5 vs 3.2 cells/hpf; n=3, p=0.07) or TNF-α+ macrophages (0.3 vs 0.3; n=3; p=0.83).
Conclusion:
Cyclosporine is associated with reduced vascular wall thickening as well as less T-cell infiltration and M2 macrophage accumulation in the vascular wall during AVF maturation. These results suggest that T-cells have a critical role during AVF maturation to promote M2 macrophage accumulation and vascular wall thickening.
