CD8⁺ T Cells Negatively Modulate Ischemia-Induced Angiogenesis in Mice

Angiogenesis-related therapeutic approaches to peripheral arterial disease (PAD) deserve attention. CD8⁺ T cells play important roles in human pathobiology, and we investigated the involvement of cytotoxic CD8⁺ T cells in angiogenesis in response to ischemic stress. We also examined the mechanism of a component of green tea catechins, epigallocatechin-3-gallate (EGCG), which facilitates vascular regeneration in mice. Male 8-week-old wild-type [(CD8a^+/+) and interferon-gamma (IFN-γ^+/+)] knockout (CD8a^-/- and IFN-γ^-/-) mice were subjected to unilateral hindlimb ischemic surgery and then loss-of-function studies by blood flow, molecular, and immunostaining analyses at several time points. Post-ischemic surgery CD8a^+/+ mice were treated with EGCG for the evaluation of its vasculoprotective effect. Ischemic stress increased CD8a⁺ T cells and IFN-γ in blood and/or ischemic muscles. A serial laser Doppler blood-flow analysis demonstrated a higher recovery of the ischemic/normal blood-flow ratio in CD8a^-/- mice throughout the follow-up period compared to CD8a^+/+ mice. On postoperative day 14, CD8a^-/- ischemic muscles showed increased capillary density, vascular endothelial growth factor, p-ERK1/2 and decreases in oxidative stress production and NLRP3 and caspase-1 proteins, as well as the levels of matrix metalloproteinase-2/9, cathepsin S/K, mac-3⁺, and ssDNA⁺ cells in the ischemic muscles. All of these beneficial effects were reproduced in IFN-γ^-/- mice. The vasculoprotection was diminished by the murine recombinant IFN-γ supplementation. EGCG showed efficacy that was comparable to that of CD8a^-/- by modulating the growth signaling and apoptosis in mice. IFN-γ depletion rescued impaired aortic ring angiogenic action. In human umbilical vein endothelial cells, EGCG ameliorated 5% T-cell culture medium-induced angiogenic actions, accompanied by reductions of NLRP3 and caspase-1. Our findings indicate that CD8a⁺ T-cell deficiency promotes angiogenesis, and EGCG can reverse the detrimental effects of CD8a⁺ T-cell activation on angiogenesis. These results provide clinically relevant insights into the potential development of immune-inflammatory therapy targeting vascular diseases.