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Jia Yin, Chunyi Shao, Maryam Tahvildari, Reza Dana; Differential Contribution of Regulatory T cells Derived from Low-risk vs. High-risk Transplants to Corneal Angiogenesis. Invest. Ophthalmol. Vis. Sci. 2018;59(9):3341.
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© ARVO (1962-2015); The Authors (2016-present)
Corneal neovascularization is the most important prognosticator for graft survival. Regulatory T cells (Tregs) are critical in maintaining immune quiescence in corneal transplants, but their role in regulating corneal angiogenesis is unknown. We have previously reported that Tregs in high-risk transplants have impaired immunoregulatory functions, compared to those in low-risk transplants. Here we investigated the differential contribution of Tregs derived from low-risk (LR) vs. high-risk (HR) transplants to the regulation of corneal angiogenesis.
CD4+ CD25+ Foxp3+ Tregs were isolated from the ipsilateral draining lymph nodes of graft recipient BALB/c mice after either low-risk (avascular host bed) or high-risk (vascularized host bed) allogeneic corneal transplantation using C57BL/6 donors. The frequencies of VEGF-A+ and IFN-gamma+ Tregs were determined using flow cytometry. Tregs were cultured, and the concentration of VEGF-A in the supernatant was determined using ELISA. Vascular endothelial cells (VEC) were co-cultured with Tregs, and VEC proliferation was determined using BrdU incorporation assay. To determine the effect of Tregs on corneal angiogenesis in vivo, corneal neovascularization was induced by suture placement, and isolated Tregs were adoptively transferred to mice via the tail vein. The vascularized area was photographed and analyzed.
Compared to Tregs derived hosts of low-risk transplants, those from high-risk graft recipients had higher frequencies of IFN-gamma+ cells (mean±SD, 6.4±0.76 in LR vs. 9.5±0.85 in HR, P=0.012), and comparable frequencies of VEGF-A+ cells (5.9±0.74 in LR vs. 6.7±0.36 in HR, P=0.31). VEGF-A level in the supernatant of cultured Tregs derived from high-risk graft recipients was 56% lower than that from low-risk graft recipients (P=0.006). Compared to Tregs derived from low-risk graft recipients, those from high-risk graft recipients resulted in a significant decrease in VEC proliferation in vitro (P=0.029) and corneal neovascularization in vivo (vascularized area: 57.7%±3.0 in LR vs. 33.12%±3.7 in HR, P=0.0001).
Regulatory T cells identified in high-risk graft recipients, despite their immunosuppressive dysfunction, are more anti-angiogenic than the Tregs in low risk graft recipients. Higher ratio of IFN-gamma/VEGF-A may be one of the underlying mechanisms.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.
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