The Impact of Host Diabetes on Corneal Transplant Immunity and Graft Survival

Abstract

Purpose : Diabetes mellitus (DM) represents a risk factor for corneal graft survival when present in hosts; however, the underlying mechanisms remain unknown. We have shown that donor DM increases the immunogenicity of graft-borne antigen-presenting cells (APC) enhancing host immunity and graft failure. Herein, we investigated immunity and graft survival in a DM-recipient mouse model

Methods : Type1 DM (T1D) was induced in BALB/c mice with streptozotocin. Insulin was administered by subcutaneous insulin pellets. Corneal transplantation was performed in 1) T1D, 2) insulin-treated T1D and 3 non-DM (ND) mice. Donor corneas were harvested from ND 1) Cx3cr1^YFPCreER^tdTomato 2) CD11c^GFPDTR transgenic and 3) wild-type (C57BL/6 background) mice. APC were depleted ex vivo in donor corneas with diphtheria toxin and clodronate. Grafted corneas and draining lymph nodes (DLN) were harvested at different time points and assessed for confocal microscopy and flow cytometry. IFN-γ production by alloreactive CD4⁺ Th1 cells was quantified using ELISPOT assay. The functionality of FoxP3⁺ Tregs was evaluated by their capacity to suppress the proliferation of CD4⁺T cells in co-culture. The remaining animals were followed for 8 weeks post-transplantation to assess graft survival

Results : T1D hosts showed 100% graft failure vs. 50% in ND. Transplant immunity in T1D hosts was outlined by 1) enhanced migration of graft-born tdTomato+ APC (p<0.001), 2) increased frequencies of alloreactive IFN-y+ cells in both DLN (p<0.001) and grafted corneas (p<0.001), 3) reduced Treg functionality profiled by expression of FoxP3+ (p<0.01), IL-10 (p<0.01), and TGFB1 (p<0.01), and suppressive capacity (p<0.001), compared to ND hosts. Depletion of donor APC led to 1) lesser host IFN-γ+ CD4+ T cells (p<0.001), 2) abolition of the direct pathway of sensitization compared to non-depleted donors (p<0.001); however, Treg functionality was impaired, and only 20% of allograft survival was observed. Insulin treatment significantly reduced APC migration and sensitization of IFN-y+ cells, while increasing Treg functionality and graft survival (80%)

Conclusions : Our results demonstrate that host DM increases the immunogenicity of donor-derived APC and graft failure. Despite the depletion of graft APC lessened Th1 alloreactivity, graft tolerance, and survival were blunted. Insulin treatment modulates transplant immunity while promoting tolerance and graft survival

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.