CD4+CD25- T-Cell-Secreted IFN-γ Promotes Corneal Nerve Degeneration in Diabetic Mice.

PURPOSE: This study aimed to explore the relationship between corneal nerve degeneration and elevated dendritic cells (DCs) in diabetic keratopathy. METHODS: Corneas from diabetic and healthy mice were analyzed using single-cell RNA sequencing. Corneal nerve density and DC and T-cell infiltration were quantified through whole-mount corneal staining. Freshly isolated mouse trigeminal ganglion (TG) neurons were co-cultured with immature DCs, mature DCs, activated CD8+ T cells, and CD4+CD25- T cells. TG neurite outgrowth was assessed to identify potential effector cells driving corneal nerve degeneration. In addition, interferon-gamma (IFN-γ) and blocking antibodies were used to evaluate their effects on TG neurite outgrowth and corneal nerve degeneration in mice. RESULTS: Compared with age-matched healthy mice, diabetic mice exhibited a significant reduction in corneal nerve density and sensitivity, along with increased infiltration of DCs, CD4+ T cells, and CD8+ T cells. In vitro co-culture experiments revealed that CD4+CD25- T cells, rather than DCs and CD8+ T cells, significantly inhibited TG neurite outgrowth. Among cytokines, elevated IFN-γ in diabetic corneas impaired TG neurite outgrowth and induced corneal nerve degeneration, whereas IL-4 and IL-17 had no such effect. Blocking IFN-γ alleviated CD4+CD25- T-cell-induced inhibition of TG neurite outgrowth and corneal nerve degeneration in diabetic mice. CONCLUSIONS: CD4+CD25- T cells, but not DCs or CD8+ T cells, contribute to corneal nerve degeneration in diabetic mice, a process partially mediated by IFN-γ.