Diabetes mellitus (DM) is one of the most prevalent diseases globally, and its prevalence is rapidly increasing. Most patients with a long-term history of DM present with some degree of keratopathy (DK). Despite its high incidence, the underlying inflammatory mechanism of DK has not been elucidated yet. For further insights into the underlying immunopathologic processes, we utilized streptozotocin-induced mice to model type 1 DM (T1D) and B6.Cg-Lepob/J mice to model type 2 DM (T2D). We evaluated the animals for the development of clinical manifestations of DK. Four weeks post-induction, the total frequencies of corneal CD45⁺CD11b⁺Ly-6G⁻ myeloid cells, with enhanced gene and protein expression levels for the proinflammatory cytokines TNF-α and IL-1β, were higher in both T1D and T2D animals. Additionally, the frequencies of myeloid cells/mm² in the sub-basal neural plexus (SBNP) were significantly higher in T1D and T2D compared to non-diabetic mice. DK clinical manifestations were observed four weeks post-induction, including significantly lower tear production, corneal sensitivity, and epitheliopathy. Nerve density in the SBNP and intraepithelial terminal endings per 40x field were lower in both models compared to the normal controls. The findings of this study indicate that DM alters the immune quiescent state of the cornea during disease onset, which may be associated with the progressive development of the clinical manifestations of DK.

Highly inflamed and neovascularized corneal graft beds are known as high-risk (HR) environments for transplant survival. One of the primary factors leading to this rejection is reduction in the suppressive function of regulatory T cells (Treg). Our results show that myeloid-derived suppressor cells (MDSC) counteract interleukin-6-mediated Treg dysfunction by expressing interleukin-10. Additionally, MDSC maintain forkhead box P3 stability and their ability to suppress IFN-γ⁺ Th1 cells. Administering MDSC to HR corneal transplant recipients demonstrates prolonged graft survival via promotion of Treg while concurrently suppressing IFN-γ⁺ Th1 cells. Moreover, MDSC-mediated donor-specific immune tolerance leads to long-term corneal graft survival as evidenced by the higher survival rate or delayed survival of a second-party C57BL/7 (B6) graft compared to those of third-party C3H grafts observed in contralateral low-risk or HR corneal transplantation of BALB/c recipient mice, respectively. Our study provides compelling preliminary evidence demonstrating the effectiveness of MDSC in preventing Treg dysfunction, significantly improving graft survival in HR corneal transplantation, and showing promising potential for immune tolerance induction.

After transplantation, Th1-mediated immune rejection is the predominant cause of graft failure. Th1 cell sensitization occurs through complex and context-dependent interaction among antigen-presenting cell subsets, particularly CD11b ⁺ DCs (DC2) and CD103 ⁺ DCs (DC1). This interaction necessitates further investigation in the context of transplant immunity. We used well-established preclinical models of corneal transplantation and identified distinct roles of migratory CD103 ⁺ DC1 in influencing the outcomes of the grafted tissue. In recipients with uninflamed corneal beds, migratory CD103 ⁺ DC1 demonstrate a tolerogenic phenotype that modulates the immunogenic capacity of CD11b ⁺ DC2 primarily mediated by IL-10, suppressing alloreactive CD4 ⁺ Th1 cells via the PD-L1/PD-1 pathway and enhancing Treg-mediated tolerance via αvβ8 integrin–activated TGF-β1, thus facilitating graft survival. Conversely, in recipients with inflamed and vascularized corneal beds, IFN-γ produced by CD4 ⁺ Th1 cells induced migratory CD103 ⁺ DC1 to adopt an immunostimulatory phenotype, characterized by the downregulation of regulatory markers, including αvβ8 integrin and IL-10, and the upregulation of IL-12 and costimulatory molecules CD80/86, resulting in graft failure. The adoptive transfer of ex vivo induced tolerogenic CD103 ⁺ DC1 (iDC1) effectively inhibited Th1 polarization and preserved the tolerogenic phenotype of their physiological counterparts. Collectively, our findings underscore the essential role played by CD103 ⁺ DC1 in modulating host alloimmune responses.

Objectives: In this study, we establish a protocol for evaluating the outcomes of endothelial keratoplasty, including graft survival, rejection, or failure. Additionally, we also evaluate the alloimmune response in graft recipients. Methods: We performed EK using C57BL/6 (allogeneic) and BALB/c (syngeneic) as donors and BALB/c mice as recipients. Slit-lamp examination and optical coherence tomography were performed for clinical evaluations for 16 weeks post-procedure. Criteria for the assessment of corneal opacity were established and the animals were graded weekly. Additionally, we assessed corneal endothelial cell density by harvesting the corneas and staining with zonula occludens-1 (ZO-1). Lastly, lymph nodes were collected, and CD4⁺ T cells were MACS-sorted and co-cultured with syngeneic or allogeneic antigen-presenting cells (APCs) to assess the IFN-γ expression levels by alloreactive Th1 cells (ELISPOT) in response to the direct (donor) or indirect (host) pathways of sensitization. Results: We observed graft failure in four animals, including irreversible corneal opacity, graft detachment, and anterior synechiae in the first four weeks. The remaining animals were graded between 0 and 5 as per the established criteria. The total and graft corneal thickness and endothelial cell density progressively worsened with a higher grade of corneal opacity. The direct allosensitization of Th1 cells was significantly higher in mice with a higher grade of corneal opacity. At 16 weeks follow-up, the grafts remained stable with low opacity scores in syngeneic EK recipients; however, the opacity scores were higher and variable in allogeneic EK recipients. Conclusions: These findings establish a standardized protocol to assess the graft outcomes in a murine model of EK. Furthermore, we delineate the underlying immunological pathway that contributes to the immune-mediated rejection of grafts in this model.

Purpose: To compare graft survival and alloimmune responses in murine endothelial keratoplasty (EK) versus penetrating keratoplasty (PK) and to elucidate the immunological mechanisms that underlie the differential graft outcomes. Methods: Allogeneic EK and PK were performed in BALB/c recipient mice using fully disparate C57BL/6 donors; syngeneic EK recipients served as controls. Graft clarity was monitored over 16 weeks by slitlamp biomicroscopy and scored using standardized opacity grading. Anterior segment optical coherence tomography (AS-OCT) was used to measure central corneal thickness. Graft survival was assessed using Kaplan–Meier analysis. Immunohistochemistry and confocal microscopy were performed to evaluate corneal endothelial cell (CEnC) integrity through ZO-1 staining. T-cell–mediated alloimmunity was assessed using intracellular IFN-γ staining (flow cytometry) and ELISPOT assays targeting both direct and indirect antigen presentation pathways. Results: PK allografts exhibited significantly higher corneal opacity and lower survival (50%) than allogeneic EK grafts (71.4%, P < 0.0001). AS-OCT showed that corneal edema was highest in rejected PK grafts at 4 weeks and in rejected EK grafts at 16 weeks, with EK displaying a more gradual increase in thickness. Flow cytometry revealed significantly greater frequencies of IFN-γ ⁺ CD4 ⁺ T cells in PK recipients compared with EK recipients ( P < 0.001). ELISPOT assays demonstrated a more robust Th1 response in PK through both the direct and indirect sensitization pathways. Corneal endothelial cell (CEnC) density was significantly reduced in rejected EK and PK grafts compared with their respective accepted counterparts ( P < 0.01), whereas CEnC density was comparable between accepted EK and PK grafts. Conclusions: EK grafts exhibit higher graft survival rates and significantly reduced activation of host T-cell responses compared with PK grafts, which may be attributed to lower frequencies of graft-borne antigen presenting cells, thus resulting in a milder Th1-mediated immune response.

Background: To report the first case of traumatic globe rupture after non-Descemet stripping automated endothelial keratoplasty (nDSAEK) with scleral suture fixation of intraocular lens (IOL). Case presentation: A 71-year old male was referred to our hospital with reduced vision in his left eye. He underwent cataract surgery in his left eye about 10 years ago. At presentation, slit-lamp examination of his left eye showed aphakic bullous keratopathy. We performed nDSAEK with scleral suture fixation of IOL. The surgical outcome was favorable. At 5 years after nDSAEK, he sustained globe rupture in his left eye from a fall. Slit-lamp examination demonstrated wound dehiscence and iris prolapse beneath the conjunctiva. However, the transplanted endothelium and Descemet’s membrane was attached completely to the recipient cornea, and there was no dislocation of the implanted IOL. No abnormal findings were observed in the posterior segment. We performed wound suturing and iris reconstruction. After 45 months, recipient and donor cornea retained clarity, and his visual acuity was 20/25. Conclusions: We encountered a patient with traumatic globe rupture after nDSAEK. It can be presumed that traumatic wound dehiscence after DSAEK is better visual outcome than traumatic wound dehiscence after conventional PKP. DSAEK might be resistant to traumatic injury because of the minimal incision than PKP. Key words: Descemet’s stripping automated endothelial keratoplasty, traumatic globe rupture, corneal transplantation