The impact of corneal allograft rejection on the long-term outcome of corneal transplantation

The purinergic receptor antagonist oxidized adenosine triphosphate suppresses immune-mediated corneal allograft rejection

Adenosine triphosphate (ATP) is released into the extracellular environment during transplantation, and acts via purinergic receptors to amplify the alloimmune response. Here, using a well-established murine model of allogeneic corneal transplantation, we investigated the immunomodulatory mechanisms of the purinergic receptor antagonist oxidized ATP (oATP). Corneal transplantation was performed using C57BL/6 donors and BALB/c hosts. oATP or sterile saline was administered via intraperitoneal injection for 2 weeks postoperatively. Frequencies of CD45⁺ leukocytes, CD11b⁺MHCII⁺ antigen presenting cells (APCs), CD4⁺IFN-γ⁺ effector Th1 cells and CD4⁺Foxp3⁺ regulatory T cells (Tregs) were evaluated by flow cytometry. Slit-lamp microscopy was performed weekly for 8 weeks to evaluate graft opacity and determine transplant rejection. Treatment with oATP was shown to significantly reduce graft infiltration of CD45⁺ leukocytes, decrease APC maturation and suppress effector Th1 cell generation relative to saline-treated control. No difference in Treg frequencies or Foxp3 expression was observed between the oATP-treated and control groups. Finally, oATP treatment was shown to reduce graft opacity and increase graft survival. This report demonstrates that oATP limits the alloimmune response by regulating APC maturation and suppressing the generation of alloreactive Th1 immunity.

Induction of Contrasuppressor Cells and Loss of Immune Privilege Produced by Corneal Nerve Ablation

Purpose

Severing of corneal nerves in preparation of corneal transplantation abolishes immune privilege of subsequent corneal transplants placed into either eye: a phenomenon termed sympathetic loss of immune privilege (SLIP). SLIP is due to the disabling of T regulatory cells (Tregs) by CD11c⁺ contrasuppressor (CS) cells. This study characterized the induction, function, and manipulation of CS cell activity and the effect of these cells on Tregs induced by anterior chamber-associated immune deviation (ACAID).

Methods

CS cells were induced using a 2.0-mm trephine to score the corneal epithelium. CD11c⁺ CS cells were evaluated by adoptive transfer and by their capacity to disable CD8⁺ ACAID Tregs in local adoptive transfer (LAT) of suppression assays. CD11c⁺ cells were deleted from the ocular surface by subconjunctival injection of clodronate-containing liposomes.

Results

CD11c⁺ CS cell were radiosenstive and long lived. As few as 1000 CS cells blocked the suppressive activity of previously generated CD8⁺ ACAID Tregs, indicating that CS cells act at the efferent arm of the immune response. Depletion of resident CD11c⁺ cells at the ocular surface prevented the generation of CS cells.

Conclusions

Corneal nerve injury that occurs during keratoplasty converts ocular surface CD11c⁺ cells into CS cells that block CD8⁺ Tregs, which are induced by introducing antigens into the anterior chamber (i.e., ACAID Tregs). Depletion of CD11c⁺ cells at the ocular surface prevents the generation of CS cells and may be a useful strategy for preventing SLIP and enhancing the survival of second corneal transplants.

Corneal transplant follow-up study II (CTFS II): a prospective clinical trial to determine the influence of HLA class II matching on corneal transplant rejection: baseline donor and recipient characteristics

PURPOSE

To describe a study to determine the influence of HLA class II matching on allograft rejection of high-risk, full-thickness corneal transplants.

METHODS

A prospective, longitudinal, clinical trial (ISRCTN25094892) with a primary outcome measure of time to first clinically determined rejection episode. Tissue typing used DNA-based techniques. Corneas were allocated to patients with ≤2 human leucocyte antigen (HLA) class I antigen mismatches by cohort minimisation to achieve 0, 1 or 2 HLA class II (HLA-DR) antigen mismatches. Transplants were to be followed up at 6 months and then annually on the anniversary of surgery for 5 years. Power calculations estimated a sample size of 856 transplants to detect a 0.1 difference in probability of rejection at 1 year between HLA class II matched and mismatched transplants at the 5% level of significance with 80% power.

RESULTS

To allow for loss to follow-up, 1133 transplants in 980 patients were accrued to the study between 3 September 1998 and 2 June 2011. 17% of transplants had 0 HLA-DR mismatches. The most frequent indication was bullous keratopathy, accounting for 27% of transplants and 54% of the transplants were regrafts. Median waiting time for a matched graft was 3 months. Donor and recipient characteristics were distributed evenly across the study groups.

CONCLUSION

Recruitment to the CFS II has closed with 1077/1133 transplants meeting all the study criteria. Follow-up has been completed and final analysis of the data has started.

TRIAL REGISTRATION NUMBER

ISRCTN25094892 andUKCRNID9871, Pre-results.

Xanthatin inhibits corneal neovascularization by inhibiting the VEGFR2‑mediated STAT3/PI3K/Akt signaling pathway

Alkali burn is one of the main causes of corneal injury. The inflammation and neovascularization caused by alkali burns aggravate corneal damage, resulting in loss of vision. The aim of the present study was to evaluate the efficacy of xanthatin in the treatment of alkali burn-induced inflammation and neovascularization. A CCK-8 assay was used to detect the effects of different concentrations of xanthatin on the proliferation of human umbilical vein endothelial cells (HUVECs). The effects of xanthatin on the migration of HUVECs and the ability of lumen formation were examined using a scratch test and lumen formation assay, respectively. A total of 60 Sprague-Dawley rats were randomly divided into two groups to establish a corneal alkali burn model, and were treated with PBS and xanthatin eye drops four times a day. A slit lamp microscope recorded changes of the cornea at 0, 4, 7, 10 and 14 days, and the inflammatory indices of the cornea and the neovascular area were evaluated. The expression levels of vascular endothelial growth factor (VEGF) and pigment epithelium-derived factor (PEDF) in the cornea under different treatment conditions were detected using immunofluorescence and western blot analysis. In order to investigate the mechanism of xanthatin on the inhibition of inflammation and neovascularization, HUVECs were treated with xanthatin and PBS following VEGF treatment. The subcellular localization of signal transducer and activator of transcription 3 (STAT3) was detected using immunofluorescence. The expression levels of VEGF receptor 2 (VEGFR2), STAT3, phosphoinositide 3-kinase (PI3K) and Akt were detected using western blot analysis. The results revealed that xanthatin inhibited the proliferation of HUVECs in a concentration-dependent manner. The migration ability and lumen-forming ability of the HUVECs were also inhibited by xanthatin. Slit lamp microscopy showed that the inflammatory index and the area of neovascularization in the xanthatin-treated group were significantly reduced, compared with those in the PBS treatment group. The xanthatin treatment group exhibited a lower protein expression level of VEGF and increased protein expression level of PEDF, compared with the PBS treatment group. In the VEGF-treated HUVECs, xanthatin significantly decreased the expression levels of p-VEGFR2, phosphorylated (p-)STAT3, p-PI3K and p-Akt. In conclusion, the present study confirmed that xanthatin inhibited corneal neovascularization and inflammation in the alkali burn model, elucidating the underlying mechanisms involved in its protective effects. Therefore, xanthatin may be a novel drug for the treatment of corneal alkali burn.

Comparative immunological study of penetrating and anterior lamellar keratoplasty in a murine model

In lamellar keratoplasty, the diseased part of a cornea is replaced while the healthy tissue remains lamellar keratoplasty has the advantage of better graft survival compared to penetrating keratoplasty (PK). We compared the immunological responses to PK and anterior lamellar keratoplasty (ALK) in a murine model. PK or ALK was performed using C57BL/6 donor grafts and BALB/c recipients, and graft opacity was assessed to evaluate graft rejection up to 8 weeks. We evaluated the immunological responses in both groups, which were not clinically considered as graft failure on postoperative day 21. PK mice showed reduced clinical graft survival compared to ALK mice. The mRNA expression of inflammatory mediators, such as IL-1β, IFN-γ, and granzyme B, in grafted corneas of PK mice, was significantly increased compared to the levels in ALK mice at postoperative day 21. PK led to a higher delayed-type hypersensitivity response and IFN-γ secretion in an in vitro T cell assay from draining lymph nodes (LNs), as compared to ALK. Furthermore, PK showed increased angiogenesis and lymphangiogenesis in grafted corneas compared to ALK and led to greater infiltration of CD3⁺ T cells into grafted corneas and increased frequencies of mature antigen presenting cells (APC; MHC-II^highCD11c + cells) and IL-12 + dendritic cells (DCs) in the draining LNs of transplanted mice. In conclusion, PK results in increased graft rejection compared to ALK through relatively increased neovascularization and lymphangiogenesis, which can induce infiltration of pathologic T cells and mature APC migration into grafted corneas and draining LNs.

Tacrolimus Eye Drops as Adjunct Therapy in Severe Corneal Endothelial Rejection Refractory to Corticosteroids

PURPOSE

To evaluate the safety and efficacy of tacrolimus eye drops as adjunctive therapy in the treatment of severe corneal endothelial rejection after penetrating keratoplasty refractory to corticosteroids.

METHODS

In this prospective interventional case series, 11 eyes of 11 patients assessed for severe corneal endothelial rejection, with an inadequate response to topical, local, and systemic corticosteroids, were treated with either 0.01% or 0.05% tacrolimus eye drops 4 times daily. Improvement in signs of rejection, visual function, and development of complications were monitored.

RESULTS

The duration of steroid treatment before intervention was 8.1 ± 1.4 days (range = 7-11). Patients were subsequently administered topical tacrolimus 0.01% or 0.05% qid. The time to clinical improvement was 10.3 ± 3.4 days (range = 3-17). The time to rejection reversal was 27.8 ± 16.3 days (range = 7-52). After 3 months, 10 patients (90.8%) demonstrated clinical improvement, and complete restoration of graft clarity was achieved in 5 patients (45.4%). In responsive cases, steroid therapy was successfully tapered off after 60.2 ± 19.7 days (range = 36-93). The best spectacle-corrected visual acuity improved from 1.7 ± 0.9 to 0.8 ± 0.5 logMAR (P = 0.0016). Reported side effects included stinging on drop instillation and punctate epithelial keratopathy.

CONCLUSIONS

Tacrolimus eye drops may be able to play an adjunctive therapeutic role in patients with severe corneal endothelial rejection refractory to conventional steroid treatment. Controlled studies are needed to further investigate the role of tacrolimus in this setting.

Alloimmunity and Tolerance in Corneal Transplantation

Corneal transplantation is one of the most prevalent and successful forms of solid tissue transplantation. Despite favorable outcomes, immune-mediated graft rejection remains the major cause of corneal allograft failure. Although low-risk graft recipients with uninflamed graft beds enjoy a success rate ∼90%, the rejection rates in inflamed graft beds or high-risk recipients often exceed 50%, despite maximal immune suppression. In this review, we discuss the critical facets of corneal alloimmunity, including immune and angiogenic privilege, mechanisms of allosensitization, cellular and molecular mediators of graft rejection, and allotolerance induction.

Effect of Corneal Nerve Ablation on Immune Tolerance Induced by Corneal Allografts, Oral Immunization, or Anterior Chamber Injection of Antigens

Purpose

Severing corneal nerves during corneal transplantation does not affect first corneal transplants, but abolishes immune privilege of subsequent corneal allografts. This abrogation of immune privilege is attributable to the disabling of T regulatory cells (T regs) induced by corneal transplantation. The goal of this study was to determine if severing corneal nerves induces the development of contrasuppressor (CS) cells, which disable T regs that impair other forms of immune tolerance.

Methods

Effect of corneal nerve ablation on immune tolerance was assessed in four forms of immune tolerance: anterior chamber-associated immune deviation (ACAID); oral tolerance; corneal transplantation, and intravenously (IV) induced immune tolerance. T regulatory cell activity was assessed by adoptive transfer and by local adoptive transfer (LAT) of suppression assays.

Results

Corneal nerve ablation prevented ACAID and oral tolerance, but did not affect IV-induced immune tolerance. Contrasuppressor cells blocked the action of T regs that were generated by anterior chamber injection, oral tolerance, or orthotopic corneal transplantation. The neuropeptide substance P (SP) was crucial for contrasuppressor activity as CS cells could not be induced in SP-/- mice and the SP receptor inhibitor, Spantide II, prevented the expression of CS cell activity in vivo. Contrasuppressor cells expressed CD11c surface marker that identifies dendritic cells (DC).

Conclusions

The loss of immune privilege produced by corneal nerve ablation following corneal transplantation extends beyond the eye and also affects immune tolerance induced through mucosal surfaces and appears to be mediated by a novel cell population of CD11c+ CS cells that disables T regs.

Scaffold-free tissue engineering of functional corneal stromal tissue

Blinding corneal scarring is predominately treated with allogeneic graft tissue; however, there is a worldwide shortage of donor tissue leaving millions in need of therapy. Human corneal stromal stem cells (CSSC) have been shown produce corneal tissue when cultured on nanofibre scaffolding, but this tissue cannot be readily separated from the scaffold. In this study, scaffold-free tissue engineering methods were used to generate biomimetic corneal stromal tissue constructs that can be transplanted in vivo without introducing the additional variables associated with exogenous scaffolding. CSSC were cultured on substrates with aligned microgrooves, which directed parallel cell alignment and matrix organization, similar to the organization of native corneal stromal lamella. CSSC produced sufficient matrix to allow manual separation of a tissue sheet from the grooved substrate. These constructs were cellular and collagenous tissue sheets, approximately 4 μm thick and contained extracellular matrix molecules typical of corneal tissue including collagen types I and V and keratocan. Similar to the native corneal stroma, the engineered corneal tissues contained long parallel collagen fibrils with uniform diameter. After being transplanted into mouse corneal stromal pockets, the engineered corneal stromal tissues became transparent, and the human CSSCs continued to express human corneal stromal matrix molecules. Both in vitro and in vivo, these scaffold-free engineered constructs emulated stromal lamellae of native corneal stromal tissues. Scaffold-free engineered corneal stromal constructs represent a novel, potentially autologous, cell-generated, biomaterial with the potential for treating corneal blindness. Copyright © 2016 John Wiley & Sons, Ltd.

Bilateral Alterations in Corneal Nerves, Dendritic Cells, and Tear Cytokine Levels in Ocular Surface Disease

This review summarizes the recent literature regarding corneal imaging in human subjects using in vivo confocal microscopy. It also covers the recent literature on corneal immune cells, nerves, and tear cytokine levels in ocular surface diseases as well as corneal immune privilege. The significance of interactions between corneal immune cells and nerves in health, neurotrophic keratopathy, and infectious keratitis is discussed. Furthermore, bilateral alterations of immune cells and nerves in clinically unilateral corneal diseases and the link to changes of tear cytokines or neuropeptide levels in contralateral eyes are described. Recent studies reported increased density and morphologic changes of corneal dendritic cells in ocular surface disease that correlated with a decrease in subbasal nerve and corneal nerve density, suggesting potential interactions between the immune and nervous systems in the cornea. Although the relevance of tear cytokines is poorly understood, tear cytokines might have an important role in the pathogenesis of ocular surface diseases. In humans and experimental animal models, alterations in immune cells, cytokines, and immunomodulatory neuropeptide levels in contralateral eyes might mediate the incidence of bilateral infectious keratitis and loss of immune privilege of the cornea in bilateral corneal transplantation or neurotrophic keratopathy cases. The discovery of bilateral alterations of immune cells and nerves in ocular surface diseases is considered the missing link between the immune and nervous systems in the cornea, and demonstrates how studies of animal models and humans aid our understanding of human corneal disease phenomena.

Low oxygen tension and macromolecular crowding accelerate extracellular matrix deposition in human corneal fibroblast culture

Development of implantable devices based on the principles of in vitro organogenesis has been hindered due to the prolonged time required to develop an implantable device. Herein we assessed the influence of serum concentration (0.5% and 10%), oxygen tension (0.5%, 2% and 20%) and macromolecular crowding (75 μg/ml carrageenan) in extracellular matrix deposition in human corneal fibroblast culture (3, 7 and 14 days). The highest extracellular matrix deposition was observed after 14 days in culture at 0.5% serum, 2% oxygen tension and 75 μg/ml carrageenan. These data indicate that low oxygen tension coupled with macromolecular crowding significantly accelerate the development of scaffold-free tissue-like modules. Copyright © 2016 John Wiley & Sons, Ltd.

Human Corneal Endothelial Cell Cultivation From Old Donor Corneas With Forced Attachment

Human corneal endothelial cells (HCEnCs) are responsible for maintaining the transparency of the cornea. Damaged or diseased HCEnCs may cause blindness. Replacement of the diseased cells with a healthy donor endothelium is the only currently available treatment. Tissue-engineering can serve as an alternative to conventional donor corneal transplantation. Due to the global shortage of donor corneas, a wide interest in the development of cultured graft substitutes and artificial corneas has increased. Availability of the old donor corneas is higher especially for research. Although it can be proposed as a valuable source for cell culture, its less proliferative capability emerges a challenge for the researchers. This article describes the use of hyaluronic acid (HA) in combination with Rho-kinase inhibitor (ROCK) Y-27632 for the cultivation of HCEnCs from older donor corneas (age > 60 years). Four conditions including and excluding HA + ROCK and its effect on early attachment rates and proliferation was studied on forty-eight corneas. It was observed that HCEnCs reach confluence within 10–15 days when cultured with HA + ROCK. This approach improves the efficiency of cell adhesion due to force attachment. HCEnCs from old donor corneas can be cultured using this method which may further lead to cell-based therapy for treating corneal endothelial dysfunction.

The Influence of Donor and Recipient Gender Incompatibility on Corneal Transplant Rejection and Failure

In vascularized organ transplants, gender mismatches have higher rates of immunological rejection. We investigated the influence of gender incompatibility, including H-Y incompatibility, on corneal transplant graft rejection and failure. Patients were included who had undergone a first corneal transplant for keratoconus (KC), Fuchs endothelial dystrophy (FED), pseudophakic bullous keratopathy (PBK), infection and other indications. A Cox regression model was fitted for each indication to determine factors affecting graft failure and rejection at 5 years. The impact of gender, including H-Y, matching was analyzed after accounting for other factors, including known risk factors. Of 18 171 patients, 4314 had undergone a transplant for FED, 4783 for KC, 3669 for PBK, 1903 for infection and 3502 for other disorders. H-Y mismatched (male [M]→female [F]) corneas were at greater risk of graft failure or rejection. For FED, F→F were 40% less likely to fail (p < 0.0001) and 30% less likely to reject (p = 0.01); M→M were 20% less likely to fail (p = 0.04) and 30% less likely to reject (p = 0.01). For KC, M→M matched corneas were 30% less likely to fail (p = 0.05) and 20% less likely to reject (p = 0.01) compared with H-Y mismatches. H-Y antigen mismatched (M→F) patients were at greater risk of rejection or graft failure.

Sequential Bilateral Corneal Transplantation and Graft Survival

PURPOSE

To investigate graft survival and rejection following sequential bilateral corneal transplantation.

DESIGN

Retrospective cohort study.

METHODS

The study included patients with Fuchs endothelial dystrophy (FED), pseudophakic bullous keratopathy (PBK), or keratoconus who had undergone a penetrating keratoplasty (PK), endothelial keratoplasty (EK), or deep anterior lamellar keratoplasty (DALK) between 1999 and 2012. The main cohort included patients who had received a first transplant in both eyes for the same indication and a control cohort patients who had undergone a unilateral first corneal transplant. Main outcome measures were graft rejection or failure at 5 years.

RESULTS

A total of 11 822 patients were included, of whom 9335 had a unilateral and 2487 bilateral corneal transplantation. For patients with FED (P < .005) and KC (P = .03) but not PBK (P = .19), a transplant in the second eye was associated with a 50% reduction in risk of graft failure within 5 years in the first eye (FED: hazard ratio [HR] 0.47, 95% confidence interval [CI]: 0.34-0.64; KC: HR 0.50, 95% CI: 0.24-1.02). For FED this was dependent on the type of transplant (EK: HR 0.30, 95% CI: 0.17-0.52; PK: HR 0.61, 95% CI: 0.42-0.88). We found no association between a transplant in the second eye and a rejection episode in the first eye (KC P = .19, FED P = .39, PBK P = .19).

CONCLUSION

For FED and KC, a transplant in the second eye was associated with a reduced risk of graft failure in the first eye, independent of inter-transplant time. For FED this effect was pronounced following an EK in the first eye, where the risk of failure was reduced by 70%.

E-Selectin Mediates Immune Cell Trafficking in Corneal Transplantation

BACKGROUND

Immune rejection continues to threaten all tissue transplants. Here we sought to determine whether platelet (P)- and endothelial (E)-selectin mediate T cell recruitment in corneal transplantation and whether their blockade can reduce T cell graft infiltration and improve long-term corneal allograft survival.

METHODS

In a murine model of allogeneic corneal transplantation, we used PCR and immunohistochemistry to investigate expression of P- and E-selectin in rejected versus accepted allografts and lymph node flow cytometry to assess expression of selectin ligands by effector T cells. Using P- and E-selectin neutralizing antibodies, we evaluated the effect of blockade on CD4 T cell recruitment, as well as the effect of anti-E-selectin on long-term allograft survival.

RESULTS

The P- (93.3-fold, P < 0.05) and E-selectin (17.1-fold, P < 0.005) are upregulated in rejected versus accepted allogeneic transplants. Type 1 T helper cells from hosts with accepted and rejected grafts express high levels of P-selectin glycoprotein ligand 1 and glycosylated CD43. In vivo blockade of P (0.47 ± 0.03, P < 0.05) and E selectin (0.49 ± 0.1, P < 0.05) reduced the number of recruited T cells compared with IgG control (0.98 ± 0.1). Anti-E-selectin reduced the number of mature antigen-presenting cells trafficking to lymphoid tissue compared with control (6.96 ± 0.9 vs 12.67 ± 0.5, P < 0.05). Anti-E-selectin treatment delayed graft rejection and increased survival compared with control, although this difference did not reach statistical significance.

CONCLUSIONS

In a model of corneal transplantation, P- and E-selectin mediate T cell recruitment to the graft, E-selectin mediates APC trafficking to lymphoid tissue, and blockade of E-selectin has a modest effect on improving long-term graft survival.

Gr-1intCD11b+ myeloid-derived suppressor cells accumulate in corneal allograft and improve corneal allograft survival

We identified the characteristics of myeloid-derived suppressor cells (MDSCs) and investigated their mechanism of induction and their functional role in allograft rejection using a murine corneal allograft model. In mice, MDSCs coexpress CD11b and myeloid differentiation antigen Gr-1. Gr-1⁺CD11b⁺ cells infiltrated allografted corneas between 4 d and 4 wk after surgery; however, the frequencies of Gr-1⁺CD11b⁺ cells were not different between accepted and rejected allografts or in peripheral blood or BM. Of interest, Gr-1^intCD11b⁺ cells, but not Gr-1^hiCD11b⁺ cells, infiltrated the accepted graft early after surgery and expressed high levels of immunosuppressive cytokines, including IL-10, TGF-β, and TNF-related apoptosis-inducing ligand. This population remained until 4 wk after surgery. In vitro, only high dose (>100 ng/ml) of IFN-γ plus GM-CSF could induce immunosuppressive cytokine expression in Gr-1^intCD11b⁺ cells. Furthermore, adoptive transfer of Gr-1^intCD11b⁺ cells reduced T cell infiltration, which improved graft survival. In conclusion, high-dose IFN-γ in allograft areas is essential for development of Gr-1^intCD11b⁺ MDSCs in corneal allografts, and subtle environmental changes in the early period of the allograft can result in a large difference in graft survival.

Progress in Corneal Stromal Repair: From Tissue Grafts and Biomaterials to Modular Supramolecular Tissue-Like Assemblies

Corneal injuries and degenerative conditions have major socioeconomic consequences, given that in most cases, they result in blindness. In the quest of the ideal therapy, tissue grafts, biomaterials, and modular engineering approaches are under intense investigation. Herein, advancements and shortfalls are reviewed and future perspectives for these therapeutic strategies discussed.

High-risk corneal allografts: A therapeutic challenge

Corneal transplantation is the most common surgical procedure amongst solid organ transplants with a high survival rate of 86% at 1-year post-grafting. This high success rate has been attributed to the immune privilege of the eye. However, mechanisms originally thought to promote immune privilege, such as the lack of antigen presenting cells and vessels in the cornea, are challenged by recent studies. Nevertheless, the immunological and physiological features of the cornea promoting a relatively weak alloimmune response is likely responsible for the high survival rate in “low-risk” settings. Furthermore, although corneal graft survival in “low-risk” recipients is favourable, the prognosis in “high-risk” recipients for corneal graft is poor. In “high-risk” grafts, the process of indirect allorecognition is accelerated by the enhanced innate and adaptive immune responses due to pre-existing inflammation and neovascularization of the host bed. This leads to the irreversible rejection of the allograft and ultimately graft failure. Many therapeutic measures are being tested in pre-clinical and clinical studies to counter the immunological challenge of “high-risk” recipients. Despite the prevailing dogma, recent data suggest that tissue matching together with use of systemic immunosuppression may increase the likelihood of graft acceptance in “high-risk” recipients. However, immunosuppressive drugs are accompanied with intolerance/side effects and toxicity, and therefore, novel cell-based therapies are in development which target host immune cells and restore immune homeostasis without significant side effect of treatment. In addition, developments in regenerative medicine may be able to solve both important short comings of allotransplantation: (1) graft rejection and ultimate graft failure; and (2) the lack of suitable donor corneas. The advances in technology and research indicate that wider therapeutic choices for patients may be available to address the worldwide problem of corneal blindness in both “low-risk” and “high-risk” hosts.

Systemic Immunosuppression in High-Risk Penetrating Keratoplasty: A Systematic Review

Cornea transplantation has a high success rate and typically only requires topical immunomodulation. However, in high-risk cases, systemic immunosuppression can be used. We conducted a systematic review on the efficacy and side effects of systemic immunosuppression for high-risk cornea transplantation. The study population was 18 years old or older with a high-risk transplant (two or more clock hours of cornea vascularization or a previous failed graft or a graft needed because of herpes simplex keratitis). A comprehensive search strategy was performed with the help of an information specialist and content experts from ophthalmology. All study designs were accepted for assessment. Level 1 and level 2 screening was performed by two reviewers followed by data abstraction. Forest plots were created whenever possible to synthesize treatment effects. Quality assessment was done with a Downs and Blacks score. From 1,150 articles, 29 were ultimately used for data abstraction. The odds ratios (ORs) for clear graft survival in cyclosporine and controls were 2.43 (95% CI: 1.00 - 5.88) and 3.64 (95% CI: 1.48 - 8.91) for rejection free episodes. Mycophenolate mofetil (MMF) significantly improved the rejection free graft survival rates at 1 year (OR: 4.05, 95% CI: 1.83 - 8.96). The overall results suggested that both systemic cyclosporine and MMF improved 1-year rejection free graft survival in high-risk keratoplasty. Cyclosporine also significantly improved clear graft survival rates at 1 year; however, there were insufficient data to analyze the same in the MMF group. Higher quality studies are needed to understand this issue better.

[Risk factors, clinical presentations, prevention, and treatment of corneal graft rejection]

Corneal transplantation is the most common and successful type of allotransplantation surgery. Post-transplant immune response in keratoplasty is less pronounced than that in other transplantation procedures, which is accounted for by anatomical features of the cornea and, also, its low antigenic potential and active immunosuppression. However, the immune privilege of the cornea can be violated by neovascularization, inflammation, or trauma. Patients who require keratoplasty to restore their sight and whose immune privilege is disturbed, fall into a high-risk group and are likely to demonstrate tissue incompatibility and non-transparent engraftment. Two approaches exist as to how graft rejection can be prevented. One of them involves induction of donor-specific tolerance, the other - non-specific suppression of the recipient's immune response. To avoid tissue incompatibility, measures can be taken to restore the immune privilege of the cornea as well as to induce antigen-specific tolerance, which is considered a promising, thought yet experimental, area of modern transplantology. In clinical practice, one pays most attention to improvement of non-specific immune suppression methods based on interfering in the metabolism of immunocompetent cells. Thus, timely prescriptions and proper immunosuppressive tactics with account to possible risk factors determine the outcome in high-risk patients undergoing corneal transplantation surgery.

Human limbal biopsy-derived stromal stem cells prevent corneal scarring

Conventional allograft therapy for corneal scarring is widespread and successful, but donor tissue is not universally available, and some grafts fail owing to rejection and complications such as endothelial failure. We investigated direct treatment of corneal scarring using autologous stem cells, a therapy that, if successful, could reduce the need for corneal grafts. Mesenchymal cells were expanded from small superficial, clinically replicable limbal biopsies of human cadaveric corneo-scleral rims. Limbal biopsy-derived stromal cells (LBSCs) expanded rapidly in media containing human serum, were highly clonogenic, and could generate spheres expressing stem cell genes (ABCG2, Nestin, NGFR, Oct4, PAX6, and Sox2). Human LBSCs differentiated into keratocytes expressing characteristic marker genes (ALDH3A1, AQP1, KERA, and PTGDS) and organized a thick lamellar stroma-like tissue containing aligned collagen and keratan sulfate proteoglycans when cultured on aligned nanofiber substrata. When engrafted into mouse corneal wounds, LBSCs prevented formation of light-scattering scar tissue containing fibrotic matrix components. The presence of LBSCs induced regeneration of ablated stroma with tissue exhibiting lamellar structure and collagen organization indistinguishable from that of native tissue. Because the limbus can be easily biopsied from either eye of an affected individual and LBSCs capable of corneal stromal remodeling can be expanded under xeno-free autologous conditions, these cells present a potential for autologous stem cell-based treatment of corneal stromal blindness.

Severing corneal nerves in one eye induces sympathetic loss of immune privilege and promotes rejection of future corneal allografts placed in either eye

Less than 10% of corneal allografts undergo rejection even though HLA matching is not performed. However, second corneal transplants experience a threefold increase in rejection, which is not due to prior sensitization to histocompatibility antigens shared by the first and second transplants since corneal grafts are selected at random without histocompatibility matching. Using a mouse model of penetrating keratoplasty, we found that 50% of the initial corneal transplants survived, yet 100% of the subsequent corneal allografts (unrelated to the first graft) placed in the opposite eye underwent rejection. The severing of corneal nerves that occurs during surgery induced substance P (SP) secretion in both eyes, which disabled T regulatory cells that are required for allograft survival. Administration of an SP antagonist restored immune privilege and promoted graft survival. Thus, corneal surgery produces a sympathetic response that permanently abolishes immune privilege of subsequent corneal allografts, even those placed in the opposite eye and expressing a completely different array of foreign histocompatibility antigens from the first corneal graft.

Effects of CD25siRNA gene transfer on high-risk rat corneal graft rejection

BACKGROUND

Corneal graft rejection is the major cause of corneal failures. Previous studies have shown that the CD25 monoclonal antibody can inhibit corneal graft rejection during the acute phase of rejection in rat models. In the current study, we evaluated the safety and efficacy of the topical Entranster™ vector in rat corneal applications and further investigated the effects of CD25siRNA gene transfer on high-risk rat corneal graft rejection.

METHODS

Fluorescence detection, clinical assessment, hematoxylin and eosin (HE), terminal deoxynucleotidyl transferase biotin-dUTP nick end labelling (TUNEL) and CD11b assays were used to evaluate the safety and efficacy of CD25siRNA gene transfer in normal SD rat corneas. Orthotopic corneal transplants were performed in alkali burned SD rats. Corneal recipients were divided into four groups that received different treatments. Clinical assessment, western blotting, quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemistry, HE and transmission electron microscopy (TEM) were performed on all grafts.

RESULTS

Low toxicity, no immunogenicity and high transfection efficiency were observed in rat corneas treated with the Entranster™ vector. Reduced endothelial cell apoptosis, inflammatory cell infiltration and graft neovascularisation were observed in the CD25siRNA treatment groups. The graft survival curves showed that CD25siRNA treatment significantly prolonged graft survival time, with better graft transparency and less graft oedema. Lower CD25 and higher IL-10 expression were detected in the CD25siRNA treatment groups during the study period, and a higher FOXP3 level was found in the CD25siRNA group than in the CD25siRNA-twice group on days 14 and 21 post-operation.

CONCLUSIONS

The Entranster™ vector is an effective vector for corneal gene therapy. CD25 siRNA gene transfer inhibits corneal graft rejection via upregulation of anti-inflammatory molecule expression.

Effect of the TLR2/MyD88/NF-κB axis on corneal allograft rejection after penetrating keratoplasty

PURPOSE

To evaluate the effect of the TLR2 (Toll-like receptor 2)/MyD88/NF-κB axis on the allograft rejection after penetrating keratoplasty (PK).

METHODS

The PK rat models were randomly divided into four groups: allograft group, dexamethasone group, PDTC group and isograft group. The mean survival time (MST) and rejection index of corneal grafts were observed. The immunohistochemical staining of TGF-α was performed on day 15. The messenger RNA (mRNA) and protein expression of TLR2, MyD88 and NF-κB p65 in corneal grafts were detected by reverse transcription-polymerase chain reaction (RT-PCR) and western blotting.

RESULTS

On days 5, 7, 9, 11, 13 and 15, the rejection index in the allograft group was higher than in the other three groups (p < 0.05). The MST in the PDTC group (MST, 23.30 ± 0.42 days, n = 10) and in the dexamethasone group (MST, 24.40 ± 0.50 days, n = 10) were higher than in the allograft group (MST, 14.7 ± 0.70 days, n = 10) (χ(2) = 18.02, p < 0.01; χ(2) = 21.47, p < 0.01). The expression of TNF-α in the PDTC group and in the dexamethasone group decreased compared with the allograft group by immunohistochemistry. On day 15, the mRNA and protein expression of TLR2, MyD88 and NF-κB p65 in the PDTC group and the dexamethasone group were less than in the allograft group (p < 0.05).

CONCLUSIONS

Expression of TLR2, MyD88 and NF-κB p65 in rat corneal graft increased significantly and concurred with the allograft rejection, but were effectively inhibited by the treatment with dexamethasone and PDTC after PK. Dexamethasone could improve corneal allograft survival by the TLR2/MyD88/NF-κB axis. PDTC could suppress corneal graft rejection by inhibiting the activity of NF-κB. The TLR2/MyD88/NF-κB axis maybe a potential therapeutic target for corneal allograft rejection.

Matching for Human Leukocyte Antigens (HLA) in corneal transplantation - to do or not to do

As many patients with severe corneal disease are not even considered as candidates for a human graft due to their high risk of rejection, it is essential to find ways to reduce the chance of rejection. One of the options is proper matching of the cornea donor and recipient for the Human Leukocyte Antigens (HLA), a subject of much debate. Currently, patients receiving their first corneal allograft are hardly ever matched for HLA and even patients undergoing a regraft usually do not receive an HLA-matched graft. While anterior and posterior lamellar grafts are not immune to rejection, they are usually performed in low risk, non-vascularized cases. These are the cases in which the immune privilege due to the avascular status and active immune inhibition is still intact. Once broken due to infection, sensitization or trauma, rejection will occur. There is enough data to show that when proper DNA-based typing techniques are being used, even low risk perforating corneal transplantations benefit from matching for HLA Class I, and high risk cases from HLA Class I and probably Class II matching. Combining HLA class I and class II matching, or using the HLAMatchmaker could further improve the effect of HLA matching. However, new techniques could be applied to reduce the chance of rejection. Options are the local or systemic use of biologics, or gene therapy, aiming at preventing or suppressing immune responses. The goal of all these approaches should be to prevent a first rejection, as secondary grafts are usually at higher risk of complications including rejections than first grafts.

Immunology of Corneal Allografts: Insights from Animal Models

Corneal transplantation stands alone as the most common and successful form of solid organ transplantation. Even though HLA matching and systemic antirejection drugs are not routinely used, 90% of the first time corneal allografts will succeed. By contrast, all other major categories of organ transplantation require HLA matching and the use of systemically administered immunosuppressive drugs. This remarkable success of corneal transplants under these conditions is an example of "immune privilege" and is the primary reason for the extraordinary success of corneal transplantation. A number of dogmas have emerged over the past century to explain immune privilege and the immunobiology of corneal transplantation. Many of these dogmas have been based largely on inferences from clinical observations on keratoplasty patients. The past 30 years have witnessed a wealth of rodent studies on corneal transplantation that have tested hypotheses and dogmas that originated from clinical observations on penetrating keratoplasty patients. Rodent models allow the application of highly sophisticated genetic and immunological tools for testing these hypotheses in a controlled environment and with experiments designed prospectively. These studies have validated some of the widely held assumptions based on clinical observations and in other cases, previous dogmas have been replaced with new insights that could only come from prospective studies performed under highly controlled conditions. This review highlights some of the key dogmas and these widely held assumptions that have been scrutinized through the use of rodent models of penetrating keratoplasty. This review also makes note of new immunological principles of corneal immunology that have emerged from rodent studies on corneal transplantation that most likely would not have been revealed in studies on corneal transplantation patients.

Endothelial cell changes as an indicator for upcoming allograft rejection following descemet membrane endothelial keratoplasty

PURPOSE

To report early, specific changes in donor endothelial cell morphology as a predictor of an upcoming allograft rejection after Descemet membrane endothelial keratoplasty (DMEK).

DESIGN

Retrospective, observational case series.

METHODS

Out of a cohort of 500 eyes that underwent DMEK at a tertiary referral center, 7 eyes developed typical clinical signs of an allograft rejection. Specular microscopy images before, during, and after the rejection episode were analyzed and compared with a case-control group of 49 asymptomatic DMEK eyes that matched baseline characteristics of the rejection group. Endothelial cell morphology was evaluated by subjective scoring (range 1-5) in a masked fashion as well as by an objective comparison of endothelial cell density, cell size, coefficient of variation, and hexagonality in rejection vs control eyes.

RESULTS

Subjective scores (median) were higher before and after rejection (2.5 and 5, respectively) than in the DMEK control group (2.0 and 2.5, respectively) at comparable time points (P = .0230 and P = .0005, respectively). Endothelial cell density also differed before (P = .0106) and after rejection (P = .0240), while hexagonality differed before (P = .0499) but not after rejection (P = .1767).

CONCLUSION

Our study suggests that allograft rejection may not be an acute event, but rather a slow-onset immune response. Early, specific changes in endothelial cell morphology were found to "announce" an upcoming allograft rejection. If so, monitoring donor endothelium after DMEK or other forms of keratoplasty may be used to anticipate a rejection episode and/or to prevent an allograft rejection from clinically manifesting itself.

Mesenchymal stem cell therapy promotes corneal allograft survival in rats by local and systemic immunomodulation

Mesenchymal stem cells (MSCs) are being investigated extensively due to their ability to dampen immune responses. Here, we tested the ability of MSCs from three distinct sources to prolong rat corneal allograft survival. A fully allogeneic rat cornea transplant model (DA to LEW) was used. Recipient rats received 1 × 10(6) MSCs (syn [LEW], allo [DA] or third-party [Wistar Furth]) intravenously 7 days before transplantation and again on the day of transplantation (day 0). A high percentage of untreated and syn-MSC treated allografts were rejected (80% and 100%, respectively). Preactivation of syn-MSCs with interferon gamma also failed to prolong allograft survival. Conversely, corneal allograft survival was significantly prolonged in allo-MSC treated (90%) and third-party MSC treated (80%) allograft recipients. Flow cytometric analysis revealed less infiltrating natural killer T cells in corneas of both allo- and third-party MSC treated animals, coupled with a higher proportion of splenic CD4+Foxp3+ regulatory T cells, compared to controls. In the case of allo- and third-party MSCs, results from a delayed-type hypersensitivity assay clearly showed that hypo-responsiveness was specific for corneal donor-associated allo-antigens. Thus, allo- and third-party MSC treatment prolongs corneal allograft survival by suppressing peripheral immune responses and promoting an intragraft immunoregulatory milieu.

Effects of topical sphingosine-1-phosphate 1 receptor agonist on corneal allograft in mice

PURPOSE

The aim of this study was to compare the antirejection effects of topical selective sphingosine-1-phosphate 1 receptor (S1P1) agonist and cyclosporine A (CsA) on the acceptance of a transplanted, allogeneic cornea graft in a murine animal model.

METHODS

Fifty-six BALB/c mice were randomly divided into 4 groups. All the mice received corneal grafts from 28 C57BL/6 donors. Experimental recipients were treated with 0.25%, 0.5% S1P1 agonist suspension eye drops or 1% CsA eye drops 4 times a day after the corneal graft was performed. Controls received no treatment. The corneal grafts were imaged and evaluated with clinical scoring. The excised corneal sections 14 days after transplantation were stained using hematoxylin-eosin for histopathological evaluation. CD86+ and MHC-II+ dendritic cells in corneal samples were identified by immunohistochemical staining. The expression of mRNA in the cornea was evaluated using real-time quantitative PCR for interleukin-2, interferon-gamma, and cytotoxic T-lymphocyte antigen 4.

RESULTS

Corneal graft survival was prolonged by treatment with 0.5% S1P1 agonist and 1% CsA (P < 0.01, respectively) when compared with that in the control in clinical scoring. In addition, topical application of 0.5% S1P1 increased the cytotoxic T-lymphocyte antigen 4 mRNA expression of the corneal grafts. There were significant differences observed with 0.5% S1P1 and agonist 1% CsA (P < 0.01, respectively) when compared with the values of the control group in histology scoring.

CONCLUSIONS

Topical 0.5% S1P1 agonist is as effective as 1% CsA, and both can effectively prolong the survival of corneal allografts in mice.

COST-EFFECTIVENESS OF HUMAN LEUKOCYTE ANTIGEN MATCHING IN PENETRATING KERATOPLASTY

Background: The matching of favorable human leukocyte antigen (HLA) combinations is rarely performed in penetrating keratoplasty procedures for primary prophylaxis of immune reactions. However, clinical studies suggest that the incidence of graft rejection decreases substantially when patients receive favorably matched grafts. Objective: The aim of this study was to assess the cost-effectiveness of HLA matching for patients undergoing penetrating keratoplasty in everyday clinical practice. Methods: In the absence of a randomized controlled clinical trial, we used administrative data from the Freiburg University Eye Hospital in Germany. Our study population consisted of all patients who underwent their first keratoplasty between 11/2003 and 01/2010 and for whom information on HLA histocompatibility was available. We used propensity score matching to estimate a causal effect of favorable HLA matching, parametric survival regression techniques to predict graft survival and expert opinion to model incremental cost for HLA matching. Because the availability of favorable HLA histocompatibility ultimately depends on the patients' HLA phenotype, we modeled the incremental cost-effectiveness ratio (ICER) as a function of the probability that a patient will receive a favorably matched HLA, and used expert opinion to set a point estimate. Results: We predicted that corneal grafts with favorable HLA matching were associated with improved rejection-free graft survival time (more than 1,000 days). We estimated the incremental cost of HLA matching at EUR 1,200 and the ICER at EUR 4.62 per additional day of graft survival. Conclusions: The ICER of HLA matching is acceptable, given the high cost of alternative treatment and the shortage of corneal donors in Germany.

A comparison of lamellar and penetrating keratoplasty outcomes: a registry study

OBJECTIVES

To investigate changing patterns of practice of keratoplasty in Australia, graft survival, visual outcomes, the influence of experience, and the surgeon learning curve for endothelial keratoplasty.

DESIGN

Observational, prospective cohort study.

PARTICIPANTS

From a long-standing national corneal transplantation register, 13 920 penetrating keratoplasties, 858 deep anterior lamellar keratoplasties (DALKs), and 2287 endokeratoplasties performed between January 1996 and February 2013 were identified.

METHODS

Kaplan-Meier functions were used to assess graft survival and surgeon experience, the Pearson chi-square test was used to compare visual acuities, and linear regression was used to examine learning curves.

MAIN OUTCOME MEASURES

Graft survival.

RESULTS

The total number of corneal grafts performed annually is increasing steadily. More DALKs but fewer penetrating grafts are being performed for keratoconus, and more endokeratoplasties but fewer penetrating grafts are being performed for Fuchs' dystrophy and pseudophakic bullous keratopathy. In 2012, 1482 grafts were performed, compared with 955 in 2002, translating to a requirement for 264 extra corneal donors across the country in 2012. Comparing penetrating grafts and DALKs performed for keratoconus over the same era, both graft survival (P <0.001) and visual outcomes (P <0.001) were significantly better for penetrating grafts. Survival of endokeratoplasties performed for Fuchs' dystrophy or pseudophakic bullous keratopathy was poorer than survival of penetrating grafts for the same indications over the same era (P <0.001). Visual outcomes were significantly better for penetrating grafts than for endokeratoplasties performed for Fuchs' dystrophy (P <0.001), but endokeratoplasties achieved better visual outcomes than penetrating grafts for pseudophakic bullous keratopathy (P <0.001). Experienced surgeons (>100 registered keratoplasties) achieved significantly better survival of endokeratoplasties (P <0.001) than surgeons who had performed fewer grafts (<100 registered keratoplasties). In the hands of experienced, high-volume surgeons, endokeratoplasty failures occurred even after 100 grafts had been performed.

CONCLUSIONS

More corneal transplants, especially DALKs and endokeratoplasties, are being performed in Australia than ever before. Survival of DALKs and endokeratoplasties is worse than the survival of penetrating grafts performed for the same indications over the same timeframe. Many endokeratoplasties fail early, but the evidence for a surgeon learning curve is unconvincing.

Short-term azithromycin treatment promotes cornea allograft survival in the rat

Background

Any inflammatory response following corneal transplantation may induce rejection and irreversible graft failure. The purpose of this study is to analyze the anti-inflammatory effect of azithromycin (AZM) following experimental keratoplasty in rats.

Methods

Corneal transplants were performed between Fisher-donor and Lewis-recipient rats. Recipients were postoperatively treated three times daily with AZM, miglyol, ofloxacin or dexamethasone eye drops. As an additional control, AZM was applied following syngeneic keratoplasty. Furthermore, short-term treatments with AZM for seven days perioperatively or with AZM only three days prior to the transplantation were compared to appropriate controls. All transplants were monitored clinically for opacity, edema, and vascularization. Infiltrating CD45⁺, CD4⁺, CD8⁺, CD25⁺, CD161⁺ and CD163⁺ cells were quantified via immunohistochemistry.

Results

AZM significantly promoted corneal graft survival compared with miglyol or ofloxacin treatment. This effect was comparable to topical dexamethasone. No adverse AZM effect was observed. Histology confirmed a significant reduction of infiltrating leukocytes. The short-term application of AZM for three days prior to transplantation or for seven days perioperatively reduced corneal graft rejection significantly compared with the controls.

Conclusions

Along with antibiotic properties, topical AZM has a strong anti-inflammatory effect. Following keratoplasty, this effect is comparable to topical dexamethasone without the risk of steroid-induced adverse effects. Short-term treatment with AZM three days prior to the transplantation was sufficient to promote graft survival in the rat keratoplasty model. We therefore suggest further assessing the anti-inflammatory function of topical AZM following keratoplasty in humans.

Topical 0.03% tacrolimus preventing rejection in high-risk corneal transplantation: a cohort study

BACKGROUND/AIMS

The present study aims to identify the rate of rejection and safety of 0.03% tacrolimus eye drops associated with 1% prednisolone in a topical formulation, comparing them with the use of 1% prednisolone eye drops alone in patients with high-risk corneal transplantation.

METHODS

Retrospective cohort study with 72 patients (72 eyes) who underwent more than one penetrating keratoplasty (PK) in the same eye or had severe chemical burn between 2004 and 2011 in the department of cornea and external disease of the Clinical Hospital of Porto Alegre, Brazil. We compared the records of 36 patients that performed unilateral PK and received only 1% prednisolone eye drops between May 2004 and July 2008, with 36 patients that received 0.03% tacrolimus eye drops in addition to 1% prednisolone between August 2008 and August 2011.

RESULTS

The mean follow-up of the group exposed to tacrolimus was 23.1 months and 24.0 in the prednisolone alone group. The demographics, intraoperative and initial indications for first PK were similar between groups, as well as the number of regrafts performed. Intraocular pressure (IOP) was not statistically different among groups. Regarding irreversible rejections, topical tacrolimus showed greater protection: only seven grafts (19.4%) lost transparency against 16 (44.4%) in the 1% prednisolone alone group (p <0.05).

CONCLUSIONS

Topical 0.03% tacrolimus was effective in preventing irreversible rejection in patients with high-risk corneal transplantation without increasing IOP.

Topical application of soluble CD83 induces IDO-mediated immune modulation, increases Foxp3+ T cells, and prolongs allogeneic corneal graft survival

Modulation of immune responses is one of the main research aims in transplant immunology. In this study, we investigate the local immunomodulatory properties of soluble CD83 (sCD83) at the graft-host interface using the high-risk corneal transplantation model. In this model, which mimics the inflammatory status and the preexisting vascularization of high-risk patients undergoing corneal transplantation, allogeneic donor corneas are transplanted onto sCD83-treated recipient animals. This model allows the direct and precise application of the immune modulator at the transplantation side. Interestingly, sCD83 was able to prolong graft survival after systemic application as well as after topical application, which is therapeutically more relevant. The therapeutic effect was accompanied by an increase in the frequency of regulatory T cells and was mediated by the immune-regulatory enzyme IDO and TGF-β. In vitro, sCD83 induced long-term IDO expression in both conventional and plasmacytoid dendritic cells via autocrine or paracrine production of TGF-β, a cytokine previously shown to be an essential mediator of IDO-dependent, long-term tolerance. These findings open new treatment avenues for local immune modulation after organ and tissue transplantation.

Role of T cell recruitment and chemokine-regulated intra-graft T cell motility patterns in corneal allograft rejection

Keratoplasty is the primary treatment to cure blindness due to corneal opacification. However, immune-mediated rejection remains the leading cause of keratoplasty failure. Here, we utilize an in vivo imaging approach to monitor, track, and characterize in real-time the recruitment of GFP-labeled allo-specific activated (Bonzo) T cells during corneal allograft rejection. We show that the recruitment of effector T cells to the site of transplantation determined the fate of corneal allografts, and that local intra-graft production of CCL5 and CXCL9/10 regulated motility patterns of effector T cells in situ, and correlated with allograft rejection. We also show that different motility patterns associate with distinct in vivo phenotypes (round, elongated, and ruffled) of graft-infiltrating effector T cells with varying proportions during progression of rejection. The ruffled phenotype was characteristic of activated effectors T cells and predominated during ongoing rejection, which associated with significantly increased T cell dynamics within the allografts. Importantly, CCR5/CXCR3 blockade decreased the motility, size, and number of infiltrating T cells and significantly prolonged allograft survival. Our findings indicate that chemokines produced locally within corneal allografts play an important role in the in situ activation and dynamic behavior of infiltrating effector T cells, and may guide targeted interventions to promote graft survival.

Clinical Transplantation of Individualized Recipient Serum-Adapted Cornea Reduces the Risk of Graft Rejection after Keratoplasty

Corneal diseases cause severe visual impairment that necessitates corneal transplantation and frequently repetitive procedures due to graft rejection. We tested the hypothesis that exposure of donor corneas to recipient serum-derived factors during eye banking triggers a preoperative adaptation that is beneficial for postoperative tolerance. Donor corneas were incubated in a medium containing human serum (HS) obtained in each case from the prospective graft recipient in order to individually expose the donor cornea to the recipient's serum. All recipient serum-adapted corneas (RSACs) fulfilled the clinical criteria required by the national law and were transplanted successfully. The postoperative ophthalmological examination extended up to 8 years. All RSACs were tolerated by their recipients and did not cause postoperative complications and no rejection. Proteomic analysis of corneas cultivated in culture medium containing either fetal calf serum (FCS) that is routinely used for cornea banking or HS revealed different patterns of proteins. HS-cultured corneas showed a greater proteomic similarity with native human corneas than did the FCS-cultured corneas, indicating a differential nutrification of the cultured corneal tissue by HS-derived factors. The clinical results show for the first time that postoperative complications such as tissue intolerance and graft rejection might be managed if the corneal tissue is individually adapted to the recipient's serum trophic factors. This new donor tissue treatment procedure offers incontrovertible advantages and could be adapted for low-risk eyes as well as other transplantable tissues.