Topical interleukin 1 receptor antagonist promotes corneal transplant survival

Pathophysiology of Corneal Endothelial Cell Loss in Dry Eye Disease and Other Inflammatory Ocular Disorders

PURPOSE

Dry eye disease (DED) and other inflammatory ocular disorders have been reported to be associated with decreased corneal endothelial cell density (CECD), however the mechanism of underlying endothelial cell loss remains unknown.

METHODS

We conducted a comprehensive literature search of English-written publications on dry eye disease, corneal endothelial cell loss, Sjögren's syndrome, and Graft Vs Host Disease (GVHD), to review the effects of DED and other inflammatory ocular surface conditions on CECD.

RESULTS

A total of 78 studies were included in our study. Loss of corneal neurotrophic support, cytotoxic stress, and a heightened immune response, all of which may occur secondarily to a common causative agent such as inflammation, are major contributors to reduced CECD.

CONCLUSION

More studies are needed to determine how the interrelated pathways of altered corneal nerve function and upregulated expression of inflammatory activity influence corneal endothelial cell loss.

Clinical progress in MSC-based therapies for the management of severe COVID-19

Considering the high impact that severe Coronavirus disease 2019 (COVID-19) cases still pose on public health and their complex pharmacological management, the search for new therapeutic alternatives is essential. Mesenchymal stromal cells (MSCs) could be promising candidates as they present important immunomodulatory and anti-inflammatory properties that can combat the acute severe respiratory distress syndrome (ARDS) and the cytokine storm occurring in COVID-19, two processes that are mainly driven by an immunological misbalance. In this review, we provide a comprehensive overview of the intricate inflammatory process derived from the immune dysregulation that occurs in COVID-19, discussing the potential that the cytokines and growth factors that constitute the MSC-derived secretome present to treat the disease. Moreover, we revise the latest clinical progress made in the field, discussing the most important findings of the clinical trials conducted to date, which follow 2 different approaches: MSC-based cell therapy or the administration of the secretome by itself, as a cell-free therapy.

Novel adaptation of a running suture technique in a mouse model of corneal transplantation

Several murine models of corneal transplantation have been developed over the years to study the immunopathological processes that lead to the failure of grafted corneas. In all of them, the classic eight interrupted sutures technique is utilized for transplanting the donor cornea on the host bed. However, in clinical practice, a single continuous suture with a single knot is generally performed for corneal transplantation. Here, we describe the adaptation of the single continuous suture technique in a mouse model of corneal transplantation.

Interleukin-1 and Transforming Growth Factor Beta: Commonly Opposing, but Sometimes Supporting, Master Regulators of the Corneal Wound Healing Response to Injury

Purpose

Interleukin (IL)-1α/IL-1β and transforming growth factor (TGF)β1/TGFβ2 have both been promoted as “master regulators” of the corneal wound healing response due to the large number of processes each regulates after injury or infection. The purpose of this review is to highlight the interactions between these systems in regulating corneal wound healing.

Methods

We conducted a systematic review of the literature.

Results

Both regulator pairs bind to receptors expressed on keratocytes, corneal fibroblasts, and myofibroblasts, as well as bone marrow-derived cells that include fibrocytes. IL-1α and IL-1β modulate healing functions, such as keratocyte apoptosis, chemokine production by corneal fibroblasts, hepatocyte growth factor (HGF), and keratinocyte growth factor (KGF) production by keratocytes and corneal fibroblasts, expression of metalloproteinases and collagenases by corneal fibroblasts, and myofibroblast apoptosis. TGFβ1 and TGFβ2 stimulate the development of myofibroblasts from keratocyte and fibrocyte progenitor cells, and adequate stromal levels are requisite for the persistence of myofibroblasts. Conversely, TGFβ3, although it functions via the same TGF beta I and II receptors, may, at least in some circumstances, play a more antifibrotic role—although it also upregulates the expression of many profibrotic genes.

Conclusions

The overall effects of these two growth factor-cytokine-receptor systems in controlling the corneal wound healing response must be coordinated during the wound healing response to injury or infection. The activities of both systems must be downregulated in coordinated fashion to terminate the response to injury and eliminate fibrosis.

Translational Relevance

A better standing of the IL-1 and TGFβ systems will likely lead to better approaches to control the excessive healing response to infections and injuries leading to scarring corneal fibrosis.

Blocking the IL-1 receptor reduces cardiac transplant ischemia and reperfusion injury and mitigates CMV-accelerated chronic rejection

Ischemia-reperfusion injury (IRI) is an important risk factor for accelerated cardiac allograft rejection and graft dysfunction . Utilizing a rat heart isogeneic transplant model, we identified inflammatory pathways involved in IRI in order to identify therapeutic targets involved in disease. Pathway analyses identified several relevant targets, including cytokine signaling by the IL-1 receptor (IL-1R) pathway and inflammasome activation. To investigate the role of IL-1R signaling pathways during IRI, we treated syngeneic cardiac transplant recipients at 1-hour posttransplant with Anakinra, a US Food and Drug Administration (FDA)-approved IL-1R antagonist; or parthenolide, a caspase-1 and nuclear factor kappa-light-chain-enhancer of activated B cells inhibitor that blocks IL-1β maturation. Both Anakinra and parthenolide significantly reduced graft inflammation and cellular recruitment in the treated recipients relative to nontreated controls. Anakinra treatment administered at 1-hour posttransplant to recipients of cardiac allografts from CMV-infected donors significantly increased the time to rejection and reduced viral loads at rejection. Our results indicate that reducing IRI by blocking IL-1Rsignaling pathways with Anakinra or inflammasome activity with parthenolide provides a promising approach for extending survival of cardiac allografts from CMV-infected donors.

Animal models of high-risk corneal transplantation: A comprehensive review

Over the past century, corneal transplantation has become the most commonly performed allogeneic solid tissue transplantation. Although more than 80% of the corneal transplantations have favorable outcomes, immune-mediated rejection continues to be the major cause of failure in well over 50% of graft recipients that have inflamed and vascularized host beds. Over the past two decades, the progress in our understanding of the immunological pathways that mediate graft rejection has aided in the development of novel therapeutic strategies. In order to successfully test the efficacy of these interventions, it is essential to model the immunological processes occurring as a consequence of corneal transplantation. Herein, we have comprehensively reviewed the established animal models used for replicating the immunopathological processes causing graft rejection in high-risk corneal transplantation settings. We have also discussed the practical and technical differences, as well as biological and immunological variations in different animal models.

Is Keratoconus an Inflammatory Disease? The Implication of Inflammatory Pathways

PURPOSE

Keratoconus is considered a non-inflammatory condition. Recently however, increased proinflammatory cytokines have been detected in the tears of keratoconic patients and clinical and immunohistochemical observations reported infiltration of matured dendritic cells and leukocytes. Our laboratory utilized cytokine antibody arrays to elucidate the inflammatory aspects of keratoconus.

METHODS

Protein was extracted from 42 corneal buttons (14 keratoconic and 28 non-keratoconic) and incubated with cytokine antibody arrays scanning 120 cytokines. Mann Whitney U test with a p-value of <0.05 was considered significant.

RESULTS

Pathways for wound healing, neuroprotection, angiogenesis, and inflammation were activated in keratoconic samples with 23 cytokines showing significant elevation. Fifteen were expressed only in keratoconus with 8 cytokines elevated 1.7-42-fold.

CONCLUSION

This study identified elevated inflammatory pathways covering immune responses in keratoconus. Our results support the evidence for inflammatory pathway activation in keratoconus and a possible redefinition of keratoconus as a chronic inflammatory corneal disease.

rhIL-1Ra reduces hepatocellular apoptosis in mice with acute liver failure mainly by inhibiting the activities of Kupffer cells

In clinic, there is still no drug that can significantly improve the survival rate of patients with acute liver failure (ALF). We have confirmed that recombinant human IL-1 receptor antagonist (rhIL-1Ra) significantly improves the survival rate of acetaminophen (APAP)-induced ALF mice by reducing hepatocellular apoptosis. Here, we investigated the mechanism of this and the key target cells of rhIL-1Ra. In vivo, APAP-induced ALF mice were treated with rhIL-1Ra and gadolinium chloride (Gdcl₃), respectively. Survival rates of mice, serum IL-1Ra and IL-1β levels, IL-1 receptor type I (IL-1RI) and CD163 expression in the livers, and the phagocytic activities of Kupffer cells (KCs) were investigated. Additionally, the proliferation of hepatocytes and KCs in co-culture conditions with the serum of ALF mice were investigated in vitro. In this study, a large number of activated large KCs were found in liver lobe region III. Both GdCl₃ and rhIL-1Ra significantly decreased the quantity of large KCs. In all of the mice, hepatocytes and liver non-parenchymal cells other than KCs expressed low levels of IL-1RI, whereas large KCs expressed high levels of IL-1RI. The high ratio of endogenous IL-1Ra/IL-1β was related to rhIL-1Ra function. Additionally, the phagocytic activities of KCs were significantly inhibited by GdCl₃ and rhIL-1Ra. In vitro, the proliferation of hepatocytes in co-culture conditions were significantly inhibited by KCs. In conclusion, large KCs were the key target cells of rhIL-1Ra, and rhIL-1Ra could play its role of reducing hepatocellular apoptosis mainly by inhibiting the activities of KCs.

Vasoactive Intestinal Peptide Promotes Corneal Allograft Survival

Corneal transplantation is the most prevalent form of tissue transplantation. The success of corneal transplantation mainly relies on the integrity of corneal endothelial cells (CEnCs), which maintain graft transparency. CEnC density decreases significantly after corneal transplantation even in the absence of graft rejection. To date, different strategies have been used to enhance CEnC survival. The neuropeptide vasoactive intestinal peptide (VIP) improves CEnC integrity during donor cornea tissue storage and protects CEnCs against oxidative stress-induced apoptosis. However, little is known about the effect of exogenous administration of VIP on corneal transplant outcomes. We found that VIP significantly accelerates endothelial wound closure and suppresses interferon-γ- and tumor necrosis factor-α-induced CEnC apoptosis in vitro in a dose-dependent manner. In addition, we found that intracameral administration of VIP to mice undergoing syngeneic corneal transplantation with endothelial injury increases CEnC density and decreases graft opacity scores. Finally, using a mouse model of allogeneic corneal transplantation, we found for the first time that treatment with VIP significantly suppresses posttransplantation CEnC loss and improves corneal allograft survival.

When Clarity Is Crucial: Regulating Ocular Surface Immunity

The ocular surface is a unique mucosal immune compartment in which anatomical, physiological, and immunological features act in concert to foster a particularly tolerant microenvironment. These mechanisms are vital to the functional competence of the eye, a fact underscored by the devastating toll of excessive inflammation at the cornea - blindness. Recent data have elucidated the contributions of specific anatomical components, immune cells, and soluble immunoregulatory factors in promoting homeostasis at the ocular surface. We highlight research trends at this distinctive mucosal barrier and identify crucial gaps in our current knowledge.

Co-culture of human bone marrow mesenchymal stem cells and macrophages attenuates lipopolysaccharide-induced inflammation in human corneal epithelial cells

Dry eye syndrome (DES) is considered as an ocular surface inflammatory disease. Previous studies have shown inflammation plays an important role in the progression and onset of DES. Co-culture of human bone marrow mesenchymal stem cells (HBMSCs) and macrophages showed immunomodulatory effects via regulation of cytokine regulation. Thus, the aim of this study was to investigate the effect of the interaction of these cells on in vitro DES model. The conditioned media (CM) from macrophages, HBMSCs, and HBMSCs + macrophages were treated to human corneal epithelial cells, which showed significant reduction in IL-1α and IL-1β expression levels in HBMSCs + macrophages group. Moreover, the IL-1 Receptor Antagonist (IL-1RA) was highly expressed in the CM from the HBMSCs + macrophages group. Wounded eyes of mice were treated with IL-1RA at 0-100 ng/mL for 16 h, the wound size was reduced. The results of this study might lead to the identification of new therapeutic targets for DES.

Gene Therapy for Modulation of T-Cell-Mediated Immune Response Provoked by Corneal Transplantation

Corneal transplantation (keratoplasty) is the most common type of tissue replacement in the world. The increased rate of graft rejection after keratoplasty is a central problem for repeated transplantations and in inflamed host corneas. It has been shown that apoptosis of grafted epithelium has a role in corneal allograft rejection. This study focused on the T-cell response triggered in BALB/c mice after allogeneic corneal transplantation with and without anti-apoptotic p35-transduced epithelium. To restrict p35 expression to the epithelial cells, modified allogeneic composite grafts were created. As a result, it was found that the proportion of alloreactive CD4⁺ T cells in postoperatively removed cervical lymph nodes was reduced in the p35-transduced group compared to the allogeneic control group. Diminished priming of the CD4⁺ T cells was supported by significantly decreased proliferation and lower interferon gamma secretion when compared to allogeneic engraftments. The reduced priming of CD4⁺ lymphocytes is the first confirmation of the functionality of p35 in the epithelium of corneal grafts to alter the development of the recipient's immune response. Thus, modification of allosensibilization seems to be a promising tool for reducing graft-mediated immune response following corneal transplantation.

Kinetics of Angiogenic Responses in Corneal Transplantation

PURPOSE

To delineate and compare the kinetics of corneal angiogenesis after high-risk (HR) versus low-risk (LR) corneal transplantation.

METHODS

In mice, intrastromal sutures were placed in the recipient graft bed 2 weeks before allogeneic transplantation to induce angiogenesis and amplify the risk of graft rejection. Control (LR) graft recipients did not undergo suture placement, and thus the host bed remained avascular at the time of transplantation. Graft hemangiogenesis and opacity scores were evaluated for 8 weeks by slit-lamp biomicroscopy. Immunohistochemistry was used to measure CD31 (blood vessels) and LYVE-1 (lymphatic vessels) cells.

RESULTS

Biphasic kinetics were observed for hemangiogenesis in both HR and LR transplant recipients using clinical and immunohistochemical assessments. The biphasic kinetics were composed of a rise-fall (phase 1) followed by a second rise (phase 2) in the degree of vessels. Compared with LR recipients, HR recipients showed higher hemangiogenesis (whole cornea and graft) throughout 8 weeks. Analyzing grafts revealed sustained presence of lymphatic vessels in HR recipients; however, lymphatic neovessels regressed in LR recipients 2 weeks posttransplantation. In contrast to HR host beds, the LR host bed microenvironment cannot sustain the growth of lymphatic neovessels in allografts, whereas it can sustain continued hemangiogenesis.

CONCLUSIONS

The sustained presence of lymphatic vessels in HR host beds can facilitate host immunity against allografts and is likely associated with ongoing higher risk of rejection of these grafts in the long term, suggesting that therapeutic interventions targeting inflammation and lymphatic vessels need to be sustained long term in the HR corneal transplant 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.

Infectious pathogens may trigger specific allo-HLA reactivity via multiple mechanisms

Transplant recipients can be sensitized against allo-HLA antigens by previous transplantation, blood transfusion, or pregnancy. While there is growing awareness that multiple components of the immune system can act as effectors of the alloresponse, the role of infectious pathogen exposure in triggering sensitization and allograft rejection has remained a matter of much debate. Here, we describe that exposure to pathogens may enhance the immune response to allogeneic HLA antigens via different pathways. The potential role of allo-HLA cross-reactivity of virus-specific memory T cells, activation of innate immunity leading to a more efficient induction of the adaptive alloimmune response by antigen-presenting cells, and bystander activation of existing memory B cell activation will be discussed in this review.

Peri- and Postoperative Treatment with the Interleukin-1 Receptor Antagonist Anakinra Is Safe in Patients Undergoing Renal Transplantation: Case Series and Review of the Literature

In patients undergoing solid organ transplantation, the presence of an interleukin-1 (IL-1) driven disease may require the addition of IL-1 inhibiting drugs to the standard immunosuppressive regimen to protect against inflammation and negative graft outcome. Three patients undergoing renal transplantation were treated perioperatively with the interleukin-1 receptor antagonist anakinra. Kidney function increased rapidly in all three and the only complications seen were minor infections. In vitro studies report associations between serum and urinary levels of IL-1β and IL-1 receptor antagonist and negative graft outcome, and studies in animals and two small human trials illustrate a possible protective effect of anti-IL-1 therapy after solid organ transplantation. Peri- and postoperative use of anakinra is safe and effective in patients undergoing renal transplantation.

Proangiogenic Function of T Cells in Corneal Transplantation

BACKGROUND

Corneal neovascularization increases the risk of T cell-mediated allograft rejection. Here, we investigate whether T cells promote angiogenesis in transplantation.

METHODS

Conventional effector T cells were collected from draining lymph nodes of allogeneic or syngeneic corneal transplanted BALB/c mice. T cells were either cocultured with vascular endothelial cells (VECs) to assess VEC proliferation or used in a mixed lymphocyte reaction assay. Messenger RNA (mRNA) expression of vascular endothelial growth factor (VEGF)-A, -C, and VEGF receptor 2 (VEGF-R2) in VECs was assessed by real-time PCR. VEGF-A protein expression was determined by enzyme-linked immunosorbent assay. Flow cytometry was used to analyze VEGF-R2 expression in corneal CD31 cells, and VEGF-A and IFNγ expression in corneal CD4 T cells.

RESULTS

Allogeneic T cells from high-risk (HR) grafted mice induced more VEC proliferation than those from syngeneic transplant recipients (P = 0.03). Vascular endothelial growth factor-A mRNA and protein expression were higher in T cells from draining lymph nodes (P = 0.03 and P = 0.04, respectively) and cornea (protein; P = 0.04) of HR compared with low-risk (LR) grafted hosts. Vascular endothelial growth factor-A, VEGF-C, and VEGF-R2 mRNA expression were increased in VECs when cocultured with T cells from HR transplants compared with LR transplants and naive mice. In addition, IFNγ blockade in T cell/VEC coculture increased VEC proliferation and VEGF-A protein expression, whereas blocking VEGF-A significantly reduced VEC proliferation (P = 0.04).

CONCLUSIONS

Allogeneic T cells from corneal transplant hosts promote VEC proliferation, probably via VEGF-A signaling, whereas IFNγ shows an antiangiogenic effect. Our data suggest that T cells are critical mediators of angiogenesis in transplantation.

Systemic Immunomodulatory Strategies in High-risk Corneal Transplantation

The cornea is the most commonly transplanted tissue in the body. Although corneal grafts generally have high success rates, transplantation onto inflamed and vascularized host beds, or so-called high-risk corneal transplantation, has a high rate of graft rejection. The management of this high-risk corneal transplantation is challenging and involves numerous measures. One of the key measures to prevent graft rejection in these cases is the use of systemic immunosuppressive agents. In this article, we will review the systemic immunosuppressive agents most commonly used for high-risk corneal transplantation, which include corticosteroids, cysclosporine A, tacrolimus, mycophenolate mofetil, and rapamycin. Benefits, risks, and published data on the use of these medications for high-risk corneal transplantation will be detailed. We will also summarize novel immunoregulatory approaches that may be used to prevent graft rejection in high-risk corneal transplantation.

Management of high-risk corneal transplantation

The cornea is the most commonly transplanted tissue in medicine. The main cause of corneal graft failure is allograft rejection. The incidence of graft rejection depends on the presence of high-risk characteristics, most notably corneal neovascularization. Although corneal grafting has high success rates in the absence of these risk factors, high-risk keratoplasty is associated with low success rates because of a high incidence of immune-mediated graft rejection. To improve the survival of high-risk corneal transplantation, various preoperative, intraoperative, and postoperative measures can be considered; however, the key step in the management of these grafts is the long-term use of local and/or systemic immunosuppressive agents. Although a number of immunosuppressive agents have been used for this purpose, the results vary significantly across different studies. This is partly due to the lack of an optimized method for their use, as well as the lack of a precise stratification of the degree of risk in each individual patient. New targeted biologic treatments, as well as tolerance-inducing methods, show promising horizons in the management of high-risk corneal transplantation in near future.

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.

Graft Site Microenvironment Determines Dendritic Cell Trafficking Through the CCR7-CCL19/21 Axis

PURPOSE

The graft site microenvironment has a profound effect on alloimmunity and graft survival. We aimed to study the kinetics and phenotype of trafficking antigen-presenting cells (APC) to the draining lymph nodes (DLNs) in a mouse model of corneal transplantation, and to evaluate the homing mechanisms through which graft site inflammation controls APC trafficking.

METHODS

Allogeneic donor corneas were transplanted onto inflamed or quiescent graft beds. Host- (YAe+) and donor (CD45.1+ or eGFP+)-derived APCs were analyzed by flow cytometry. Protein and mRNA expression of the CC chemokine receptor (CCR)7 ligands CCL19 and CCL21 were assessed using ELISA and Real-Time qPCR, respectively. Transwell migration assay was performed to assess the effect of DLNs isolated from hosts with inflamed graft beds on mature bone marrow-derived dendritic cells (BMDCs).

RESULTS

We found that inflamed graft sites greatly promote the trafficking of both recipient- and graft-derived APCs, in particular mature CCR7+ CD11c+ dendritic cells (DC). CCL19 and CCL21 were expressed at significantly higher levels in the DLNs of recipients with inflamed graft beds. The supernatant of DLNs from recipients with inflamed graft beds induced a marked increase in mature DC migration compared with supernatant from recipients with quiescent graft beds in a transwell assay. This effect was abolished by neutralizing CCL19 or CCL21. These data suggest that graft site inflammation increases the expression of CCR7 ligands in the DLNs, which promote mature DC homing and allorejection.

CONCLUSIONS

We conclude that the graft site microenvironment plays a critical role in alloimmunity by determining DC trafficking through the CCR7-CCL19/21 axis.

Murine corneal transplantation: a model to study the most common form of solid organ transplantation

Corneal transplantation is the most common form of organ transplantation in the United States with between 45,000 and 55,000 procedures performed each year. While several animal models exist for this procedure and mice are the species that is most commonly used. The reasons for using mice are the relative cost of using this species, the existence of many genetically defined strains that allow for the study of immune responses, and the existence of an extensive array of reagents that can be used to further define responses in this species. This model has been used to define factors in the cornea that are responsible for the relative immune privilege status of this tissue that enables corneal allografts to survive acute rejection in the absence of immunosuppressive therapy. It has also been used to define those factors that are most important in rejection of such allografts. Consequently, much of what we know concerning mechanisms of both corneal allograft acceptance and rejection are due to studies using a murine model of corneal transplantation. In addition to describing a model for acute corneal allograft rejection, we also present for the first time a model of late-term corneal allograft rejection.

Ocular surface rehabilitation: Application of human amniotic membrane in high-risk penetrating keratoplasties

BACKGROUND

Human amniotic membrane is a versatile tool for management of ocular surface disorders. This study evaluates the effect of cryopreserved human amniotic membrane (hAM) on one-year survival of penetrating keratoplasties (PKP) in high-risk recipients.

METHOD

This is a retrospective noncomparative cohort study of 58 consecutive eyes undergoing PKP with concurrent placement of a self-retained cryopreserved hAM (PROKERA®) at a tertiary care center from January 2009 to July 2010.

RESULTS

Mean patient age was 66.7 ± 17.2 years and 30 (54%) were males. 51 eyes were pseudophakic and one aphakic. 27 eyes were glaucomatous; 24 had glaucoma drainage device and 2 had previous endocyclophotocoagulation. 12 patients had PKP for the first time and 46 had repeat PKP (average number of prior PKP = 1.63 ± 1.1, range: 1-5). Risk factors for graft failure included repeat PKP (79.3%), corneal neovascularization (51.7%), preexisting glaucoma (46.6%), and presence of anterior synechiae (37.9%). Both First Transplant and Repeat Transplant groups had similar survival rates until 6 months after transplant (75% vs 74%, odds ratio = 1.06, p = 1.00). At 12 months, First Transplant group showed a better survival rate (67% vs 43%, odds ratio = 2.60, p = 0.20). Eyes with >3 risk factors had a higher graft failure rate (odds ratio = 5.81, p = 0.003).

CONCLUSION

Survey of the literature suggests that high-risk PKP with concurrent hAM placement demonstrate comparable graft survival. Presence of multiple risk factors is associated with poor survival.

Critical appraisal of loteprednol ointment, gel, and suspension in the treatment of postoperative inflammation and pain following ocular and corneal transplant surgery

Purpose

To review comprehensively the available peer-reviewed published articles in the literature on loteprednol suspension, gel, and ointment in the treatment of ocular inflammation and pain following ocular surgery.

Methods

We conducted a PubMed literature search review of all published articles on keywords associated with loteprednol etabonate and ocular surgery.

Results

A total of 59 peer-reviewed articles were found in the literature. The focus of the majority of the articles was on the safety and efficacy of loteprednol etabonate 0.5% in postoperative control of inflammation and pain following cataract surgery. There were only three articles with a remote association between loteprednol etabonate and keratoplasty.

Conclusion

Lotemax® ointment may also have potential as a first-line anti-inflammatory agent of choice in postoperative settings of strabismus and penetrating glaucoma, and following low-risk penetrating keratoplasty procedures.

Concise review: immunological properties of ocular surface and importance of limbal stem cells for transplantation

Cornea transplantation has been considered to be different from other solid organ transplantation because of the assumed immune-privileged state of the anterior chamber of the eye. Three major lines of thought regarding the molecular mechanisms of immune privilege in the eye are as follows: (a) anatomical, cellular, and molecular barriers in the eye; (b) anterior chamber-associated immune deviation; and (c) immunosuppressive microenvironment in the eye. However, cornea transplants suffer allograft rejection when breached by vascularization. In recent developments, cellular corneal transplantation from cultivated limbal epithelial cells has shown impressive advances as a future therapy. The limbal stem cell niche contains stem cells that promote proliferation and migration and have immunosuppressive mechanisms to protect them from immunological reactions. Limbal stem cells are also noted to display an enhanced expression of genes for the antiapoptotic proteins, a property that is imperative for the survival of transplanted tissues. Further investigation of the molecular mechanisms regulating the immune regulation of limbal stem cells is relevant in the clinical setting to promote the survival of whole corneal and limbal stem cell transplantation.

The experimental treatment of corneal graft rejection with the interleukin-1 receptor antagonist (IL-1ra) gene

PURPOSE

To investigate the protective effects of interleukin-1 receptor antagonist (IL-1ra) gene transfer in a rat model of corneal graft rejection.

METHODS

We constructed a recombinant plasmid (pcDNA3.1-hIL-1ra) with high IL-1ra expression in eukaryotic cells. Using a Wistar-SD rat model of corneal graft rejection, we examined the effects of IL-1ra in vivo after cationic polymer jetPEI-mediated nonviral gene delivery. Four groups were included: negative controls (group I, n = 20), pcDNA3.1-hIL-1ra corneal stromal injection (group II, n = 34), pcDNA3.1-hIL-1ra anterior chamber injection (group III, n = 34), and 500 µg/ml IL-1ra protein subconjunctiva injection (group IV, n = 20). IL-1ra expression after transfection was evaluated by real-time polymerase chain reaction (RT-PCR) and western blotting. The rejection indices of corneal grafts were analysed in the different groups. The expression levels of transforming growth factor β1 (TGF-β1), inflammatory chemokines including RANTES, interleukin-1 (IL-1) and the numbers of CD4+ and CD8+ T cells in the grafts were determined by biochemical assays at different time points after corneal transplantation.

RESULTS

Various degrees of inflammatory cell infiltration and graft neovascularisation were observed by histopathology. After injecting the pcDNA3.1-hIL-1ra plasmid into the cornea, IL-1ra mRNA and protein expression was detected in the corneal stroma and reached a peak on day 3. The graft survival curves indicated that the corneal transparency rates of grafts in the IL-1ra gene-treated group and the IL-1ra protein-treated group were higher compared with the untreated group (P<0.05). During the period of acute rejection, TGF-β1, RANTES, IL-1α and IL-1β levels in the grafts in the IL-1ra treatment groups were lower than the control group (P<0.05). CD4+ and CD8+ T cell counts were reduced significantly in the corneal grafts of groups II, III and IV compared with group I (P<0.05).

CONCLUSION

Interleukin-1 receptor antagonist (IL-1ra) gene transfer treatment inhibits graft rejection after corneal transplantation through the downregulation of immune mediators.

Strategies for local gene therapy of corneal allograft rejection

Penetrating keratoplasty is the most common type of tissue transplant in humans. Irreversible immune rejection leads to loss of vision and graft failure. This complex immune response further predisposes future corneal transplants to rejection and failure. A diverse armamentarium of surgical and pharmacologic tools is available to improve graft survival. In this review, we will discuss the various gene therapeutic strategies aimed at potentiating the anterior chamber-associated immune deviation to extend graft survival.

Sinomenine can prolong high-risk corneal graft survival in a rat model

AIMS

To study the role of sinomenine (SIN) in prolonging high-risk corneal graft survival in rats.

METHODS

All recipients were randomly assigned to SIN, cyclosporine A (CsA), SIN plus CsA and control groups. IL-2, IL-10, Fas-Fas ligand and CD4(+)CD25(+)FoxP3(+) T cells in peripheral blood were detected. In addition, rat corneal grafts' survival times were recorded.

RESULTS

Survival time was 15.88 ± 5.87 days in the SIN group, 17.67 ± 5.43 days in the CsA group and 20.75 ± 4.77 days in the drug combination group, which were longer survival times than those in the control group (p < 0.05). Compared with the SIN and CsA groups, levels of CD4(+)CD25(+)FoxP3(+) lymphocytes in the control group were decreased (p < 0.05) and were increased in the cotreated group (p < 0.05). IL-2 levels in the SIN-only and CsA-only groups were lower than those in the control group (p < 0.05) and higher than those in the cotreated group (p < 0.05); however, the results for IL-10 were different. The expressions of Fas and Fas ligand were least in the control group.

CONCLUSION

SIN could prolong allograft survival and might have potential clinical usage.

An experimental study on in situ transfection of the interleukin-1 receptor antagonist (IL-1ra) gene into the rat cornea

OBJECTIVE

To investigate the efficiency of the transfection of PEGFP-IL-1ra plasmid via cation polymer mediation (poly-ethylenimine, PEI) by injection into the corneal stroma.

METHODS

Plasmid PEGFP-hIL-1ra recombinants were constructed and transferred into corneal endothelial cells via cation polymer mediation. Plasmid PEGFP-hIL-1ra recombinants and/or PEI-in-vivo were injected into the corneal stroma of Wistar rats. Corneas were harvested at different time points (days 3, 6, 14 and 21) after injection. The expression of IL-1ra after transfection was studied by fluorescence microscopy, transmission electron microscopy, real time polymerase chain reaction (RT-PCR) and immunohistochemistry.

RESULTS

Plasmid PEGFP-hIL-1ra recombinants were constructed successfully. After injection of pEGFP-hIL-1ra plasmid into the cornea, IL-1ra mRNA expression was detected in the corneal stroma and reached a peak on day 6. IL-1ra-GFP granules could be observed in every layer of the cornea in the PEGFP-hIL-1ra recombinant group by transmission electron microscopy, but not in the negative control (PEI-in-vivo) group. P63 immunocytochemical staining in the corneal epithelium was positive in both groups. There was no impairment in the ultrastructure of cells in both groups.

CONCLUSIONS

By direct injection of PEGFP-hIL-1ra into the corneal stroma and mediation by the cation polymer, the IL-1ra gene could be transferred and expressed in corneal tissue efficiently. This may be a novel technique for gene transfection to the cornea in situ.

Innate immunity and resistance to tolerogenesis in allotransplantation

The development of immunosuppressive drugs to control adaptive immune responses has led to the success of transplantation as a therapy for end-stage organ failure. However, these agents are largely ineffective in suppressing components of the innate immune system. This distinction has gained in clinical significance as mounting evidence now indicates that innate immune responses play important roles in the acute and chronic rejection of whole organ allografts. For instance, whereas clinical interest in natural killer (NK) cells was once largely confined to the field of bone marrow transplantation, recent findings suggest that these cells can also participate in the acute rejection of cardiac allografts and prevent tolerance induction. Stimulation of Toll-like receptors (TLRs), another important component of innate immunity, by endogenous ligands released in response to ischemia/reperfusion is now known to cause an inflammatory milieu favorable to graft rejection and abrogation of tolerance. Emerging data suggest that activation of complement is linked to acute rejection and interferes with tolerance. In summary, the conventional wisdom that the innate immune system is of little importance in whole organ transplantation is no longer tenable. The addition of strategies that target TLRs, NK cells, complement, and other components of the innate immune system will be necessary to eventually achieve long-term tolerance to human allograft recipients.

Combined blockade of VEGFR-3 and VLA-1 markedly promotes high-risk corneal transplant survival

PURPOSE. High-risk corneal transplantation refers to grafting performed on inflamed and highly vascularized host beds. It represents a clinical dilemma because the rejection rate can be as high as 90%, irrespective of current treatment modalities. This study was conducted to investigate whether combined blockade of VEGFR-3 (vascular endothelial growth factor receptor-3) and VLA-1 (very late antigen-1) promotes high-risk transplant survival and how it correlates with corneal lymphangiogenesis and hemangiogenesis before and after transplantation. METHODS. High-risk corneal transplantation was performed between normal C57BL/6 (donor) and inflamed BALB/c (recipient) mice. The recipients were randomized to receive intraperitoneal injections of VEGFR-3 and VLA-1-neutralizing antibodies or their controls twice a week for up to 8 weeks after transplantation. Corneal grafts were evaluated by ophthalmic slit-lamp biomicroscopy and analyzed by Kaplan-Meier survival curve. Additionally, whole-mount corneas before and after transplantation were examined by immunofluorescent microscopic assays, and the correlation between lymphatic or blood vessel distribution and transplant outcome was analyzed. RESULTS. The combined blockade markedly promotes 90% survival of high-risk transplants. This strategy specifically modified host beds by selective inhibition of lymphangiogenesis but not hemangiogenesis. A strong correlation was also identified between high-risk transplant rejection and severe lymphatic invasion reaching the donor-graft border. CONCLUSIONS. These novel findings not only provide a new and potentially powerful strategy to promote high-risk transplant survival, they also confirm a critical role of high-degree lymphangiogenesis in mediating high-risk transplant rejection. Results from this study may also shed new light on our understanding and management of other lymphatic- and immune-related diseases in general.

Protective effect of recombinant human IL-1Ra on CCl4-induced acute liver injury in mice

AIM: To evaluate the effects of positive regulation of recombinant human interleukin 1 receptor antagonist (rhIL-1Ra) on hepatic tissue recovery in acute liver injury in mice induced by carbon tetrachloride (CCl₄).

METHODS: Acute liver damage was induced by injecting 8-wk-old mice with CCl₄ 1 mL/kg (1:3 dilution in corn oil) intraperitoneally (ip). Survival after liver failure was assessed by injecting 8-wk-old mice with a lethal dose of CCl₄ 2.6 mL/kg (1:1 dilution in corn oil) ip. Mice were subcutaneously injected with 1 mg/kg recombinant human IL-1Ra twice a day after CCl₄ treatment for 5 d. Serum alanine amino transferase (ALT) and aspartate aminotransferase (AST) levels were determined with a commercial assay kit. Serum IL-1β, IL-1Ra levels were measured by enzyme-linked immunosorbent assay kit. Quantitative real-time polymerase chain reaction was used to determine liver IL-1β, IL-1Ra and IL-6 expression during CCl₄-induced acute liver injury. Liver sections were stained with hematoxylin-eosin. A histology-injury grading system was used to evaluate the degree of necrosis after acute liver injury. Proliferating cell nuclear antigen (PCNA) staining was used to evaluate the role of rhIL-1Ra in promoting hepatocyte proliferation.

RESULTS: Quantitative analysis showed a higher level of IL-6 mRNA expression and reduced serum AST and ALT levels in the livers of the rhIL-1Ra-treated group at the early phase of CCl₄-induced acute liver injury. Histological examination indicated a decrease in centrilobular necrotic areas in mice treated with rhIL-1Ra, and a novel role of rhIL-1Ra in promoting hepatocyte proliferation was also supported by an increase of PCNA staining. All these results, accompanied by a strong survival benefit in rhIL-1Ra-treated vs PBS-treated groups, demonstrated that rhIL-1Ra administration ameliorated the histological damage and accelerated the regeneration and recovery process of the liver.

CONCLUSION: rhIL-1Ra could be further developed as a novel therapeutic agent for the treatment of acute liver injury because of its ability to reduce hepatocellular damage and facilitate liver regeneration.

Cauterization of central cornea induces recruitment of major histocompatibility complex class II+ Langerhans cells from limbal basal epithelium

PURPOSE

The purpose of this study was to investigate the distribution and characterization of Langerhans cells (LCs) in the rat corneal epithelium and to compare the findings with those obtained earlier in the mouse corneal epithelium.

METHODS

Normal and cauterized corneal tissues were excised from Wistar rats, and immunofluorescence staining for major histocompatibility complex (MHC) class II, CD3, CD11c, CD11b, CD45, CD80(B-1), and CD86(B-2) was performed by confocal microscopy. The density of intraepithelial MHC class II+ LCs was quantified.

RESULTS

In the normal corneal epithelium, CD11c+ cells were exclusively distributed in the limbal and peripheral areas. Double staining showed that these cells were CD45 and MHC class II positive and B7 (CD80 or CD86) costimulatory molecules, CD11b, and CD3 negative, exhibiting a dendritic cell phenotype. In cauterized cornea, the expression of MHC class II was significantly enhanced in the limbal basal epithelium. The expression of the activation markers, CD80 and CD86, by MHC class II+ LCs was first present in the limbal basal epithelium as early as 4 hours after corneal inflammation and later throughout the entire corneal epithelium.

CONCLUSIONS

The present study demonstrates for the first time the distribution and characterization of LCs in the rat corneal epithelium, which largely resembles most of those observed in the mouse cornea. In the cauterized cornea, B7+ LCs were first present in the limbal basal epithelium, suggesting that these cells play an important role in corneal inflammatory reaction.

Analysis of inflammatory cytokines in the tears of dry eye patients

PURPOSE

To determine the levels of 8 important cytokines and 1 chemokine in tears of patients with dry eye disease.

METHODS

Tear samples were collected from 7 patients with dry eye disease and 7 healthy volunteers, and impression cytology samples were collected from 3 of the dry eye patients and 3 of the normal controls. Tears were analyzed for the presence of 8 cytokines [interleukin (IL)-2, IL-4, IL-5, IL-6, IL-10, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, IL-1beta] and 1 chemokine (IL-8). The cytokines and chemokine in each tear sample were measured using Invitrogen's Multiplex Bead Immunoassays. The impression cytology samples were analyzed for IL-1beta, IL-6, IL-8, and TNF-alpha mRNA expression using real-time reverse transcriptase polymerase chain reaction anlaysis.

RESULTS

All cytokines and the chemokine measured were significantly increased in the tears of dry eye patients as compared to normal controls. mRNA of all four markers was increased, and the fold increase correlated well with the fold increase of the cytokine concentration found in the tear samples.

CONCLUSION

Tears from dry eye patients contain significantly increased concentrations of cytokines that show correlation to severity of the disease. The upregulation of their respective genes in the conjunctiva suggests that the concentration increase is not the result of evaporative effects, but of overproduction. These findings suggest that cytokines may play an important role in dry eye disease and topical cytokine modulators may be explored as a therapeutic approach to dry eye disease.

Local treatment with alpha-melanocyte stimulating hormone reduces corneal allorejection

BACKGROUND

Corneal grafting is by far the most common form of transplantation. Many grafts suffer from immune rejection and current therapies are associated with many side effects, requiring more effective and safe therapies. alpha-Melanocyte stimulating hormone (alpha-MSH) is a neuropeptide that suppresses host inflammatory defense mechanisms. The purpose of this study was to determine the role of local therapy with alpha-MSH on corneal allograft survival, and the mechanisms by which it may influence graft outcome.

METHODS

Orthotopic corneal transplantation was performed, with recipients receiving subconjunctival alpha-MSH or sham injections twice weekly. Grafts were followed up for 70 days, and graft inflammation/opacification was compared between the two groups in a masked fashion. Graft infiltration and ocular gene expression of select inflammatory cytokines was evaluated at different timepoints. Additionally, allospecific delayed-type hypersensitivity was compared among the groups 3 weeks posttransplantation.

RESULTS

Results showed a significant increase in corneal graft survival in alpha-MSH-treated recipients compared with controls. Although 75% of allografts in alpha-MSH-treated hosts survived at 70 days, 43% survived in controls (P=0.04). Graft infiltration studies demonstrated a significant decrease in the number of mononuclear and polymorphonuclear cells in alpha-MSH-treated mice compared with controls at days 7 and 14 after transplantation. Furthermore, allospecific delayed-type hypersensitivity and gene expression of interferon-gamma and interleukin-2 showed a significantly reduced expression in alpha-MSH-treated mice compared with controls.

CONCLUSIONS

This study provides for the first time, in vivo evidence that treatment with local alpha-MSH may significantly reduce allorejection of orthotopic transplants.

Angiogenesis and Lymphangiogenesis—Implications for Corneal Immunity

It is now widely acknowledged that vasculogenesis and immunogenic inflammation are intricately related in many tissues. However, less understood is to what extent blood (heme) angiogenesis (HA) and lymphangiogenesis (LG) are differentially regulated, and in turn contribute potentially to different aspects of adaptive immunity generated to corneal antigens. Herein, we will provide a brief synopsis of relevant work in this field by focusing particularly on the differential regulation of immunity by these two distinct vasculogenic processes in the cornea, illustrating that in spite of significant redundancies in the mechanisms that induce these vascular processes in the cornea, there are also important distinctions in what aspects of immunity are promoted by them.

Corneal antigen presentation: molecular regulation and functional implications

Presentation of corneal antigens for induction of adaptive immune responses is mediated by corneal antigen-presenting cells (APC), including those that infiltrate the cornea in response to inflammatory stimuli and, to a lesser extent, those that reside in the cornea and up-regulate activation markers in response to inflammation. Significant progress has been made in the last decade in dissecting the molecular mechanisms that mediate APC infiltration into the cornea. However, it has recently been determined that exit of APC out of the cornea is critical for induction of T cells that normally reside outside of the cornea in lymphoid reservoirs. Much less is understood about the molecular regulation of APC egress from the cornea, but our laboratory has recently discovered that APC access to afferent lymphatics and draining lymph nodes requires signaling mediated by VEGFR-3. We describe herein the functional implication of APC trafficking and the prospects for novel immunomodulatory strategies based on regulating APC migration.

Very late antigen 1 blockade markedly promotes survival of corneal allografts

OBJECTIVE

To investigate the role of very late antigen 1 (VLA-1) (also known as integrin receptor alpha(1)beta(1)) in corneal transplantation inflammation and allograft survival.

METHODS

Cell infiltration and vasculogenesis (both angiogenesis and lymphangiogenesis) associated with allodisparate corneal transplantation were assessed in VLA-1-deficient conditions and controls by immunofluorescent microscopic studies. Corneal allograft survival was also assessed after anti-VLA-1 antibody treatment and in VLA-1 knockout recipient mice.

RESULTS

Anti-VLA-1 antibody treatment leads to a profound reduction in the granulocytic, monocytic, and T-cell infiltration after corneal transplantation. In addition, corneal angiogenesis and lymphangiogenesis were both significantly suppressed in VLA-1 knockout mice. Remarkably, universal graft survival was observed in both anti-VLA-1 antibody treatment and knockout mice.

CONCLUSIONS

Very late antigen 1 blockade markedly reduces inflammation and inflammation-induced tissue responses, including vasculogenic responses, associated with corneal transplantation and promotes allograft survival.

CLINICAL RELEVANCE

These studies offer insights into important integrin-mediated mechanisms of corneal transplant-related inflammation and provide possible new integrin-based immunotherapies for transplant rejection.

J2 prolongs the corneal allograft survival through inhibition of the CD4+ T cell-mediated response in vivo

In our previous report, we described a novel non-peptidic organic ligand of CD4 D1, designated J2, as a potential inhibitor of CD4 D1 and thus CD4-dependent T cell responses in vitro. In this work, we further used a murine model of corneal allograft rejection to determine its in vivo immunosuppressive activities. To mimic the situation in high-risk human eyes, the recipient mice corneas were all induced by intrastromal sutures to serve as neovascularized graft beds. J2 was administrated by mouth 3 h before transplantation and thereafter on consecutive 12 days. The results showed that J2 could significantly prolong the median survival time of the corneal allografts, compared to the untreated control group. And the subsequent functional assays, including T cell phenotype analysis, delayed-type hypersensitivity (DTH) and enzyme-linked immunospot (ELISPOT) assays revealed that the immunosuppressive activity of J2 was associated with its inhibitory effects on the CD4(+) T cells and these cells-mediated responses. All these results suggest that J2 is a potential lead for the development of new immunosuppressive agents to prevent the corneal allograft rejection.

Inhibition of inflammatory cytokine production in human corneal cells by dexamethasone, but not cyclosporin

PURPOSE

To evaluate the modulatory effects of anti-inflammatory agents, dexamethasone (Dex) and cyclosporin A (CsA), on the production of cytokines and chemokines by human corneal cells in vitro following stimulation by the pro-inflammatory cytokine after interleukin 1beta (IL-1beta).

METHODS

A human corneal epithelial (HCE) cell line and human corneal fibroblasts (HCFs) were stimulated in culture with IL-1beta and treated with Dex or CsA. The gene expression for selected cytokines and chemokines was determined by reverse transcriptase-polymerase chain reaction (RT-PCR). The secretion of cytokines and chemokines was measured by enzyme-linked immunosorbent assay.

RESULTS

IL-1beta enhanced the mRNA and/or protein levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), IL-8, and monocyte chemotactic protein (MCP)-1 in HCE and IL-6, IL-8, MCP-3, and regulated on T-cell activation expressed secreted (RANTES) in HCFs. Treatment with CsA did not inhibit cytokine production in either HCE or HCFs. In contrast, Dex treatment inhibited the IL-1beta-induced production of GM-CSF, IL-6, IL-8, MCP-3, and RANTES, but not MCP-1.

CONCLUSION

These results show that Dex, but not CsA, has direct immunosuppressive effects on the resident corneal cells, HCE and HCFs. This suggests that the clinically observed immunosuppressive effects of topical CsA are mediated primarily through the immune cells.

Upregulation of CD4+ NKT Cells Is Important for Allograft Survival in Staphylococcal-Enterotoxin-B-Treated Rats after High-Risk Corneal Transplantation

OBJECTIVE

To study the role of CD4+ natural killer T (NKT) cells in staphylococcal-enterotoxin-B (SEB)-treated rats after high-risk corneal transplantation.

METHOD

Fisher 344 donor corneas were transplanted into Lewis recipients. Corneal neovascularization was induced by sutures. All the recipients were randomly divided into 3 groups. The SEB group was intraperitoneally injected with SEB at a concentration of 75 microg/kg. The drug combination group received SEB and dexamethasone at a concentration of 5 mg/ml. The control group received saline buffer. All transplants were evaluated for 30 days. Ten days after transplantation, 3 recipients in each group were sacrificed for immunological study.

RESULT

The survival time of the allografts in the SEB group was 12.50 +/- 1.41 days, much longer than in the control group (7.30 +/- 0.67 days) and the drug combination group (10.38 +/- 3.07 days). The lymphocyte proliferation ability was the weakest and the percentage of CD4+ NKT cells in both the spleen and the mandibular lymph nodes was the highest in the SEB group, while the percentage of CD4+ and CD8+ cells was the lowest in the drug combination group. IL-2 in the aqueous humor and the serum was lower while IL-10 was higher in the SEB group than in the other 2 groups.

CONCLUSION

SEB prolongs allograft survival in rat high-risk corneal transplantation. This effect seems to be mediated by the upregulation of CD4+ NKT cells.

Local thermal injury elicits immediate dynamic behavioural responses by corneal Langerhans cells

Langerhans cells (LCs) represent a special subset of immature dendritic cells (DCs) that reside in epithelial tissues at the environmental interfaces. Although dynamic interactions of mature DCs with T cells have been visualized in lymph nodes, the cellular behaviours linked with the surveillance of tissues for pathogenic signals, an important function of immature DCs, remain unknown. To visualize LCs in situ, bone marrow cells from C57BL/6 mice expressing the enhanced green fluorescent protein (EGFP) transgene were transplanted into syngeneic wild-type recipients. Motile activities of EGFP(+) corneal LCs in intact organ cultures were then recorded by time lapse two-photon microscopy. At baseline, corneal LCs exhibited a unique motion, termed dendrite surveillance extension and retraction cycling habitude (dSEARCH), characterized by rhythmic extension and retraction of their dendritic processes through intercellular spaces between epithelial cells. Upon pinpoint injury produced by infrared laser, LCs showed augmented dSEARCH and amoeba-like lateral movement. Interleukin (IL)-1 receptor antagonist completely abrogated both injury-associated changes, suggesting roles for IL-1. In the absence of injury, exogenous IL-1 caused a transient increase in dSEARCH without provoking lateral migration, whereas tumour necrosis factor-alpha induced both changes. Our results demonstrate rapid cytokine-mediated behavioural responses by LCs to local tissue injury, providing new insights into the biology of LCs.

Interleukin-1 receptor antagonist (IL-1RA) prevents apoptosis in ex vivo expansion of human limbal epithelial cells cultivated on human amniotic membrane

Stem cells of the corneal epithelium have been found to be located exclusively at the anatomical junction between the cornea and the conjunctiva, the limbus. Ex vivo expanded limbal epithelial cells on amniotic membrane (AM) are capable of restoring the corneal surface with limbal stem cell deficiency. Recent studies indicate that intact AM preserves the limbal epithelial phenotype and that distinct epithelial morphology is noted among various culture matrix. However, the factors in response to the interaction between limbal epithelial cells and AM were not well understood. Using Annexin V-fluorescein isothiocyanate staining, we found that human limbal epithelial cells expanded on intact human AM demonstrated fewer apoptotic cells as compared with those on plastic dishes. To identify the anti-apoptotic factors, we performed cDNA microarray analysis and showed that interleukin-1 receptor antagonist (IL-1RA) was overexpressed in cultures on intact AM, which was confirmed by reverse transcription-polymerase chain reaction (RT-PCR), real-time quantitative PCR (Q-PCR) and enzyme-linked immunosorbent assay. In addition, we also noted that the phenomenon of apoptosis detected in cultures on plastic dishes could be reversed by adding recombinant IL-1RA protein into the media, whereas apoptosis of limbal epithelial cells cultivated on intact AM could be induced by exogenous neutralizing IL-1RA neutralizing antibody. These results demonstrated that intact human AM may prevent cultured human limbal epithelial cells from undergoing apoptosis. IL-1RA might be a candidate mediator to exert as an anti-apoptotic molecule during the interaction between human limbal epithelial cells and intact human AM.