Management of high-risk corneal grafts

Nanoparticle-hydrogel composite as dual-drug delivery system for the potential application of corneal graft rejection

Immune rejection remains the major cause of corneal graft failure. Immunosuppressants (such as rapamycin; RAPA) adjunctive to antibiotics (such as levofloxacin hydrochloride; Lev) are a clinical mainstay after corneal grafts but suffer from poor ocular bioavailability associated with severe side effects. In this study, we fabricated a Lev@RAPA micelle loaded cationic peptide-based hydrogel (NapFFKK) as a dual-drug delivery system by integrating RAPA micelles with Lev into a cationic NapFFKK hydrogel to potentially reduced the risk of corneal graft rejection. The properties of the resulting hydrogels were characterized using transmission electronmicroscopy and rheometer. Lev@RAPA micelles loaded NapFFKK hydrogel provided sustained in vitro drug release without compromising their inherent pharmacological activities. Topical instillation of Lev@RAPA micelles loaded NapFFKK hydrogel resulted in the great ocular tolerance and extended precorneal retention over 60 min, thus significantly enhancing the ocular bioavailability of both Lev and RAPA. Overall, such dual-drug delivery system might be a promising formulation for the suppression of corneal graft failure.

Indications and Results of Emergency Penetrating Keratoplasty With Simultaneous Cataract Surgery ("Triple-PKP à Chaud")

PURPOSE

The purpose of this study was to analyze the indications and clinical results of emergency penetrating keratoplasty with simultaneous cataract surgery ("Triple-PKP à chaud").

METHODS

This study included all subjects who underwent Triple-PKP à chaud between 2006 and 2020 at the Department of Ophthalmology, Saarland University Medical Center, Homburg/Saar in Germany. Data obtained from patient records were retrospectively analyzed.

RESULTS

Triple-PKP à chaud was successfully performed in 27 of 29 eyes with a mean age of 66.0 ± 19.9 years. Previous surgery was performed in 20 eyes (69.0%), most frequently amniotic membrane transplantation in 11 eyes (37.9%) and previous keratoplasty in 9 eyes (31.0%). The most common indication was infectious keratitis (62.1%). In 27 subjects (93.1%), capsulorhexis was performed using the open-sky technique. The most frequent intraoperative complication was positive vitreous pressure (24.1%). In 2 eyes (6.9%), no intraocular lens implantation was performed because of posterior capsule rupture. The preoperative uncorrected visual acuity improved from 2.2 ± 0.6 logMAR (range = 3.0-0.7 logMAR) to 1.3 ± 0.7 logMAR (range = 3.0-0.18 logMAR) postoperatively ( P < 0.001). Common postoperative complications were suture loosening (44.4%) and corneal epithelial defects (33.3%). Repeat keratoplasty was necessary in 14 eyes (51.9%), including 9 eyes (64.2%) within 12 months postoperatively. The mean graft survival was 12.2 ± 17.9 months (range = 1-69 mo).

CONCLUSIONS

Triple-PKP is also feasible in emergency conditions. Nevertheless, the surgery is associated with an increased risk of intraoperative and postoperative complications. Combined surgery should, therefore, only be performed in severely diseased eyes with progressed stage of cataract.

Triplet of doubles: Double anterior chamber, double descemet membranes, and double rhexis

A 52-year-old women underwent penetrating keratoplasty for total corneal opacity after healed microbial keratitis with an uneventful postoperative period until six months when she developed gross diminution of vision. During examination, she was detected to have a membrane in the anterior chamber, creating a double anterior chamber with a total cataract. The graft was clear, and sutures were intact. Anterior segment optical coherence tomography (OCT) showed the membrane in the anterior chamber crossing the graft host junction, suggesting this membrane to be retained host descemet membrane. This was confirmed on histopathological examination. Double rhexis (descemetorhexis and capsulorhexis) was performed with cataract removal and intraocular lens (IOL) implantation, and patient had good visual recovery postoperatively.

Clinical Course of Different Types of Immune Reactions following Keratoplasty

BACKGROUND

Immune-mediated corneal graft rejection (IR) is a leading cause of corneal graft failure. The endothelium, stroma, epithelium, or a combination can be affected. Little is known about the long-term outcomes of different types of IR.

METHODS

We reviewed the medical records of all keratoplasties that had been performed at our eye centre between 2003 and 2016 (n = 3934) for any kind of IR that occurred between the surgery and 2019. All patients with a definite diagnosis of IR and sufficient clinical data were included in the analysis. IRs were grouped according to the affected part of the graft (endothelial, stromal, epithelial, and mixed). We analysed the dynamics of recovery and the clinical outcomes.

RESULTS

We identified a total of 319 patients with IR. Twenty-seven of those were lost to follow-up and were excluded from further analysis. Of the IRs, 89% affected the endothelium. Endothelial IR resulted more frequently in a considerable loss of endothelial cell density than other forms of IR. Stromal IR showed a lower relapse rate and a better visual recovery than other types of IR and resulted less often in a failure of the graft.

CONCLUSIONS

We herein report comprehensive data about the prognosis regarding functional recovery after different types of IR following keratoplasty. Our data underline that timely recognition and correct classification of IR are important because they determine the clinical course and prognosis.

Use of Post-transplant Cyclophosphamide Treatment to Build a Tolerance Platform to Prevent Liquid and Solid Organ Allograft Rejection

Corneal transplantation (CT) is the most frequent type of solid organ transplant (SOT) performed worldwide. Unfortunately, immunological rejection is the primary cause of graft failure for CT and therefore advances in immune regulation to induce tolerance remains an unmet medical need. Recently, our work and others in pre-clinical studies found that cyclophosphamide (Cy) administered after (“post-transplant,” PTCy) hematopoietic stem cell transplantation (HSCT), i.e., liquid transplants is effective for graft vs. host disease prophylaxis and enhances overall survival. Importantly, within the past 10 years, PTCy has been widely adopted for clinical HSCT and the results at many centers have been extremely encouraging. The present studies found that Cy can be effectively employed to prolong the survival of SOT, specifically mouse corneal allografts. The results demonstrated that the timing of PTCy administration is critical for these CT and distinct from the kinetics employed following allogeneic HSCT. PTCy was observed to interfere with neovascularization, a process critically associated with immune rejection of corneal tissue that ensues following the loss of ocular “immune privilege.” PTCy has the potential to delete or directly suppress allo-reactive T cells and treatment here was shown to diminish T cell rejection responses. These PTCy doses were observed to spare significant levels of CD4⁺ FoxP3⁺ (Tregs) which were found to be functional and could readily receive stimulating signals leading to their in vivo expansion via TNFRSF25 and CD25 agonists. In total, we posit future studies can take advantage of Cy based platforms to generate combinatorial strategies for long-term tolerance induction.

Boston keratoprosthesis type 1: outcomes of the first 38 cases performed at Moorfields Eye Hospital

PURPOSE

To evaluate outcomes of Boston keratoprosthesis type 1 (K-Pro) surgery in a cohort of high-risk patients at Moorfields Eye Hospital. Our patients were referred to us at the end-point of their ocular disease.

METHODS

A retrospective review of all K-Pro surgery performed between March 2011 and July 2015 with a minimum follow-up of 12 months.

RESULTS

39 eyes of 38 patients were included. Mean follow-up was 28.4 months (range: 12-56). The main indication for surgery was bullous keratopathy from multiple failed grafts (56%). 26 cases (72.2%) had known posterior segment disease pre-operatively. Mean BCVA for the entire cohort (n = 39) initially improved from HM vision to 1/60 before returning to CF vision by 6 months and was maintained for the duration of follow-up. By final follow-up (n = 39), 46% had improved vision (1 line improvement in 10%; 2 lines or more in 36%) and 31% maintained pre-operative visual acuity. Anterior segment pathology was not an independent variable in visual outcome. However, absence of posterior segment disease was significant and performed best, improving from HM to 6/15 and maintaining that vision in the longer term. There were 13 (33%) cases of progressive glaucomatous optic neuropathy, 10 (26%) retinal detachments, 8 (21%) retroprosthetic membranes, 3 (8%) infective keratitis and 2 (5%) vitritis of which 1 progressed to endophthalmitis. In all, 3 (8%) had NPL vision and 4 (10%) required removal of the K-Pro.

CONCLUSIONS

Implantation of the Boston K-Pro can lead to improved vision, with the main limiting factor being posterior segment pathology.

Biomaterials-enabled cornea regeneration in patients at high risk for rejection of donor tissue transplantation

The severe worldwide shortage of donor organs, and severe pathologies placing patients at high risk for rejecting conventional cornea transplantation, have left many corneal blind patients untreated. Following successful pre-clinical evaluation in mini-pigs, we tested a biomaterials-enabled pro-regeneration strategy to restore corneal integrity in an open-label observational study of six patients. Cell-free corneal implants comprising recombinant human collagen and phosphorylcholine were grafted by anterior lamellar keratoplasty into corneas of unilaterally blind patients diagnosed at high-risk for rejecting donor allografts. They were followed-up for a mean of 24 months. Patients with acute disease (ulceration) were relieved of pain and discomfort within 1–2 weeks post-operation. Patients with scarred or ulcerated corneas from severe infection showed better vision improvement, followed by corneas with burns. Corneas with immune or degenerative conditions transplanted for symptom relief only showed no vision improvement overall. However, grafting promoted nerve regeneration as observed by improved touch sensitivity to near normal levels in all patients tested, even for those with little/no sensitivity before treatment. Overall, three out of six patients showed significant vision improvement. Others were sufficiently stabilized to allow follow-on surgery to restore vision. Grafting outcomes in mini-pig corneas were superior to those in human subjects, emphasizing that animal models are only predictive for patients with non-severely pathological corneas; however, for establishing parameters such as stable corneal tissue and nerve regeneration, our pig model is satisfactory. While further testing is merited, we have nevertheless shown that cell-free implants are potentially safe, efficacious options for treating high-risk patients.

A biomaterial implant supports the regeneration of severely damaged corneas in patients at high risk for rejecting conventional transplantation. An international team from Canada, China, India, Sweden, Ukraine and United Kingdom used mini-pigs to confirm the safety of implanting cell-free corneas made from recombinant human collagen and a synthetic lipid, before examining the effects of implantation on human vision in seven patients. The implants were well-tolerated and led to significant vision improvement in patients with damaged corneas due to infection. Furthermore, within two weeks of surgery the implants had relieved pain. Over two years, sensitivity to touch improved, suggesting an ability to promote nerve regeneration. This study supports the use of animal models to test biomaterials designed for medical applications and describes a safe and promising option for treating patients that not treatable by conventional corneal transplantation.

Mesenchymal stem cell therapy for retro-corneal membrane - A clinical challenge in full-thickness transplantation of biosynthetic corneal equivalents

Artificial corneas (keratoprostheses) and biosynthetic collagen-based corneal equivalents are surgical implants designed to ease the global burden of corneal blindness. However, keratoprostheses in many cases fail due to development of fibrous retro-corneal membranes (RCM). Fibrous membranes which develop in the anterior chamber after prosthesis implantation do so on a matrix of fibrin. This study investigated fibrin deposition and RCM formation after full-thickness collagen-based hydrogel implants and compared them with syngeneic and allogeneic corneal grafts in mice. Fibrin cleared from the anterior chamber within 14 days in both allo- and syn-grafts but, persisted in hydrogel implants and developed into dense retro-corneal membrane (RCM) which were heavily infiltrated by activated myofibroblasts. In contrast, the number of CD11b⁺ macrophages infiltrating the initial deposition of fibrin in the anterior chamber (AC) after hydrogel implantation was markedly reduced compared to syn- and allo-grafts. Inoculation of mesenchymal stem cells prior to collagen gel implant promoted clearance of gel-associated fibrin from the anterior chamber. We propose that a failure of macrophage-mediated clearance of fibrin may be the cause of RCM formation after collagen-based hydrogel implants and that mesenchymal stem cell therapy promotes clearance of fibrin and prevents RCM formation.

STATEMENT OF SIGNIFICANCE

The manuscript addresses the potential value of bone marrow-derived mesenchymal stem cell therapy for retro-corneal membrane (RCM) formation in full-thickness transplantation of biosynthetic corneal equivalents. This work reports the pathophysiological changes in the anterior chamber of the mouse eye following full-thickness recombinant human cross-linked collagen-based hydrogel implants in which persistent fibrin promotes the development of dense RCM. Furthermore, pre-treatment with mesenchymal stem cells reduces RCM formation and enhances corneal transparency.

Trends in corneal transplant surgery in Ireland: indications and outcomes of corneal transplant surgery and intraocular lens opacification following Descemet's stripping automated endothelial keratoplasty

PURPOSE

To evaluate the indications for corneal transplantation, the procedures carried out, and the postoperative outcomes and to compare these with previous Irish corneal transplant studies.

METHODS

A retrospective review of the case notes of all patients who underwent corneal transplantation under the care of a single surgeon, from 2008 to 2015, was performed. The risk factors for postoperative complications including transplant failure were examined.

RESULTS

During the period studied, 42 corneal transplant surgeries were carried out on 40 eyes of 38 patients, 24 of whom were male (63%), median age at surgery was 62 years (range 23-96 years). The most common indication for transplantation was pseudophakic corneal decompensation associated with Fuch's endothelial dystrophy (FED) (n = 13). Seventeen penetrating keratoplasties, 23 lamellar keratoplasties, and two amniotic membrane transplant procedures were carried out. Transplant failure resulting in corneal oedema or repeat corneal transplant surgery (n = 4, 10%), was associated with previous transplant failure in the eye; odds ratio (OR) = 1.58 (p = 0.05), and with comorbid FED, OR = 1.50 (p = 0.02). Intraocular lens opacification occurred in one lens following DSAEK, giving an incidence rate of 7%.

CONCLUSIONS

Pseudophakic corneal decompensation is the commonest indication for corneal transplant surgery, with lamellar keratoplasty the most frequent approach in our cohort, reflecting developments observed in corneal transplant surgery elsewhere. Prior corneal transplant failure and Fuch's dystrophy remain important risk factors for failure. The risk of intraocular lens opacification and its potential effects on vision should be elaborated prior to endothelial keratoplasty.

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.

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.

Keratoprostheses for corneal blindness: a review of contemporary devices

According to the World Health Organization, globally 4.9 million are blind due to corneal pathology. Corneal transplantation is successful and curative of the blindness for a majority of these cases. However, it is less successful in a number of diseases that produce corneal neovascularization, dry ocular surface and recurrent inflammation, or infections. A keratoprosthesis or KPro is the only alternative to restore vision when corneal graft is a doomed failure. Although a number of KPros have been proposed, only two devices, Boston type-1 KPro and osteo-odonto-KPro, have came to the fore. The former is totally synthetic and the latter is semi-biological in constitution. These two KPros have different surgical techniques and indications. Keratoprosthetic surgery is complex and should only be undertaken in specialized centers, where expertise, multidisciplinary teams, and resources are available. In this article, we briefly discuss some of the prominent historical KPros and contemporary devices.

Efficacy and safety of systemic tacrolimus in high-risk penetrating keratoplasty after graft failure with systemic cyclosporine

PURPOSE

The aim of this study was to investigate the efficacy and safety of systemic tacrolimus for the treatment of eyes that developed graft failure despite treatment with cyclosporine (CsA).

METHODS

Ten eyes of 10 patients who underwent high-risk penetrating keratoplasty (PKP) and developed graft failure despite treatment with systemic CsA were included in this study. The patients underwent PKP and were treated with systemic tacrolimus according to the standardized protocol.

RESULTS

Treatment with tacrolimus was continued for 18.1 ± 13.9 months. The median duration of corneal graft clarity was 34.5 months. Graft rejection occurred in 2 of 10 eyes during a mean follow-up period of 48.9 ± 22.9 months. Kaplan-Meier survival plots showed significantly fewer graft rejection episodes (P = 0.033) and longer graft survival (P = 0.042) after treatment with tacrolimus compared those with CsA. Tacrolimus was discontinued in 2 patients; 1 had renal dysfunction and the other had muscle pain and fatigue. These side effects subsided after discontinuation of tacrolimus.

CONCLUSIONS

Treatment with systemic tacrolimus is possibly safe and effective in reducing graft rejection and prolonging graft survival in patients with high-risk PKP after graft failure with systemic CsA.

The use of an IL-1 receptor antagonist peptide to control inflammation in the treatment of corneal limbal epithelial stem cell deficiency

Corneal limbal stem cell deficiency (LSCD) may be treated using ex vivo limbal epithelial stem cells (LESCs) derived from cadaveric donor tissue. However, continuing challenges exist around tissue availability, inflammation, and transplant rejection. Lipopolysaccharide (LPS) or recombinant human IL-1β stimulated primary human keratocyte and LESC models were used to investigate the anti-inflammatory properties of a short chain, IL-1 receptor antagonist peptide for use in LESC sheet growth to control inflammation. The peptide was characterized using mass spectroscopy and high performance liquid chromatography. Peptide cytotoxicity, patterns of cell cytokine expression in response to LPS or IL-1β stimulation, and peptide suppression of this response were investigated by MTS/LDH assays, ELISA, and q-PCR. Cell differences in LPS stimulated toll-like receptor 4 expression were investigated using immunocytochemistry. A significant reduction in rIL-1β stimulated inflammatory cytokine production occurred following LESC and keratocyte incubation with anti-inflammatory peptide and in LPS stimulated IL-6 and IL-8 production following keratocyte incubation with peptide (1 mg/mL) (P < 0.05). LESCs produced no cytokine response to LPS stimulation and showed no TLR4 expression. The peptide supported LESC growth when adhered to a silicone hydrogel contact lens indicating potential use in improved LESC grafting through suppression of inflammation.

A brief review of Boston type-1 and osteo-odonto keratoprostheses

Globally there are ≈4.9 million bilaterally corneal blind and 23 million unilaterally corneal blind. Majority of this blindness exists in the developing countries, where resources for corneal banking and transplant surgery are less than adequate. Survival of corneal grafts gradually declines over the long term. Corneal transplantation has poor prognosis in vascularised corneal beds, ocular surface disease and viral keratitis. Keratoprosthesis (KPro) remains as a final option for end-stage ocular surface disease, multiple corneal transplant failures and high-risk corneal grafts. Boston type-1 KPro and osteo-odonto-keratoprosthesis are the two devices proven useful in recent years. Choice of a keratoprosthetic device is patient specific based on the underlying diagnosis, ocular morbidity and patient suitability. KPro surgery demands a high level of clinical and surgical expertise, lifelong commitment and extensive resources. Improvements in techniques and biomaterials may in the future provide retainable KPros that do not need regular follow-up of patients, have low complications but high retention rates and may be produced at a low cost on a mass scale to be available as 'off the shelf' devices. Because KPros have the potential to effectively address the burden of surgically treatable corneal blindness and may also eliminate the problems of corneal transplantation, more research is required to develop KPros as substitutes for corneal transplantation even in low-risk cases. In those countries where corneal blindness is a major liability, we need a two pronged approach: one to develop eye donation, eye banking and corneal transplantation and the second to establish centres for keratoprostheses, which are affordable and technically not challenging, in a population where default on follow-up visits are high. Until the latter is achieved, KPros should be viewed as a temporary means for visual restoration and be offered in national and supraregional specialised centres only.

Allograft survival enhancement using doxycycline in alkali-burned mouse corneas

PURPOSE

To explore the inhibitory effects of doxycycline on allograft rejection in alkali-burned cornea beds.

METHODS

The corneas of BALB/c mice were injured using a 1 mol/l NaOH solution. Following the injury, the corneas from C57BL/6 mice were transplanted into the eyes of BALB/c mice after being randomized into three groups: allogeneic corneal transplantation (group A), topical use of doxycycline after allogeneic corneal transplantation (group B) and syngeneic corneal transplantation (group C). Corneal angiogenesis was examined using whole-mount immunofluorescence, and corneal inflammation was evaluated using inflammation index scoring. The immune rejection of the grafts was examined using a slit lamp. In addition, the expression of vascular endothelial growth factor A and interleukin-1β in the transplanted corneas was examined using a real-time polymerase chain reaction, immunohistochemistry and an enzyme-linked immunosorbent assay.

RESULTS

The outgrowth of the corneal blood vessels in the group A mice was faster than that in the group B and group C mice. The inflammation index levels were highest in the group A mice, intermediate in the group B mice and lowest in the group C mice. Vascular endothelial growth factor and the interleukin-1β protein and mRNA levels decreased dramatically in the group B mice compared with the group A mice (all p-values < 0.01). In addition, the mean survival time in the group B mice (27.00 ± 2.00 days) was significantly longer than that in the group A mice (11.67 ± 1.51 days; p < 0.05).

CONCLUSIONS

Doxycycline may have had a significant role in preventing corneal angiogenesis and inflammation in alkali-burned corneal beds, which resulted in higher allograft survival rates.

The high-risk corneal regraft model: a justification for tissue matching in humans

Models of high-risk corneal graft rejection involve neovascularization induced via innate immune responses, e.g., suture-mediated trauma. We describe a model of high-risk corneal graft rejection using corneal graft donor-recipient pairing based on a single-antigen disparity. Donor corneas from transgenic mice on B10.BR (H-2k ) background, in which hen-egg lysozyme (HEL) as a membrane-bound antigen (mHEL) was expressed under the major histocompatibility complex (MHC) class I promoter (KLK-mHEL, H-2k), were transplanted into wild type B10.BR recipient mice. Unmanipulated wild type recipient mice rejected KLK-mHEL grafts (39%) slowly over 50-60 days. Graft rejection incidence was maximized (100%) and tempo accelerated (27 days) by priming with HEL-pulsed syngeneic dendritic cells and less so by increasing T-cell precursor frequency. Rejection also reached maximum levels (100%) and tempo (3-8 days) when mice which had rejected a first graft ('rejectors') were regrafted, and was associated with induction of HEL-specific memory T cells. In contrast, 'acceptors' rejected a second graft at rates and tempo similar to naïve mice. These data reveal the importance of (i) donor MHC antigens as alloantigens for indirect recognition, (ii) alloantigen-specific memory in high-risk graft rejection involving regrafts, and (iii) suggest a role for tissue matching in human corneal graft to avoid sensitization to donor MHC antigens.

Irreversible optical clearing of rabbit dermis for autogenic corneal stroma transplantation

Tissue engineering and transplantation of autogenic grafts have been widely investigated for solving problems on current allograft treatments (i.g., donor shortage and rejection). However, it is difficult to obtain an autogenic corneal stromal replacement that is composed of transparent, tough, and thick collagen constructs by current cell culture-based tissue engineering. Aim of this study is to develop transparent dermis for an autogenic corneal stroma transplantation. This study examined dehydration at 4-8°C and carbodiimide cross-linking on cloudy rabbit dermis (approx. 1.8%-3.8% light transmittance at 550 nm) for dermis optical clearing. Transparency of dehydrated rabbit dermis was founded to be approx. 37.9%-41.4% at 550 nm. Additional cross-linking treatment on dehydrated dermis prevented from swelling and clouding in saline, and improved its transparency to be 56.9% at 550 nm. Rabbit corneal epithelium was found to regenerate on optically cleared dermis in vitro. Furthermore, no abnormal biological response (i.e., inflammation, vascularization, and the barrier defect of epithelia) or no optical functional change on optically cleared dermis was observed during its 4-week autogenic transplantation into rabbit corneal stromal pocket.

Potent in vivo antiangiogenic effects of GS-101 (5'-TATCCGGAGGGCTCGCCATGCTGCT-3'), an antisense oligonucleotide preventing the expression of insulin receptor substrate-1

Angiogenesis is a complex phenomenon regulated by both pro- and antiangiogenic factors such as the vascular endothelial growth factor (VEGF), and inflammation may be involved in the process. Although antagonizing VEGF has been proposed as a therapeutic approach to limit corneal angiogenesis, alternative targets are needed. In this study, we demonstrate that, under proangiogenic experimental conditions, human endothelial cells (hECs) express more insulin receptor substrate (IRS)-1 proteins relative to quiescent cells. The antisense oligonucleotide, GS-101 (5'-TATCCGGAGGGCTCGCCATGCTGCT-3'), targeting IRS-1 mRNA, dose-dependently inhibited (p < 0.01) both IRS-1 expression and in vitro angiogenesis (hEC tube-like structure formation) with IC(50) of 8.51 +/- 3.01 microM (mean +/- S.E.M.) and 2.47 +/- 0.56 microM, respectively, demonstrating that partial IRS-1 down-regulation interferes with angiogenesis. The antiangiogenic effects of GS-101 were associated with a decrease in protein kinase B (Akt) activation but not mitogen-activated protein kinase-1/2 and a dose-dependent reduction in vascular endothelial growth factor-A (IC(50) = 5.59 +/- 2.76 microM) and the proinflammatory cytokine interleukin-1beta (IC(50) = 2.19 +/- 1.07 microM) mRNA expression. In accordance, once daily topical application of GS-101 dose-dependently inhibited injury-dependent corneal angiogenesis in vivo (p < 0.05). GS-101 in vivo efficacy was achieved at final tissue concentrations within in vitro EC(50) for IRS-1 down-regulation. In conclusion, these results suggest that IRS-1 is important for angiogenesis and that GS-101 could become a novel therapeutic tool against corneal angiogenesis.

Cost of corneal transplantation for the Quebec health care system

OBJECTIVE

Although corneal graft is a common, long-standing procedure, little is known about its economic impact. The purpose of this study was to estimate resource use and costs associated with corneal transplantation according to a public third-party perspective.

DESIGN

Retrospective study using claim data from the Régie de l'assurance maladie du Québec (RAMQ).

PARTICIPANTS

A total of 610 subjects were included in the study. Mean age was 54.8 (SD 20.4) years.

METHODS

The RAMQ provided medical and pharmaceutical data for a random sample of 75% of the patients who underwent a corneal graft procedure between June 1, 1999, and May 31, 2002. Resource usage data, defined as medical interventions, physician visits, and medication, were collected for a 3-year postoperative follow-up period. Hospital costs associated with corneal graft were obtained from the University of Montreal Hospital Centre costing system.

RESULTS

The average costs per patient for graft and anesthesia were $501 (SD $75) and $115 (SD $124), respectively. The mean cost per patient for physician visits was $276 (SD $146). The mean number of physician visits per patient during the follow-up was 14.9 (SD 9.1). The cost per patient for medication was $337 (SD $1075). The average total cost per patient was $1229 (SD $1125). Costs incurred by the hospital represented a total of $1942.

CONCLUSIONS

The overall cost of corneal graft, including a 3-year follow-up, was estimated at $3171 ($1229 RAMQ, $1942 hospital). The majority of these costs occurred at the time of the procedure.

Effect of CXCL-1/KC production in high risk vascularized corneal allografts on T cell recruitment and graft rejection

BACKGROUND

The survival rate of corneal allografts in high-risk vascularized corneal bed recipients is poor, similar to vascularized solid organ allografts. Although the early induction of selective chemokines in solid organs is required for the optimal recruitment of T cells into rejecting allografts, little is known about the role of these chemokines in high risk corneal allografts.

METHODS

Orthotopic corneal allotransplants were performed in low-risk (nonvascularized) and high-risk (vascularized) C57BL/6 (H-2b) recipients using Balb/c (H-2d) donors. Intragraft production of CXC chemokines was measured by Luminex and enzyme-linked immunosorbent assay on corneal transplant extracts at different times after surgery. Rabbit anti-KC serum was used to test its role in high risk corneal allograft survival.

RESULTS

Early upregulation of CXCL1/KC occurs 3 days after transplantation in high risk allograft only. Moreover, the T-cell chemoattractants, CXCL9/Mig and CXCL10/IP10, are produced late (day 10) after surgery and their production correlates with the recruitment of CD4 T cells into the graft. Furthermore, in vivo neutralization of CXCL1/KC with anti-KC sera results in increased graft survival and decreased recruitment of T cells into high-risk allografts.

CONCLUSION

We propose that a high risk vascularized cornea behaves like a vascularized solid organ transplant. The early production of CXCL1/KC is crucial to the induction of T-cell chemoattractants necessary for the recruitment of allospecific CD4 T cells into the graft. In vivo neutralization of CXCL1/KC represents a potential novel therapy that could be used to increase the survival rate of high-risk vascularized corneal allografts.

How effective is penetrating corneal transplantation? Factors influencing long-term outcome in multivariate analysis

BACKGROUND

In a large patient cohort, we investigated long-term corneal graft outcome, risk factors for graft failure, and whether corneal graft survival had improved over time.

METHODS

Records of 10,952 full-thickness corneal grafts with associated archival follow-up were examined within a prospectively-maintained, national database of 13,831 records, with follow-up extending for up to 18 years. Kaplan-Meier survival analysis was used to indicate variables of interest for Cox proportional hazards regression analysis. A model clustered by individual patient to control for inter-eye or inter-graft dependence was constructed to identify variables best predicting penetrating corneal graft failure.

RESULTS

Probability of corneal graft survival was 0.86 at 1 year, 0.73 at 5 years, 0.62 at 10 years, and 0.55 at 15 years. Graft survival did not improve over a 15-year timeframe. Variables predicting graft failure in multivariate analysis included transplant centre, donor age, preoperative diagnosis, number of previous ipsilateral grafts, lens status, history of corneal neovascularisation, ocular inflammation or raised intraocular pressure in the grafted eye, requirement for anterior vitrectomy, graft size, early suture removal, postoperative events including graft neovascularisation, rise in intraocular pressure, and rejection episodes, type of treatment for raised intraocular pressure, and arrangements for recipient follow-up. A further 11 variables showing a significant influence on graft survival in univariate analysis were not included in the final Cox model.

CONCLUSION

The long-term results of corneal transplantation are no better than for other forms of transplantation and have shown no measurable improvement over the past 15 years.

Centennial review of corneal transplantation

Abstract One hundred years ago, on 7 December 1905, Dr Eduard Zirm performed the world's first successful human corneal transplant. This significant milestone was achieved only after many decades of unsuccessful trial and error; however, it did not lead to relatively 'routine' keratoplasty success for several more decades. The idea of replacing an opaque cornea had been suggested for centuries, and had stimulated theoretical approaches to the problem by many esteemed physicians throughout history. However, little practical progress was made in the ultimate realization of the dream until the 19th century when pioneering surgeons pursued extensive studies in relation to both animal and human 'keratoplasty'. Clinical progress and scientific insight developed slowly, and it was ultimately due to parallel advances in medicine such as anaesthesia and antisepsis that Zirm's success was finally achieved. Key concepts were enshrined such as the use of fresh tissue from the same species, careful placement and handling of tissue, and the development of specialized instrumentation such as the circular trephine. In the latter half of the 20th century, many 'masters' of corneal surgery evolved significant refinements in technique and instrumentation with the development of corticosteroids, antibiotics, surgical microscopes, improved trephines, viscoelastics and suture materials, that enable this delicate procedure to be routinely performed with the prospect of success. There are still limitations to corneal transplantation, and corneal allograft rejection still poses the greatest challenge to the modern corneal surgeon. In the foreseeable future it may be in the laboratory, rather than the theatre, that further milestones will be achieved. This review aims to highlight the significant milestones in the rich history of corneal transplantation, and to pay tribute to the many inspired and dedicated individuals involved in the development of keratoplasty to a point where the procedure is now a standard tool in the repertoire of ophthalmic surgery and more than a million people have enjoyed restoration of useful sight.

Corneal graft rejection occurs despite Fas ligand expression and apoptosis of infiltrating cells

BACKGROUND/AIMS

Constitutive expression of Fas ligand (CD95L) protects the eye against cell mediated immune responses by inducing apoptosis in infiltrating Fas bearing T cells. This study was designed to examine Fas ligand expression on acutely rejecting rat corneal grafts and to investigate the kinetics of induction of apoptosis in infiltrating leucocytes.

METHODS

Orthotopic penetrating corneal transplantation was performed between genetically disparate inbred rats. Fas ligand expression and the phenotype of infiltrating leucocytes were examined by immunohistochemistry. Apoptotic nuclei were visualised in sections of normal rat cornea, rejecting allografts, and time matched isografts by terminal deoxynucleotidyl transferase mediated dUTP biotin nick end labelling (TUNEL) and quantified by video image analysis. Staining with Hoechst dye 33258 was used to confirm the presence of apoptotic nuclei.

RESULTS

Fas ligand was expressed on corneal endothelial and epithelial cells during acute corneal graft rejection. At all time points examined, including as early as the fifth postoperative day, the cells infiltrating both corneal isografts and allografts were TUNEL positive. By the 15th postoperative day, over 90% of all nuclei, many of which were T cells, were apoptotic.

CONCLUSION

Expression of Fas ligand is not downregulated on the cornea during allograft rejection and infiltrating leucocytes in both isografts and allografts die rapidly in situ. Despite the death of the cells believed to be responsible for rejection, isografts survive indefinitely whereas allografts are irreparably damaged.