Immunological Graft Rejection Research Articles

Prospective Assessment of Loteprednol Etabonate 0.25% for Prevention of Immunologic Rejection After Descemet Membrane Endothelial Keratoplasty in Eyes With Fuchs Dystrophy.

The purpose of this study was to assess off-label use of loteprednol etabonate 0.25% ophthalmic suspension for prevention of immunologic rejection after Descemet membrane endothelial keratoplasty (DMEK). This prospective, open-label study enrolled 70 eyes of 70 participants without preexisting glaucoma 1 month after DMEK. Participants used topical loteprednol 0.25% 4 times daily for 2 months, tapered by 1 drop/month to once daily use, and continued use through 1 year after DMEK. Main outcomes were rate of intraocular pressure (IOP) elevation (defined as a relative increase of ≥10 mm Hg over the pretransplant IOP) and rate of initial allograft rejection episodes. The results were compared with historical data using the log-rank test. All participants had Fuchs dystrophy, and 40 of 70 (57%) were female. None (0%) experienced an immunologic graft rejection episode, matching the previously reported efficacy of prednisolone acetate 1% suspension and loteprednol 0.5% gel (both 0% incidence). One study eye developed IOP elevation 3 months after DMEK (cumulative risk 1.5%). Compared with historical data, this was similar to the risk with loteprednol 0.5% gel (4%, P = 0.36) and significantly lower than the risk with prednisolone 1% suspension (18%, P = 0.0025). Two participants (3%) complained of instillation site discomfort, consistent with the 5% rate reported on package labeling. Loteprednol 0.25% suspension, approved for short-term treatment of dry eyes, effectively prevented immunologic rejection episodes with minimal risk of IOP elevation when used from 1 month until 12 months after DMEK in patients without preexisting glaucoma.

Impact of pandemic COVID-19 lockdown on penetrating keratoplasty patients.

To study the impact of the COVID-19 lockdown on the regular follow-up of keratoplasty patients. This retrospective interventional case series included 30 patients who had immunological corneal endothelial rejection out of 190 patients who came for post-PKP follow-up between September 15, 2019, and September 30, 2020. The demographics, primary diagnosis, surgical technique, time of presentation, recovery of graft, associated ocular problems, and visual acuity at 1 month were analyzed. Forward stepwise (likelihood ratio) binary logistic regression was used to find significant variables. The study population had 19 males (63.33%) and 11 females (36.67%). The mean age of the study group was 42.83 ± 18.89 (8-80) years. Of 30 patients, 19 (63.3%) presented before and 11 (36.7%) after the COVID-19 lockdown. Overall, 23 (77%) showed a reversal of graft rejection. Logistic regression showed that preoperative indications, large-sized grafts, and deep corneal vascularization were significant risk factors for non-resolution of graft rejection. It was noted that patients who presented to the hospital late had poor recovery (P = 0.002). The delay in the presentation was a significant risk factor for non-resolution of graft rejection (P < 0.01). Z-test for proportions revealed that the difference in the non-resolution of rejection on immediate or delayed treatment in patients presenting during lockdown (P = 0.002) was significant. This article is to highlight the impact of the COVID-19 lockdown on graft rejection recovery of PKP patients due to delays in follow-up. Early treatment helps in the recovery of graft transparency and the reversal of immunological graft rejection. Also, primary diagnosis, deep vascularization, and large-sized grafts were significant risk factors for non-resolution of graft rejection.

Direct Differentiation of Human Embryonic Stem Cells to 3D Functional Hepatocyte-like Cells in Alginate Microencapsulation Sphere.

Background: The lack of a stable source of hepatocytes is one of major limitations in hepatocyte transplantation and clinical applications of a bioartificial liver. Human embryonic stem cells (hESCs) with a high degree of self-renewal and totipotency are a potentially limitless source of a variety of cell lineages, including hepatocytes. Many techniques have been developed for effective differentiation of hESCs into functional hepatocyte-like cells. However, the application of hESC-derived hepatocyte-like cells (hESC-Heps) in the clinic has been constrained by the low yield of fully differentiated cells, small-scale culture, difficulties in harvesting, and immunologic graft rejection. To resolve these shortcomings, we developed a novel 3D differentiation system involving alginate-microencapsulated spheres to improve current hepatic differentiation, providing ready-to-use hESC-Heps. Methods: In this study, we used alginate microencapsulation technology to differentiate human embryonic stem cells into hepatocyte-like cells (hESC-Heps). Hepatic markers of hESC-Heps were examined by qPCR and Western blotting, and hepatic functions of hESC-Heps were evaluated by indocyanine-green uptake and release, and ammonia removal. Results: The maturity and hepatic functions of the hESC-Heps derived from this 3D system were better than those derived from 2D culture. Hepatocyte-enriched genes, such as HNF4α, AFP, and ALB, were expressed at higher levels in 3D hESC-Heps than in 2D hESC-Heps. 3D hESC-Heps could metabolize indocyanine green and had better capacity to scavenge ammonia. In addition, the 3D sodium alginate hydrogel microspheres could block viral entry into the microspheres, and thus protect hESC-Heps in 3D microspheres from viral infection. Conclusion: We developed a novel 3D differentiation system for differentiating hESCs into hepatocyte-like cells by using alginate microcapsules.

Ex Vivo T-Cell Receptor αβ +/CD19 +depletion of Peripheral Stem Cell Grafts for Pediatric Patients with Bone Marrow Failure (BMF) Undergoing Unrelated Donor Transplantation

Background: Success of alternative donor stem cell transplantation (SCT) for acquired and inherited bone marrow failure (BMF) syndromes has previously been limited by significant risks of severe graft versus host disease (GvHD) and graft failure, particularly for patients who lack fully HLA-matched donors. The development of post-transplant cyclophosphamide (ptCy)-based haploidentical donor SCT has mitigated but not eliminated these risks, and the relatively slow engraftment seen with ptCy bone marrow grafts may not be ideal given high rates of infectious disease and bleeding concerns in patients with BMF. Partial T cell depletion of mobilized peripheral stem cell (PSC) grafts can greatly reduce risks of graft versus host disease while facilitating rapid and robust engraftment by providing a high stem cell dose. We previously reported excellent outcomes with minimal GVHD and no graft rejection using peripheral stem cell transplant (PSCT) combined with ex vivo CD3 +/CD19 +depletion and low dose CD3+ T cell addback from matched unrelated donors (MUD) and mismatched unrelated donors (MMUD) in pediatric patients with BMF. Here, we describe the use of selective ex vivoT cell receptor (TCR)αβ +/CD19 +depletion of mobilized PSC from MUD and MMUD for pediatric patients with BMF, which has the advantage of retaining TCRgd +T cells which may help facilitate engraftment and decrease infections.Methods: We report the outcomes of 26 pediatric patients with BMF (excluding MDS-defining clonal evolution) who underwent MUD/MMUD PSCT with TCRαβ +T cell/CD19 +depletion using CliniMACS at The Children's Hospital of Philadelphia from 2017 to 2021. Patients were enrolled on a prospective clinical trial for patients with BMF (NCT03047746, n=21)or on an expanded access study (NCT03145545, n=5). Conditioning regimens consisted of thymoglobulin (9mg/kg), cyclophosphamide (100mg/kg), fludarabine (150mg/m 2), and low dose TBI (200-300 cGy) for patients with acquired BMF disorders, thymoglobulin (9mg/kg), busulfan (PK-adjusted), fludarabine (150mg/m 2), and thiotepa (10mg/kg) for patients with single lineage BMF or thymoglobulin. One patient with Fanconi Anemia received thymoglobulin and fludarabine, with reduced dosing of busulfan and cyclophosphamide. Patients undergoing MSD-BMT for BMF over a similar time period served as a comparison group for engraftment kinetics, rates of GVHD, donor chimerism, immune reconstitution, and overall survival.Results: Subjects included 18 with severe acquired aplastic anemia (SAAA), 4 with SAAA and concurrent paroxysmal nocturnal hemoglobinuria (PNH), 2 patients with acquired BMF not otherwise specified, 1 patient with DBA, and 1 patient with Fanconi Anemia. 11 patients with SAAA underwent SCT as initial therapy while 11 patients had SCT after failing previous medical therapies. Median age at diagnosis was 10.3 years (0.1-20.6) and at transplant 11.1 years (0.9-21). HLA match of unrelated donors was either 10/10 (n=15), or 9/10 (n=11). Median CD34 +and TCR αβ +T cell dose was 12.0x10 6cells/kg (3-22.6) and 0.1x10 5cells/kg (0.0-4.2). Median times to neutrophil and platelet engraftment per CIBMTR criteria were 15 days (10-22) and 15 days (13-19), respectively, both significantly earlier than engraftment following MSD-BMT (Fig 1a). At a median follow-up of 727 days (39-1498), 25 of 26 patients are alive with resolved hematologic disease (Fig 1b). One patient with SAAA+PNH who failed prior IST achieved trilinear engraftment without GVHD, but died on Day+95 due to acute disseminated toxoplasmosis. No patients exhibited immunologic graft rejection. 2/26 patients had grade II acute GVHD that responded to steroids and none developed Grade III-IV acute or chronic extensive GVHD (Fig 1c) CMV viremia/reactivation occurred in 5 subjects, all responding to antiviral pharmacotherapy, and none developed end-organ CMV disease (Fig 1d). One patient developed recipient-derived EBV post-transplant lymphoproliferative disorder requiring multimodal treatment. Only one patient developed BK cystitis. Total peripheral chimerism exceeded 90% in all patients. Immune reconstitution kinetics were similar to that seen in MSD-BMT.Conclusion: MUD/MMUD PSCT with TCRαβ +T cell/CD19 +depletion in patients with BMF enables rapid, durable engraftment with minimal risk of GVHD and immunologic graft rejection. [Display omitted] DisclosuresMonos: Omixon: Consultancy, Patents & Royalties. Grupp: Jazz Pharmaceuticals: Consultancy, Other: Steering committee, Research Funding; Novartis, Adaptimmune, TCR2, Cellectis, Juno, Vertex, Allogene and Cabaletta: Other: Study steering committees or scientific advisory boards; Novartis, Kite, Vertex, and Servier: Research Funding; Novartis, Roche, GSK, Humanigen, CBMG, Eureka, and Janssen/JnJ: Consultancy.

Treatment With Melatonin After Corneal Graft Attenuates Rejection.

Background: Immunologic graft rejection is the main complication of corneal transplants. This study aimed to investigate the effect of melatonin (MT) on the rejection of corneal transplantation. Methods: Corneal allografts were performed by grafting corneas from BALB/C mice to C57BL/6 hosts. MT (50 mg/kg) was intraperitoneally injected into the hosts every day from the day of transplantation. The survival of grafts was observed by slit lamp biomicroscopy, and inflammatory cell infiltration was detected by hematoxylin and eosin staining and immunohistochemistry. The balance of Teff and Treg immune cells in draining lymph nodes (DLNs) was detected by flow cytometry. The levels of cytokines related to the grafts and DLNs were detected using real-time fluorescence quantitative PCR. Additionally, we used the mouse macrophage line RAW264.7 to study the effect of MT on the activation of NLRP3 inflammatory body. Results: MT treatment improved the graft survival rate, reduced inflammatory cell infiltration in the graft, decreased the percentage of Th1/Th17 cells in the DLNs, and increased the percentage of Treg cells. Melatonin inhibited the activation of the NLRP3 inflammasome, thereby reducing the expression of IL-1β and other related proinflammatory cytokines such as MCP-1, MIP-1, NLRP3, ASC, TNF-a and VEGF-A (all p < 0.05). Conclusion: Our study demonstrates that MT promotes the survival of mouse corneal grafts by inhibiting NLRP3-mediated immune regulation, reducing immune cell activation and cell migration, and inhibiting the production of inflammatory-related cytokines. Treatment with MT might provide a potential clinical therapeutic target for corneal transplantation.

Donor Cornea Use in Scleral Surface Reconstruction

Objectives:To investigate the indications for and results of treating scleral surface problems with donor corneal grafts that are not used in keratoplasty surgery or are left over from keratoplasty.Materials and Methods:The records of 16 patients in whom corneal tissue was used to repair a scleral tissue defect or cover an exposed glaucoma drainage implant were evaluated retrospectively. Partial-thickness grafts were prepared using a combined microkeratome system with artificial anterior chamber in 10 eyes and by manual dissection in 3 eyes. Full-thickness grafts were used in 3 eyes.Results:There were 8 female and 8 male patients aged 5-79 years (mean: 39.37±24.68). Indications for the use of corneal tissue on the scleral surface were limbal dermoid excision (n=2), pterygium surgery (n=1), intraocular lens removal and scleral fixation intraocular lens (SFIOL) implantation (n=1), exposed SFIOL suture coverage (n=1), trauma (n=2), scleral tissue loss due to repeated glaucoma surgeries (n=5), and exposed glaucoma drainage implant (n=4). The patients were followed for 6-42 months (mean: 14.37±9.14). None of the patients had graft infection, thinning, immunological graft rejection, or vision loss during follow-up. Tectonic lamellar grafts did not adversely affect final visual acuity in any case. At final examination, a good combination of graft and recipient tissue, a smooth ocular surface, and a cosmetic appearance were achieved in all eyes.Conclusion:Donor corneas that are not suitable for corneal transplantation or left over from the cornea transplant can be used in patients with scleral tissue loss due to various pathologies and in the treatment of glaucoma drainage implant erosion. In these cases, the use of corneal grafts provides a good ocular surface restoration and cosmetic appearance. The effectiveness and safety of this method should be investigated with large patient series and long follow-up times.

Topical corticosteroids with topical cyclosporine A versus topical corticosteroids alone for immunological corneal graft rejection.

To assess the efficacy and safety of supplementing topical cyclosporine A (CsA) to topical corticosteroids (CS), in the prophylaxis and treatment of corneal graft rejection following penetrating keratoplasty (PK). Meta-analysis. Search was performed in PubMed, CENTRAL, ClinicalTrials.gov, reference lists of articles and conference proceedings. Primary outcomes: 1-year rejection-free survival rate (prophylaxis); resolution rate of rejection episodes (treatment). Secondary outcomes: 6- and 24-month rejection-free graft survival rate, number of rejection episodes during follow-up, time-to-resolution of rejection episode, 12- and 24-months graft survival rate, adverse events. Subgroup analyses were planned for high-risk grafts; primary vs. secondary prophylaxis of graft rejection episodes; and CsA concentrations of 0.05%, 1%, and 2%. Five studies of moderate methodological quality were included (one retrospective, four RCT), assessing 459 eyes (CS + CsA 226, CS 233). In the prophylaxis setting, supplemental CsA was associated with a higher rejection-free survival rate at 12-months (RR 1.25, 95% CI: 1.00-1.56, p = 0.05) and 24-months post-PK (RR 1.56, 95% CI: 1.15-2.11, p < 0.01), though no differences were found at the 6-months timepoint (p = 0.93). This effect was mostly verified using CsA 2% in the high-risk subset of patients. In the treatment setting, no differences were found in the resolution rate of rejection episodes (p = 0.23). No differences existed on drug-related adverse events. In the prophylaxis of rejection episodes post-PK, the combined regimen of CS + CsA was associated with a higher 1- and 2-year rejection-free graft survival rate. Subgroup analysis mostly supported the use of CsA 2% for high-risk grafts. Further studies are needed to validate these results.

Partial Heterotopic Hindlimb Transplantation Model in Rats.

Vascularized composite allotransplantations (VCA) represent the most advanced reconstruction option for patients without autologous surgical possibilities after a complex tissue defect. Face and hand transplantations have changed disfigured patients' lives, giving them a new aesthetic and functional social organ. Despite promising outcomes, VCA is still underperformed due to life-long immunosuppression comorbidities and infectious complications. The rat is an ideal animal model for in vivo studies investigating immunological pathways and graft rejection mechanisms. Rats are also widely used in novel composite tissue graft preservation techniques, including perfusion and cryopreservation studies. Models used for VCA in rats must be reproducible, reliable, and efficient with low postoperative morbidity and mortality. Heterotopic limb transplantation procedures fulfill these criteria and are easier to perform than orthotopic limb transplants. Mastering rodent microsurgical models requires solid experience in microsurgery and animal care. Herein is reported a reliable and reproducible model of partial heterotopic osteomyocutaneous flap transplantation in rats, the postoperative outcomes, and the means of prevention of potential complications.

Comparative Study of Long-term Graft Survival Between Penetrating Keratoplasty and Deep Anterior Lamellar Keratoplasty

Endothelial failure and immunological graft rejection remain long-term complications leading to late graft failure in penetrating keratoplasty (PK). Deep anterior lamellar keratoplasty (DALK) has emerged as a viable alternative that enables preservation of the host's endothelial cells to eliminate risks of endothelial rejection and failure. The aim of this study was to compare long-term graft survival between PK and DALK. Retrospective clinical cohort study. All consecutive primary grafts of DALKs (n= 362) and PKs (n= 307) performed for optical indications in a tertiary eye center from the ongoing, prospective Singapore Corneal Transplant Study. Ten-year graft survival outcomes were compared. Cases in which endothelial pathologies were diagnosed were excluded, as DALK was not performed for such cases. Main outcome measurements were mean graft survival rate. The survival rate for PK was 94.4%, 80.4%, and 72.0% at 1, 5, and 10 years, respectively; and 95.8%, 93.9%, and 93.9% at 1, 5, and 10 years, respectively, for DALK (P= .001). Patients who underwent PK developed more complications of glaucoma (29.3% vs. 11.6%, respectively; P < .001), allograft rejection (16.6% vs. 1.7%, respectively; P < .001), epithelial problems (10.4% vs. 5.5%, respectively; P= .018), and nonimmunological failure (7.8% vs. 1.9%, respectively; P < .001), compared to DALK. Rates of graft failure attributable to rejection (36.7% vs. 5.9%, respectively; P= .015) and endothelial failure (36.7% vs. 5.9%, respectively; P= .015) were lower in DALK. The 10-year graft survival for primary DALK was superior to that for PK for corneal pathologies with functional endothelium. Primary DALK resulted in fewer post-operative complications and lower rates of graft rejection and failure. This study strengthens the case in favor of performing DALK over PK when possible.

Appearance, recurrence and prognosis of immunological graft rejection after penetrating keratoplasty

The aim of this study was to examine the patterns of immunological graft rejection reactions (IAR) after penetrating keratoplasty (KPL) and to assess the prognosis for preservation of transparency of the corneal graft. In the period from 2006 to 2015 a total of 190 IAR, which occurred in 120 eyes of 119 patients, were retrospectively analyzed. The underlying disease, number of previous KPL and IAR and measures of best corrected visual acuity (BCVA, logMAR) and pachymetry at the time points T1 = postoperatively, T2 = acute IAR, T3 = follow-up at 6 weeks and T4 = follow-up at 3-12months were recorded. Asuccessful treatment was defined as alack of early recurrence (6-12weeks after treatment) or the necessity for repeating the KPL. Data were compared using the χ2-test and Wilcoxon-Mann-Whitney U‑test with asignificance level of 5%. The Kaplan-Meier procedure was used to define the rejection-free interval after KPL. The temporal analysis showed amedian rejection-free interval of 19.3months after the previous KPL (95% confidence interval, CI 14.7-26.6 months). In 138 out of 190 cases (72.6%) the IAR could be successfully treated, 12(6.3%) suffered an early recurrence and 40(21%) were irreversible. Despite asignificant decrease of BCVA at T2 from 0.5 ± 0.4 at T1 to 0.7 ± 0.5 at T2 (p < 0.001), the comparison with the follow-up at 3-12months (T1 vs. T4) showed no significant differences. The pachymetry at the thinnest point showed significant changes from T1 (535.4 ± 64.1 µm) to T2 (636.1 ± 102.1 µm; p < 0.001). Despite asignificant reduction in thickness at T3 (607.3 ± 114.0 µm, p = 0.03), the corneal grafts were still significantly thicker in the follow-up at 3-12months (591.8 ± 116.8 µm; p < 0.001; T1 vs. T4). With closely monitored aftercare following surgery IAR after KPL is rare. In most cases IAR typically occurs in the second postoperative year after KPL and under adequate treatment is reversible in approximately 75% of the cases. While BCVA showed agood recovery until the end of the follow-up period, the corneal grafts were still significantly thicker in the long-term after IAR (7.7-9.7%).

Descemet membrane endothelial keratoplasty after penetrating keratoplasty

# Purpose To describe visual and clinical outcomes of descemet membrane endothelial keratoplasty (DMEK) for late endothelial failure after penetrating keratoplasty (PK). # Methods Retrospective, observational study of patients who consecutively received DMEK to treat PK graft failure. Intraoperative complications were recorded. Our previously described DMEK surgical technique was used except that host descemet membrane was not stripped in any of the eyes. Corrected distance visual acuity (CDVA), and endothelial cell density (ECD) were evaluated before surgery and at regular intervals up to 24 months after the surgery. # Results Twenty-six eyes of 26 patients were included. Mean host age was 58.50 ± 12.50 years old. Mean donor age was 65.30 ± 10.49. Mean follow up after DMEK was 23.08 ± 10.27 (range 6 months–48 months). Seventeen (65.38%) eyes reached at least the 24-month follow up time point. At last follow up, 24 eyes (92.31%) presented with clear corneas. Twenty-four months postoperatively, mean Snellen CDVA in decimal fraction was 0.75 ± 0.03 (range 0.6–0.80) and mean central endothelial cell density was 1480.41 ± 320.56 cells/mm2 (range, 591–1950 cells/mm2). Mean cell loss at 6 months was 27.67 ± 16.03%. Three (11.53%) eyes had significant graft detachment that required re-bubbling. No episodes of immunological graft rejection were documented. # Conclusions Our experience shows that DMEK is a useful technique to treat endothelial graft failure following PK. Compared to repeat PK, DMEK-specific surgical complications and postsurgical management should be expected.

Transplantation of endothelium and Descemet's membrane

Nowadays, endothelial keratoplasty has become an alternative to penetrating keratoplasty (PKP) in the management of corneal endothelial dysfunction. Descemet membrane endothelial keratoplasty (DMEK) is a relatively new corneal transplantation surgery technique suited for patients with endothelial insufficiency, an increasing number of surgeons are learning the graft preparation technique and the surgery itself after seeing its excellent postoperative visual outcomes and faster rehabilitation of patients. DMEK has significant advantages in comparison with automated and manual Descemet Stripping Endothelial Keratoplasty (DSAEK/DSEK) and PKP including lower risk of immunologic graft rejection (1-2%), lower cost of the procedure, and it does not require expensive equipment such as a microkeratome or a femtosecond laser device. Another advantage is that the corneal graft tissue can be used for several recipients - e.g. when the Descemet's membrane and endothelium are used for a patient with endothelial dysfunction of the cornea, the retained stroma and epithelium can be then used for another patient with pathology of these corneal layers. Key problematic issues regarding this surgery are the technical difficulties during graft preparation and during surgery itself, however the majority of surgeons report very good results after gaining some experience. The article reviews latest clinical trials on DMEK and describes its strengths and weaknesses.

Third-Party Allogeneic Mesenchymal Stromal Cells Prevent Rejection in a Pre-sensitized High-Risk Model of Corneal Transplantation

High-risk cornea transplant recipients represent a patient population with significant un-met medical need for more effective therapies to prevent immunological graft rejection due to heightened anti-donor immune response. In this study, a rat model of pre-existing anti-donor immunity was developed in which corneal allografts were rejected earlier than in non-pre-sensitized recipients. In this model, third-party (non-donor, non-recipient strain) allogeneic mesenchymal stromal cells (allo-MSC) were administered intravenously 7 and 1 days prior to transplantation. Rejection-free graft survival to 30 days post-transplant improved from 0 to 63.6% in MSC-treated compared to vehicle-treated control animals (p = < 0.0001). Pre-sensitized animals that received third-party allo-MSC prior to transplantation had significantly higher proportions of CD45+CD11b+ B220+ monocytes in the lungs 24 h after the second MSC injection and significantly higher proportions of CD4+ FoxP3+ regulatory T cells in the graft-draining lymph nodes at the average day of rejection of control animals. In in vitro experiments, third-party allo-MSC polarized primary lung-derived CD11b/c+ myeloid cells to a more anti-inflammatory phenotype, as determined by cytokine profile and conferred them with the capacity to suppress T cell activation via prostaglandin E2 and TGFβ1. In experiments designed to further validate the clinical potential of the protocol, thawed cryopreserved, third-party allo-MSC were shown to be similarly potent at prolonging rejection-free corneal allograft survival as their freshly-cultured counterparts in the pre-sensitized high-risk model. Furthermore, thawed cryopreserved third-party allo-MSC could be co-administered with mycophenolate mofetil without adversely affecting their immunomodulatory function. In conclusion, a clinically-relevant protocol consisting of two intravenous infusions of third-party allo-MSC during the week prior to transplantation, exerts a potent anti-rejection effect in a pre-sensitized rat model of high-risk corneal allo-transplantation. This immune regulatory effect is likely to be mediated in the immediate post-transplant period through the promotion, by allo-MSC, of alternatively-activated macrophages in the lung and, later, by enhanced regulatory T-cell numbers.

UV light crosslinking regresses mature corneal blood and lymphatic vessels and promotes subsequent high-risk corneal transplant survival.

Immunologic graft rejection is the main complication after corneal transplant into pathologically prevascularized so‐called high‐risk eyes. The aim of this study was to evaluate whether ultraviolet (UV) light crosslinking can regress pathologic corneal blood and lymphatic vessels and thereby improve subsequent graft survival. Using the murine model of suture‐induced corneal neovascularization, we found that corneal crosslinking with UVA light and riboflavin regressed both preexisting blood and lymphatic vessels significantly via induction of apoptosis in vascular endothelial cells. In addition, macrophages and CD45+ cell counts were significantly reduced. Consistently, corneal crosslinking reduced keratocyte density and corneal thickness without affecting corneal nonvascular endothelial cells, iris, and lens depending on the crosslinking duration. Furthermore, using the murine model of corneal transplant, long‐term graft survival was significantly promoted (P < .05) and CD4+ CD25+FoxP3+ T regulatory cells were upregulated (P < .01) in high‐risk eyes preoperatively treated with crosslinking. Our results suggest UV light crosslinking as a novel method to regress both pathologic corneal blood and lymphatic vessels and to reduce CD45+ inflammatory cells. Furthermore, this study demonstrates for the first time that preoperative corneal crosslinking in prevascularized high‐risk eyes can significantly improve subsequent graft survival and may become a promising novel therapy in the clinic.

MHC matching improves engraftment of iPSC-derived neurons in non-human primates

The banking of human leukocyte antigen (HLA)-homozygous-induced pluripotent stem cells (iPSCs) is considered a future clinical strategy for HLA-matched cell transplantation to reduce immunological graft rejection. Here we show the efficacy of major histocompatibility complex (MHC)-matched allogeneic neural cell grafting in the brain, which is considered a less immune-responsive tissue, using iPSCs derived from an MHC homozygous cynomolgus macaque. Positron emission tomography imaging reveals neuroinflammation associated with an immune response against MHC-mismatched grafted cells. Immunohistological analyses reveal that MHC-matching reduces the immune response by suppressing the accumulation of microglia (Iba-1+) and lymphocytes (CD45+) into the grafts. Consequently, MHC-matching increases the survival of grafted dopamine neurons (tyrosine hydroxylase: TH+). The effect of an immunosuppressant, Tacrolimus, is also confirmed in the same experimental setting. Our results demonstrate the rationale for MHC-matching in neural cell grafting to the brain and its feasibility in a clinical setting.

Keratolimbal allograft

Keratolimbal allograft (KLAL) transplants limbal tissue attached to a corneoscleral carrier from a cadaveric donor to deliver a large number of stem cells to the recipient. The present article will provide a review of KLAL focusing on the recent literature. Recent findings pertain to tissue selection, immunosuppression and adverse event profiles, and postoperative complications (particularly related to immunologic rejection). KLAL permits the treatment of limbal stem cell deficiency eyes when there is no available living-related or autograft tissue with minimal risk of irreversible toxicity from modern systemic immunosuppression. The prevention of immunologic graft rejection with the use of systemic immunosuppression after KLAL is critical and may require extending systemic immunosuppression treatment longer than previously thought. With vigilant postoperative management, KLAL can allow successful treatment of the most severely diseased eyes.

Functional Results and Graft Failure after Repeat Keratoplasty

Background and Purpose Keratoplasty is the oldest and most successful transplantation method in man. Despite the immunological privilege of the cornea, the graft fails in up to 10 % of patients, depending on corneal disease, quality of donor tissue and patient compliance, and repeat keratoplasty may then be necessary. The aim of this study was to verify factors which affect the functional result and graft survival after repeat keratoplasty. Patients and Methods In this single centre, consecutive retrospective case series, patients were included who were treated at Department of Ophthalmology, Saarland University Medical Centre with repeat keratoplasty between January 1st 2001 and December 31st 2010. Data were recorded with an Access Database from the medical records and statistically analysed with SPSS 19.0. The surgical reports and the results from the follow-up examinations concentrated on visual acuity, intraocular pressure, endothelial cell density, corneal topography and tomography and corneal graft reactions. Results The results of the study showed that trephination with the excimer laser was significantly superior (p = 0.009) to mechanical trephination with a motor trephine with respect to corrected visual acuity. Corrected visual acuity after 2 years was 0.39 in the laser group, compared to 0.16 in the group with mechanical trephination. A graft diameter under 7.5 mm showed a significant negative impact on postkeratoplasty astigmatism (p = 0.004). After a follow-up period of 120 months, the rate of immunological graft rejection was 20/60 % (p = 0.259) in the patient group with graft diameters ≤ 7.5 mm/> 7.5 mm, respectively. Conclusion The present study shows that repeat keratoplasty using excimer laser gives better functional rehabilitation, if corneal morphology permits this (for example, the vascularisation). However, the trephination method has no significant impact on graft survival. The basic principle for repeat keratoplasties is that the diameter of the graft should be as great as possible but as small as necessary.

Успешное использование флюдарабина в посттрансплантационной терапии частичного иммунологического отторжения гемопоэтического трансплантата у детей

Успешное использование флюдарабина в посттрансплантационной терапии частичного иммунологического отторжения гемопоэтического трансплантата у детей

Long-Term Outcomes of High-Risk Keratoplasty in Patients Receiving Systemic Immunosuppression.

Immunological graft rejection after corneal transplantation remains the leading cause of graft failure. Systemic immunosuppression is used for keratoplasty at a high risk of rejection to improve graft survival. We examined the long-term outcomes of high-risk corneal grafts in patients receiving systemic immunosuppression. Thirty-five corneal transplants with a high risk of rejection were identified from 29 patients within a regional immunosuppression service in the United Kingdom. Definition of keratoplasty at "high risk" of rejection included one or more of the following: a history of ipsilateral graft rejection and/or failure, 2 or more quadrants of stromal vascularization, perforation or ocular inflammation at the time of surgery, presence of atopy, and a large-diameter (≥9 mm) graft. Median follow-up duration was 5 years after transplantation. Graft survival at 5 years in patients receiving systemic immunosuppression was 73.5%. Rejection episodes occurred in 14 grafts (40%); these episodes were reversible in 10 grafts (71%). Indications for transplantation were mostly visual (n = 19; 54%) and tectonic (n = 14; 40%). Eighteen grafts (51%) had 2 or more high-risk characteristics. Most patients (n = 20; 69%) received monotherapy, commonly with tacrolimus (n = 15; 52%) or mycophenolate mofetil (n = 8; 28%). Three patients (10%) experienced severe systemic side effects. Median "day-to-day" logMAR visual acuity was 0.5 in grafts for all indications and 0.2 for visual indications. Systemic immunosuppression in patients with high-risk keratoplasty seems to improve graft survival with a median follow-up duration of 5 years and is tolerated by most patients. Despite rejection episodes occurring in 40% of grafts, these were mostly reversible.

Xenogeneic cell therapeutics: Treatment of type 1 diabetes using porcine pancreatic islets and islet cells

In view of the existing shortage of human donor organs and tissues, xenogeneic cell therapeutics (xCT) offer an alternative for adequate treatment. In particular, porcine pancreatic islets and islet cells have already entered the field of experimental therapy for type-1 diabetes mellitus (T1DM) patients. Thereby, xCT depict challenging products with a glance on medical, ethical, and regulatory questions. With cross-species transplantation (xenotransplantation), the risk of immunological graft rejection as well as the risk of infectious transmission of microbial and viral pathogens must be considered. This includes the bidirectional transmission of microorganisms from graft to host as well as from host to graft. Crossing the border of species requires a critical risk-benefit evaluation as well as a thorough longtime surveillance of transplant recipients after treatment. The international legal and regulatory requirements for xCT are inter alia based on the World Health Organization criteria summarized in the Changsha Communiqué (2008). In the European Union, they were reflected by the European Medicines Agency (EMA) Guideline on Xenogeneic Cell-based Medicinal Products following the implementation of the Regulation on Advanced Therapies (ATMP). On the basis of this regulation, the first non-clinical and clinical experiences were obtained for porcine islets. The results suggest that supportive treatment of T1DM risk patients with xCT may be an alternative to established allogeneic organ transplantation in the future.