Current Trends and Future Perspective of Mesenchymal Stem Cells and Exosomes in Corneal Diseases.

The corneal functions (transparency, refractivity and mechanical strength) deteriorate in many corneal diseases but can be restored after corneal transplantation (penetrating and lamellar keratoplasties). However, the global shortage of transplantable donor corneas remains significant and patients are subject to life-long risk of immune response and graft rejection. Various studies have shown the differentiation of multipotent mesenchymal stem cells (MSCs) into various corneal cell types. With the unique properties of immunomodulation, anti-angiogenesis and anti-inflammation, they offer the advantages in corneal reconstruction. These effects are widely mediated by MSC differentiation and paracrine signaling via exosomes. Besides the cell-free nature of exosomes in circumventing the problems of cell-fate control and tumorigenesis, the vesicle content can be genetically modified for optimal therapeutic affinity. The pharmacology and toxicology, xeno-free processing with sustained delivery, scale-up production in compliant to Good Manufacturing Practice regulations, and cost-effectiveness are the current foci of research. Routes of administration via injection, topical and/or engineered bioscaffolds are also explored for its applicability in treating corneal diseases.

Comparison of Optical Coherence Tomography Angiography to Indocyanine Green Angiography and Slit Lamp Photography for Corneal Vascularization in an Animal Model.

Corneal neovascularization (CoNV) could be treated by novel anti-angiogenic therapies, though reliable and objective imaging tools to evaluate corneal vasculature and treatment efficacy is still lacking. Optical coherence tomography angiography (OCTA) -currently designed as a retinal vascular imaging system- has been recently adapted for anterior-segment and showed good potential for successful imaging of CoNV. However, further development requires an animal model where parameters can be studied more carefully with histological comparison. Our study evaluated the OCTA in suture-induced CoNV in a rabbit model compared to indocyanine green angiography (ICGA) and slit-lamp photography (SLP). Overall vessel density measurements from OCTA showed good correlation with ICGA (0.957) and SLP (0.992). Vessels density by OCTA was higher than ICGA and SLP (mean = 20.77 ± 9.8%, 15.71 ± 6.28% and 17.55 ± 8.36%, respectively, P < 0.05). OCTA was able to depict CoNV similarly to SLP and ICGA, though it could better detect small vessels. Moreover, the depth and growth of vessels could be assessed using en-face and serial-scans. This study validated the OCTA in a rabbit model as a useful imaging tool for translational studies on CoNV. This may contribute to further studies on OCTA for anterior-segment including serial evaluation of emerging anti-angiogenic therapies.

Safety and Feasibility of Intrastromal Injection of Cultivated Human Corneal Stromal Keratocytes as Cell-Based Therapy for Corneal Opacities.

Purpose: To evaluate the safety and feasibility of intrastromal injection of human corneal stromal keratocytes (CSKs) and its therapeutic effect on a rodent early corneal opacity model. Methods: Twelve research-grade donor corneas were used in primary culture to generate quiescent CSKs and activated stromal fibroblasts (SFs). Single and repeated intrastromal injections of 2 to 4 × 104 cells to rat normal corneas (n = 52) or corneas with early opacities induced by irregular phototherapeutic keratectomy (n = 16) were performed, followed by weekly examination of corneal response under slit-lamp biomicroscopy and in vivo confocal microscopy with evaluation of haze level and stromal reflectivity, and corneal thickness using anterior segment optical coherence tomography (AS-OCT). Time-lapse tracing of Molday ION-labelled cells was conducted using Spectralis OCT and label intensity was measured. Corneas were collected at time intervals for marker expression by immunofluorescence, cell viability, and apoptosis assays. Results: Injected CSKs showed proper marker expression with negligible SF-related features and inflammation, hence maintaining corneal clarity and stability. The time-dependent loss of injected cells was recovered by repeated injection, achieving an extended expression of human proteoglycans inside rat stroma. In the early corneal opacity model, intrastromal CSK injection reduced stromal reflectivity and thickness, resulting in recovery of corneal clarity, whereas noninjected corneas were thicker and had haze progression. Conclusions: We demonstrated the safety, feasibility, and therapeutic efficacy of intrastromal CSK injection. The cultivated CSKs can be a reliable cell source for potential cell-based therapy for corneal opacities.

Incidence and Clinical Course of Immune Reactions after Descemet Membrane Endothelial Keratoplasty: Retrospective Analysis of 1000 Consecutive Eyes.

PURPOSE: To analyze the incidence and clinical course of graft rejection episodes after Descemet membrane endothelial keratoplasty (DMEK). DESIGN: Retrospective analysis of a consecutive, interventional case series. PARTICIPANTS: One thousand eyes that underwent DMEK from July 2011 through August 2015 at the Department of Ophthalmology, University of Cologne. METHODS: All cases with follow-up of at least 1 month were included (mean follow-up, 18.5 months). Patients with a graft rejection episode were followed up for 1 additional year. MAIN OUTCOME MEASURES: Incidence of graft rejection, best spectacle-corrected visual acuity (BSCVA), central corneal thickness (CCT), endothelial cell density (ECD), and need for regraft. RESULTS: Nine hundred five cases met the inclusion criteria. A graft rejection episode developed in 12 patients (estimated probability of rejection at 1 year, 0.9%; at 2 years, 2.3%; at 4 years, 2.3%). At time of rejection, 9 of 12 patients had stopped corticosteroids. Five patients were symptomatic and 7 did not note the rejection episode. Intensified topical corticosteroid therapy was started immediately after diagnosis of rejection. Two eyes decompensated and required a regraft, whereas the remaining 10 eyes required no regraft (BSCVA, 0.27±0.28 logarithm of the minimum angle of resolution [logMAR]; CCT, 554.1±39.1 µm at last visit before rejection vs. BSCVA, 0.21±0.15 logMAR; CCT, 540.0±15.0 µm 3 months after rejection). One year after the rejection episodes, BSCVA and CCT in these eyes remained unchanged when compared with the last visit before rejection (BSCVA, 0.15±0.11 logMAR; CCT, 533.8±26.0 µm). Significant changes were observed for ECD values (1741±274.5 cells/mm2 at last visit before rejection vs. 1356±380.3 cells/mm2 after 3 months [P = 0.04] and 1290±359.0 cells/mm2 after 1 year [P = 0.01]). CONCLUSIONS: The risk for graft rejection after DMEK is low, and an even smaller minority requires a regraft. After intensified local corticosteroid therapy, most patients show stable visual acuity and CCT, although ECD decreases. The occurrence of immune reactions up to 2 years after surgery predominantly in patients not receiving corticosteroids supports the prolonged use of corticosteroids after DMEK.

Intensified Early Postoperative Topical Steroids Do Not Influence Endothelial Cell Density After Descemet Membrane Endothelial Keratoplasty Combined With Cataract Surgery (Triple-DMEK).

PURPOSE: To investigate the effect of intensified postoperative topical steroid therapy after Descemet membrane endothelial keratoplasty combined with cataract surgery (Triple-DMEK) on postoperative endothelial cell density (ECD). METHODS: This comparative clinical study with historical controls was conducted at a tertiary hospital, specialized in corneal surgery. Patients undergoing DMEK or Triple-DMEK are included prospectively in the Cologne DMEK Database. Until April 2014, first week's postoperative standard therapy for lamellar keratoplasties was prednisolone acetate eye drops 1% applied 5× daily. After April 2014, first week's postoperative standard therapy changed to prednisolone acetate eye drops 1% applied hourly. We compared 75 consecutive eyes before (group 1) with 75 consecutive eyes after the change of therapy regimen (group 2). Patients received ECD analysis 3 and 6 months after surgery. RESULTS: ECD of grafts in group 1 before transplantation, and 3 months and 6 months after surgery was 2697 ± 218, 1765 ± 349, and 1703 ± 432 cells/mm, respectively. ECD of grafts in group 2 was 2696 ± 267, 1737 ± 450, and 1694 ± 482 cells/mm, respectively. Over 3 and 6 months, ECD in group 1 decreased by 35% ± 13% and 38% ± 18%, respectively. In group 2, ECD decreased by 36% ± 16% and 38% ± 16%, respectively. Neither absolute numbers nor decrease in ECD differed significantly between groups 1 and 2 at any time point (all P > 0.60). CONCLUSIONS: Intensified early postoperative topical steroid therapy during the first postoperative week does not stabilize ECD, nor does it have a toxic effect on endothelial cells during a follow-up of 6 months.

Impact of Donor Age on Descemet Membrane Endothelial Keratoplasty Outcome: Evaluation of Donors Aged 17-55 Years.

PURPOSE: To investigate whether the impression held by Descemet membrane endothelial keratoplasty (DMEK) surgeons that young donors are less suitable for DMEK is reflected in 1-year postoperative results. DESIGN: Retrospective, comparative, interventional case series. METHODS: Records of 1084 consecutive DMEKs were reviewed and matched with corresponding donor tissue data. Young donors (aged ≤55 years; subgroups: 10-40, 41-55) were compared with old donors (>55 years; subgroups: 56-65, >65). Outcome measures in DMEK recipients included best spectacle-corrected visual acuity (BSCVA), endothelial cell density (ECD), central corneal thickness (CCT) at 6 and 12 months, and rebubbling rate. RESULTS: Out of 529 included DMEKs, 94 (17.8%) were performed with young donor lamellae (mean donor age 49.31 ± 6.35 years; range: 17-55 years) and 435 (82.2%) with older donor tissue (mean age 70.68 ± 7.77 years; range: 56-90 years). Postoperative BSCVA, ECD, and CCT results were comparable in both groups at 6 and 12 months without statistically significant differences. Overall rebubbling rate in the young donor group was 42.6% and in the old donors was 53.3% (P = .058). Complication rates also did not differ significantly. CONCLUSION: Younger donor age seems not to affect the clinical outcome of DMEK surgery negatively within the first postoperative year, suggesting donor corneas with donor age down to 17 years as safe donor tissue for DMEK surgery.

Bilateral Descemet Membrane Endothelial Keratoplasty: Analysis of Clinical Outcome in First and Fellow Eye.

PURPOSE: To analyze the clinical outcomes, complications, comparability, and predictors of sequential bilateral Descemet membrane endothelial keratoplasty (DMEK). METHODS: Retrospective analyses were completed on 60 patients (120 eyes) with corneal endothelial disorders who underwent bilateral sequential DMEK. Main outcome measures were best-corrected visual acuity (BCVA), pachymetry, endothelial cell density, rebubbling frequency, and graft or nongraft-associated complications-as measured 6 and 12 months after surgery. RESULTS: BCVA, pachymetry, and endothelial cell loss did not differ significantly 6 and 12 months after surgery in first versus fellow eyes (P > 0.05, respectively). Graft and nongraft-associated complications such as graft detachment, graft failure, graft rejection, anterior chamber inflammation, and intraocular pressure decompensation did not differ significantly between first and fellow eyes (P > 0.05, respectively). The BCVA of first eyes 6 and 12 months after surgery correlates significantly with the 12-month BCVA of fellow eyes (r = 0.454, P = 0.031; r = 0.602, P = 0.001, respectively). Nevertheless, it was not possible to identify BCVA as an influencing variable on fellow eye outcome in regression modeling. Early sequential DMEK did not increase patients' risk of early immune reactions in their fellow eyes. CONCLUSIONS: The clinical outcomes of first and fellow eyes were comparable in patients after DMEK. This suggests patients will experience good fellow eye outcomes after successful first eye DMEK. When certain quality characteristics are maintained, donor differences do not significantly affect DMEK results. We found no significant correlation in postoperative complications in first and fellow eye DMEK surgeries.

Immediate Postoperative Intraocular Pressure Changes After Anterior Chamber Air Fill in Descemet Membrane Endothelial Keratoplasty.

PURPOSE: To monitor the intraocular pressure (IOP) changes immediately after anterior chamber air tamponade in Descemet membrane endothelial keratoplasty (DMEK). METHODS: Twenty-four patients undergoing DMEK and 16 patients undergoing rebubbling after DMEK were enrolled (n = 40). All DMEK patients had inferior iridectomy and nearly full intracameral air tamponade with an aimed IOP of 25 mm Hg at the end of surgery. The IOP was measured at 1, 2, 3, 5, 12, 24 hours and 1 week postoperatively. RESULTS: After anterior chamber air fill in DMEK, the IOP increased from preoperative baseline, 12.1 ± 2.9 mm Hg, to 26.3 ± 4.7 mm Hg, P < 0.001. Mean IOP was significantly elevated in the first 2 hours, 19.4 ± 10.5 mm Hg and 17.0 ± 7.4 mm Hg, P = 0.007 and 0.006, respectively. Then, it lowered to the baseline level, 14.0 ± 4.7 mm Hg, P > 0.05, and remained stable during follow-ups. An asymptomatic IOP elevation above 30 mm Hg was detected in 3 patients (12.5%) within the first 2 hours. None had preexisting glaucoma. Most episodes could be controlled by antiglaucoma medications and upright positioning. The pattern of IOP changes after rebubbling was similar to that after DMEK but the IOP dropped sharply to the baseline level after 1 hour and had no incidence of IOP elevations beyond 30 mm Hg. CONCLUSIONS: Adequate inferior iridectomy greatly alleviates the risk and severity of acute IOP rises after nearly full anterior chamber air tamponade in DMEK. Standard IOP adjustment at the end of DMEK surgery with postoperative IOP monitoring especially in the first 2 postoperative hours is advisable when there is no postoperative default air release.