Rat Model of Type 2 Diabetes Mellitus Recapitulates Human Disease in the Anterior Segment of the Eye.

Changes in the anterior segment of the eye due to type 2 diabetes mellitus (T2DM) are not well-characterized, in part due to the lack of a reliable animal model. This study evaluated changes in the anterior segment, including crystalline lens health, corneal endothelial cell density, aqueous humor metabolites, and ciliary body vasculature, in a rat model of T2DM compared with human eyes. Male Sprague-Dawley rats were fed a high-fat diet (45% fat) or normal diet, and rats fed the high-fat diet were injected with streptozotocin intraperitoneally to generate a model of T2DM. Cataract formation and corneal endothelial cell density were assessed using microscopic analysis. Diabetes-related rat aqueous humor alterations were assessed using metabolomics screening. Transmission electron microscopy was used to assess qualitative ultrastructural changes ciliary process microvessels at the site of aqueous formation in the eyes of diabetic rats and humans. Eyes from the diabetic rats demonstrated cataracts, lower corneal endothelial cell densities, altered aqueous metabolites, and ciliary body ultrastructural changes, including vascular endothelial cell activation, pericyte degeneration, perivascular edema, and basement membrane reduplication. These findings recapitulated diabetic changes in human eyes. These results support the use of this model for studying ocular manifestations of T2DM and support a hypothesis postulating blood-aqueous barrier breakdown and vascular leakage at the ciliary body as a mechanism for diabetic anterior segment pathology.

Squishy matters - Corneal mechanobiology in health and disease.

The cornea, as a dynamic and responsive tissue, constantly interacts with mechanical forces in order to maintain its structural integrity, barrier function, transparency and refractive power. Cells within the cornea sense and respond to various mechanical forces that fundamentally regulate their morphology and fate in development, homeostasis and pathophysiology. Corneal cells also dynamically regulate their extracellular matrix (ECM) with ensuing cell-ECM crosstalk as the matrix serves as a dynamic signaling reservoir providing biophysical and biochemical cues to corneal cells. Here we provide an overview of mechanotransduction signaling pathways then delve into the recent advances in corneal mechanobiology, focusing on the interplay between mechanical forces and responses of the corneal epithelial, stromal, and endothelial cells. We also identify species-specific differences in corneal biomechanics and mechanotransduction to facilitate identification of optimal animal models to study corneal wound healing, disease, and novel therapeutic interventions. Finally, we identify key knowledge gaps and therapeutic opportunities in corneal mechanobiology that are pressing for the research community to address especially pertinent within the domains of limbal stem cell deficiency, keratoconus and Fuchs' endothelial corneal dystrophy. By furthering our understanding corneal mechanobiology, we can contextualize discoveries regarding corneal diseases as well as innovative treatments for them.

Type II Diabetes Mellitus Causes Extracellular Matrix Alterations in the Posterior Cornea That Increase Graft Thickness and Rigidity.

Purpose: There is a pressing need to investigate the impact of type II diabetes mellitus on the posterior cornea in donor tissues given its increasing prevalence and potential impact on endothelial keratoplasty surgical outcomes. Methods: Immortalized human cultured corneal endothelial cells (CECs; HCEC-B4G12) were grown in hyperglycemic media for 2 weeks. Extracellular matrix (ECM) adhesive glycoprotein expression and advanced glycation end products (AGEs) in cultured cells and corneoscleral donor tissues, as well as the elastic modulus for the Descemet membrane (DMs) and CECs of diabetic and nondiabetic donor corneas, were measured. Results: In CEC cultures, increasing hyperglycemia resulted in increased transforming growth factor beta-induced (TGFBI) protein expression and colocalization with AGEs in the ECM. In donor corneas, the thicknesses of the DM and the interfacial matrix (IFM) between the DM and stroma both increased from 8.42 ± 1.35 µm and 0.504 ± 0.13 µm in normal corneas, respectively, to 11.13 ± 2.91 µm (DM) and 0.681 ± 0.24 µm (IFM) in non-advanced diabetes (P = 0.013 and P = 0.075, respectively) and 11.31 ± 1.76 µm (DM) and 0.744 ± 0.18 µm (IFM) in advanced diabetes (AD; P = 0.0002 and P = 0.003, respectively). Immunofluorescence in AD tissues versus controls showed increased AGEs (P < 0.001) and markedly increased labeling intensity for adhesive glycoproteins, including TGFBI, that colocalized with AGEs. The elastic modulus significantly increased between AD and control tissues for the DMs (P < 0.0001) and CECs (P < 0.0001). Conclusions: Diabetes and hyperglycemia alter human CEC ECM structure and composition, likely contributing to previously documented complications of endothelial keratoplasty using diabetic donor tissue, including tearing during graft preparation and reduced graft survival. AGE accumulation in the DM and IFM may be a useful biomarker for determining diabetic impact on posterior corneal tissue.

Mice Deficient in TAZ (Wwtr1) Demonstrate Clinical Features of Late-Onset Fuchs' Endothelial Corneal Dystrophy.

Purpose: We sought to define the role of Wwtr1 in murine ocular structure and function and determine the role of mechanotransduction in Fuchs' endothelial corneal dystrophy (FECD), with emphasis on interactions between corneal endothelial cells (CEnCs) and Descemet's membrane (DM). Methods: A Wwtr1 deficient mouse colony was established, and advanced ocular imaging, atomic force microscope (AFM), and histology/immunofluorescence were performed. Corneal endothelial wound healing was assessed using cryoinjury and phototherapeutic keratectomy in Wwtr1 deficient mice. Expression of WWTR1/TAZ was determined in the corneal endothelium from normal and FECD-affected patients; WWTR1 was screened for coding sequence variants in this FECD cohort. Results: Mice deficient in Wwtr1 had reduced CEnC density, abnormal CEnC morphology, softer DM, and thinner corneas versus wildtype controls by 2 months of age. Additionally, CEnCs had altered expression and localization of Na/K-ATPase and ZO-1. Further, Wwtr1 deficient mice had impaired CEnC wound healing. The WWTR1 transcript was highly expressed in healthy human CEnCs comparable to other genes implicated in FECD pathogenesis. Although WWTR1 mRNA expression was comparable between healthy and FECD-affected patients, WWTR1/TAZ protein concentrations were higher and localized to the nucleus surrounding guttae. No genetic associations were found in WWTR1 and FECD in a patient cohort compared to controls. Conclusions: There are common phenotypic abnormalities seen between Wwtr1 deficient and FECD-affected patients, suggesting that Wwtr1 deficient mice could function as a murine model of late-onset FECD. Despite the lack of a genetic association between FECD and WWTR1, aberrant WWTR1/TAZ protein subcellular localization and degradation may play critical roles in the pathogenesis of FECD.

Metabolic and proteomic indications of diabetes progression in human aqueous humor.

Diabetes mellitus is a multiorgan systemic disease impacting numerous ocular structures that results in significant ocular morbidity and often results in more frequent corneal and glaucoma surgeries for affected individuals. We hypothesize that the systemic metabolic and proteomic derangement observed in the progression of diabetes influences the composition of the aqueous humor (AH), which ultimately impacts the anterior segment health of the eye. To identify changes associated with diabetes progression, we mapped the metabolite profile and proteome of AH samples from patients with varying severities of type II diabetes (T2DM). Patients were classified as nondiabetic (ND or control), non-insulin-dependent diabetic without advanced features of disease (NAD-ni), insulin-dependent diabetic without advanced features (NAD-i), or diabetic with advanced features (AD). AH samples collected from the anterior chamber during elective ophthalmic surgery were evaluated for metabolite and protein expression changes associated with diabetic severity via gas chromatography/mass spectrometry and ultra-high performance liquid chromatography tandem mass spectrometry, respectively. Metabolic and proteomic pathway analyses were conducted utilizing MetaboAnalyst 4.0 and Ingenuity Pathway Analysis. A total of 14 control, 12 NAD-ni, 4 NAD-I, and 14 AD samples were included for analysis. Elevated levels of several branched amino acids (e.g., valine, leucine, isoleucine), and lipid metabolites (e.g., palmitate) were found only with increasing diabetic severity (i.e., the AD group). Similar proteomic trends were noted in amino acid and fatty acid metabolism and the unfolded protein/stress response. These results represent the first report of both metabolomic and proteomic evaluation of aqueous humor. Diabetes results in metabolic and proteomic perturbations detectable in the AH, and unique changes become manifest as T2DM severity worsens. Changes in AH composition may serve as an indicator of disease severity, risk assessment of anterior segment cells and structures, and potential future therapies.

Solubilized ubiquinol for preserving corneal function.

Defective cellular metabolism, impaired mitochondrial function, and increased cell death are major problems that adversely affect donor tissues during hypothermic preservation prior to transplantation. These problems are thought to arise from accumulated reactive oxygen species (ROS) inside cells. Oxidative stress acting on the cells of organs and tissues preserved in hypothermic conditions before surgery, as is the case for cornea transplantation, is thought to be a major reason behind cell death prior to surgery and decreased graft survival after transplantation. We have recently discovered that ubiquinol - the reduced and active form of coenzyme Q10 and a powerful antioxidant - significantly enhances mitochondrial function and reduces apoptosis in human donor corneal endothelial cells. However, ubiquinol is highly lipophilic, underscoring the need for an aqueous-based formulation of this molecule. Herein, we report a highly dispersible and stable formulation comprising a complex of ubiquinol and gamma cyclodextrin (γ-CD) for use in aqueous-phase ophthalmic products. Docking studies showed that γ-CD has the strongest binding affinity with ubiquinol compared to α- or ß-CD. Complexed ubiquinol showed significantly higher stability compared to free ubiquinol in different aqueous ophthalmic products including Optisol-GS® corneal storage medium, balanced salt solution for intraocular irrigation, and topical Refresh® artificial tear eye drops. Greater ROS scavenging activity was noted in a cell model with high basal metabolism and ROS generation (A549) and in HCEC-B4G12 human corneal endothelial cells after treatment with ubiquinol/γ-CD compared to free ubiquinol. Furthermore, complexed ubiquinol was more effective at lowering ROS, and at far lower concentrations, compared to free ubiquinol. Complexed ubiquinol inhibited lipid peroxidation and protected HCEC-B4G12 cells against erastin-induced ferroptosis. No evidence of cellular toxicity was detected in HCEC-B4G12 cells after treatment with complexed ubiquinol. Using a vertical diffusion system, a topically applied inclusion complex of γ-CD and a lipophilic dye (coumarin-6) demonstrated transcorneal penetrance in porcine corneas and the capacity for the γ-CD vehicle to deliver drug to the corneal endothelium. Using the same model, topically applied ubiquinol/γ-CD complex penetrated the entire thickness of human donor corneas with markedly greater ubiquinol retention in the endothelium compared to free ubiquinol. Lastly, the penetrance of ubiquinol/γ-CD complex was assayed using human donor corneas preserved for 7 days in Optisol-GS® per standard industry practices, and demonstrated higher amounts of ubiquinol retained in the corneal endothelium compared to free ubiquinol. In summary, ubiquinol complexed with γ-CD is a highly stable composition that can be incorporated into a variety of aqueous-phase products for ophthalmic use including donor corneal storage media and topical eye drops to scavenge ROS and protect corneal endothelial cells against oxidative damage.

Cell-Matrix Interactions in the Eye: From Cornea to Choroid.

The extracellular matrix (ECM) plays a crucial role in all parts of the eye, from maintaining clarity and hydration of the cornea and vitreous to regulating angiogenesis, intraocular pressure maintenance, and vascular signaling. This review focuses on the interactions of the ECM for homeostasis of normal physiologic functions of the cornea, vitreous, retina, retinal pigment epithelium, Bruch's membrane, and choroid as well as trabecular meshwork, optic nerve, conjunctiva and tenon's layer as it relates to glaucoma. A variety of pathways and key factors related to ECM in the eye are discussed, including but not limited to those related to transforming growth factor-ß, vascular endothelial growth factor, basic-fibroblastic growth factor, connective tissue growth factor, matrix metalloproteinases (including MMP-2 and MMP-9, and MMP-14), collagen IV, fibronectin, elastin, canonical signaling, integrins, and endothelial morphogenesis consistent of cellular activation-tubulogenesis and cellular differentiation-stabilization. Alterations contributing to disease states such as wound healing, diabetes-related complications, Fuchs endothelial corneal dystrophy, angiogenesis, fibrosis, age-related macular degeneration, retinal detachment, and posteriorly inserted vitreous base are also reviewed.

Mitophagy: An Emerging Target in Ocular Pathology.

Mitochondrial function is essential for the viability of aerobic eukaryotic cells, as mitochondria provide energy through the generation of adenosine triphosphate (ATP), regulate cellular metabolism, provide redox balancing, participate in immune signaling, and can initiate apoptosis. Mitochondria are dynamic organelles that participate in a cyclical and ongoing process of regeneration and autophagy (clearance), termed mitophagy specifically for mitochondrial (macro)autophagy. An imbalance in mitochondrial function toward mitochondrial dysfunction can be catastrophic for cells and has been characterized in several common ophthalmic diseases. In this article, we review mitochondrial homeostasis in detail, focusing on the balance of mitochondrial dynamics including the processes of fission and fusion, and provide a description of the mechanisms involved in mitophagy. Furthermore, this article reviews investigations of ocular diseases with impaired mitophagy, including Fuchs endothelial corneal dystrophy, primary open-angle glaucoma, diabetic retinopathy, and age-related macular degeneration, as well as several primary mitochondrial diseases with ocular phenotypes that display impaired mitophagy, including mitochondrial encephalopathy lactic acidosis stroke, Leber hereditary optic neuropathy, and chronic progressive external ophthalmoplegia. The results of various studies using cell culture, animal, and human tissue models are presented and reflect a growing awareness of mitophagy impairment as an important feature of ophthalmic disease pathology. As this review indicates, it is imperative that mitophagy be investigated as a targetable mechanism in developing therapies for ocular diseases characterized by oxidative stress and mitochondrial dysfunction.

Optimizing Visualization of Descemet Membrane Endothelial Keratoplasty Tissue: Assessing the Impact of Trypan Blue Exposure on Stain Duration and Corneal Endothelial Cell Function.

PURPOSE: To assess how trypan blue staining affects Descemet membrane endothelial keratoplasty (DMEK) graft visibility and corneal endothelial cell (CEC) mitochondrial respiration. METHODS: DMEK grafts (n = 20) were stained with trypan blue 0.06% for 1, 3, 5, or 10 minutes. Each graft was injected into an artificial anterior chamber. Surgery was simulated with tapping and sweeping motions on the corneal surface and injections of balanced salt solution (BSS). Graft visibility was assessed at 5, 10, 20, and 30 minutes. Effects of trypan blue on mitochondrial respiration were assessed using primary CECs cultured from donor corneas (n = 43). Treatment wells exposed to trypan blue 0.06% (1, 5, or 30 minutes) and donor-matched control wells to methylene blue 1% (1 minute) or BSS (1, 5, or 30 minutes) were assayed for key respiration parameters. RESULTS: After 5 minutes of surgical manipulation, grafts stained for 5 minutes were significantly more visible than grafts stained for 1 or 3 minutes; there was no added benefit of staining for 10 minutes. After 10 minutes of surgical manipulation, grafts stained for 3 minutes were more visible than grafts stained for 1 minute, without additional benefits of staining ≥5 minutes. No visibility differences were observed after ≥20 minutes of surgical manipulation. CEC mitochondrial respiration did not change significantly following trypan blue exposure for all intervals tested compared to BSS. CONCLUSIONS: Staining DMEK grafts with trypan blue for 3 to 5 minutes optimizes visibility during surgical manipulation without mitochondrial impairment. Corneal surgeons learning DMEK will benefit from optimizing this critical step.

Ubiquinol Supplementation of Donor Tissue Enhances Corneal Endothelial Cell Mitochondrial Respiration.

PURPOSE: To determine whether ubiquinol improves mitochondrial function and cell viability in human donor corneal endothelial cells during hypothermic corneal tissue storage. METHODS: Endothelial cell Descemet membrane tissues were treated with 10 µM ubiquinol, the reduced form of the antioxidant coenzyme Q10, for 5 days in Optisol-GS storage media before assaying for mitochondrial activity using extracellular flux analysis of oxygen consumption. In addition, endothelial cell Descemet membrane tissues were analyzed for cell viability using apoptosis and necrosis assays. Control tissues from mate corneas were treated with diluent only, and comparisons were analyzed for differences. RESULTS: A total of 13 donor corneal tissues with a mean (SEM) preservation time of 11.8 days (0.4) were included for the analysis. Treatment with 10 µM ubiquinol increased spare respiratory capacity by 174% (P = 0.001), maximal respiration by 93% (P = 0.003), and proton leak by 80% (P = 0.047) compared with controls. Cells treated with ubiquinol had no significant change in cell necrosis or apoptosis. CONCLUSIONS: Preliminary testing in donor corneal tissue at specified doses indicates that ubiquinol may be a useful biocompatible additive to hypothermic corneal storage media that increases corneal endothelial cell mitochondrial function. Additional investigations are indicated to further study and optimize the dose and formulation of ubiquinol for use in preserving donor corneal tissue function during hypothermic storage.

The effects of diabetes mellitus on the corneal endothelium: A review.

The corneal endothelium plays a critical role in maintaining corneal clarity. There is an expected decline in cell density with age and disease, and maintaining the health of this cell layer is important as corneal endothelial cells generally are amitotic in vivo. Diabetes mellitus is a highly prevalent disease that damages the corneal endothelium. Diabetes causes structural and functional impairments in the corneal endothelium that decrease cellular reserve in response to stress. These effects have implications to consider for diabetic patients undergoing anterior segment surgery, and for corneal surgeons who use diabetic donor tissue and treat diabetic patients. In this review, we discuss the specifics of how diabetes mellitus impacts the corneal endothelium including alterations in cell morphology, cell density, ultrastructure, pump and barrier function, cataract surgery outcomes, and corneal transplant outcomes with attention to the use of diabetic donor tissue and diabetic transplant recipients.

Efficacy and Safety of Various Amphotericin B Concentrations on Candida albicans in Cold Storage Conditions.

PURPOSE: To determine the concentration of amphotericin B that would be both effective against Candida albicans contamination and safe for corneal endothelial cells (CECs) in cold storage conditions. METHODS: Triplicate media cultures were inoculated with 10 colony-forming units (CFUs)/mL of C. albicans (American Type Culture Collection 10231), supplemented with amphotericin B (0-20 µg/mL), stored in cold conditions (2°C-8°C) for 72 hours, and analyzed quantitatively for CFUs. C. albicans concentration in each sample was determined initially and after 6, 24, 48, and 72 hours of storage. CEC mitochondrial function (oxygen consumption rate), apoptosis, and necrosis were examined in donor corneas after 7 days of amphotericin B exposure and compared with untreated controls. CEC viability was also examined by calcein-AM staining and Fiji segmentation after 72 hours or 2 weeks of amphotericin B exposure to mimic potential eye bank practices. RESULTS: Amphotericin B concentrations of 1.25, 2.5, and 5.0 µg/mL resulted in 0.47, 1.11, and 1.21 log10 CFU reduction after only 6 hours of cold storage and continued to decrease to 3.50, 3.86, and 4.49 log10 reductions after 72 hours, respectively. By contrast, amphotericin B 0.255 µg/mL showed only 1.01 log10 CFU reduction after 72 hours of incubation. CEC mitochondrial function and viability did not differ in donor corneas exposed to amphotericin B ≤2.59 µg/mL compared with the controls. CONCLUSIONS: Optimal efficacy of amphotericin B against C. albicans is achieved in cold storage conditions at concentrations ≥1.25 µg/mL, and 2.5 µg/mL reduces Candida contamination by >90% after 6 hours of cold storage without sacrificing CEC health.

DMEK outcomes using nondiabetic grafts for recipients with diabetes mellitus.

PURPOSE: To compare Descemet membrane endothelial keratoplasty (DMEK) outcomes using nondiabetic grafts in diabetic and nondiabetic recipients. METHODS: All eyes that underwent DMEK between February 2013 and October 2016 (follow-up ≥3 months, without prior keratoplasty) were included. Recipients were divided into diabetic (insulin dependent [IDDM] or noninsulin dependent [NIDDM]) and nondiabetic groups. Main outcome measures included postoperative visual acuity, rebubble procedure rates, and graft failure rates. RESULTS: Of 334 eyes (243 subjects) included for analysis, 63 eyes (18.8%) were from diabetic recipients. At each timepoint, best-corrected visual acuity trended lower for IDDM recipients compared to NIDDM and nondiabetic recipients. There were no statistically significant differences in rebubble rates of diabetic compared to nondiabetic recipients (20.6% vs. 12.9%, p = 0.17), or IDDM compared to nondiabetic recipients (27.3% vs. 12.9%, p = 0.08; hazard ratio 2.26). Overall, 13 grafts (3.9%) failed (mean follow-up, 565 days; range, 90-1293 days). Graft failures did not differ between diabetic and nondiabetic recipients (4.0% vs. 4.9%, p = 0.15) regardless of subgroup (p = 0.36). CONCLUSIONS: DMEK provides excellent outcomes for patients with and without diabetes. DMEK outcomes were excellent with improvements in visual acuity and low rates of graft failure. Our findings were unable to determine differences between rebubble procedure rates but do emphasize the need for further research using stratified groups based on diabetes severity.

Assessing the Effects of Ripasudil, a Novel Rho Kinase Inhibitor, on Human Corneal Endothelial Cell Health.

PURPOSE: To determine how the Rho kinase inhibitor, ripasudil, affects metabolic function and cell viability in donor human corneal endothelial cells (HCECs). METHODS: Endothelial cell-Descemet membrane (EDM) tissues were treated with 10 µM ripasudil and assayed for mitochondrial and glycolytic activity using extracellular flux analysis and then compared to untreated controls. In addition, EDM tissues with a 24-h ripasudil treatment and control tissues were exposed to 1 µM staurosporine to induce apoptosis and then analyzed for cell viability using apoptosis and necrosis assays. RESULTS: Mitochondrial respiration metrics, specifically maximal respiration (P = 0.758) and spare respiratory capacity (P = 0.777), did not differ among the 1-h ripasudil treatment, 24-h treatment, and untreated tissues. Glycolytic activity assays showed an increase in glycolytic capacity at 1 h compared to the 24-h exposure group (P = 0.049) and controls (P = 0.009). Following exposure to staurosporine, the percentage of apoptotic HCECs was lower (P = 0.009) in ripasudil-treated tissues (2.473%, standard error of the mean [SEM] 0.477%) compared to untreated controls (3.349%, SEM 0.566%). In contrast, the percentage of necrotic HCECs decreased but did not differ statistically (P = 0.158) between ripasudil-treated (3.789%, SEM 0.487%) and untreated (4.567%, SEM 0.571%) tissues. CONCLUSIONS: Exposures to ripasudil did not result in any detectable reduction in metabolic function for HCECs in an ex vivo donor tissue model, and an increase in glycolytic activity at the 1-h time point was detected. In addition, HCECs treated with ripasudil gained a protective effect against induced apoptosis, suggesting that ripasudil may help improve the integrity of the corneal endothelium.

Proteomic analysis of corneal endothelial cell-descemet membrane tissues reveals influence of insulin dependence and disease severity in type 2 diabetes mellitus.

The objective of this study was to characterize the proteome of the corneal endothelial cell layer and its basement membrane (Descemet membrane) in humans with various severities of type II diabetes mellitus compared to controls, and identify differentially expressed proteins across a range of diabetic disease severities that may influence corneal endothelial cell health. Endothelium-Descemet membrane complex tissues were peeled from transplant suitable donor corneas. Protein fractions were isolated from each sample and subjected to multidimensional liquid chromatography and tandem mass spectrometry. Peptide spectra were matched to the human proteome, assigned gene ontology, and grouped into protein signaling pathways unique to each of the disease states. We identified an average of 12,472 unique proteins in each of the endothelium-Descemet membrane complex tissue samples. There were 2,409 differentially expressed protein isoforms that included previously known risk factors for type II diabetes mellitus related to metabolic processes, oxidative stress, and inflammation. Gene ontology analysis demonstrated that diabetes progression has many protein footprints related to metabolic processes, binding, and catalysis. The most represented pathways involved in diabetes progression included mitochondrial dysfunction, cell-cell junction structure, and protein synthesis regulation. This proteomic dataset identifies novel corneal endothelial cell and Descemet membrane protein expression in various stages of diabetic disease. These findings give insight into the mechanisms involved in diabetes progression relevant to the corneal endothelium and its basement membrane, prioritize new pathways for therapeutic targeting, and provide insight into potential biomarkers for determining the health of this tissue.

Mitochondrial and Morphologic Alterations in Native Human Corneal Endothelial Cells Associated With Diabetes Mellitus.

Purpose: To characterize changes in the energy-producing metabolic activity and morphologic ultrastructure of corneal endothelial cells associated with diabetes mellitus. Methods: Transplant suitable corneoscleral tissue was obtained from donors aged 50 to 75 years. We assayed 3-mm punches of endothelium-Descemet membrane for mitochondrial respiration and glycolysis activity using extracellular flux analysis of oxygen and pH, respectively. Transmission electron microscopy was used to assess qualitative and quantitative ultrastructural changes in corneal endothelial cells and associated Descemet membrane. For purposes of analysis, samples were divided into four groups based on a medical history of diabetes regardless of type: (1) nondiabetic, (2) noninsulin-dependent diabetic, (3) insulin-dependent diabetic, and (4) insulin-dependent diabetic with specified complications due to diabetes (advanced diabetic). Results: In total, 229 corneas from 159 donors were analyzed. Insulin-dependent diabetic samples with complications due to diabetes displayed the lowest spare respiratory values compared to all other groups (P ≤ 0.002). The remaining mitochondrial respiration and glycolysis metrics did not differ significantly among groups. Compared to nondiabetic controls, the endothelium from advanced diabetic samples had alterations in mitochondrial morphology, pronounced Golgi bodies associated with abundant vesicles, accumulation of lysosomal bodies/autophagosomes, and focal production of abnormal long-spacing collagen. Conclusions: Extracellular flux analysis suggests that corneal endothelial cells of donors with advanced diabetes have impaired mitochondrial function. Metabolic findings are supported by observed differences in mitochondrial morphology of advanced diabetic samples but not controls. Additional studies are needed to determine the precise mechanism(s) by which mitochondria become impaired in diabetic corneal endothelial cells.

Assessing the Impact of Diabetes Mellitus on Donor Corneal Endothelial Cell Density.

PURPOSE: To quantify changes in endothelial cell density (ECD) of donor corneal tissue in relation to the presence or absence of a medical history of diabetes mellitus diagnosis, treatment, and complications. METHODS: A retrospective review was performed for all corneas collected at Iowa Lions Eye Bank between January 2012 and December 2015. For purposes of analysis, donor corneas were divided into 4 groups: nondiabetic, non-insulin-dependent diabetic, insulin-dependent diabetic without medical complications due to diabetes, and insulin-dependent diabetic with medical complications due to diabetes. ECD values (obtained through specular microscopy) and transplant suitability for endothelial transplantation (determined by the standard protocol of the eye bank) were compared among groups using linear mixed model analysis. RESULTS: In total, 4185 corneas from 2112 donors were included for analysis. Insulin-dependent diabetic samples with medical complications due to diabetes (N = 231 from 119 donors) showed lower ECD values compared with nondiabetic samples (-102 cells/mm, P = 0.049) and non-insulin-dependent diabetic samples (-117 cells/mm, P = 0.031). ECD values did not differ significantly among the remaining groups. The likelihood of suitability for endothelial transplantation did not differ among all 4 groups. CONCLUSIONS: Corneas from donors with insulin-dependent diabetes mellitus and medical complications resulting from the disease have lower mean ECD values compared with other donors. However, our analysis suggests that these corneas are equally likely to be included in the donor pool for corneal transplantation. Additional studies are needed to determine the mechanism(s) contributing to cell loss in donors with advanced diabetes and to assess associated endothelial cell functional impairment.

Incidence and Outcomes of Positive Donor Corneoscleral Rim Fungal Cultures after Keratoplasty.

PURPOSE: To determine the incidence of positive corneoscleral donor rim fungal cultures after keratoplasty and to report clinical outcomes of grafts with culture-positive donor rims. DESIGN: Retrospective cohort study. PARTICIPANTS: Consecutive donor corneas and keratoplasty recipients at a single tertiary referral center over 20 years. METHODS: Patient charts were reviewed to determine the incidence of positive donor rim fungal cultures and clinical outcomes of all grafts using contaminated tissue. MAIN OUTCOME MEASURES: The primary outcome measures were positive donor rim fungal culture results and the development of postkeratoplasty fungal infection using corresponding corneal tissue. The secondary outcome measure was the impact of postoperative prophylaxis on donor tissue-associated infections. RESULTS: A total of 3414 keratoplasty cases were included in the statistical analysis. Seventy-one cases (2.1%) were associated with a fungal culture-positive donor rim. Candida species were cultured in 40 cases (56.3%). There was a higher incidence of positive rim cultures over the last 5 years of the analytic period compared with the first 15 years (P = 0.018). Fungal keratitis developed in 4 cases (5.6%), and all patients required further surgical intervention to achieve cure. There were no cases of fungal endophthalmitis. Empiric antimycotic prophylaxis initiated at the time of positive culture result reduced the incidence of keratitis from 15.8% in untreated cases to 1.9% in treated cases (P = 0.056). CONCLUSIONS: Positive donor rim fungal cultures are uncommon, but carry an unacceptably high risk of postoperative fungal infection. This risk may be reduced with prophylactic antimycotic therapy when culture-positive donor rims are identified.

Elucidation of transcriptome-wide microRNA binding sites in human cardiac tissues by Ago2 HITS-CLIP.

MicroRNAs (miRs) have emerged as key biological effectors in human health and disease. These small noncoding RNAs are incorporated into Argonaute (Ago) proteins, where they direct post-transcriptional gene silencing via base-pairing with target transcripts. Although miRs have become intriguing biological entities and attractive therapeutic targets, the translational impacts of miR research remain limited by a paucity of empirical miR targeting data, particularly in human primary tissues. Here, to improve our understanding of the diverse roles miRs play in cardiovascular function and disease, we applied high-throughput methods to globally profile miR:target interactions in human heart tissues. We deciphered Ago2:RNA interactions using crosslinking immunoprecipitation coupled with high-throughput sequencing (HITS-CLIP) to generate the first transcriptome-wide map of miR targeting events in human myocardium, detecting 4000 cardiac Ago2 binding sites across >2200 target transcripts. Our initial exploration of this interactome revealed an abundance of miR target sites in gene coding regions, including several sites pointing to new miR-29 functions in regulating cardiomyocyte calcium, growth and metabolism. Also, we uncovered several clinically-relevant interactions involving common genetic variants that alter miR targeting events in cardiomyopathy-associated genes. Overall, these data provide a critical resource for bolstering translational miR research in heart, and likely beyond.

Effect of internal limiting membrane abrasion on retinal tissues in macular holes.

PURPOSE: The purpose of this study was to identify the structural and histological effects of a Tano diamond-dusted membrane scraper (DDMS) on the retinal surface after internal limiting membrane (ILM) abrasion in macular hole surgery. METHODS: Institutional experimental study was performed in 11 eyes. All eyes underwent ILM abrasion in the operating room with a DDMS for macular hole repair as an alternative to traditional ILM peeling. Three human donor eyes underwent an identical procedure in the laboratory. Retinal tissues were removed by ILM abrasion with a DDMS during vitrectomy for macular hole repair and retinal tissues remaining in human donor eyes. Main outcome measures were microscopic and immunohistological characteristics of instrument tip tissues and retinal structure after ILM abrasion. RESULTS: The tips of the Tano DDMS showed evidence of cellular membranes and ILM removal. The retinas showed distinct areas of lamellar ILM removal without penetration of the retinal nerve fiber layer (RNFL). CONCLUSIONS: Application of the Tano DDMS instrument is sufficient to remove membranes from the surface of the ILM and layers of the ILM without disruption of the underlying RNFL. Internal limiting membrane abrasion can be a useful and effective alternative to complete ILM removal for macular surgery.