Correlations of Corneal Endothelial Morphology and Corneal Thickness With Anterior Segment Parameters in Healthy Individuals

PURPOSE

The purpose of this study was to investigate the associations between central corneal endothelial cell density (ECD), endothelial morphology, and corneal thickness (central corneal thickness) with the anterior chamber depth, corneal volume (CV), white-to-white (WTW) distance, mean anterior chamber angle (CAmean), and gender in healthy individuals.

METHODS

This observational study included 136 healthy volunteers. The ECD, coefficient of variation of cell area, and hexagonal cell appearance ratio (%Hex) were measured by means of specular microscopy. The central corneal thickness, anterior chamber depth, CV, WTW distance, and the angle width of 12 points were taken by the Pentacam HR Scheimpflug anterior segment imaging. The arithmetical mean of the 12 points was considered as the CAmean. We used mixed effect linear regression model for the statistical analysis of the data.

RESULTS

ECD was positively correlated with CV ( P = 0.028), while after adjusting for age, it was negatively correlated with age ( P < 0.001). Coefficient of variation of cell area was positively correlated with CAmean ( P = 0.036), while after adjusting for age, it was positively correlated with age ( P < 0.001) and CAmean ( P = 0.005). Hex was negatively correlated with WTW ( P = 0.023) and CAmean ( P = 0.025), and after adjusting for age, this correlation remained the same ( P = 0.029 when correlated with WTW and P = 0.035 with CAmean).

CONCLUSIONS

There were significant changes in the morphology of the corneal endothelial cells in eyes with wider anterior chamber angle. Greater pleomorphism and polymegethism of the corneal endothelium was observed in healthy patients with wider CAmean. Deepening of the anterior chamber as myopia progresses could render the corneal endothelium more fragile and susceptible to mechanical stress, which is an area worthy of further study.

Corneal Endothelium Viability Assay Using Trypan Blue Dye After Preloaded Descemet Membrane Endothelial Keratoplasty Graft Preparation

PURPOSE

The purpose of this study was to establish a validated method, consistent with Eye Bank Association of America medical standards, for evaluating endothelial cell loss (ECL) from an entire Descemet membrane endothelial keratoplasty (DMEK) graft using trypan blue dye as an alternative to specular microscopy.

METHOD

Twenty-nine corneas were prepared for preloaded DMEK by a single technician, and the endothelium was stained with trypan blue dye for 30 seconds. The technician estimated total cell loss as a percentage of the graft and captured an image. Images were evaluated by a blinded technician using ImageJ software to determine ECL and compared with endothelial cell density from specular microscopy. Tissue processing intervals were analyzed for 4 months before and after implementation of this method.

RESULTS

For the 29 grafts, there was no statistically significant difference ( t test, P = 0.285) between ECL estimated by a processor (mean = 5.8%) and ECL calculated using an ImageJ software (mean = 5.1%). The processor tended to estimate greater ECL than the actual ECL determined by ImageJ (paired t test, P = 0.022). Comparatively, postprocessing endothelial cell density measured by specular microscopy were higher compared with the preprocessing endothelial cell density (mean = 4.5% P = 0.0006). After implementation of this evaluation method, DMEK graft processing time intervals were reduced by 47.9% compared with specular microscopy evaluation ( P < 0.001).

CONCLUSIONS

Our results show that visual ECL estimation using trypan blue staining by a DMEK graft processor is a reliable and efficient method for endothelial assessment. Unlike specular microscopy, this method achieves comprehensive visualization of the entire endothelium, reduces total time out of cold storage, and decreases total time required to prepare and evaluate DMEK grafts.

The proliferative effects of stem cells from apical papilla-conditioned medium on rat corneal endothelial cells

The cornea, positioned at the forefront of the eye, refracts the light for focusing images on the retina. Damage to this transparent structure can lead to various visual disorders. The corneal endothelial cells (CECs) are crucial for transparency and homeostasis, but lack the ability to reproduce. Significant damage results in structure destruction and vision impairment. While extensive research has aimed at the restoring the corneal endothelial layer, including endothelial proliferation for functional monolayers remains challenging. Our previous studies confirmed the proliferative activity of stem cells from apical papilla-conditioned medium (SCAP-CM) on the retinal pigmented epithelium as a single cell layer. This study investigates how SCAP-CM influences the proliferation and migration of CECs. Our results introduced Matrigel, as a new matrix component for in vitro culture of CECs. Moreover, 60% of SCAP-CM was able to stimulate CEC proliferation as well as migrate to repair wound healing during 24 h. Confluent CECs also expressed specific markers, ATP1a1, ZO-1 and CD56, indicative of CEC characteristics, aligning with the recapitulation of differentiation when forming a homogenous monolayer at the same level of isolated CECs without in vitro culture. These findings suggested that SCAP-CM administration could be useful for future preclinical and clinical applications.

Nicotinamide promotes the differentiation of functional corneal endothelial cells from human embryonic stem cells

Corneal transplantation represents the primary therapeutic approach for managing corneal endothelial dysfunction, but corneal donors remain scarce. Anterior chamber cell injection emerges as a highly promising alternative strategy for corneal transplantation, with pluripotent stem cells (PSC) demonstrating considerable potential as an optimal cell source. Nevertheless, only a few studies have explored the differentiation of functional corneal endothelial-like cells originating from PSC. In this investigation, a chemical-defined protocol was successfully developed for the differentiation of functional corneal endothelial-like cells derived from human embryonic stem cells (hESC). The application of nicotinamide (NAM) exhibited a remarkable capability in suppressing the fibrotic phenotype, leading to the generation of more homogeneous and well-distinctive differentiated cells. Furthermore, NAM effectively suppressed the expression of genes implicated in endothelial cell migration and extracellular matrix synthesis. Notably, NAM also facilitated the upregulation of surface marker genes specific to functional corneal endothelial cells (CEC), including CD26 (-) CD44 (-∼+-) CD105 (-) CD133 (-) CD166 (+) CD200 (-). Moreover, in vitro functional assays were performed, revealing intact barrier properties and Na+/K+-ATP pump functionality in the differentiated cells treated with NAM. Consequently, our findings provide robust evidence supporting the capacity of NAM to enhance the differentiation of functional CEC originating from hESC, offering potential seed cells for therapeutic interventions of corneal endothelial dysfunction.

Novel ROCK Inhibitors, Sovesudil and PHP-0961, Enhance Proliferation, Adhesion and Migration of Corneal Endothelial Cells

The loss or dysfunction of human corneal endothelial cells (hCEnCs) is a leading cause of blindness due to corneal failure. Corneal transplantation with a healthy donor cornea has been the only available treatment for corneal endothelial disease. However, the need for way to regenerate the CEnCs has been increased due to the global shortage of donor corneas. The aim of the study is to investigate whether novel Rho-kinase (ROCK) inhibitors can induce the cultivation and regeneration of hCEnCs. Cultured hCEnCs were treated with Y-27632, sovesudil, or PHP-0961 for 24 h. Cellular responses, including cell viability, cytotoxicity, proliferation, and Ki67 expression with ROCK inhibitors were evaluated. We also evaluated wound healing and cell adhesion assays. Porcine corneas were used ex vivo to evaluate the effects of Y-27632, sovesudil, and PHP-0961 on wound healing and regeneration. We performed live/dead cell assays and immunofluorescence staining for SRY (sex determining region Y)-box 2 (SOX2), β-catenin, and ZO-1 on porcine corneas after ROCK inhibitor treatments. Cell viability, cell proliferation rate, and the number of Ki67-positive cells were higher in Y-27632, sovesudil and PHP-0961 treated cells compared to the control. There was no difference in LDH cytotoxicity test between any groups. Cells treated with Y-27632, sovesudil and PHP-0961 showed faster migration, wound healing, and cell adhesion. In the porcine ex vivo experiments, wound healing, the number of live cells, and SOX2-positive cells were higher in Y-27632, sovesudil and PHP-0961 treated corneas. In all experiments, sovesudil and PHP-0961, the novel ROCK inhibitors, were equal or superior to the results of the ROCK inhibitor positive control, Y-27632. In conclusion, sovesudil and PHP-0961, novel ROCK inhibitors have the capacity to regenerate hCEnCs by enhancing cell proliferation and adhesion between cells.

Effect of Body Refrigeration Time on Cornea Donor Tissue

PURPOSE

To determine how early body refrigeration affects corneal donor transplant suitability and endothelial cell density.

METHODS

Donor information was obtained from the CorneaGen Eye Bank including demographics, time of death to preservation, and body refrigeration status, for donors between 2012 and 2016. The death to preservation interval was classified into 3 categories: 0 to 10, 10 to 20, and 20+ hours. Two primary logistic method models were fit using a main effects model and an interaction model to determine the association of body refrigeration on unsuitability of transplantation and endothelial cell density.

RESULTS

Analysis was from 42,929 donor eyes, with a mean (standard deviation) endothelial cell count of 2743 (415) cells/mm2. Fifty-nine percent of donor eyes were from male donors in the eye bank data set, and the mean death to preservation interval was 11.0 (5.6) hours for all eyes. Unsuitability for transplantation demonstrated a reduced adjusted odds ratio by 22% (OR = 0.78, P = 0.009) when the body was refrigerated during the death to preservation interval versus when the body was not refrigerated. Eyes that were refrigerated, however, exhibited no statistically significant difference in endothelial cell count from eyes that were not refrigerated (P = 0.12).

CONCLUSIONS

We demonstrate an appreciable effect of early body refrigeration on transplant suitability in this large cohort of eye bank eyes. There was no beneficial effect of body refrigeration on endothelial cell count.

Analysis of Cryopreservation Protocols and Their Harmful Effects on the Endothelial Integrity of Human Corneas

Corneal cryopreservation can partially solve the worldwide concern regarding donor cornea shortage for keratoplasties. In this study, human corneas were cryopreserved using two standard cryopreservation protocols that are employed in the Tissue Bank of the Teresa Herrera Hospital (Spain) to store corneas for tectonic keratoplasties (TK protocol) and aortic valves (AV protocol), and two vitrification protocols, VS55 and DP6. Endothelial viability and general corneal state were evaluated to determine the protocol that provides the best results. The potential corneal cryopreservation protocol was studied in detail taking into consideration some cryopreservation-related variables and the endothelial integrity and stroma arrangement of the resulting cryopreserved corneas. TK corneas showed mostly viable endothelial cells, while the others showed few (AV) or none (DP6 and VS55). The corneal structure was well maintained in TK and AV corneas. TK corneas showed endothelial acellular areas surrounded by injured cells and a normal-like stromal fiber arrangement. Cryoprotectant solutions of the TK protocol presented an increasing osmolality and a physiological pH value. Cooling temperature rate of TK protocol was of 1 °C/min to −40 °C and 3 °C/min to −120 °C, and almost all of dimethyl sulfoxide left the tissue after washing. Future studies should be done changing cryopreservation-related variables of the TK protocol to store corneas of optical grade.

Single cell transcriptomics reveals the heterogeneity of the human cornea to identify novel markers of the limbus and stroma

The cornea is the clear window that lets light into the eye. It is composed of five layers: epithelium, Bowman's layer, stroma, Descemet's membrane and endothelium. The maintenance of its structure and transparency are determined by the functions of the different cell types populating each layer. Attempts to regenerate corneal tissue and understand disease conditions requires knowledge of how cell profiles vary across this heterogeneous tissue. We performed a single cell transcriptomic profiling of 19,472 cells isolated from eight healthy donor corneas. Our analysis delineates the heterogeneity of the corneal layers by identifying cell populations and revealing cell states that contribute in preserving corneal homeostasis. We identified expression of CAV1, HOMER3 and CPVL in the corneal epithelial limbal stem cell niche, CKS2, STMN1 and UBE2C were exclusively expressed in highly proliferative transit amplifying cells, CXCL14 was expressed exclusively in the suprabasal/superficial limbus, and NNMT was exclusively expressed by stromal keratocytes. Overall, this research provides a basis to improve current primary cell expansion protocols, for future profiling of corneal disease states, to help guide pluripotent stem cells into different corneal lineages, and to understand how engineered substrates affect corneal cells to improve regenerative therapies.

Primary Graft Failure, Infection, and Endothelial Cell Density in Corneal Transplants With Increased Death-to-Preservation Time

PURPOSE

To ascertain whether death-to-preservation time (DPT) is associated with donor endothelial cell density (ECD), primary graft failure (PGF), and infection.

METHODS

Donor corneas aged older than 10 years with ECD 2000 to 4500 cells/mm2 were procured between 2011 and 2018 by a single eye bank. Donor corneas were analyzed retrospectively for the main outcome measures of PGF, infection, and ECD. Means and proportions of study parameters were compared between corneas with long and short DPT, defined as greater or less than 14 hours, respectively, excluding corneas with a history of intraocular surgery or diabetes. Multivariate analyses were performed using logistic regression, adjusting for donor age at time of death, history of diabetes mellitus, and history of cataract surgery.

RESULTS

Among 12,015 corneas, those with long DPT had a statistically but not clinically significant higher ECD than that of corneas with short DPT (2754 vs. 2724 cells/mm2, P < 0.01). There was no difference in PGF and infections in corneas with long versus short DPT (0.28% vs. 0.26%, P = 0.86; 0.43% vs. 0.29%, P = 0.51, respectively).

CONCLUSIONS

Longer DPT is not associated with a clinically meaningful reduction in donor ECD, PGF, or infection.

Comparison of the rabbit and human corneal endothelial proteomes regarding proliferative capacity

The shortage of human donor corneas has raised important concerns about engineering of corneal endothelial cells (CECs) for clinical use. However, due to the limited proliferative capacity of human CECs, driving them into proliferation and regeneration may be difficult. Unlike human CECs, rabbit CECs have a marked proliferative capacity. To clarify the potential reason for this difference, we analysed the proteomes of four human corneal endothelium samples and four rabbit corneal endothelium samples with quantitative label-free proteomics and downstream analysis. We discovered that vitamin and selenocompound metabolism and some signaling pathways such as NF-kappa B signaling pathway differed between the samples. Moreover, TGFβ, PITX2 and keratocan were distinctively expressed in rabbit samples, which might be associated with active proliferation in rabbit CECs. This study illustrates the proteomic differences between human and rabbit CECs and might promote CEC engineering strategies.

Effect of Rho-Associated Kinase Inhibitor and Mesenchymal Stem Cell-Derived Conditioned Medium on Corneal Endothelial Cell Senescence and Proliferation

This study aims to obtain sufficient corneal endothelial cells for regenerative application. We examined the combinatory effects of Rho-associated kinase (ROCK) inhibitor Y-27632 and mesenchymal stem cell-derived conditioned medium (MSC-CM) on the proliferation and senescence of rabbit corneal endothelial cells (rCECs). rCECs were cultured in a control medium, a control medium mixed with either Y-27632 or MSC-CM, and a combinatory medium containing Y-27632 and MSC-CM. Cells were analyzed for morphology, cell size, nuclei/cytoplasmic ratio, proliferation capacity and gene expression. rCECs cultured in a combinatory culture medium showed a higher passage number, cell proliferation, and low senescence. rCECs on collagen type I film showed high expression of tight junction. The cell proliferation marker Ki-67 was positively stained either in Y-27632 or MSC-CM-containing media. Genes related to cell proliferation resulted in negligible changes in MKI67, CIP2A, and PCNA in the combinatory medium, suggesting proliferative capacity was maintained. In contrast, all of these genes were significantly downregulated in the other groups. Senescence marker β-galactosidase-positive cells significantly decreased in either MSC-CM and/or Y-27632 mixed media. Senescence-related genes downregulated LMNB1 and MAP2K6, and upregulated MMP2. Cell cycle checkpoint genes such as CDC25C, CDCA2, and CIP2A did not vary in the combinatory medium but were significantly downregulated in either ROCK inhibitor or MSC-CM alone. These results imply the synergistic effect of combinatory culture medium on corneal endothelial cell proliferation and high cell number. This study supports high potential for translation to the development of human corneal endothelial tissue regeneration.

A clinical assessment of the anterior eye in arc welders

BACKGROUND

Corneal irradiation with high doses of ultraviolet-B (UVB) has been shown to damage the corneal endothelium in animals. Human occupational exposure to ultraviolet radiation (UVR) in welding is considered a risk for endothelial damage but the evidence for such an effect is limited.

METHODS

External eye photographs and non-contact specular micrographs (Topcon SP2000-P) were obtained from 102 white males aged between 32 and 62 years, 51 being arc welders (with 24 +/- 7 years experience) and 51 office workers. Most welders reported repeated occupational exposure to UVR (that is, welder's 'flashes').

RESULTS

Welders reported a higher level of ocular symptoms and a higher prevalence of pingueculae (47 versus 12 per cent), but only one case with pterygium. The average endothelial cell areas were the same in welders and office workers (398 +/- 55 microm(2) versus 400 +/- 56 microm(2); p = 0.868) as were the endothelial cell density (ECD) values (2,555 +/- 342 cells/mm(2) versus 2,541 +/- 308 cells/mm(2); p = 0.825). ECD decreased with years of welding experience (p < 0.01) but not faster than the decrease in ECD due to age.

CONCLUSIONS

Repeated occupational ultraviolet radiation exposure through welding is not associated with any obvious differences in the corneal endothelium. No differences were observed in either ECD or cell polymegethism. Despite the periodic welding flashes, the exposure levels are below those needed to cause damage to the corneal endothelium.

Biofabrication of chitosan/chitosan nanoparticles/polycaprolactone transparent membrane for corneal endothelial tissue engineering

We aimed to construct a biodegradable transparent scaffold for culturing corneal endothelial cells by incorporating chitosan nanoparticles (CSNPs) into chitosan/polycaprolactone (PCL) membranes. Various ratios of CSNP/PCL were prepared in the presence of constant concentration of chitosan and the films were constructed by solvent casting method. Scaffold properties including transparency, surface wettability, FTIR, and biocompatibility were examined. SEM imaging, H&E staining, and cell count were performed to investigate the HCECs adhesion. The phenotypic maintenance of the cells during culture was investigated by flow cytometry. Transparency and surface wettability improved by increasing the CSNP/PCL ratio. The CSNP/PCL 50/25, which has the lowest WCA, showed comparable transparency with human acellular corneal stroma. The scaffold was not cytotoxic and promoted the HCECs proliferation as evaluated by MTT assay. Cell counting, flow cytometry, SEM, and H&E results showed appropriate attachment of HCECs to the scaffold which formed a compact monolayer. The developed scaffold seems to be suitable for use in corneal endothelial regeneration in terms of transparency and biocompatibility.

Hydrodynamic forces influence the gene transcription of mechanosensitive intercellular junction associated genes in corneal endothelial cells

Mechanicals forces are known to influence cell behavior. In vivo, the corneal endothelium is under the influence of various mechanical forces, such as intraocular pressure (IOP) and fluid flow. In this study, we used a corneal bioreactor to understand the effect of these hydrodynamic forces on the transcription of intercellular junctions associated genes in the corneal endothelium. Native and tissue-engineered (TE) corneal endothelium were cultured in a corneal bioreactor for 7 days with 16 mmHg IOP and 5 μl/ml of medium flow. RNA was harvested, and gene expression was quantified. Cells that were used to reconstruct the TE corneal endothelia were also seeded on plastic to characterize their morphology by calculating their circularity index. For native endothelia, hydrodynamic forces increased gene expression of GJA1 (connexin 43), CDH2 (N-cadherin), TJP1 (ZO-1), ITGAV (integrin subunit αv), ITGB5 (integrin subunit β5) and CTNND1 (p120-ctn) by 1.68 ± 0.40, 1.10 ± 0.27, 3.80 ± 0.56, 1.82 ± 0.33, 1.32 ± 0.21 and 3.04 ± 0.63, respectively. For TE corneal endothelium, this fold change was 1.72 ± 0.31, 1.58 ± 0.41, 6.18 ± 1.03, 1.80 ± 0.71, 1.77 ± 0.55, 2.42 ± 0.71. Furthermore, gene transcription fold changes (hydrodynamic/control) increased linearly with TE corneal endothelium cells population morphology with r = 0.83 for TJP1 (ZO-1) and r = 0.58 for CTNND1 (p120-ctn). In fact, the more elongated the cells populations were, the greater hydrodynamic conditions increased the transcription of TJP1 (ZO-1) and CTNND1 (p120-ctn). These results suggest that hydrodynamic forces contribute to the maintenance of tight and adherens junctions of native corneal endothelial cells, as well as to the formation of tight and adherens junctions of corneal endothelial cells that are in the process of forming a functional endothelial barrier.

Bicarbonate activates glycolysis and lactate production in corneal endothelial cells by increased pHi

Recent studies have shown that lactate coupled water flux is the underlying mechanism of the corneal endothelial pump, which is highly dependent on the presence of bicarbonate. In this study we test the hypothesis that the increased intracellular pH (pHi) caused by bicarbonate stimulates glycolytic activity and the production of lactate by endothelial cells. Primary cultures of bovine corneal endothelial cells (BCEC) were incubated in bicarbonate-free (BF) ringer, a high [HEPES] ringer, and bicarbonate-rich (BR) ringer all at pH 7.5. Lactate production and glucose consumption were greatest in BR>HEPES >BF. Similarly, pHi was greatest in BR>HEPES>BF. Increasing pHi with NH4Cl also increased lactate production in BF or BR, indicating that the increased lactate production in BR is not due to HCO3- itself. Glucose transport capacity, as measured by 2-N-(7-Nitrobenz-2-oxa-1,3-diazol-4-yl)Amino-2-Deoxyglucose (2-NBDG) uptake was unaffected by the three incubation conditions. Using Laconic, a FRET sensor for lactate, we found that intracellular [lactate] increased immediately and transiently when cells were switched from BF to BR perfusion indicating increased lactate production with subsequent matching of efflux. Moreover, induction of acute lactate influx by perfusion pulses of 10 mM lactate increased intracellular [lactate] significantly faster in BF than in BR, consistent with higher lactate production and efflux in BR. In summary, our results indicate that glycolytic flux and lactate production increase in BR due to increased pHi, consistent with the well-known pH sensitivity of phosphofructokinase, the rate limiting enzyme in glycolysis.

A fine-tuned β-catenin regulation during proliferation of corneal endothelial cells revealed using proteomics analysis

Corneal endothelial (CE) dysfunction is the main indication for corneal transplantation, an invasive procedure with several limitations. Developing novel strategies to re-activate CE regenerative capacity is, therefore, of fundamental importance. This goal has proved to be challenging as corneal endothelial cells (CEnC) are blocked in the G0/G1 phase of the cell cycle in vivo and, albeit retaining proliferative capacity in vitro, this is further hindered by endothelial-to-mesenchymal transition. Herein we investigated the mechanisms regulating CEnC proliferation in vitro. Comparing the proteome of non-proliferating (in vivo-G0/G1) and proliferating (in vitro-G2/M) rabbit CEnC (rCEnC), 77 proteins, out of 3,328 identified, were differentially expressed in the two groups (p < 0.005). Literature and Gene Ontology analysis revealed β-catenin and transforming growth factor (TGF-β) pathways to be correlated with the identified proteins. Treatment of rCEnC with a β-catenin activator and inhibitor showed that β-catenin activation was necessary during rCEnC proliferation, but not sufficient for its induction. Furthermore, both pro-proliferative activity of basic fibroblast growth factor and anti-proliferative effects of TGF-β were regulated through β-catenin. Overall, these results provide novel insights into the molecular basis underlying the proliferation process that CEnC re-activate in vitro, consolidating the role of β-catenin and TGF-β.

Nanolaser in cataract surgery and its impact on corneal endotelium

PURPOSE

To compare safety and efficacy of new nanolaser photofragmentation technique with standard ultrasound phacoemulsification cataract surgery technique. Metods: A group of 20 patients - 40 eyes who underwent bilateral cataract surgery, one eye with ultrasound phacoemulsification (group I), n = 20 fellow eye with nanosecond laser framentation (group II ). Lens Opacities Classification System III was used to classify cataract stage. All 40 eyes had stage III cataract, Nucleus Opalescence was NO2 - NO3. Uncorrected visual acuity (UCVA), endothelial cells density (DEC), hexagonal cells rate, index of endothelial cells pleomorfism, and corneal thickness were evaluated prior to surgery and at day 7 follow up.

RESULTS

All 40 eyes had uneventful surgery,without complications. Preoperative UCVA in group I was 0,70±0,07 and 0,68 ± 0,10 in group II. At follow up check 7 days after surgery UCVA was 0,98 ± 0,05 in group 1 and 0,98 ± 0,04 in group II (p-NS). The mean DEC (cells/mm2) before surgery was 2508 ± 205,54 in group 1 and 2472 ± 287,85 in group II. After surgery density decreased to 2024,92±271,50 in group 1 and 2138,5 ± 390,85 in group II. Difference in endothelial cells decrease between groups showed no statistical significance. There was no statistical significance in differences of hexagonal cells rate and corneal thickness between both groups pre and postoperatively.

CONCLUSION

Nanolaser lens photofragmentation and ultrasound phacoemulsification can be considered equal regarding impact on endothelial cells.

Effect of SOX2 Repression on Corneal Endothelial Cells

Purpose: Human corneal endothelial cells (hCECs) pump out water from the stroma and maintain the clarity of the cornea. The sex-determining region Y-box 2 (SOX2) participates in differentiation during the development of the anterior segment of the eye and is found in the periphery of wounded corneas. This study was performed to investigate the effect of SOX2 repression on hCECs. Methods: Cultured hCECs were transfected by siRNA for SOX2. The wound healing rate and cell viability were measured. The cell proliferation-associated protein level was evaluated by Western blotting and RT-PCR. The energy production and mitochondrial function were measured, and cell shape and WNT signaling were assessed. Results: Upon transfecting the cultured cells with siRNA for SOX2, the SOX2 level was reduced by 80%. The wound healing rate and viability were also reduced. Additionally, CDK1, cyclin D1, SIRT1, and ATP5B levels were reduced, and CDKN2A and pAMPK levels were increased. Mitochondrial oxidative stress and mitochondrial viability decreased, and the cell shape became elongated. Furthermore, SMAD1, SNAI1, WNT3A, and β-catenin levels were increased. Conclusion: SOX2 repression disrupts the normal metabolism of hCECs through modulating WNT signaling and mitochondrial functions.

Effect of Down syndrome and keratoconus on corneal density and volume: a triple comparative study

Keratoconus (KCN) and Down syndrome affect the corneal density and volume. In this study included Down syndrome patients with and without KCN (24 Down-KCN and 204 Down-nonKCN eyes) and normal age- and gender-matched individuals (184 eyes). Studied parameters were the corneal density measured with Pentacam HR in 5 concentric zones and annuli (0-2 mm, 2-6 mm, 6-10 mm, 10-12 mm, and 0-12 mm) in 4 different depth layers (anterior 120 µm, posterior 60 µm, middle layer, and the full thickness of the cornea), and the 10 mm zone corneal volume. In Down-KCN, Down-nonKCN, and control groups, respectively, mean full thickness density in the 0-12 mm zone was 19.35 ± 2.92, 17.85 ± 2.55, and 15.78 ± 2.67 GSU, and mean corneal volume was 57.45 ± 4.37, 56.99 ± 3.46, and 61.43 ± 3.42mm3. All density readings were significantly different between the three studied groups (all P < 0.01) except full thickness density in 0-2 mm and 2-6 mm (P > 0.05) and corneal volume (P = 0.519) between Down-KCN and Down-nonKCN groups; these inter-group densitometry differences within the 6 mm zone were only in the middle layer, and not the anterior or posterior thickness layers (all P > 0.05). Corneal density increased with age and corneal thickness, but there was no significant relationship with gender. Overall, Down syndrome is associated with increased density and light scatter in all corneal layers up to the 12 mm diameter. In Down patients with KCN, the increased light scatter and density in the 6 mm zone is only in the middle thickness layer. Corneal volume is reduced in Down syndrome irrespective of the presence or absence of KCN.

Comparison of preloaded grafts for Descemet membrane endothelial keratoplasty (DMEK) in a novel preloaded transport cartridge compared to conventional precut grafts

To determine the safety and graft quality of eye bank precut and preloaded grafts for Descemet membrane endothelial keratoplasty (DMEK) after storage and shipping in a novel preloaded transport cartridge compared to precut grafts in a conventional viewing chamber. In this laboratory proof-of-concept study, 29 human donor corneas that were unsuitable for transplantation with a mean endothelial cell density of 1948 ± 260 cells/mm2 were prepared using liquid bubble technique for producing precut lamellar grafts. The grafts were either preloaded into novel transport cartridge (n = 16) or transferred into conventional Krolman viewing chamber (control, n = 13). Grafts were stored for 24 or 48 h in dextran-containing medium at room temperature and subjected to a shipping simulation. Endothelial cell loss (ECL) and morphology were determined at different steps. Endothelial cell viability staining was performed with calcein dye. Mean ECL in the preloaded transport cartridge was 0.7% ± 1.2% after 24 h and 3.4% ± 1.2% (p = 0.006) after 48 h storage and injection. In the control group the ECL was mean 1.6% ± 2.7% after 24 h compared to 3.7% ± 0.9% (p = 0.042) after 48 h. The slightly higher endothelial cell loss in the viewing chamber group after 48 h was not statistically significant compared to the preloaded transport cartridge (p = 0.8). Calcein staining was comparably low in all groups and correlated with the low ECL in both groups. DMEK grafts can be preloaded into a novel transport cartridge using a "no touch" technique, stored and shipped for up to 2 days in dextran-containing medium without significant ECL.

A non-canonical role for p27Kip1 in restricting proliferation of corneal endothelial cells during development

The cell cycle regulator p27^Kip1 is a critical factor controlling cell number in many lineages. While its anti-proliferative effects are well-established, the extent to which this is a result of its function as a cyclin-dependent kinase (CDK) inhibitor or through other known molecular interactions is not clear. To genetically dissect its role in the developing corneal endothelium, we examined mice harboring two loss-of-function alleles, a null allele (p27⁻) that abrogates all protein function and a knockin allele (p27^CK−) that targets only its interaction with cyclins and CDKs. Whole-animal mutants, in which all cells are either homozygous knockout or knockin, exhibit identical proliferative increases (~0.6-fold) compared with wild-type tissues. On the other hand, use of mosaic analysis with double markers (MADM) to produce infrequently-occurring clones of wild-type and mutant cells within the same tissue environment uncovers a roughly three- and six-fold expansion of individual p27^CK−/CK− and p27^−/− cells, respectively. Mosaicism also reveals distinct migration phenotypes, with p27^−/− cells being highly restricted to their site of production and p27^CK−/CK− cells more widely scattered within the endothelium. Using a density-based clustering algorithm to quantify dispersal of MADM-generated clones, a four-fold difference in aggregation is seen between the two types of mutant cells. Overall, our analysis reveals that, in developing mouse corneal endothelium, p27 regulates cell number by acting cell autonomously, both through its interactions with cyclins and CDKs and through a cyclin-CDK-independent mechanism(s). Combined with its parallel influence on cell motility, it constitutes a potent multi-functional effector mechanism with major impact on tissue organization.

In Vitro Expansion of Corneal Endothelial Cells for Transplantation

The corneal endothelium forms a leaky barrier between the corneal stroma and the aqueous humor of the anterior chamber. This cell monolayer maintains the corneal stroma in a state of relative dehydration, a process called deturgescence, which is required in order to obtain corneal stromal transparency. Endothelial dysfunctions lead to visual impairment that ultimately can only be treated surgically via the corneal transplantation of a functional endothelium. Shortages of corneas suitable for transplantation has motivated research toward new alternatives involving in vitro corneal endothelial cell (CEC) expansion.This chapter describes current methods that allow isolate and culture CECs. In brief, Descemet membrane is peeled out of the cornea and digested in order to obtain CECs. Cells are then seeded and cultured.

Treatment of corneal endothelial damage in a rabbit model with a bioengineered graft using human decellularized corneal lamina and cultured human corneal endothelium

Objective

We aimed to investigate the functionality of human decellularized stromal laminas seeded with cultured human corneal endothelial cells as a tissue engineered endothelial graft (TEEK) construct to perform endothelial keratoplasty in an animal model of corneal endothelial damage.

Methods

Engineered corneal endothelial grafts were constructed by seeding cultured human corneal endothelial cell (hCEC) suspensions onto decellularized human corneal stromal laminas with various coatings. The functionality and survival of these grafts with cultured hCECs was examined in a rabbit model of corneal endothelial damage after central descemetorhexis. Rabbits received laminas with and without hCECs (TEEK and control group, respectively).

Results

hCEC seeding over fibronectin-coated laminas provided an optimal and consistent endothelial cell count density and polygonal shape on the decellularized laminas, showing active pump fuction. Surgery was performed uneventfully as standard Descemet stripping automated endothelial keratoplasty (DSAEK). Corneal transparency gradually recovered in the TEEK group, whereas haze and edema persisted for up to 4 weeks in the controls. Histologic examination showed endothelial cells of human origin covering the posterior surface of the graft in the TEEK group.

Conclusions

Grafting of decellularized stroma carriers re-surfaced with human corneal endothelial cells ex vivo can be a readily translatable method to improve visual quality in corneal endothelial diseases.

Poly-ε-lysine based hydrogels as synthetic substrates for the expansion of corneal endothelial cells for transplantation

Dysfunction of the corneal endothelium (CE) resulting from progressive cell loss leads to corneal oedema and significant visual impairment. Current treatments rely upon donor allogeneic tissue to replace the damaged CE. A donor cornea shortage necessitates the development of biomaterials, enabling in vitro expansion of corneal endothelial cells (CECs). This study investigated the use of a synthetic peptide hydrogel using poly-ε-lysine (pεK), cross-linked with octanedioic-acid as a potential substrate for CECs expansion and CE grafts. PεK hydrogel properties were optimised to produce a substrate which was thin, transparent, porous and robust. A human corneal endothelial cell line (HCEC-12) attached and grew on pεK hydrogels as confluent monolayers after 7 days, whereas primary porcine CECs (pCECs) detached from the pεK hydrogel. Pre-adsorption of collagen I, collagen IV and fibronectin to the pεK hydrogel increased pCEC adhesion at 24 h and confluent monolayers formed at 7 days. Minimal cell adhesion was observed with pre-adsorbed laminin, chondroitin sulphate or commercial FNC coating mix (fibronectin, collagen and albumin). Functionalisation of the pεK hydrogel with synthetic cell binding peptide H-Gly-Gly-Arg-Gly-Asp-Gly-Gly-OH (RGD) or α2β1 integrin recognition sequence H-Asp-Gly-Glu-Ala-OH (DGEA) resulted in enhanced pCEC adhesion with the RGD peptide only. pCECs grown in culture at 5 weeks on RGD pεK hydrogels showed zonula occludins 1 staining for tight junctions and expression of sodium-potassium adenosine triphosphase, suggesting a functional CE. These results demonstrate the pεK hydrogel can be tailored through covalent binding of RGD to provide a surface for CEC attachment and growth. Thus, providing a synthetic substrate with a therapeutic application for the expansion of allogenic CECs and replacement of damaged CE.

A Human Corneal Equivalent Constructed from SV40-immortalised Corneal Cell Lines

Within the last decade, extensive research in the field of tissue and organ engineering has focused on the development of in vitro models of the cornea. The use of organotypic, three-dimensional corneal equivalents has several advantages over simple monolayer cultures. The aim of this study was to develop a corneal equivalent model composed of the same cell types as in the natural human tissue, but by using immortalised cell lines to ensure reproducibility and to minimise product variation. We report our success in the establishment of an SV40-immortalised human corneal keratocyte cell line (designated HCK). A collagen matrix, built up with these cells, displayed the morphological characteristics of the human stromal tissue and served as a biomatrix for the immortalised human corneal epithelial and endothelial cells. Histological cross-sections of the whole-cornea equivalents resemble human corneas in tissue structure. This organotypic in vitro model may serve as a research tool for the ophthalmic science community, as well as a model system for testing for eye irritancy and drug efficacy.

The presence of a feeder layer improves human corneal endothelial cell proliferation by altering the expression of the transcription factors Sp1 and NFI

Based on the use of tissue-cultured human corneal endothelial cells (HCECs), cell therapy is a very promising avenue in the treatment of corneal endothelial pathologies such as Fuchs' dystrophy, and post-surgical corneal edema. However, once in culture, HCECs rapidly lose their phenotypic and physiological characteristics, and are therefore unsuitable for the reconstruction of a functional endothelial monolayer. Expression of NFI, a transcription factor that can either function as an activator or a repressor of gene transcription, has never been examined in endothelial cells. The present study therefore aimed to determine the impact of a non-proliferating, lethally irradiated i3T3 feeder layer on the maintenance of HCEC's morphological characteristics, and both the expression and stability of Sp1 (a strong transcriptional activator) and NFI in such cells. The typical morphology of endothelial cells was best maintained when 8 × 103/cm2 HCECs were co-cultured in the presence of 2 × 104 cells/cm2 i3T3. HCECs were found to express both Sp1 and NFI in vitro. Also, the presence of i3T3 led to higher levels of Sp1 and NFI in HCECs, with a concomitant increase in their DNA binding levels (assessed by electrophoretic mobility shift assays (EMSA)). Specifically, i3T3 increased the expression of the NFIA, NFIB and NFIC isoforms, without a noticeable increase in their mRNAs (as revealed by gene profiling on microarray). Gene profiling analysis also identified a few feeder layer-dependent, differentially regulated genes whose protein products may contribute to improving the properties of HCECs in culture. Therefore, co-culturing HCECs with an i3T3 feeder layer clearly improves their morphological characteristics by maintaining stable levels of Sp1 and NFI in cell culture.

Donor, Recipient, and Operative Factors Associated with Graft Success in the Cornea Preservation Time Study

PURPOSE

To associate donor, recipient, and operative factors with graft success 3 years after Descemet stripping automated endothelial keratoplasty (DSAEK) in the Cornea Preservation Time Study (CPTS).

DESIGN

Cohort study within a multicenter, double-masked, randomized clinical trial.

PARTICIPANTS

One thousand ninety individuals (1330 study eyes) with a median age of 70 years undergoing DSAEK for Fuchs endothelial corneal dystrophy (94% of eyes) or pseudophakic or aphakic corneal edema (PACE; 6% of eyes).

METHODS

Eyes undergoing DSAEK were randomized to receive a donor cornea with preservation time (PT) of 0 to 7 days (n = 675) or 8 to 14 days (n = 655). Donor, recipient, and operative parameters were recorded prospectively. Graft failure was defined as regraft for any reason, a graft that failed to clear by 8 weeks after surgery, or an initially clear graft that became and remained cloudy for 90 days. Failure in the first 8 weeks was classified further as primary donor failure or early failure, in the absence or presence of operative complications, respectively. Proportional hazards and logistic regression models were used to estimate risk ratios (RR) and 99% confidence intervals (CIs) for graft failure.

MAIN OUTCOME MEASURES

Graft success at 3 years.

RESULTS

One thousand two hundred fifty-one of 1330 grafts (94%) remained clear at 3 years and were considered successful. After adjusting for PT, tissue from donors with diabetes (RR, 2.35; 99% CI, 1.03-5.33) and operative complications (RR, 4.21; 99% CI, 1.42-12.47) were associated with increased risk for primary or early failure. Preoperative diagnosis of PACE (RR, 3.59; 99% CI, 1.05-12.24) was associated with increased risk for late failure by 3 years after surgery compared with Fuchs dystrophy. Graft success showed little variation among other factors evaluated, including donor age (RR, 1.19 per decade; 99% CI, 0.91-1.56 per decade), preoperative donor endothelial cell density (RR, 1.10 per 500 cells; 99% CI, 0.74-1.63 per 500 cells), graft diameter (RR, 1.22 per 1 mm; 99% CI, 0.39-3.76 per 1 mm), and injector use for graft insertion (RR, 0.92; 99% CI, 0.40-2.10).

CONCLUSIONS

Descemet stripping automated endothelial keratoplasty success in the early and entire postoperative period is more likely when the donor did not have diabetes and was without operative complications and in the long-term postoperative period in recipients with Fuchs dystrophy compared with those with PACE. Mechanisms whereby diabetic donors and PACE recipients reduce the rate of graft success after DSAEK warrant further study.

Using continuous intraoperative optical coherence tomography to classify swirling lens fragments during cataract surgery and to predict their impact on corneal endothelial cell damage

PURPOSE

To quantify and classify swirling lens fragments during cataract surgery and record their impact on the corneal endothelium using continuous intraoperative optical coherence tomography (OCT).

SETTING

Vienna Institute for Ocular Surgery, Hanusch Hospital, Vienna, Austria.

DESIGN

Prospective case series.

METHODS

Patients scheduled for cataract surgery without other ophthalmologic comorbidities were included. During surgery, continuous OCT recordings were performed to measure and score swirling lens fragments that came into contact with the corneal endothelium. Endothelial cell density (ECD) was measured preoperatively and 1 month postoperatively. In addition, the central corneal thickness and aqueous flare were measured preoperatively and 1 hour, 1 day, and 1 month postoperatively.

RESULTS

Continuous intraoperative OCT video recordings showed 104 swirling lens fragments in 40 eyes that came into contact with the corneal endothelium. A mean of 2.6 lens fragments (range 0 to 6) that came into contact were observed per eye. Small fragments and fragments touching the center of the endothelium had a significantly greater effect on postoperative ECD than other fragment parameters. The predictive power of the fragment score on ECD was found to be moderate (r(2) = 0.6).

CONCLUSIONS

Small swirling lens fragments touching the center of the corneal endothelium had a significant influence on ECD. With the newly developed fragment score, it was possible to predict the operative endothelial cell loss.

FINANCIAL DISCLOSURE

None of the authors has a financial or proprietary interest in any material or method mentioned.

Corneal Endothelial Cell Segmentation by Classifier-Driven Merging of Oversegmented Images

Corneal endothelium images obtained by in vivo specular microscopy provide important information to assess the health status of the cornea. Estimation of clinical parameters, such as cell density, polymegethism, and pleomorphism, requires accurate cell segmentation. State-of-the-art techniques to automatically segment the endothelium are error-prone when applied to images with low contrast and/or large variation in cell size. Here, we propose an automatic method to segment the endothelium. Starting with an oversegmented image comprised of superpixels obtained from a stochastic watershed segmentation, the proposed method uses intensity and shape information of the superpixels to identify and merge those that constitute a cell, using support vector machines. We evaluated the automatic segmentation on a data set of in vivo specular microscopy images (Topcon SP-1P), obtaining 95.8% correctly merged cells and 2.0% undersegmented cells. We also evaluated the parameter estimation against the results of the vendor's built-in software, obtaining a statistically significant better precision in all parameters and a similar or better accuracy. The parameter estimation was also evaluated on three other data sets from different imaging modalities (confocal microscopy, phase-contrast microscopy, and fluorescence confocal microscopy) and tissue types (ex vivo corneal endothelium and retinal pigment epithelium). In comparison with the estimates of the data sets' authors, we achieved statistically significant better accuracy and precision in all parameters except pleomorphism, where a similar accuracy and precision were obtained.

A fully automated cell segmentation and morphometric parameter system for quantifying corneal endothelial cell morphology

BACKGROUND AND OBJECTIVE

Corneal endothelial cell abnormalities may be associated with a number of corneal and systemic diseases. Damage to the endothelial cells can significantly affect corneal transparency by altering hydration of the corneal stroma, which can lead to irreversible endothelial cell pathology requiring corneal transplantation. To date, quantitative analysis of endothelial cell abnormalities has been manually performed by ophthalmologists using time consuming and highly subjective semi-automatic tools, which require an operator interaction. We developed and applied a fully-automated and real-time system, termed the Corneal Endothelium Analysis System (CEAS) for the segmentation and computation of endothelial cells in images of the human cornea obtained by in vivo corneal confocal microscopy.

METHODS

First, a Fast Fourier Transform (FFT) Band-pass filter is applied to reduce noise and enhance the image quality to make the cells more visible. Secondly, endothelial cell boundaries are detected using watershed transformations and Voronoi tessellations to accurately quantify the morphological parameters of the human corneal endothelial cells. The performance of the automated segmentation system was tested against manually traced ground-truth images based on a database consisting of 40 corneal confocal endothelial cell images in terms of segmentation accuracy and obtained clinical features. In addition, the robustness and efficiency of the proposed CEAS system were compared with manually obtained cell densities using a separate database of 40 images from controls (n = 11), obese subjects (n = 16) and patients with diabetes (n = 13).

RESULTS

The Pearson correlation coefficient between automated and manual endothelial cell densities is 0.9 (p < 0.0001) and a Bland-Altman plot shows that 95% of the data are between the 2SD agreement lines.

CONCLUSIONS

We demonstrate the effectiveness and robustness of the CEAS system, and the possibility of utilizing it in a real world clinical setting to enable rapid diagnosis and for patient follow-up, with an execution time of only 6 seconds per image.

Comparison of manual & automated analysis methods for corneal endothelial cell density measurements by specular microscopy

PURPOSE

To determine the reliability of corneal endothelial cell density (ECD) obtained by automated specular microscopy versus that of validated manual methods and factors that predict such reliability.

METHODS

Sharp central images from 94 control and 106 glaucomatous eyes were captured with Konan specular microscope NSP-9900. All images were analyzed by trained graders using Konan CellChek Software, employing the fully- and semi-automated methods as well as Center Method. Images with low cell count (input cells number <100) and/or guttata were compared with the Center and Flex-Center Methods. ECDs were compared and absolute error was used to assess variation. The effect on ECD of age, cell count, cell size, and cell size variation was evaluated.

RESULTS

No significant difference was observed between the Center and Flex-Center Methods in corneas with guttata (p=0.48) or low ECD (p=0.11). No difference (p=0.32) was observed in ECD of normal controls <40 yrs old between the fully-automated method and manual Center Method. However, in older controls and glaucomatous eyes, ECD was overestimated by the fully-automated method (p=0.034) and semi-automated method (p=0.025) as compared to manual method.

CONCLUSION

Our findings show that automated analysis significantly overestimates ECD in the eyes with high polymegathism and/or large cell size, compared to the manual method. Therefore, we discourage reliance upon the fully-automated method alone to perform specular microscopy analysis, particularly if an accurate ECD value is imperative.

Characterizing human decellularized crystalline lens capsules as a scaffold for corneal endothelial tissue engineering

The idea of transplanting a sheet of laboratory-grown corneal endothelium dates back to 1978; however, the ideal scaffold is still lacking. We hypothesized that human crystalline lens capsules (LCs) could qualify as a scaffold and aimed to characterize the properties of this material for endothelial tissue engineering. LCs were isolated from donor eyes, stored at -80 °C, and decellularized with water and trypsin-EDTA. The decellularization was investigated by nuclear staining and counting and the capsule thickness was determined by optical coherence tomography and compared with Descemet's membrane (DM). Transparency was examined by spectrometry, and collagenase degradation was performed to evaluate its resistance to degradation. Cell-scaffold interaction was assessed by measuring focal adhesions surface area on LC and plastic. Finally, primary corneal endothelial cells were grown on LCs to validate the phenotype. Trypsin-EDTA decellularized most effectively, removing 99% of cells. The mean LC thickness was 35.76 ± 0.43 μm, whereas DM measured 25.93 ± 0.26 μm (p < .0001). Light transmission was 90% for both LC and DM. On a collagenase challenge, LC and amniotic membrane were digested after 13 hr, whereas DM was digested after 17 hr. The surface area of focal adhesions for cells grown on coated LCs was at least double that compared with other conditions, whereas tight junctions, ion pumps, and hexagonal morphology were well maintained when endothelial cells were cultured on LCs. In conclusion, LCs demonstrate excellent scaffolding properties for tissue engineering and sustain the cell phenotype and can be considered a suitable substrate for ocular tissue engineering or as a template for future scaffolds.

Air-Guided Manual Deep Lamellar Keratoplasty

Purpose

To evaluate the efficacy of a new modified technique of deep lamellar keratoplasty (DLK).

METHODS

Nine eyes of eight patients with keratoconus of moderate degree were included. All patients underwent DLK with manual dissection from a limbal side port after an air bubble injection in the anterior chamber. The patients underwent a complete ophthalmologic examinations months after the suture removal, evaluating best-corrected visual acuity, corneal thickness, endothelial cell count, and topographic astigmatism.

Results

One case (11.1%) was converted to penetrating keratoplasty because of micro-perforation. In the eight successful cases, 7 eyes (77.8%) achieved 20/30 or better visual acuity 6 months after suture removal. Mean postoperative pachymetry was 604.76μm (SD 46.76). Specular microscopy 6 months after suture removal revealed average endothelial cell count of 2273/mm2 (SD 229).

CONCLUSIONS

This modified DLK technique is a safe and effective procedure and could facilitate, after a short learning curve, this kind of surgery with a low risk of conversion to penetrating keratoplasty.

On the regional variability of averaged cell area estimates for the human corneal endothelium in relation to the extent of polymegethism

Purpose

To assess variability in the coefficient of variation (COV) in cell area estimates when using different numbers of cells for endothelial morphometry.

Methods

Using non-contact specular microscopy images of the corneal endothelium, 4 sets of 20 cases were selected that included 200 cells and had overall (global) COV values of less than 30 (group 1), 31–40 (group 2), 41–50 (group 3) and over 50% (group 4). Subjects could be normal, or had ophthalmic disease (such as diabetes), a history of rigid or soft contact lens wear or were assessed after cataract surgery. A step-wise analysis was undertaken, 20 cells at a time, of the variability in cell area estimates when using different numbers of cells for the calculations.

Results

Variability in the average cell area values was higher if only 20–60 cells were used in the calculations and then tended to decrease. The standard deviation values on these average cell area values and the calculated COV showed the same overall trends and were more than twice as large for endothelia with marked polymegethism. Using more than 100 cells/image in markedly polymegethous endothelia only increased the variability in the calculations.

Conclusions

These analyses indicate that substantial region variability in cell area values can be expected in polymegethous endothelia. The analysis further confirm that using only small numbers of cells (e.g. less than 50/image) in such cases is likely to yield far less reliable estimates of COV.

In vitro biomimetic platforms featuring a perfusion system and 3D spheroid culture promote the construction of tissue-engineered corneal endothelial layers

Corneal endothelial cells (CECs) are very important for the maintenance of corneal transparency. However, in vitro, CECs display limited proliferation and loss of phenotype via endothelial to mesenchymal transformation (EMT) and cellular senescence. In this study, we demonstrate that continuous supplementary nutrition using a perfusion culture bioreactor and three-dimensional (3D) spheroid culture can be used to improve CEC expansion in culture and to construct a tissue-engineered CEC layer. Compared with static culture, perfusion-derived CECs exhibited an increased proliferative ability as well as formed close cell-cell contact junctions and numerous surface microvilli. We also demonstrated that the CEC spheroid culture significantly down-regulated gene expression of the proliferation marker Ki67 and EMT-related markers Vimentin and α-SMA, whereas the gene expression level of the CEC marker ATP1A1 was significantly up-regulated. Furthermore, use of the perfusion system in conjunction with a spheroid culture on decellularized corneal scaffolds and collagen sheets promoted the generation of CEC monolayers as well as neo-synthesized ECM formation. This study also confirmed that a CEC spheroid culture on a curved collagen sheet with controlled physiological intraocular pressure could generate a CEC monolayer. Thus, our results show that the use of a perfusion system and 3D spheroid culture can promote CEC expansion and the construction of tissue-engineered corneal endothelial layers in vitro.

Endothelium-in versus endothelium-out for Descemet membrane endothelial keratoplasty graft preparation and implantation

PURPOSE

To evaluate the difference between endothelium-in and endothelium-out for Descemet membrane endothelial keratoplasty (DMEK) preparation and implantation using injection method.

METHODS

The study was a randomized, comparative, institutional, laboratory investigation. Eighteen human donor corneas were included. A total of 9.5 mm DMEK grafts were stripped and restored on the corneal base with a hinge and preserved in the deswelling medium. The grafts were detached from the hinge and either manually tri-folded with the endothelium on the inside, or allowed to spontaneously roll in phosphate-buffered saline (PBS) with endothelium outwards. The corneas were mounted on an artificial anterior chamber (AAC) and four incisions made using a 15° eye knife for the side ports and slit knife to create a 3.0 mm incision for delivery of the graft into the AAC. The grafts with endothelium-in (endo-in) were pulled into a cartridge, whereas those with endothelium-out (endo-out) were aspirated using a modified Jones tube. Both were delivered using an injection method. Central and peripheral endothelial cell density (pre- and post-delivery and after removal), time of preparation and unfolding were measured.

RESULTS

Endothelial cell loss postimplantation was 10.53% (±2.82) with endo-in (n = 9) compared to 7.56% (±14.74) with endo-out (n = 9) (p > 0.05). Preparation and unfolding time was 4.43 min (±3.43) and 0.96 min (±1.10) for endo-in compared to 1.68 min (±0.57) and 4.92 min (±4.21) for endo-out. A statistical significance between endo-in and endo-out for loading (p = 0.04) and unfolding (p = 0.023) time was observed.

CONCLUSIONS

Descemet membrane endothelial keratoplasty tissues can be tri-folded (endo-in) with no significantly less cell loss as compared to endo-out. Spontaneous unfolding of endo-in may reduce overall time and surgical manipulation.

[Corneal cell therapy-an overview]

In recent years, the cultivation and expansion of primary corneal cells has made significant progress. The transplantation of cultured limbal epithelial cells represents a successful and established treatment of the ocular surface. Cultivated corneal endothelial cells are undergoing a clinical trial in Japan. Stromal keratocytes can now be expanded in vitro. A wide range of stem cell sources is being tested in vitro and animal models for their possible application in corneal cell therapy. This article gives an overview of recent advancements and prevailing limitations for the use of different cell sources in the therapy of corneal disease.

[Density of the endotheliocytic layer of the cornea of the eyeball as a function of age]

This article presents the results of measuring the number of corneal endotheliocytes in a unit area of descemet membrane surface in 546 volunteers of different ages. The average values of the density of the corneal posterior epithelium for the age intervals 40-49, 50-59, 60-69, 70-79, 80 years and older are shown, a constant decrease in the number of endotheliocyte cells as the number of years lived increases.

Engineered Basement Membranes for Regenerating the Corneal Endothelium

Basement membranes are protein-rich extracellular matrices (ECM) that are essential for epithelial and endothelial tissue structure and function. Aging and disease cause changes in the physical properties and ECM composition of basement membranes, which has spurred research to develop methods to repair and/or regenerate these tissues. An area of critical clinical need is the cornea, where failure of the endothelium leads to stromal edema and vision loss. Here, an engineered basement membrane (EBM) is developed that consists of a dense layer of collagen IV and/or laminin ≈5-10 nm thick, created using surface-initiated assembly, conformally attached to a collagen I film. These EBMs are used to engineer a corneal endothelium (CE) that mimics the structure of Descemet's membrane with a thin stromal layer, toward use as a graft for lamellar keratoplasty. Results show that bovine and human CE cells form confluent monolayers on the EBM, express ZO-1 at the cell-cell borders, and achieve a density of ≈1600 cells mm-2 for 28 and 14 d, respectively. These results demonstrate that the technique is capable of fabricating EBMs with structural and compositional properties that mimic native basement membranes and that EBM may be a suitable carrier for engineering transplant quality CE grafts.

[Effect of a new ROCK inhibitor thiazovivin on the morphology and function of human corneal endothelial cells]

OBJECTIVE

To evaluate the effect of thiazovivin, a novel ROCK inhibitor, on the morphology and function of human corneal endothelial cells(HCECs).

METHODS

The primary HCECs were identified by light microscopy and immunofluorescence staining of neuron-specific enolase. To screen the optimal concentration and action time of thiazovivin for maintaining the morphology and function of primary HCECs, Na (+)/K (+)-ATPase and N-cadherin were chosen as indicators, and the morphology and function of HCECs in various concentrations(0 μmol/L, 2 μmol/L, 4 μmol/L, and 6 μmol/L)for different durations(24 h and 48 h)were examined by immunofluorescence experiments. The effect of thiazovivin on the expression of ROCK was investigated by immunofluorescence and Western blot.

RESULTS

The primary HCECs cultured were hexagonal, closely packed, homogeneously and obviously stained by neuron-specific enolase. The immunofluorescence staining of Na(+)/K(+)-ATPase showed that when the primary HCECs cultured with various concentrations of thiazovivin(0, 2, 4, 6 μmol/L)for 24 h, the fluorescence were obvious, and the average absorbance values(A)were 1.27±0.08, 3.72±0.17, 21.07±4.67, 3.69±0.34, respectively. And the immunofluorescence staining of N-cadherin revealed that when the primary HCECs treated with 4 μmol/L thiazovivin for 24 h, the cell boundary was clear and the structure of the cells was intact. While the treating time of thiazovivin(4 μmol/L)on HCECs extended to 48 h, the immunofluorescence staining of Na(+)/K(+)-ATPase and N-cadherin showed that compared to HCECs treated with thiazovivin(4 μmol/L)for 24 h, the fluorescence intensity did not change significantly, but the cells arranged slightly untidy. In addition, the immunofluorescence staining of ROCK was weakened and the expression of ROCK was reduced by thiazovivin. Thiazovivin was effective for protecting the morphology and function of HCECs. An optimal improvement in the morphology, connection and function of HCECs was found when the primary HCECs were cultured with 4 μmol/L thiazovivin for 24 h. Moreover, the expression of ROCK protein could be significantly inhibited by thiazovivin. (Chin J Ophthalmol, 2016, 52: 686-692).

Generation and Feasibility Assessment of a New Vehicle for Cell-Based Therapy for Treating Corneal Endothelial Dysfunction

The corneal endothelium maintains corneal transparency by its pump and barrier functions; consequently, its decompensation due to any pathological reason causes severe vision loss due to corneal haziness. Corneal transplantation is the only therapeutic choice for treating corneal endothelial dysfunction, but associated problems, such as a shortages of donor corneas, the difficulty of the surgical procedure, and graft failure, still need to be resolved. Regenerative medicine is attractive to researchers as a means of providing innovative therapies for corneal endothelial dysfunction, as it now does for other diseases. We previously demonstrated the successful regeneration of corneal endothelium in animal models by injecting cultured corneal endothelial cells (CECs) in combination with a Rho kinase (ROCK) inhibitor. The purpose of the present study was to optimize the vehicle for clinical use in cell-based therapy. Our screening of cell culture media revealed that RELAR medium promoted CEC adhesion. We then modified RELAR medium by removing hormones, growth factors, and potentially toxic materials to generate a cell therapy vehicle (CTV) composed of amino acid, salts, glucose, and vitamins. Injection of CECs in CTV enabled efficient engraftment and regeneration of the corneal endothelium in the rabbit corneal endothelial dysfunction model, with restoration of a transparent cornea. The CECs retained >85% viability after a 24 hour preservation as a cell suspension in CTV at 4°C and maintained their potency to regenerate the corneal endothelium in vivo. The vehicle developed here is clinically applicable for cell-based therapy aimed at treating the corneal endothelium. Our strategy involves the generation of vehicle from a culture medium appropriate for a given cell type by removing materials that are not favorable for clinical use.

Results of Deep Anterior Lamellar Keratoplasty for Advanced Keratoconus in Children Less Than 18 Years

PURPOSE

To evaluate the outcomes of deep anterior lamellar keratoplasty (DALK) in children with advanced keratoconus.

DESIGN

Retrospective noncomparative interventional case series.

METHODS

A retrospective analysis was conducted of 20 eyes of 16 patients who underwent deep anterior lamellar keratoplasty at a tertiary eye care center for advanced keratoconus. The main preoperative parameters measured were decimal uncorrected visual acuity (UCVA), decimal best-corrected visual acuity (BCVA), and average keratometry. The average keratometry was taken as an average of the flat and steep keratometric readings. The follow-up ranged from 24 to 105 months. The main outcome measures were UCVA, BCVA, steep and flat simulated keratometry, refraction, graft clarity, and complications.

RESULTS

At the final follow-up, 18 patients had clear grafts in the visual axis area. Mean decimal UCVA changed from 0.06 ± 0.08 to 0.24 ± 0.09. Mean decimal BCVA changed from 0.12 ± 0.19 to 0.45 ± 0.24. The average keratometry decreased from 64.15 diopter (D) to 45.7 D after surgery. The complications noted in the patients were graft rejection (1), shield ulcers (2), graft infection (2), and interface vascularization (4). They were managed accordingly and only 1 patient needed penetrating keratoplasty.

CONCLUSIONS

DALK is an effective therapeutic modality for the management of advanced keratoconus in children.

Concise Review: An Update on the Culture of Human Corneal Endothelial Cells for Transplantation

The cornea forms the front window of the eye, enabling the transmission of light to the retina through a crystalline lens. Many disorders of the cornea lead to partial or total blindness, and therefore corneal transplantation becomes mandatory. Recently, selective corneal layer (as opposed to full thickness) transplantation has become popular because this leads to earlier rehabilitation and visual outcomes. Corneal endothelial disorders are a common cause of corneal disease and transplantation. Corneal endothelial transplantation is successful but limited worldwide because of lower donor corneal supply. Alternatives to corneal tissue for endothelial transplantation therefore require immediate attention. The field of human corneal endothelial culture for transplantation is rapidly emerging as a possible viable option. This manuscript provides an update regarding these developments. Significance: The cornea is the front clear window of the eye. It needs to be kept transparent for normal vision. It is formed of various layers of which the posterior layer (the endothelium) is responsible for the transparency of the cornea because it allows the transport of ions and solutes to and from the other layers of the cornea. Corneal blindness that results from the corneal endothelial dysfunction can be treated using healthy donor tissues. There is a huge demand for human donor corneas but limited supply, and therefore there is a need to identify alternatives that would reduce this demand. Research is underway to understand the isolation techniques for corneal endothelial cells, culturing these cells in the laboratory, and finding possible options to transplant these cells in the patients. This review article is an update on the recent developments in this field.

[Analysis of the Effect of Non-phacoemulsification Cataract Operation on Corneal Endothelial Cell Nucleus Division]

PURPOSE

To investigate the effect of non-phacoemulsification cataract operation in two different patterns of nucleus delivery on the quantity and morphology of corneal endothelial cells and postoperative visual acuity.

METHODS

Forty patients diagnosed with cataract underwent cataract surgery and were assigned into the direct nuclear delivery and semi-nuclear delivery groups. Lens density was measured and divided into the hard and soft lenses according to Emery-little lens nucleus grading system. Non-phacoemulsification cataract operation was performed. At 3 d after surgery, the quantity and morphology of corneal endothelium were counted and observed under corneal endothelial microscope. During 3-month postoperative follow-up, the endothelial cell loss rate, morphological changes and visual acuity were compared among four groups.

RESULTS

Corneal endothelial cell loss rate in the direct delivery of hard nucleus group significantly differed from those in the other three groups before and 3 months after operation (P < 0.01), whereas no statistical significance was found among the direct delivery of soft nucleus, semi-delivery of hard nucleus and semi-delivery soft nucleus groups (all P > 0.05). Preoperative and postoperative 2-d visual acuity did not differ between the semi-delivery of hard nucleus and direct delivery of soft nucleus groups (P = 0.49), significantly differed from those in the semi-delivery of soft nucleus (P = 0.03) and direct delivery of hard nucleus groups (P = 0.14). Visual acuity at postoperative four months did not differ among four groups (P = 0.067).

CONCLUSION

During non-phacoemulsification cataract surgery, direct delivery of hard nucleus caused severe injury to corneal endothelium and semi-delivery of soft nucleus yielded mild corneal endothelial injury. Slight corneal endothelial injury exerted no apparent effect upon visual acuity and corneal endothelial morphology at three months after surgery.

Investigation of Overrun-Processed Porous Hyaluronic Acid Carriers in Corneal Endothelial Tissue Engineering

Hyaluronic acid (HA) is a linear polysaccharide naturally found in the eye and therefore is one of the most promising biomaterials for corneal endothelial regenerative medicine. This study reports, for the first time, the development of overrun-processed porous HA hydrogels for corneal endothelial cell (CEC) sheet transplantation and tissue engineering applications. The hydrogel carriers were characterized to examine their structures and functions. Evaluations of carbodiimide cross-linked air-dried and freeze-dried HA samples were conducted simultaneously for comparison. The results indicated that during the fabrication of freeze-dried HA discs, a technique of introducing gas bubbles in the aqueous biopolymer solutions can be used to enlarge pore structure and prevent dense surface skin formation. Among all the groups studied, the overrun-processed porous HA carriers show the greatest biological stability, the highest freezable water content and glucose permeability, and the minimized adverse effects on ionic pump function of rabbit CECs. After transfer and attachment of bioengineered CEC sheets to the overrun-processed HA hydrogel carriers, the therapeutic efficacy of cell/biopolymer constructs was tested using a rabbit model with corneal endothelial dysfunction. Clinical observations including slit-lamp biomicroscopy, specular microscopy, and corneal thickness measurements showed that the construct implants can regenerate corneal endothelium and restore corneal transparency at 4 weeks postoperatively. Our findings suggest that cell sheet transplantation using overrun-processed porous HA hydrogels offers a new way to reconstruct the posterior corneal surface and improve endothelial tissue function.

Influence of Pre-Freezing Temperature on the Corneal Endothelial Cytocompatibility and Cell Delivery Performance of Porous Hyaluronic Acid Hydrogel Carriers

The development of porous hyaluronic acid (HA) hydrogels for corneal endothelial tissue engineering is attractive because they can be used as functional cell delivery carriers to help in the reconstruction of damaged areas. The purpose of this study was to investigate the corneal endothelial cytocompatibility and cell delivery performance of porous HA hydrogel biomaterials fabricated at different pre-freezing temperatures. As compared to their counterparts prepared at −80 °C, the HA samples fabricated at higher pre-freezing temperature (i.e., 0 °C) exhibited a larger pore size and higher porosity, thereby leading to lower resistance to glucose permeation. Live/dead assays and gene expression analyses showed that the restricted porous structure of HA carriers decreases the viability and ionic pump function of cultured corneal endothelial cells (CECs). The results also indicated that the porous hydrogel biomaterials fabricated at high pre-freezing temperature seem to be more compatible with rabbit CECs. In an animal model of corneal endothelial dysfunction, the wounded rabbit corneas receiving bioengineered CEC sheets and restricted porous-structured HA carriers demonstrated poor tissue reconstruction. The therapeutic efficacy of cell sheet transplants can be improved by using carrier materials prepared at high pre-freezing temperature. Our findings suggest that the cryogenic operation temperature-mediated pore microstructure of HA carriers plays an important role in corneal endothelial cytocompatibility and cell delivery performance.

Comparison of corneal endothelial cell measurements by two non-contact specular microscopes

BACKGROUND

Measurement of corneal endothelial cell density is important both for clinical diagnosis as well as clinical studies. Since endothelial cell loss is considered irreversible in humans, even small changes in endothelial cell density are relevant. Therefore it is important to know whether different instruments for endothelial cell density measurements give the same results and can thus be used interchangeably. In this study we compare corneal endothelial cell density and morphometry measurements from two widely used non-contact specular microscopes, the Topcon SP3000P and Konan Noncon Robo SP8000.

METHODS

Endothelial cell measurements were performed with both the Topcon SP3000P and Konan Noncon Robo SP8000 on 34 eyes of 18 consecutive patients of our cornea clinics with poor image quality being the only exclusion criterion. Images were obtained using the auto-focussing method and manual cell selection. Endothelial cell density (ECD), hexagonal cell ratio (HEX) and coefficient of value (CV) of the endothelial cell layer were calculated by the instruments' built-in software.

RESULTS

ECD values calculated by the Konan were systematically higher than Topcon values: in 94 % of eyes Konan gave a higher value than Topcon, leading to a mean difference in ECD between the instruments of 187 cells/mm(2) (P < 0.001 in paired Wilcoxon test). HEX showed a broad range of values and differed greatly with only weak correlation between the two instruments. CV values for Konan mostly exceeded Topcon values, and only showed a weak correlation between the two instruments as well.

CONCLUSIONS

Values for ECD between the Konan and the Topcon do correlate well, but the ECDs calculated by the Konan are systematically higher than Topcon values. Both HEX and CV vary greatly and do not correlate sufficiently. Thus we recommend not to use the Konan and the Topcon instrument interchangeably.

Delivery of Molecules into Human Corneal Endothelial Cells by Carbon Nanoparticles Activated by Femtosecond Laser

Corneal endothelial cells (CECs) form a monolayer at the innermost face of the cornea and are the engine of corneal transparency. Nevertheless, they are a vulnerable population incapable of regeneration in humans, and their diseases are responsible for one third of corneal grafts performed worldwide. Donor corneas are stored in eye banks for security and quality controls, then delivered to surgeons. This period could allow specific interventions to modify the characteristics of CECs in order to increase their proliferative capacity, increase their resistance to apoptosis, or release immunosuppressive molecules. Delivery of molecules specifically into CECs during storage would therefore open up new therapeutic perspectives. For clinical applications, physical methods have a more favorable individual and general benefit/risk ratio than most biological vectors, but are often less efficient. The delivery of molecules into cells by carbon nanoparticles activated by femtosecond laser pulses is a promising recent technique developed on non-adherent cells. The nanoparticles are partly consummated by the reaction releasing CO and H₂ gas bubbles responsible for the shockwave at the origin of cell transient permeation. Our aim was to develop an experimental setting to deliver a small molecule (calcein) into the monolayer of adherent CECs. We confirmed that increased laser fluence and time exposure increased uptake efficiency while keeping cell mortality below 5%. We optimized the area covered by the laser beam by using a motorized stage allowing homogeneous scanning of the cell culture surface using a spiral path. Calcein uptake reached median efficiency of 54.5% (range 50.3–57.3) of CECs with low mortality (0.5%, range (0.55–1.0)). After sorting by flow cytometry, CECs having uptaken calcein remained viable and presented normal morphological characteristics. Delivery of molecules into CECs by carbon nanoparticles activated by femtosecond laser could prove useful for future cell or tissue therapy.

Keratin-chitosan membranes as scaffold for tissue engineering of human cornea

PURPOSE

To study the attachment and growth of human corneal cells on keratin-chitosan membranes. The end goal is to develop a bioengineered cornea based on this material.

METHODS

Keratin-chitosan membranes were prepared as previously described by Tanabe et al., 2002. Briefly, 7.15 mg/cm2 of keratin dialysate was mixed with 10 wt% chitosan solution and 20 wt% glycerol. The solution was cast into a silicone mold and dried at 50ºC for 36 hours. Eyes were attained from a local eye bank after penetrant-keratoplastic surgery. Human epithelial, stromal and endothelial cells were obtained of the limbal, stromal and endothelial regions. Cells were cultured on keratin-chitosan membranes, as well as on plastic dishes as controls. When cultured cells reached confluence, they were fixed, incubated with primary antibodies (E-cadherin, cytokeratin high molecular weight (CK), vimentin and Na+/K+ ATPase) and visualized by indirect immunocytochemistry.

RESULTS

Epithelial, stromal and endothelial cells were able to attach and grow on keratin-chitosan membranes. All the cells maintained their morphology and cellular markers, both in the membrane and on the culture plate. Epithelial cells stained positively for CK and E-cadherin. A positive vimentin stain was observed in all stromal cells, while endothelial cells were positive for vimentin and Na+/K+ ATPase, but negative for E-cadherin.

CONCLUSIONS

Keratin-chitosan membranes have been shown to be a good scaffold for culturing epithelial, stromal and endothelial corneal cells; therefore, future applications of keratin-chitosan membranes may be developed for reconstruction of the cornea.

Characterization of tissue-engineered posterior corneas using second- and third-harmonic generation microscopy

Three-dimensional tissues, such as the cornea, are now being engineered as substitutes for the rehabilitation of vision in patients with blinding corneal diseases. Engineering of tissues for translational purposes requires a non-invasive monitoring to control the quality of the resulting biomaterial. Unfortunately, most current methods still imply invasive steps, such as fixation and staining, to clearly observe the tissue-engineered cornea, a transparent tissue with weak natural contrast. Second- and third-harmonic generation imaging are well known to provide high-contrast, high spatial resolution images of such tissues, by taking advantage of the endogenous contrast agents of the tissue itself. In this article, we imaged tissue-engineered corneal substitutes using both harmonic microscopy and classic histopathology techniques. We demonstrate that second- and third-harmonic imaging can non-invasively provide important information regarding the quality and the integrity of these partial-thickness posterior corneal substitutes (observation of collagen network, fibroblasts and endothelial cells). These two nonlinear imaging modalities offer the new opportunity of monitoring the engineered corneas during the entire process of production.