Biobanking of Dehydrated Human Donor Corneal Stroma to Increase the Supply of Anterior Lamellar Grafts

Low-temperature vacuum evaporation as a novel dehydration process for the long-term preservation of transplantable human corneal tissue

Globally there is a shortage of available donor corneas with only 1 cornea available for every 70 needed. A large limitation to corneal transplant surgery is access to quality donor tissue due to inadequate eye donation services and infrastructure in many countries, compounded by the fact that there are few available long-term storage solutions for effectively preserving spare donor corneas collected in countries with a surplus. In this study, we describe a novel technology termed low-temperature vacuum evaporation (LTVE) that can effectively dry-preserve surplus donor corneal tissue, allowing it to be stored for approximately 5 years, shipped at room temperature, and stored on hospital shelves before rehydration prior to ophthalmic surgery. The dry-preserved corneas demonstrate equivalent biological characteristics to non-dried donor tissue, with the exception that epithelial and endothelial cells are removed and keratocytes are rendered non-viable and encapsulated within the preserved extracellular matrix. Structure and composition of the dried and rehydrated corneas remained identical to that of non-dried control corneas. Matrix-bound cytokines and growth factors were not affected by the drying and rehydration of the corneas. The ability to preserve human donor corneas using LTVE will have considerable impact on global corneal supply; utilisation of preserved corneas in lamellar keratoplasties, corneal perforations, ulcers, and tectonic support, will allow non-preserved donor tissue to be reserved for where it is truly required.

Current and emerging strategies for the manufacture, implantation, and clinical management of corneal tissue allografts

Approximately 40,000 Australians have received a donor corneal tissue transplant over the last 40 years, with the primary indications being keratoconus, Fuchs' endothelial dystrophy, bullous keratopathy, and failure of a prior corneal transplant. Although corneal cross-linking and rigid contact lenses have emerged as alternative strategies for the management of keratoconus, the demand for donor corneas is increasing in-line with the ageing population in Australia. Moreover, owing to the lack of tissue banking resources in less-developed countries, the global demand for donor corneas exceeds supply by 70-fold. These supply issues, combined with evolving tissue banking and surgical techniques, have led to the emergence of new strategies for the storage, processing and implantation of corneal cells and tissues. Organ culture techniques have been developed that support the storage of donor corneas for up to 30 days, facilitating improvements in tissue supply and surgery scheduling. Bespoke surgical methods have been developed that are tailored to the requirements of specific conditions, allowing reductions in both the volume of tissue required to be transplanted and the size of the necessary surgical incision. Further efficiencies and improvements in patient care may be achieved via exploitation of cell culture technologies as exemplified through use of cultured corneal epithelial cells for the treatment of limbal stem cell deficiency. Promising progress has also been made in developing a cultured corneal endothelial cell therapy for patients with corneal endothelial dysfunction. These evolving strategies are discussed with respect to their potential impact on the clinical presentation and management of patients who have received an implant of donor corneal tissue or cells.

Integrated environmental and health economic assessments of novel xeno-keratografts addressing a growing public health crisis

Tissue scarcity poses global challenges for corneal transplantation and public health. Xeno-keratoplasty using animal-derived tissues offers a potential solution, but its environmental and economic implications remain unclear. This study evaluated two xeno-keratoplasty procedures at a single institution: (1) native corneas (Option 1) and (2) tissue-engineered corneal scaffolds derived from slaughterhouse waste (Option 2). Life cycle assessment (LCA) quantified environmental impacts across 18 midpoint indicators, while cost-effectiveness analysis (CEA) incorporated cost and environmental impact using two approaches. Option 1 exhibited significantly lower environmental impact than Option 2 across most indicators, primarily due to the energy and equipment demands of cell culture in Option 2. Both CEA approaches (carbon offset pricing and utility decrement) demonstrated cost-effectiveness dominance for Option 1. Xeno-keratoplasty using native corneas (Option 1) appears more environmentally and economically favorable than tissue-engineered scaffolds (Option 2) in the current analysis. Future studies could explore diverse xeno-keratoplasty techniques for optimizing sustainability.

Hydroxyproline Concentration and Associated Factors of Preserved Small Incision Lenticule Extraction-Derived Corneal Stromal Lenticules

PURPOSE

To evaluate changes of hydroxyproline concentration and its influencing factors of small incision lenticule extraction (SMILE)-derived corneal stromal lenticules with different preservation methods.

METHODS

A total of 390 corneal stromal lenticules of 195 patients were derived from SMILE surgeries. Thirty of the lenticules were classified as the fresh (control) group, and the rest were randomly and evenly divided and stored in anhydrous glycerol, silicone oil, Optisol, and cryopreservation for 1 day, 1 week, or 1 month. A hydroxyproline assay kit (ab222941, Abcam) was used to measure the hydroxyproline concentration in each preservation method. Concentrations of MMP-2, TIMP-2, TNFα, TGFβ2, and reactive oxygen species were also evaluated.

RESULTS

In the anhydrous glycerol group, the concentration of hydroxyproline decreased within 1 week (fresh: 1 dΔ = 0.229, P < 0.001*; 1 d - 1 wΔ = 0.055, P < 0.001*) while that in the silicone oil group remained stable in 1 week (1 d - 1 wΔ = -0.005, P = 0.929) and decreased significantly in 1 m (1 m - 1 wΔ = -0.041, P = 0.003*). The sequence of hydroxyproline concentration in the Optisol group was 1 m > 1 day > 1 week. Hydroxyproline concentration in the cryopreservation group decreased within 1 m. Hydroxyproline concentration was highest in the Optisol group and lowest in the anhydrous glycerol group under the same preservation time. Hydroxyproline concentration was negatively correlated with MMP-2 (r = -0.16, P = 0.421) and TIMP-2 (r = -0.56, P = 0.002*) while MMP-2 and TNFα (r = 0.17, P = 0.242), TIMP-2 and TGFβ2 (r = 0.21, P = 0.207), and TNFα and reactive oxygen species (r = 0.52, P = 0.007*) were positively correlated.

CONCLUSIONS

More collagen was retained in SMILE lenticules preserved in Optisol under the same preservation time. The mechanism of the changes of collagen in preserved SMILE-derived lenticules and oxidative stress requires additional investigation.

Banking of post-SMILE stromal lenticules for additive keratoplasty: A new challenge for eye banks?

PURPOSE

ReLEx (Refractive Lenticule Extraction) Small Incision Lenticule Extraction (SMILE), the second generation of ReLEx Femtosecond Lenticule Extraction (FLEx), is a minimally invasive, flapless procedure designed to treat refractive errors such as myopia, hyperopia, presbyopia, and astigmatism. This review aims to provide a comprehensive overview of the methods for preserving SMILE-derived lenticules and discusses their potential future applications.

METHODS

A narrative literature review was conducted using PubMed, Scopus, and Web of Science databases, focusing on articles published up to January 2024 and available in English. The authors also evaluated the reference lists of the collected papers to identify any additional relevant research.

RESULTS

No standardized protocols currently exist for the storage or clinical application of SMILE-derived lenticules. However, these lenticules present a promising resource for therapeutic uses, particularly in addressing the shortage of donor corneal tissues. Their potential applications include inlay and overlay additive keratoplasty, as well as other ocular surface applications. Further research is needed to establish reliable protocols for their preservation and clinical use.

CONCLUSION

SMILE-derived lenticules offer significant potential as an alternative to donor corneal tissues. Standardizing their storage and application methods could enhance their use in clinical settings.

Second harmonic generation microscopy of electromechanical reshaping on corneal collagen

Refractive errors remain a global health concern, as a large proportion of the world's population is myopic. Current ablative approaches are costly, not without risks, and not all patients are candidates for these procedures. Electromechanical reshaping (EMR) has been explored as a viable cost-effective modality to directly shape tissues, including cartilage. In this study, stromal collagen structure and fibril orientation was examined before and after EMR with second-harmonic generation microscopy (SHG), a nonlinear multiphoton imaging method that has previously been used to study native corneal collagen with high spatial resolution. EMR, using a milled metal contact lens and potentiostat, was performed on the corneas of five extracted rabbit globes. SHG was performed using a confocal microscopy system and all images underwent collagen fibril orientation analysis. The collagen SHG signal in controls is uniform and is similarly seen in samples treated with pulsed potential, while continuous EMR specimens have reduced, nonhomogeneous signal. Collagen fibril orientation in native tissue demonstrates a broad distribution with suggestion of another peak evolving, while with EMR treated eyes a bimodal characteristic becomes readily evident. Pulsed EMR may be a means to correct refractive errors, as when comparing its SHG signal to negative control, preservation of collagen structures with little to no damage is observed. From collagen fiber orientation analysis, it can be inferred that simple DC application alters the structure of collagen. Future studies will involve histological assessment of these layers and multi-modal imaging analysis of dosimetry.

Deep Anterior Lamellar Keratoplasty Using Dehydrated versus Standard Organ Culture-Stored Donor Corneas: Prospective Randomized Trial

PURPOSE

To compare the outcomes of deep anterior lamellar keratoplasty (DALK) using dehydrated versus standard organ culture-stored donor corneas for eyes with keratoconus.

DESIGN

Prospective, randomized, single-center trial conducted in Italy.

PARTICIPANTS

Adult patients (age ≥ 18 years) with keratoconus scheduled for elective DALK.

METHODS

Patients undergoing successful type 1 bubble pneumatic dissection using a standard DALK technique were randomized during surgery to receive either dehydrated (n = 30) or standard organ culture-stored (n = 30) donor corneas.

MAIN OUTCOME MEASURES

The primary study outcome was best spectacle-corrected visual acuity (BSCVA) 12 months after surgery. Secondary outcomes were refractive astigmatism (RA), endothelial cell density (ECD), and complication rates.

RESULTS

Postoperative BSCVA did not significantly differ between groups at both time points: mean difference at 6 months was 0.030 logarithm of the minimum angle of resolution (logMAR; 95% confidence interval [CI], -0.53 to 0.10 logMAR; P = 0.471) and at 12 months was -0.013 logMAR (95% CI, -0.10 to 0.08 logMAR; P = 0.764). No significant differences between groups were observed in terms of postoperative RA and ECD at all time points. In the first 3 days after DALK, an epithelial defect was present in 10 patients (33%) in the organ culture cornea group and in 29 patients (97%) in the dehydrated cornea group. Complete re-epithelialization was achieved by day 7 in all patients (100%) in both groups.

CONCLUSIONS

The study provides evidence that the use of dehydrated corneas is noninferior to the use of standard organ culture donor corneas for DALK. Corneal tissue dehydration represents a viable solution that can allow long-term cornea preservation and avoid wastage of unused corneas.

FINANCIAL DISCLOSURE(S)

The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Dry Eye Para-Inflammation Treatment: Evaluation of a Novel Tear Substitute Containing Hyaluronic Acid and Low-Dose Hydrocortisone

Purpose: The purpose of this study was to check the efficacy and safety of a novel tear substitute containing hyaluronic acid and low-dose hydrocortisone in the treatment of moderate dry eye disease. Methods: In this prospective randomized study, 38 patients with moderate dry eye disease were divided into two treatment groups: Group 1 received one drop of 0.2% sodium hyaluronate and 0.001% hydrocortisone four times daily for 3 months, while Group 2 received 0.15% sodium hyaluronate and 3% trehalose at the same dosage. OSDI and SANDE questionnaires, Non-Invasive Break-Up time (NIBUT), Tear Meniscus Height (TMH), meibography, Lipid Layer Thickness (LLT), Tear Break-Up Time (TBUT), Corneal Staining Score (CFS), and Intraocular Pressure (IOP) were evaluated at baseline and after 1, 2, and 3 months of treatment. Results: During the treatment period, Group 1 showed statistically significant improvement in OSDI score (p = 0.002), SANDE score (p = 0.01), NIBUT (p < 0.0001), LLT (p < 0.0001), TBUT (p = 0.01), and CFS (p = 0.02). In Group 2, significant improvement was observed only in the TBUT score (p < 0.05). Comparison of the two groups showed that NIBUT and LLT were significantly different at the end of treatment (p = 0.001 for both comparisons), with more favorable results for sodium hyaluronate and hydrocortisone than for sodium hyaluronate and trehalose. No significant variations in intraocular pressure were observed in either group during the treatment period (p > 0.05). Conclusions: The study confirms that a 3-months treatment with hyaluronic acid 0.2% in combination with low-dose hydrocortisone 0.001% improves the signs and symptoms of moderate DED and that a low-dosage 0.001% hydrocortisone can be helpful in preventing the progression to chronic stages of DED.

Allogenic Lenticular Implantation for Correction of Refractive Error and Ectasia: Narrative Review

INTRODUCTION

Intrastromal lenticule implantation is a promising treatment option for corneal pathologies, from refractive error to ectasia. In this narrative review, we intend to feature up-to-date literature supporting the use of lenticular tissue, a compelling method that can be customized for a variety of applications, providing an additional source of donor tissue for treating corneal diseases.

METHODS

We searched databases PubMed, Mendeley, and Scopus last accessed 10 May 2023, for literature on stromal lenticules and narrowed based on relevance. Review articles, animal studies, ex vivo studies, and book chapters were excluded, while assessable and relevant articles published in English were included.

RESULTS

Storage methods from using fresh lenticules to dehydration have proven successful, with cryopreservation maintaining structure and cellular viability for up to 10 years. Successful use of lenticules for treatment of numerous pathologies including corneal ectasias, hyperopia, and presbyopia with additional insight into the treatment of corneal ulcers and perforations are highlighted in this narrative review.

CONCLUSION

Lenticular implantation is an innovative and advantageous treatment for various ocular pathologies, offering increased bioavailability, flexibility, and customization for patients. They can treat previously untreatable diseases and serve as a replacement for synthetic implants, with promising outcomes worldwide. Lenticular implantation has the potential to become a leading approach in ophthalmologic surgery. Further studies should aim to provide evidentiary support for a standardization of lenticule banking.

TGF-β2 Induces Epithelial-Mesenchymal Transitions in 2D Planer and 3D Spheroids of the Human Corneal Stroma Fibroblasts in Different Manners

To examine the epithelial-mesenchymal transition (EMT) that is induced on the human corneal stroma, two- and three-dimensional (2D and 3D) cultures of human corneal stroma fibroblasts (HCSFs) were used. In this study, HCSF 2D monolayers and 3D spheroids were characterized by (1) scanning electron microscopy (SEM), (2) trans-endothelial electrical resistance (TEER) measurements and fluorescein isothiocyanate (FITC)-dextran permeability, (3) cellular metabolic measurements, (4) the physical properties of 3D HCSF spheroids, and (5) the extracellular matrix (ECM) molecule gene expressions, including collagen (COL) 1, 4 and 6, and fibronectin (FN), a tissue inhibitor of metalloproteinase (TIMP) 1-4, matrix metalloproteinase (MMP) 2, 3, 9 and 14, and several endoplasmic reticulum (ER) stress-related factors. In the 2D HCSFs, TGF-β2 concentration-dependently generated (1) a considerable increase in ECM deposits revealed by SEM, (2) an increase in TEER values and a decrease in FITC-dextran permeability, (3) increases in both mitochondrial and glycolytic functions, and a substantial upregulation of COL1, COL4, FN, αSMA, TIMP1, TIMP, and most ER stress-related genes and the downregulation of COL6 and MMP3. In the case of 3D spheroids, TGF-β2 induced the downsizing and stiffening of 3D spheroids and the upregulation of COL6, MMP14, and most ER stress-related genes. These findings suggest that TGF-β2 significantly induced a number of EMT-associated biological events including planar proliferation, cellular metabolic functions, and the production of ECM molecules in the 2D cultured HCSF cells, but these effects were significantly less pronounced in the case of 3D HCSF spheroids.

Update of Research Progress on Small Incision Lenticule Extraction (SMILE) Lenticule Reuse

The SMILE lenticule is a complete corneal stroma that is removed from SMILE surgery. Since the increasing number of SMILE surgeries, a large number of SMILE lenticules have been produced, so the reuse and preservation of the stromal lens has become a research hotspot. Due to the rapid development of the preservation and clinical reuse of SMILE lenticules, there have been many related studies in recent years, so we updated it on this basis. We searched PubMed, Web of Science, Embase, Elsevier Science, CNKI, WANFANG Data and other databases for all articles published on the preservation and clinical reuse of SMILE lenticules, screened useful articles, selected relevant articles published in the last five years as the main body for summary, and then reached a conclusion. The existing preservation methods of SMILE lenticule include Moist chamber storage at low temperature, cryopreservation technique dehydrating agent and corneal storage medium, which have their own advantages and disadvantages. Presently, smile lenticules can be used for the treatment of corneal ulcers and perforations, corneal tissue defects, hyperopia, presbyopia and keratectasia, which have been proven to be relatively effective and safe. More research on smile lenticule reuse needs to be carried out to confirm its long-term efficacy.

Cytoprotective Effects of Human Platelet Lysate during the Xeno-Free Culture of Human Donor Corneas

We evaluated the suitability of 2% human platelet lysate medium (2%HPL) as a replacement for 2% fetal bovine serum medium (2%FBS) for the xeno-free organ culture of human donor corneas. A total of 32 corneas from 16 human donors were cultured in 2%FBS for 3 days (TP1), then evaluated using phase contrast microscopy (endothelial cell density (ECD) and cell morphology). Following an additional 25-day culture period (TP2) in either 2%FBS or 2%HPL, the pairs were again compared using microscopy; then stroma and Descemet membrane/endothelium (DmE) were processed for next generation sequencing (NGS). At TP2 the ECD was higher in the 2%HPL group (2179 ± 288 cells/mm²) compared to 2%FBS (2113 ± 331 cells/mm²; p = 0.03), and endothelial cell loss was lower (ECL HPL = -0.7% vs. FBS = -3.8%; p = 0.01). There were no significant differences in cell morphology between TP1 and 2, or between 2%HPL and 2%FBS. NGS showed the differential expression of 1644 genes in endothelial cells and 217 genes in stromal cells. It was found that 2%HPL led to the upregulation of cytoprotective, anti-inflammatory and anti-fibrotic genes (HMOX1, SERPINE1, ANGPTL4, LEFTY2, GADD45B, PLIN2, PTX3, GFRA1/2), and the downregulation of pro-inflammatory/apoptotic genes (e.g., CXCL14, SIK1B, PLK5, PPP2R3B, FABP5, MAL, GATA3). 2%HPL is a suitable xeno-free substitution for 2%FBS in human cornea organ culture, inducing less ECL and producing potentially beneficial alterations in gene expression.

Tips, Tricks, and Guides in Descemet Membrane Endothelial Keratoplasty Learning Curve

Lamellar keratoplasty is fast becoming the most popular form of corneal transplantation. The adoption of Descemet membrane endothelial keratoplasty (DMEK) in the management of Fuchs endothelial dystrophy and pseudophakic bullous keratopathy is partly responsible for this shift in the paradigm of management of corneal pathology. The learning curve of DMEK, however, has been proven to be much steeper than previous endothelial keratoplasty procedures. To ease the procedure, experts have proposed multiple innovative techniques from tissue preparation to graft unfolding to aid the more novice surgeon. Here, we collate and share tips and tricks from our collective experiences to support the learning curve and outcomes in DMEK for both the novice and more experienced corneal transplant surgeons.

Cornea donation process and tissue quality for transplantation

Introduction

The quality of the corneal tissue can be influenced by several factors inherent to the recipient, donor, and to the donation and transplantation process. The donated corneal tissue can be classified by its quality as excellent, good, regular, bad, or unacceptable for transplantation, evaluating it in a slit lamp.

Objective

To analyze the relationship between the clinical and sociodemographic variables of the donors and the donation process and the classification of the quality of the corneal tissue collected for transplantation.

Methods

This is an epidemiologic study, retrospective cohort type, which addressed the process of cornea donation by the Human Eye Tissue Bank in a reference service in Northeast Brazil. The sample consisted of corneas processed by the Human Eye Tissue Bank of Rio Grande do Norte (n = 419). For descriptive and inferential analysis, the study used the Statistical Package for the Social Sciences (SPSS) software, version 25.0, and considered a significance level of 0.05. Logistic regression analysis was used for the adjustment of the final model.

Results

It was verified that the epidemiological profile showed a prevalence of individuals with a mean age of 42.54 years old, male (73.99%), and living in the metropolitan region of the state capital (75.66%). When analyzing the relationship between the clinical and sociodemographic variables of the donors, it was identified that those aged 45 years old or less had better quality corneas (excellent and good), while the chronological variables were predictive factors for corneas of regular and bad qualities.

Conclusion

The identification of the factors inherent to the donation process and predictors of corneal tissue quality contribute to minimizing the risk of transplantation and to a better ocular prognosis.

Optical transmittance and ultrastructure of SMILE-derived lenticules subjected to three different preservative methods

PURPOSE

To investigate the optical transmittance and ultrastructure of small incision lenticule extraction (SMILE)-derived lenticules preserved via three different methods.

METHODS

A total of 90 lenticules obtained from myopic patients undergoing SMILE surgery were divided into control and experimental groups. Fresh lenticules served as the control. The preserved lenticules of the experimental group were randomly divided into three subgroups according to different storage conditions: anhydrous glycerol, silicone oil and allochroic silica gel groups. Optical transmittance was evaluated, histological changes were analysed by haematoxylin eosin (HE) staining, and collagen fibril densities and necrotic response were assessed via transmission electron microscopy (TEM) at 48 h, 14 days and 4 weeks.

RESULTS

After storage for 4 weeks, the mean percentage transmittance values in glycerol and silicone oil groups significantly decreased (P = 0.034 and P = 0.042, respectively), but the lenticules preserved in silica gel remained unchanged when compared with the control lenticules. In all the groups, HE staining results showed a regular arrangement of collagen fibers with a few keratocytes and several cavitation bubbles. TEM revealed that the fibril densities in the glycerol group (273.70 ± 31.42/μm²) after 4 weeks were significant less than those in the other two groups (silicone oil, 335.20 ± 33.09/μm²; silica gel, 371.80 ± 37.60/μm²) and control group (340 ± 33.61/μm²) (all P < 0.001). In each group, a few necrotic and apoptotic keratocytes were observed.

CONCLUSIONS

All the three agents, namely glycerol, silicone oil and silica gel, could be used for lenticule preservation. Silica gel facilitates better maintenance of optical transmittance than the other two agents.

Banking of corneal stromal lenticules: a risk-analysis assessment with the EuroGTP II interactive tool

We evaluated the feasibility and performed a risk-benefit analysis of the storage and widespread distribution of stromal lenticules for clinical application using a new systematic tool (European Good Tissue and cells Practices II-EuroGTP II tool), specifically designed for assessing the risk, safety and efficacy of substances of human origin. Three types of potential tissue preparations for human stromal lenticules were evaluated: cryopreserved, dehydrated and decellularized. The tool helps to identify an overall risk score (0-2: negligible; 2-6: low; 6-22: moderate; > 22: high) and suggests risk reduction strategies. For all the three types of products, we found the level of risk to be as "moderate". A process validation, pre-clinical in vitro and in vivo evaluations and a clinical study limited to a restricted number of patients should therefore be performed in order to mitigate the risks. Our study allowed to establish critical points and steps necessary to implement a new process for safe stromal lenticule preparation by the eye banks to be used in additive keratoplasty. Moreover, it shows that the EuroGTP II tool is useful to assess and identify risk reduction strategies for introduction of new Tissue and Cellular Therapies and Products into the clinical practice.