Utility of a Model to Predict Endothelial Cell Density of Donor Corneas to Determine Suitability for Transplantation.

Purpose: In Germany, approximately one-third of the harvested donor corneas are not suitable for transplantation, mostly due to insufficient endothelial cell density (ECD). The ECD can only be reliably determined after harvesting and processing of the cornea. Our group has previously developed a predictive model for corneal ECD: \( {Predicted\, ECD} = 2919-6^{\ast}\;{age}\; [{years}]-189\; [{if\, male}]\\ -7^{\ast}\;{death-to-explantation\, interval\,} [{hours}]\\ - 378\; [{if\, pseudophakic}] \;{cells/mm}^2 \). Methods: A total of 2.999 consecutive donor corneas harvested between 2017 and 2021 from the Eye Bank of Rhineland-Palatinate in Mainz, Germany, were included. An actual ECD of >2000 cells/mm2 was defined as the cutoff value. To evaluate the clinical utility of the prognostic model as a screening instrument for transplant eligibility in an independent cohort, we performed a decision curve analysis. Results: The median predicted ECD was 2061 cells/mm2 (interquartile range [IQR] = 1834 to 2221), whereas the median actual ECD was 2377 cells/mm2 (IQR = 1907 to 2624). There was a positive correlation between predicted and actual ECD (correlation coefficient = 0.411; P < 0.01). Our predictive model for ECD is a strong predictor for an actual ECD greater than 2000 (odds ratio = 1.374, 95% confidence interval [CI]) per 100 cells; P < 0.001, area under the curve [AUC] of 0.73). Decision curve analysis showed that the predictive model yielded a positive net benefit in clinical settings. Conclusions: Decision curve analysis demonstrated a positive net benefit of the ECD predictive model in clinical settings with limited eye bank resources. Translational Relevance: In possible scenarios where a choice between corneal grafts is required, or in countries with limited eye bank infrastructure and staff, the initial estimate of ECD from the formula may be beneficial.

Prevalence of Herpes Simplex and Varicella-Zoster Virus DNA in Corneal Grafts Is Higher than Expected.

PURPOSE: (1) To determine the prevalence of herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), varicella-zoster virus (VZV), and cytomegalovirus (CMV) DNA in donor corneas; (2) To evaluate the clinical outcome of the grafts with viral DNA and to compare donors with and without viral DNA. METHODS: We analyzed data from all donors and recipients who underwent penetrating keratoplasty (PK) or Descemet membrane endothelial keratoplasty (DMEK) between September 2022 and March 2023. Donor corneoscleral rims and excised recipients' corneal buttons were tested for the presence of HSV-1, HSV-2, VZV, and CMV DNA by polymerase chain reaction (PCR). The results were known 2-3 days after the surgery. We closely followed up on patients whose grafts tested positive for viral DNA. We compared the medical histories of donors with and without viral DNA. RESULTS: We included 85 corneas from 67 donors. Seven (8.2%) donor corneas tested positive for HSV-1 (n = 3) or VZV (n = 4) DNA. We did not detect any HSV-2 or CMV DNA. In the postoperative follow-up of patients with positive PCR, a graft failure was observed in one and infections in two eyes. Re-operation was necessary in three of these cases (42.9%). Patients without herpes DNA in the donor cornea needed reoperation in 7.7% of the cases. Cultural duration, the cause of the donor's death, and the death-to-explantation interval did not differ significantly between donors with and without viral DNA. Additionally, 3 of the 7 (42.9%) donors with positive PCR were in a septic status at the time of death, compared to 21 of the 78 (26.9%) donors with negative PCR (p = 0.52). CONCLUSIONS: The prevalence of herpes DNA in the donor corneas was 8.2% and thus higher than previously reported. We did not notice any evidence for a donor-to-host transmission, but a higher rate of postoperative complications in recipients of the grafts with viral DNA. The donors with and without herpetic DNA did not differ significantly regarding systemic diagnoses or cultural conditions, but sepsis was more frequent in the group with viral DNA.

Expression and subcellular localization of USH1C/harmonin in human retina provides insights into pathomechanisms and therapy.

Usher syndrome (USH) is the most common form of hereditary deaf-blindness in humans. USH is a complex genetic disorder, assigned to three clinical subtypes differing in onset, course and severity, with USH1 being the most severe. Rodent USH1 models do not reflect the ocular phenotype observed in human patients to date; hence, little is known about the pathophysiology of USH1 in the human eye. One of the USH1 genes, USH1C, exhibits extensive alternative splicing and encodes numerous harmonin protein isoforms that function as scaffolds for organizing the USH interactome. RNA-seq analysis of human retinae uncovered harmonin_a1 as the most abundant transcript of USH1C. Bulk RNA-seq analysis and immunoblotting showed abundant expression of harmonin in Müller glia cells (MGCs) and retinal neurons. Furthermore, harmonin was localized in the terminal endfeet and apical microvilli of MGCs, presynaptic region (pedicle) of cones and outer segments (OS) of rods as well as at adhesive junctions between MGCs and photoreceptor cells (PRCs) in the outer limiting membrane (OLM). Our data provide evidence for the interaction of harmonin with OLM molecules in PRCs and MGCs and rhodopsin in PRCs. Subcellular expression and colocalization of harmonin correlate with the clinical phenotype observed in USH1C patients. We also demonstrate that primary cilia defects in USH1C patient-derived fibroblasts could be reverted by the delivery of harmonin_a1 transcript isoform. Our studies thus provide novel insights into PRC cell biology, USH1C pathophysiology and development of gene therapy treatment(s).

How to Predict the Suitability for Corneal Donorship?

BACKGROUND: In Germany, more than one-third of donor corneas harvested are not suitable for transplantation. We evaluated the factors associated with the usability of donor corneas. METHOD: Data from 2032 consecutive donor corneas harvested at the Rhineland-Palatinate Eye Bank in Mainz, Germany, were retrospectively analyzed. Factors of interest were age, sex, lens status, cause of death, cardiopulmonary resuscitation (CPR), death-to-explantation-interval (DEI), and the influence of these factors on the proportion of discarded donor corneas. Factors associated with endothelial cell density (ECD) were analyzed in a linear regression mixed model. RESULTS: Higher donor age, male gender, pseudophakic lens status, and longer DEI were associated with significantly reduced ECD. With respect to DEI, the estimated cell loss was 7 ± 2 cells/mm2/hour (p < 0.001). Age was associated with a lower ECD of 6 ± 2 cells/mm2 per year (p = 0.001). Female ECD was 189 ± 44 cells/mm2 higher than male ECD (p < 0.001). Pseudophakic eyes had 378 ± 42 cells/mm2 less compared with phakic eyes (p < 0.001). Cause of death did not affect the ECD. Of note, 55% and 38% of corneas harvested on the second and third postmortem day, respectively, and 45% of corneas from donors older than 80 years were still suitable for transplantation. CONCLUSIONS: In the context of a growing need for donor corneas, we do not recommend limiting donor age and collection time to 24 h or excluding oncology donors, as is the practice in many countries. Therefore, we propose a mathematical model for better donor preselection.

SARS-CoV-2: Impact on, Risk Assessment and Countermeasures in German Eye Banks.

INTRODUCTION: Since the beginning of the COVID-19 pandemic there has been some debate regarding the risk of transmission through tissue transplantation and tissue banking processes. AIM OF THE STUDY: To analyze the changes that SARS-CoV-2 has caused regarding the harvesting of corneal donor tissue and eye bank activities in Germany. METHODS: A questionnaire was provided to 26 eye banks in Germany, consisting of questions about adaptations made in the screening of potential donors and the harvesting of corneal tissue following the pandemic spread of SARS-CoV-2. RESULTS: Eighteen eye banks actively reduced recruitment of donors and two banks ceased all activity. Additional diagnostic screening was performed in eight banks, using conjunctival swabs and/or nasopharyngeal swabs. In six eye banks, additional protective measures, such as FFP2 masks and/or facial shields, were implemented. Overall, a mean reduction in the number of obtained donor tissues of 17% was observed. DISCUSSION: Conjunctival and/or nasopharyngeal swabs of donors have been implemented by a minority. Reasons for not performing additional tests may be moderate sensitivity and lack of validation for postmortem use of RT-PCR testing. Also, the hazard of SARS-CoV-2 entering the corneal donor pool with subsequent transmission might be perceived as theoretical. Face shields provide a sufficient barrier against splash and splatter contamination but may be insufficient against aerosols. Additional face masks would provide support against aerosols, but it remains debatable if corneal harvesting can be considered an aerosol-producing procedure. In the future we expect to see changes in current guidelines because of a surge in scientific activities to improve our understanding of the risks involved with cornea donation in the COVID-19 pandemic, and because current practice may reduce the availability of donor corneas due to new exclusion criteria while the demand remains unchanged.