The genetic basis for adult onset glaucoma: Recent advances and future directions

An ultra-high-performance tandem mass spectrometry method to quantify tryptophan metabolites in aqueous humor of primary angle-closure glaucoma patients

This study presented the development and validation of a robust ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for the simultaneous quantification of tryptophan (TRP) and its nine metabolites in aqueous humor (AH) to explore the regulation of the TRP metabolic pathway in primary angle-closure glaucoma (PACG). The optimized UPLC-MS/MS method demonstrated good linearity (R² > 0.99), sensitivity (LLMI: 0.11 - 1.31 ng/mL), precision (CVs: 2.18 % and 12.88 %), recovery rates (85.06 % - 105.74 %), bench-top, long-term and on-instrument stabilities (CVs: 2.35 % - 6.88 %). The validated UPLC-MS/MS method was applied to AH samples from PACG patients with cataract and cataract-alone patients. The results showed that kynurenine and 3-hydroxykynurenine concentrations were significantly increased in the AH of the PACG group, indicating up-regulated indoleamine 2,3-dioxygenase activity and a metabolic shift towards the production of the neurotoxic metabolites within the kynurenine pathway. These findings underscore the potential involvement of TRP metabolism in PACG pathogenesis.

Emerging trends in long-acting sustained drug delivery for glaucoma management

Glaucoma is an optic neuropathy in which progressive degeneration of retinal ganglion cells and the optic nerve leads to irreversible visual loss. Glaucoma is one of the leading causes of blindness. The pathogenesis of glaucoma is determined by different pathogenetic mechanisms, including increased intraocular pressure, mechanical stress, excitotoxicity, resistance to aqueous drainage and oxidative stress. Topical formulations are often used in glaucoma treatment, whereas surgical measures are used in acute glaucoma cases. For most patients, long-term glaucoma treatments are given. Poor patient compliance and low bioavailability are often associated with topical therapy, which suggests that sustained-release, long-acting drug delivery systems could be beneficial in managing glaucoma. This review summarizes the eye's physiology, the pathogenesis of glaucoma, current treatments, including both pharmacological and nonpharmacological interventions, and recent advances in long-acting drug delivery systems for the treatment of glaucoma.

Changes in eye axis length and corneal curvature in central China from the perspective of birth year

OBJECTIVES

To explore the changes in eye structures over time in the Chinese population from the perspective of birth year.

METHODS

We collected measurement data of intraocular lens Master from patients who underwent intraocular lens Master biometry for a routine cataract or refractive examination (ametropia and presbyopia) between April 2012 and October 2023, then screened them. Selected patients were divided into ten groups of 10 years each according to their year of birth (called birth decades). Birth-year-dependent changes in axial length and corneal curvature were compared between the groups.

RESULTS

The average axial length increased from 23.52 mm to 25.95 mm, and the corneal curvature dropped from 44.20 D to 43.33 D in patients born in before-1930 and 1990s. The proportion of short average axial length and steep corneal curvature decreased, whereas the proportion of long average axial length increased with the birth decade. The proportion of patients with corneal curvature < 40 D was 4.18% in 1970s, 5.73% in 1980s, and 3.38% in 1990s, which were significantly higher than those of other age groups. The average axial length of the eyes among primary school students was 23.96 mm, and among college students, it was 25.86 mm.

CONCLUSIONS

Overall, with the birth decade, average axial length increased and corneal curvature decreased. There were generational differences in ocular biological parameters, changes in the eye might affect the incidence of eye diseases such as glaucoma and fundus diseases, which in turn might lead to changes in the spectrum of eye diseases.

Prevalence of MYOC mutations in a cohort of juvenile open-angle glaucoma (JOAG) patients from Sub-Saharan Africa

PURPOSE

Determine the prevalence and the role of myocilin (MYOC) gene mutations in a sub-Saharan population of juvenile open-angle glaucoma (JOAG) patients DESIGN: Prospective case-control PARTICIPANTS: 45 JOAG patients and 41 normal control subjects from the ophthalmology clinics of the University College Hospital Ibadan, Nigeria.

METHODS

DNA was tested for MYOC coding sequence mutations using Sanger sequencing. Identified mutations were evaluated for pathogenicity by 1) ClinGen scoring 2) assessing prevalence in large public databases of patients with African ancestry (gnomAD and 1000 Genomes); and 3) Mutation analysis algorithms (PolyPhen, SIFT, Blosum62, MutationTaster, CADD, and AlphaMissense). The prevalence of variants was compared between JOAG patients and normal controls from Ibadan using a mutation burden analysis using SKAT-O.

MAIN OUTCOME MEASURES

Sanger DNA sequencing data indicating the presence or absence of glaucoma-causing mutations in the MYOC gene.

RESULTS

A total of 10 instances of 4 MYOC variants were detected. A p.Pro370Leu variant, which has been previously categorized by the ClinGen as Pathogenic, was detected in three (6.7%) of 45 JOAG probands. A p.Arg470Cys MYOC variant, previously categorized a Variant of Unknown Significance, was identified in one (2.2%) of 45 JOAG probands. A p.Glu352Lys variant, previously categorized as Benign, was detected in 2 (4.4%) of JOAG probands. Both the p.Pro370Leu and p.Arg470Cys variants were absent from control subjects and large public databases, while p.Glu352Lys was present at a frequency >1%, which is inconsistent with pathogenicity. Finally, synonymous missense variant, p.Glu396Glu, was also detected. Five of six mutation analysis algorithms supported the pathogenicity of the p.Pro370Leu and p.Arg470Cys variants, while slightly fewer (4 of 6) suggested that p.Glu352Lys is pathogenic.

CONCLUSIONS

MYOC mutations are the most common known cause of JOAG in populations of European ancestry. Our case-control study estimated the prevalence of pathogenic MYOC mutations to be 8.9% in an African population from Nigeria. MYOC mutations are the most common known cause of JOAG in sub-Saharan Africa, however, they account for a minority of cases.

Five-year outcomes of trabeculo-canalectomy for Chinese PACG patients: a retrospective study

BACKGROUND

To evaluate the 5-year outcomes of trabeculo-canalectomy in the treatment of primary angle-closure glaucoma (PACG) among Chinese patients.

METHODS

A retrospective study was designed, involving 46 PACG patients (50 eyes) treated with trabeculo-canalectomy at the First Affiliated Hospital of Nanjing Medical University from January 2016 to December 2018. The patients were followed up at 1 week, 1 month, 3 months, 6 months, 12 months, 1 year, 2 years and 5 years. Surgical success was defined as intraocular pressure (IOP) ≤ 21 mmHg (1 mmHg = 0.133 kPa) under glaucoma medication (qualified success) and without any glaucoma medication (absolute success). Main outcomes were measured according to IOP, number of medication regimens, surgical success rate, complications, and filtering bleb status.

RESULTS

A total of 46 PACG patients (50 eyes) were finally included for statistical analysis, with a mean age of 56.68 ± 6.75 years (range, 41-69 years). The mean preoperative IOP was 30.72 ± 10.26 mmHg with a median number of medication regimens of 2 (range, 0 to 4). Compared to those before the operation, the mean IOP decreased to 12.15 ± 3.11, 14.33 ± 4.10, 15.68 ± 4.24, 16.45 ± 4.14, 16.95 ± 3.51, 17.67 ± 3.15 and 17.04 ± 3.78 mmHg at 1 week, 1 month, 3 months, 6 months, 12 months, 1 year, 2 years and 5 years, respectively. The median (range) numbers of medication regimens were 0 (0 ~ 1), 0 (0 ~ 2), 0 (0 ~ 2), 0 (0 ~ 2), 0 (0 ~ 2), 0 (0 ~ 3), 0 (0 ~ 3), 0 (0 ~ 3) at the eight time points, respectively. The mean postoperative IOP and the number of medication regimens at each time point were significantly lower than those before operation (all P < 0.01). The 5-year total success rate was 89%, and the absolute success rate was 78%. Shallow anterior chamber (10%) and hyphema (12%) were the most common complications early after surgery. At 3 months, anterior segment slit-lamp photography and ultrasound biomicroscopy showed no obvious filtering blebs in 50 eyes (100%). IOP increased transiently in 6 eyes (12%) within 1 month after surgery.

CONCLUSION

Simple and cost-saving trabeculo-canalectomy provides favorable 5-year outcomes in the treatment of medically uncontrolled PACG, as shown by more effective IOP control, more obvious drug reduction, as well as fewer post-operative interventions compared to trabeculectomy.

Genetic Risk for Open-Angle Glaucoma Subtypes Is Associated with Specific Visual Field Defect Classes

PURPOSE

We investigated visual field (VF) archetype-genotype associations for open-angle glaucoma (OAG) and its subtypes, high-tension glaucoma (HTG) and normal-tension glaucoma (NTG).

DESIGN

Cross-sectional, population-based study.

PARTICIPANTS

A total of 79 357 VF results from 11 572 patients with OAG at Massachusetts Eye and Ear (2012-2022) were used to identify VF archetypes. Archetype-genotype correlations were performed on participants with genotyping data, VF results, and OAG codes (H40.1x) from the Mass General Brigham Biobank, and 3 Health Professional Cohorts (n = 1517) with primary open-angle glaucoma (POAG) and reproducible VF loss.

METHODS

Primary open-angle glaucoma polygenic risk score (PRS), NTG PRS, and weighted HTG genetic risk score (GRS) from genome-wide association studies were calculated for 1517 participants (2408 eyes). Logistic regression assessed VF archetype-genotype associations.

MAIN OUTCOME MEASURES

Associations between PRS or GRS and VF archetypes.

RESULTS

Nine archetypes were identified, including normal and various paracentral, peripheral, and total loss patterns. In a logistic regression model adjusted for age, sex, and ancestry, a 1-standard deviation (SD) increase in POAG PRS was linked to 1.65-times higher odds of paracentral defects (adjusted odds ratio [aOR], 1.65; 95% confidence interval [CI], 1.32-2.08) and 1.30-times higher odds of peripheral defects (aOR, 1.3; 95% CI, 1.14-1.48). A 1-SD increase in NTG PRS was associated with 1.69-times higher odds of paracentral defects (aOR, 1.69; 95% CI, 1.23-2.3) and 1.28-times higher odds of peripheral defects (aOR, 1.28; 95% CI, 1.06-1.54). A 1-SD increase in HTG GRS was linked to 0.68-times lower odds of both paracentral defects (aOR, 0.68; 95% CI, 0.57-0.82) and peripheral defects (aOR, 0.68; 95% CI, 0.62-0.76). A 1-SD increase in HTG GRS also was associated with 1.31-times higher odds of total loss (OR, 1.31; 95% CI, 1.01-1.77) in an unadjusted model, but was not significant in the adjusted model.

CONCLUSIONS

Higher POAG PRSs and NTG PRSs were associated with paracentral VF loss, whereas higher HTG GRS was linked to total VF loss, but not paracentral defects. Genetic risk for glaucoma subtypes is associated with specific VF defects, which may affect disease diagnosis and prognostication.

FINANCIAL DISCLOSURE(S)

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Association between gene polymorphisms and glaucoma susceptibility among Africans: a systematic review and meta-analysis

PURPOSE

This study sought to analyze the effect of allele mutations and gene functions specific to glaucoma susceptibility among Africans.

METHODS

Potentially relevant studies were retrieved from major bibliographic databases (PubMed, Scopus, and Web of Science). Data were extracted and study-specific estimates were meta-analyzed using various models to obtain pooled results.

RESULTS

A total of 11 studies were included in the study. The studies included a total of 3,191 cases with glaucoma and 3,013 controls across all variants. There is no association between the E396E variants of the myocilin (MYOC) gene and an increased likelihood of susceptibility to POAG (OR: 0.91 [95% CI 0.42 to 1.97]). The R141L variant of the Lysyl Oxidase Like 1 (LOXL1) gene is associated with an approximately 3-fold increased likelihood of susceptibility to exfoliative syndrome/exfoliative glaucoma (XFS/XFG) (OR: 2.68 [95% CI 0.04 to 198.94]). There is no association between the G153D variant of the LOXL1 gene and an increased likelihood of susceptibility to XFS/XFG (OR: 0.42 [95% CI 0.02 to 7.65]). The rs59892895*C variant of the Amyloid Beta Precursor Protein Binding Family B Member 2 (APBB2) is associated with a 34% increased likelihood of susceptibility to POAG (OR: 1.34 [95% CI 1.13 to 1.58]).

CONCLUSION

Although progress has been made in understanding the genetic basis of the pathogenesis of glaucoma, several gene mutations related to glaucoma pathogenesis in Africans are yet to be discovered, especially those associated with the pathogenesis of POAG, the most prevalent glaucoma subtype in Africa.

Genome-wide association studies, Polygenic Risk Scores and Mendelian randomisation: an overview of common genetic epidemiology methods for ophthalmic clinicians

Genetic information will be increasingly integrated into clinical eye care within the current generation of ophthalmologists. For monogenic diseases such as retinoblastoma, genetic studies have been relatively straightforward as these conditions result from pathogenic variants in a single gene resulting in large physiological effects. However, most eye diseases result from the cumulative effects of multiple genetic variants and environmental factors. In such diseases, because each variant usually has an individually small effect, genetic studies for complex diseases are comparatively more challenging. This article aims to provide an overview of three genetic epidemiology methods for polygenic (or complex) diseases: genome-wide association studies (GWAS), Polygenic Risk Scores (PRS) and Mendelian randomisation (MR). A GWAS systematically conducts association analyses of a trait of interest against millions of genetic variants, usually in the form of single nucleotide polymorphisms, across the genome. GWAS findings can then be used for PRS construction and MR analyses. To construct a PRS, the cumulative effect of many genetic variants associated with a trait from a prior GWAS is calculated and taken as a quantitative representation of an individual's genetic risk of a complex disease. MR studies analyse an outcome measure against the genetic variants of an exposure, and are particularly useful in investigating causal relations between two traits where randomised controlled trials are not possible or ethical. In addition to explaining the principles of these three genetic epidemiology concepts, this article provides a minimally technical description of their basic methodology that is accessible to the non-expert reader.

Small extracellular vesicles derived from human induced pluripotent stem cell-differentiated neural progenitor cells mitigate retinal ganglion cell degeneration in a mouse model of optic nerve injury

JOURNAL/nrgr/04.03/01300535-202502000-00034/figure1/v/2024-05-28T214302Z/r/image-tiff Several studies have found that transplantation of neural progenitor cells (NPCs) promotes the survival of injured neurons. However, a poor integration rate and high risk of tumorigenicity after cell transplantation limits their clinical application. Small extracellular vesicles (sEVs) contain bioactive molecules for neuronal protection and regeneration. Previous studies have shown that stem/progenitor cell-derived sEVs can promote neuronal survival and recovery of neurological function in neurodegenerative eye diseases and other eye diseases. In this study, we intravitreally transplanted sEVs derived from human induced pluripotent stem cells (hiPSCs) and hiPSCs-differentiated NPCs (hiPSC-NPC) in a mouse model of optic nerve crush. Our results show that these intravitreally injected sEVs were ingested by retinal cells, especially those localized in the ganglion cell layer. Treatment with hiPSC-NPC-derived sEVs mitigated optic nerve crush-induced retinal ganglion cell degeneration, and regulated the retinal microenvironment by inhibiting excessive activation of microglia. Component analysis further revealed that hiPSC-NPC derived sEVs transported neuroprotective and anti-inflammatory miRNA cargos to target cells, which had protective effects on RGCs after optic nerve injury. These findings suggest that sEVs derived from hiPSC-NPC are a promising cell-free therapeutic strategy for optic neuropathy.

Insights on the Genetic and Phenotypic Complexities of Optic Neuropathies

Background/Objectives: Optic neuropathies are a category of illnesses that ultimately cause damage to the optic nerve, leading to vision impairment and possible blindness. Disorders such as dominant optic atrophy (DOA), Leber hereditary optic neuropathy (LHON), and glaucoma demonstrate intricate genetic foundations and varied phenotypic manifestations. This narrative review study seeks to consolidate existing knowledge on the genetic and molecular mechanisms underlying ocular neuropathies, examine genotype-phenotype correlations, and assess novel therapeutic options to improve diagnostic and treatment methodologies. Methods: A systematic literature review was performed in October 2024, utilizing PubMed, Medline, the Cochrane Library, and ClinicalTrials.gov. Search terms encompassed "optic neuropathy", "genetic variants", "LHON", "DOA", "glaucoma", and "molecular therapies". Studies were chosen according to established inclusion criteria, concentrating on the genetic and molecular dimensions of optic neuropathies and their therapeutic ramifications. Results: The results indicate that DOA and LHON are mostly associated with the mitochondrial dysfunction resulting from pathogenic variants in nuclear genes, mainly OPA1, and mitochondrial DNA (mtDNA) genes, respectively. Glaucoma, especially its intricate variants, is linked to variants in genes like MYOC, OPTN, and TBK1. Molecular mechanisms, such as oxidative stress and inflammatory modulation, are pivotal in disease progression. Innovative therapeutics, including gene therapy, RNA-based treatments, and antioxidants such as idebenone, exhibit promise for alleviating optic nerve damage and safeguarding vision. Conclusions: Genetic and molecular investigations have markedly enhanced our comprehension of ocular neuropathies. The amalgamation of genetic and phenotypic data is essential for customized medical strategies. Additional research is required to enhance therapeutic strategies and fill the gaps in our understanding of the underlying pathophysiology. This interdisciplinary approach shows potential for enhancing patient outcomes in ocular neuropathies.

Glaucoma and dietary links: insights from high-salt intake, the Mediterranean diet, and specific nutrients

Glaucoma, a prevalent and potentially blinding eye disease, is linked to a variety of factors, including elevated intraocular pressure, optic nerve damage, and oxidative stress. In recent years, dietary habits, as a controllable lifestyle factor, have received increasing attention in the prevention and treatment of glaucoma. The purpose of this review was to investigate the effects of dietary factors on glaucoma, with a particular emphasis on two common dietary patterns: the high-salt diet and the Mediterranean diet. In addition, we investigated the association between many particular nutrients (including omega-3 fatty acids, vitamins, caffeine, and minerals) and glaucoma to fully assess the potential involvement of dietary variables in glaucoma pathogenesis, prevention, and treatment. This article reveals the importance of dietary components in glaucoma prevention and explores prospective possibilities for future research by conducting a comprehensive review of previous scientific studies.

Associations between Disc Hemorrhage and Primary Open-Angle Glaucoma Based on Genome-Wide Association and Mendelian Randomization Analyses

Background/Objectives: We aimed to investigate the genetic loci related to disc hemorrhage (DH) and the relationship of causation between DH and primary open-angle glaucoma (POAG) using a genome-wide association study (GWAS) in East Asian individuals. Methods: The GWAS included 8488 Koreans who underwent ocular examination including fundus photography to determine the presence of DH and POAG. We performed a GWAS to identify significant single-nucleotide polymorphisms (SNPs) associated with DH and analyzed the heritability of DH and genetic correlation between DH and POAG. The identified SNPs were utilized as instrumental variables (IVs) for two-sample Mendelian randomization (MR) analysis. The POAG outcome dataset was adopted from Biobank Japan data (n = 179,351). Results: We found that the rs62463744 (TMEM270;ELN), rs11658281 (CCDC42), and rs77127203 (PDE10A;LINC00473) SNPs were associated with DH. The SNP heritability of DH was estimated to be 6.7%, with an absence of a genetic correlation with POAG. MR analysis did not reveal a causal association between DH and POAG for East Asian individuals. Conclusions: The novel loci underlying DH in the Korean cohort revealed SNPs in the ELN, CCDC41, and LINC00473 genes. The absence of a causal association between DH and POAG implies that DH is a shared risk factor, rather than an independent culprit factor, and warrants further investigation.

Minimal phenotypes in transgenic mice with the human LOXL1/LOXL1-AS1 locus associated with exfoliation glaucoma

Exfoliation syndrome is a leading cause of secondary glaucoma worldwide. Among the risk-factors for exfoliation syndrome and exfoliation glaucoma that have been investigated, a genetic association with 15q24.1 is among the most striking. The leading candidates for the causal gene at this locus are LOXL1 and/or LOXL1-AS1, but studies have not yet coalesced in establishing, or ruling out, either candidate. Here, we contribute to studies of the 15q24.1 locus by making a partially humanized mouse model in which 166 kb of human genomic DNA from the 15q24.1 locus was introduced into the mouse genome via BAC transgenesis (B6-Tg(RP11-71M11)Andm). Transgenic expression of human genes in the BAC was only detectable for LOXL1-AS1. One cohort of 34 mice (21 experimental hemizygotes and 13 non-carrier control littermates) was assessed by slit-lamp exams and SD-OCT imaging at early (1-2 months) and mid (4-5 months) time points; fundus exams were performed at 5 months of age. A second smaller cohort (3 hemizygotes) were aged extensively (>12 months) to screen for overt abnormalities. Across all genotypes and ages, 136 slit-lamp exams, 128 SD-OCT exams, and 42 fundus exams detected no overt indices of exfoliation syndrome. Quantitatively, small, but statistically significant, age-related declines in ganglion cell complex thickness and total retinal thickness were detected in the hemizygotes at 4 months of age. Overall, this study demonstrates complexity in gene regulation from the 15q24.1 locus and suggests that LOXL1-AS1 is unlikely to be a monogenic cause of exfoliation syndrome but may contribute to glaucomatous retinal damage.

Polygenic Risk Scores Driving Clinical Change in Glaucoma

Glaucoma is a clinically heterogeneous disease and the world's leading cause of irreversible blindness. Therapeutic intervention can prevent blindness but relies on early diagnosis, and current clinical risk factors are limited in their ability to predict who will develop sight-threatening glaucoma. The high heritability of glaucoma makes it an ideal substrate for genetic risk prediction, with the bulk of risk being polygenic in nature. Here, we summarize the foundations of glaucoma genetic risk, the development of polygenic risk prediction instruments, and emerging opportunities for genetic risk stratification. Although challenges remain, genetic risk stratification will significantly improve glaucoma screening and management.

TRPV4 subserves physiological and pathological elevations in intraocular pressure

Ocular hypertension (OHT) caused by mechanical stress and chronic glucocorticoid exposure reduces the hydraulic permeability of the conventional outflow pathway. It increases the risk for irreversible vision loss, yet healthy individuals experience nightly intraocular pressure (IOP) elevations without adverse lifetime effects. It is not known which pressure sensors regulate physiological vs. pathological OHT nor how they impact the permeability of the principal drainage pathway through the trabecular meshwork (TM). We report that OHT induced by the circadian rhythm, occlusion of the iridocorneal angle and glucocorticoids requires activation of TRPV4, a stretch-activated cation channel. Wild-type mice responded to nocturnal topical administration of the agonist GSK1016790A with IOP lowering, while intracameral injection of the agonist elevated diurnal IOP. Microinjection of TRPV4 antagonists HC067047 and GSK2193874 lowered IOP during the nocturnal OHT phase and in hypertensive eyes treated with steroids or injection of polystyrene microbeads. Conventional outflow-specific Trpv4 knockdown induced partial IOP lowering in mice with occluded iridocorneal angle and protected retinal neurons from pressure injury. Indicating a central role for TRPV4-dependent mechanosensing in trabecular outflow, HC067047 doubled the outflow facility in TM-populated steroid-treated 3D nanoscaffolds. Tonic TRPV4 signaling thus represents a fundamental property of TM biology as a driver of increased in vitro and in vivo outflow resistance. The TRPV4-dependence of OHT under conditions that mimic primary and secondary glaucomas could be explored as a novel target for glaucoma treatments.

The accuracy of self-reported family history in glaucoma in Brazil

PURPOSE

To evaluate the accuracy of a positive self-reported glaucoma family history.

MATERIAL AND METHODS

Cross-sectional study. Each subject was asked if they had a first-degree relative diagnosed with glaucoma. If their answer was affirmative, the relative was invited to attend on ophthalmic evaluation and underwent complementary exams to confirm or exclude the glaucoma diagnosis. Only one relative was included per subject.

RESULTS

We included 204 subjects in the study (102 subjects and their respective relatives). The accuracy of family history of glaucoma was 76.96% of the cases. In the univariable analysis, subjects with college degree had 2.34 [(P = 0.010; 95% confidence interval (CI) 1.18-4.63)], with higher family income 3.72 (P = 0.003; 95% CI 1.57-8.85) and those with health insurance 3.42 (P = 0.001; 95% CI 1.67-6.98) more chances to have a true positive family history for glaucoma. In the multivariable logistic regression analysis, none of the variables presented significant association.

CONCLUSION

Around 24% of patients may not provide reliable information about family history for glaucoma. When asking about a glaucoma family history, clinicians should consider the real accuracy of this self-reported data.

Lack of evidence for GWAS signals of exfoliation glaucoma working via monogenic loss-of-function mutation in the nearest gene

PURPOSE

Exfoliation syndrome (XFS) is a systemic disease of elastin-rich tissues involving a deposition of fibrillar exfoliative material (XFM) in the anterior chamber of the eye, which can promote glaucoma. The purpose of this study was to create mice with CRISPR/Cas9-induced variations in candidate genes identified from human genome-wide association studies (GWAS) and screen them for indices of XFS.

METHODS

Variants predicted to be deleterious were sought in the Agpat1, Cacna1a, Loxl1, Pomp, Rbms3, Sema6a, and Tlcd5 genes of C57BL/6J mice using CRISPR/Cas9-based gene editing. Strains were phenotyped by slit-lamp, SD-OCT imaging, and fundus exams at 1-5 mos of age. Smaller cohorts of 12-mos-old mice were also studied.

RESULTS

Deleterious variants were identified in six targets; Pomp was recalcitrant to targeting. Multiple alleles of some targets were isolated, yielding 12 strains. Across all genotypes and ages, 277 mice were assessed by 902 slit-lamp exams, 928 SD-OCT exams, and 358 fundus exams. Homozygosity for Agpat1 or Cacna1a mutations led to early lethality; homozygosity for Loxl1 mutations led to pelvic organ prolapse, preventing aging. Loxl1 homozygotes exhibited a conjunctival phenotype of potential relevance to XFS. Multiple other genotype-specific phenotypes were variously identified. XFM was not observed in any mice.

CONCLUSIONS

This study did not detect XFM in any of the strains. This may have been due to species-specific differences, background dependence, or insufficient aging. Alternatively, it is possible that the current candidates, selected based on proximity to GWAS signals, are not effectors acting via monogenic loss-of-function mechanisms.

Modeling complex age-related eye disease

Modeling complex eye diseases like age-related macular degeneration (AMD) and glaucoma poses significant challenges, since these conditions depend highly on age-related changes that occur over several decades, with many contributing factors remaining unknown. Although both diseases exhibit a relatively high heritability of >50%, a large proportion of individuals carrying AMD- or glaucoma-associated genetic risk variants will never develop these diseases. Furthermore, several environmental and lifestyle factors contribute to and modulate the pathogenesis and progression of AMD and glaucoma. Several strategies replicate the impact of genetic risk variants, pathobiological pathways and environmental and lifestyle factors in AMD and glaucoma in mice and other species. In this review we will primarily discuss the most commonly available mouse models, which have and will likely continue to improve our understanding of the pathobiology of age-related eye diseases. Uncertainties persist whether small animal models can truly recapitulate disease progression and vision loss in patients, raising doubts regarding their usefulness when testing novel gene or drug therapies. We will elaborate on concerns that relate to shorter lifespan, body size and allometries, lack of macula and a true lamina cribrosa, as well as absence and sequence disparities of certain genes and differences in their chromosomal location in mice. Since biological, rather than chronological, age likely predisposes an organism for both glaucoma and AMD, more rapidly aging organisms like small rodents may open up possibilities that will make research of these diseases more timely and financially feasible. On the other hand, due to the above-mentioned anatomical and physiological features, as well as pharmacokinetic and -dynamic differences small animal models are not ideal to study the natural progression of vision loss or the efficacy and safety of novel therapies. In this context, we will also discuss the advantages and pitfalls of alternative models that include larger species, such as non-human primates and rabbits, patient-derived retinal organoids, and human organ donor eyes.

Polygenic risk score-based phenome-wide association for glaucoma and its impact on disease susceptibility in two large biobanks

BACKGROUND

Glaucoma is a leading cause of worldwide irreversible blindness. Considerable uncertainty remains regarding the association between a variety of phenotypes and the genetic risk of glaucoma, as well as the impact they exert on the glaucoma development.

METHODS

We investigated the associations of genetic liability for primary open angle glaucoma (POAG) with a wide range of potential risk factors and to assess its impact on the risk of incident glaucoma. The phenome-wide association study (PheWAS) approach was applied to determine the association of POAG polygenic risk score (PRS) with a wide range of phenotypes in 377, 852 participants from the UK Biobank study and 43,623 participants from the Penn Medicine Biobank study, all of European ancestry. Participants were stratified into four risk tiers: low, intermediate, high, and very high-risk. Cox proportional hazard models assessed the relationship of POAG PRS and ocular factors with new glaucoma events.

RESULTS

In both discovery and replication set in the PheWAS, a higher genetic predisposition to POAG was specifically correlated with ocular disease phenotypes. The POAG PRS exhibited correlations with low corneal hysteresis, refractive error, and ocular hypertension, demonstrating a strong association with the onset of glaucoma. Individuals carrying a high genetic burden exhibited a 9.20-fold, 11.88-fold, and 28.85-fold increase in glaucoma incidence when associated with low corneal hysteresis, high myopia, and elevated intraocular pressure, respectively.

CONCLUSION

Genetic susceptibility to POAG primarily influences ocular conditions, with limited systemic associations. Notably, the baseline polygenic risk for POAG robustly associates with new glaucoma events, revealing a large combined effect of genetic and ocular risk factors on glaucoma incidents.

Rodent genetically modified models of glaucoma

Glaucoma, one of the leading causes of irreversible blindness worldwide, is a complex and heterogenous disease. While environmental factors are important, it is well-recognized that the disease has a strong heritable component. With the advent of large-cohort genome wide association studies, a myriad of genetic risk loci has been linked to different forms of glaucoma. Animal models have been an indispensable tool in characterizing these loci, especially if they lie within coding regions in the genome. Not only do these models connect genotype to phenotype, advancing our understanding of glaucoma pathogenesis in the process, they also have valuable utility as a platform for the pre-clinical testing of potential therapies. In this review, we will outline genetic models used for studying the major forms of glaucoma, including primary open angle glaucoma, normal tension glaucoma, primary angle closure glaucoma, pigmentary glaucoma, pseudoexfoliation glaucoma, and early onset glaucoma, including congenital and developmental glaucoma, and how studying these models have helped shed light on human glaucoma.

Glaucoma: from pathogenic mechanisms to retinal glial cell response to damage

Glaucoma is a neurodegenerative disease of the retina characterized by the irreversible loss of retinal ganglion cells (RGCs) leading to visual loss. Degeneration of RGCs and loss of their axons, as well as damage and remodeling of the lamina cribrosa are the main events in the pathogenesis of glaucoma. Different molecular pathways are involved in RGC death, which are triggered and exacerbated as a consequence of a number of risk factors such as elevated intraocular pressure (IOP), age, ocular biomechanics, or low ocular perfusion pressure. Increased IOP is one of the most important risk factors associated with this pathology and the only one for which treatment is currently available, nevertheless, on many cases the progression of the disease continues, despite IOP control. Thus, the IOP elevation is not the only trigger of glaucomatous damage, showing the evidence that other factors can induce RGCs death in this pathology, would be involved in the advance of glaucomatous neurodegeneration. The underlying mechanisms driving the neurodegenerative process in glaucoma include ischemia/hypoxia, mitochondrial dysfunction, oxidative stress and neuroinflammation. In glaucoma, like as other neurodegenerative disorders, the immune system is involved and immunoregulation is conducted mainly by glial cells, microglia, astrocytes, and Müller cells. The increase in IOP produces the activation of glial cells in the retinal tissue. Chronic activation of glial cells in glaucoma may provoke a proinflammatory state at the retinal level inducing blood retinal barrier disruption and RGCs death. The modulation of the immune response in glaucoma as well as the activation of glial cells constitute an interesting new approach in the treatment of glaucoma.

Understanding the complex genetics and molecular mechanisms underlying glaucoma

Glaucoma is the leading cause of irreversible blindness worldwide. Currently the only effective treatment for glaucoma is to reduce the intraocular pressure, which can halt the progression of the disease. Highlighting the importance of identifying individuals at risk of developing glaucoma and those with early-stage glaucoma will help patients receive treatment before sight loss. However, some cases of glaucoma do not have raised intraocular pressure. In fact, glaucoma is caused by a variety of different mechanisms and has a wide range of different subtypes. Understanding other risk factors, the underlying mechanisms, and the pathology of glaucoma might lead to novel treatments and treatment of underlying diseases. In this review we present the latest research into glaucoma including the genetics and molecular basis of the disease.

Matrix Metalloproteinases in Glaucoma: An Updated Overview

Matrix metalloproteinases (MMPs) are important regulators of the extracellular matrix (ECM) and are involved in many stages of cellular growth and development. An imbalance of MMP expression is also the basis of many diseases, including eye diseases, such as diabetic retinopathy (DR), glaucoma, dry eye, corneal ulcer, keratoconus. This paper describes the role of MMPs in the glaucoma and their role in the glaucomatous trabecular meshwork (TM), aqueous outflow channel, retina, and optic nerve (ON). This review also summarizes several treatments for glaucoma that target MMPs imbalance and suggests that MMPs may represent a viable therapeutic target for glaucoma.

Advances in understanding glaucoma pathogenesis: A multifaceted molecular approach for clinician scientists

Glaucoma, a leading cause of irreversible blindness worldwide, is a spectrum of neurodegenerative diseases characterized by the gradual deterioration of retinal ganglion cells (RGCs) and optic neuropathy. With complex etiology, glaucoma's major risk factors include elevated intraocular pressure (IOP), advanced age, ethnicity, systemic vascular factors, and genetic predisposition. By 2040, glaucoma is expected to affect over 110 million individuals aged 40 to 80, posing a significant economic burden. Glaucoma can be classified into open-angle, angle-closure, and developmental subtypes, with primary and secondary forms. The disease often progresses silently, gradually impairing the visual field (VF) until it reaches an advanced stage. Understanding the abnormal functional changes associated with glaucoma at the tissue, cellular, molecular, and genetic levels is crucial for comprehending its pathogenesis. This review examines the published data from the past two decades to shed light on the biological mechanisms underlying glaucoma development. The most evident factors in the development of glaucomatous optic neuropathy include elevated IOP, aging, genetic influences, followed by impaired ocular blood flow regulation. These factors are interconnected processes that lead to optic nerve damage, compromised circulation, and structural changes in glial and connective tissues. Contributing factors involve extracellular matrix remodeling, excitotoxicity, nitric oxide, oxidative stress, and neuroinflammation. Ultimately, all types of glaucoma result in RGC dysfunction and loss, causing irreversible visual impairment. While our understanding of glaucoma pathogenesis is evolving, further research is crucial for a comprehensive understanding of glaucoma pathogenesis and the development of effective treatments.

Lysyl oxidase-like 1-antisense 1 (LOXL1-AS1) lncRNA differentially regulates gene and protein expression, signaling and morphology of human ocular cells

Pseudoexfoliation glaucoma (PEXG) is characterized by dysregulated extracellular matrix (ECM) homeostasis that disrupts conventional outflow function and increases intraocular pressure (IOP). Prolonged IOP elevation results in optic nerve head damage and vision loss. Uniquely, PEXG is a form of open angle glaucoma that has variable penetrance, is difficult to treat and does not respond well to common IOP-lowering pharmaceuticals. Therefore, understanding modulators of disease severity will aid in targeted therapies for PEXG. Genome-wide association studies have identified polymorphisms in the long non-coding RNA lysyl oxidase-like 1-antisense 1 (LOXL1-AS1) as a risk factor for PEXG. Risk alleles, oxidative stress and mechanical stretch all alter LOXL1-AS1 expression. As a long non-coding RNA, LOXL1-AS1 binds hnRNPL and regulates global gene expression. In this study, we focus on the role of LOXL1-AS1 in the ocular cells (trabecular meshwork and Schlemm's canal) that regulate IOP. We show that selective knockdown of LOXL1-AS1 leads to cell-type-specific changes in gene expression, ECM homeostasis, signaling and morphology. These results implicate LOXL1-AS1 as a modulator of cellular homeostasis, altering cell contractility and ECM turnover, both of which are well-known contributors to PEXG. These findings support LOXL1-AS1 as a key target for modifying the disease.

Losing, preserving, and restoring vision from neurodegeneration in the eye

The retina is a part of the brain that sits at the back of the eye, looking out onto the world. The first neurons of the retina are the rod and cone photoreceptors, which convert changes in photon flux into electrical signals that are the basis of vision. Rods and cones are frequent targets of heritable neurodegenerative diseases that cause visual impairment, including blindness, in millions of people worldwide. This review summarizes the diverse genetic causes of inherited retinal degenerations (IRDs) and their convergence onto common pathogenic mechanisms of vision loss. Currently, there are few effective treatments for IRDs, but recent advances in disparate areas of biology and technology (e.g., genome editing, viral engineering, 3D organoids, optogenetics, semiconductor arrays) discussed here enable promising efforts to preserve and restore vision in IRD patients with implications for neurodegeneration in less approachable brain areas.

The effect of GelDex-S58 hydrogel on anti-conjunctival scarring after glaucoma filtration surgery

Excessive scarring is the main cause of surgical failure in glaucoma filtration surgery. S58 has been shown to have an excellent antifibrotic effect but its duration of action is not sufficient to achieve the desired antiscarring effect. In this study, a light-cured bioadhesive hydrogel composed of GelMA and oxidized dextran (ODex), namely, GelDex, was used to load S58 (GelDex-S58). The microscopic morphology of GelDex-S58 appeared to be a porous structure with good slow-release properties and suitable degradation time. Cell Counting Kit-8, cell scratch and transwell assays showed that GelDex-S58 significantly reduced TGF-β-induced fibroblast proliferation, increased migration and invasion ability. In in vivo studies, GelDex-S58 treatment prolonged follicular retention, reduced mean intraocular pressure, and significantly reduced collagen deposition and α-SMA expression levels in the conjunctival tissue compared to treatment with S58 alone. In conclusion, GelDex-S58 could reduce scar formation after glaucoma filtration surgery.

Phenotypic and Genetic Links between Body Fat Measurements and Primary Open-Angle Glaucoma

The phenotypic and genetic links between body fat phenotypes and primary open-angle glaucoma (POAG) are unclear. We conducted a meta-analysis of relevant longitudinal epidemiological studies to evaluate the phenotypic link. To identify genetic links, we performed genetic correlation analysis and pleiotropy analysis of genome-wide association study summary statistics datasets of POAG, intraocular pressure (IOP), vertical cup-to-disc ratio, obesity, body mass index (BMI), and waist-to-hip ratio. In the meta-analysis, we first established that obese and underweight populations have a significantly higher risk of POAG using longitudinal data. We also discovered positive genetic correlations between POAG and BMI and obesity phenotypes. Finally, we identified over 20 genomic loci jointly associated with POAG/IOP and BMI. Among them, the genes loci CADM2, RP3-335N17.2, RP11-793K1.1, RPS17P5, and CASC20 showed the lowest false discovery rate. These findings support the connection between body fat phenotypes and POAG. The newly identified genomic loci and genes render further functional investigation.