Enhanced Optic Nerve Expansion and Altered Ultrastructure of Elastic Fibers Induced by Lysyl Oxidase Inhibition in a Mouse Model of Marfan Syndrome

Two major constituents of exfoliation material, fibrillin-1 and lysyl oxidase-like 1 (encoded by FBN1 and LOXL1), are implicated in exfoliation glaucoma, yet their individual contributions to ocular phenotype are minor. To test the hypothesis that a combination of FBN1 mutation and LOXL1 deficiency exacerbates ocular phenotypes, the pan-LOX inhibitor β-aminopropionitrile (BAPN) was used to treat adult wild-type (WT) and Fbn1C1041G/+ mice for 8 weeks and their eyes were examined. Although intraocular pressure did not change and exfoliation material was not detected in the eyes, BAPN treatment worsened optic nerve and axon expansion in Fbn1C1041G/+ mice, an early sign of axonal damage in rodent models of glaucoma. Disruption of elastic fibers was detected only in Fbn1C1041G/+ mice, which increased with BAPN treatment, as shown by histologic and immunohistochemical staining of the optic nerve pia mater. Transmission electron microscopy showed that Fbn1C1041G/+ mice had fewer microfibrils, smaller elastin cores, and a lower density of elastic fibers compared with WT mice in control groups. BAPN treatment led to elastin core expansion in both WT and Fbn1C1041G/+ mice, but an increase in the density of elastic fiber was confined to Fbn1C1041G/+ mice. LOX inhibition had a stronger effect on optic nerve and elastic fiber parameters in the context of Fbn1 mutation, indicating the Marfan mouse model with LOX inhibition warrants further investigation for exfoliation glaucoma pathogenesis.

Compound Heterozygous LTBP2 Mutations Associated With Juvenile-Onset Open-Angle Glaucoma and Marfan-Like Phenotype

This case report describes a patient diagnosed at age 13 years with glaucoma who later presented with elevated intraocular pressure, severe cupping, open iridocorneal angle, and lens dislocation.

Optic neuropathy associated with TGFβ dysregulation in mice with a glaucoma-causative mutation of ADAMTS10

Glaucoma is a neurodegenerative disease that causes irreversible blindness due to loss of retinal ganglion cells (RGCs) and their axons. We previously identified a G661R mutation of ADAMTS10 (A Disintegrin And Metalloproteinase with ThromboSpondin type 1 motif 10) as the disease-causing mutation in a beagle model of glaucoma. ADAMTS10 is a secreted matrix metalloproteinase that belongs to the ADAMTS family which is involved in extracellular matrix (ECM) turnover. Previous studies have shown that ADAMTS10 binds fibrillin microfibrils, promotes their formation, and influences their fibrillin isoform composition. Here, we established a mouse model carrying the G661R mutation of ADAMTS10 (ADAMTS10G661R/G661R) to investigate its ocular phenotypes related to glaucoma and to explore possible functions of ADAMTS10. We found that ADAMTS10 was expressed in the inner retina and along RGC axons in the optic nerve. However, ADAMTS10 was not colocalized with fibrillin microfibrils in these tissues, suggesting fibrillin-independent function for ADAMTS10. In electroretinogram experiments, we found that ADAMTS10G661R/G661R mice had reduced amplitude of retinal responses to dim light stimulus, indicating RGC dysfunction. The reduced RGC function coincided with RGC axon structural changes manifested as smaller optic nerves and fewer optic nerve axons, which may contribute to glaucoma. The reduced number of optic nerve axons found for ADAMTS10G661R/G661R mice occurred early, suggesting developmental deficits. Subsequent experiments found increased apoptosis in the retina of ADAMTS10G661R/G661R mice during postnatal development, which could result in fewer RGCs produced, accounting for fewer optic nerve axons in adulthood. Consistent with a protective effect of transforming growth factor β (TGFβ) signaling against apoptosis during retinal development as shown previously by others, we found increased apoptosis accompanied by decreased TGFβ signaling in the developing retina of ADAMTS10G661R/G661R mice, suggesting a novel role for ADAMTS10 in regulating TGFβ signaling which could involve direct interaction between ADAMTS10 and latent TGFβ.

Adamts10 controls transforming growth factor β family signaling that contributes to retinal ganglion cell development

Although mutations in ADAMTS10 have long been known to cause autosomal recessive Weill-Marchesani Syndrome which is characterized by short stature and ocular abnormalities, more recent work has shown that certain mutations in ADAMTS10 cause glaucoma in dogs. In humans, glaucoma is the leading cause of irreversible vision loss that affects tens of millions of people world-wide. Vision loss in glaucoma is a result of neurodegeneration of retinal ganglion cells that form the inner-most layer of the retina and whose axons form the optic nerve which relays visual information to the brain. ADAMTS10 contributes to the formation of microfibrils which sequester latent transforming growth factor β (TGFβ). Among its many biological functions, TGFβ promotes the development of retinal ganglion cells and is also known to play other roles in glaucoma pathogenesis. The aim of this study was to test the hypothesis that ADAMTS10 plays a role in retinal ganglion cell development through regulation of TGFβ signaling. To this end, Adamts10 expression was targeted for reduction in zebrafish embryos carrying either a fluorescent reporter that labels retinal ganglion cells, or a fluorescent reporter of pSmad3-mediated TGFβ family signaling. Loss of adamts10 function in zebrafish embryos reduced retinal ganglion cell reporter fluorescence and prevented formation of an ordered retinal ganglion cell layer. Targeting adamts10 expression also drastically reduced constitutive TGFβ signaling in the eye. Direct inhibition of the TGFβ receptor reduced retinal ganglion cell reporter fluorescence similar to the effect of targeting adamts10 expression. These findings unveil a previously unknown role for Adamts10 in retinal ganglion cell development and suggest that the developmental role of Adamts10 is mediated by active TGFβ family signaling. In addition, our results show for the first time that Adamts10 is necessary for pSmad3-mediated constitutive TGFβ family signaling.

Facilitators and Barriers to Glaucoma Medication Adherence

PRCIS

Patient education and dosing self-efficacy are important factors related to ongoing adherence to glaucoma topical treatment, and patients view their disease management as a shared effort with their provider.

PURPOSE

Glaucoma affects nearly 3 million Americans, and medication adherence has been reported to be as low as 20% in this patient population; however, key limitations to our understanding of this behavior in adults with glaucoma exist.

PATIENTS AND METHODS

This research used an electronic survey including validated concepts related to topical medication use and an in-person interview to investigate the influencers of and solutions for challenges to medication adherence in adults with glaucoma. Patient eligibility was determined upon arrival to a regularly-scheduled visit to the Vanderbilt Eye Institute, during which they were asked for consent to complete the survey. Responses were captured by tablet and assessed using descriptive and inferential statistics. The primary focus was instrument correlations with the Adherence to Refills and Medications Scale score and were run between Adherence to Refills and Medications Scale, and the totaled score for each individual questionnaire as well as individual items. Recorded interviews were thematically assessed by multiple study team members.

RESULTS

Survey results of adults with glaucoma suggested that self-efficacy, forgetfulness, fear of side effects, and dosing ability were all related to self-reported medication adherence. Despite most having glaucoma for several years, discrepancies in disease knowledge were observed. Patient interviews uncovered 3 overall themes related to glaucoma treatment: (1) glaucoma management as a shared responsibility; (2) the importance of patient education; and (3) specific adherence facilitators and barriers.

CONCLUSION

Glaucoma medication adherence interventions may benefit from focusing on developing patient medication-taking self-efficacy, disease-related education, and engagement with their provider.

Altered Ocular Fibrillin Microfibril Composition in Mice With a Glaucoma-Causing Mutation of Adamts10

Purpose

Previously, we identified a G661R mutation of ADAMTS10 (a disintegrin-like and metalloprotease with thrombospondin type 1 motif 10) as being disease causative in a colony of Beagles with inherited primary open-angle glaucoma (POAG). Mutations in ADAMTS10 are known to cause Weill-Marchesani syndrome (WMS), which is also caused by mutations in the fibrillin-1 gene (FBN1), suggesting functional linkage between ADAMTS10 and fibrillin-1, the principal component of microfibrils. Here, we established a mouse line with the G661R mutation of Adamts10 (Adamts10G661R/G661R) to determine if they develop features of WMS and alterations of ocular fibrillin microfibrils.

Methods

Intraocular pressure (IOP) was measured using a TonoLab rebound tonometer. Central cornea thickness (CCT), anterior chamber depth (ACD) and axial length (AL) of the eye were examined by spectral-domain optical coherence tomography. Sagittal eye sections from mice at postnatal day 10 (P10) and at 3 and 24 months of age were stained with antibodies against fibrillin-1, fibrillin-2, and ADAMTS10.

Results

IOP was not elevated in Adamts10G661R/G661R mice. Adamts10G661R/G661R mice had smaller bodies, thicker CCT, and shallower ACD compared to wild-type mice but normal AL. Adamts10G661R/G661R mice displayed persistent fibrillin-2 and enhanced fibrillin-1 immunofluorescence in the lens zonules and in the hyaloid vasculature and its remnants in the vitreous.

Conclusions

Adamts10G661R/G661R mice recapitulate the short stature and ocular phenotypes of WMS. The altered fibrillin-1 and fibrillin-2 immunoactivity in Adamts10G661R/G661R mice suggests that the G661R mutation of Adamts10 perturbs regulation of the fibrillin isotype composition of microfibrils in the mouse eye.

Increased Susceptibility to Glaucomatous Damage in Microfibril Deficient Mice

Purpose

To test whether mice with microfibril deficiency due to the Tsk mutation of fibrillin-1 (Fbn1Tsk/+) have increased susceptibility to pressure-induced retinal ganglion cell (RGC) degeneration.

Methods

Intraocular pressure (IOP) elevation was induced in Fbn1Tsk/+ and wild type (wt) mice by injecting microbeads into the anterior chamber. Mice were then followed up for four months, with IOP measurements every three to six days. Retinas were stained for Brn3a to determine RGC number. Optic nerve cross-sections were stained with p-phenylene diamine to determine nerve area, axon number, and caliber and thickness of the pia mater.

Results

Microbead injection induced significant IOP elevation that was significantly less for Fbn1Tsk/+ mice compared with wt. The optic nerves and optic nerve axons were larger, and the elastic fiber-rich pia mater was thinner in Fbn1Tsk/+ mice. Microbead injection resulted in reduced optic nerve size, thicker pia mater, and a slight decrease in axon size. Fbn1Tsk/+ mice had significantly greater loss of RGCs and optic nerve axons compared with wt (14.8% vs. 5.8%, P = 0.002, and 17.0% vs. 7.5%, P = 0.002, respectively).

Conclusions

Fbn1Tsk/+mice had altered optic nerve structure as indicated by larger optic nerves, larger optic nerve axons and thinner pia mater, consistent with our previous findings. Despite lower IOP elevation, Fbn1Tsk/+mice had greater loss of RGCs and optic nerve axons, suggesting increased susceptibility to IOP-induced optic nerve degeneration in microfibril-deficient mice.

Telmisartan Reduces Axon Degeneration in Mice With Experimental Glaucoma

Purpose

The purpose of this study was to determine if treatment with telmisartan, an angiotensin II type 1 receptor blocker (ARB), protects against retinal ganglion cell (RGC) degeneration in a mouse glaucoma model with induced elevation of intraocular pressure (IOP).

Methods

IOP elevation was induced by injection of polystyrene microbeads into the anterior chamber of the right eye of 3-month-old C57BL/6J mice, with the left eye serving as contralateral control. Starting the day of microbead injection, mice were maintained on solid food pellets with or without incorporated telmisartan. IOP was measured by Tono Lab tonometry prior to and weekly after microbead injection. Twelve weeks postinjection, mice were euthanized to obtain optic nerves for analysis of RGC axons. The total numbers of optic nerve axons were determined manually and automatedly using AxonJ. Degenerating axons were counted manually.

Results

IOP elevation induced by microbead injection was similar in magnitude and duration in vehicle and telmisartan-fed mice, although IOP was reduced 5.8% in uninjected mice treated with telmisartan (P = 0.0027). Axon loss determined by manual and automated methods was greater in vehicle compared to telmisartan-treated mice (manual: 9.5% vs. 1.8%, P = 0.044; automated: 14.2% vs. 2.9%, P = 0.0375). An increase in the percent of axons undergoing degeneration was observed in nerves from microbead-injected eyes that was greater in vehicle-treated compared to telmisartan-treated mice (49.0% vs. –0.58%, P = 0.0019).

Conclusions

Elevation of IOP by microbead injection led to loss of RGC axons in vehicle-treated mice that was largely prevented by telmisartan treatment, suggesting a neuroprotective effect of telmisartan.

Association of Genetic Variants With Primary Open-Angle Glaucoma Among Individuals With African Ancestry

IMPORTANCE

Primary open-angle glaucoma presents with increased prevalence and a higher degree of clinical severity in populations of African ancestry compared with European or Asian ancestry. Despite this, individuals of African ancestry remain understudied in genomic research for blinding disorders.

OBJECTIVES

To perform a genome-wide association study (GWAS) of African ancestry populations and evaluate potential mechanisms of pathogenesis for loci associated with primary open-angle glaucoma.

DESIGN, SETTINGS, AND PARTICIPANTS

A 2-stage GWAS with a discovery data set of 2320 individuals with primary open-angle glaucoma and 2121 control individuals without primary open-angle glaucoma. The validation stage included an additional 6937 affected individuals and 14 917 unaffected individuals using multicenter clinic- and population-based participant recruitment approaches. Study participants were recruited from Ghana, Nigeria, South Africa, the United States, Tanzania, Britain, Cameroon, Saudi Arabia, Brazil, the Democratic Republic of the Congo, Morocco, Peru, and Mali from 2003 to 2018. Individuals with primary open-angle glaucoma had open iridocorneal angles and displayed glaucomatous optic neuropathy with visual field defects. Elevated intraocular pressure was not included in the case definition. Control individuals had no elevated intraocular pressure and no signs of glaucoma.

EXPOSURES

Genetic variants associated with primary open-angle glaucoma.

MAIN OUTCOMES AND MEASURES

Presence of primary open-angle glaucoma. Genome-wide significance was defined as P < 5 × 10-8 in the discovery stage and in the meta-analysis of combined discovery and validation data.

RESULTS

A total of 2320 individuals with primary open-angle glaucoma (mean [interquartile range] age, 64.6 [56-74] years; 1055 [45.5%] women) and 2121 individuals without primary open-angle glaucoma (mean [interquartile range] age, 63.4 [55-71] years; 1025 [48.3%] women) were included in the discovery GWAS. The GWAS discovery meta-analysis demonstrated association of variants at amyloid-β A4 precursor protein-binding family B member 2 (APBB2; chromosome 4, rs59892895T>C) with primary open-angle glaucoma (odds ratio [OR], 1.32 [95% CI, 1.20-1.46]; P = 2 × 10-8). The association was validated in an analysis of an additional 6937 affected individuals and 14 917 unaffected individuals (OR, 1.15 [95% CI, 1.09-1.21]; P < .001). Each copy of the rs59892895*C risk allele was associated with increased risk of primary open-angle glaucoma when all data were included in a meta-analysis (OR, 1.19 [95% CI, 1.14-1.25]; P = 4 × 10-13). The rs59892895*C risk allele was present at appreciable frequency only in African ancestry populations. In contrast, the rs59892895*C risk allele had a frequency of less than 0.1% in individuals of European or Asian ancestry.

CONCLUSIONS AND RELEVANCE

In this genome-wide association study, variants at the APBB2 locus demonstrated differential association with primary open-angle glaucoma by ancestry. If validated in additional populations this finding may have implications for risk assessment and therapeutic strategies.

Three-Year Findings on Intraocular Pressure Changes in The Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) Study

BACKGROUND AND OBJECTIVE

This paper reports 3-year intraocular pressure (IOP) outcomes of the Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study.

PATIENTS AND METHODS

The prospective, controlled, observational study included 80 eyes of 40 participants undergoing routine pars plana vitrectomy. Study patients underwent preoperative evaluation and multimodal testing of the study (surgical) and fellow (control) eye. This testing was repeated at 3 months postoperatively and then annually for 3 years.

RESULTS

Thirty-two of 40 patients (80%) completed 3-year follow-up. At 3 years postoperatively, there was no difference in IOP measurements in surgical eyes overall from baseline (P = .36). Subgroup analysis of pseudophakic eyes at baseline showed a significant elevation in IOP from 14.3 mm Hg ± 2.9 mm Hg at baseline to 16.8 mm Hg ± 3.2 mm Hg at 3-year follow-up (P < .029). Fellow eyes did not experience a significant change from baseline.

CONCLUSION

The authors' 3-year results show that IOP is consistently and significantly elevated in pseudophakic eyes compared to baseline following routine vitrectomy. [Ophthalmic Surg Lasers Imaging Retina. 2019;50:371-376.].

Differential effects of angiotensin II type I receptor blockers on reducing intraocular pressure and TGFβ signaling in the mouse retina

PURPOSE

Angiotensin II type 1 receptor blockers (ARBs) have been investigated for their neuroprotective and intraocular pressure (IOP) lowering effects in treating glaucoma, but the reports have been inconsistent possibly because different compounds and models have been used. Here we selected three ARBs for head-to-head comparisons of their effects on IOP and transforming growth factor β (TGFβ) signaling, which is believed to play an important role in glaucoma pathogenesis.

METHODS

Three ARBs (losartan, irbesartan or telmisartan) or vehicle controls were administered via chow to C57BL/6J mice for up to 7 days. Drug concentrations in the eye, brain, and plasma were evaluated by liquid chromatography mass spectrometry. Cohorts of mice were randomly assigned to different treatments. IOP and blood pressure were measured before and after ARB treatment. Effects of ARBs on TGFβ signaling in the retina were evaluated by phosphorylated Smad2 (pSmad2) immunohistochemistry.

RESULTS

Physiologically relevant concentrations of losartan, irbesartan and telmisartan were detected in eye, brain and plasma after drug administration (n = 11 mice/treatment). Blood pressure was significantly reduced by all ARBs compared to vehicle-fed controls (all p-values < 0.001, n = 8-15 mice/treatment). Compared to vehicle control, IOP was significantly reduced by irbesartan (p = 0.030) and telmisartan (p = 0.019), but not by losartan (n = 14-17 mice/treatment). Constitutive pSmad2 fluorescence observed in retinal ganglion cells was significantly reduced by telmisartan (p = 0.034), but not by losartan or irbesartan (n = 3-4 mice/treatment).

CONCLUSIONS

Administration via chow is an effective delivery method for ARBs, as evidenced by lowered blood pressure. ARBs vary in their abilities to lower IOP or reduce TGFβ signaling. Considering the significant roles of IOP and TGFβ in glaucoma pathogenesis, specific ARBs with dual effects, such as telmisartan, may be more effective than other ARBs for treating glaucoma.

Differentially expressed microRNAs in the aqueous humor of patients with exfoliation glaucoma or primary open-angle glaucoma

Both exfoliation glaucoma (XFG) and primary open-angle glaucoma (POAG) have been linked to decreased conventional outflow of aqueous humor (AH). To better understand the molecular changes in the AH content under such conditions, we analyzed the miRNA profiles of AH samples from patients with POAG and XFG compared to non-glaucoma controls. Individual AH samples (n = 76) were collected from POAG and XFG patients and age-matched controls during surgical procedure. After RNA extraction, the miRNA profiles were individually determined in 12 POAG, 12 XFG and 11 control samples. We identified 205, 295 and 195 miRNAs in the POAG, XFG and control samples, respectively. Our differential expression analysis identified three miRNAs (miR-125b-5p, miR-302d-3p and miR-451a) significantly different between POAG and controls, five miRNAs (miR-122-5p, miR-3144-3p, miR-320a, miR-320e and miR-630) between XFG and controls and one miRNA (miR-302d-3p) between POAG and XFG. While none of these miRNAs have been previously linked to glaucoma, miR-122-5p may target three glaucoma-associated genes: OPTN, TMCO1 and TGF-ß1. Pathway analysis revealed that these miRNAs are involved in potential glaucoma pathways, including focal adhesion, tight junctions, and TGF-ß signaling. Comparison of the miRNA profile in AH to unrelated human serum (n = 12) exposed potential relationships between these two fluids, although they were not significantly correlated. In summary, we have successfully profiled the miRNA expression without amplification in individual human AH samples and identified several POAG or XFG-associated miRNAs. These miRNAs may play a role in pathways previously implicated in glaucoma and act as biomarkers for disease pathogenesis.

Consensus recommendations for trabecular meshwork cell isolation, characterization and culture

Cultured trabecular meshwork (TM) cells are a valuable model system to study the cellular mechanisms involved in the regulation of conventional outflow resistance and thus intraocular pressure; and their dysfunction resulting in ocular hypertension. In this review, we describe the standard procedures used for the isolation of TM cells from several animal species including humans, and the methods used to validate their identity. Having a set of standard practices for TM cells will increase the scientific rigor when used as a model, and enable other researchers to replicate and build upon previous findings.

Genetic association study of exfoliation syndrome identifies a protective rare variant at LOXL1 and five new susceptibility loci

Exfoliation syndrome (XFS) is the most common known risk factor for secondary glaucoma and a major cause of blindness worldwide. Variants in two genes, LOXL1 and CACNA1A, have previously been associated with XFS. To further elucidate the genetic basis of XFS, we collected a global sample of XFS cases to refine the association at LOXL1, which previously showed inconsistent results across populations, and to identify new variants associated with XFS. We identified a rare protective allele at LOXL1 (p.Phe407, odds ratio (OR) = 25, P = 2.9 × 10^-14) through deep resequencing of XFS cases and controls from nine countries. A genome-wide association study (GWAS) of XFS cases and controls from 24 countries followed by replication in 18 countries identified seven genome-wide significant loci (P < 5 × 10^-8). We identified association signals at 13q12 (POMP), 11q23.3 (TMEM136), 6p21 (AGPAT1), 3p24 (RBMS3) and 5q23 (near SEMA6A). These findings provide biological insights into the pathology of XFS and highlight a potential role for naturally occurring rare LOXL1 variants in disease biology.

A Common Variant in MIR182 Is Associated With Primary Open-Angle Glaucoma in the NEIGHBORHOOD Consortium

Purpose

Noncoding microRNAs (miRNAs) have been implicated in the pathogenesis of glaucoma. We aimed to identify common variants in miRNA coding genes (MIR) associated with primary open-angle glaucoma (POAG).

Methods

Using the NEIGHBORHOOD data set (3853 cases/33,480 controls with European ancestry), we first assessed the relation between 85 variants in 76 MIR genes and overall POAG. Subtype-specific analyses were performed in high-tension glaucoma (HTG) and normal-tension glaucoma subsets. Second, we examined the expression of miR-182, which was associated with POAG, in postmortem human ocular tissues (ciliary body, cornea, retina, and trabecular meshwork [TM]), using miRNA sequencing (miRNA-Seq) and droplet digital PCR (ddPCR). Third, miR-182 expression was also examined in human aqueous humor (AH) by using miRNA-Seq. Fourth, exosomes secreted from primary human TM cells were examined for miR-182 expression by using miRNA-Seq. Fifth, using ddPCR we compared miR-182 expression in AH between five HTG cases and five controls.

Results

Only rs76481776 in MIR182 gene was associated with POAG after adjustment for multiple comparisons (odds ratio [OR] = 1.23, 95% confidence interval [CI]: 1.11–1.42, P = 0.0002). Subtype analysis indicated that the association was primarily in the HTG subset (OR = 1.26, 95% CI: 1.08–1.47, P = 0.004). The risk allele T has been associated with elevated miR-182 expression in vitro. Data from ddPCR and miRNA-Seq confirmed miR-182 expression in all examined ocular tissues and TM-derived exosomes. Interestingly, miR-182 expression in AH was 2-fold higher in HTG patients than nonglaucoma controls (P = 0.03) without controlling for medication treatment.

Conclusions

Our integrative study is the first to associate rs76481776 with POAG via elevated miR-182 expression.

Genetics, Diagnosis, and Monitoring of Pseudoexfoliation Glaucoma

Recent studies have shed new light on the genetic factors underlying pseudoexfoliation syndrome, growing our understanding of the role of the lysyl oxidase-like 1 (LOXL1) gene and its various polymorphisms as well as identifying new genetic associations. Recent years have brought new insight on how these genetic factors interact with other factors, including environmental, to confer risk to individuals and populations worldwide. All of these findings may hold importance to the screening, diagnosis, and monitoring of pseudoexfoliation and may also help lead to the identification of novel therapeutic targets. This review serves as an update on the recent trends and findings in pseudoexfoliation syndrome.

Severe open angle glaucoma in hereditary hemorrhagic telangiectasia

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant disease. Conjunctival telangiectasias and retinal vascular malformations are known ocular manifestations. We report here the first case of open angle glaucoma in a patient with HHT caused by a nonsense mutation, C471X in the ACVRL1 gene.

Metabolome-Wide Association Study of Primary Open Angle Glaucoma

PURPOSE

To determine if primary open-angle glaucoma (POAG) patients can be differentiated from controls based on metabolic characteristics.

METHODS

We used ultra-high resolution mass spectrometry with C18 liquid chromatography for metabolomic analysis on frozen plasma samples from 72 POAG patients and 72 controls. Metabolome-wide Spearman correlation was performed to select differentially expressed metabolites (DEM) correlated with POAG. We corrected P values for multiple testing using Benjamini and Hochberg false discovery rate (FDR). Hierarchical cluster analysis (HCA) was used to depict the relationship between participants and DEM. Differentially expressed metabolites were matched to the METLIN metabolomics database; both DEM and metabolites significantly correlating with DEM were analyzed using MetaboAnalyst to identify metabolic pathways altered in POAG.

RESULTS

Of the 2440 m/z (mass/charge) features recovered after filtering, 41 differed between POAG cases and controls at FDR = 0.05. Hierarchical cluster analysis revealed these DEM to associate into eight clusters; three of these clusters contained the majority of the DEM and included palmitoylcarnitine, hydroxyergocalciferol, and high-resolution METLIN matches to sphingolipids, other vitamin D-related metabolites, and terpenes. MetaboAnalyst also indicated likely alteration in steroid biosynthesis pathways.

CONCLUSIONS

Global ultrahigh resolution metabolomics emphasized the importance of altered lipid metabolism in POAG. The results suggest specific metabolic processes, such as those involving palmitoylcarnitine, sphingolipids, vitamin D-related compounds, and steroid precursors, may contribute to POAG status and merit more detailed study with targeted methods.

Elevated transforming growth factor β1 in plasma of primary open-angle glaucoma patients

PURPOSE

To test the hypothesis that primary open-angle glaucoma (POAG) patients have a systemic elevation of transforming growth factor β1 (TGFβ1).

METHODS

Plasma was prepared from blood samples drawn from patients of the Vanderbilt Eye Institute during clinic visits. Concentrations of total TGFβ1 and thrombospondin-1 (TSP1) in plasma were determined by ELISA. Statistical significance of differences between POAG and control samples was evaluated by Mann-Whitney test. Regression analysis was used to evaluate correlations between plasma TGFβ1 and patient age and between plasma TGFβ1 and TSP1.

RESULTS

Plasma samples were obtained from 148 POAG patients and 150 controls. Concentration of total TGFβ1 in the plasma of POAG patients (median = 3.25 ng/mL) was significantly higher (P < 0.0001) than in controls (median = 2.46 ng/mL). Plasma TGFβ1 was not correlated with age of patient (P = 0.17). Thrombospondin-1 concentration was also significantly higher (P < 0.0001) in POAG patients (median = 0.774 μg/mL) as compared to controls (median = 0.567 μg/mL). Plasma total TGFβ1 and TSP1 concentrations were linearly correlated (P < 0.0001).

CONCLUSIONS

Plasma samples from POAG patients display elevated total TGFβ1 compared to controls, consistent with elevated systemic TGFβ1 in POAG patients.

Acute myopia and angle closure glaucoma from topiramate in a seven-year-old: a case report and review of the literature

Background

A case is reported of acute bilateral myopia and angle closure glaucoma in a 7-year-old patient from topiramate toxicity. This is the second known reported case of topiramate induced acute angle closure glaucoma and third known reported case of topiramate induced acute myopia in a pediatric patient.

Case presentation

This case presents a 7-year-old who had recently begun topiramate therapy for seizures and headache. She developed painless blurred vision and acute bilateral myopia, which progressed to acute bilateral angle closure glaucoma. After a routine eye exam where myopia was diagnosed, the patient presented to the emergency room with symptoms of acute onset blurry vision, tearing, red eyes, swollen eyelids, and photophobia. The symptoms, myopia, and angle closure resolved with topical and oral intraocular pressure lowering medications, topical cyclopentolate, and discontinuation of topiramate.

Conclusion

Acute angle closure glaucoma is a well-known side effect of topiramate, but is rarely seen in children. It cautions providers to the potential ophthalmic side effects of commonly used medications in the pediatric population. It highlights the need to keep a broad differential in mind when encountering sudden onset blurry vision in the primary care clinic, the need for careful consideration of side effects when starting topiramate therapy in a child, and the need for parental counseling of side effects.

The microfibril hypothesis of glaucoma: implications for treatment of elevated intraocular pressure

Microfibrils are macromolecular aggregates located in the extracellular matrix of both elastic and nonelastic tissues that have essential functions in formation of elastic fibers and control of signaling through the transforming growth factor beta (TGFβ) family of cytokines. Elevation of systemic TGFβ and chronic activation of TGFβ signal transduction are associated with diseases caused by mutations in microfibril-associated genes, including FBN1. A role for microfibrils in glaucoma is suggested by identification of risk alleles in LOXL1 for exfoliation glaucoma and mutations in LTBP2 for primary congenital glaucoma, both of which are microfibril-associated genes. Recent identification of a mutation in another microfibril-associated gene, ADAMTS10, in a dog model of primary open-angle glaucoma led us to form the microfibril hypothesis of glaucoma, which in general states that defective microfibrils may be an underlying cause of glaucoma. Microfibril defects could contribute to glaucoma through alterations in biomechanical properties of tissue and/or through effects on signaling through TGFβ, which is well established to be elevated in the aqueous humor of glaucoma patients. Recent work has shown that diseases caused by microfibril defects are associated with increased concentrations of TGFβ protein and chronic activation of TGFβ-mediated signal transduction. In analogy with other microfibril-related diseases, defective microfibrils could provide a mechanism for the elevation of TGFβ2 in glaucomatous aqueous humor. If glaucoma shares mechanisms with other diseases caused by defective microfibrils, such as Marfan syndrome, therapeutic interventions to inhibit chronic activation of TGFβ signaling used in those diseases may be applied to glaucoma.

Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study: findings at 3 months

Background

The purpose of this paper is to report the 3-month findings of the Prospective Retinal and Optic Nerve Vitrectomy Evaluation (PROVE) study.

Methods

Eighty eyes of 40 participants undergoing vitrectomy were enrolled. Participants underwent baseline evaluation of the study (surgical) and fellow (control) eye that included: intraocular pressure, central corneal thickness, gonioscopy, cup-to-disc ratio measurement, color fundus and optic disc photography, automated perimetry, and optical coherence tomography of the macula and optic nerve. Evaluation was repeated at 3 months. Main outcome measures were changes in macula and retinal nerve fiber layer (RNFL) thickness and intraocular pressure.

Results

All participants completed follow-up. Mean cup-to-disc ratio of study and fellow eyes at baseline was 0.43 ± 0.2 and 0.46 ± 0.2, respectively, and 13% of participants had undiagnosed narrow angles. There was no significant change in intraocular pressure, cup-to-disc ratio, or pattern standard deviation in study eyes compared with baseline or fellow eyes at 3 months. Vision improved in all study eyes at 3 months compared with baseline (P = 0.013), but remained significantly worse than fellow eyes (P < 0.001). Central subfield and temporal peripapillary RNFL thickness were significantly greater in eyes with epiretinal membrane (P < 0.05), and resolution after surgery correlated with visual improvement (P < 0.05).

Conclusion

The 3-month results do not indicate any increased risk for open-angle glaucoma but suggest that a relatively high percentage of eyes may be at risk of angle closure glaucoma. Temporal RNFL thickness and central subfield were increased in eyes with epiretinal membrane, and resolution correlated with degree of visual recovery.

A de novo MYOC mutation detected in juvenile open angle glaucoma associated with reduced myocilin protein in aqueous humor

MYOC mutations were originally identified in patients with juvenile open angle glaucoma (JOAG). Cell culture and mouse studies suggest that MYOC mutations cause glaucoma through a dominant-negative effect on myocilin protein secretion. We tested this hypothesis with patient samples in this study. Glaucoma and control patients underwent complete ocular examination. DNA samples from glaucoma patients, unaffected relatives and controls were used for DNA sequencing of MYOC. Aqueous humor (AH) samples from glaucoma and control patients were obtained at the time of surgery. Myocilin protein in AH was detected by quantitative Western blot analysis. A de novo Val251Ala mutation of MYOC was found to segregate with disease in a family with autosomal dominant JOAG. Myocilin protein was detected in all control AH samples but was nearly undetectable in AH samples from a patient heterozygous for the Val251Ala mutation. Our results using human patient samples are consistent with a dominant-negative effect of pathogenic MYOC mutations on myocilin secretion.

Screening ADAMTS10 in dog populations supports Gly661Arg as the glaucoma-causing variant in beagles

PURPOSE

Previously, we mapped the disease locus in the beagle model of autosomal recessive primary open angle glaucoma (POAG) to a 4-Mb interval on chromosome 20, and identified a Gly661Arg variant in ADAMTS10 as the candidate disease-causing variant. The purpose of this study was to test the hypothesis that the Gly661Arg variant of ADAMTS10 causes glaucoma by genotyping dogs of various breeds affected and unaffected by primary glaucoma.

METHODS

Dogs of various breeds, affected or unaffected with primary glaucoma, were genotyped for the Gly661Arg variant of ADAMTS10, as well as 7 other nonsynonymous single nucleotide polymorphisms (SNPs) in other genes in the beagle POAG locus that segregate with disease. Alternate allele frequencies were calculated with 95% confidence intervals and comparisons made to expected allele frequency relative to disease prevalence or between cases and controls.

RESULTS

For the nonsynonymous SNPs other than the ADAMTS10 variant, control dogs were identified that were homozygous for the alternative alleles, ruling out those variants as causative. None of the nonsynonymous SNPs were found associated with primary glaucoma in American cocker spaniels. The Gly661Arg variant of ADAMTS10 was the only variant with minor allele frequency consistent with the prevalence of primary glaucoma in the general beagle population. The only dog found homozygous for the Gly661Arg variant of ADAMTS10 was an affected beagle, unrelated to the POAG colony.

CONCLUSIONS

These findings support the Gly661Arg mutation of ADAMTS10 as the likely cause of POAG in beagles.

Marfan syndrome caused by a novel FBN1 mutation with associated pigmentary glaucoma

Mutations in fibrillin-1 (FBN1) cause a wide spectrum of disorders, including Marfan syndrome, which have in common defects in fibrillin-1 microfibrils. Ectopia lentis and myopia are frequently observed ocular manifestations of Marfan syndrome. Glaucoma is also associated with Marfan syndrome, though the form of glaucoma has not been well-characterized. In this report, ocular examination of a patient diagnosed with Marfan syndrome based on family history and aortic dilatation was performed, including measurement of facility of aqueous humor outflow by tonography. The patient did not have ectopia lentis at the age of 42 years. Based on optic nerve appearance, reduced outflow facility, elevated IOP with open angles and clear signs of pigment dispersion, the patient was diagnosed with pigmentary glaucoma. The patient was heterozygous for a novel truncating mutation in FBN1, p.Leu72Ter. Histology of normal human eyes revealed abundant expression of elastic fibers and fibrillin-1 in aqueous humor outflow structures. This is the first report of a patient with Marfan syndrome that is caused by a confirmed FBN1 mutation with associated pigmentary glaucoma. In addition to identifying a novel mutation of FBN1 and broadening the spectrum of associated ocular phenotypes in Marfan syndrome, our findings suggest that pigmentary glaucoma may involve defects in fibrillin-1 microfibrils. © 2013 Wiley Periodicals, Inc.

Mapping of the disease locus and identification of ADAMTS10 as a candidate gene in a canine model of primary open angle glaucoma

Primary open angle glaucoma (POAG) is a leading cause of blindness worldwide, with elevated intraocular pressure as an important risk factor. Increased resistance to outflow of aqueous humor through the trabecular meshwork causes elevated intraocular pressure, but the specific mechanisms are unknown. In this study, we used genome-wide SNP arrays to map the disease gene in a colony of Beagle dogs with inherited POAG to within a single 4 Mb locus on canine chromosome 20. The Beagle POAG locus is syntenic to a previously mapped human quantitative trait locus for intraocular pressure on human chromosome 19. Sequence capture and next-generation sequencing of the entire canine POAG locus revealed a total of 2,692 SNPs segregating with disease. Of the disease-segregating SNPs, 54 were within exons, 8 of which result in amino acid substitutions. The strongest candidate variant causes a glycine to arginine substitution in a highly conserved region of the metalloproteinase ADAMTS10. Western blotting revealed ADAMTS10 protein is preferentially expressed in the trabecular meshwork, supporting an effect of the variant specific to aqueous humor outflow. The Gly661Arg variant in ADAMTS10 found in the POAG Beagles suggests that altered processing of extracellular matrix and/or defects in microfibril structure or function may be involved in raising intraocular pressure, offering specific biochemical targets for future research and treatment strategies.

Primary open angle glaucoma (POAG) is a leading cause of vision loss and blindness affecting tens of millions of people. Ocular hypertension is a strong risk factor for the disease and the only effective target of treatment. Ocular hypertension results from increased resistance to outflow of aqueous humor through the trabecular meshwork, a specialized filtration tissue consisting of alternating layers of cells and connective tissue, but the specific reasons for the increased resistance are not known. The animal model for human POAG used in this study was a colony of Beagle dogs that carry an inherited form of the disease in which ocular hypertension is the primary manifestation. We have found a variant in ADAMTS10 that belongs to a family of genes that contribute to formation of extracellular matrix and may itself be involved in formation of elastic microfiber structures. We found that the ADAMTS10 protein is expressed at particularly high levels in the trabecular meshwork. The candidate variant in ADAMTS10 found in the POAG–affected Beagles suggests that altered processing of connective tissue and/or elastic microfiber defects may be involved in raising eye pressure, offering specific biochemical targets for future research and treatment strategies.

Multiplex cytokine analysis reveals elevated concentration of interleukin-8 in glaucomatous aqueous humor

PURPOSE

To test the hypothesis that immune activation occurs in glaucoma by comparing concentrations of multiple cytokines in aqueous humor (AH) from patients with primary open angle glaucoma (POAG) and from cataract patients without glaucoma as controls.

METHODS

Cytokine concentrations in AH obtained during surgery were measured using microparticle-based immunoassays. Localized expression of IL-8 protein was investigated by immunohistochemistry of human eyes.

RESULTS

Eight cytokines (IL-1β, IL-2, IL-4, IL-5, IL-10, IL-12, IFN-γ, and TNF-α) were below the limits of detection, and two cytokines (IL-18 and IL-15) were detected at low levels or in only a few patients. Although IL-6 was detected in 26 of 30 control patients (median, 2.7 pg/mL) and in 23 of 29 POAG patients (median, 1.6 pg/mL), the difference was not statistically significant. IL-8 was detected in 28 of 30 control patients (median, 1.8 pg/mL) and in all 29 POAG patients (median, 4.9 pg/mL). The higher IL-8 concentration in the AH of POAG patients was statistically significant (P < 0.001). In pairs of eyes from patients with asymmetric glaucomatous optic nerve damage, IL-8 concentration was higher in the AH of the more severely affected eye (P < 0.05). Patients with severe visual field defects had higher IL-8 concentrations in the AH than did patients with mild visual field defects. IL-8 protein expression was found in human retina and optic nerve.

CONCLUSIONS

Concentration of the inflammatory cytokine IL-8 is significantly elevated in the AH of POAG patients, supporting the hypothesis that immune activation occurs in glaucoma.

Angiopoietin-like 7 secretion is induced by glaucoma stimuli and its concentration is elevated in glaucomatous aqueous humor

PURPOSE

To investigate the possibility that Angiopoietin-like 7 (ANGPTL7) protein is involved in the pathogenesis of glaucoma.

METHODS

Primary human trabecular meshwork (TM) cells and corneoscleral explants were stimulated with either dexamethasone (DEX) or transforming growth factor beta (TGFbeta), and ANGPTL7 protein secreted into culture medium was determined by Western blot analysis. The effect of stable overexpression of ANGPTL7 in transfected immortalized TM cell lines on collagen expression was investigated by immunocytochemistry. Localization of ANGPTL7 protein in human eyes was determined by immunohistochemistry. The concentration of ANGPTL7 protein in aqueous humor (AH) from patients with glaucoma and control patients was compared by Western blot analysis. The beagle model of primary open-angle glaucoma (POAG) was used to correlate ANGPTL7 protein levels in canine AH with disease progression.

RESULTS

TGFbeta and DEX stimulated secretion of ANGPTL7 protein by TM cells and corneoscleral explants. Overexpression of ANGPTL7 by immortalized TM cell lines increased expression of type I collagen. Expression of ANGPTL7 protein was located in the corneal stroma, near the limbus, and throughout the sclera, with lower expression in the TM. In the lamina cribrosa, ANGPTL7 expression was associated with the cribriform plates. The concentration of ANGPTL7 protein was elevated in AH from patients with glaucoma and increased as disease progressed in POAG beagle dogs.

CONCLUSIONS

Induction of ANGPTL7 secretion by glaucoma stimuli and increased concentration of ANGPTL7 in glaucomatous AH suggest that ANGPTL7 is overexpressed in glaucoma. Since overexpression of ANGPTL7 increases collagen expression, a potential disease mechanism, ANGPTL7 could have a pathogenic role in glaucoma, and may serve as a potential therapeutic target.

Linkage mapping of canine rod cone dysplasia type 2 (rcd2) to CFA7, the canine orthologue of human 1q32

PURPOSE

To map the canine rcd2 retinal degeneration locus. Rod-cone dysplasia type 2 (rcd2), an early-onset autosomal recessive form of progressive retinal atrophy (PRA), is phenotypically similar to early-onset forms of retinitis pigmentosa collectively termed Leber congenital amaurosis and segregates naturally in the collie breed of dog. Multiple genes have previously been evaluated as candidates for rcd2, but all have been excluded.

METHODS

A set of informative experimental pedigrees segregating the rcd2 phenotype was produced. A genome-wide scan of these pedigrees using a set of 241 markers was undertaken. To refine the localized homology between canine and human maps, an RH map of the identified rcd2 region was built using a 3000 cR panel. A positional candidate gene strategy was then undertaken to begin to evaluate potentially causative genes.

RESULTS

A locus responsible for the rcd2 phenotype was mapped to CFA7 in a region corresponding to human chromosome 1, region q32.1-q32.2. Maximum linkage was observed between rcd2 and marker FH3972 (theta = 0.02; lod = 25.53), and the critical region was flanked by markers FH2226 and FH3972. As CRB1 is the closest gene on human chromosome 1q known to cause retinal degeneration, canine gene-specific markers for CRB1 were developed, and this gene was excluded as a positional candidate for rcd2.

CONCLUSIONS

The rcd2 locus represents a novel retinal degeneration gene. It is anticipated that when identified, this gene will offer new insights into retinal developmental and degenerative processes, and new opportunities for exploring experimental therapies.

Cochlin deposits in the trabecular meshwork of the glaucomatous DBA/2J mouse

Cochlin deposits were observed in the trabecular meshwork (TM) of 8-month-old glaucomatous DBA/2J mice, coincident with the reported onset of increased intraocular pressure and optic nerve damage. An age-dependent increase in cochlin was observed up to 10 months of age and was paralleled by a decrease in type II collagen. Similar expression patterns exist in the TM of humans with primary open-angle glaucoma. Cochlin deposits, absent in non-glaucomatous mouse and human TM, may disrupt the TM extracellular matrix and obstruct aqueous humor circulation. Studies of DBA/2J mice offer promise for understanding the role cochlin may play in glaucoma.

Glaucoma in Patients with Ocular Inflammatory Disease

Uveitic glaucoma can pose some of the most challenging management problems faced by the ophthalmologist. A better understanding of the pathogenesis of glaucoma associated with ocular inflammatory disease is an important key to making appropriate therapeutic decisions. This article provides an update on recent advances in understanding the epidemiology and pathogenesis of uveitic glaucoma, as well as developments in the diagnosis and management of this condition.

Proteomics reveal Cochlin deposits associated with glaucomatous trabecular meshwork

The etiology of primary open angle glaucoma, a leading cause of age-related blindness, remains poorly defined, although elevated intraocular pressure (IOP) contributes to the disease progression. To better understand the mechanisms causing elevated IOP from aqueous humor circulation, we pursued proteomic analyses of trabecular meshwork (TM) from glaucoma and age-matched control donors. These analyses demonstrated that Cochlin, a protein associated with deafness disorder DFNA9, is present in glaucomatous but absent in normal TM. Cochlin was also detected in TM from the glaucomatous DBA/2J mouse preceding elevated IOP but found to be absent in three other mouse lines that do not develop elevated IOP. Histochemical analyses revealed co-deposits of Cochlin and mucopolysaccharide in human TM around Schlemm's canal, similar to that observed in the cochlea in DFNA9 deafness. Purified Cochlin was found to aggregate after sheer stress and to induce the aggregation of TM cells in vitro. Age-dependent in vivo increases in Cochlin were observed in glaucomatous TM, concomitant with a decrease in type II collagen, suggesting that Cochlin may disrupt the TM architecture and render components like collagen more susceptible to degradation and collapse. Overall, these observations suggest that Cochlin contributes to elevated IOP in primary open angle glaucoma through altered interactions within the TM extracellular matrix, resulting in cell aggregation, mucopolysaccharide deposition, and significant obstruction of the aqueous humor circulation.