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Wu HJ, Krystofiak E, Kuchtey J, Kuchtey RW. Enhanced Optic Nerve Expansion and Altered Ultrastructure of Elastic Fibers Induced by Lysyl Oxidase Inhibition in a Mouse Model of Marfan Syndrome. THE AMERICAN JOURNAL OF PATHOLOGY 2024; 194:1317-1328. [PMID: 38548269 DOI: 10.1016/j.ajpath.2024.03.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/27/2023] [Revised: 02/27/2024] [Accepted: 03/11/2024] [Indexed: 04/09/2024]
Abstract
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-lysyl oxidase inhibitor β-aminopropionitrile (BAPN) was used to treat adult wild-type (WT) mice and mice heterozygous for a missense mutation in Fbn1 (Fbn1C1041G/+) 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.
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Affiliation(s)
- Hang-Jing Wu
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Evan Krystofiak
- Cell Imaging Shared Resource, Vanderbilt University, Nashville, Tennessee
| | - John Kuchtey
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee
| | - Rachel W Kuchtey
- Vanderbilt Eye Institute, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee.
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2
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Li G, van Batenburg‐Sherwood J, Safa BN, Fraticelli Guzmán NS, Wilson A, Bahrani Fard MR, Choy K, de Ieso ML, Cui JS, Feola AJ, Weisz T, Kuhn M, Bowes Rickman C, Farsiu S, Ethier CR, Stamer WD. Aging and intraocular pressure homeostasis in mice. Aging Cell 2024; 23:e14160. [PMID: 38566432 PMCID: PMC11258442 DOI: 10.1111/acel.14160] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2023] [Revised: 03/09/2024] [Accepted: 03/14/2024] [Indexed: 04/04/2024] Open
Abstract
Age and elevated intraocular pressure (IOP) are the two primary risk factors for glaucoma, an optic neuropathy that is the leading cause of irreversible blindness. In most people, IOP is tightly regulated over a lifetime by the conventional outflow tissues. However, the mechanistic contributions of age to conventional outflow dysregulation, elevated IOP and glaucoma are unknown. To address this gap in knowledge, we studied how age affects the morphology, biomechanical properties and function of conventional outflow tissues in C57BL/6 mice, which have an outflow system similar to humans. As reported in humans, we observed that IOP in mice was maintained within a tight range over their lifespan. Remarkably, despite a constellation of age-related changes to the conventional outflow tissues that would be expected to hinder aqueous drainage and impair homeostatic function (decreased cellularity, increased pigment accumulation, increased cellular senescence and increased stiffness), outflow facility, a measure of conventional outflow tissue fluid conductivity, was stable with age. We conclude that the murine conventional outflow system has significant functional reserve in healthy eyes. However, these age-related changes, when combined with other underlying factors, such as genetic susceptibility, are expected to increase risk for ocular hypertension and glaucoma.
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Affiliation(s)
- Guorong Li
- Department of OphthalmologyDuke UniversityDurhamNorth CarolinaUSA
| | | | - Babak N. Safa
- Wallace H. Coulter Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGeorgiaUSA
| | - Nina Sara Fraticelli Guzmán
- Department of OphthalmologyEmory UniversityAtlantaGeorgiaUSA
- George W. Woodruff School of Mechanical EngineeringGeorgia Institute of TechnologyAtlantaGeorgiaUSA
| | - Andrea Wilson
- Department of OphthalmologyDuke UniversityDurhamNorth CarolinaUSA
| | - Mohammad Reza Bahrani Fard
- Wallace H. Coulter Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGeorgiaUSA
| | - Kevin Choy
- Department of Biomedical EngineeringDuke UniversityDurhamNorth CarolinaUSA
| | | | - J. Serena Cui
- Department of OphthalmologyDuke UniversityDurhamNorth CarolinaUSA
| | - Andrew J. Feola
- Department of OphthalmologyEmory UniversityAtlantaGeorgiaUSA
- Department of Biomedical EngineeringDuke UniversityDurhamNorth CarolinaUSA
- Center for Visual and Neurocognitive RehabilitationAtlanta Virginia Medical CenterDecaturGeorgiaUSA
| | - Tara Weisz
- Department of OphthalmologyDuke UniversityDurhamNorth CarolinaUSA
| | - Megan Kuhn
- Department of OphthalmologyDuke UniversityDurhamNorth CarolinaUSA
| | | | - Sina Farsiu
- Department of OphthalmologyDuke UniversityDurhamNorth CarolinaUSA
- Department of Biomedical EngineeringDuke UniversityDurhamNorth CarolinaUSA
| | - C. Ross Ethier
- Wallace H. Coulter Department of Biomedical EngineeringGeorgia Institute of Technology and Emory UniversityAtlantaGeorgiaUSA
- Department of OphthalmologyEmory UniversityAtlantaGeorgiaUSA
| | - W. Daniel Stamer
- Department of OphthalmologyDuke UniversityDurhamNorth CarolinaUSA
- Department of Biomedical EngineeringDuke UniversityDurhamNorth CarolinaUSA
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3
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Meyer KJ, Fingert JH, Anderson MG. Lack of evidence for GWAS signals of exfoliation glaucoma working via monogenic loss-of-function mutation in the nearest gene. Hum Mol Genet 2024:ddae088. [PMID: 38770563 DOI: 10.1093/hmg/ddae088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 04/29/2024] [Accepted: 05/14/2024] [Indexed: 05/22/2024] Open
Abstract
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.
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Affiliation(s)
- Kacie J Meyer
- Department of Molecular Physiology and Biophysics, University of Iowa, 51 Newton Rd, Iowa City, IA 52242, United States
- Institute for Vision Research, University of Iowa, 375 Newton Rd, Iowa City, IA 52242, United States
| | - John H Fingert
- Institute for Vision Research, University of Iowa, 375 Newton Rd, Iowa City, IA 52242, United States
- Department of Ophthalmology and Visual Sciences, University of Iowa, 200 Hawkins Dr, Iowa City, IA 52242, United States
| | - Michael G Anderson
- Department of Molecular Physiology and Biophysics, University of Iowa, 51 Newton Rd, Iowa City, IA 52242, United States
- Institute for Vision Research, University of Iowa, 375 Newton Rd, Iowa City, IA 52242, United States
- Department of Ophthalmology and Visual Sciences, University of Iowa, 200 Hawkins Dr, Iowa City, IA 52242, United States
- Center for the Prevention and Treatment of Visual Loss, Iowa City VA Health Care System, 601 Hwy 6 W, Iowa City, IA 52246, United States
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Becker S, L'Ecuyer Z, Jones BW, Zouache MA, McDonnell FS, Vinberg F. Modeling complex age-related eye disease. Prog Retin Eye Res 2024; 100:101247. [PMID: 38365085 DOI: 10.1016/j.preteyeres.2024.101247] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 01/31/2024] [Accepted: 02/02/2024] [Indexed: 02/18/2024]
Abstract
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.
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Affiliation(s)
- Silke Becker
- John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA
| | - Zia L'Ecuyer
- John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA
| | - Bryan W Jones
- John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA
| | - Moussa A Zouache
- John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA
| | - Fiona S McDonnell
- John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA; Biomedical Engineering, University of Utah, Salt Lake City, UT, USA
| | - Frans Vinberg
- John A. Moran Eye Center, University of Utah, Salt Lake City, UT, USA; Biomedical Engineering, University of Utah, Salt Lake City, UT, USA.
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5
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Melton HJ, Zhang Z, Wu C. SUMMIT-FA: a new resource for improved transcriptome imputation using functional annotations. Hum Mol Genet 2024; 33:624-635. [PMID: 38129112 PMCID: PMC10954367 DOI: 10.1093/hmg/ddad205] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 10/24/2023] [Accepted: 11/30/2023] [Indexed: 12/23/2023] Open
Abstract
Transcriptome-wide association studies (TWAS) integrate gene expression prediction models and genome-wide association studies (GWAS) to identify gene-trait associations. The power of TWAS is determined by the sample size of GWAS and the accuracy of the expression prediction model. Here, we present a new method, the Summary-level Unified Method for Modeling Integrated Transcriptome using Functional Annotations (SUMMIT-FA), which improves gene expression prediction accuracy by leveraging functional annotation resources and a large expression quantitative trait loci (eQTL) summary-level dataset. We build gene expression prediction models in whole blood using SUMMIT-FA with the comprehensive functional database MACIE and eQTL summary-level data from the eQTLGen consortium. We apply these models to GWAS for 24 complex traits and show that SUMMIT-FA identifies significantly more gene-trait associations and improves predictive power for identifying "silver standard" genes compared to several benchmark methods. We further conduct a simulation study to demonstrate the effectiveness of SUMMIT-FA.
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Affiliation(s)
- Hunter J Melton
- Department of Statistics, Florida State University, 214 Rogers Building, 117 N. Woodward Avenue, Tallahassee, FL 32306, United States
| | - Zichen Zhang
- Department of Biostatistics, The University of Texas MD Anderson Cancer Center, 7007 Bertner Avenue, Unit 1689, Houston, TX 77030, United States
| | - Chong Wu
- Department of Biostatistics, The University of Texas MD Anderson Cancer Center, 7007 Bertner Avenue, Unit 1689, Houston, TX 77030, United States
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6
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Li G, van Batenburg-Sherwood J, Safa BN, Fraticelli Guzmán NS, Wilson A, Bahrani Fard MR, Choy K, De Ieso ML, Cui JS, Feola AJ, Weisz T, Kuhn M, Rickman CB, Farsiu S, Ethier CR, Stamer WD. Aging and intraocular pressure homeostasis in mice. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.10.17.562768. [PMID: 38106150 PMCID: PMC10723259 DOI: 10.1101/2023.10.17.562768] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2023]
Abstract
Age and elevated intraocular pressure (IOP) are the two primary risk factors for glaucoma, an optic neuropathy that is the leading cause of irreversible blindness. In most people, IOP is tightly regulated over a lifetime by the conventional outflow tissues. However, the mechanistic contributions of age to conventional outflow dysregulation, elevated IOP and glaucoma are unknown. To address this gap in knowledge, we studied how age affects the morphology, biomechanical properties and function of conventional outflow tissues in C57BL/6 mice, which have an outflow system similar to humans. As reported in humans, we observed that IOP in mice was maintained within a tight range over their lifespan. Remarkably, despite a constellation of age-related changes to the conventional outflow tissues that would be expected to hinder aqueous drainage and impair homeostatic function (decreased cellularity, increased pigment accumulation, increased cellular senescence and increased stiffness), outflow facility, a measure of conventional outflow tissue fluid conductivity, was stable with age. We conclude that the murine conventional outflow system has significant functional reserve in healthy eyes. However, these age-related changes, when combined with other underlying factors, such as genetic susceptibility, are expected to increase risk for ocular hypertension and glaucoma.
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7
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Suarez MF, Schmitt HM, Kuhn MS, Watkins T, Hake KM, Weisz T, Flynn EJ, Elliott MH, Hauser MA, Stamer WD. Genetic background determines severity of Loxl1-mediated systemic and ocular elastosis in mice. Dis Model Mech 2023; 16:dmm050392. [PMID: 37905384 PMCID: PMC10668029 DOI: 10.1242/dmm.050392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2023] [Accepted: 10/20/2023] [Indexed: 11/02/2023] Open
Abstract
Pseudoexfoliation syndrome (PEX) is a systemic, age-related disorder characterized by elastosis and extracellular matrix deposits. Its most significant ocular manifestation is an aggressive form of glaucoma associated with variants in the gene encoding lysyl oxidase-like 1 (LOXL1). Depending upon the population, variants in LOXL1 can impart risk or protection for PEX, suggesting the importance of genetic context. As LOXL1 protein levels are lower and the degree of elastosis is higher in people with PEX, we studied Loxl1-deficient mice on three different genetic backgrounds: C57BL/6 (BL/6), 129S×C57BL/6 (50/50) and 129S. Early onset and high prevalence of spontaneous pelvic organ prolapse in BL/6 Loxl1-/- mice necessitated the study of mice that were <2 months old. Similar to pelvic organ prolapse, most elastosis endpoints were the most severe in BL/6 Loxl1-/- mice, including skin laxity, pulmonary tropoelastin accumulation, expansion of Schlemm's canal and dilation of intrascleral veins. Interestingly, intraocular pressure was elevated in 50/50 Loxl1-/- mice, depressed in BL/6 Loxl1-/- mice and unchanged in 129S Loxl1-/- mice compared to that of control littermates. Overall, the 129S background was protective against most elastosis phenotypes studied. Thus, repair of elastin-containing tissues is impacted by the abundance of LOXL1 and genetic context in young animals.
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Affiliation(s)
- Maria F. Suarez
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
| | - Heather M. Schmitt
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
- Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - Megan S. Kuhn
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
| | - TeddiJo Watkins
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
| | - Kristyn M. Hake
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
- Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
| | - Tara Weisz
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
| | - Edward J. Flynn
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
| | - Michael H. Elliott
- Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
| | - Michael A. Hauser
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
- Duke Molecular Physiology Institute, Duke University, Durham, NC 27701, USA
- Department of Medicine, Duke University, Durham, NC 27710, USA
| | - W. Daniel Stamer
- Department of Ophthalmology, Duke University, Durham, NC 27705, USA
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8
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Lysyl oxidase-like 1 deficiency alters ultrastructural and biomechanical properties of the peripapillary sclera in mice. Matrix Biol Plus 2022; 16:100120. [PMID: 36060791 PMCID: PMC9436796 DOI: 10.1016/j.mbplus.2022.100120] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Accepted: 08/17/2022] [Indexed: 11/30/2022] Open
Abstract
Lysyl oxidate-like 1 knockout (Loxl1-/-) mice have decreased vision without elevated intraocular pressure. Loxl1-/- mice exhibit biometric changes of the anterior segment of the eye. Loxl1-/- mice have altered elastin and collagen structure in peripapillary sclera. Structural alternations of peripapillary sclera correlate with its increased stiffness in Loxl1-/- mice.
Lysyl oxidase-like 1 encoded by the LOXL1 gene is a member of the lysyl oxidase family of enzymes that are important in the maintenance of extracellular matrix (ECM)-rich tissue. LOXL1 is important for proper elastic fiber formation and mice lacking LOXL1 (Loxl1−/−) exhibit systemic elastic fiber disorders, such as pelvic organ prolapse, a phenotype associated with exfoliation syndrome (XFS) in humans. Patients with XFS have a significant risk of developing exfoliation glaucoma (XFG), a severe form of glaucoma, which is a neurodegenerative condition leading to irreversible blindness if not detected and treated in a timely fashion. Although Loxl1−/− mice have been used extensively to investigate mechanisms of pelvic organ prolapse, studies of eyes in those mice are limited and some showed inconsistent ocular phenotypes. In this study we demonstrate that Loxl1−/− mice have significant anterior segment biometric abnormalities which recapitulate some human XFS features. We then focused on the peripapillary sclera (PPS), a critical structure for maintaining optic nerve health. We discovered quantitative and qualitive changes in ultrastructure of PPS, such as reduced elastic fibers, enlarged collagen fibrils, and transformed collagen lamella organization detected by transmission electron microscopy (TEM). Importantly, these changes corelate with altered tissue biomechanics detected by Atomic Force Microscopy (AFM) of PPS in mice. Together, our results support a crucial role for LOXL1 in ocular tissue structure and biomechanics, and Loxl1−/− mice could be a valuable resource for understanding the role of scleral tissue biomechanics in ocular disease.
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9
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Enyong EN, Gurley JM, De Ieso ML, Stamer WD, Elliott MH. Caveolar and non-Caveolar Caveolin-1 in ocular homeostasis and disease. Prog Retin Eye Res 2022; 91:101094. [PMID: 35729002 PMCID: PMC9669151 DOI: 10.1016/j.preteyeres.2022.101094] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Revised: 06/03/2022] [Accepted: 06/10/2022] [Indexed: 11/17/2022]
Abstract
Caveolae, specialized plasma membrane invaginations present in most cell types, play important roles in multiple cellular processes including cell signaling, lipid uptake and metabolism, endocytosis and mechanotransduction. They are found in almost all cell types but most abundant in endothelial cells, adipocytes and fibroblasts. Caveolin-1 (Cav1), the signature structural protein of caveolae was the first protein associated with caveolae, and in association with Cavin1/PTRF is required for caveolae formation. Genetic ablation of either Cav1 or Cavin1/PTRF downregulates expression of the other resulting in loss of caveolae. Studies using Cav1-deficient mouse models have implicated caveolae with human diseases such as cardiomyopathies, lipodystrophies, diabetes and muscular dystrophies. While caveolins and caveolae are extensively studied in extra-ocular settings, their contributions to ocular function and disease pathogenesis are just beginning to be appreciated. Several putative caveolin/caveolae functions are relevant to the eye and Cav1 is highly expressed in retinal vascular and choroidal endothelium, Müller glia, the retinal pigment epithelium (RPE), and the Schlemm's canal endothelium and trabecular meshwork cells. Variants at the CAV1/2 gene locus are associated with risk of primary open angle glaucoma and the high risk HTRA1 variant for age-related macular degeneration is thought to exert its effect through regulation of Cav1 expression. Caveolins also play important roles in modulating retinal neuroinflammation and blood retinal barrier permeability. In this article, we describe the current state of caveolin/caveolae research in the context of ocular function and pathophysiology. Finally, we discuss new evidence showing that retinal Cav1 exists and functions outside caveolae.
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Affiliation(s)
- Eric N Enyong
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Jami M Gurley
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael L De Ieso
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, NC, USA
| | - W Daniel Stamer
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, NC, USA
| | - Michael H Elliott
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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10
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Mastronikolis S, Pagkalou M, Plotas P, Kagkelaris K, Georgakopoulos C. Emerging roles of oxidative stress in the pathogenesis of pseudoexfoliation syndrome (Review). Exp Ther Med 2022; 24:602. [PMID: 35949329 PMCID: PMC9353531 DOI: 10.3892/etm.2022.11539] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2022] [Accepted: 07/06/2022] [Indexed: 11/25/2022] Open
Abstract
Pseudoexfoliation syndrome (PEXS) is a systemic disease caused by defects in the extracellular matrix (ECM) remodelling process leading to the chronic deposition of extracellular, fibrillary, white flaky pseudoexfoliation material (PEXM) throughout the body. Specifically, PEXM deposits on the lens capsule cause open-angle glaucoma, cataracts and blindness in patients with PEXS. Several gene single nucleotide polymorphisms are linked to the development of PEXS in humans, including lysyl oxidase-like 1 gene, clusterin and fibulin-5. The exact reason for the PEXM generation and its resulting pathogenesis is not well understood. However, defective ECM remodelling and oxidative stress (OS) have been hypothesized as significant events leading to the PEXM. Specifically, the link between OS and PEXS has been well studied, although the investigation is still ongoing. The present review explored recent advances in various aspects of PEXS and the involvement of OS in the eye for PEXS development.
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Affiliation(s)
| | - Marina Pagkalou
- Department of Chemistry, University of Crete, 70013 Heraklion, Greece
| | - Panagiotis Plotas
- Laboratory of Primary Health Care, School of Health Rehabilitation Sciences, University of Patras, 26334 Patras, Greece
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11
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Behera G, Kaliaperumal S. Commentary: The genetics of pseudoexfoliation syndrome/glaucoma. Indian J Ophthalmol 2022; 70:2028-2029. [PMID: 35647974 PMCID: PMC9359298 DOI: 10.4103/ijo.ijo_30_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Geeta Behera
- Department of Ophthalmology, Jawaharlal Institute of Post-Graduate Medical Education and Research (JIPMER), Puducherry, India
| | - Subashini Kaliaperumal
- Department of Ophthalmology, Jawaharlal Institute of Post-Graduate Medical Education and Research (JIPMER), Puducherry, India
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12
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Madekurozwa M, Reina-Torres E, Overby DR, van Batenburg-Sherwood J. Measurement of postmortem outflow facility using iPerfusion. Exp Eye Res 2022; 220:109103. [PMID: 35525299 DOI: 10.1016/j.exer.2022.109103] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2022] [Revised: 04/24/2022] [Accepted: 04/28/2022] [Indexed: 11/04/2022]
Abstract
The key risk factor for glaucoma is elevation of intraocular pressure (IOP) and alleviating it is the only effective therapeutic approach to inhibit further vision loss. IOP is regulated by the flow of aqueous humour across resistive tissues, and a reduction in outflow facility C, is responsible for the IOP elevation in glaucoma. Measurement of C is therefore important when investigating the pathophysiology of glaucoma and testing candidate treatments for lowering IOP. Due to similar anatomy and response to pharmacological treatments, mouse eyes are a common model of human aqueous humour dynamics. The ex vivo preparation, in which an enucleated mouse eye is mounted in a temperature controlled bath and cannulated, has been well characterised and is widely used. The postmortem in situ model, in which the eyes are perfused within the cadaver, has received relatively little attention. In this study, we investigate the postmortem in situ model using the iPerfusion system, with a particular focus on i) the presence or absence of pressure-independent flow, ii) the effect of evaporation on measured flow rates and iii) the magnitude and pressure dependence of outflow facility and how these properties are affected by postmortem changes. Measurements immediately after cannulation and following multi-pressure facility measurement demonstrated negligible pressure-independent flow in postmortem eyes, in contrast to assumptions made in previous studies. Using a humidity chamber, we investigated whether the humidity of the surrounding air would influence measured flow rates. We found that at room levels of humidity, evaporation of saline droplets on the eye resulted in artefactual flow rates with a magnitude comparable to outflow, which were eliminated by a high relative humidity (>85%) environment. Average postmortem outflow facility was ∼4 nl/min/mmHg, similar to values observed ex vivo, irrespective of whether a postmortem delay was introduced prior to cannulation. The intra-animal variability of measured outflow facility values was also reduced relative to previous ex vivo data. The pressure-dependence of outflow facility was reduced in the postmortem relative to ex vivo model, and practically eliminated when eyes were cannulated >40 min after euthanisation. Overall, our results indicate that the moderately increased technical complexity associated with postmortem perfusion provides reduced variability and reduced pressure-dependence in outflow facility, when experimental conditions are properly controlled.
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Affiliation(s)
| | | | - Darryl R Overby
- Dept. of Bioengineering, Imperial College London, London, SW7 2AZ, UK.
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13
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Aboobakar IF, Wiggs JL. The genetics of glaucoma: Disease associations, personalised risk assessment and therapeutic opportunities-A review. Clin Exp Ophthalmol 2022; 50:143-162. [PMID: 35037362 DOI: 10.1111/ceo.14035] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2021] [Revised: 12/14/2021] [Accepted: 12/15/2021] [Indexed: 12/23/2022]
Abstract
Glaucoma refers to a heterogenous group of disorders characterised by progressive loss of retinal ganglion cells and associated visual field loss. Both early-onset and adult-onset forms of the disease have a strong genetic component. Here, we summarise the known genetic associations for various forms of glaucoma and the possible functional roles for these genes in disease pathogenesis. We also discuss efforts to translate genetic knowledge into clinical practice, including gene-based tests for disease diagnosis and risk-stratification as well as gene-based therapies.
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Affiliation(s)
- Inas F Aboobakar
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, USA
| | - Janey L Wiggs
- Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, USA
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14
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Mastronikolis S, Pagkalou M, Baroutas G, Kyriakopoulou K, Makri ΟE, Georgakopoulos CD. Pseudoexfoliation syndrome: The critical role of the extracellular matrix in pathogenesis and treatment. IUBMB Life 2022; 74:995-1002. [PMID: 35201654 DOI: 10.1002/iub.2606] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/30/2022] [Accepted: 02/07/2022] [Indexed: 11/11/2022]
Abstract
Pseudoexfoliation syndrome (PEXS) is an age-related condition manifesting mainly in ocular tissues. PEXS is manifested through excess aggregation of fibrillary extracellular material at the anterior part of the eye that consists of a plethora of biomolecules, such as different proteoglycans (PGs) and glycosaminoglycans. PEXS is often linked to increased intraocular pressure, and can also lead to pseudoexfoliation glaucoma with very poor prognosis. Various stimuli are known to affect PEXS, including oxidation stress (OS), UV radiation and osmotic pressure. OS, is prominently involved on the progression of the syndrome as it promotes fibrogenesis, possibly via the induction of transforming growth factor-β (TGF-β) and other biomolecular effectors. In addition, PEXS initiation is tightly connected with the dysregulation of extracellular matrix (ECM) homeostasis since aberrant expression of ECM molecules is linked to both the accumulation and low degradation of pseudoexfoliation material. This article aims at uncovering the crucial role of various ECM effectors such as lysyl oxidase-like proteins, matrix metalloproteinases, and TGF-β1, as well as the biochemical pathways involved in the development and the progression of the PEXS.
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Affiliation(s)
- Stylianos Mastronikolis
- Department of Ophthalmology, Medical School, University of Patras, Rion, Achaia, Greece.,Neurosurgery Department, James Cook University Hospital, Middlesbrough, UK
| | - Marina Pagkalou
- Department of Chemistry, University of Crete, Voutes, Heraklion, Greece
| | - Giorgos Baroutas
- Biochemistry Biochemical Analysis & Matrix Pathobiology Research Group, Laboratory of Biochemistry, Department of Chemistry, University of Patras, Patras, Greece
| | - Konstantina Kyriakopoulou
- Biochemistry Biochemical Analysis & Matrix Pathobiology Research Group, Laboratory of Biochemistry, Department of Chemistry, University of Patras, Patras, Greece
| | - Οlga E Makri
- Department of Ophthalmology, Medical School, University of Patras, Rion, Achaia, Greece
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15
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Choy KC, Li G, Stamer WD, Farsiu S. Open-source deep learning-based automatic segmentation of mouse Schlemm's canal in optical coherence tomography images. Exp Eye Res 2022; 214:108844. [PMID: 34793828 PMCID: PMC8792324 DOI: 10.1016/j.exer.2021.108844] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Revised: 10/25/2021] [Accepted: 11/11/2021] [Indexed: 01/03/2023]
Abstract
The purpose of this study was to develop an automatic deep learning-based approach and corresponding free, open-source software to perform segmentation of the Schlemm's canal (SC) lumen in optical coherence tomography (OCT) scans of living mouse eyes. A novel convolutional neural network (CNN) for semantic segmentation grounded in a U-Net architecture was developed by incorporating a late fusion scheme, multi-scale input image pyramid, dilated residual convolution blocks, and attention-gating. 163 pairs of intensity and speckle variance (SV) OCT B-scans acquired from 32 living mouse eyes were used for training, validation, and testing of this CNN model for segmentation of the SC lumen. The proposed model achieved a mean Dice Similarity Coefficient (DSC) of 0.694 ± 0.256 and median DSC of 0.791, while manual segmentation performed by a second expert grader achieved a mean and median DSC of 0.713 ± 0.209 and 0.763, respectively. This work presents the first automatic method for segmentation of the SC lumen in OCT images of living mouse eyes. The performance of the proposed model is comparable to the performance of a second human grader. Open-source automatic software for segmentation of the SC lumen is expected to accelerate experiments for studying treatment efficacy of new drugs affecting intraocular pressure and related diseases such as glaucoma, which present as changes in the SC area.
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Affiliation(s)
- Kevin C Choy
- Department of Biomedical Engineering, Duke University, Durham, NC, United States
| | - Guorong Li
- Department of Ophthalmology, Duke University, Durham, NC, United States
| | - W Daniel Stamer
- Department of Biomedical Engineering, Duke University, Durham, NC, United States; Department of Ophthalmology, Duke University, Durham, NC, United States
| | - Sina Farsiu
- Department of Biomedical Engineering, Duke University, Durham, NC, United States; Department of Ophthalmology, Duke University, Durham, NC, United States.
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16
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Zhang M, Sun S, Wang L, Wang X, Chen T, Chen Z, Jiang Y. Zonular defects in loxl1-deficient zebrafish. Clin Exp Ophthalmol 2021; 50:62-73. [PMID: 34585825 DOI: 10.1111/ceo.14017] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Revised: 08/17/2021] [Accepted: 09/25/2021] [Indexed: 12/13/2022]
Abstract
BACKGROUND To investigate the roles of the lysyl oxidase-like 1 (loxl1) gene in zebrafish eye development and the potency of loxl1 deficiency in mimicking the ocular manifestations of exfoliation syndrome (XFS). METHODS CRISPR/Cas9 technology was used to generate a frameshift coding deletion in zebrafish loxl1. Expression profiles and ocular manifestations of the wildtype, heterozygous mutant (loxl1+/- ) and homozygous mutant (loxl1-/- ) zebrafish were analysed in a range of developmental stages from zebrafish larvae to dissected adult zebrafish eyes. RESULTS The loxl1 deficiency caused zonular bundling disorders in juvenile zebrafish and accumulation of pearl-like particles adhering to the adult zebrafish zonule. The bundles appeared to lack form and were thinner in both loxl1+/- and loxl1-/- zebrafish compared with the wildtype (p < 0.01 for all Bonferroni post-hoc analyses). The zonule of loxl1-/- zebrafish appeared stretched, ragged and torn, with isolated fibres also detected. The particles in loxl1-/- zebrafish were more numerous (counts: 92.33 ± 10.02/100 μm2 vs. 58.33 ± 5.03/100 μm2 , p = 0.006), but smaller in size (diameter: 0.21 ± 0.03 μm vs. 0.43 ± 0.04 μm, p = 0.002) compared with those in loxl1+/- . Transmission electron microscopy revealed thinning or even loss of elastic lamina in loxl1+/- Bruch's membrane (BM) (thickness of elastic lamina: 92.94 ± 18.19 nm in the wildtype vs 35.65 ± 14.76 nm in loxl1+/- , p = 0.003). The breakage of BM was observed in loxl1-/- . CONCLUSIONS The loxl1-/- zebrafish is a promising animal model of XFS zonular pathology.
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Affiliation(s)
- Min Zhang
- Department of Ophthalmology and Vision Science, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, and Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China.,Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
| | - Shaoyang Sun
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Lei Wang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Xu Wang
- Key Laboratory of Metabolism and Molecular Medicine, Ministry of Education, Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Fudan University, Shanghai, China
| | - Tianhui Chen
- Department of Ophthalmology and Vision Science, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, and Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China
| | - Zexu Chen
- Department of Ophthalmology and Vision Science, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, and Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China
| | - Yongxiang Jiang
- Department of Ophthalmology and Vision Science, Eye & ENT Hospital, Fudan University, Shanghai, China.,NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, and Shanghai Key Laboratory of Visual Impairment and Restoration, Shanghai, China
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17
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Wang T, Guo Y, Liu S, Zhang C, Cui T, Ding K, Wang P, Wang X, Wang Z. KLF4, a Key Regulator of a Transitive Triplet, Acts on the TGF-β Signaling Pathway and Contributes to High-Altitude Adaptation of Tibetan Pigs. Front Genet 2021; 12:628192. [PMID: 33936161 PMCID: PMC8082500 DOI: 10.3389/fgene.2021.628192] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 03/10/2021] [Indexed: 11/13/2022] Open
Abstract
Tibetan pigs are native mammalian species on the Tibetan Plateau that have evolved distinct physiological traits that allow them to tolerate high-altitude hypoxic environments. However, the genetic mechanism underlying this adaptation remains elusive. Here, based on multitissue transcriptional data from high-altitude Tibetan pigs and low-altitude Rongchang pigs, we performed a weighted correlation network analysis (WGCNA) and identified key modules related to these tissues. Complex network analysis and bioinformatics analysis were integrated to identify key genes and three-node network motifs. We found that among the six tissues (muscle, liver, heart, spleen, kidneys, and lungs), lung tissue may be the key organs for Tibetan pigs to adapt to hypoxic environment. In the lung tissue of Tibetan pigs, we identified KLF4, BCL6B, EGR1, EPAS1, SMAD6, SMAD7, KDR, ATOH8, and CCN1 genes as potential regulators of hypoxia adaption. We found that KLF4 and EGR1 genes might simultaneously regulate the BCL6B gene, forming a KLF4-EGR1-BCL6B complex. This complex, dominated by KLF4, may enhance the hypoxia tolerance of Tibetan pigs by mediating the TGF-β signaling pathway. The complex may also affect the PI3K-Akt signaling pathway, which plays an important role in angiogenesis caused by hypoxia. Therefore, we postulate that the KLF4-EGR1-BCL6B complex may be beneficial for Tibetan pigs to survive better in the hypoxia environments. Although further molecular experiments and independent large-scale studies are needed to verify our findings, these findings may provide new details of the regulatory architecture of hypoxia-adaptive genes and are valuable for understanding the genetic mechanism of hypoxic adaptation in mammals.
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Affiliation(s)
- Tao Wang
- College of Animal Science and Technology, Northeast Agricultural University, Harbin, China.,Bioinformatics Center, Northeast Agricultural University, Harbin, China
| | - Yuanyuan Guo
- College of Animal Science and Technology, Northeast Agricultural University, Harbin, China.,Bioinformatics Center, Northeast Agricultural University, Harbin, China
| | - Shengwei Liu
- College of Animal Science and Technology, Northeast Agricultural University, Harbin, China.,Bioinformatics Center, Northeast Agricultural University, Harbin, China
| | - Chaoxin Zhang
- College of Animal Science and Technology, Northeast Agricultural University, Harbin, China.,Bioinformatics Center, Northeast Agricultural University, Harbin, China
| | - Tongyan Cui
- College of Animal Science and Technology, Northeast Agricultural University, Harbin, China.,Bioinformatics Center, Northeast Agricultural University, Harbin, China
| | - Kun Ding
- College of Computer Science and Technology, Inner Mongolia Normal University, Hohhot, China
| | - Peng Wang
- HeiLongJiang Provincial Husbandry Department, Harbin, China
| | - Xibiao Wang
- College of Animal Science and Technology, Northeast Agricultural University, Harbin, China
| | - Zhipeng Wang
- College of Animal Science and Technology, Northeast Agricultural University, Harbin, China.,Bioinformatics Center, Northeast Agricultural University, Harbin, China
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18
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De Ieso ML, Gurley JM, McClellan ME, Gu X, Navarro I, Li G, Gomez-Caraballo M, Enyong E, Stamer WD, Elliott MH. Physiologic Consequences of Caveolin-1 Ablation in Conventional Outflow Endothelia. Invest Ophthalmol Vis Sci 2021; 61:32. [PMID: 32940661 PMCID: PMC7500130 DOI: 10.1167/iovs.61.11.32] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Purpose Polymorphisms at the caveolin-1/2 locus are associated with glaucoma and IOP risk and deletion of caveolin-1 (Cav1) in mice elevates IOP and reduces outflow facility. However, the specific location/cell type responsible for Cav1-dependent regulation of IOP is unclear. We hypothesized that endothelial Cav1 in the conventional outflow (CO) pathway regulate IOP via endothelial nitric oxide synthase (eNOS) signaling. Methods We created a mouse with targeted deletion of Cav1 in endothelial cells (Cav1ΔEC) and evaluated IOP, outflow facility, outflow pathway distal vascular morphology, eNOS phosphorylation, and tyrosine nitration of iridocorneal angle tissues by Western blotting. Results Endothelial deletion of Cav1 resulted in significantly elevated IOP versus wild-type mice but not a concomitant decrease in outflow facility. Endothelial Cav1 deficiency did not alter the trabecular meshwork or Schlemm's canal morphology, suggesting that the effects observed were not due to developmental deformities. Endothelial Cav1 deletion resulted in eNOS hyperactivity, modestly increased protein nitration, and significant enlargement of the drainage vessels distal to Schlemm's canal. L-Nitro-arginine methyl ester treatment reduced outflow in Cav1ΔEC but not wild-type mice and had no effect on the size of drainage vessels. Endothelin-1 treatment decrease the outflow and drainage vessel size in both wild-type and Cav1ΔEC mice. Conclusions Our results suggest that hyperactive eNOS signaling in the CO pathway of both Cav1ΔEC and global Cav1 knockout mice results in chronic dilation of distal CO vessels and protein nitration, but that Cav1 expression in the trabecular meshwork is sufficient to rescue CO defects reported in global Cav1 knockout mice.
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Affiliation(s)
- Michael L De Ieso
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, North Carolina, United States
| | - Jami M Gurley
- Department of Ophthalmology, Dean McGee Eye Institute University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Mark E McClellan
- Department of Ophthalmology, Dean McGee Eye Institute University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Xiaowu Gu
- Department of Ophthalmology, Dean McGee Eye Institute University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - Iris Navarro
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, North Carolina, United States
| | - Guorong Li
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, North Carolina, United States
| | - Maria Gomez-Caraballo
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, North Carolina, United States
| | - Eric Enyong
- Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
| | - W Daniel Stamer
- Department of Ophthalmology, Duke Eye Center, Duke University, Durham, North Carolina, United States
| | - Michael H Elliott
- Department of Ophthalmology, Dean McGee Eye Institute University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States.,Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, United States
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19
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Abstract
PURPOSE OF REVIEW The genetic basis of pseudoexfoliation (PEX) syndrome, the most common identifiable cause of open-angle glaucoma, is steadily being elucidated. This review summarizes the recent advances on genetic risk factors for PEX syndrome/glaucoma and their potential functional implications in PEX pathophysiology. RECENT FINDINGS As of today, seven loci associated with the risk of PEX surpassing genome-wide significance have been identified by well-powered genome-wide association studies and sequencing efforts. LOXL1 (lysyl oxidase-like 1) represents the major genetic effect locus, although the biological role of common risk variants and their reversed effect in different ethnicities remain an unresolved problem. Rare protein-coding variants at LOXL1 and a single noncoding variant downstream of LOXL1 showed no allele effect reversal and suggested potential roles for elastin homeostasis and vitamin A metabolism in PEX pathogenesis. Other PEX-associated genetic variants provided biological insights into additional disease processes and pathways, including ubiquitin-proteasome function, calcium signaling, and lipid biosynthesis. Gene-environment interactions, epigenetic alterations, and integration of multiomics data have further contributed to our knowledge of the complex etiology underlying PEX syndrome and glaucoma. SUMMARY PEX-associated genes are beginning to reveal relevant biological pathways and processes involved in disease development. To understand the functional consequences and molecular mechanisms of these loci and to translate them into novel therapeutic approaches are the major challenges for the future.
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20
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Lee C, Li G, Stamer WD, Ethier CR. In vivo estimation of murine iris stiffness using finite element modeling. Exp Eye Res 2021; 202:108374. [PMID: 33253706 PMCID: PMC7855533 DOI: 10.1016/j.exer.2020.108374] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Revised: 11/22/2020] [Accepted: 11/23/2020] [Indexed: 12/17/2022]
Abstract
The iris plays an important role in certain types of glaucoma, including primary angle-closure glaucoma and pigmentary glaucoma. Iris mechanics are also important in influencing trabecular meshwork deformation in response to intraocular pressure changes in some animal species. Although mice are widely used to study ocular disease, including glaucoma, the in vivo biomechanical properties of the murine iris are unknown. Thus, the primary objective of this study was to estimate murine iris biomechanical stiffness. We used optical coherence tomography (OCT) images of the anterior segment of living mice (n = 13, age = 7.3 ± 3.2 [mean ± SD] months) at sequentially increasing IOP levels, observing IOP-dependent iris deformations. We then used an inverse finite element model to predict iris deformations under the same conditions, estimating iris stiffness by maximizing agreement between OCT data and numerical simulations. Our results show an in vivo murine iris stiffness of 96.1 ± 54.7 kPa (mean ± SD), which did not correlate with age but was dependent on gender. Our results further showed strong evidence of reverse pupillary block, with mean posterior chamber pressure remaining at approximately 12 mmHg even as anterior chamber pressure was set to much higher levels. Our approach to monitoring iris stiffness in vivo is applicable to study potential changes of iris stiffness in various pathophysiological conditions and thus has significant potential for clinical care of ocular disease involving iris biomechanics.
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Affiliation(s)
- Chanyoung Lee
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Guorong Li
- Department of Ophthalmology, Duke University, Durham, NC, USA
| | - W Daniel Stamer
- Department of Ophthalmology, Duke University, Durham, NC, USA
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA.
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21
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Molecular Genetics of Glaucoma: Subtype and Ethnicity Considerations. Genes (Basel) 2020; 12:genes12010055. [PMID: 33396423 PMCID: PMC7823611 DOI: 10.3390/genes12010055] [Citation(s) in RCA: 32] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 12/27/2020] [Accepted: 12/28/2020] [Indexed: 12/11/2022] Open
Abstract
Glaucoma, the world’s leading cause of irreversible blindness, is a complex disease, with differential presentation as well as ethnic and geographic disparities. The multifactorial nature of glaucoma complicates the study of genetics and genetic involvement in the disease process. This review synthesizes the current literature on glaucoma and genetics, as stratified by glaucoma subtype and ethnicity. Primary open-angle glaucoma (POAG) is the most common cause of glaucoma worldwide, with the only treatable risk factor (RF) being the reduction of intraocular pressure (IOP). Genes associated with elevated IOP or POAG risk include: ABCA1, AFAP1, ARHGEF12, ATXN2, CAV1, CDKN2B-AS1, FOXC1, GAS7, GMDS, SIX1/SIX6, TMCO1, and TXNRD2. However, there are variations in RF and genetic factors based on ethnic and geographic differences; it is clear that unified molecular pathways accounting for POAG pathogenesis remain uncertain, although inflammation and senescence likely play an important role. There are similar ethnic and geographic complexities in primary angle closure glaucoma (PACG), but several genes have been associated with this disorder, including MMP9, HGF, HSP70, MFRP, and eNOS. In exfoliation glaucoma (XFG), genes implicated include LOXL1, CACNA1A, POMP, TMEM136, AGPAT1, RBMS3, and SEMA6A. Despite tremendous progress, major gaps remain in resolving the genetic architecture for the various glaucoma subtypes across ancestries. Large scale carefully designed studies are required to advance understanding of genetic loci as RF in glaucoma pathophysiology and to improve diagnosis and treatment options.
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