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Goyal V, Read AT, Brown DM, Brawer L, Bateh K, Hannon BG, Feola AJ, Ethier CR. Morphometric Analysis of Retinal Ganglion Cell Axons in Normal and Glaucomatous Brown Norway Rats Optic Nerves. Transl Vis Sci Technol 2023; 12:8. [PMID: 36917118 PMCID: PMC10020949 DOI: 10.1167/tvst.12.3.8] [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: 04/19/2022] [Accepted: 11/23/2022] [Indexed: 03/15/2023] Open
Abstract
Purpose A reference atlas of optic nerve (ON) retinal ganglion cell (RGC) axons could facilitate studies of neuro-ophthalmic diseases by detecting subtle RGC axonal changes. Here we construct an RGC axonal atlas for normotensive eyes in Brown Norway rats, widely used in glaucoma research, and also develop/evaluate several novel metrics of axonal damage in hypertensive eyes. Methods Light micrographs of entire ON cross-sections from hypertensive and normotensive eyes were processed through a deep learning-based algorithm, AxoNet2.0, to determine axonal morphological properties and were semiquantitatively scored using the Morrison grading scale (MGS) to provide a damage score independent of AxoNet2.0 outcomes. To construct atlases, ONs were conformally mapped onto an ON "template," and axonal morphometric data was computed for each region. We also developed damage metrics based on myelin morphometry. Results In normotensive eyes, average axon density was ∼0.3 axons/µm2 (i.e., ∼80,000 axons in an ON). We measured axoplasm diameter, eccentricity, cross-sectional area, and myelin g-ratio and thickness. Most morphological parameters exhibited a wide range of coefficients of variation (CoV); however, myelin thickness CoV was only ∼2% in normotensive eyes. In hypertensive eyes, increased myelin thickness correlated strongly with MGS (P < 0.0001). Conclusions We present the first comprehensive normative RGC axon morphometric atlas for Brown Norway rat eyes. We suggest objective, repeatable damage metrics based on RGC axon myelin thickness for hypertensive eyes. Translational Relevance These tools can evaluate regional changes in RGCs and overall levels of damage in glaucoma studies using Brown Norway rats.
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Affiliation(s)
- Vidisha Goyal
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - A. Thomas Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Dillon M. Brown
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Luke Brawer
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Kaitlyn Bateh
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Bailey G. Hannon
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Andrew J. Feola
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, USA
- Department of Ophthalmology, Emory University, Atlanta, GA, USA
| | - C. Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- Department of Ophthalmology, Emory University, Atlanta, GA, USA
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Goyal V, Read AT, Ritch MD, Hannon BG, Rodriguez GS, Brown DM, Feola AJ, Hedberg-Buenz A, Cull GA, Reynaud J, Garvin MK, Anderson MG, Burgoyne CF, Ethier CR. AxoNet 2.0: A Deep Learning-Based Tool for Morphometric Analysis of Retinal Ganglion Cell Axons. Transl Vis Sci Technol 2023; 12:9. [PMID: 36917117 PMCID: PMC10020950 DOI: 10.1167/tvst.12.3.9] [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: 04/19/2022] [Accepted: 01/30/2023] [Indexed: 03/16/2023] Open
Abstract
Purpose Assessment of glaucomatous damage in animal models is facilitated by rapid and accurate quantification of retinal ganglion cell (RGC) axonal loss and morphologic change. However, manual assessment is extremely time- and labor-intensive. Here, we developed AxoNet 2.0, an automated deep learning (DL) tool that (i) counts normal-appearing RGC axons and (ii) quantifies their morphometry from light micrographs. Methods A DL algorithm was trained to segment the axoplasm and myelin sheath of normal-appearing axons using manually-annotated rat optic nerve (ON) cross-sectional micrographs. Performance was quantified by various metrics (e.g., soft-Dice coefficient between predicted and ground-truth segmentations). We also quantified axon counts, axon density, and axon size distributions between hypertensive and control eyes and compared to literature reports. Results AxoNet 2.0 performed very well when compared to manual annotations of rat ON (R2 = 0.92 for automated vs. manual counts, soft-Dice coefficient = 0.81 ± 0.02, mean absolute percentage error in axonal morphometric outcomes < 15%). AxoNet 2.0 also showed promise for generalization, performing well on other animal models (R2 = 0.97 between automated versus manual counts for mice and 0.98 for non-human primates). As expected, the algorithm detected decreased in axon density in hypertensive rat eyes (P ≪ 0.001) with preferential loss of large axons (P < 0.001). Conclusions AxoNet 2.0 provides a fast and nonsubjective tool to quantify both RGC axon counts and morphological features, thus assisting with assessing axonal damage in animal models of glaucomatous optic neuropathy. Translational Relevance This deep learning approach will increase rigor of basic science studies designed to investigate RGC axon protection and regeneration.
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Affiliation(s)
- Vidisha Goyal
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - A. Thomas Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Matthew D. Ritch
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Bailey G. Hannon
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Gabriela Sanchez Rodriguez
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Dillon M. Brown
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Andrew J. Feola
- Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, USA
- Department of Ophthalmology, Emory University, Atlanta, GA, USA
| | - Adam Hedberg-Buenz
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, USA
- Iowa City VA Health Care System and Iowa City VA Center for the Prevention and Treatment of Visual Loss, Iowa City, IA, USA
| | - Grant A. Cull
- Devers Eye Institute, Legacy Research Institute, Portland, OR, USA
| | - Juan Reynaud
- Devers Eye Institute, Legacy Research Institute, Portland, OR, USA
| | - Mona K. Garvin
- Devers Eye Institute, Legacy Research Institute, Portland, OR, USA
- Department of Electrical and Computer Engineering, University of Iowa, Iowa City, IA, USA
| | - Michael G. Anderson
- Department of Molecular Physiology and Biophysics, University of Iowa, Iowa City, IA, USA
- Iowa City VA Health Care System and Iowa City VA Center for the Prevention and Treatment of Visual Loss, Iowa City, IA, USA
| | | | - C. Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- Department of Ophthalmology, Emory University, Atlanta, GA, USA
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Sayah DN, Lesk MR. Ocular Rigidity and Current Therapy. Curr Eye Res 2023; 48:105-113. [PMID: 35763027 DOI: 10.1080/02713683.2022.2093380] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Purpose: Ocular rigidity (OR) is an important biomechanical parameter of the eye accounting for the material and geometrical properties of the corneoscleral shell.Methods: This study used a literature search to review the role of ocular rigidity and the application of potential therapies targeting this parameter in glaucoma and myopia.Conclusion: Biomechanical modeling and improved understanding of the biochemistry, and molecular arrangement of sclera and its constituents have yielded important insights. Recent developments, including that of a non-invasive and direct OR measurement method and improved ocular imaging techniques are helping to elucidate the role of OR in healthy and diseased eyes by facilitating large scale and longitudinal clinical studies. Improved understanding of OR at the initial stages of disease processes and its alterations with disease progression will undoubtedly propel research in the field. Furthermore, a better understanding of the determinants of OR is helping to refine novel therapeutic approaches which target and alter the biomechanical properties of the sclera in sight-threatening conditions such as glaucoma and myopia.
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Affiliation(s)
- Diane N Sayah
- Maisonneuve-Rosemont Hospital Research Center, Montreal, Canada.,School of Optometry, Université de Montréal, Montreal, Canada
| | - Mark R Lesk
- Maisonneuve-Rosemont Hospital Research Center, Montreal, Canada.,Department of Ophthalmology, Faculty of Medicine, Université de Montréal, Montreal, Canada.,Centre Universitaire d'ophtalmologie de l'Université de Montréal de l'Hôpital Maisonneuve-Rosemont, CIUSSS-E, Montreal, Canada
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Xia M, Zhang E, Yao F, Xia Z, Zhou M, Ran X, Xia X. Regional differences of the sclera in the ocular hypertensive rat model induced by circumlimbal suture. EYE AND VISION (LONDON, ENGLAND) 2023; 10:2. [PMID: 36597143 PMCID: PMC9811703 DOI: 10.1186/s40662-022-00319-w] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 11/15/2022] [Indexed: 01/05/2023]
Abstract
PURPOSE To describe the regional differences of the sclera in ocular hypertension (OHT) models with the inappropriate extension of the ocular axis. METHODS To discover the regional differences of the sclera at the early stage, OHT models were established using circumlimbal suture (CS) or sclerosant injection (SI). Axial length (AL) was measured by ultrasound and magnetic resonance imaging. The glaucoma-associated distinction was determined by intraocular pressure (IOP) and retrograde tracing of retinal ganglion cells (RGCs). The central thickness of the ganglion cell complex (GCC) was measured by optical coherence tomography. RGCs and collagen fibrils were detected using a transmission electron microscope, furthermore, anti-alpha smooth muscle actin (αSMA) was determined in the early stage after the operation. RESULTS Compared with the control group, the eyes in OHT models showed an increased IOP (P < 0.001 in the CS group, P = 0.001 in the SI group), growing AL (P = 0.026 in the CS group, P = 0.043 in the SI group), reduction of central RGCs (P < 0.001 in the CS group, P = 0.017 in the SI group), thinning central GCC (P < 0.001 in the CS group), and a distinctive expression of αSMA in the central sclera in the early 4-week stage after the operation (P = 0.002 in the CS group). Compared with the SI group, the eye in the CS group showed a significantly increased AL (7.1 ± 0.4 mm, P = 0.031), reduction of central RGCs (2121.1 ± 87.2 cells/mm2, P = 0.001), thinning central GCC (71.4 ± 0.8 pixels, P = 0.015), and a distinctive expression of αSMA (P = 0.005). Additionally, ultrastructural changes in RGCs, scleral collagen fibers, and collagen crimp were observed in the different regions. Increased collagen volume fraction in the posterior segment of the eyeball wall (30.2 ± 3.1%, P = 0.022) was observed by MASSON staining in the CS group. CONCLUSION Regional differences of the sclera in the ocular hypertensive rat model induced by CS may provide a reference for further treatment of scleral-related eye disorders.
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Affiliation(s)
- Mingfang Xia
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.469519.60000 0004 1758 070XDepartment of Ophthalmology, People’s Hospital of Ningxia Hui Autonomous Region, Yinchuan, 750004 Ningxia China
| | - Endong Zhang
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan China
| | - Fei Yao
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan China
| | - Zhaohua Xia
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan China
| | - Mingmin Zhou
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan China
| | - Xufang Ran
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan China
| | - Xiaobo Xia
- grid.216417.70000 0001 0379 7164Eye Center of Xiangya Hospital, Central South University, Changsha, 410008 Hunan China ,grid.452223.00000 0004 1757 7615Hunan Key Laboratory of Ophthalmology, Changsha, 410008 Hunan China ,grid.216417.70000 0001 0379 7164National Clinical Research Center for Geriatric Disorders, Xiangya Hospital, Central South University, Changsha, 410008 Hunan China
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Yang Q, Lv S, Zhu H, Zhang L, Li H, Song S. A Potential Research Target for Scleral Remodeling: Effect of MiR-29a on Scleral Fibroblasts. Ophthalmic Res 2022; 65:566-574. [PMID: 35605595 DOI: 10.1159/000525189] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 05/06/2022] [Indexed: 11/19/2022]
Abstract
INTRODUCTION The purpose of this study was to determine whether miR-29a regulates cell survival and apoptosis and the expression of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), MMP-2, and collagen I in scleral fibroblasts. METHODS We transfected scleral fibroblasts with the miR-29a mimic and inhibitor. The effects of miR-29a on cell proliferation and apoptosis were determined using the CCK-8 assay and flow cytometry, respectively. Quantitative polymerase chain reaction (qPCR) was used to determine whether miR-29a regulates the mRNA levels of PTEN, MMP-2, and collagen I. The protein expression of PTEN, MMP-2, and collagen I was also assessed by western blot analysis. RESULTS The results of CCK-8 showed that, at 0, 24, 48, and 72 h after transfection, the relative optical density values in the mimic group were 0.233 ± 0.005, 0.380 ± 0.008, 0.650 ± 0.040, and 0.906 ± 0.032, and in the inhibitor group were 0.272 ± 0.011, 0.393 ± 0.029, 0.597 ± 0.059, and 0.950 ± 0.101, respectively. The flow cytometry results showed that the apoptosis rates of each group were as follows: the mimic group (0.043 ± 0.007), the NC group (0.040 ± 0.006), the inhibitor group (0.032 ± 0.003), the inhibitor NC group (0.027 ± 0.010), the lipofectamine group (0.027 ± 0.005), and the blank group (0.031 ± 0.009). The qPCR results indicated that in the mimic group, PTEN (0.795 ± 0.182, p = 0.2783), MMP-2 (0.621 ± 0.105, p = 0.0033), and COL1A1 (0.271 ± 0.100, p = 0.0002) expression decreased, whereas in the inhibitor group, PTEN (1.211 ± 0.100, p = 0.2614), MMP-2 (1.161 ± 0.053, p = 0.1190), and COL1A1 (1.7040 ± 0.093, p = 0.0003) increased. Western blot analysis showed that in the mimic group, the expression of PTEN (0.392 ± 0.039, p < 0.0001), MMP-2 (0.577 ± 0.017, p < 0.0001), and COL1A1 (0.072 ± 0.006, p < 0.0001) protein decreased, whereas in the inhibitor group, PTEN (1.043 ± 0.042, p = 0.9413), MMP-2 (1.397 ± 0.075, p = 0.0002), and COL1A1 (1.935 ± 0.081, p < 0.0001) expression increased. CONCLUSION MiR-29a inhibits the expression of PTEN, MMP-2, and collagen I on scleral fibroblasts, which may provide a basis studies in sclera.
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Affiliation(s)
- Qianying Yang
- Department of Ophthalmology, Yongchuan Hospital of Chongqing Medical University, Chongqing, China,
| | - Sha Lv
- Department of Ophthalmology, Yongchuan Hospital of Chongqing Medical University, Chongqing, China
| | - Huirong Zhu
- Department of Ophthalmology, Yongchuan Hospital of Chongqing Medical University, Chongqing, China
| | - Liming Zhang
- Department of Ophthalmology, Yongchuan Hospital of Chongqing Medical University, Chongqing, China
| | - Hua Li
- Department of Ophthalmology, Yongchuan Hospital of Chongqing Medical University, Chongqing, China
| | - Shengfang Song
- Department of Ophthalmology, Yongchuan Hospital of Chongqing Medical University, Chongqing, China
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Gerberich BG, Hannon BG, Brown DM, Read AT, Ritch MD, Schrader Echeverri E, Nichols L, Potnis C, Sridhar S, Toothman MG, Schwaner SA, Winger EJ, Huang H, Gershon GS, Feola AJ, Pardue MT, Prausnitz MR, Ethier CR. Evaluation of Spatially Targeted Scleral Stiffening on Neuroprotection in a Rat Model of Glaucoma. Transl Vis Sci Technol 2022; 11:7. [PMID: 35536721 PMCID: PMC9100482 DOI: 10.1167/tvst.11.5.7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Accepted: 03/14/2022] [Indexed: 11/25/2022] Open
Abstract
Purpose Scleral stiffening may protect against glaucomatous retinal ganglion cell (RGC) loss or dysfunction associated with ocular hypertension. Here, we assess the potential neuroprotective effects of two treatments designed to stiffen either the entire posterior sclera or only the sclera adjacent to the peripapillary sclera in an experimental model of glaucoma. Methods Rat sclerae were stiffened in vivo using either genipin (crosslinking the entire posterior sclera) or a regionally selective photosensitizer, methylene blue (stiffening only the juxtaperipapillary region surrounding the optic nerve). Ocular hypertension was induced using magnetic microbeads delivered to the anterior chamber. Morphological and functional outcomes, including optic nerve axon count and appearance, retinal thickness measured by optical coherence tomography, optomotor response, and electroretinography traces, were assessed. Results Both local (juxtaperipapillary) and global (whole posterior) scleral stiffening treatments were successful at increasing scleral stiffness, but neither provided demonstrable neuroprotection in hypertensive eyes as assessed by RGC axon counts and appearance, optomotor response, or electroretinography. There was a weak indication that scleral crosslinking protected against retinal thinning as assessed by optical coherence tomography. Conclusions Scleral stiffening was not demonstrated to be neuroprotective in ocular hypertensive rats. We hypothesize that the absence of benefit may in part be due to RGC loss associated with the scleral stiffening agents themselves (mild in the case of genipin, and moderate in the case of methylene blue), negating any potential benefit of scleral stiffening. Translational Relevance The development of scleral stiffening as a neuroprotective treatment will require the identification of better tolerated stiffening protocols and further preclinical testing.
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Affiliation(s)
- Brandon G. Gerberich
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Bailey G. Hannon
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Dillon M. Brown
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - A. Thomas Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Matthew D. Ritch
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Elisa Schrader Echeverri
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Lauren Nichols
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Cahil Potnis
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veteran Affairs Healthcare System, Atlanta, GA, USA
| | - Sreesh Sridhar
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Maya G. Toothman
- College of Sciences, Georgia Institute of Technology, Atlanta, GA, USA
| | - Stephen A. Schwaner
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
- Exponent, Inc., Biomechanics Practice, Atlanta, GA, USA
| | - Erin J. Winger
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Hannah Huang
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Gabby S. Gershon
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Andrew J. Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veteran Affairs Healthcare System, Atlanta, GA, USA
| | - Machelle T. Pardue
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- Center for Visual and Neurocognitive Rehabilitation, Atlanta Veteran Affairs Healthcare System, Atlanta, GA, USA
| | - Mark R. Prausnitz
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - C. Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
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Hamdaoui ME, Levy AM, Stuber AB, Girkin CA, Kraft TW, Samuels BC, Grytz R. Scleral crosslinking using genipin can compromise retinal structure and function in tree shrews. Exp Eye Res 2022; 219:109039. [PMID: 35339475 DOI: 10.1016/j.exer.2022.109039] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2022] [Revised: 03/08/2022] [Accepted: 03/13/2022] [Indexed: 01/29/2023]
Abstract
Scleral crosslinking using genipin has been identified as a promising treatment approach for myopia control. The efficacy of genipin to alter biomechanical properties of the sclera has been shown in several animal models of myopia but its safety profile remains unclear. In this safety study, we aim to investigate the effect of scleral crosslinking using retrobulbar injections of genipin on retinal structure and function at genipin doses that were shown to be effective in slowing myopia progression in juvenile tree shrews. To this end, three or five retrobulbar injections of genipin at 0 mM (sham), 10 mM, or 20 mM were performed in one eye every other day. Form deprivation myopia was induced in the injected eye. We quantified retinal function changes using full-field electroretinography and retinal structure changes using in vivo optical coherence tomography imaging and ex vivo histology. The optical coherence tomography results revealed significant thinning of the peripapillary retinal nerve fiber layer in all genipin treated groups including the lowest dose group, which showed no significant treatment effect in slowing myopia progression. In contrast, inducing form deprivation myopia alone and in combination with sham injections caused no obvious thinning of the retinal nerve fiber layer. Electroretinography results showed a significant desensitizing shift of the b-wave semi-saturation constant in the sham group and the second highest genipin dose group, and a significant reduction in b-wave maxima in the two highest genipin dose groups. The ex vivo histology revealed noticeable degeneration of photoreceptors and retinal pigment epithelium in one of two investigated eyes of the highest genipin dose group. While scleral crosslinking using genipin may still be a feasible treatment option for myopia control, our results suggest that repeated retrobulbar injections of genipin at 10 mM or higher are not safe in tree shrews. An adequate and sustained delivery strategy of genipin at lower concentrations will be needed to achieve a safe and effective scleral crosslinking treatment for myopia control in tree shrews. Caution should be taken if the proposed treatment approach is translated to humans.
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Affiliation(s)
- Mustapha El Hamdaoui
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Alexander M Levy
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Aaron B Stuber
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Christopher A Girkin
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Timothy W Kraft
- Department of Optometry and Vision Science, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Brian C Samuels
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA
| | - Rafael Grytz
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, AL, USA.
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Mendez-Martinez S, Martínez-Rincón T, Subias M, Pablo LE, García-Herranz D, Feijoo JG, Bravo-Osuna I, Herrero-Vanrell R, Garcia-Martin E, Rodrigo MJ. Influence of Chronic Ocular Hypertension on Emmetropia: Refractive, Structural and Functional Study in Two Rat Models. J Clin Med 2021; 10:jcm10163697. [PMID: 34441992 PMCID: PMC8397123 DOI: 10.3390/jcm10163697] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2021] [Revised: 08/11/2021] [Accepted: 08/17/2021] [Indexed: 12/29/2022] Open
Abstract
Chronic ocular hypertension (OHT) influences on refraction in youth and causes glaucoma in adulthood. However, the origin of the responsible mechanism is unclear. This study analyzes the effect of mild-moderate chronic OHT on refraction and neuroretina (structure and function) in young-adult Long-Evans rats using optical coherence tomography and electroretinography over 24 weeks. Data from 260 eyes were retrospectively analyzed in two cohorts: an ocular normotension (ONT) cohort (<20 mmHg) and an OHT cohort (>20 mmHg), in which OHT was induced either by sclerosing the episcleral veins (ES group) or by injecting microspheres into the anterior chamber. A trend toward emmetropia was found in both cohorts over time, though it was more pronounced in the OHT cohort (p < 0.001), especially in the ES group (p = 0.001) and males. IOP and refraction were negatively correlated at week 24 (p = 0.010). The OHT cohort showed early thickening in outer retinal sectors (p < 0.050) and the retinal nerve fiber layer, which later thinned. Electroretinography demonstrated early supranormal amplitudes and faster latencies that later declined. Chronic OHT accelerates emmetropia in Long–Evans rat eyes towards slowly progressive myopia, with an initial increase in structure and function that reversed over time.
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Affiliation(s)
- Silvia Mendez-Martinez
- Department of Ophthalmology, Miguel Servet University Hospital, 50009 Zaragoza, Spain; (T.M.-R.); (M.S.); (L.E.P.); (E.G.-M.); (M.J.R.)
- Miguel Servet Ophthalmology Research Group (GIMSO), Aragon Health Research Institute (IIS Aragon), 50009 Zaragoza, Spain
- Correspondence: ; Tel.: +34-9-7676-5558
| | - Teresa Martínez-Rincón
- Department of Ophthalmology, Miguel Servet University Hospital, 50009 Zaragoza, Spain; (T.M.-R.); (M.S.); (L.E.P.); (E.G.-M.); (M.J.R.)
- Miguel Servet Ophthalmology Research Group (GIMSO), Aragon Health Research Institute (IIS Aragon), 50009 Zaragoza, Spain
| | - Manuel Subias
- Department of Ophthalmology, Miguel Servet University Hospital, 50009 Zaragoza, Spain; (T.M.-R.); (M.S.); (L.E.P.); (E.G.-M.); (M.J.R.)
- Miguel Servet Ophthalmology Research Group (GIMSO), Aragon Health Research Institute (IIS Aragon), 50009 Zaragoza, Spain
| | - Luis E. Pablo
- Department of Ophthalmology, Miguel Servet University Hospital, 50009 Zaragoza, Spain; (T.M.-R.); (M.S.); (L.E.P.); (E.G.-M.); (M.J.R.)
- Miguel Servet Ophthalmology Research Group (GIMSO), Aragon Health Research Institute (IIS Aragon), 50009 Zaragoza, Spain
- National Ocular Pathology Network (OFTARED), Carlos III Health Institute, 28040 Madrid, Spain; (J.G.F.); (I.B.-O.); (R.H.-V.)
| | - David García-Herranz
- Innovation, Therapy and Pharmaceutical Development in Ophthalmology (InnOftal) Research Group, UCM 920415 Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Complutense University of Madrid, 28040 Madrid, Spain;
- Health Research Institute, San Carlos Clinical Hospital (IdISSC), 28040 Madrid, Spain
- University Institute for Industrial Pharmacy (IUFI), School of Pharmacy, Complutense University of Madrid, 28040 Madrid, Spain
| | - Julian García Feijoo
- National Ocular Pathology Network (OFTARED), Carlos III Health Institute, 28040 Madrid, Spain; (J.G.F.); (I.B.-O.); (R.H.-V.)
- Department of Ophthalmology, San Carlos Clinical Hospital (IdISSC), Complutense University of Madrid, 28040 Madrid, Spain
| | - Irene Bravo-Osuna
- National Ocular Pathology Network (OFTARED), Carlos III Health Institute, 28040 Madrid, Spain; (J.G.F.); (I.B.-O.); (R.H.-V.)
- Innovation, Therapy and Pharmaceutical Development in Ophthalmology (InnOftal) Research Group, UCM 920415 Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Complutense University of Madrid, 28040 Madrid, Spain;
- Health Research Institute, San Carlos Clinical Hospital (IdISSC), 28040 Madrid, Spain
| | - Rocío Herrero-Vanrell
- National Ocular Pathology Network (OFTARED), Carlos III Health Institute, 28040 Madrid, Spain; (J.G.F.); (I.B.-O.); (R.H.-V.)
- Innovation, Therapy and Pharmaceutical Development in Ophthalmology (InnOftal) Research Group, UCM 920415 Department of Pharmaceutics and Food Technology, Faculty of Pharmacy, Complutense University of Madrid, 28040 Madrid, Spain;
- Health Research Institute, San Carlos Clinical Hospital (IdISSC), 28040 Madrid, Spain
| | - Elena Garcia-Martin
- Department of Ophthalmology, Miguel Servet University Hospital, 50009 Zaragoza, Spain; (T.M.-R.); (M.S.); (L.E.P.); (E.G.-M.); (M.J.R.)
- Miguel Servet Ophthalmology Research Group (GIMSO), Aragon Health Research Institute (IIS Aragon), 50009 Zaragoza, Spain
- National Ocular Pathology Network (OFTARED), Carlos III Health Institute, 28040 Madrid, Spain; (J.G.F.); (I.B.-O.); (R.H.-V.)
| | - María J. Rodrigo
- Department of Ophthalmology, Miguel Servet University Hospital, 50009 Zaragoza, Spain; (T.M.-R.); (M.S.); (L.E.P.); (E.G.-M.); (M.J.R.)
- Miguel Servet Ophthalmology Research Group (GIMSO), Aragon Health Research Institute (IIS Aragon), 50009 Zaragoza, Spain
- National Ocular Pathology Network (OFTARED), Carlos III Health Institute, 28040 Madrid, Spain; (J.G.F.); (I.B.-O.); (R.H.-V.)
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9
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Park SA, Komáromy AM. Biomechanics of the optic nerve head and sclera in canine glaucoma: A brief review. Vet Ophthalmol 2021; 24:316-325. [PMID: 34402566 DOI: 10.1111/vop.12923] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2020] [Revised: 06/04/2021] [Accepted: 07/25/2021] [Indexed: 01/17/2023]
Abstract
Glaucoma is a leading cause of irreversible blindness, a progressive optic neuropathy with retinal ganglion cell (RGC) death beginning in the optic nerve head (ONH). A primary risk factor for developing glaucoma is elevated intraocular pressure (IOP). Reducing IOP is the only treatment proven to be effective at delaying disease progression. Nevertheless, even when patients have their IOP reduced, the majority of them continue to lose vision. There are, in both humans and dogs, significant interindividual variabilities in susceptibilities to IOP-induced optic nerve damage. Vision loss progresses much more slowly in Beagles with open-angle glaucoma (OAG) caused by ADAMTS10 mutation. This can be attributed to the mutation-related altered ocular biomechanical properties. The principal site of optic nerve (ON) damage in glaucoma is the ONH. It is suggested that the biomechanical properties of the ONH and the surrounding peripapillary sclera (PPS) contribute to glaucoma development and progression. As far as the beneficial biomechanical properties of the ONH and PPS for a decreased susceptibility and slow progression of glaucoma, data are inconsistent and conflicting. Recent biomechanical studies on beagles with ADAMTS10 mutation demonstrated that the mutant dogs have mechanically weak posterior sclera. This weakness was associated with a reduced collagen density and a lower proportion of insoluble collagen. These changes, observed before glaucoma development, were considered intrinsic characteristics caused by the mutation rather than a secondary effect of IOP elevation. Further studies of ADAMTS10-OAG may elucidate the effects of altered biomechanical properties of ONH and PPS in determining the glaucoma progression.
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Affiliation(s)
- Shin Ae Park
- Department of Veterinary Clinical Sciences, College of Veterinary Medicine, Purdue University, West Lafayette, Indiana, USA
| | - András M Komáromy
- Department of Small Animal Clinical Sciences, College of Veterinary Medicine, Michigan State University, East Lansing, Michigan, USA
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10
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Wang M, Corpuz CCC, Zhang F. Shaping Eyeballs by Scleral Collagen Cross-Linking: A Hypothesis for Myopia Treatment. Front Med (Lausanne) 2021; 8:655822. [PMID: 34277654 PMCID: PMC8282923 DOI: 10.3389/fmed.2021.655822] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 06/08/2021] [Indexed: 11/13/2022] Open
Abstract
The global prevalence of myopia has brought to the attention of the different eye and vision specialists, who make way to control its progression. Evidence have shown that a proactive reshaping of the eyeball is the core point of myopia developing process, which particularly includes the weakening, thinning, and expanding of the sclera. Thus, the sclera is considered to be a prime target for therapeutic manipulation in halting progressive myopia. In the past decades, corneal collagen cross-linking has been applied in clinical practice for treating aberrant corneal remodeling diseases. In this article, we hypothesize that scleral collagen cross-linking (SXL) has a huge potential in stabilizing myopic process by shaping the eyeball and preventing the aberrant scleral remodeling. In contrast with the current methods of optometry correction, such as physiotherapy, pharmacotherapy, spectacles, contact lenses, refractive surgeries, etc., eyeball-shaping method using SXL is a fundamental intervention which aims at the pathogenesis of progressive visual loss of myopia. Compared with the current posterior scleral reinforcement, the most advantage of SXL is that there is no allotransplant into the myopic eye, which means less expenditure, lower risk, and easier to handle in operating.
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Affiliation(s)
- Mengmeng Wang
- Hebei Ophthalmology Key Lab, Hebei Eye Hospital, Xingtai, China
| | | | - Fengju Zhang
- Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
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11
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Blackburn BJ, Rollins AM, Dupps WJ. Biomechanics of Ophthalmic Crosslinking. Transl Vis Sci Technol 2021; 10:8. [PMID: 34328498 PMCID: PMC8327749 DOI: 10.1167/tvst.10.5.8] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2021] [Accepted: 06/19/2021] [Indexed: 12/12/2022] Open
Abstract
Crosslinking involves the formation of bonds between polymer chains, such as proteins. In biological tissues, these bonds tend to stiffen the tissue, making it more resistant to mechanical degradation and deformation. In ophthalmology, the crosslinking phenomenon is being increasingly harnessed and explored as a treatment strategy for treating corneal ectasias, keratitis, degenerative myopia, and glaucoma. This review surveys the multitude of exogenous crosslinking strategies reported in the literature, both "light" (involving light energy) and "dark" (involving non-photic chemical processes), and explores their mechanisms, cytotoxicity, and stage of translational development. The spectrum of ophthalmic applications described in the literature is then discussed, with particular attention to proposed therapeutic mechanisms in the cornea and sclera. The mechanical effects of crosslinking are then discussed in the context of their proposed site and scale of action. Biomechanical characterization of the crosslinking effect is needed to more thoroughly address knowledge gaps in this area, and a review of reported methods for biomechanical characterization is presented with an attempt to assess the sensitivity of each method to crosslinking-mediated changes using data from the experimental and clinical literature. Biomechanical measurement methods differ in spatial resolution, mechanical sensitivity, suitability for detecting crosslinking subtypes, and translational readiness and are central to the effort to understand the mechanistic link between crosslinking methods and clinical outcomes of candidate therapies. Data on differences in the biomechanical effect of different crosslinking protocols and their correspondence to clinical outcomes are reviewed, and strategies for leveraging measurement advances predicting clinical outcomes of crosslinking procedures are discussed. Advancing the understanding of ophthalmic crosslinking, its biomechanical underpinnings, and its applications supports the development of next-generation crosslinking procedures that optimize therapeutic effect while reducing complications.
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Affiliation(s)
- Brecken J. Blackburn
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - Andrew M. Rollins
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
| | - William J. Dupps
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, USA
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, OH, USA
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, USA
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12
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El Hamdaoui M, Levy AM, Gaonkar M, Gawne TJ, Girkin CA, Samuels BC, Grytz R. Effect of Scleral Crosslinking Using Multiple Doses of Genipin on Experimental Progressive Myopia in Tree Shrews. Transl Vis Sci Technol 2021; 10:1. [PMID: 34003978 PMCID: PMC8088221 DOI: 10.1167/tvst.10.5.1] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2020] [Accepted: 02/07/2021] [Indexed: 02/06/2023] Open
Abstract
Purpose To evaluate the effect of scleral crosslinking (SXL) on slowing experimental progressive myopia in tree shrew eyes using sub-Tenon's injections of genipin (GEN) at different concentrations and number of injections. Methods Three or five sub-Tenon's injections of GEN at 0 mM (sham), 10 mM, or 20 mM were performed in one eye every other day starting at 18 days of visual experience. Form deprivation (FD) myopia was induced in the injected eye between 24 and 35 days of visual experience; the fellow eye served as control. Tree shrews were randomly assigned to five experimental groups: FD (n = 8); FD + 5 × sham injections (n = 6); FD + 3 × GEN injections at 10 mM (n = 6) and 20 mM (n = 6); and FD + 5 × GEN injections at 20 mM (n = 6). Refractive state and ocular dimensions were measured daily. Results Compared with the FD group, the sham-injected group showed a transient effect on slowing vitreous chamber elongation. With increasing GEN dose, SXL had an increasing treatment effect on slowing vitreous chamber elongation and myopia progression. In addition, SXL led to a dose-dependent shortening of the aqueous chamber depth and corneal thickening. Lens thickening was observed in the group with the highest concentration. Conclusions We have shown that SXL using GEN can slow axial elongation and myopia progression in tree shrews. The extent of this treatment effect was dose dependent. Several unexpected effects were observed (corneal thickening, decrease of the anterior chamber depth, and lens thickening), which require further optimization of the GEN delivery approach before clinical consideration. Translational Relevance The results of this preclinical study suggest that scleral crosslinking using genipin can slow myopia progression.
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Affiliation(s)
- Mustapha El Hamdaoui
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Alexander M. Levy
- Department of Biomedical Engineering, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Mokshad Gaonkar
- Department of Biostatistics, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Timothy J. Gawne
- Department of Optometry and Vision Science, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Christopher A. Girkin
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Brian C. Samuels
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - Rafael Grytz
- Department of Ophthalmology and Visual Sciences, The University of Alabama at Birmingham, Birmingham, Alabama, USA
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13
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Gerberich BG, Hannon BG, Hejri A, Winger EJ, Schrader Echeverri E, Nichols LM, Gersch HG, MacLeod NA, Gupta S, Read AT, Ritch MD, Sridhar S, Toothman MG, Gershon GS, Schwaner SA, Sánchez-Rodríguez G, Goyal V, Toporek AM, Feola AJ, Grossniklaus HE, Pardue MT, Ethier CR, Prausnitz MR. Transpupillary collagen photocrosslinking for targeted modulation of ocular biomechanics. Biomaterials 2021; 271:120735. [PMID: 33721571 PMCID: PMC8044034 DOI: 10.1016/j.biomaterials.2021.120735] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2020] [Revised: 02/15/2021] [Accepted: 02/21/2021] [Indexed: 12/21/2022]
Abstract
The central vision-threatening event in glaucoma is dysfunction and loss of retinal ganglion cells (RGCs), thought to be promoted by local tissue deformations. Here, we sought to reduce tissue deformation near the optic nerve head by selectively stiffening the peripapillary sclera, i.e. the scleral region immediately adjacent to the optic nerve head. Previous scleral stiffening studies to treat glaucoma or myopia have used either pan-scleral stiffening (not regionally selective) or regionally selective stiffening with limited access to the posterior globe. We present a method for selectively stiffening the peripapillary sclera using a transpupillary annular light beam to activate methylene blue administered by retrobulbar injection. Unlike prior approaches to photocrosslinking in the eye, this approach avoids the damaging effects of ultraviolet light by employing red light. This targeted photocrosslinking approach successfully stiffened the peripapillary sclera at 6 weeks post-treatment, as measured by whole globe inflation testing. Specifically, strain was reduced by 47% when comparing treated vs. untreated sclera within the same eye (n = 7, p=0.0064) and by 54% when comparing the peripapillary sclera of treated vs. untreated eyes (n = 7, p<0.0001). Post-treatment characterization of RGCs (optic nerve axon counts/density, and grading), retinal function (electroretinography), and retinal histology revealed that photocrosslinking was associated with some ocular toxicity. We conclude that a transpupillary photocrosslinking approach enables selective scleral stiffening targeted to the peripapillary region that may be useful in future treatments of glaucoma.
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Affiliation(s)
- B G Gerberich
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - B G Hannon
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - A Hejri
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - E J Winger
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - E Schrader Echeverri
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - L M Nichols
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - H G Gersch
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - N A MacLeod
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - S Gupta
- Daniel Guggenheim School of Aerospace Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - A T Read
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - M D Ritch
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - S Sridhar
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - M G Toothman
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - G S Gershon
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - S A Schwaner
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - G Sánchez-Rodríguez
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - V Goyal
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - A M Toporek
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - A J Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, USA
| | - H E Grossniklaus
- Winship Cancer Institute of Emory University, Atlanta, GA, USA; Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA, USA
| | - M T Pardue
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; Center for Visual and Neurocognitive Rehabilitation, Atlanta VA Healthcare System, Decatur, GA, USA
| | - C R Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
| | - M R Prausnitz
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA; School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA.
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14
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Role of radially aligned scleral collagen fibers in optic nerve head biomechanics. Exp Eye Res 2020; 199:108188. [PMID: 32805265 DOI: 10.1016/j.exer.2020.108188] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2020] [Revised: 07/22/2020] [Accepted: 08/06/2020] [Indexed: 01/04/2023]
Abstract
Collagen fibers organized circumferentially around the canal in the peripapillary sclera are thought to provide biomechanical support to the sensitive tissues within the optic nerve head (ONH). Recent studies have demonstrated the existence of a family of fibers in the innermost sclera organized radially from the scleral canal. Our goal was to determine the role of these radial fibers in the sensitivity of scleral canal biomechanics to acute increases in intraocular pressure (IOP). Following the same general approach of previous parametric sensitivity studies, we created nonlinear generic finite element models of a posterior pole with various combinations of radial and circumferential fibers at an IOP of 0 mmHg. We then simulated the effects of normal and elevated IOP levels (15 and 30 mmHg). We monitored four IOP-induced geometric changes: peripapillary sclera stretch, scleral canal displacement, lamina cribrosa displacement, and scleral canal expansion. In addition, we examined the radial (maximum tension) and through-thickness (maximum compression) strains within the ONH tissues. Our models predicted that: 1) radial fibers reduced the posterior displacement of the lamina, especially at elevated IOP; 2) radial fibers reduced IOP-induced radial strain within the peripapillary sclera and retinal tissue; and 3) a combination of radial and circumferential fibers maintained strains within the ONH at a level similar to those conferred by circumferential fibers alone. In conclusion, radial fibers provide support for the posterior globe, additional to that provided by circumferential fibers. Most importantly, a combination of both fiber families can better protect ONH tissues from excessive IOP-induced deformation than either alone.
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15
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Chow A, McCrea L, Kimball E, Schaub J, Quigley H, Pitha I. Dasatinib inhibits peripapillary scleral myofibroblast differentiation. Exp Eye Res 2020; 194:107999. [PMID: 32179077 DOI: 10.1016/j.exer.2020.107999] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Revised: 02/11/2020] [Accepted: 03/09/2020] [Indexed: 12/22/2022]
Abstract
Scleral fibroblast activation occurs in glaucomatous and myopic eyes. Here we perform an unbiased screen to identify kinase inhibitors that reduce fibroblast activation to diverse stimuli in vitro and to in vivo intraocular pressure (IOP) elevation. Primary cultures of peripapillary scleral (PPS) fibroblasts from two human donors were screened using a library of 80 kinase inhibitors to identify compounds that inhibit TGFβ-induced extracellular matrix (ECM) synthesis. Inhibition of myofibroblast differentiation was verified by alpha smooth muscle actin (αSMA) immunoblot and collagen contraction assay. Inhibition of IOP-induced scleral fibroblast proliferation was assessed by ELISA assay for proliferating cell nuclear antigen (PCNA). The initial screen identified 7 inhibitors as showing>80% reduction in ECM binding. Three kinase inhibitors were verified to reduce TGFβ-induced αSMA expression and cellular contractility (rottlerin, PP2, tyrphostin 9). The effect of three Src inhibitors, bosutinib, dasatinib, and SU-6656, on myofibroblast differentiation was evaluated, with only dasatinib significantly inhibiting TGFβ-induced ECM synthesis, αSMA expression, and cellular contractility at nanomolar dosages. Subconjunctival injection of dasatinib reduced IOP-induced scleral fibroblast proliferation compared to control (4.9 ± 11.1 ng/sclera with 0.1 μM versus 88.7 ± 38.6 ng/sclera in control, P < 0.0001). Dasatinib inhibits scleral myofibroblast differentiation and there is pharmacologic evidence that this inhibition is not solely due to Src-kinase inhibition.
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Affiliation(s)
- Amanda Chow
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA
| | - Liam McCrea
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA
| | - Elizabeth Kimball
- Glaucoma Center of Excellence, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA
| | - Julie Schaub
- Glaucoma Center of Excellence, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA
| | - Harry Quigley
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA; Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA; Glaucoma Center of Excellence, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA
| | - Ian Pitha
- Department of Ophthalmology, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA; Center for Nanomedicine, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA; Glaucoma Center of Excellence, The Johns Hopkins University School of Medicine, Baltimore, MD, 21287, USA.
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16
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Genipin inhibits the scleral expression of miR-29 and MMP2 and promotes COL1A1 expression in myopic eyes of guinea pigs. Graefes Arch Clin Exp Ophthalmol 2020; 258:1031-1038. [PMID: 32125507 DOI: 10.1007/s00417-020-04634-7] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 02/12/2020] [Accepted: 02/19/2020] [Indexed: 12/11/2022] Open
Abstract
PURPOSE High myopia can lead to blindness. Genipin is a collagen cross-linking agent that may be used to treat myopia. However, the mechanism of action of genipin for the treatment of myopia is unclear. This study investigated the effect of genipin on the scleral expression of the miR-29 cluster, matrix metalloproteinase 2 (MMP2), and collagen alpha1 chain of type I (COL1A1) in a guinea pig model of myopia. METHODS The model of myopia was established by treating guinea pigs with a - 8D lens on both eyes for 21 days, and eyes with a refractive error of - 6D or greater were included. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) and western blot were used to examine the mRNA and protein expression, respectively. A dual-luciferase assay was used to determine the direct targeting of the miR-29 cluster on the 3'-untranslated region (UTR) of the COL1A1 gene. RESULTS The scleral expression of miR-29a, miR-29b, and miR-29c as well as MMP2 was significantly increased, and the scleral expression of COL1A1 was significantly decreased in the myopia group. Genipin treatment reversed these effects in myopic eyes. The dual-luciferase assay showed that the luciferase activities were significantly decreased in human embryonic kidney (HEK) cells transfected with miR-29a and miR-29b, but not miR-29c, compared with those transfected with control miRNAs. CONCLUSIONS Genipin inhibits the scleral expression of the miR-29 cluster and MMP2 and promotes COL1A1 expression in a guinea pig model of myopia. Thus, genipin may promote COL1A1 expression by reducing the expression of the miR-29 cluster.
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17
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Sherwood JM, Boazak EM, Feola AJ, Parker K, Ethier CR, Overby DR. Measurement of Ocular Compliance Using iPerfusion. Front Bioeng Biotechnol 2019; 7:276. [PMID: 31709244 PMCID: PMC6823226 DOI: 10.3389/fbioe.2019.00276] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 10/01/2019] [Indexed: 11/25/2022] Open
Abstract
The pressure-volume relationship of the eye is determined by the biomechanical properties of the corneoscleral shell and is classically characterised by Friedenwald's coefficient of ocular rigidity or, alternatively, by the ocular compliance (OC), defined as dV/dP. OC is important in any situation where the volume (V) or pressure (P) of the eye is perturbed, as occurs during several physiological and pathological processes. However, accurately measuring OC is challenging, particularly in rodents. We measured OC in 24 untreated enucleated eyes from 12 C57BL/6 mice using the iPerfusion system to apply controlled pressure steps, whilst measuring the time-varying flow rate into the eye. Pressure and flow data were analysed by a “Discrete Volume” (integrating the flow trace) and “Step Response” method (fitting an analytical solution to the pressure trace). OC evaluated at 13 mmHg was similar between the two methods (Step Response, 41 [37, 46] vs. Discrete Volume, 42 [37, 48] nl/mmHg; mean [95% CI]), although the Step Response Method yielded tighter confidence bounds on individual eyes. OC was tightly correlated between contralateral eyes (R2 = 0.75, p = 0.0003). Following treatment with the cross-linking agent genipin, OC decreased by 40 [33, 47]% (p = 0.0001; N = 6, Step Response Method). Measuring OC provides a powerful tool to assess corneoscleral biomechanics in mice and other species.
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Affiliation(s)
- Joseph M Sherwood
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - Elizabeth M Boazak
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States
| | - Andrew J Feola
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.,Atlanta VA Medical Center, Atlanta, GA, United States
| | - Kim Parker
- Department of Bioengineering, Imperial College London, London, United Kingdom
| | - C Ross Ethier
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, United States.,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, United States
| | - Darryl R Overby
- Department of Bioengineering, Imperial College London, London, United Kingdom
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Hannon BG, Schwaner SA, Boazak EM, Gerberich BG, Winger EJ, Prausnitz MR, Ethier CR. Sustained scleral stiffening in rats after a single genipin treatment. J R Soc Interface 2019; 16:20190427. [PMID: 31615330 DOI: 10.1098/rsif.2019.0427] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Scleral stiffening has been proposed as a therapy for glaucoma and myopia. Previous in vivo studies have evaluated the efficacy of scleral stiffening after multiple treatments with a natural collagen crosslinker, genipin. However, multiple injections limit clinical translatability. Here, we examined whether scleral stiffening was maintained after four weeks following a single genipin treatment. Eyes from brown Norway rats were treated in vivo with a single 15 mM genipin retrobulbar injection, sham retrobulbar injection, or were left naive. Eyes were enucleated either 1 day or four weeks post-injection and underwent whole globe inflation testing. We assessed first principal Lagrange strain of the posterior sclera using digital image correlation as a proxy for scleral stiffness. Four weeks post-injection, genipin treatment resulted in a 58% reduction in scleral strain as compared to controls (p = 0.005). We conclude that a single in vivo injection of genipin effectively stiffened rat sclera for at least four weeks which motivates further functional studies and possible clinical translation of genipin-induced scleral stiffening.
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Affiliation(s)
- Bailey G Hannon
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Stephen A Schwaner
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Elizabeth M Boazak
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Brandon G Gerberich
- Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - Erin J Winger
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA
| | - Mark R Prausnitz
- School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA, USA.,Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
| | - C Ross Ethier
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, USA.,Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, Atlanta, GA, USA
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19
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Boote C, Sigal IA, Grytz R, Hua Y, Nguyen TD, Girard MJA. Scleral structure and biomechanics. Prog Retin Eye Res 2019; 74:100773. [PMID: 31412277 DOI: 10.1016/j.preteyeres.2019.100773] [Citation(s) in RCA: 139] [Impact Index Per Article: 27.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 08/07/2019] [Accepted: 08/08/2019] [Indexed: 12/18/2022]
Abstract
As the eye's main load-bearing connective tissue, the sclera is centrally important to vision. In addition to cooperatively maintaining refractive status with the cornea, the sclera must also provide stable mechanical support to vulnerable internal ocular structures such as the retina and optic nerve head. Moreover, it must achieve this under complex, dynamic loading conditions imposed by eye movements and fluid pressures. Recent years have seen significant advances in our knowledge of scleral biomechanics, its modulation with ageing and disease, and their relationship to the hierarchical structure of the collagen-rich scleral extracellular matrix (ECM) and its resident cells. This review focuses on notable recent structural and biomechanical studies, setting their findings in the context of the wider scleral literature. It reviews recent progress in the development of scattering and bioimaging methods to resolve scleral ECM structure at multiple scales. In vivo and ex vivo experimental methods to characterise scleral biomechanics are explored, along with computational techniques that combine structural and biomechanical data to simulate ocular behaviour and extract tissue material properties. Studies into alterations of scleral structure and biomechanics in myopia and glaucoma are presented, and their results reconciled with associated findings on changes in the ageing eye. Finally, new developments in scleral surgery and emerging minimally invasive therapies are highlighted that could offer new hope in the fight against escalating scleral-related vision disorder worldwide.
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Affiliation(s)
- Craig Boote
- Structural Biophysics Research Group, School of Optometry & Vision Sciences, Cardiff University, UK; Ophthalmic Engineering & Innovation Laboratory (OEIL), Department of Biomedical Engineering, National University of Singapore, Singapore; Newcastle Research & Innovation Institute Singapore (NewRIIS), Singapore.
| | - Ian A Sigal
- Laboratory of Ocular Biomechanics, Department of Ophthalmology, University of Pittsburgh, USA
| | - Rafael Grytz
- Department of Ophthalmology & Visual Sciences, University of Alabama at Birmingham, USA
| | - Yi Hua
- Laboratory of Ocular Biomechanics, Department of Ophthalmology, University of Pittsburgh, USA
| | - Thao D Nguyen
- Department of Mechanical Engineering, Johns Hopkins University, USA
| | - Michael J A Girard
- Ophthalmic Engineering & Innovation Laboratory (OEIL), Department of Biomedical Engineering, National University of Singapore, Singapore; Singapore Eye Research Institute (SERI), Singapore National Eye Centre, Singapore
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20
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Levy AM, Fazio MA, Grytz R. Experimental myopia increases and scleral crosslinking using genipin inhibits cyclic softening in the tree shrew sclera. Ophthalmic Physiol Opt 2019; 38:246-256. [PMID: 29691925 DOI: 10.1111/opo.12454] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2018] [Accepted: 03/15/2018] [Indexed: 11/30/2022]
Abstract
PURPOSE Myopia progression is thought to involve biomechanical weakening of the sclera, which leads to irreversible deformations and axial elongation of the eye. Scleral crosslinking has been proposed as a potential treatment option for myopia control by strengthening the mechanically weakened sclera. The biomechanical mechanism by which the sclera weakens during myopia and strengthens after crosslinking is not fully understood. Here, we assess the effect of lens-induced myopia and exogenous crosslinking using genipin on the inelastic mechanical properties of the tree shrew sclera measured by cyclic tensile tests. METHODS Cyclic tensile tests were performed on 2-mm wide scleral strips at physiological loading conditions (50 cycles, 0-3.3 g, 30 s cycle-1 ). Two scleral strips were obtained from each eye of juvenile tree shrews exposed to two different visual conditions: normal and 4 days of monocular -5 D lens wear to accelerate scleral remodelling and induce myopia. Scleral strips were mechanically tested at three alternative conditions: immediately after enucleation; after incubation in phosphate buffered saline (PBS) for 24 h at 37°C; and after incubation for 24 h in PBS supplemented with genipin at a low cytotoxicity concentration (0.25 mm). Cyclic softening was defined as the incremental strain increase from one cycle to the next. RESULTS -5D lens treatment significantly increased the cyclic softening response of the sclera when compared to contralateral control eyes (0.10% ± 0.029%, mean ± standard error, P = 0.037). Exogenous crosslinking of the lens treated sclera significantly decreased the cyclic softening response (-0.12% ± 0.014%, P = 2.2 × 10-5 ). Contrary to all other groups, the genipin-cross-linked tissue did not exhibit cyclic softening significantly different from zero within the 50-cycle test. CONCLUSIONS Results indicated that cyclic tensile loading leads to an inelastic, cyclic softening of the juvenile tree shrew sclera. The softening rate increased during lens-induced myopia and was diminished after genipin crosslinking. This finding suggests that axial elongation in myopia may involve a biomechanical weakening mechanism that increased the cyclic softening response of the sclera, which was inhibited by scleral crosslinking using genipin.
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Affiliation(s)
- Alexander M Levy
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, USA
| | - Massimo A Fazio
- Department of Biomedical Engineering, University of Alabama at Birmingham, Birmingham, USA.,Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, USA
| | - Rafael Grytz
- Department of Ophthalmology and Visual Sciences, University of Alabama at Birmingham, Birmingham, USA
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21
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Schwaner SA, Kight AM, Perry RN, Pazos M, Yang H, Johnson EC, Morrison JC, Burgoyne CF, Ross Ethier C. A Methodology for Individual-Specific Modeling of Rat Optic Nerve Head Biomechanics in Glaucoma. J Biomech Eng 2018; 140:2679249. [PMID: 30003249 PMCID: PMC6056184 DOI: 10.1115/1.4039998] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2018] [Revised: 04/10/2018] [Indexed: 12/20/2022]
Abstract
Glaucoma is the leading cause of irreversible blindness and involves the death of retinal ganglion cells (RGCs). Although biomechanics likely contributes to axonal injury within the optic nerve head (ONH), leading to RGC death, the pathways by which this occurs are not well understood. While rat models of glaucoma are well-suited for mechanistic studies, the anatomy of the rat ONH is different from the human, and the resulting differences in biomechanics have not been characterized. The aim of this study is to describe a methodology for building individual-specific finite element (FE) models of rat ONHs. This method was used to build three rat ONH FE models and compute the biomechanical environment within these ONHs. Initial results show that rat ONH strains are larger and more asymmetric than those seen in human ONH modeling studies. This method provides a framework for building additional models of normotensive and glaucomatous rat ONHs. Comparing model strain patterns with patterns of cellular response seen in studies using rat glaucoma models will help us to learn more about the link between biomechanics and glaucomatous cell death, which in turn may drive the development of novel therapies for glaucoma.
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Affiliation(s)
- Stephen A. Schwaner
- George W. Woodruff School of Mechanical Engineering,
Georgia Institute of Technology,
315 Ferst Drive,
2306 IBB,
Atlanta, GA 30332
e-mail:
| | - Alison M. Kight
- Coulter Department of Biomedical Engineering,
Georgia Institute of Technology/Emory University,
Atlanta, GA 30332
e-mail:
| | - Robert N. Perry
- Coulter Department of Biomedical Engineering,
Georgia Institute of Technology/Emory University,
Atlanta, GA 30332
e-mail:
| | - Marta Pazos
- Institut Clínic d'Oftalmologia,
Hospital Clínic de Barcelona,
Barcelona 08036, Spain
e-mail:
| | - Hongli Yang
- Optic Nerve Head Research Laboratory,
Discoveries in Sight Research Laboratories,
Devers Eye Institute, Legacy Health System,
Portland, OR 97210
e-mail:
| | - Elaine C. Johnson
- The Kenneth C. Swan Ocular Neurobiology Laboratory,
Casey Eye Institute,
Oregon Health and Science University,
Portland, OR 97239
e-mail:
| | - John C. Morrison
- The Kenneth C. Swan Ocular Neurobiology Laboratory,
Casey Eye Institute,
Oregon Health and Science University,
Portland, OR 97239
e-mail:
| | - Claude F. Burgoyne
- Optic Nerve Head Research Laboratory,
Discoveries in Sight Research Laboratories,
Devers Eye Institute,
Legacy Health System,
Portland, OR 97210
e-mail:
| | - C. Ross Ethier
- Coulter Department of Biomedical Engineering,
Georgia Institute of Technology/Emory University,
Atlanta, GA 30332
e-mail:
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Cause and Effect Relationship between Changes in Scleral Matrix Metallopeptidase-2 Expression and Myopia Development in Mice. THE AMERICAN JOURNAL OF PATHOLOGY 2018; 188:1754-1767. [DOI: 10.1016/j.ajpath.2018.04.011] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/12/2017] [Revised: 02/21/2018] [Accepted: 04/06/2018] [Indexed: 12/29/2022]
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23
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Clayson K, Pan X, Pavlatos E, Short R, Morris H, Hart RT, Liu J. Corneoscleral stiffening increases IOP spike magnitudes during rapid microvolumetric change in the eye. Exp Eye Res 2017; 165:29-34. [PMID: 28864177 DOI: 10.1016/j.exer.2017.08.015] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 07/17/2017] [Accepted: 08/23/2017] [Indexed: 12/16/2022]
Abstract
Factors governing the steady-state IOP have been extensively studied; however, the dynamic aspects of IOP are less understood. Clinical studies have suggested that intraocular pressure (IOP) fluctuation may be associated with glaucoma risk. This study aims to investigate how stiffening of corneoscleral biomechanical properties affects IOP spikes induced by rapid microvolumetric change. Porcine eyes (n = 25 in total) were subjected to volumetric infusions before and after external treatment of a circular area (11 mm diameter) in either the central cornea or posterior sclera. The treated area in the control group was immersed in phosphate-buffered saline (PBS) for 40 min, while the treated area of the chemical crosslinking group was immersed in 4% glutaraldehyde/PBS for 40 min. A subset of the sham-treated eyes was also subjected to volumetric infusions at a raised steady-state IOP. The magnitude of IOP spikes increased after localized chemical crosslinking of either the cornea (27.5% increase, p < 0.001) or the sclera (14.3% increase, p < 0.001) with corneal crosslinking having a stronger effect than scleral crosslinking (p = 0.018). We also observed that raising the steady-state IOP from 15 to 25 mmHg resulted in marked increase in IOP spike magnitudes by 63.9% (p < 0.001). These results suggested that an increased corneoscleral stiffness could significantly increase IOP spike magnitudes at the same volumetric change. Corneal stiffness appeared to have a strong impact on the IOP spike magnitude and may play a major role in regulating rapid volume-pressure dynamics. An increase in steady-state IOP also resulted in larger IOP fluctuations due to the increased "apparent" stiffness of the ocular shell, suggesting a potential interaction between the magnitude of IOP and its fluctuations. Corneoscleral properties may represent additional pathways for understanding and managing glaucoma risk and warrant future investigation.
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Affiliation(s)
- Keyton Clayson
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA; Biophysics Interdisciplinary Program, Ohio State University, Columbus, OH, USA
| | - Xueliang Pan
- Center for Biostatistics, Ohio State University, Columbus, OH, USA
| | - Elias Pavlatos
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Ryan Short
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Hugh Morris
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Richard T Hart
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA
| | - Jun Liu
- Department of Biomedical Engineering, Ohio State University, Columbus, OH, USA; Biophysics Interdisciplinary Program, Ohio State University, Columbus, OH, USA; Department of Ophthalmology and Visual Science, Ohio State University, Columbus, OH, USA.
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