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Isolation and Characterization of primary human trabecular meshwork cells from segmental flow regions: New tools for understanding segmental flow. Exp Eye Res 2020; 197:108046. [PMID: 32376472 DOI: 10.1016/j.exer.2020.108046] [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: 11/25/2019] [Revised: 04/24/2020] [Accepted: 04/26/2020] [Indexed: 11/21/2022]
Abstract
Segmental flow in the human trabecular meshwork is a well-documented phenomenon but in depth mechanistic investigations of high flow (HF) and low flow (LF) regions are restricted due to the small amount of tissue available from a single donor. To address this issue we have generated and characterized multiple paired HF and LF cell strains. Here paired HF and LF cell strains were generated from single donors. Cells were characterized for growth and proliferation, as well as gene and protein expression of potential segmental region markers. Cells isolated from HF and LF regions have similar growth and proliferation rates. Gene expression data reveals vascular cell adhesion protein 1 (VCAM1), thrombospondin 2 (THBS2), and tissue inhibitor of metalloproteinase 1 (TIMP1) are potential markers of LF cells in vitro. Protein expression of VCAM1, THBS2 and TIMP1 are complex and may reflect the dynamic nature of the TM. Initial protein expression levels of these genes is either similar between HF and LF cells (VCAM1, THBS2), or higher in HF compared to LF in some strains (TIMP1). However, after long term culture LF cells express higher levels of VCAM1, TIMP1 and THBS2 protein compared to HF cells. HF and LF cell strains are a powerful new tool that enable understanding segmental flow allowing for multiple experiments on the same genetic background.
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Sherwood JM, Stamer WD, Overby DR. A model of the oscillatory mechanical forces in the conventional outflow pathway. J R Soc Interface 2020; 16:20180652. [PMID: 30958169 PMCID: PMC6364644 DOI: 10.1098/rsif.2018.0652] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Intraocular pressure is regulated by mechanosensitive cells within the conventional outflow pathway, the primary route of aqueous humour drainage from the eye. However, the characteristics of the forces acting on those cells are poorly understood. We develop a model that describes flow through the conventional outflow pathway, including the trabecular meshwork (TM) and Schlemm’s canal (SC). Accounting for the ocular pulse, we estimate the time-varying shear stress on SC endothelium and strain on the TM. We consider a range of outflow resistances spanning normotensive to hypertensive conditions. Over this range, the SC shear stress increases significantly and becomes highly oscillatory. TM strain also increases, but with negligible oscillations. Interestingly, TM strain responds more to changes in outflow resistance around physiological values, while SC shear stress responds more to elevated levels of resistance. A modest increase in TM stiffness, as observed in glaucoma, suppresses TM strain and practically eliminates the influence of outflow resistance on SC shear stress. As SC and TM cells respond to mechanical stimulation by secreting factors that modulate outflow resistance, our model provides insight regarding the potential role of SC shear and TM strain as mechanosensory cues for homeostatic regulation of outflow resistance and hence intraocular pressure.
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Affiliation(s)
- Joseph M Sherwood
- 1 Department of Bioengineering, Imperial College London , London , UK
| | - W Daniel Stamer
- 2 Department of Ophthalmology, Duke University , Durham, NC , USA
| | - Darryl R Overby
- 1 Department of Bioengineering, Imperial College London , London , UK
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53
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Experimental glaucoma model with controllable intraocular pressure history. Sci Rep 2020; 10:126. [PMID: 31924837 PMCID: PMC6954231 DOI: 10.1038/s41598-019-57022-5] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2019] [Accepted: 12/18/2019] [Indexed: 12/20/2022] Open
Abstract
Glaucoma-like neuropathies can be experimentally induced by disturbing aqueous outflow from the eye, resulting in intraocular pressure (IOP) changes that are variable in magnitude and time course and permanent in duration. This study introduces a novel method of glaucoma induction that offers researchers round-the-clock measurement and reversible control of IOP for the first time. One eye of Brown-Norway rats was implanted with a cannula tethered to a pressure sensor and aqueous reservoir. IOP was raised 10 mmHg for weeks-to-months in treated animals and unaltered in control animals. Counts of Brn3a-expressing retinal ganglion cells (RGCs) in implanted eyes were indistinguishable from non-implanted eyes in control animals and 15 ± 2%, 23 ± 4%, and 38 ± 4% lower in animals exposed to 2, 4, and 9 weeks of IOP elevation. RGC loss was greater in peripheral retina at 2 weeks and widespread at longer durations. Optic nerves also showed progressive degeneration with exposure duration, yet conventional outflow facility of implanted eyes was normal (24.1 ± 2.9 nl/min/mmHg) even after 9-weeks elevation. Hence, this infusion-based glaucoma model exhibits graded neural damage with unimpaired outflow pathways. The model further revealed a potentially-significant finding that outflow properties of rat eyes do not remodel in response to chronic ocular hypertension.
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Vahabikashi A, Gelman A, Dong B, Gong L, Cha EDK, Schimmel M, Tamm ER, Perkumas K, Stamer WD, Sun C, Zhang HF, Gong H, Johnson M. Increased stiffness and flow resistance of the inner wall of Schlemm's canal in glaucomatous human eyes. Proc Natl Acad Sci U S A 2019; 116:26555-26563. [PMID: 31806762 PMCID: PMC6936716 DOI: 10.1073/pnas.1911837116] [Citation(s) in RCA: 71] [Impact Index Per Article: 14.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The cause of the elevated outflow resistance and consequent ocular hypertension characteristic of glaucoma is unknown. To investigate possible causes for this flow resistance, we used atomic force microscopy (AFM) with 10-µm spherical tips to probe the stiffness of the inner wall of Schlemm's canal as a function of distance from the tissue surface in normal and glaucomatous postmortem human eyes, and 1-µm spherical AFM tips to probe the region immediately below the tissue surface. To localize flow resistance, perfusion and imaging methods were used to characterize the pressure drop in the immediate vicinity of the inner wall using giant vacuoles that form in Schlemm's canal cells as micropressure sensors. Tissue stiffness increased with increasing AFM indentation depth. Tissues from glaucomatous eyes were stiffer compared with normal eyes, with greatly increased stiffness residing within ∼1 µm of the inner-wall surface. Giant vacuole size and density were similar in normal and glaucomatous eyes despite lower flow rate through the latter due to their higher flow resistance. This implied that the elevated flow resistance found in the glaucomatous eyes was localized to the same region as the increased tissue stiffness. Our findings implicate pathological changes to biophysical characteristics of Schlemm's canal endothelia and/or their immediate underlying extracellular matrix as cause for ocular hypertension in glaucoma.
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Affiliation(s)
- Amir Vahabikashi
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
| | - Ariel Gelman
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Biqin Dong
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201
| | - Lihua Gong
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Elliott D. K. Cha
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Margit Schimmel
- Institute of Anatomy, University of Regensburg, D-93053 Regensburg, Germany
| | - Ernst R. Tamm
- Institute of Anatomy, University of Regensburg, D-93053 Regensburg, Germany
| | | | - W. Daniel Stamer
- Department of Ophthalmology, Duke University, Durham, NC 27710
- Department of Biomedical Engineering, Duke University, Durham, NC 27708
| | - Cheng Sun
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201
| | - Hao F. Zhang
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
- Department of Ophthalmology, Northwestern University, Chicago, IL 60611
| | - Haiyan Gong
- Department of Ophthalmology, Boston University School of Medicine, Boston, MA 02118
| | - Mark Johnson
- Department of Biomedical Engineering, Northwestern University, Evanston, IL 60201
- Department of Mechanical Engineering, Northwestern University, Evanston, IL 60201
- Department of Ophthalmology, Northwestern University, Chicago, IL 60611
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In vivo measurement of trabecular meshwork stiffness in a corticosteroid-induced ocular hypertensive mouse model. Proc Natl Acad Sci U S A 2019; 116:1714-1722. [PMID: 30651311 PMCID: PMC6358695 DOI: 10.1073/pnas.1814889116] [Citation(s) in RCA: 52] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Ocular corticosteroids are commonly used clinically. Unfortunately, their administration frequently leads to ocular hypertension, i.e., elevated intraocular pressure (IOP), which, in turn, can progress to a form of glaucoma known as steroid-induced glaucoma. The pathophysiology of this condition is poorly understood yet shares similarities with the most common form of glaucoma. Using nanotechnology, we created a mouse model of corticosteroid-induced ocular hypertension. This model functionally and morphologically resembles human ocular hypertension, having titratable, robust, and sustained IOPs caused by increased resistance to aqueous humor outflow. Using this model, we then interrogated the biomechanical properties of the trabecular meshwork (TM), including the inner wall of Schlemm's canal (SC), tissues known to strongly influence IOP and to be altered in other forms of glaucoma. Specifically, using spectral domain optical coherence tomography, we observed that SC in corticosteroid-treated mice was more resistant to collapse at elevated IOPs, reflecting increased TM stiffness determined by inverse finite element modeling. Our noninvasive approach to monitoring TM stiffness in vivo is applicable to other forms of glaucoma and has significant potential to monitor TM function and thus positively affect the clinical care of glaucoma, the leading cause of irreversible blindness worldwide.
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Xin C, Song S, Johnstone M, Wang N, Wang RK. Quantification of Pulse-Dependent Trabecular Meshwork Motion in Normal Humans Using Phase-Sensitive OCT. Invest Ophthalmol Vis Sci 2018; 59:3675-3681. [PMID: 30029254 PMCID: PMC6054426 DOI: 10.1167/iovs.17-23579] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 05/30/2018] [Indexed: 12/23/2022] Open
Abstract
Purpose The purpose of this study was to characterize the pulsatile motion of trabecular meshwork (TM) in normal subjects and demonstrate its changes in accommodation with phase-sensitive optical coherence tomography (PhS-OCT). Methods A new PhS-OCT laboratory prototype was designed to measure pulsatile TM motion in 13 healthy humans. Two sets of images were captured in 10 subjects, first with best corrective refraction and the other with an additional 3.0 diopters of accommodation. In each image, both maximum velocity (MV) and cumulative displacement (CD) in two selected regions of TM, the internal (IMV and ICD) and external (EMV and ECD) region, were measured. Results For all parameters the intraclass correlation coefficient was >0.75. Neither MV nor CD was significantly different between eyes in individual subjects (PIMV = 0.967, PEMV = 0.391, PICD = 0.603, PECD = 0.482). In 26 eyes, with best corrective refraction, the EMV was higher than the IMV (23.9 ± 9.8 vs. 18.9 ± 8.08 μm/s; P = 0.0001), as was the ECD compared with the ICD (0.340 ±0.125 vs. 0.264 ± 0.111 μm; P = 0.000004). With accommodation, MV and CD significantly increased (PIMV = 0.0003, PEMV = 0.0003, PICD = 0.019, and PECD = 0.007), whereas MV and CD in the external region were still larger than those in the internal area (PEMV vs. IMV = 0.009, PECD vs. ICD = 0.023). Conclusions This study demonstrates the differences in TM motion between the internal and external regions of TM and displays its change with accommodation. The findings and good reproducibility suggest PhS-OCT helps to understand TM function in regulation of IOP, and, with further refinements, it may be useful in clinical management of glaucoma.
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Affiliation(s)
- Chen Xin
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Shaozhen Song
- Department of Bioengineering, University of Washington, Seattle, Washington, United States
| | - Murray Johnstone
- Department of Ophthalmology, University of Washington, Seattle, Washington, United States
| | - Ningli Wang
- Beijing Institute of Ophthalmology, Beijing Tongren Eye Center, Beijing Tongren Hospital, Capital Medical University, Beijing, China
| | - Ruikang K. Wang
- Department of Bioengineering, University of Washington, Seattle, Washington, United States
- Department of Ophthalmology, University of Washington, Seattle, Washington, United States
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Yoshikawa M, Akagi T, Uji A, Nakanishi H, Kameda T, Suda K, Ikeda HO, Tsujikawa A. Pilot study assessing the structural changes in posttrabecular aqueous humor outflow pathway after trabecular meshwork surgery using swept-source optical coherence tomography. PLoS One 2018; 13:e0199739. [PMID: 29953502 PMCID: PMC6023224 DOI: 10.1371/journal.pone.0199739] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2018] [Accepted: 06/13/2018] [Indexed: 11/19/2022] Open
Abstract
This study evaluated the morphological change in aqueous humor outflow (AHO) pathways using swept-source optical coherence tomography (SS-OCT) volumetric scans in glaucoma patients before and after glaucoma surgery. In this prospective observational case series, 15 eyes (13 patients) with glaucoma were treated with 120-degree Trabectome or 360-degree suture trabeculotomy and followed up for 3 months. B-scan images of the posttrabecular AHO pathway were reconstructed and the pathway areas were evaluated, before and after surgery. Changes in posttrabecular AHO pathway were qualitatively classified as “increased”, “non-significant change”, and “decreased” on reconstructed B-scan images. Quantitative measurements of the posttrabecular AHO pathway areas were performed pre- and postoperatively. Factors associated with both qualitative and quantitative changes in AHO pathway were investigated. From 30 regions (15 nasal and 15 temporal regions) in the 15 eyes, AHO pathways were analyzable in 20 regions pre- and postoperatively. Qualitative assessments of the pathway changes were “increased” in 8 regions, “non-significant change” in 9 regions, and “decreased” in 3 regions. Quantitative assessments of the average pathway area did not change significantly (from 3155±1633 pixels preoperatively to 3212±1684 pixels postoperatively, P = 0.50). All parameters relating to intraocular pressure changes or the surgical location were not associated with postoperative AHO pathway change. The intrascleral AHO pathway could be well visualized in glaucoma patients pre- and postoperatively using swept-source optical coherence tomography. However, structural changes in the AHO pathway assessed by SS-OCT were not significant after trabecular-targeted glaucoma surgery. Functional assessments of AHO are needed in future studies.
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Affiliation(s)
- Munemitsu Yoshikawa
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Tadamichi Akagi
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
- * E-mail:
| | - Akihito Uji
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Hideo Nakanishi
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Takanori Kameda
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Kenji Suda
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Hanako Ohashi Ikeda
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
| | - Akitaka Tsujikawa
- Department of Ophthalmology and Visual Sciences, Kyoto University Graduate School of Medicine, Kyoto, Japan
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58
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Wang K, Li G, Read AT, Navarro I, Mitra AK, Stamer WD, Sulchek T, Ethier CR. The relationship between outflow resistance and trabecular meshwork stiffness in mice. Sci Rep 2018; 8:5848. [PMID: 29643342 PMCID: PMC5895808 DOI: 10.1038/s41598-018-24165-w] [Citation(s) in RCA: 46] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2017] [Accepted: 03/26/2018] [Indexed: 11/25/2022] Open
Abstract
It has been suggested that common mechanisms may underlie the pathogenesis of primary open-angle glaucoma (POAG) and steroid-induced glaucoma (SIG). The biomechanical properties (stiffness) of the trabecular meshwork (TM) have been shown to differ between POAG patients and unaffected individuals. While features such as ocular hypertension and increased outflow resistance in POAG and SIG have been replicated in mouse models, whether changes of TM stiffness contributes to altered IOP homeostasis remains unknown. We found that outer TM was stiffer than the inner TM and, there was a significant positive correlation between outflow resistance and TM stiffness in mice where conditions are well controlled. This suggests that TM stiffness is intimately involved in establishing outflow resistance, motivating further studies to investigate factors underlying TM biomechanical property regulation. Such factors may play a role in the pathophysiology of ocular hypertension. Additionally, this finding may imply that manipulating TM may be a promising approach to restore normal outflow dynamics in glaucoma. Further, novel technologies are being developed to measure ocular tissue stiffness in situ. Thus, the changes of TM stiffness might be a surrogate marker to help in diagnosing altered conventional outflow pathway function if those technologies could be adapted to TM.
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Affiliation(s)
- Ke Wang
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, 30332, United States of America
| | - Guorong Li
- Department of Ophthalmology, Duke University, Durham, North Carolina, 27708, United States of America
| | - A Thomas Read
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, 30332, United States of America
| | - Iris Navarro
- Department of Ophthalmology, Duke University, Durham, North Carolina, 27708, United States of America
| | - Ashim K Mitra
- School of Pharmacy, University of Missouri-Kansas City, Kansas City, Missouri, 64110, United States of America
| | - W Daniel Stamer
- Department of Ophthalmology, Duke University, Durham, North Carolina, 27708, United States of America
| | - Todd Sulchek
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, 30332, United States of America
| | - C Ross Ethier
- Department of Biomedical Engineering, Georgia Institute of Technology/Emory University, Atlanta, Georgia, 30332, United States of America. .,George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia, 30332, United States of America.
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