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Guimarães P, Morgado M, Batista A. On the quantitative analysis of lamellar collagen arrangement with second-harmonic generation imaging. BIOMEDICAL OPTICS EXPRESS 2024; 15:2666-2680. [PMID: 38633085 PMCID: PMC11019681 DOI: 10.1364/boe.516817] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/27/2023] [Revised: 02/23/2024] [Accepted: 02/27/2024] [Indexed: 04/19/2024]
Abstract
Second harmonic generation (SHG) allows for the examination of collagen structure in collagenous tissues. Collagen is a fibrous protein found in abundance in the human body, present in bones, cartilage, the skin, and the cornea, among other areas, providing structure, support, and strength. Its structural arrangement is deeply intertwined with its function. For instance, in the cornea, alterations in collagen organization can result in severe visual impairments. Using SHG imaging, various metrics have demonstrated the potential to study collagen organization. The discrimination between healthy, keratoconus, and crosslinked corneas, assessment of injured tendons, or the characterization of breast and ovarian tumorous tissue have been demonstrated. Nevertheless, these metrics have not yet been objectively evaluated or compared. A total of five metrics were identified and implemented from the literature, and an additional approach adapted from texture analysis was proposed. In this study, we analyzed their effectiveness on a ground-truth set of artificially generated fibrous images. Our investigation provides the first comprehensive assessment of the performance of multiple metrics, identifying both the strengths and weaknesses of each approach and providing valuable insights for future applications of SHG imaging in medical diagnostics and research.
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Affiliation(s)
- Pedro Guimarães
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal
| | - Miguel Morgado
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal
| | - Ana Batista
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, Coimbra, Portugal
- Centre for Innovative Biomedicine and Biotechnology (CIBB), Faculty of Medicine, University of Coimbra, Coimbra, Portugal
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2
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Bradford S, Luo S, Brown D, Juhasz T, Jester J. A review of the epithelial and stromal effects of corneal collagen crosslinking. Ocul Surf 2023; 30:150-159. [PMID: 37683969 PMCID: PMC10993773 DOI: 10.1016/j.jtos.2023.09.003] [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: 04/21/2023] [Revised: 08/31/2023] [Accepted: 09/05/2023] [Indexed: 09/10/2023]
Abstract
Induced corneal collagen crosslinking and mechanical stiffening via ultraviolet-A photoactivation of riboflavin (UVA CXL) is now a common treatment for corneal ectasia and Keratoconus. Some effects of the procedure such as induced mechanical stiffening, corneal flattening, and cellular toxicity are well-known, but others remain more controversial. Authors report a variety of contradictory effects, and provide evidence based on individual results and observations. A full understanding of the effects of and mechanisms behind this procedure are essential to predicting its outcome. A growing interest in modifications to the standard UVA CXL protocol, such as transepithelial or accelerated UVA CXL, makes analyzing the literature as a whole more urgent. This review presents an analysis of both the agreed-upon and contradictory results reported and the various methods used to obtain them.
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Affiliation(s)
- Samantha Bradford
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA.
| | - Shangbang Luo
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Donald Brown
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - Tibor Juhasz
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
| | - James Jester
- Department of Ophthalmology and Biomedical Engineering, University of California, Irvine, Irvine, CA, USA
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3
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Yam GHF, Pi S, Du Y, Mehta JS. Posterior corneoscleral limbus: Architecture, stem cells, and clinical implications. Prog Retin Eye Res 2023; 96:101192. [PMID: 37392960 DOI: 10.1016/j.preteyeres.2023.101192] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2023] [Revised: 06/22/2023] [Accepted: 06/23/2023] [Indexed: 07/03/2023]
Abstract
The limbus is a transition from the cornea to conjunctiva and sclera. In human eyes, this thin strip has a rich variation of tissue structures and composition, typifying a change from scleral irregularity and opacity to corneal regularity and transparency; a variation from richly vascularized conjunctiva and sclera to avascular cornea; the neural passage and drainage of aqueous humor. The limbal stroma is enriched with circular fibres running parallel to the corneal circumference, giving its unique role in absorbing small pressure changes to maintain corneal curvature and refractivity. It contains specific niches housing different types of stem cells for the corneal epithelium, stromal keratocytes, corneal endothelium, and trabecular meshwork. This truly reflects the important roles of the limbus in ocular physiology, and the limbal functionality is crucial for corneal health and the entire visual system. Since the anterior limbus containing epithelial structures and limbal epithelial stem cells has been extensively reviewed, this article is focused on the posterior limbus. We have discussed the structural organization and cellular components of the region beneath the limbal epithelium, the characteristics of stem cell types: namely corneal stromal stem cells, endothelial progenitors and trabecular meshwork stem cells, and recent advances leading to the emergence of potential cell therapy options to replenish their respective mature cell types and to correct defects causing corneal abnormalities. We have reviewed different clinical disorders associated with defects of the posterior limbus and summarized the available preclinical and clinical evidence about the developing topic of cell-based therapy for corneal disorders.
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Affiliation(s)
- Gary Hin-Fai Yam
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA; Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; McGowan Institute for Regenerative Medicine, Pittsburgh, PA, USA.
| | - Shaohua Pi
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, PA, USA
| | - Yiqin Du
- Department of Ophthalmology, University of South Florida, Tampa, FL, USA
| | - Jodhbir S Mehta
- Tissue Engineering and Cell Therapy Group, Singapore Eye Research Institute, Singapore; Department of Cornea and External Eye Disease, Singapore National Eye Centre, Singapore; Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore (NUS) Medical School, Singapore.
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4
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Raoux C, Chessel A, Mahou P, Latour G, Schanne-Klein MC. Unveiling the lamellar structure of the human cornea over its full thickness using polarization-resolved SHG microscopy. LIGHT, SCIENCE & APPLICATIONS 2023; 12:190. [PMID: 37528091 PMCID: PMC10394036 DOI: 10.1038/s41377-023-01224-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2023] [Revised: 06/22/2023] [Accepted: 07/05/2023] [Indexed: 08/03/2023]
Abstract
A key property of the human cornea is to maintain its curvature and consequently its refraction capability despite daily changes in intraocular pressure. This is closely related to the multiscale structure of the corneal stroma, which consists of 1-3 µm-thick stacked lamellae made of thin collagen fibrils. Nevertheless, the distribution, size, and orientation of these lamellae along the depth of the cornea are poorly characterized up to now. In this study, we use second harmonic generation (SHG) microscopy to visualize the collagen distribution over the full depth of 10 intact and unstained human corneas (500-600 µm thick). We take advantage of the small coherence length in epi-detection to axially resolve the lamellae while maintaining the corneal physiological curvature. Moreover, as raw epi-detected SHG images are spatially homogenous because of the sub-wavelength size of stromal collagen fibrils, we use a polarimetric approach to measure the collagen orientation in every voxel. After a careful validation of this approach, we show that the collagen lamellae (i) are mostly oriented along the inferior-superior axis in the anterior stroma and along the nasal-temporal axis in the posterior stroma, with a gradual shift in between and (ii) exhibit more disorder in the anterior stroma. These results represent the first quantitative characterization of the lamellar structure of the human cornea continuously along its entire thickness with micrometric resolution. It also shows the unique potential of P-SHG microscopy for imaging of collagen distribution in thick dense tissues.
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Affiliation(s)
- Clothilde Raoux
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France
| | - Anatole Chessel
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France
| | - Pierre Mahou
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France
| | - Gaël Latour
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France
- Université Paris-Saclay, 91190, Gif-sur-Yvette, France
| | - Marie-Claire Schanne-Klein
- Laboratory for Optics and Biosciences, Ecole Polytechnique, CNRS, INSERM, Institut Polytechnique de Paris, 91128, Palaiseau, France.
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5
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Batista A, Guimarães P, Domingues JP, Quadrado MJ, Morgado AM. Two-Photon Imaging for Non-Invasive Corneal Examination. SENSORS (BASEL, SWITZERLAND) 2022; 22:9699. [PMID: 36560071 PMCID: PMC9783858 DOI: 10.3390/s22249699] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 12/02/2022] [Accepted: 12/04/2022] [Indexed: 06/17/2023]
Abstract
Two-photon imaging (TPI) microscopy, namely, two-photon excited fluorescence (TPEF), fluorescence lifetime imaging (FLIM), and second-harmonic generation (SHG) modalities, has emerged in the past years as a powerful tool for the examination of biological tissues. These modalities rely on different contrast mechanisms and are often used simultaneously to provide complementary information on morphology, metabolism, and structural properties of the imaged tissue. The cornea, being a transparent tissue, rich in collagen and with several cellular layers, is well-suited to be imaged by TPI microscopy. In this review, we discuss the physical principles behind TPI as well as its instrumentation. We also provide an overview of the current advances in TPI instrumentation and image analysis. We describe how TPI can be leveraged to retrieve unique information on the cornea and to complement the information provided by current clinical devices. The present state of corneal TPI is outlined. Finally, we discuss the obstacles that must be overcome and offer perspectives and outlooks to make clinical TPI of the human cornea a reality.
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Affiliation(s)
- Ana Batista
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
| | - Pedro Guimarães
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
| | - José Paulo Domingues
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
| | - Maria João Quadrado
- Department of Ophthalmology, Centro Hospitalar e Universitário de Coimbra, 3004-561 Coimbra, Portugal
- Coimbra Institute for Clinical and Biomedical Research (iCBR), Faculty of Medicine, University of Coimbra, 3000-548 Coimbra, Portugal
| | - António Miguel Morgado
- Coimbra Institute for Biomedical Imaging and Translational Research (CIBIT), University of Coimbra, 3000-548 Coimbra, Portugal
- Institute for Nuclear Sciences Applied to Health (ICNAS), University of Coimbra, 3000-548 Coimbra, Portugal
- Department of Physics, Faculty of Science and Technology, University of Coimbra, 3004-516 Coimbra, Portugal
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6
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Ghezzi M, Ferraboschi I, Delledonne A, Pescina S, Padula C, Santi P, Sissa C, Terenziani F, Nicoli S. Cyclosporine-loaded micelles for ocular delivery: Investigating the penetration mechanisms. J Control Release 2022; 349:744-755. [PMID: 35901859 DOI: 10.1016/j.jconrel.2022.07.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Revised: 07/14/2022] [Accepted: 07/18/2022] [Indexed: 11/18/2022]
Abstract
Cyclosporine is an immunomodulatory drug commonly used for the treatment of mild-to-severe dry eye syndrome as well as intermediate and posterior segment diseases as uveitis. The ocular administration is however hampered by its relatively high molecular weight and poor permeability across biological barriers. The aim of this work was to identify a micellar formulation with the ability to solubilize a considerable amount of cyclosporine and promote its transport across ocular barriers. Non-ionic amphiphilic polymers used for micelles preparation were tocopherol polyethylene glycol 1000 succinate (TPGS) and Solutol® HS15. Furthermore, the addition of alpha-linolenic acid was assessed. A second aim was to evaluate micelles fate in the ocular tissues (cornea and sclera) to shed light on penetration mechanisms. This was possible by extracting and quantifying both drug and polymer in the tissues, by studying TPGS hydrolysis in a bio-relevant environment and by following micelles penetration with two-photon microscopy. Furthermore, TPGS role as permeation enhancer on the cornea, with possible irreversible modifications of tissue permeability, was analyzed. Results showed that TPGS micelles (approx. 13 nm in size), loaded with 5 mg/ml of cyclosporine, promoted drug retention in both the cornea and the sclera. Data demonstrated that micelles behavior strictly depends on the tissue: micelles disruption occurs in contact with the cornea, while intact micelles diffuse in the interfibrillar pores of the sclera and form a reservoir that can sustain over time drug delivery to the deeper tissues. Finally, cornea quickly restore the barrier properties after TPGS removal from the tissue, demonstrating its potential good tolerability for ocular application.
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Affiliation(s)
- Martina Ghezzi
- ADDRes Lab, Food and Drug Department, University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy
| | - Ilaria Ferraboschi
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 17/A, 43124 Parma, Italy
| | - Andrea Delledonne
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 17/A, 43124 Parma, Italy
| | - Silvia Pescina
- ADDRes Lab, Food and Drug Department, University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy
| | - Cristina Padula
- ADDRes Lab, Food and Drug Department, University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy
| | - Patrizia Santi
- ADDRes Lab, Food and Drug Department, University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy
| | - Cristina Sissa
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 17/A, 43124 Parma, Italy
| | - Francesca Terenziani
- Department of Chemistry, Life Sciences and Environmental Sustainability, University of Parma, Parco Area delle Scienze 17/A, 43124 Parma, Italy
| | - Sara Nicoli
- ADDRes Lab, Food and Drug Department, University of Parma, Parco Area delle Scienze 27/A, 43124 Parma, Italy.
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7
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Dilley KK, Borden PA, Qu Y, Heidari AE, Prasad KR, Li Y, Sun CH, Chen Z, Kim S, Hill MG, Wong BJF. Potential-Driven Electrochemical Clearing of Ex Vivo Alkaline Corneal Injuries. Transl Vis Sci Technol 2022; 11:32. [PMID: 35061010 PMCID: PMC8787648 DOI: 10.1167/tvst.11.1.32] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/04/2022] Open
Abstract
Purpose Corneal chemical injuries (CCI) obscure vision by opacifying the cornea; however, current treatments may not fully restore clarity. Here, we investigated potential-driven electrochemical treatment (P-ECT) to restore clarity after alkaline-based CCI in ex vivo rabbit corneas and examined collagen fiber orientation changes using second harmonic generation (SHG). Methods NaOH was applied to the corneas of intact New Zealand white rabbit globes. P-ECT was performed on the opacified cornea while optical coherence tomography (OCT) imaging (∼35 frames per second) was simultaneously performed. SHG imaging evaluated collagen fiber structure before NaOH application and after P-ECT. Irrigation with water served as a control. Results P-ECT restored local optical clarity after NaOH exposure. OCT imaging shows both progression of NaOH injury and the restoration of clarity in real time. Analysis of SHG z-stack images show that collagen fibril orientation is similar between control, NaOH-damaged, and post-P-ECT corneas. NaOH-injured corneas flushed with water (15 minutes) show no restoration of clarity. Conclusions P-ECT may be a means to correct alkaline CCI. Collagen fibril orientation does not change after NaOH exposure or P-ECT, suggesting that no irreversible matrix level fiber changes occur. Further studies are required to determine the mechanism for corneal clearing and to ascertain the optimal electrical dosimetry parameters and electrode designs. Translational Relevance Our findings suggest that P-ECT is a potentially effective, low-cost treatment for alkaline CCI.
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Affiliation(s)
- Katelyn K Dilley
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Pamela A Borden
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Yueqiao Qu
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Andrew E Heidari
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Karthik R Prasad
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,School of Medicine, University of California-Irvine, Irvine, CA, USA
| | - Yan Li
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Chung Ho Sun
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA
| | - Zhongping Chen
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA
| | - Sehwan Kim
- Beckman Laser Institute-Korea, Department of Biomedical Engineering, Dankook University, Cheonan-si, Chungnam, Republic of Korea
| | - Michael G Hill
- Department of Chemistry, Occidental College, Los Angeles, CA, USA
| | - Brian J F Wong
- Beckman Laser Institute & Medical Clinic, University of California-Irvine, Irvine, CA, USA.,Department of Biomedical Engineering, University of California-Irvine, Irvine, CA, USA.,Department of Otolaryngology-Head and Neck Surgery, University of California-Irvine, School of Medicine, Orange, CA, USA
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8
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Akella SS, Liu J, Miao Y, Chuck RS, Barmettler A, Zhang C. Collagen Structural Changes in Rat Tarsus After Crosslinking. Transl Vis Sci Technol 2021; 10:3. [PMID: 34003976 PMCID: PMC8088227 DOI: 10.1167/tvst.10.5.3] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Purpose Surgery is the standard treatment for floppy eyelid syndrome, but crosslinking (CXL) tarsus has recently been proposed as an alternative. To the best of our knowledge, this study is the first to use second-harmonic generation (SHG) microscopy to examine tarsal collagen ex vivo before and after photo-activated crosslinking. To quantify crosslinking, this study examined fluorescence recovery after photobleaching (FRAP), which indirectly measures tissue stiffness. Methods Upper eyelid tarsal plates were dissected from 21 Sprague-Dawley rats (total of 42 tarsal plates). Six normal plates were sent for histopathology and SHG imaging; the remaining 36 were crosslinked with phosphate-buffered saline (PBS) alone or riboflavin in PBS (concentrations of 0.1%, 0.3%, and 0.5%). Tissues were irradiated with 365-nm ultraviolet A light (power, 0.45 mW/cm2) for 30 minutes and immediately underwent SHG microscopy. Stiffness was indirectly measured with FRAP using fluorescein isothiocyanate (FITC)-dextran. Results SHG imaging of normal tarsus showed that the organization of collagen bundles is complex and varies greatly depending on location. After crosslinking with high-concentration riboflavin (0.5%), collagen fibers showed clear structural changes, becoming more densely packed and wavier compared to control. FRAP half-time to fluorescence recovery was significantly increased (P < 0.05), indirectly indicating increased tissue stiffness. No structural changes were observed after crosslinking with lower riboflavin concentrations of 0.1% and 0.3%. Conclusions This is the first report of SHG microscopy used to image tarsus collagen before and after crosslinking. These results highlight collagen structural changes, with effects on tissue stiffness indirectly confirmed by FRAP. Translational Relevance Collagen fibers in the tarsus may be a therapeutic target for crosslinking in order to treat symptomatic floppy eyelid syndrome.
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Affiliation(s)
- Sruti S Akella
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Juan Liu
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA.,Department of Ophthalmology, Ning Xia Eye Hospital, Yinchuan, China
| | - Yuan Miao
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA.,Aier School of Ophthalmology, Central South University, Changsha, China
| | - Roy S Chuck
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Anne Barmettler
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Cheng Zhang
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
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9
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Sioufi K, Zheleznyak L, MacRae S, Rocha KM. Femtosecond Lasers in Cornea & Refractive Surgery. Exp Eye Res 2021; 205:108477. [PMID: 33516763 DOI: 10.1016/j.exer.2021.108477] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 01/20/2021] [Accepted: 01/22/2021] [Indexed: 11/18/2022]
Abstract
Since the introduction of femtosecond laser (FS) systems for corneal flap creation in laser-assisted in-situ keratomileusis there have been numerous applications for FS laser in corneal surgery. This manuscript details the utility of FS lasers in corneal surgical procedures including refractive laser surgeries, intracorneal ring segment tunnels, presbyopic treatments, and FS-assisted keratoplasty. We also review the role of FS lasers in diagnostic procedures such as two photon excitation fluorescence and second harmonic generation.
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Affiliation(s)
- Kareem Sioufi
- Storm Eye Institute, Medical University of South Carolina, Charleston, SC, USA
| | | | - Scott MacRae
- Flaum Eye Institute and the Institute of Optics, University of Rochester, Rochester, NY, USA
| | - Karolinne M Rocha
- Storm Eye Institute, Medical University of South Carolina, Charleston, SC, USA.
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10
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Xu M, Ramirez-Garcia MA, Narang H, Buckley MR, Lerner AL, Yoon G. Individualized Characterization of the Distribution of Collagen Fibril Dispersion Using Optical Aberrations of the Cornea for Biomechanical Models. Invest Ophthalmol Vis Sci 2021; 61:54. [PMID: 32866268 PMCID: PMC7463181 DOI: 10.1167/iovs.61.10.54] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose The spatial distribution of collagen fibril dispersion has a significant impact on both corneal biomechanical and optical behaviors. The goal of this study was to demonstrate a novel method to characterize collagen fibril dispersion using intraocular pressure (IOP)-induced changes in corneal optical aberrations for individualized finite-element (FE) modeling. Methods The method was tested through both numerical simulations and ex vivo experiments. Inflation tests were simulated in FE models with three assumed patterns of collagen fibril dispersion and experimentally on three rhesus monkey corneas. Geometry, matrix stiffness, and the IOP-induced changes in wavefront aberrations were measured, and the collagen fibril dispersion was characterized. An individualized corneal model with customized collagen fibril dispersion was developed, and the estimated optical aberrations were compared with the measured data. Results For the theoretical investigations, three assumed distributions of fibril dispersion were all successfully characterized. The estimated optical aberrations closely matched the measured data, with average root-mean-square (RMS) differences of 0.29, 0.24, and 0.10 µm for the three patterns, respectively. The overall features of the IOP-induced changes in optical aberrations were estimated for two ex vivo monkey corneas, with average RMS differences of 0.57 and 0.43 µm. Characterization of the fibril dispersion in the third cornea might have been affected by corneal hydration, resulting in an increased RMS difference, 0.8 µm. Conclusions A more advanced corneal model with individualized distribution of collagen fibril dispersion can be developed and used to improve our ability to understand both biomechanical and optical behaviors of the cornea.
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Affiliation(s)
- Mengchen Xu
- Department of Mechanical Engineering, University of Rochester, Rochester, New York, United States
| | - Manuel A Ramirez-Garcia
- Department of Biomedical Engineering, University of Rochester, Rochester, New York, United States
| | - Harshita Narang
- Department of Biomedical Engineering, University of Rochester, Rochester, New York, United States
| | - Mark R Buckley
- Department of Biomedical Engineering, University of Rochester, Rochester, New York, United States
| | - Amy L Lerner
- Department of Mechanical Engineering, University of Rochester, Rochester, New York, United States.,Department of Biomedical Engineering, University of Rochester, Rochester, New York, United States
| | - Geunyoung Yoon
- Flaum Eye Institute, The Institute of Optics, Center for Visual Science, Department of Biomedical Engineering, University of Rochester, Rochester, New York, United States
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11
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Guo P, Miao Y, Jing Y, Akella S, Wang F, Park CY, Zhang C, Chuck RS. Changes in Collagen Structure and Permeability of Rat and Human Sclera After Crosslinking. Transl Vis Sci Technol 2020; 9:45. [PMID: 32934895 PMCID: PMC7463178 DOI: 10.1167/tvst.9.9.45] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 07/11/2020] [Indexed: 11/25/2022] Open
Abstract
Purpose To use second harmonic generation imaging and fluorescence recovery after photobleaching to demonstrate alterations in scleral collagen structure and permeability after crosslinking in rat and human eyes. Methods Excised rat and human scleras were imaged ex vivo with an inverted two-photon excitation fluorescence microscope before and after photochemical crosslinking using riboflavin and 405-nm laser light. Fluorescence recovery after photobleaching was applied to measure the diffusion of fluorescein isothiocyanate–dextran across the sclera. Results Crosslinking caused scleral collagen fibers to become wavier and more densely packed, with surface collagen being more affected than deeper collagen fibers. Crosslinked sclera showed significantly decreased permeability in the irradiation zone and also extended as far as 250 µm outside the irradiation zone. Conclusions Photochemical crosslinking induced changes in scleral structure and permeability that extended to tissue even outside the irradiation zone. Translational Relevance Ultrastructural changes associated with the emerging clinical technique of photochemical scleral crosslinking have not been well characterized. We demonstrate not only changes in scleral collagen by second harmonic generation imaging but also the associated functional changes in tissue permeability by fluorescence recovery after photobleaching. We report the novel finding of reduced permeability extending well beyond the direct irradiation zone. This has implications for control in the clinical setting.
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Affiliation(s)
- Peng Guo
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY, USA.,Analytical Imaging Facility, Albert Einstein College of Medicine, Bronx, NY, USA.,Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Yuan Miao
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA.,Aier School of Ophthalmology, Central South University, China
| | - Yang Jing
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Sruti Akella
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Fang Wang
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Choul Yong Park
- Department of Ophthalmology, Dongguk University Ilsan Hospital, Goyang, South Korea
| | - Cheng Zhang
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Roy S Chuck
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
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12
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Shin DH, Ryu WY, Jung JH. The Effect of Absorbable and Non-absorbable Scleral Suture on Strabismus Surgery in the Rabbits. Curr Eye Res 2020; 45:1252-1256. [PMID: 32105157 DOI: 10.1080/02713683.2020.1736308] [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] [Indexed: 02/07/2023]
Abstract
Purpose: To evaluate and compare the histopathological changes in a rabbit model, following strabismus surgery using either absorbable or non-absorbable suture materials. Methods: Superior rectus muscle recession was performed in rabbits using either an absorbable (Vicryl®) or non-absorbable (Prolene®) suture material. Hematoxylin-eosin staining was performed and histologic changes in the sclera were evaluated at the first, second, fourth, and eighth weeks, postoperatively. Moreover, the postoperative scleral thickness was measured and the postoperative pattern of arrangement of scleral fibers was analyzed. Results: Suture material-induced limited inflammatory reaction and formation of new vessels were observed in the study subjects, in the early postoperative phase, in both the Vicryl® and Prolene® groups. In the Vicryl® group, multinucleated giant cells were dominant during the inflammatory phase, and replacement by fibrotic scar tissues was observed. In the Prolene® group, the suture material was observed to be intact, and the inflammatory reactions around the sutures were observed to be less severe compared to the Vicryl® group. Meanwhile, neither group exhibited reduction in scleral thickness or irregular rearrangement of scleral fibers. Conclusions: The current histological study demonstrated that there was no significant postoperative scleral tissue changes after a strabismus surgery. Furthermore, the absorbable suture material was observed to induce inflammatory reactions of greater severity, compared to the non-absorbable suture material, in scleral tissues.
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Affiliation(s)
- Dong-Hoon Shin
- Department of Pathology, Pusan National University Yangsan Hospital , Yangsan, South Korea.,Research Institute for Convergence of Biomedical Science and Technology, Pusan National University Yangsan Hospital , Yangsan, South Korea
| | - Won Yeol Ryu
- Department of Ophthalmology, Dong-A University College of Medicine , Busan, South Korea
| | - Jae Ho Jung
- Department of Ophthalmology, Seoul National University College of Medicine , Seoul, South Korea
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13
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Cavinato C, Badel P, Krasny W, Avril S, Morin C. Experimental Characterization of Adventitial Collagen Fiber Kinematics Using Second-Harmonic Generation Imaging Microscopy: Similarities and Differences Across Arteries, Species and Testing Conditions. MULTI-SCALE EXTRACELLULAR MATRIX MECHANICS AND MECHANOBIOLOGY 2020. [DOI: 10.1007/978-3-030-20182-1_5] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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14
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Lee SL, He MY, Chen YF, Dong CY. Quantification of collagen structural changes during chick corneal development. JOURNAL OF BIOPHOTONICS 2020; 13:e201900144. [PMID: 31465146 DOI: 10.1002/jbio.201900144] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/17/2019] [Revised: 08/27/2019] [Accepted: 08/28/2019] [Indexed: 06/10/2023]
Abstract
As the most abundant structural mammalian protein, collagen has been implicated in the pathogenesis of numerous diseases such as osteogenesis imperfecta, and cancer. In the case of cornea, abnormal cornea development can lead to conditions such as agenesis, megalocornea, microcornea, and cornea plana. Therefore, understanding the mechanisms of collagen assembly during development may contribute to the prevention or treatment of corneal diseases. In this study, we applied fast Fourier transform second harmonic generation microscopy to quantify parameters of corneal structures during chick development. Our results show that both the rotational pitch and overall rotational angle of corneal stroma modulate between E9 and E19. In addition, we found that corneal structures between left and right corneas are highly correlated during development.
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Affiliation(s)
- Sheng-Lin Lee
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Ming-Ye He
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Yang-Fang Chen
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
| | - Chen-Yuan Dong
- Department of Physics, National Taiwan University, Taipei, Taiwan, ROC
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15
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Abstract
Two-photon (2P) microscopy is a powerful tool for imaging and exploring label-free biological tissues at high resolution. Although this type of microscopy has been demonstrated in ex vivo ocular tissues of both humans and animal models, imaging the human eye in vivo has always been challenging. This work presents a novel compact 2P microscope for non-contact imaging of the anterior part of the living human eye. The performance of the instrument was tested and the maximum permissible exposure to protect ocular tissues established. To the best of our knowledge, 2P images of the in vivo human cornea, the sclera and the trabecular meshwork are shown for the very first time. Acquired images are of enough quality to visualize collagen arrangement and morphological features of clinical interest. Future implementations of this technique may constitute a potential tool for early diagnosis of ocular diseases at submicron scale.
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16
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Seyed-Razavi Y, Lopez MJ, Mantopoulos D, Zheng L, Massberg S, Sendra VG, Harris DL, Hamrah P. Kinetics of corneal leukocytes by intravital multiphoton microscopy. FASEB J 2019; 33:2199-2211. [PMID: 30226811 PMCID: PMC6338630 DOI: 10.1096/fj.201800684rr] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2018] [Accepted: 08/27/2018] [Indexed: 12/13/2022]
Abstract
Corneal immune privilege is integral in maintaining the clear avascular window to the foreign world. The presence of distinct populations of corneal leukocytes (CLs) in the normal cornea has been firmly established. However, their precise function and kinetics remain, as of yet, unclear. Through intravital multiphoton microscopy (IV-MPM), allowing the means to accumulate critical spatial and temporal cellular information, we provide details for long-term investigation of CL morphology and kinetics under steady state and following inflammation. Significant alterations in size and morphology of corneal CD11c+ dendritic cells (DCs) were noted following acute sterile inflammation, including cell volume (4364.4 ± 489.6 vs. 1787.6 ± 111.0 μm3, P < 0.001) and sphericity (0.82 ± 0.01 vs. 0.42 ± 0.02, P < 0.001) compared with steady state. Furthermore, IV-MPM analyses revealed alterations in both the CD11c+ DC and major histocompatibility complex class II (MHC)-II+ mature antigen-presenting cell population kinetics during inflammation, including track displacement length (CD11c: 16.57 ± 1.41 vs. 4.64 ± 0.56 μm, P < 0.001; MHC-II: 9.03 ± 0.37 vs. 4.09 ± 0.39, P < 0.001) and velocity (CD11c: 1.91 ± 0.07 μm/min vs. 1.73 ± 0.1302 μm/min; MHC-II: 2.97 ± 0.07 vs. 1.62 ± 0.08, P < 0.001) compared with steady state. Our results reveal in vivo evidence of sessile CL populations exhibiting dendritic morphology under steady state and increased velocity of spherical leukocytes following inflammation. IV-MPM represents a powerful tool to study leukocytes in corneal diseases in context.-Seyed-Razavi, Y., Lopez, M. J., Mantopoulos, D., Zheng, L., Massberg, S., Sendra, V. G., Harris, D. L., Hamrah, P. Kinetics of corneal leukocytes by intravital multiphoton microscopy.
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Affiliation(s)
- Yashar Seyed-Razavi
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Schepens Eye Research Institute, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Maria J. Lopez
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Schepens Eye Research Institute, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Dimosthenis Mantopoulos
- Schepens Eye Research Institute, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
- Division of Immunology, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Lixin Zheng
- Schepens Eye Research Institute, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
- Division of Immunology, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA
| | - Steffen Massberg
- Division of Immunology, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA
- Department of Cardiology, Ludwig Maximilians Universität, Munich, Germany
| | - Victor G. Sendra
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Schepens Eye Research Institute, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Deshea L. Harris
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Schepens Eye Research Institute, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
| | - Pedram Hamrah
- Center for Translational Ocular Immunology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Department of Ophthalmology, Tufts Medical Center, Tufts University School of Medicine, Tufts University, Boston, Massachusetts, USA
- Schepens Eye Research Institute, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
- Division of Immunology, Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts, USA
- Sackler School of Graduate Biomedical Sciences, Tufts University, Boston, Massachusetts, USA
- Cornea Service, Tufts New England Eye Center, Boston, Massachusetts, USA
- Cornea Service, Department of Ophthalmology, Massachusetts Eye and Ear Infirmary, Harvard Medical School, Boston, Massachusetts, USA
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17
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Bradford SM, Mikula ER, Juhasz T, Brown DJ, Jester JV. Collagen fiber crimping following in vivo UVA-induced corneal crosslinking. Exp Eye Res 2018; 177:173-180. [PMID: 30118656 PMCID: PMC6911705 DOI: 10.1016/j.exer.2018.08.009] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2018] [Revised: 08/03/2018] [Accepted: 08/13/2018] [Indexed: 02/03/2023]
Abstract
The purpose of this study was to measure collagen fiber crimping (CFC) using nonlinear optical imaging of second harmonic generated (SHG) signals to determine the effects of UVA-riboflavin induced corneal collagen crosslinking (UVA CXL) on collagen structure. Two groups, four rabbits each, were treated in the right eye with standard UVA CXL. In vivo confocal microscopy was performed at 1, 2, and 4 weeks after treatment for the first group and up to three months for the second group to measure epithelial/stromal thickness and corneal haze during recovery. Rabbits were sacrificed at one and three months, respectively, and their corneas fixed under pressure. Regions of crosslinking were identified by the presence of collagen autofluorescence (CAF) and then collagen structure was imaged using SHG microscopy. The degree of CFC was determined by measuring the percentage difference between the length of the collagen fiber and the linear distance traveled. CFC was measured in the central anterior and posterior CXL region, the peripheral non-crosslinked region in the same cornea, and the central cornea of the non-crosslinked contralateral eye. No change in corneal thickness was detected after one month, however the stromal thickness surpassed its original baseline thickness at three months by 25.9 μm. Corneal haze peaked at one month and then began to clear. Increased CAF was detected in all CXL corneas, localized to the anterior stroma and extending to 42.4 ± 3.4% and 47.7 ± 7.6% of the corneal thickness at one and three months. There was a significant (P < 0.05) reduction in CFC in the CAF region in all eyes averaging 1.007 ± 0.006 and 1.009 ± 0.005 in one and three month samples compared to 1.017 ± 0.04 and 1.016 ± 0.06 for controls. These results indicate that there is a significant reduction in collagen crimping following UVA CXL of approximately 1%. One possible explanation for this loss of crimping could be shortening of the collagen fibers over the CXL region.
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Affiliation(s)
- Samantha M Bradford
- Biomedical Engineering, University of California, Irvine, Irvine, CA, United States.
| | - Eric R Mikula
- Ophthalmology, University of California, Irvine, Irvine, CA, United States.
| | - Tibor Juhasz
- Biomedical Engineering, University of California, Irvine, Irvine, CA, United States; Ophthalmology, University of California, Irvine, Irvine, CA, United States.
| | - Donald J Brown
- Ophthalmology, University of California, Irvine, Irvine, CA, United States.
| | - James V Jester
- Biomedical Engineering, University of California, Irvine, Irvine, CA, United States; Ophthalmology, University of California, Irvine, Irvine, CA, United States.
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18
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Ma J, Wang Y, Wei P, Jhanji V. Biomechanics and structure of the cornea: implications and association with corneal disorders. Surv Ophthalmol 2018; 63:851-861. [PMID: 29857022 DOI: 10.1016/j.survophthal.2018.05.004] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2018] [Revised: 05/17/2018] [Accepted: 05/21/2018] [Indexed: 12/14/2022]
Abstract
Recent studies have shown that alterations in corneal biomechanical properties are associated with corneal pathologies, particularly corneal ectasia. Moreover, these alterations may have implications with regard to the outcomes of therapeutic modalities and corneal refractive surgeries. We address corneal anatomy and its relevance to corneal biomechanical characteristics, as well as ocular and systemic conditions associated with changes in corneal biomechanics.
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Affiliation(s)
- Jiaonan Ma
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China
| | - Yan Wang
- Clinical College of Ophthalmology, Tianjin Medical University, Tianjin, China; Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Naikai University, Tianjin Medical University, Tianjin, China.
| | - Pinghui Wei
- Tianjin Eye Hospital, Tianjin Eye Institute, Tianjin Key Laboratory of Ophthalmology and Visual Science, Naikai University, Tianjin Medical University, Tianjin, China
| | - Vishal Jhanji
- UPMC Eye Center, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, USA
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19
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Zyablitskaya M, Munteanu EL, Nagasaki T, Paik DC. Second Harmonic Generation Signals in Rabbit Sclera As a Tool for Evaluation of Therapeutic Tissue Cross-linking (TXL) for Myopia. J Vis Exp 2018. [PMID: 29364259 DOI: 10.3791/56385] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Methods to strengthen tissue by introducing chemical bonds (non-enzymatic cross-linking) into structural proteins (fibrillar collagens) for therapy include photochemical cross-linking and tissue cross-linking (TXL) methods. Such methods for inducing mechanical tissue property changes are being employed to the cornea in corneal thinning (mechanically weakened) disorders such as keratoconus as well as the sclera in progressive myopia, where thinning and weakening of the posterior sclera occurs and likely contributes to axial elongation. The primary target proteins for such tissue strengthening are fibrillar collagens which constitute the great majority of dry weight proteins in the cornea and sclera. Fortuitously, fibrillar collagens are the main source of second harmonic generation signals in the tissue extracellular space. Therefore, modifications of the collagen proteins, such as those induced through cross-linking therapies, could potentially be detected and quantitated through the use of second harmonic generation microscopy (SHGM). Monitoring SHGM signals through the use of a laser scanning microscopy system coupled with an infrared excitation light source is an exciting modern imaging method that is enjoying widespread usage in the biomedical sciences. Thus, the present study was undertaken in order to evaluate the use of SHGM microscopy as a means to measure induced cross-linking effects in ex vivo rabbit sclera, following an injection of a chemical cross-linking agent into the sub-Tenon's space (sT), an injection approach that is standard practice for causing ocular anesthesia during ophthalmologic clinical procedures. The chemical cross-linking agent, sodium hydroxymethylglycinate (SMG), is from a class of cosmetic preservatives known as formaldehyde releasing agents (FARs). Scleral changes following reaction with SMG resulted in increases in SHG signals and correlated with shifts in thermal denaturation temperature, a standard method for evaluating induced tissue cross-linking effects.
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Affiliation(s)
- Mariya Zyablitskaya
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons
| | - E Laura Munteanu
- Confocal and Specialized Microscopy Shared Resource, Herbert Irving Comprehensive Cancer Center, Columbia University
| | - Takayuki Nagasaki
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons
| | - David C Paik
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons;
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20
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Bueno JM, Ávila FJ, Artal P. Comparison of second harmonic microscopy images of collagen-based ocular tissues with 800 and 1045 nm. BIOMEDICAL OPTICS EXPRESS 2017; 8:5065-5074. [PMID: 29188103 PMCID: PMC5695953 DOI: 10.1364/boe.8.005065] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/11/2017] [Accepted: 10/17/2017] [Indexed: 06/07/2023]
Abstract
Second harmonic generation (SHG) imaging is a well-suited multiphoton technique allowing visualization of biological tissues mainly composed of collagen with submicron resolution. Despite its inherent confocal properties, imaging of deeper layers within thick samples has still some limitations. Although the use of longer wavelengths might help to overcome this, the dependence between SHG signals and wavelength is still under discussion. We report here on the dependence with wavelength of SHG signals from collagen-based ocular tissues. The quality of SHG images for two commonly used excitation wavelengths (800 and 1045 nm) is studied. The analysis of the collagen structural information reveals that the information provided by both wavelengths is similar. It was also found that, independently of the depth location, 1045-nm SHG images presented always lower signal levels than those acquired with 800 nm. However, the contrast of the former images was higher, what may improve the visualization of certain features of interest.
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21
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Hadraba D, Janacek J, Filova E, Lopot F, Paesen R, Fanta O, Jarman A, Necas A, Ameloot M, Jelen K. Calcaneal Tendon Collagen Fiber Morphometry and Aging. MICROSCOPY AND MICROANALYSIS : THE OFFICIAL JOURNAL OF MICROSCOPY SOCIETY OF AMERICA, MICROBEAM ANALYSIS SOCIETY, MICROSCOPICAL SOCIETY OF CANADA 2017; 23:1040-1047. [PMID: 28929998 DOI: 10.1017/s1431927617012569] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Fibrillar collagen in tendons and its natural development in rabbits are discussed in this paper. Achilles tendons from newborn (~7 days) to elderly (~38 months) rabbits were monitored in intact (n tendons=24) and microtome sectioned (n tendons=11) states with label-free second harmonic generation microscopy. After sectioning, the collagen fiber pattern was irregular for the younger animals and remained oriented parallel to the load axis of the tendon for the older animals. In contrast, the collagen fiber pattern in the intact samples followed the load axis for all the age groups. However, there was a significant difference in the tendon crimp pattern appearance between the age groups. The crimp amplitude (A) and wavelength (Λ) started at very low values (A=2.0±0.6 µm, Λ=19±4 µm) for the newborn animals. Both parameters increased for the sexually mature animals (>5 months old). When the animals were fully mature the amplitude decreased but the wavelength kept increasing. The results revealed that the microtome sectioning artifacts depend on the age of animals and that the collagen crimp pattern reflects the physical growth and development.
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Affiliation(s)
- Daniel Hadraba
- Department of Biomathematics, Institute of Physiology, The Czech Academy of Sciences, Videnska 1083, Prague 4, 14220, Czech Republic
- Department of Anatomy and Biomechanics, Faculty of Physical Education and Sport, Charles University, Jose Martiho 31, Prague 6, 162 00, Czech Republic
- Department of Biophysics, Biomedical Research Institute, Hasselt University, Agoralaan building C, Diepenbeek, B-3590, Belgium
| | - Jiri Janacek
- Department of Biomathematics, Institute of Physiology, The Czech Academy of Sciences, Videnska 1083, Prague 4, 14220, Czech Republic
| | - Eva Filova
- Department of Tissue Engineering, Institute of Experimental Medicine, The Czech Academy of Sciences, Videnska 1083, Prague 4, 14220, Czech Republic
| | - Frantisek Lopot
- Department of Anatomy and Biomechanics, Faculty of Physical Education and Sport, Charles University, Jose Martiho 31, Prague 6, 162 00, Czech Republic
| | - Rik Paesen
- Department of Biophysics, Biomedical Research Institute, Hasselt University, Agoralaan building C, Diepenbeek, B-3590, Belgium
| | - Ondrej Fanta
- Department of Anatomy and Biomechanics, Faculty of Physical Education and Sport, Charles University, Jose Martiho 31, Prague 6, 162 00, Czech Republic
| | - Anneliese Jarman
- Department of Tissue Engineering & Biophotonics, King's College London, Guy's Campus, Great Maze Pond, London, SE1 9RT, UK
| | - Alois Necas
- Faculty of Veterinary Medicine, University of Veterinary and Pharmaceutical Sciences Brno, Palackeho tr. 1/3, Brno, 612 42, Czech Republic
| | - Marcel Ameloot
- Department of Biophysics, Biomedical Research Institute, Hasselt University, Agoralaan building C, Diepenbeek, B-3590, Belgium
| | - Karel Jelen
- Department of Biomathematics, Institute of Physiology, The Czech Academy of Sciences, Videnska 1083, Prague 4, 14220, Czech Republic
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22
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Zyablitskaya M, Takaoka A, Munteanu EL, Nagasaki T, Trokel SL, Paik DC. Evaluation of Therapeutic Tissue Crosslinking (TXL) for Myopia Using Second Harmonic Generation Signal Microscopy in Rabbit Sclera. Invest Ophthalmol Vis Sci 2017; 58:21-29. [PMID: 28055099 PMCID: PMC5225996 DOI: 10.1167/iovs.16-20241] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Purpose Second harmonic generation signals (SHG) are emitted preferentially from collagenous tissue structures and have been used to evaluate photochemically-induced (CXL) crosslinking changes in the cornea. Since therapeutic tissue crosslinking (TXL) using sodium hydroxymethylglycinate (SMG) of the sclera is a potential treatment for high myopia, we explored the use of SHG microscopy to evaluate the effects. Methods Single sub-Tenon's (sT) injections (400 μL) using SMG (40-400 mM) were made at the equatorial 12 o'clock position of the right eye of cadaveric rabbit heads (n = 16 pairs). After 3.5 hours, confocal microscopy (CM) was performed using 860 nm two-photon excitation and 400 to 450 nm emission. Pixel density and fiber bundle "waviness" analyses were performed on the images. Crosslinking effects were confirmed using thermal denaturation (Tm) temperature. Comparison experiments with riboflavin photochemical crosslinking were done. Results Therapeutic tissue crosslinking localization studies indicated that crosslinking changes occurred at the site of injection and in adjacent sectors. Second harmonic generation signals revealed large fibrous collagenous bundled structures that displayed various degrees of waviness. Histogram analysis showed a nearly 6-fold signal increase in 400 mM SMG over 40 mM. This corresponded to a ΔTm = 13°C for 400 mM versus ΔTm = 4°C for 40 mM. Waviness analysis indicated increased fiber straightening as a result of SMG CXL. Conclusions Second harmonic generation signal intensity and fiber bundle waviness is altered by scleral tissue crosslinking using SMG. These changes provide insights into the macromolecular changes that are induced by therapeutic crosslinking technology and may provide a method to evaluate connective tissue protein changes induced by scleral crosslinking therapies.
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Affiliation(s)
- Mariya Zyablitskaya
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Anna Takaoka
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Emilia L Munteanu
- Confocal and Specialized Microscopy Shared Resource, Herbert Irving Comprehensive Cancer Center, Columbia University, New York, New York, United States
| | - Takayuki Nagasaki
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - Stephen L Trokel
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, United States
| | - David C Paik
- Department of Ophthalmology, Columbia University College of Physicians and Surgeons, New York, New York, United States
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23
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Zhou HY, Cao Y, Wu J, Zhang WS. Role of corneal collagen fibrils in corneal disorders and related pathological conditions. Int J Ophthalmol 2017; 10:803-811. [PMID: 28546941 DOI: 10.18240/ijo.2017.05.24] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2016] [Accepted: 03/23/2017] [Indexed: 01/24/2023] Open
Abstract
The cornea is a soft tissue located at the front of the eye with the principal function of transmitting and refracting light rays to precisely sense visual information. Corneal shape, refraction, and stromal stiffness are to a large part determined by corneal fibrils, the arrangements of which define the corneal cells and their functional behaviour. However, the modality and alignment of native corneal collagen lamellae are altered in various corneal pathological states such as infection, injury, keratoconus, corneal scar formation, and keratoprosthesis. Furthermore, corneal recuperation after corneal pathological change is dependent on the balance of corneal collagen degradation and contraction. A thorough understanding of the characteristics of corneal collagen is thus necessary to develop viable therapies using the outcome of strategies using engineered corneas. In this review, we discuss the composition and distribution of corneal collagens as well as their degradation and contraction, and address the current status of corneal tissue engineering and the progress of corneal cross-linking.
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Affiliation(s)
- Hong-Yan Zhou
- Department of Ophthalmology, China-Japan Union Hospital of Jilin University, Changchun 130033, Jilin Province, China
| | - Yan Cao
- Department of Ophthalmology, China-Japan Union Hospital of Jilin University, Changchun 130033, Jilin Province, China
| | - Jie Wu
- Department of Ophthalmology, China-Japan Union Hospital of Jilin University, Changchun 130033, Jilin Province, China
| | - Wen-Song Zhang
- Department of Ophthalmology, the Second Hospital of Jilin University, Changchun 130000, Jilin Province, China
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