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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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Hatami-Marbini H, Emu ME. The relationship between keratan sulfate glycosaminoglycan density and mechanical stiffening of CXL treatment. Exp Eye Res 2023; 234:109570. [PMID: 37454921 PMCID: PMC10530321 DOI: 10.1016/j.exer.2023.109570] [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: 05/05/2023] [Revised: 06/20/2023] [Accepted: 07/06/2023] [Indexed: 07/18/2023]
Abstract
The corneal stroma is primarily composed of collagen fibrils, proteoglycans, and glycosaminoglycans (GAGs). It is known that corneal crosslinking (CXL) treatment improves mechanical properties of the cornea. However, the influence of stromal composition on the strengthening effect of CXL procedure has not been thoroughly investigated. The primary objective of the present research was to characterize the effect of keratan sulfate (KS) GAGs on the efficacy of CXL therapy. To this end, the CXL method was used to crosslink porcine corneal samples from which KS GAGs were enzymatically removed by keratanase II enzyme. Alcian blue staining was done to confirm the successful digestion of GAGs and uniaxial tensile experiments were performed for characterizing corneal mechanical properties. The influence of GAG removal and CXL treatment on resistance of corneal samples against enzymatic pepsin degradation was also quantified. It was found that removal of KS GAGs significantly softened corneal tensile properties (P < 0.05). Moreover, the CXL therapy significantly increased the tensile stiffness of GAG-depleted strips (P < 0.05). GAG-depleted corneal buttons were dissolved in the pepsin digestion solution significantly faster than control samples (P < 0.05). The CXL treatment significantly increased the time needed for complete pepsin digestion of GAG-depleted disks (P < 0.05). Based on these observations, we concluded that KS GAGs play a significant role in defining tensile properties and structural integrity of porcine cornea. Furthermore, the stiffening influence of the CXL treatment does not significantly depend on the density of corneal KS GAGs. The findings of the present study provided new information on the relation between corneal composition and CXL procedure mechanical effects.
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Affiliation(s)
- H Hatami-Marbini
- Computational Biomechanics Research Laboratory, Mechanical and Industrial Engineering, Department, University of Illinois Chicago, Chicago, IL, USA.
| | - Md E Emu
- Computational Biomechanics Research Laboratory, Mechanical and Industrial Engineering, Department, University of Illinois Chicago, Chicago, IL, USA
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3
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De Hoon I, Barras A, Swebocki T, Vanmeerhaeghe B, Bogaert B, Muntean C, Abderrahmani A, Boukherroub R, De Smedt S, Sauvage F, Szunerits S. Influence of the Size and Charge of Carbon Quantum Dots on Their Corneal Penetration and Permeation Enhancing Properties. ACS APPLIED MATERIALS & INTERFACES 2023; 15:3760-3771. [PMID: 36645837 DOI: 10.1021/acsami.2c18598] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
Reaching the corneal endothelium through the topical administration of therapeutic drugs remains a challenge in ophthalmology. Besides, endothelial cells are not able to regenerate, and diseases at this site can lead to corneal blindness. Targeting the corneal endothelium implies efficient penetration through the three corneal layers, which still remains difficult for small molecules. Carbon quantum dots (CQDs) have demonstrated great potential for ocular nanomedicine. This study focuses on the corneal penetration abilities of differently charged CQDs and their use as permeation enhancers for drugs. Excised whole bovine eyes were used as an ex vivo model to investigate corneal penetration of CQDs derived from glucosamine using β-alanine, ethylenediamine, or spermidine as a passivation agent. It was found that negatively charged CQDs have limited corneal penetration ability, while positively charged CQDs derived from glucosamine hydrochloride and spermidine (CQD-S) penetrate the entire corneal epithelium all the way down to the endothelium. CQD-S were shown to enhance the penetration of FITC-dextran 150 kDa, suggesting that they could be used as efficient penetration enhancers for therapeutic delivery to the corneal endothelium.
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Affiliation(s)
- Inès De Hoon
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 - IEMN, F-59000 Lille, France
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Alexandre Barras
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 - IEMN, F-59000 Lille, France
| | - Tomasz Swebocki
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 - IEMN, F-59000 Lille, France
| | - Bernd Vanmeerhaeghe
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Bram Bogaert
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Cristina Muntean
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Amar Abderrahmani
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 - IEMN, F-59000 Lille, France
| | - Rabah Boukherroub
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 - IEMN, F-59000 Lille, France
| | - Stefaan De Smedt
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Félix Sauvage
- Laboratory of General Biochemistry and Physical Pharmacy, Faculty of Pharmaceutical Sciences, Ghent University, 9000 Ghent, Belgium
| | - Sabine Szunerits
- Univ. Lille, CNRS, Centrale Lille, Univ. Polytechnique Hauts-de-France, UMR 8520 - IEMN, F-59000 Lille, France
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Balters L, Reichl S. 3D bioprinting of corneal models: A review of the current state and future outlook. J Tissue Eng 2023; 14:20417314231197793. [PMID: 37719307 PMCID: PMC10504850 DOI: 10.1177/20417314231197793] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 08/13/2023] [Indexed: 09/19/2023] Open
Abstract
The cornea is the outermost layer of the eye and serves to protect the eye and enable vision by refracting light. The need for cornea organ donors remains high, and the demand for an artificial alternative continues to grow. 3D bioprinting is a promising new method to create artificial organs and tissues. 3D bioprinting offers the precise spatial arrangement of biomaterials and cells to create 3D constructs. As the cornea is an avascular tissue which makes it more attractive for 3D bioprinting, it could be one of the first tissues to be made fully functional via 3D bioprinting. This review discusses the most common 3D bioprinting technologies and biomaterials used for 3D bioprinting corneal models. Additionally, the current state of 3D bioprinted corneal models, especially specific characteristics such as light transmission, biomechanics, and marker expression, and in vivo studies are discussed. Finally, the current challenges and future prospects are presented.
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Affiliation(s)
- Leon Balters
- Institute of Pharmaceutical Technology and Biopharmaceutics, Technische Universität Braunschweig, Braunschweig, Germany
| | - Stephan Reichl
- Institute of Pharmaceutical Technology and Biopharmaceutics, Technische Universität Braunschweig, Braunschweig, Germany
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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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Mutoji KN, Sun M, Elliott G, Moreno IY, Hughes C, Gesteira TF, Coulson-Thomas VJ. Extracellular Matrix Deposition and Remodeling after Corneal Alkali Burn in Mice. Int J Mol Sci 2021; 22:5708. [PMID: 34071909 PMCID: PMC8199272 DOI: 10.3390/ijms22115708] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2021] [Revised: 05/24/2021] [Accepted: 05/25/2021] [Indexed: 12/13/2022] Open
Abstract
Corneal transparency relies on the precise arrangement and orientation of collagen fibrils, made of mostly Type I and V collagen fibrils and proteoglycans (PGs). PGs are essential for correct collagen fibrillogenesis and maintaining corneal homeostasis. We investigated the spatial and temporal distribution of glycosaminoglycans (GAGs) and PGs after a chemical injury. The chemical composition of chondroitin sulfate (CS)/dermatan sulfate (DS) and heparan sulfate (HS) were characterized in mouse corneas 5 and 14 days after alkali burn (AB), and compared to uninjured corneas. The expression profile and corneal distribution of CS/DSPGs and keratan sulfate (KS) PGs were also analyzed. We found a significant overall increase in CS after AB, with an increase in sulfated forms of CS and a decrease in lesser sulfated forms of CS. Expression of the CSPGs biglycan and versican was increased after AB, while decorin expression was decreased. We also found an increase in KS expression 14 days after AB, with an increase in lumican and mimecan expression, and a decrease in keratocan expression. No significant changes in HS composition were noted after AB. Taken together, our study reveals significant changes in the composition of the extracellular matrix following a corneal chemical injury.
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Affiliation(s)
- Kazadi N. Mutoji
- College of Optometry, University of Houston, Houston, TX 77204, USA; (K.N.M.); (M.S.); (G.E.); (I.Y.M.); (T.F.G.)
| | - Mingxia Sun
- College of Optometry, University of Houston, Houston, TX 77204, USA; (K.N.M.); (M.S.); (G.E.); (I.Y.M.); (T.F.G.)
| | - Garrett Elliott
- College of Optometry, University of Houston, Houston, TX 77204, USA; (K.N.M.); (M.S.); (G.E.); (I.Y.M.); (T.F.G.)
| | - Isabel Y. Moreno
- College of Optometry, University of Houston, Houston, TX 77204, USA; (K.N.M.); (M.S.); (G.E.); (I.Y.M.); (T.F.G.)
| | - Clare Hughes
- School of Biosciences, Cardiff University, Cardiff CF10 3AT, UK;
| | - Tarsis F. Gesteira
- College of Optometry, University of Houston, Houston, TX 77204, USA; (K.N.M.); (M.S.); (G.E.); (I.Y.M.); (T.F.G.)
- Optimvia, Batavia, OH 45103, USA
| | - Vivien J. Coulson-Thomas
- College of Optometry, University of Houston, Houston, TX 77204, USA; (K.N.M.); (M.S.); (G.E.); (I.Y.M.); (T.F.G.)
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Cheung IM, Mcghee CN, Sherwin T. A new perspective on the pathobiology of keratoconus: interplay of stromal wound healing and reactive species‐associated processes. Clin Exp Optom 2021; 96:188-96. [DOI: 10.1111/cxo.12025] [Citation(s) in RCA: 38] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Accepted: 10/30/2012] [Indexed: 12/13/2022] Open
Affiliation(s)
- Isabella My Cheung
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
| | - Charles Nj Mcghee
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
| | - Trevor Sherwin
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
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Kelly SJ, duPlessis L, Soley J, Noble F, Wells HC, Kelly PJ. Pilot study on the effects of preservatives on corneal collagen parameters measured by small angle X-ray scattering analysis. BMC Res Notes 2021; 14:78. [PMID: 33640024 PMCID: PMC7913446 DOI: 10.1186/s13104-021-05494-y] [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: 10/15/2020] [Accepted: 02/16/2021] [Indexed: 11/30/2022] Open
Abstract
Objective Small angle X-ray scattering (SAXS) analysis is a sensitive way of determining the ultrastructure of collagen in tissues. Little is known about how parameters measured by SAXS are affected by preservatives commonly used to prevent autolysis. We determined the effects of formalin, glutaraldehyde, Triton X and saline on measurements of fibril diameter, fibril diameter distribution, and D-spacing of corneal collagen using SAXS analysis. Results Compared to sections of sheep and cats’ corneas stored frozen as controls, those preserved in 5% glutaraldehyde and 10% formalin had significantly larger mean collagen fibril diameters, increased fibril diameter distribution and decreased D-spacing. Sections of corneas preserved in Triton X had significantly increased collagen fibril diameters and decreased fibril diameter distribution. Those preserved in 0.9% saline had significantly increased mean collagen fibril diameters and decreased diameter distributions. Subjectively, the corneas preserved in 5% glutaraldehyde and 10% formalin maintained their transparency but those in Triton X and 0.9% saline became opaque. Subjective morphological assessment of transmission electron microscope images of corneas supported the SAXS data. Workers using SAXS analysis to characterize collagen should be alerted to changes that can be introduced by common preservatives in which their samples may have been stored.
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Affiliation(s)
- Susyn Joan Kelly
- Department of Clinical Sciences, Ross University of Veterinary Medicine, Basseterre, Saint Kitts and Nevis. .,School of Engineering and Advanced Technology, Massey University, Palmerston North, 4442, New Zealand.
| | - Lizette duPlessis
- Department of Anatomy and Physiology, Electron Microscope Unit, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110, South Africa
| | - John Soley
- Department of Anatomy and Physiology, Electron Microscope Unit, Faculty of Veterinary Science, University of Pretoria, Onderstepoort, 0110, South Africa
| | - Frazer Noble
- School of Engineering and Advanced Technology, Massey University, Palmerston North, 4442, New Zealand
| | - Hannah Carolyn Wells
- School of Engineering and Advanced Technology, Massey University, Palmerston North, 4442, New Zealand
| | - Patrick John Kelly
- Department of Clinical Sciences, Ross University of Veterinary Medicine, Basseterre, Saint Kitts and Nevis
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9
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Bi L, Lwigale P. Transcriptomic analysis of differential gene expression during chick periocular neural crest differentiation into corneal cells. Dev Dyn 2019; 248:583-602. [PMID: 31004457 DOI: 10.1002/dvdy.43] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2018] [Revised: 03/13/2019] [Accepted: 03/19/2019] [Indexed: 12/15/2022] Open
Abstract
BACKGROUND Multipotent neural crest cells (NCC) contribute to the corneal endothelium and keratocytes during ocular development, but the molecular mechanisms that underlie this process remain poorly understood. We performed RNA-Seq analysis on periocular neural crest (pNC), corneal endothelium, and keratocytes and validated expression of candidate genes by in situ hybridization. RESULTS RNA-Seq profiling revealed enrichment of genes between pNC and neural crest-derived corneal cells, which correspond to pathways involved in focal adhesion, ECM-receptor interaction, cell adhesion, melanogenesis, and MAPK signaling. Comparisons of candidate NCC genes to ocular gene expression revealed that majority of the NCC genes are expressed in the pNC, but they are either differentially expressed or maintained during corneal development. Several genes involved in retinoic acid, transforming growth factor-β, and Wnt signaling pathways and their modulators are also differentially expressed. We identified differentially expressed transcription factors as potential downstream candidates that may instruct expression of genes involved in establishing corneal endothelium and keratocyte identities. CONCLUSION Combined, our data reveal novel changes in gene expression profiles as pNC differentiate into highly specialized corneal endothelial cells and keratocytes. These data serve as platform for further analyses of the molecular networks involved in NCC differentiation into corneal cells and provide insights into genes involved in corneal dysgenesis and adult diseases.
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Affiliation(s)
- Lian Bi
- BioSciences, Rice University, Houston, Texas
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10
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Blackburn BJ, Jenkins MW, Rollins AM, Dupps WJ. A Review of Structural and Biomechanical Changes in the Cornea in Aging, Disease, and Photochemical Crosslinking. Front Bioeng Biotechnol 2019; 7:66. [PMID: 31019909 PMCID: PMC6459081 DOI: 10.3389/fbioe.2019.00066] [Citation(s) in RCA: 78] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2018] [Accepted: 03/07/2019] [Indexed: 12/27/2022] Open
Abstract
The study of corneal biomechanics is motivated by the tight relationship between biomechanical properties and visual function within the ocular system. For instance, variation in collagen fibril alignment and non-enzymatic crosslinks rank high among structural factors which give rise to the cornea's particular shape and ability to properly focus light. Gradation in these and other factors engender biomechanical changes which can be quantified by a wide variety of techniques. This review summarizes what is known about both the changes in corneal structure and associated changes in corneal biomechanical properties in aging, keratoconic, and photochemically crosslinked corneas. In addition, methods for measuring corneal biomechanics are discussed and the topics are related to both clinical studies and biomechanical modeling simulations.
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Affiliation(s)
- Brecken J. Blackburn
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
- Department of Biomedical Engineering, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
- Department of Ophthalmology, Cleveland Clinic Lerner College of Medicine of CWRU, Cleveland, OH, United States
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
| | - Michael W. Jenkins
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
- Department of Pediatrics, Case Western Reserve University, Cleveland, OH, United States
| | - Andrew M. Rollins
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
| | - William J. Dupps
- Cole Eye Institute, Cleveland Clinic, Cleveland, OH, United States
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, United States
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11
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Microwave treatment of the cornea leads to localised disruption of the extracellular matrix. Sci Rep 2018; 8:13742. [PMID: 30213993 PMCID: PMC6137159 DOI: 10.1038/s41598-018-32110-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Accepted: 08/31/2018] [Indexed: 11/11/2022] Open
Abstract
Microwave keratoplasty is a thermo-refractive surgical procedure that can correct myopia (short-sightedness) and pathologic corneal steepening by using microwave energy to cause localised shrinkage around an annulus of the cornea leading to its flattening and vision correction. The effects on the corneal extracellular matrix, however, have not yet been evaluated, thus the current study to assess post-procedure ultrastructural changes in an in-vivo rabbit model. To achieve this a series of small-angle x-ray scattering (SAXS) experiments were carried out across whole transects of treated and untreated rabbit corneas at 0.25 mm intervals, which indicated no significant change in collagen intra-fibrillar parameters (i.e. collagen fibril diameter or axial D-period), whereas inter-fibrillar measures (i.e. fibril spacing and the degree of spatial order) were markedly altered in microwave-treated regions of the cornea. These structural matrix alterations in microwave-treated corneas have predicted implications for corneal biomechanical strength and tissue transparency, and, we contend, potentially render microwave-treated corneas resistant to surgical stabilization using corneal cross-linking procedures currently employed to combat refractive error caused by corneal steepening.
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12
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Asena L, Alkayid H, Altınörs DD. Corneal Epithelial Wound Healing and Management Strategies. PLASTIC AND THORACIC SURGERY, ORTHOPEDICS AND OPHTHALMOLOGY 2018. [DOI: 10.1007/15695_2017_65] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/05/2022]
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13
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Abstract
Fibrillar collagens (types I, II, III, V, XI, XXIV and XXVII) constitute a sub-group within the collagen family (of which there are 28 types in humans) whose functions are to provide three-dimensional frameworks for tissues and organs. These networks confer mechanical strength as well as signalling and organizing functions through binding to cellular receptors and other components of the extracellular matrix (ECM). Here we describe the structure and assembly of fibrillar collagens, and their procollagen precursors, from the molecular to the tissue level. We show how the structure of the collagen triple-helix is influenced by the amino acid sequence, hydrogen bonding and post-translational modifications, such as prolyl 4-hydroxylation. The numerous steps in the biosynthesis of the fibrillar collagens are reviewed with particular attention to the role of prolyl 3-hydroxylation, collagen chaperones, trimerization of procollagen chains and proteolytic maturation. The multiple steps controlling fibril assembly are then discussed with a focus on the cellular control of this process in vivo. Our current understanding of the molecular packing in collagen fibrils, from different tissues, is then summarized on the basis of data from X-ray diffraction and electron microscopy. These results provide structural insights into how collagen fibrils interact with cell receptors, other fibrillar and non-fibrillar collagens and other ECM components, as well as enzymes involved in cross-linking and degradation.
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Affiliation(s)
- Jordi Bella
- Faculty of Life Sciences, University of Manchester, Oxford Road, Manchester, M13 9PT, UK.
| | - David J S Hulmes
- Tissue Biology and Therapeutic Engineering Unit (UMR5305), CNRS/Université Claude Bernard Lyon 1, Lyon, France
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14
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Establishment of an in vitro monolayer model of macular corneal dystrophy. J Transl Med 2016; 96:1311-1326. [PMID: 27748734 DOI: 10.1038/labinvest.2016.102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 08/13/2016] [Accepted: 08/15/2016] [Indexed: 11/08/2022] Open
Abstract
Macular corneal dystrophy (MCD) is characterized by multiple punctate gray-white opacities in the corneal stromal region, due to the accumulation of abnormally sulfated keratan sulfates. We attempted to develop an in vitro model of MCD by simulating the sulfation inhibition using sodium chlorate, a chemical inhibitor of 3'-phosphoadenosine-5'-phosphosulfate (PAPs). The SEM and micro-Raman spectroscopy results showed the hallmark feature of MCD. Further the gene expression studies elucidated the direct effect of sulfation inhibition on the WNT pathway, that in turn downregulated production of matrix metalloproteinases (MMPs), which causes abnormal matrix deposits leading to loss of transparency in vivo. It also resulted in downregulation of integrin and cadherin complexation that leads to disruption of the epithelial layer in the MCD affected corneas. This study offers a promising initial step toward establishing a relevant in vitro MCD disease model, to assess signaling transduction pathways and devise potential treatment strategies based on MMP administration to the MCD affected corneas.
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15
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Murab S, Ghosh S. Impact of osmoregulatory agents on the recovery of collagen conformation in decellularized corneas. ACTA ACUST UNITED AC 2016; 11:065005. [PMID: 27786166 DOI: 10.1088/1748-6041/11/6/065005] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
The process of decellularization of the cornea leads to the removal of cells and antigens. However, during decellularization the ultrastructure of the corneal matrix is usually damaged and a secondary conformation of the collagen fibrils is modulated resulting in altered transparency and physical properties. The strategy for recovering modulation in collagen conformation may help to attain the native physical properties and transparency of the cornea. Decellularized corneas were treated with varied concentrations of glycerol and dextran, and the collagen conformation was monitored by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), x-ray diffraction (XRD) and Raman spectroscopic analysis. The peak at ~4 Å in XRD established the presence of transitional conformations that decreased with the application of osmoregulatory agents, but could not be completely eliminated. This was validated by the results of ATR-FTIR and Raman analysis. Importantly, the mechanism of this loss and the regaining of transparency has been proposed on the basis of the detachment of decorin molecules from the collagen triple helices, due to the change in collagen conformation during decellularization, and the subsequent partial reversal due to the desiccation effect of the osmoregulatory agents on collagen molecules. Taken together, collagen conformational transition can be considered as an indexing tool for the development of improved decellularization techniques.
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Affiliation(s)
- Sumit Murab
- Department of Textile Technology, Indian Institute of Technology Delhi, New Delhi, India
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16
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Topical delivery of a Rho-kinase inhibitor to the cornea via mucoadhesive film. Eur J Pharm Sci 2016; 91:256-64. [PMID: 27196964 DOI: 10.1016/j.ejps.2016.05.016] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2016] [Revised: 04/29/2016] [Accepted: 05/14/2016] [Indexed: 01/21/2023]
Abstract
The application of inhibitors of the Rho kinase pathway (ROCK inhibitors) to the surface of the eye in the form of eyedrops has beneficial effects which aid the recovery of diseased or injured endothelial cells that line the inner surface of the cornea. The aim of this study was to test the plausibility of delivering a selective ROCK inhibitor, Y-27632, to the cornea using a thin polymeric film. Mucoadhesive polymeric thin films were prepared incorporating Y-27632 and diffusional release into PBS was determined. Topical ocular delivery from the applied film was investigated using freshly excised porcine eyes and eyedrops of equivalent concentration acted as comparators; after 24h the formulations were removed and the corneas extracted. Drug-loaded thin polymeric films, with high clarity and pliability were produced. ROCK inhibitor Y-27632 was weakly retained within the film, with release attaining equilibrium after 1h. This in turn facilitated its rapid ocular delivery, and an approximately three-fold greater penetration of Y-27632 into cryoprobe-treated corneas was observed from the thin film (p<0.01) compared to eyedrops. These findings support the further development of ROCK inhibitor delivery to the cornea via release from thin mucoadhesive films to treat vision loss cause by corneal endothelial dysfunction.
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17
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Spadea L, Maraone G, Verboschi F, Vingolo EM, Tognetto D. Effect of corneal light scatter on vision: a review of the literature. Int J Ophthalmol 2016; 9:459-64. [PMID: 27158621 DOI: 10.18240/ijo.2016.03.24] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2014] [Accepted: 06/08/2015] [Indexed: 11/23/2022] Open
Abstract
The cornea is the transparent connective tissue window at the front of the eye. The physiological role of the cornea is to conduct external light into the eye, focus it, together with the lens, onto the retina, and to provide rigidity to the entire eyeball. Therefore, good vision requires maintenance of the transparency and proper refractive shape of the cornea. The surface structures irregularities can be associated with wavefront aberrations and scattering errors. Light scattering in the human cornea causes a reduction of visual quality. In fact, the cornea must be transparent and maintain a smooth and stable curvature since it contributes to the major part of the focusing power of the eye. In most cases, a simple examination of visual acuity cannot demonstrate the reduction of visual quality secondary light scattering. In fact, clinical techniques for examining the human cornea in vivo have greatly expanded over the last few decades. The measurement of corneal back scattering qualifies the degree of corneal transparency. The measurement of corneal forward-scattering quantifies the amount of visual impairment that is produced by the alteration of transparency. The aim of this study was to review scattering in the human cornea and methods of measuring it.
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Affiliation(s)
- Leopoldo Spadea
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Giorgia Maraone
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Francesca Verboschi
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Enzo Maria Vingolo
- Department of Biotechnology and Medical-Surgical Sciences, "Sapienza" University of Rome, Latina 04100, Italy
| | - Daniele Tognetto
- Eye Clinic, Ospedale Maggiore, University of Trieste, Trieste 34010, Italy
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18
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Xuan M, Wang S, Liu X, He Y, Li Y, Zhang Y. Proteins of the corneal stroma: importance in visual function. Cell Tissue Res 2016; 364:9-16. [DOI: 10.1007/s00441-016-2372-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2015] [Accepted: 01/27/2016] [Indexed: 12/13/2022]
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19
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Characterization of a corneal endothelium engineered on a self-assembled stromal substitute. Exp Eye Res 2015; 145:125-129. [PMID: 26658713 DOI: 10.1016/j.exer.2015.11.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2015] [Revised: 11/20/2015] [Accepted: 11/25/2015] [Indexed: 12/13/2022]
Abstract
Endothelial dysfunctions are the first indication for allogeneic corneal transplantation. Development of a tissue-engineered posterior cornea could be an alternative to the use of native allogeneic tissues. In this paper, we used the self-assembly approach to form a cellularized stromal substitute that served as a carrier for the engineering of an endothelium. This endothelialized stromal substitute was then characterized using alizarin red staining, histology, scanning and transmission electron microscopy, as well as mass spectrometry and immunodetection of collagens and function-related proteins. We report the engineering of a monolayer of flattened endothelial cells with a cell density of 966 ± 242 cells/mm(2) (mean ± SD). Endothelial interdigitations were present between cells. The stromal fibroblasts deposited a dense and cohesive collagenous matrix. Collagen fibrils had a diameter of 39.1 ± 11.3 nm, and a mean center to center interfibrillar space of 50.9 ± 10.9 nm. The stromal substitute was composed of collagen types I, V, VI and XII, as well as lumican and decorin. Type IV collagen was also present underneath the endothelium. The endothelium expressed both the sodium/potassium (Na(+)/K(-)) ATPase and sodium/bicarbonate (Na(+)/ [Formula: see text] ) cotransporter pumps. These results indicate that the self-assembled stromal substitute is able to support the expression of endothelial cell functionality markers and therefore, is a suitable carrier for the engineering of an endothelium that could be used for the treatment of endothelial dysfunctions.
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20
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Massoudi D, Malecaze F, Galiacy SD. Collagens and proteoglycans of the cornea: importance in transparency and visual disorders. Cell Tissue Res 2015. [PMID: 26205093 DOI: 10.1007/s00441-015-2233-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The cornea represents the external part of the eye and consists of an epithelium, a stroma and an endothelium. Due to its curvature and transparency this structure makes up approximately 70% of the total refractive power of the eye. This function is partly made possible by the particular organization of the collagen extracellular matrix contained in the corneal stroma that allows a constant refractive power. The maintenance of such an organization involves other molecules such as type V collagen, FACITs (fibril-associated collagens with interrupted triple helices) and SLRPs (small leucine-rich proteoglycans). These components play crucial roles in the preservation of the correct organization and function of the cornea since their absence or modification leads to abnormalities such as corneal opacities. Thus, the aim of this review is to describe the different corneal collagens and proteoglycans by highlighting their importance in corneal transparency as well as their implication in corneal visual disorders.
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Affiliation(s)
| | - Francois Malecaze
- EA4555, Université Toulouse III Paul Sabatier, Toulouse, France
- CHU Toulouse, Hôpital Purpan, Service d'Ophtalmologie, Toulouse, France
| | - Stephane D Galiacy
- EA4555, Université Toulouse III Paul Sabatier, Toulouse, France.
- CHU Toulouse, Hôpital Purpan, Service d'Ophtalmologie, Toulouse, France.
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21
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Hertsenberg AJ, Funderburgh JL. Stem Cells in the Cornea. PROGRESS IN MOLECULAR BIOLOGY AND TRANSLATIONAL SCIENCE 2015; 134:25-41. [PMID: 26310147 DOI: 10.1016/bs.pmbts.2015.04.002] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
The cornea is the tough, transparent tissue through which light first enters the eye and functions as a barrier to debris and infection as well as two-thirds of the refractive power of the eye. Corneal damage that is not promptly treated will often lead to scarring and vision impairment. Due to the limited options currently available to treat corneal scars, the identification and isolation of stem cells in the cornea has received much attention, as they may have potential for autologous, cell-based approaches to the treatment of damaged corneal tissue.
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Affiliation(s)
- Andrew J Hertsenberg
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA
| | - James L Funderburgh
- Department of Ophthalmology, University of Pittsburgh, Pittsburgh, Pennsylvania, USA.
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22
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Mathebula SD, Segoati TM. Is the central corneal thickness of diabetic patients thicker than that of non-diabetics’ eyes? AFRICAN VISION AND EYE HEALTH 2015. [DOI: 10.4102/aveh.v74i1.307] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The purpose of the study was to evaluate central corneal thickness in diabetic patients and to compare the results with controls without diabetes mellitus. Sixty-five diabetic patients (65 eyes) constituted the study group, and 50 eyes were from the healthy control group (50 non-diabetic patients). The study group was subdivided into group 1 (no diabetic retinopathy, n = 35), group 2 (mild to moderate nonproliferative diabetic retinopathy, n = 20), and group 3 (proliferative diabetic retinopathy, n = 10). Central corneal thickness measurements in microns were determined using ultrasound pachymetry. The mean central corneal thickness was significantly greater in the study group (567.14 μm ± 14.63 μm) than in the control group (531.14 μm ± 5 μm). In addition, the mean central corneal thickness was found to be greater in group 3 (577 μm ± 12 μm) than in groups 1 (562 μm ± 13 μm) and 2 (566.86 μm ± 15 μm), but the difference did not reach statistical significance. We found that the mean central corneal thickness for diabetic patients was thicker than that of the healthy controls. Thicker central corneas associated with diabetes mellitus should be taken into consideration when obtaining accurate intraocular pressure measurements in diabetics.
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23
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Rudisill SG, DiVito MD, Hubel A, Stein A. In vitro collagen fibril alignment via incorporation of nanocrystalline cellulose. Acta Biomater 2015; 12:122-128. [PMID: 25449923 DOI: 10.1016/j.actbio.2014.10.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2014] [Revised: 09/25/2014] [Accepted: 10/19/2014] [Indexed: 12/29/2022]
Abstract
This study demonstrates a method for producing ordered collagen fibrils on a similar length scale to those in the cornea, using a one-pot liquid-phase synthesis. The alignment persists throughout samples on the mm scale. The addition of nanocrystalline cellulose (NCC), a biocompatible and widely available material, to collagen prior to gelation causes the fibrils to align and achieve a narrow size distribution (36±8nm). The effects of NCC loading in the composites on microstructure, transparency and biocompatibility are studied by scanning electron microscopy, ultraviolet-visible spectroscopy and cell growth experiments. A 2% loading of NCC increases the transparency of collagen while producing an ordered microstructure. A mechanism is proposed for the ordering behavior on the basis of enhanced hydrogen bonding during collagen gel formation.
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24
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Corneal assessment technologies: Current status. Surv Ophthalmol 2014; 59:599-614. [DOI: 10.1016/j.survophthal.2014.05.001] [Citation(s) in RCA: 60] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2013] [Revised: 05/15/2014] [Accepted: 05/20/2014] [Indexed: 11/22/2022]
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25
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Biochemical properties and aggregation propensity of transforming growth factor-induced protein (TGFBIp) and the amyloid forming mutants. Ocul Surf 2014; 13:9-25. [PMID: 25557343 DOI: 10.1016/j.jtos.2014.04.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 04/01/2014] [Accepted: 04/08/2014] [Indexed: 02/07/2023]
Abstract
TGFBI-associated corneal dystrophies are characterized by accumulation of insoluble deposits of the mutant protein transforming growth factor β-induced protein (TGFBIp) in the cornea. Depending on the nature of mutation, the lesions appear as granular (non-amyloid) or lattice lines (amyloid) in the Bowman's layer or in the stroma. This review article emphasizes the structural biology aspects of TGFBIp. We discuss the tinctorial properties and ultrastructure of deposits observed in granular and lattice corneal dystrophic mutants with amyloid and non-amyloid forms of other human protein deposition diseases and review the biochemical and putative functional role of the protein. Using bioinformatics tools, we identify intrinsic aggregation propensity and discuss the possible protective role of gatekeepers close to the "aggregation-prone" regions of native TGFBIp. We describe the relative aggregation rates of lattice corneal dystrophy (LCD) and granular corneal dystrophy (GCD2) mutants using the three-parameter model, which is based on intrinsic properties of polypeptide chains. The predictive power of this model is compared with two other algorithms. We conclude that the model is able to predict the aggregation rate of mutants which do not alter overall net charge of the protein. The need to understand the mechanism of corneal dystrophies from the structural biology viewpoint is emphasized.
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26
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Takiyama N, Mizuno T, Iwai R, Uechi M, Nakayama Y. In-body tissue-engineered collagenous connective tissue membranes (BIOSHEETs) for potential corneal stromal substitution. J Tissue Eng Regen Med 2013; 10:E518-E526. [PMID: 24668614 DOI: 10.1002/term.1859] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 09/07/2013] [Accepted: 11/10/2013] [Indexed: 01/15/2023]
Abstract
There is a severe shortage of donor cornea for transplantation in many countries. Collagenous connective tissue membranes, named BIOSHEETs, grown in vivo were successfully implanted in rabbit corneal stroma for in vivo evaluation of their suitability as a corneal stromal substitute to solve this global donor shortage. BIOSHEETs were prepared by embedding silicone moulds into dorsal subcutaneous pouches in rabbits for 1 month and stored in glycerol. After re-swelling in saline and trephining, disk-shaped BIOSHEETs (4 mm diameter) were allogeneically implanted into stromal pockets prepared in the right cornea of seven rabbits. Clinical tests for corneal thickness and transparency, and tissue analyses were performed. Because the BIOSHEETs (thickness, 131 ± 14 µm) obtained were opaque immediately after implantation, the transparency of the cornea decreased. The total thickness of the BIOSHEET-implanted cornea increased from 364 ± 21.0 µm to 726 ± 131 µm. After 4 weeks' implantation, the thickness of the cornea stabilized (493 ± 80 µm at 4 weeks and 447 ± 46 µm at 8 weeks). The transparency of the cornea increased progressively with time of implantation. The random orientation of collagen fibrils in the original BIOSHEETs tended to be homogeneous, similar to that of the native stroma. No inflammatory cells accumulated and fibroblast-like cells infiltrated the implant. The BIOSHEETs showed high biocompatibility with stromal tissues; however, further studies are needed to test its functional aspects. Although this research is only intended as a proof of concept, BIOSHEETs may be considered a feasible corneal stromal replacement, especially for treating visual impairment caused by stromal haze. Copyright © 2013 John Wiley & Sons, Ltd.
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Affiliation(s)
- Naoaki Takiyama
- Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Kanagawa, Japan
| | - Takeshi Mizuno
- Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.,Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan
| | - Ryosuke Iwai
- Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan
| | - Masami Uechi
- Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Kanagawa, Japan.,Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan
| | - Yasuhide Nakayama
- Division of Medical Engineering and Materials, National Cerebral and Cardiovascular Centre Research Institute, Osaka, Japan.
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27
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McHugh KJ, Saint-Geniez M, Tao SL. Topographical control of ocular cell types for tissue engineering. J Biomed Mater Res B Appl Biomater 2013; 101:1571-84. [PMID: 23744715 PMCID: PMC4090092 DOI: 10.1002/jbm.b.32968] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2012] [Revised: 03/19/2013] [Accepted: 04/21/2013] [Indexed: 02/06/2023]
Abstract
Visual impairment affects over 285 million people worldwide and has a major impact on an individual's quality of life. Tissue engineering has the potential to increase the quality of life for many of these patients by preventing vision loss or restoring vision using cell-based therapies. However, these strategies will require an understanding of the microenvironmental factors that influence cell behavior. The eye is a well-organized organ whose structural complexity is essential for proper function. Interactions between ocular cells and their highly ordered extracellular matrix are necessary for maintaining key tissue properties including corneal transparency and retinal lamination. Therefore, it is not surprising that culturing these cells in vitro on traditional flat substrates result in irregular morphology. Instead, topographically patterned biomaterials better mimic native extracellular matrix and have been shown to elicit in vivo-like morphology and gene expression which is essential for tissue engineering. Herein we review multiple methods for producing well-controlled topography and discuss optimal biomaterial scaffold design for cells of the cornea, retina, and lens.
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Affiliation(s)
- Kevin J. McHugh
- The Charles Stark Draper Laboratory, Cambridge, MA
- Schepens Eye Research Institute, Boston, MA
- Department of Biomedical Engineering, Boston University, Boston, MA
| | - Magali Saint-Geniez
- Schepens Eye Research Institute, Boston, MA
- Department of Ophthalmology, Harvard Medical School, Boston, MA
| | - Sarah L. Tao
- The Charles Stark Draper Laboratory, Cambridge, MA
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28
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Cheng X, Pinsky PM. Mechanisms of self-organization for the collagen fibril lattice in the human cornea. J R Soc Interface 2013; 10:20130512. [PMID: 23904589 DOI: 10.1098/rsif.2013.0512] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
The transparency of the human cornea depends on the regular lattice arrangement of the collagen fibrils and on the maintenance of an optimal hydration--the achievement of both depends on the presence of stromal proteoglycans (PGs) and their linear sidechains of negatively charged glycosaminoglycans (GAGs). Although the GAGs produce osmotic pressure by the Donnan effect, the means by which they exert positional control of the lattice is less clear. In this study, a theoretical model based on equilibrium thermodynamics is used to describe restoring force mechanisms that may control and maintain the fibril lattice and underlie corneal transparency. Electrostatic-based restoring forces that result from local charge density changes induced by fibril motion, and entropic elastic restoring forces that arise from duplexed GAG structures that bridge neighbouring fibrils, are described. The model allows for the possibility that fibrils have a GAG-dense coating that adds an additional fibril force mechanism preventing fibril aggregation. Swelling pressure predictions are used to validate the model with results showing excellent agreement with experimental data over a range of hydration from 30 to 200% of normal. The model suggests that the electrostatic restoring force is dominant, with the entropic forces from GAG duplexes being an order or more smaller. The effect of a random GAG organization, as observed in recent imaging, is considered in a dynamic model of the lattice that incorporates randomness in both the spatial distribution of GAG charge and the topology of the GAG duplexes. A striking result is that the electrostatic restoring forces alone are able to reproduce the image-based lattice distribution function for the human cornea, and thus dynamically maintain the short-range order of the lattice.
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Affiliation(s)
- Xi Cheng
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
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29
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X-ray absorption near-edge structure (XANES) spectroscopy identifies differential sulfur speciation in corneal tissue. Anal Bioanal Chem 2013; 405:6613-20. [DOI: 10.1007/s00216-013-7120-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2013] [Revised: 05/27/2013] [Accepted: 06/05/2013] [Indexed: 01/26/2023]
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30
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Pandolfi A, Boschetti F. The influence of the geometry of the porcine cornea on the biomechanical response of inflation tests. Comput Methods Biomech Biomed Engin 2013; 18:64-77. [PMID: 23521091 DOI: 10.1080/10255842.2013.778983] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
To withstand the high probability of success, the growing diffusion of laser surgery for the correction of visual defects, corneal surgeons are regarding with interest numerical tools able to provide reliable predictions of the intervention outcomes. The main obstacle to the definition of a predictive numerical instrument is the objective difficulty in evaluating the in vivo mechanical properties of the human cornea. In this study, we assess the ability of a parametrised numerical model of the cornea (Pandolfi and Manganiello 2006) to describe individual pressurisation tests on whole porcine corneas once the mechanical parameters of the model have been calibrated over average data. We also aim at estimating the sensitivity of the mechanical response with the variation of basic geometrical parameters, such as the central corneal thickness, the curvature and the in-plane diameter. We conclude that the actual geometry of a cornea has a minor role in the overall mechanical response, and therefore the material properties must be considered carefully and individually in any numerical application. This study makes use of the data obtained from a wide experimental program, where a set of 21 porcine corneas has been fully characterised in terms of mechanical and geometrical properties (Boschetti et al. 2012).
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Affiliation(s)
- Anna Pandolfi
- a Laboratory of Biological Structure Mechanics , Politecnico di Milano , Milano , Italy
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31
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Labat-Robert J, Pouliquen Y, Robert L. [Eye connective tissues: cornea and vitreous body]. Biol Aujourdhui 2012; 206:145-60. [PMID: 22748052 DOI: 10.1051/jbio/2012013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Indexed: 11/15/2022]
Abstract
The authors, ophtalmologist (Y.P.) and basic scientists (J.L.-R and L.R.), collaborated on eye-research since 1962 on normal and pathological aspects of eye tissues, considered as specialized forms of connective tissues, and on specific aspects of the physiology and pathology of the eye. This date coincides with the foundation of the French Society of Connective Tissues, which celebrates the 50th anniversary of its creation. We shall present here some of our work on the ontogenetic and phylogenetic aspects of the cornea, on its structure, function and regulation in normal and pathological states, taken from a large number of publications of our laboratories. Our work on cornea started with the study of the morphogenesis of its lamellar structure, made of collagen fibers and proteoglycans. This led us to the isolation and characterization of structural (or matrix) glycoproteins, a new class of matrix components, present also in all other connective tissues, and to the study of their biosynthesis by keratocytes. Corneal wounds and regeneration were also studied, as well as some corneal pathologies such as keratoconus. The confrontation of quantitative morphological methods with biochemical procedures were to yield important results on the mechanisms of the maintenance of corneal structure and function. Another series of studies concerned the vitreous where we detected, besides previously characterized components, such as hyaluronan and collagens, fibronectin which plays an important role in the adhesion of hyaluronan to the collagen network. Its age-dependent modifications were also studied, with a special focus on the role of reactive oxygen species (ROS)-mediated degradation of hyaluronan, especially important for the aging of the vitreous.
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32
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Elavazhagan M, Lakshminarayanan R, Zhou L, Ting LW, Tong L, Beuerman RW, Chaurasia SS, Mehta JS. Expression, purification and characterization of fourth FAS1 domain of TGFβIp-associated corneal dystrophic mutants. Protein Expr Purif 2012; 84:108-15. [PMID: 22575305 DOI: 10.1016/j.pep.2012.04.018] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2012] [Accepted: 04/25/2012] [Indexed: 11/18/2022]
Abstract
Corneal dystrophies (CDs) are a group of inherited bilateral disorders affecting the corneal tissue of the eye. Most of these CDs in the stromal layer of the cornea have been associated with mutations found on the TGFBI gene that codes for a 683-amino acid transforming growth factor induced protein (TGFβIp). These mutations have been found to induce atypical aggregation and progressive accumulation of protein aggregates in the cornea that leads to loss of corneal transparency and hence blindness. At present, 65 distinct pathogenic mutations have been identified in TGFBI that are associated with different clinical phenotypes. More than 80% of these missense mutations occur in the 4th FAS (fasciclin-like) 1 domain. Current treatment includes surgical intervention, which often involves high recurrence rates. Hence, it is imperative to examine the properties of the TGFβIp and the pathogenic mutant proteins to understand the pathology of the disease mechanism and to develop potent therapeutics. Here, we report the recombinant expression, purification, characterization and the effect of four clinically significant pathogenic TGFβIp mutants - R555W, H572R, A620D, and H626R on the biophysical properties of the wild type (WT) 4th FAS1 domain of TGFβIp. While a higher proportion of the R555W, H572R and H626R mutants of the 4th FAS1 domains remained stable, the A620D mutant largely existed as inclusion bodies in native state and aggregates under physiological conditions. These mutants present a unique platform to examine protein aggregation-prone diseases wherein single amino-acid mutations present distinct pathogenic phenotypes. Though pathogenically and phenotypically diverse, these mutants do not exhibit variations in secondary structure and stability, except for the A620D mutant, when examined by CD and UV spectroscopy.
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Affiliation(s)
- Murugan Elavazhagan
- Tissue Engineering and Stem Cell Group, Singapore Eye Research Institute, Singapore
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33
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Self-assembled matrix by umbilical cord stem cells. J Funct Biomater 2011; 2:213-29. [PMID: 24956304 PMCID: PMC4030936 DOI: 10.3390/jfb2030213] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/03/2011] [Revised: 08/23/2011] [Accepted: 08/25/2011] [Indexed: 01/08/2023] Open
Abstract
Corneal integrity is critical for vision. Corneal wounds frequently heal with scarring that impairs vision. Recently, human umbilical cord mesenchymal stem cells (cord stem cells) have been investigated for tissue engineering and therapy due to their availability and differentiation potential. In this study, we used cord stem cells in a 3-dimensional (3D) stroma-like model to observe extracellular matrix organization, with human corneal fibroblasts acting as a control. For 4 weeks, the cells were stimulated with a stable Vitamin C (VitC) derivative ±TGF-β1. After 4 weeks, the mean thickness of the constructs was ∼30 μm; however, cord stem cell constructs had 50% less cells per unit volume, indicating the formation of a dense matrix. We found minimal change in decorin and lumican mRNA, and a significant increase in perlecan mRNA in the presence of TGF-β1. Keratocan on the other hand decreased with TGF-β1 in both cell lineages. With both cell types, the constructs possessed aligned collagen fibrils and associated glycosaminoglycans. Fibril diameters did not change with TGF-β1 stimulation or cell lineage; however, highly sulfated glycosaminoglycans associated with the collagen fibrils significantly increased with TGF-β1. Overall, we have shown that cord stem cells can secrete their own extracellular matrix and promote the deposition and sulfation of various proteoglycans. Furthermore, these cells are at least comparable to commonly used corneal fibroblasts and present an alternative for the 3D in vitro tissue engineered model.
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Parfitt GJ, Pinali C, Akama TO, Young RD, Nishida K, Quantock AJ, Knupp C. Electron tomography reveals multiple self-association of chondroitin sulphate/dermatan sulphate proteoglycans in Chst5-null mouse corneas. J Struct Biol 2011; 174:536-41. [PMID: 21440637 DOI: 10.1016/j.jsb.2011.03.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 03/14/2011] [Accepted: 03/20/2011] [Indexed: 11/28/2022]
Abstract
The spatial distribution of collagen fibrils in the corneal stroma is essential for corneal transparency and is primarily regulated by extrafibrillar proteoglycans, which are multi-functional polymers that interact with hybrid type I/V collagen fibrils. In order to understand more about proteoglycan organisation and collagen associations in the cornea, three-dimensional electron microscopy reconstructions of collagen-proteoglycan interactions in the anterior, mid and posterior stroma from a Chst5 knockout mouse, which lacks a keratan sulphate sulphotransferase, were obtained. Both longitudinal and transverse section show sinuous, oversized proteoglycans with near-periodic, orthogonal off-shoots. In many cases, these proteoglycans traverse over 400nm of interfibrillar space interconnecting over 10 collagen fibrils. The reconstructions suggest that multiple chondroitin sulphate/dermatan sulphate proteoglycans have aggregated laterally and, possibly, end-to-end, with orthogonal extensions protruding from the main electron-dense stained filament. We suggest possible mechanisms as to how sulphation differences may lead to this increase in aggregation of proteoglycans in the Chst5-null mouse corneal stroma and how this relates to proteoglycan packing in healthy corneas.
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Affiliation(s)
- Geraint J Parfitt
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Wales, UK.
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Palka BP, Sotozono C, Tanioka H, Akama TO, Yagi N, Boote C, Young RD, Meek KM, Kinoshita S, Quantock AJ. Structural collagen alterations in macular corneal dystrophy occur mainly in the posterior stroma. Curr Eye Res 2010; 35:580-6. [PMID: 20597644 DOI: 10.3109/02713681003760150] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
PURPOSE Collagen fibrils in the corneal stroma in macular corneal dystrophy, on average, are more closely spaced than in the normal cornea. This study was conducted to investigate if this occurs uniformly across the stroma or is more prevalent at certain stromal depths. METHODS Microbeam synchrotron X-ray fiber diffraction patterns were obtained in 25 microm steps across the whole thickness of a thin strip of a macular corneal dystrophy cornea obtained at keratoplasty. Data were analyzed for mean collagen interfibrillar spacing at all positions. Serum was analyzed immunochemically to determine immunophenotype, and transmission electron microscopy was carried out to visualize stromal ultrastructure. RESULTS Keratan sulphate was not detectable in blood serum, classifying the disease as macular corneal dystrophy type I. Collagen interfibrillar spacing dropped linearly with stromal depth from the anterior to posterior cornea, measuring 5-10% less in the posterior 100 microm of the MCD stroma compared to the anterior 100 microm (p < 0.001). Isolated pockets of collagen fibrils with unusually large diameters were identified in the deep stroma. CONCLUSIONS Collagen fibril spacing is reduced and large-diameter collagen fibrils are seen in macular corneal dystrophy type I, with the deep stroma affected more. We speculate that the ultrastructural abnormalities are more prevalent in the posterior stroma because the structural influence of sulphated keratan sulphate glycosaminoglycans/proteoglycans is high in this region of the cornea.
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Affiliation(s)
- Barbara P Palka
- School of Optometry & Vision Sciences, Cardiff University, Cardiff, United Kingdom
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Three-dimensional reconstruction of collagen–proteoglycan interactions in the mouse corneal stroma by electron tomography. J Struct Biol 2010; 170:392-7. [DOI: 10.1016/j.jsb.2010.01.019] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 01/28/2010] [Accepted: 01/28/2010] [Indexed: 11/21/2022]
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Quantock AJ, Young RD, Akama TO. Structural and biochemical aspects of keratan sulphate in the cornea. Cell Mol Life Sci 2010; 67:891-906. [PMID: 20213925 PMCID: PMC11115788 DOI: 10.1007/s00018-009-0228-7] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2009] [Revised: 12/02/2009] [Accepted: 12/04/2009] [Indexed: 12/13/2022]
Abstract
Keratan sulphate (KS) is the predominant glycosaminoglycan (GAG) in the cornea of the eye, where it exists in proteoglycan (PG) form. KS-PGs have long been thought to play a pivotal role in the establishment and maintenance of the array of regularly-spaced and uniformly- thin collagen fibrils which make up the corneal stroma. This characteristic arrangement of fibrils allows light to pass through the cornea. Indeed, perturbations to the synthesis of KS-PG core proteins in genetically altered mice lead to structural matrix alterations and corneal opacification. Similarly, mutations in enzymes responsible for the sulphation of KS-GAG chains are causative for the inherited human disease, macular corneal dystrophy, which is manifested clinically by progressive corneal cloudiness starting in young adulthood.
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