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Zhou H, Zhang S, Lei M, Cai Y, Wang H, Sun J, Cui J, Liu C, Qu X. A suture-free, shape self-adaptive and bioactive PEG-Lysozyme implant for Corneal stroma defect repair and rapid vision restoration. Bioact Mater 2023; 29:1-15. [PMID: 37456580 PMCID: PMC10338238 DOI: 10.1016/j.bioactmat.2023.05.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2023] [Revised: 04/20/2023] [Accepted: 05/09/2023] [Indexed: 07/18/2023] Open
Abstract
Corneal transplantation is a prevailing treatment to repair injured cornea and restore vision but faces the limitation of donor tissue shortage clinically. In addition, suturing-needed transplantation potentially causes postoperative complications. Herein, we design a PEG-Lysozyme injective hydrogel as a suture-free, shape self-adaptive, bioactive implant for corneal stroma defect repair. This implant experiences a sol-gel phase transition via an in situ amidation reaction between 4-arm-PEG-NHS and lysozyme. The physicochemical properties of PEG-Lysozyme can be tuned by the components ratio, which confers the implant mimetic corneal modulus and provides tissue adhesion to endure increased intraocular pressure. In vitro tests prove that the implant is beneficial to Human corneal epithelial cells growth and migration due to the bioactivity of lysozyme. Rabbit lamellar keratoplasty experiment demonstrates that the hydrogel can be filled into defect to form a shape-adaptive implant adhered to native stroma. The implant promotes epithelialization and stroma integrity, recovering the topology of injured cornea to normal. A newly established animal forging behavior test prove a rapid visual restoration of rabbits when use implant in a suture free manner. In general, this work provides a promising preclinical practice by applicating a self-curing, shape self-adaptive and bioactive PEG-Lysozyme implant for suture-free stroma repair.
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Affiliation(s)
- Hang Zhou
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Material Science and Engineering, Frontiers Science Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai, 200237, China
| | - Shaohua Zhang
- Eye Institute and Department of Ophthalmology, NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai Key Laboratory of Visual Impairment and Restoration, Eye & ENT Hospital, Fudan University, Shanghai, 200031, China
| | - Miao Lei
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Material Science and Engineering, Frontiers Science Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai, 200237, China
| | - Yixin Cai
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Material Science and Engineering, Frontiers Science Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai, 200237, China
| | - Honglei Wang
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Material Science and Engineering, Frontiers Science Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai, 200237, China
| | - Jianguo Sun
- Eye Institute and Department of Ophthalmology, NHC Key Laboratory of Myopia (Fudan University), Key Laboratory of Myopia, Chinese Academy of Medical Sciences, Shanghai Key Laboratory of Visual Impairment and Restoration, Eye & ENT Hospital, Fudan University, Shanghai, 200031, China
| | - Jingyuan Cui
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Material Science and Engineering, Frontiers Science Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai, 200237, China
- Wenzhou Institute of Shanghai University, Wenzhou, 325000, China
| | - Changsheng Liu
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Material Science and Engineering, Frontiers Science Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai, 200237, China
| | - Xue Qu
- Key Laboratory for Ultrafine Materials of Ministry of Education, School of Material Science and Engineering, Frontiers Science Center for Materiobiology and Dynamic Chemistry, East China University of Science and Technology, Shanghai, 200237, China
- Wenzhou Institute of Shanghai University, Wenzhou, 325000, China
- Shanghai Frontier Science Center of Optogenetic Techniques for Cell Metabolism, Shanghai, 200237, China
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2
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Garcin T, Gauthier AS, Crouzet E, He Z, Herbepin P, Perrache C, Acquart S, Cognasse F, Forest F, Thuret G, Gain P. Innovative corneal active storage machine for long-term eye banking. Am J Transplant 2019; 19:1641-1651. [PMID: 30589181 DOI: 10.1111/ajt.15238] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2018] [Revised: 12/11/2018] [Accepted: 12/18/2018] [Indexed: 01/25/2023]
Abstract
Optimal ex vivo corneal storage in eye banks is crucial to increase both the number of corneas suitable for graft and their intrinsic quality, mainly the number of viable endothelial cells, which dictates graft survival in recipients. With both passive storage methods used worldwide (short-term cold storage in the United States, long-term organ culture in Europe), significant endothelial cell loss is inevitable. Here we show that, with an active storage machine, also called a bioreactor, which restores 2 fundamental physiological parameters, intraocular pressure and medium renewal, endothelial cell survival is improved by 23% compared with organ culture after 4 weeks' storage. Also observed in the bioreactor is a 4-fold higher expression of Na+ /K+ ATPase, which supports one of the major endothelial cell pumping functions. In addition, corneas remain thin and transparent, so they are suitable for surgery at any time. This new active eye banking method may help to reduce the severe global scarcity of donor corneas.
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Affiliation(s)
- Thibaud Garcin
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France.,Ophthalmology Department, University Hospital, Saint-Etienne, France
| | - Anne-Sophie Gauthier
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France
| | - Emmanuel Crouzet
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France
| | - Zhiguo He
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France
| | - Pascal Herbepin
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France
| | - Chantal Perrache
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France
| | | | | | - Fabien Forest
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France.,Pathology Department, University Hospital, Saint-Etienne, France
| | - Gilles Thuret
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France.,Ophthalmology Department, University Hospital, Saint-Etienne, France.,Institut Universitaire de France, Boulevard Saint-Michel, Paris, France
| | - Philippe Gain
- Corneal Graft Biology, Engineering and Imaging Laboratory, BiiGC, EA2521, Federative Institute of Research in Sciences and Health Engineering, Faculty of Medicine, Jean Monnet University, Saint-Etienne, France.,Ophthalmology Department, University Hospital, Saint-Etienne, France
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3
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Affiliation(s)
- Young Hyun Kim
- Vision Science Graduate Group, University of California, Berkeley, CA, USA
- Clinical Research Center, School of Optometry, University of California, Berkeley, CA, USA
- Chemical and Biomolecular Engineering Department, University of California, Berkeley, CA, USA
| | - Bo Tan
- Clinical Research Center, School of Optometry, University of California, Berkeley, CA, USA
| | - Meng C. Lin
- Vision Science Graduate Group, University of California, Berkeley, CA, USA
- Clinical Research Center, School of Optometry, University of California, Berkeley, CA, USA
| | - Clayton J. Radke
- Vision Science Graduate Group, University of California, Berkeley, CA, USA
- Chemical and Biomolecular Engineering Department, University of California, Berkeley, CA, USA
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4
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Baturina GS, Katkova LE, Kolosova NG, Solenov EI. Age-Related Changes in Water Transport by Corneal Endothelial Cells in Rats. ADVANCES IN GERONTOLOGY 2018. [DOI: 10.1134/s2079057018020029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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5
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Nims RJ, Ateshian GA. Reactive Constrained Mixtures for Modeling the Solid Matrix of Biological Tissues. JOURNAL OF ELASTICITY 2017; 129:69-105. [PMID: 38523894 PMCID: PMC10959290 DOI: 10.1007/s10659-017-9630-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Indexed: 03/26/2024]
Abstract
This article illustrates our approach for modeling the solid matrix of biological tissues using reactive constrained mixtures. Several examples are presented to highlight the potential benefits of this approach, showing that seemingly disparate fields of mechanics and chemical kinetics are actually closely interrelated and may be elegantly expressed in a unified framework. Thus, constrained mixture models recover classical theories for fibrous materials with bundles oriented in different directions or having different reference configurations, that produce characteristic fiber recruitment patterns under loading. Reactions that exchange mass among various constituents of a mixture may be used to describe tissue growth and remodeling, which may also alter the material's anisotropy. Similarly, reactions that describe the breaking and reforming of bonds may be used to model free energy dissipation in a viscoelastic material. Therefore, this framework is particularly well suited for modeling biological tissues.
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Affiliation(s)
- Robert J Nims
- Columbia University, 500 West 120th St, MC4703, New York, NY 10027, USA
| | - Gerard A Ateshian
- Columbia University, 500 West 120th St, MC4703, New York, NY 10027, USA
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Filev F, Oezcan C, Feuerstacke J, Linke SJ, Wulff B, Hellwinkel OJC. Semi-quantitative assessments of dextran toxicity on corneal endothelium: conceptual design of a predictive algorithm. Cell Tissue Bank 2016; 18:91-98. [DOI: 10.1007/s10561-016-9596-z] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2016] [Accepted: 10/24/2016] [Indexed: 10/20/2022]
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Role of the Endothelial Layer in the Deswelling Process of Organ-Cultured Human Corneas Before Transplantation. Cornea 2016; 35:1216-21. [DOI: 10.1097/ico.0000000000000937] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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8
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Abstract
Corneal endothelial cells (CECs) are terminally differentiated cells, specialized in regulating corneal hydration and transparency. They are highly polarized flat cells that separate the cornea from the aqueous humor. Their apical surface, in contact with aqueous humor is hexagonal, whereas their basal surface is irregular. We characterized the structure of human CECs in 3D using confocal microscopy of immunostained whole corneas in which cells and their interrelationships remain intact. Hexagonality of the apical surface was maintained by the interaction between tight junctions and a submembraneous network of actomyosin, braced like a drum. Lateral membranes, which support enzymatic pumps, presented complex expansions resembling interdigitated foot processes at the basal surface. Using computer-aided design and drafting software, we obtained a first simplified 3D model of CECs. By comparing their expression with those in epithelial, stromal and trabecular corneal cells, we selected 9 structural or functional proteins for which 3D patterns were specific to CECs. This first 3D map aids our understanding of the morphologic and functional specificity of CECs and could be used as a reference for characterizing future cell therapy products destined to treat endothelial dysfunctions.
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9
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Cheng X, Petsche SJ, Pinsky PM. A structural model for the in vivo human cornea including collagen-swelling interaction. J R Soc Interface 2016; 12:20150241. [PMID: 26156299 DOI: 10.1098/rsif.2015.0241] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
A structural model of the in vivo cornea, which accounts for tissue swelling behaviour, for the three-dimensional organization of stromal fibres and for collagen-swelling interaction, is proposed. Modelled as a binary electrolyte gel in thermodynamic equilibrium, the stromal electrostatic free energy is based on the mean-field approximation. To account for active endothelial ionic transport in the in vivo cornea, which modulates osmotic pressure and hydration, stromal mobile ions are shown to satisfy a modified Boltzmann distribution. The elasticity of the stromal collagen network is modelled based on three-dimensional collagen orientation probability distributions for every point in the stroma obtained by synthesizing X-ray diffraction data for azimuthal angle distributions and second harmonic-generated image processing for inclination angle distributions. The model is implemented in a finite-element framework and employed to predict free and confined swelling of stroma in an ionic bath. For the in vivo cornea, the model is used to predict corneal swelling due to increasing intraocular pressure (IOP) and is adapted to model swelling in Fuchs' corneal dystrophy. The biomechanical response of the in vivo cornea to a typical LASIK surgery for myopia is analysed, including tissue fluid pressure and swelling responses. The model provides a new interpretation of the corneal active hydration control (pump-leak) mechanism based on osmotic pressure modulation. The results also illustrate the structural necessity of fibre inclination in stabilizing the corneal refractive surface with respect to changes in tissue hydration and IOP.
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Affiliation(s)
- Xi Cheng
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Steven J Petsche
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
| | - Peter M Pinsky
- Department of Mechanical Engineering, Stanford University, Stanford, CA, USA
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10
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Ateshian GA, Maas S, Weiss JA. Multiphasic finite element framework for modeling hydrated mixtures with multiple neutral and charged solutes. J Biomech Eng 2014; 135:111001. [PMID: 23775399 DOI: 10.1115/1.4024823] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 06/17/2013] [Indexed: 11/08/2022]
Abstract
Computational tools are often needed to model the complex behavior of biological tissues and cells when they are represented as mixtures of multiple neutral or charged constituents. This study presents the formulation of a finite element modeling framework for describing multiphasic materials in the open-source finite element software febio.1 Multiphasic materials may consist of a charged porous solid matrix, a solvent, and any number of neutral or charged solutes. This formulation proposes novel approaches for addressing several challenges posed by the finite element analysis of such complex materials: The exclusion of solutes from a fraction of the pore space due to steric volume and short-range electrostatic effects is modeled by a solubility factor, whose dependence on solid matrix deformation and solute concentrations may be described by user-defined constitutive relations. These solute exclusion mechanisms combine with long-range electrostatic interactions into a partition coefficient for each solute whose value is dependent upon the evaluation of the electric potential from the electroneutrality condition. It is shown that this electroneutrality condition reduces to a polynomial equation with only one valid root for the electric potential, regardless of the number and valence of charged solutes in the mixture. The equation of charge conservation is enforced as a constraint within the equation of mass balance for each solute, producing a natural boundary condition for solute fluxes that facilitates the prescription of electric current density on a boundary. It is also shown that electrical grounding is necessary to produce numerical stability in analyses where all the boundaries of a multiphasic material are impermeable to ions. Several verification problems are presented that demonstrate the ability of the code to reproduce known or newly derived solutions: (1) the Kedem-Katchalsky model for osmotic loading of a cell; (2) Donnan osmotic swelling of a charged hydrated tissue; and (3) current flow in an electrolyte. Furthermore, the code is used to generate novel theoretical predictions of known experimental findings in biological tissues: (1) current-generated stress in articular cartilage and (2) the influence of salt cation charge number on the cartilage creep response. This generalized finite element framework for multiphasic materials makes it possible to model the mechanoelectrochemical behavior of biological tissues and cells and sets the stage for the future analysis of reactive mixtures to account for growth and remodeling.
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Hatami-Marbini H, Etebu E. Hydration dependent biomechanical properties of the corneal stroma. Exp Eye Res 2013; 116:47-54. [DOI: 10.1016/j.exer.2013.07.016] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 06/21/2013] [Accepted: 07/15/2013] [Indexed: 11/17/2022]
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Abstract
The ability to clearly observe one's environment in the visible spectrum provides a tremendous evolutionary advantage in most of the world's habitats. The complex optical processing system that has evolved in higher vertebrate animals gathers, focuses, detects, transduces, and interprets incoming visible light. The cornea resides at the front end of this imaging system, where it provides a clear optical aperture, substantial refractive power, and the structural stability required to protect the fragile intraocular components. Nature has resolved these simultaneous design requirements through an exceedingly clever manipulation of common extracellular-matrix structural materials (e.g., collagen and proteoglycans). In this review, we (a) examine the biophysical and optical roles of the cornea, (b) discuss increasingly popular approaches to altering its natural refractive properties with an emphasis on biomechanics, and (c) investigate the fast-rising science of corneal replacement via synthetic biomaterials. We close by considering relevant open problems that would benefit from the increased attention of bioengineers.
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Affiliation(s)
- Jeffrey W Ruberti
- Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA
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13
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Leung BK, Bonanno JA, Radke CJ. Oxygen-deficient metabolism and corneal edema. Prog Retin Eye Res 2011; 30:471-92. [PMID: 21820076 DOI: 10.1016/j.preteyeres.2011.07.001] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2011] [Revised: 07/14/2011] [Accepted: 07/16/2011] [Indexed: 11/18/2022]
Abstract
Wear of low-oxygen-transmissible soft contact lenses swells the cornea significantly, even during open eye. Although oxygen-deficient corneal edema is well-documented, a self-consistent quantitative prediction based on the underlying metabolic reactions is not available. We present a biochemical description of the human cornea that quantifies hypoxic swelling through the coupled transport of water, salt, and respiratory metabolites. Aerobic and anaerobic consumption of glucose, as well as acidosis and pH buffering, are incorporated in a seven-layer corneal model (anterior chamber, endothelium, stroma, epithelium, postlens tear film, contact lens, and prelens tear film). Corneal swelling is predicted from coupled transport of water, dissolved salts, and especially metabolites, along with membrane-transport resistances at the endothelium and epithelium. At the endothelium, the Na+/K+ - ATPase electrogenic channel actively transports bicarbonate ion from the stroma into the anterior chamber. As captured by the Kedem-Katchalsky membrane-transport formalism, the active bicarbonate-ion flux provides the driving force for corneal fluid pump-out needed to match the leak-in tendency of the stroma. Increased lactate-ion production during hypoxia osmotically lowers the pump-out rate requiring the stroma to swell to higher water content. Concentration profiles are predicted for glucose, water, oxygen, carbon dioxide, and hydronium, lactate, bicarbonate, sodium, and chloride ions, along with electrostatic potential and pressure profiles. Although the active bicarbonate-ion pump at the endothelium drives bicarbonate into the aqueous humor, we find a net flux of bicarbonate ion into the cornea that safeguards against acidosis. For the first time, we predict corneal swelling upon soft-contact-lens wear from fundamental biophysico-chemical principles. We also successfully predict that hypertonic tear alleviates contact-lens-induced edema.
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Affiliation(s)
- B K Leung
- Chemical and Biomolecular Engineering Department, University of California, Berkeley, CA 94720, USA
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14
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Grueterich M, Messmer EM, Lackerbauer C, Kampik A. Lamellar keratoplasty with a novel anterior chamber system and organ cultured donor corneas. Eur J Ophthalmol 2009; 20:276-82. [PMID: 19967666 DOI: 10.1177/112067211002000204] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
PURPOSE To present a novel artificial anterior chamber system for anterior and posterior lamellar keratoplasty. METHODS The artificial anterior chamber system MOZARTTM in conjunction with the AMADEUSTM II microkeratome was evaluated for its applicability in anterior and posterior lamellar keratoplasty using organ cultured donor corneas. RESULTS Twelve patients underwent microkeratome-assisted lamellar keratoplasty for corneal opacifications due to either anterior stromal scaring or endothelial decompensation. Eight patients underwent Descemet stripping automated endothelial keratoplasty (DSAEK) and 4 patients underwent anterior lamellar keratoplasty (ALK). A 400-microm and 250-microm cutting head was used for DSAEK and ALK, respectively. In all patients, an 8.5-mm suction ring was applied. For the 250-microm cutting head, a mean anterior lamella thickness of 244+/-12 microm was found. For the 400-microm cutting head, a mean anterior lamella thickness of 390+/-18 microm was found. The graft diameter was 8.85+/-0.5 mm for the 8.5-mm suction ring with both cutting heads. Deswelling of the anterior donor lamella was 11.5% compared to 30% of the posterior lamella transplant after 6 months of follow-up. CONCLUSION The AMADEUSTM II microkeratome in conjunction with the MOZARTTM artificial anterior chamber system proved to be a suitable device for modern lamellar keratoplasty. Swelling and deswelling characteristics of organ cultured corneas need to be further investigated to optimize the deswelling time prior to donor cornea sectioning in lamellar keratoplasty.
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Affiliation(s)
- Martin Grueterich
- Department of Ophthalmology, Ludwig-Maximilians University, Munich, Germany.
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15
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Abstract
PURPOSE During deswelling of organ-cultured human corneas, endothelial cell loss occurs. Therefore, it is necessary to minimize the deswelling time and achieving an optimal central corneal thickness (CCT) of approximately 550 microm at the same time. We investigated the minimal deswelling time necessary and analyzed endothelial cell loss. METHODS Fifty-eight human corneas were stored between 13 and 81 days in organ culture. CCT was measured by optical coherence tomography. Measurements were performed before preparation, during culturing, before deswelling, and after varying deswelling periods (1-72 hours) using 5% dextran. Additionally, vital staining was performed in 6 human corneas to assess endothelial cell loss between 24 and 30 hours of deswelling. To evaluate absolute cell loss, endothelial cells were counted on human corneal pairs after 24 and 30 hours of deswelling. RESULTS After organ culture, mean CCT was 1194 microm. After 24 hours of deswelling in dextran-containing medium, mean CCT was 600 microm, whereas after 30 hours, mean CCT was 510 microm and hardly any corneas showed a CCT of more than 550 microm. Almost no further decrease in CCT was observed thereafter. No factors could be identified predicting the necessary deswelling time; however, paired corneas showed significant correlation of deswelling characteristics. We did not see any differences in endothelial cell loss 24 and 30 hours of deswelling or the ratio of living to dead endothelial cell counts. CONCLUSIONS Deswelling for 24 hours does not provide an optimal corneal thickness. Because endothelial cell loss does not increase between 24 and 30 hours of deswelling, a period of 30 hours is more suitable for obtaining sufficient corneal thickness.
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Ateshian GA, Friedman MH. Integrative biomechanics: A paradigm for clinical applications of fundamental mechanics. J Biomech 2009; 42:1444-1451. [DOI: 10.1016/j.jbiomech.2009.04.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2008] [Revised: 03/27/2009] [Accepted: 04/04/2009] [Indexed: 11/26/2022]
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17
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Volumetric and ionic regulation during the in vitro development of a corneal endothelial barrier. Exp Eye Res 2008; 86:758-69. [PMID: 18384772 DOI: 10.1016/j.exer.2008.02.003] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Revised: 02/14/2008] [Accepted: 02/14/2008] [Indexed: 12/13/2022]
Abstract
Corneal endothelium is responsible for generating an ion flux between the corneal stroma and the anterior chamber of the eye that is necessary for the cornea to remain transparent. However, the ion transport regulatory mechanisms that develop during the formation of the endothelial barrier are not known. In this study, we determined the influence of cell confluence on cell volume and intracellular ionic content on the corneal endothelial cells of rabbits. Our results demonstrate that non-confluent endothelial cells display a hypertrophic volume increase, with higher intracellular contents of potassium and chlorine than those of confluent cells. In contrast, when cells reach confluence and the endothelial barrier forms, cell volume decreases and the intracellular contents of potassium and chlorine decrease. Our genetic analysis showed a higher expression of CFTR and CA2 genes in non-confluent cells, and of the gene KCNC3 in confluent cells. These results suggest that the normal ionic current that keeps the corneal stroma dehydrated and transparent is regulated by cell-cell contacts and endothelial cell confluence, and could explain why the loss of corneal endothelial cells is often associated with corneal edema and even blindness.
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Mergler S, Pleyer U. The human corneal endothelium: new insights into electrophysiology and ion channels. Prog Retin Eye Res 2007; 26:359-78. [PMID: 17446115 DOI: 10.1016/j.preteyeres.2007.02.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The corneal endothelium is a monolayer that mediates the flux of solutes and water across the posterior corneal surface. Thereby, it plays an essential role to maintain the transparency of the cornea. Unlike the epithelium, the human endothelium is an amitotic cell layer with a critical cell density and the risk of corneal decompensation. The number of endothelial cells subsequently decreases with age. Moreover, the endothelial cell loss is accelerated after various impairments such as surgical trauma (e.g. cataract extraction) and following corneal transplantation. This cell loss is associated with programmed cell death (apoptosis) and changed ion channel activity. However, little is known about the electrophysiology and ion channel expression (in particular Ca2+ channels) in corneal endothelial cells. This article reviews our current knowledge about the electrophysiology of the corneal endothelium. It highlights ion channel expression, which may have a major role in corneal cell physiology and pathological events. A better understanding of the (electro)physiological function of the cornea may lead to the development of clinical relevant new therapeutic and preventive measures.
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Affiliation(s)
- Stefan Mergler
- Department of Ophthalmology, Charité-University Medicine Berlin, Campus Virchow-Clinic, Augustenburger Platz 1, 13353 Berlin, Germany.
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19
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Park CY, Zhu Z, Zhang C, Moon CS, Chuck RS. Cellular redox state predicts in vitro corneal endothelial cell proliferation capacity. Exp Eye Res 2006; 83:903-10. [PMID: 16806172 DOI: 10.1016/j.exer.2006.04.015] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Revised: 04/26/2006] [Accepted: 04/28/2006] [Indexed: 12/13/2022]
Abstract
Cellular redox state using the non-invasive mitochondrial autofluorescence technique of redox fluorometry was evaluated as a predictor for corneal endothelial proliferative capacity in vitro. Human corneal endothelial cells (HCEC) harvested from eye bank corneas were cultured in plates with two different coating substrates; type I collagen and poly-D-lysine. Cellular autofluorescence was measured with both DAPI (excitation: G365, emission: bandpass 445/50) and FITC (excitation: bandpass 450-490, emission bandpass 515-565) filter sets on days 3, 5, 7, and 14. The redox fluorometric ratio was calculated as net "DAPI" signal intensity divided by net "FITC" signal intensity. Normalized redox ratio was calculated as redox ratio divided by individual cell size. Cellular proliferation was analyzed by live cell count on days 2, 7, and 14. Mitochondrial staining was performed on days 4 and 14. The poly-d-lysine substrate decreased the proliferation capacity of HCEC in comparison to type I collagen out to 2 weeks (p=0.045). The cellular redox fluorometric ratio decreased significantly as the cells proliferated (p<0.001). The cells cultured on type I collagen coated plates exhibited significantly lower redox fluorometric ratios than cells cultured on poly-D-lysine coated plates at day 7 (p=0.015). Normalized redox ratio showed significantly lower value in type I collagen coated plates at days 7 (p=0.015) and 14 (p=0.039). Correlated cell proliferation capacity was significantly higher on type I collagen coating at days 7 and 14 (p=0.045 and p=0.049 respectively). HCECs showed different growth potential in vitro on different culture surface coating agents. This difference was well correlated with cellular redox ratios determined using redox fluorometry. Cellular redox ratio can be a potential predictor of cellular proliferation capacity.
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Affiliation(s)
- Choul Yong Park
- Department of Ophthalmology, Wilmer Ophthalmological Institute, Johns Hopkins University, 255 Woods Building, 600 North Wolfe Street, Baltimore, MD 21287, USA
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Abstract
This paper presents a numerical study on the transport of ions and ionic solution in human corneas and the corresponding influences on corneal hydration. The transport equations for each ionic species and ionic solution within the corneal stroma are derived based on the transport processes developed for electrolytic solutions, whereas the transport across epithelial and endothelial membranes is modelled by using phenomenological equations derived from the thermodynamics of irreversible processes. Numerical examples are provided for both human and rabbit corneas, from which some important features are highlighted.
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Affiliation(s)
- Long-yuan Li
- School of Engineering and Applied Science, Aston University, Birmingham B4 7ET, UK.
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Li LY, Tighe BJ, Ruberti JW. Mathematical modelling of corneal swelling. Biomech Model Mechanobiol 2004; 3:114-23. [PMID: 15378390 DOI: 10.1007/s10237-004-0054-7] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2004] [Accepted: 07/29/2004] [Indexed: 11/26/2022]
Abstract
This paper presents a differential model of the corneal transport system capable of modelling thickness changes in response to osmotic perturbations applied to either limiting membrane. The work is directed towards understanding corneal behaviour in vivo. The model considers the coupled viscous flows within the corneal stroma and across the epithelial and endothelial membranes. The flows within the stroma are established based on transport theory in porous media, while the flows across the membranes are described using the phenomenological equations of irreversible thermodynamics. The ability of the numerical model to reproduce corneal thickness changes in response to endothelial perturbations was tested against available experimental data. The sensitivity of the model to changes in stromal and membrane transport coefficients was examined.
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Affiliation(s)
- L Y Li
- School of Engineering and Applied Science, Aston University, B4 7ET, Birmingham, UK.
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Wu JZ, Herzog W. Simulating the swelling and deformation behaviour in soft tissues using a convective thermal analogy. Biomed Eng Online 2002; 1:8. [PMID: 12685940 PMCID: PMC443818 DOI: 10.1186/1475-925x-1-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2002] [Accepted: 12/19/2002] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND It is generally accepted that cartilage adaptation and degeneration are mechanically mediated. Investigating the swelling behaviour of cartilage is important because the stress and strain state of cartilage is associated with the swelling and deformation behaviour. It is well accepted that the swelling of soft tissues is associated with mechanical, chemical, and electrical events. METHOD The purpose of the present study was to implement the triphasic theory into a commercial finite element tool (ABAQUS) to solve practical problems in cartilage mechanics. Because of the mathematical identity between thermal and mass diffusion processes, the triphasic model was transferred into a convective thermal diffusion process in the commercial finite element software. The problem was solved using an iterative procedure. RESULTS The proposed approach was validated using the one-dimensional numerical solutions and the experimental results of confined compression of articular cartilage described in the literature. The time-history of the force response of a cartilage specimen in confined compression, which was subjected to swelling caused by a sudden change of saline concentration, was predicted using the proposed approach and compared with the published experimental data. CONCLUSION The advantage of the proposed thermal analogy technique over previous studies is that it accounts for the convective diffusion of ion concentrations and the Donnan osmotic pressure in the interstitial fluid.
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Affiliation(s)
- John Z Wu
- National Institute for Occupational Safety and Health, Morgantown, West Virginia, USA
| | - Walter Herzog
- Human Performance Laboratory, Faculty of Kinesiology, The University of Calgary, Calgary, Alberta, Canada
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