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Cheng KKW, Fingerhut L, Duncan S, Prajna NV, Rossi AG, Mills B. In Vitro and Ex Vivo Models of Microbial Keratitis: Present and Future. Prog Retin Eye Res 2024:101287. [PMID: 39004166 DOI: 10.1016/j.preteyeres.2024.101287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2024] [Revised: 07/09/2024] [Accepted: 07/10/2024] [Indexed: 07/16/2024]
Abstract
Microbial keratitis (MK) is an infection of the cornea, caused by bacteria, fungi, parasites, or viruses. MK leads to significant morbidity, being the fifth leading cause of blindness worldwide. There is an urgent requirement to better understand pathogenesis in order to develop novel diagnostic and therapeutic approaches to improve patient outcomes. Many in vitro, ex vivo and in vivo MK models have been developed and implemented to meet this aim. Here, we present current in vitro and ex vivo MK model systems, examining their varied design, outputs, reporting standards, and strengths and limitations. Major limitations include their relative simplicity and the perceived inability to study the immune response in these MK models, an aspect widely accepted to play a significant role in MK pathogenesis. Consequently, there remains a dependence on in vivo models to study this aspect of MK. However, looking to the future, we draw from the broader field of corneal disease modelling, which utilises, for example, three-dimensional co-culture models and dynamic environments observed in bioreactors and organ-on-a-chip scenarios. These remain unexplored in MK research, but incorporation of these approaches will offer further advances in the field of MK corneal modelling, in particular with the focus of incorporation of immune components which we anticipate will better recapitulate pathogenesis and yield novel findings, therefore contributing to the enhancement of MK outcomes.
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Affiliation(s)
- Kelvin Kah Wai Cheng
- Centre for Inflammation Research, Institute of Regeneration and Repair, University of Edinburgh, United Kingdom
| | - Leonie Fingerhut
- Centre for Inflammation Research, Institute of Regeneration and Repair, University of Edinburgh, United Kingdom
| | - Sheelagh Duncan
- Centre for Inflammation Research, Institute of Regeneration and Repair, University of Edinburgh, United Kingdom
| | - N Venkatesh Prajna
- Department of Cornea and Refractive Surgery Services, Aravind Eye Hospital and Postgraduate Institute of Ophthalmology, Madurai, Tamil Nadu, India
| | - Adriano G Rossi
- Centre for Inflammation Research, Institute of Regeneration and Repair, University of Edinburgh, United Kingdom
| | - Bethany Mills
- Centre for Inflammation Research, Institute of Regeneration and Repair, University of Edinburgh, United Kingdom.
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2
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Vij P, Brinkman A, Koch RM, DeGeorge G, Wolter M. Ocular irritation reversibility assessment of a laundry detergent using the Porcine Corneal Opacity Reversibility Assay (PorCORA): a focused study. Cutan Ocul Toxicol 2024; 43:75-86. [PMID: 38099874 DOI: 10.1080/15569527.2023.2284146] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2023] [Accepted: 11/12/2023] [Indexed: 03/09/2024]
Abstract
Consumer product manufacturers utilise a spectrum of alternative ocular irritation assays, as these tests do not require the use of live animals. Despite their usefulness, no regulatory-accepted assay assesses the reversibility of ocular damage, a key criterion of GHS ocular classification, like the rabbit eye test (i.e., Draize Rabbit Eye Test [DRET]) . The Porcine Corneal Opacity Reversibility Assay (PorCORA), an ex vivo intact corneal tissue culture model, predicts the reversibility of damage by ocular irritants. Inclusion of the damage reversibility endpoint in the PorCORA supplements other alternative test methods for ocular irritation, by assessing induced eye damage and the ability of this damage to reverse (heal) without the use of live animals to distinguish between Globally Harmonised System of Classification and Labelling of Chemicals (GHS) ocular classifications. In this focused study, results of a Bovine Corneal Opacity and Permeability (BCOP) test of a laundry detergent, neat and 10% dilution, (product mixture from S.C. Johnson & Son, Inc. [SCJ]) classified the product into GHS Category 1; however, the BCOP test cannot assess the reversibility of ocular damage. The laundry detergent was evaluated using the PorCORA, where ocular damage induced by the detergent was fully reversed within seven days. Evaluation of the reversibility of ocular damage using the PorCORA in this focused study can add strength to the weight-of-evidence (WoE) analysis approach in ocular hazard assessment. This WoE approach strengthens the argument that the PorCORA can be used to supplement BCOP data, and that this laundry detergent is not an irreversible eye irritant.
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Affiliation(s)
- Puneet Vij
- MB Research Laboratories, Spinnerstown, PA, USA
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3
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Wyroślak-Bednarek D, Skrzypska M, Górnik A, Jurowski P. Selective Bowman's layer transplantation in the treatment of neurotrophic corneal ulcers. Indian J Ophthalmol 2024; 72:S308-S311. [PMID: 38271428 DOI: 10.4103/ijo.ijo_1371_23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 07/12/2023] [Indexed: 01/27/2024] Open
Abstract
The aim of this paper is to present the surgical technique of selective Bowman's layer transplantation as well as the results of the surgery in patients with trophic corneal ulcers. The methodology of the study included three eyes from three patients with neurotrophic corneal ulcers grafting with corneal Bowman's layer. Pre- and postoperative analyses of the anterior segment of the eye were based on optical coherence tomography and slit-lamp assessment. Postoperatively a gradual corneal stroma restoration and fast corneal epithelialization were noticed. Based on our observations, the stiff and firm structure of Bowman's layer is supposed to strengthen the corneal surface and maintain its shape. It acts also as an antipathogen and antitoxin corneal barrier. Application of this acellular corneal layer transplantation to cover trophic corneal ulcers is an interesting, modern and crucial method of neurotrophic keratitis treatment.
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Affiliation(s)
- Diana Wyroślak-Bednarek
- Department of Ophthalmology and Visual Rehabilitation, Veterans Central Hospital, Lodz, Poland
- Department of Ophthalmology and Visual Rehabilitation, Medical University of Lodz, Poland
| | - Milena Skrzypska
- Department of Ophthalmology and Visual Rehabilitation, Veterans Central Hospital, Lodz, Poland
- Department of Ophthalmology and Visual Rehabilitation, Medical University of Lodz, Poland
| | - Anna Górnik
- Department of Ophthalmology and Visual Rehabilitation, Veterans Central Hospital, Lodz, Poland
- Department of Ophthalmology and Visual Rehabilitation, Medical University of Lodz, Poland
| | - Piotr Jurowski
- Department of Ophthalmology and Visual Rehabilitation, Veterans Central Hospital, Lodz, Poland
- Department of Ophthalmology and Visual Rehabilitation, Medical University of Lodz, Poland
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4
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Kumar R, Sinha NR, Mohan RR. Corneal gene therapy: Structural and mechanistic understanding. Ocul Surf 2023; 29:279-297. [PMID: 37244594 DOI: 10.1016/j.jtos.2023.05.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Revised: 05/18/2023] [Accepted: 05/22/2023] [Indexed: 05/29/2023]
Abstract
Cornea, a dome-shaped and transparent front part of the eye, affords 2/3rd refraction and barrier functions. Globally, corneal diseases are the leading cause of vision impairment. Loss of corneal function including opacification involve the complex crosstalk and perturbation between a variety of cytokines, chemokines and growth factors generated by corneal keratocytes, epithelial cells, lacrimal tissues, nerves, and immune cells. Conventional small-molecule drugs can treat mild-to-moderate traumatic corneal pathology but requires frequent application and often fails to treat severe pathologies. The corneal transplant surgery is a standard of care to restore vision in patients. However, declining availability and rising demand of donor corneas are major concerns to maintain ophthalmic care. Thus, the development of efficient and safe nonsurgical methods to cure corneal disorders and restore vision in vivo is highly desired. Gene-based therapy has huge potential to cure corneal blindness. To achieve a nonimmunogenic, safe and sustained therapeutic response, the selection of a relevant genes, gene editing methods and suitable delivery vectors are vital. This article describes corneal structural and functional features, mechanistic understanding of gene therapy vectors, gene editing methods, gene delivery tools, and status of gene therapy for treating corneal disorders, diseases, and genetic dystrophies.
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Affiliation(s)
- Rajnish Kumar
- Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, 65201, USA; One-health One-medicine Vision Research Program, Departments of Veterinary Medicine and Surgery & Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA; Amity Institute of Biotechnology, Amity University Uttar Pradesh, Lucknow campus, UP, 226028, India
| | - Nishant R Sinha
- Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, 65201, USA; One-health One-medicine Vision Research Program, Departments of Veterinary Medicine and Surgery & Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA
| | - Rajiv R Mohan
- Harry S. Truman Memorial Veterans' Hospital, Columbia, MO, 65201, USA; One-health One-medicine Vision Research Program, Departments of Veterinary Medicine and Surgery & Biomedical Sciences, College of Veterinary Medicine, University of Missouri, Columbia, MO, 65211, USA; Mason Eye Institute, School of Medicine, University of Missouri, Columbia, MO, 65212, USA.
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5
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Wilson SE. The Cornea: No Difference in the Wound Healing Response to Injury Related to Whether, or Not, There's a Bowman's Layer. Biomolecules 2023; 13:biom13050771. [PMID: 37238641 DOI: 10.3390/biom13050771] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 04/10/2023] [Accepted: 04/16/2023] [Indexed: 05/28/2023] Open
Abstract
Bowman's layer is an acellular layer in the anterior stroma found in the corneas of humans, most other primates, chickens, and some other species. Many other species, however, including the rabbit, dog, wolf, cat, tiger, and lion, do not have a Bowman's layer. Millions of humans who have had photorefractive keratectomy over the past thirty plus years have had Bowman's layer removed by excimer laser ablation over their central cornea without apparent sequelae. A prior study showed that Bowman's layer does not contribute significantly to mechanical stability within the cornea. Bowman's layer does not have a barrier function, as many cytokines and growth factors, as well as other molecules, such as EBM component perlecan, pass bidirectionally through Bowman's layer in normal corneal functions, and during the response to epithelial scrape injury. We hypothesized that Bowman's layer represents a visible indicator of ongoing cytokine and growth factor-mediated interactions that occur between corneal epithelial cells (and corneal endothelial cells) and stromal keratocytes that maintain the normal corneal tissue organization via negative chemotactic and apoptotic effects of modulators produced by the epithelium on stromal keratocytes. Interleukin-1 alpha, produced constitutively by corneal epithelial cells and endothelial cells, is thought to be one of these cytokines. Bowman's layer is destroyed in corneas with advanced Fuchs' dystrophy or pseudophakic bullous keratopathy when the epithelium becomes edematous and dysfunctional, and fibrovascular tissue commonly develops beneath and/or within the epithelium in these corneas. Bowman's-like layers have been noted to develop surrounding epithelial plugs within the stromal incisions years after radial keratotomy. Although there are species-related differences in corneal wound healing, and even between strains within a species, these differences are not related to the presence or absence of Bowman's layer.
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Affiliation(s)
- Steven E Wilson
- The Cole Eye Institute, I-32, Cleveland Clinic, 9500 Euclid Ave, Cleveland, OH 44195, USA
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6
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Tavakkoli F, Eleiwa TK, Elhusseiny AM, Damala M, Rai AK, Cheraqpour K, Ansari MH, Doroudian M, H Keshel S, Soleimani M, Djalilian AR, Sangwan VS, Singh V. Corneal stem cells niche and homeostasis impacts in regenerative medicine; concise review. Eur J Ophthalmol 2023:11206721221150065. [PMID: 36604831 DOI: 10.1177/11206721221150065] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
The limbal stem cells niche (LSCN) is an optimal microenvironment that provides the limbal epithelial stem cells (LESCs) and strictly regulates their proliferation and differentiation. Disturbing the LSCN homeostasis can lead to limbal stem cell dysfunction (LSCD) and subsequent ocular surface aberrations, such as corneal stromal inflammation, persistent epithelial defects, corneal neovascularisation, lymphangiogenesis, corneal opacification, and conjunctivalization. As ocular surface disorders are considered the second main cause of blindness, it becomes crucial to explore different therapeutic strategies for restoring the functions of the LSCN. A major limitation of corneal transplantation is the current shortage of donor tissue to meet the requirements worldwide. In this context, it becomes mandatory to find an alternative regenerative medicine, such as using cultured limbal epithelial/stromal stem cells, inducing the production of corneal like cells by using other sources of stem cells, and using tissue engineering methods aiming to produce the three-dimensional (3D) printed cornea. Limbal epithelial stem cells have been considered the magic potion for eye treatment. Epithelial and stromal stem cells in the limbal niche hold the responsibility of replenishing the corneal epithelium. These stem cells are being used for transplantation to maintain corneal epithelial integrity and ultimately sustain optimal vision. In this review, we summarised the characteristics of the LSCN and their current and future roles in restoring corneal homeostasis in eyes with LSCD.
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Affiliation(s)
- Fatemeh Tavakkoli
- Department of Community Health, College of Health Technology, Cihan University, Erbil, Iraq.,SSR Stem Cell Biology Laboratory, Brien Holden Eye Research Centre, Centre for Ocular Regeneration, Hyderabad Eye Research Foundation, L.V. Prasad Eye Institute, Hyderabad, India.,Centre for Genetic Disorders, Banaras Hindu University, Varanasi, India
| | - Taher K Eleiwa
- Department of Ophthalmology, Benha University, Benha, Egypt
| | - Abdelrahman M Elhusseiny
- Department of Ophthalmology, Harvey and Bernice Jones Eye Institute, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Mukesh Damala
- SSR Stem Cell Biology Laboratory, Brien Holden Eye Research Centre, Centre for Ocular Regeneration, Hyderabad Eye Research Foundation, L.V. Prasad Eye Institute, Hyderabad, India.,School of Life Sciences, University of Hyderabad, Hyderabad, India
| | - Amit K Rai
- Centre for Genetic Disorders, Banaras Hindu University, Varanasi, India
| | - Kasra Cheraqpour
- Translational Eye Research Center, Farabi Eye Hospital, 48439Tehran University of Medical Sciences, Tehran, Iran
| | - Mohammad H Ansari
- Ophthalmic Research Center, Department of Ophthalmology, Labbafinejad Medical Center, 556492Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Doroudian
- Department of Cell and Molecular Biology, Faculty of Biological Sciences, 145440Kharazmi University, Tehran, Iran
| | - Saeed H Keshel
- Department of Tissue Engineering and Applied Cell Sciences, 556492Shahid Beheshti University of Medical Sciences, Tehran, Iran
| | - Mohammad Soleimani
- Department of Ophthalmology, 159636Illinois Eye and Ear Infirmary, University of Illinois at Chicago, Chicago, IL, USA
| | - Ali R Djalilian
- Department of Ophthalmology, 159636Illinois Eye and Ear Infirmary, University of Illinois at Chicago, Chicago, IL, USA
| | | | - Vivek Singh
- SSR Stem Cell Biology Laboratory, Brien Holden Eye Research Centre, Centre for Ocular Regeneration, Hyderabad Eye Research Foundation, L.V. Prasad Eye Institute, Hyderabad, India
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7
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Menon A, Vijayavenkataraman S. Novel vision restoration techniques: 3D bioprinting, gene and stem cell therapy, optogenetics, and the bionic eye. Artif Organs 2022; 46:1463-1474. [PMID: 35373344 DOI: 10.1111/aor.14241] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2022] [Revised: 03/18/2022] [Accepted: 03/18/2022] [Indexed: 11/29/2022]
Abstract
BACKGROUND Vision restoration has been one of the most sought-after goals of ophthalmology because of its inception. Despite these problems being tackled from numerous different perspectives, a concrete solution has not yet been achieved. An optimal solution will have significant implications on the patient's quality of life, socioeconomic status, and mental health. METHODS This article will explore new and innovative approaches with one common aim-to restore functional vision for the visually impaired. These novel techniques include 3D bioprinting, stem cell therapy, gene therapy, implantable devices, and optogenetics. RESULTS While the techniques mentioned above show significant promise, they are currently in various stages of development ranging from clinical trials to commercial availability. Restoration of minimal vision in specific cases has already been achieved by the different methods but optimization of different parameters like biocompatibility, spatiotemporal resolution, and minimizing the costs are essential for widespread use. CONCLUSION The developments over the past decade have resulted in multiple milestones in each of the techniques with many solutions getting approved by the FDA. This article will compare these novel techniques and highlight the major advantages and drawbacks of each of them.
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Affiliation(s)
- Abhay Menon
- The Vijay Lab, Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates
| | - Sanjairaj Vijayavenkataraman
- The Vijay Lab, Division of Engineering, New York University Abu Dhabi, Abu Dhabi, United Arab Emirates.,Department of Mechanical and Aerospace Engineering, Tandon School of Engineering, New York University, Brooklyn, New York, USA
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8
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Frutos-Rincón L, Gómez-Sánchez JA, Íñigo-Portugués A, Acosta MC, Gallar J. An Experimental Model of Neuro-Immune Interactions in the Eye: Corneal Sensory Nerves and Resident Dendritic Cells. Int J Mol Sci 2022; 23:ijms23062997. [PMID: 35328417 PMCID: PMC8951464 DOI: 10.3390/ijms23062997] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2022] [Revised: 02/28/2022] [Accepted: 03/04/2022] [Indexed: 12/04/2022] Open
Abstract
The cornea is an avascular connective tissue that is crucial, not only as the primary barrier of the eye but also as a proper transparent refractive structure. Corneal transparency is necessary for vision and is the result of several factors, including its highly organized structure, the physiology of its few cellular components, the lack of myelinated nerves (although it is extremely innervated), the tightly controlled hydration state, and the absence of blood and lymphatic vessels in healthy conditions, among others. The avascular, immune-privileged tissue of the cornea is an ideal model to study the interactions between its well-characterized and dense sensory nerves (easily accessible for both focal electrophysiological recording and morphological studies) and the low number of resident immune cell types, distinguished from those cells migrating from blood vessels. This paper presents an overview of the corneal structure and innervation, the resident dendritic cell (DC) subpopulations present in the cornea, their distribution in relation to corneal nerves, and their role in ocular inflammatory diseases. A mouse model in which sensory axons are constitutively labeled with tdTomato and DCs with green fluorescent protein (GFP) allows further analysis of the neuro-immune crosstalk under inflammatory and steady-state conditions of the eye.
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Affiliation(s)
- Laura Frutos-Rincón
- Instituto de Neurociencias, Universidad Miguel Hernández—Consejo Superior de Investigaciones Científicas, 03550 San Juan de Alicante, Spain; (L.F.-R.); (A.Í.-P.); (M.C.A.); (J.G.)
- The European University of Brain and Technology-NeurotechEU, 03550 San Juan de Alicante, Spain
| | - José Antonio Gómez-Sánchez
- Instituto de Neurociencias, Universidad Miguel Hernández—Consejo Superior de Investigaciones Científicas, 03550 San Juan de Alicante, Spain; (L.F.-R.); (A.Í.-P.); (M.C.A.); (J.G.)
- Correspondence: ; Tel.: +34-965-91-9594
| | - Almudena Íñigo-Portugués
- Instituto de Neurociencias, Universidad Miguel Hernández—Consejo Superior de Investigaciones Científicas, 03550 San Juan de Alicante, Spain; (L.F.-R.); (A.Í.-P.); (M.C.A.); (J.G.)
| | - M. Carmen Acosta
- Instituto de Neurociencias, Universidad Miguel Hernández—Consejo Superior de Investigaciones Científicas, 03550 San Juan de Alicante, Spain; (L.F.-R.); (A.Í.-P.); (M.C.A.); (J.G.)
- The European University of Brain and Technology-NeurotechEU, 03550 San Juan de Alicante, Spain
| | - Juana Gallar
- Instituto de Neurociencias, Universidad Miguel Hernández—Consejo Superior de Investigaciones Científicas, 03550 San Juan de Alicante, Spain; (L.F.-R.); (A.Í.-P.); (M.C.A.); (J.G.)
- The European University of Brain and Technology-NeurotechEU, 03550 San Juan de Alicante, Spain
- Instituto de Investigación Biomédica y Sanitaria de Alicante, 03010 Alicante, Spain
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Brar S, Ganesh S, Sriganesh SS, Dorennavar L. Long-term Outcomes of Bowman's Membrane Relaxation for Enhancement of Femtosecond Intrastromal Lenticule Implantation Performed for the Management of High Hyperopia. J Refract Surg 2022; 38:134-141. [DOI: 10.3928/1081597x-20211215-01] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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10
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Williams IM, Pineda R, Neerukonda VK, Stagner AM. Mucopolysaccharidosis Type I-Associated Corneal Disease: A Clinicopathologic Study. Am J Ophthalmol 2021; 231:39-47. [PMID: 34048802 DOI: 10.1016/j.ajo.2021.05.014] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2020] [Revised: 05/14/2021] [Accepted: 05/15/2021] [Indexed: 11/17/2022]
Abstract
PURPOSE To report the anterior segment clinical features and histopathologic and histochemical characteristics of explanted corneas from the largest reported cohort of patients with Hurler syndrome and other variants of mucopolysaccharidosis (MPS) I undergoing corneal transplantation. DESIGN Retrospective observational case series. METHODS This institutional study reviewed 15 corneas from 9 patients with MPS I spectrum disease who underwent corneal transplant to treat corneal clouding between May 2011 and October 2020. We reviewed the clinical data, hematoxylin-eosin-stained sections, and histochemical stains, including those for mucopolysaccharides (Alcian blue and/or colloidal iron). The main outcome measures were pathology observed under light microscopy and postsurgical clinical outcomes. RESULTS Nine patients underwent 15 corneal transplants for corneal clouding (14/15 procedures were deep anterior lamellar keratoplasty). All corneas had mucopolysaccharide deposition visible on hematoxylin-eosin-stained sections, which was highlighted in blue with histochemical stains. All corneas also showed alterations in Bowman's layer and the majority also showed epithelial abnormalities. CONCLUSION MPS I shows significant corneal clouding that is successfully treated with deep anterior lamellar keratoplasty. The excised corneas show characteristic epithelial changes, disruption or breaks in Bowman's membrane, and amphophilic collections of stromal granular mucopolysaccharides which are visible on hematoxylin-eosin-stained sections and highlighted by special histochemical stains (Alcian blue and collodial iron). These changes, although subtle, should alert the pathologist to the possibility of an underlying lysosomal storage disorder.
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Affiliation(s)
- Imani M Williams
- From the David G. Cogan Laboratory of Ophthalmic Pathology (I.M.W., V.K.N, A.M.S.)
| | - Roberto Pineda
- and Cornea Service (R.P.), Department of Ophthalmology, Massachusetts Eye and Ear, Harvard Medical School, Boston, Massachusetts, USA
| | - Vamsee K Neerukonda
- From the David G. Cogan Laboratory of Ophthalmic Pathology (I.M.W., V.K.N, A.M.S.)
| | - Anna M Stagner
- From the David G. Cogan Laboratory of Ophthalmic Pathology (I.M.W., V.K.N, A.M.S.).
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11
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Bradley AE, Wancket LM, Rinke M, Gruebbel MM, Saladino BH, Schafer K, Katsuta O, Garcia B, Chanut F, Hughes K, Nelson K, Himmel L, McInnes E, Schucker A, Uchida K. International Harmonization of Nomenclature and Diagnostic Criteria (INHAND): Nonproliferative and Proliferative Lesions of the Rabbit. J Toxicol Pathol 2021; 34:183S-292S. [PMID: 34712007 PMCID: PMC8544166 DOI: 10.1293/tox.34.183s] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The INHAND (International Harmonization of Nomenclature and Diagnostic Criteria for
Lesions Project (www.toxpath.org/inhand.asp) is a joint initiative of the Societies of
Toxicologic Pathology from Europe (ESTP), Great Britain (BSTP), Japan (JSTP) and North
America (STP) to develop an internationally accepted nomenclature for proliferative and
non-proliferative lesions in laboratory animals. The purpose of this publication is to
provide a standardized nomenclature for classifying microscopic lesions observed in most
tissues and organs from the laboratory rabbit used in nonclinical safety studies. Some of
the lesions are illustrated by color photomicrographs. The standardized nomenclature
presented in this document is also available electronically on the internet
(http://www.goreni.org/). Sources of material included histopathology databases from
government, academia, and industrial laboratories throughout the world. Content includes
spontaneous lesions as well as lesions induced by exposure to test materials. Relevant
infectious and parasitic lesions are included as well. A widely accepted and utilized
international harmonization of nomenclature for lesions in laboratory animals will provide
a common language among regulatory and scientific research organizations in different
countries and increase and enrich international exchanges of information among
toxicologists and pathologists.
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Affiliation(s)
- Alys E Bradley
- Charles River Laboratories Edinburgh Ltd, Tranent, Scotland, UK
| | | | | | | | | | | | | | - Begonya Garcia
- Charles River Laboratories Edinburgh Ltd, Tranent, Scotland, UK
| | - Franck Chanut
- Sanofi, 1 Avenue Pierre Brosselette, 91380 Chilly-Mazarin, France
| | | | | | - Lauren Himmel
- Vanderbilt University Medical Center, Nashville, TN, USA
| | | | - Adrienne Schucker
- American Preclinical Services, LLC, 8945 Evergreen Blvd, Minneapolis, MN 55433
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12
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Poudel BK, Robert MC, Simpson FC, Malhotra K, Jacques L, LaBarre P, Griffith M. In situ Tissue Regeneration in the Cornea from Bench to Bedside. Cells Tissues Organs 2021; 211:506-526. [PMID: 34380144 DOI: 10.1159/000514690] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2020] [Accepted: 01/22/2021] [Indexed: 11/19/2022] Open
Abstract
Corneal blindness accounts for 5.1% of visual deficiency and is the fourth leading cause of blindness globally. An additional 1.5-2 million people develop corneal blindness each year, including many children born with or who later develop corneal infections. Over 90% of corneal blind people globally live in low- and middle-income regions (LMIRs), where corneal ulcers are approximately 10-fold higher compared to high-income countries. While corneal transplantation is an effective option for patients in high-income countries, there is a considerable global shortage of corneal graft tissue and limited corneal transplant programs in many LMIRs. In situ tissue regeneration aims to restore diseases or damaged tissues by inducing organ regeneration. This can be achieved in the cornea using biomaterials based on extracellular matrix (ECM) components like collagen, hyaluronic acid, and silk. Solid corneal implants based on recombinant human collagen type III were successfully implanted into patients resulting in regeneration of the corneal epithelium, stroma, and sub-basal nerve plexus. As ECM crosslinking and manufacturing methods improve, the focus of biomaterial development has shifted to injectable, in situ gelling formulations. Collagen, collagen-mimetic, and gelatin-based in situ gelling formulas have shown the ability to repair corneal wounds, surgical incisions, and perforations in in-vivo models. Biomaterial approaches may not be sufficient to treat inflammatory conditions, so other cell-free therapies such as treatment with tolerogenic exosomes and extracellular vesicles may improve treatment outcomes. Overall, many of the technologies described here show promise as future medical devices or combination products with cell or drug-based therapies. In situ tissue regeneration, particularly with liquid formulas, offers the ability to triage and treat corneal injuries and disease with a single regenerative solution, providing alternatives to organ transplantation and improving patient outcomes.
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Affiliation(s)
- Bijay K Poudel
- Département d'Ophtalmologie, Université de Montréal, Montréal, Québec, Canada.,Centre de Recherche, Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada
| | - Marie-Claude Robert
- Département d'Ophtalmologie, Université de Montréal, Montréal, Québec, Canada.,Centre de Recherche, Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada.,Département d'Opthalmologie, Centre hospitalier de l'Université de Montréal, Montréal, Québec, Canada
| | - Fiona C Simpson
- Département d'Ophtalmologie, Université de Montréal, Montréal, Québec, Canada.,Centre de Recherche, Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada.,Département d'Opthalmologie, Centre hospitalier de l'Université de Montréal, Montréal, Québec, Canada.,Institut du Génie Biomédicale, Université de Montréal, Montréal, Québec, Canada
| | - Kamal Malhotra
- Département d'Ophtalmologie, Université de Montréal, Montréal, Québec, Canada.,Centre de Recherche, Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada.,Département d'Opthalmologie, Centre hospitalier de l'Université de Montréal, Montréal, Québec, Canada
| | - Ludovic Jacques
- Département d'Ophtalmologie, Université de Montréal, Montréal, Québec, Canada.,Centre de Recherche, Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada
| | | | - May Griffith
- Département d'Ophtalmologie, Université de Montréal, Montréal, Québec, Canada.,Centre de Recherche, Hôpital Maisonneuve-Rosemont, Montréal, Québec, Canada.,Département d'Opthalmologie, Centre hospitalier de l'Université de Montréal, Montréal, Québec, Canada.,Institut du Génie Biomédicale, Université de Montréal, Montréal, Québec, Canada
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13
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Baratta RO, Schlumpf E, Buono BJD, DeLorey S, Calkins DJ. Corneal collagen as a potential therapeutic target in dry eye disease. Surv Ophthalmol 2021; 67:60-67. [PMID: 33882269 DOI: 10.1016/j.survophthal.2021.04.006] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 04/11/2021] [Accepted: 04/12/2021] [Indexed: 01/15/2023]
Abstract
Dry eye disease (DED) is a major cause of ocular discomfort, inflammation and dysfunction worldwide. Tear film instability in DED both causes and is exacerbated by disruption of the corneal epithelium. This tandem leads to a cycle of inflammation at the corneal surface involving immune cell dysregulation and increased chemokines and cytokines, which activate mitogen-activated protein kinases in the epithelium and elevates matrix metalloproteinases (MMPs). We review evidence suggesting that corneal collagen might be highly susceptible in DED to MMP-induced disruption, digestion, and thinning. We also summarize that collagen is far from inert and contains binding sites that serve as ligands for multiple inflammatory and immune regulators. Fragmented collagen not only challenges these receptor-ligand binding relationships, but also can promote recruitment and motility of pro-inflammatory immune cells. Current physician-directed therapies for DED focus on reducing inflammation, but do not directly ameliorate the underlying corneal damage that could exacerbate surface inflammation. We argue that an important gap in practice is lack of a direct therapeutic reparative for damaged corneal collagen, which is slow to heal, and likely amplifies sight-threatening inflammation. Healing fragmented collagen in the cornea may represent a more effective means to interrupt the "vicious cycle" of inflammation in DED and other conditions that damages, sometimes irreversibly, the ocular surface.
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Affiliation(s)
- Robert O Baratta
- Stuart Therapeutics, Inc., 411 SE Osceola St., Suite 203, Stuart, FL 34994
| | - Eric Schlumpf
- Stuart Therapeutics, Inc., 411 SE Osceola St., Suite 203, Stuart, FL 34994
| | - Brian J Del Buono
- Stuart Therapeutics, Inc., 411 SE Osceola St., Suite 203, Stuart, FL 34994
| | - Shawn DeLorey
- Stuart Therapeutics, Inc., 411 SE Osceola St., Suite 203, Stuart, FL 34994
| | - David J Calkins
- The Vanderbilt Eye Institute and Vanderbilt Vision Research Center, AA7100 MCN, 1161 21st Ave S. Nashville, TN 37232-2279.
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14
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Challenges and strategies for the delivery of biologics to the cornea. J Control Release 2021; 333:560-578. [PMID: 33857565 DOI: 10.1016/j.jconrel.2021.04.008] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2020] [Revised: 04/05/2021] [Accepted: 04/10/2021] [Indexed: 02/07/2023]
Abstract
Biologics, like peptides, proteins and nucleic acids, have proven to be promising drugs for the treatment of numerous diseases. However, besides the off label use of the monoclonal antibody bevacizumab for the treatment of corneal neovascularization, to date no other biologics for corneal diseases have reached the market. Indeed, delivering biologics in the eye remains a challenge, especially at the level of the cornea. While it appears to be a rather accessible tissue for the administration of drugs, the cornea in fact presents several anatomical barriers to delivery. In addition, also intracellular delivery barriers need to be overcome to achieve a promising therapeutic outcome with biologics. This review outlines efforts that have been reported to successfully deliver biologics into the cornea. Biochemical and physical methods for achieving delivery of biologics in the cornea are discussed, with a critical view on their efficacy in overcoming corneal barriers.
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15
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Vellara HR, Patel DV. Biomechanical properties of the keratoconic cornea: a review. Clin Exp Optom 2021; 98:31-8. [DOI: 10.1111/cxo.12211] [Citation(s) in RCA: 91] [Impact Index Per Article: 30.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2014] [Revised: 06/12/2014] [Accepted: 06/21/2014] [Indexed: 11/26/2022] Open
Affiliation(s)
- Hans R Vellara
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
| | - Dipika V Patel
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand,
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16
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López-Cano JJ, González-Cela-Casamayor MA, Andrés-Guerrero V, Herrero-Vanrell R, Molina-Martínez IT. Liposomes as vehicles for topical ophthalmic drug delivery and ocular surface protection. Expert Opin Drug Deliv 2021; 18:819-847. [PMID: 33412914 DOI: 10.1080/17425247.2021.1872542] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Introduction: The development of ophthalmic formulations able to deliver hydrophilic and hydrophobic drugs to the inner structures of the eye and restore the preocular tear film has been a leading topic of discussion over the last few years. In this sense, liposomes represent a suitable strategy to achieve these objectives in ocular drug delivery.Areas covered: Knowledge of the different physiological and anatomical eye structures, and specially the ocular surface are critical to better understanding and comprehending the characteristics required for the development of topical ophthalmic liposomal formulations. In this review, several features of liposomes are discussed such as the main materials used for their fabrication, basic structure and preparation methods, from already established to novel techniques, allowing the control and design of special characteristics. Besides, physicochemical properties, purification processes and strategies to overcome delivery or encapsulation challenges are also presented. Expert opinion: Regarding ocular drug delivery of liposomes, there are some features that can be redesigned. Specific biocompatible and biodegradable materials presenting therapeutic properties, such as lipidic compounds or polymers significantly change the way of tackling ophthalmic diseases. Besides, liposomes entail an effective, safe and versatile strategy for the treatment of diseases in the clinical practice.
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Affiliation(s)
- José Javier López-Cano
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Miriam Ana González-Cela-Casamayor
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Vanessa Andrés-Guerrero
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Rocío Herrero-Vanrell
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
| | - Irene Teresa Molina-Martínez
- Department of Pharmaceutics and Food Technology, Complutense University, Madrid, Spain.,Ocular Pathology National Net (OFTARED) of the Institute of Health Carlos III, Health Research Institute of the San Carlos Clinical Hospital (Idissc), Madrid Spain
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17
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Animal model with structural similarity to human corneal collagen fibrillar arrangement. Anat Sci Int 2021; 96:286-293. [PMID: 33392925 DOI: 10.1007/s12565-020-00590-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2020] [Accepted: 11/24/2020] [Indexed: 12/15/2022]
Abstract
Rabbit and porcine corneas have been used in scientific research due to their structural similarity to the human cornea. Currently, there are no studies that have compared corneal collagen fibrillar diameter, interfibrillar distance and interlamellar distance between human and animal models. Ten pairs of porcine, rabbit, and human corneas were used. These were analysed using light and Transmission Electron microscopy. The collagen fibrillar diameter, interfibrillar distance and interlamellar distance were statistically compared between porcine, rabbit and human corneas. The human, porcine and rabbit; mean collagen fibrillar diameters were: 24.52 ± 2.09 nm; 32.87 ± 0.87 nm; and 33.67 ± 1.97 nm. The mean interfibrillar distances were: 46.10 ± 2.44 nm; 53.33 ± 2.24 nm; and 52.87 ± 2.73 nm, respectively. The collagen fibrillar diameter and interfibrillar distance of porcine and rabbit corneas were significantly different (p < 0.001) to the human corneal values but not form each other. The interlamellar distance of human, porcine and rabbit corneas was: 2190 ± 820 nm; 6460 ± 1180 nm; and 4410 ± 1330 nm, respectively. All the comparisons were statistically different, in porcine versus rabbit at the p < 0.01 level and both porcine and rabbit versus human at the p < 0.001 level. Histologically, all five layers (epithelium, Bowman's layer, stroma, Descemet membrane and endothelium) of the cornea were visible in all the three species. While neither animal model was structurally identical to the human cornea, they are both relatively close to being used as models to study the biomechanical effects of external insults/treatments to be extrapolated to the human cornea.
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18
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Ramirez DA, Kam Y, Wilson CW, Ling JJ. Updates in the Management of Corneal Ectasia. Int Ophthalmol Clin 2021; 61:29-43. [PMID: 33337792 DOI: 10.1097/iio.0000000000000341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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19
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Espana EM, Birk DE. Composition, structure and function of the corneal stroma. Exp Eye Res 2020; 198:108137. [PMID: 32663498 PMCID: PMC7508887 DOI: 10.1016/j.exer.2020.108137] [Citation(s) in RCA: 92] [Impact Index Per Article: 23.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2020] [Revised: 06/29/2020] [Accepted: 06/30/2020] [Indexed: 12/13/2022]
Abstract
No other tissue in the body depends more on the composition and organization of the extracellular matrix (ECM) for normal structure and function than the corneal stroma. The precise arrangement and orientation of collagen fibrils, lamellae and keratocytes that occurs during development and is needed in adults to maintain stromal function is dependent on the regulated interaction of multiple ECM components that contribute to attain the unique properties of the cornea: transparency, shape, mechanical strength, and avascularity. This review summarizes the contribution of different ECM components, their structure, regulation and function in modulating the properties of the corneal stroma. Fibril forming collagens (I, III, V), fibril associated collagens with interrupted triple helices (XII and XIV), network forming collagens (IV, VI and VIII) as well as small leucine-rich proteoglycans (SLRP) expressed in the stroma: decorin, biglycan, lumican, keratocan, and fibromodulin are some of the ECM components reviewed in this manuscript. There are spatial and temporal differences in the expression of these ECM components, as well as interactions among them that contribute to stromal function. Unique regions within the stroma like Bowman's layer and Descemet's layer are discussed. To define the complexity of corneal stroma composition and structure as well as the relationship to function is a daunting task. Our knowledge is expanding, and we expect that this review provides a comprehensive overview of current knowledge, definition of gaps and suggests future research directions.
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Affiliation(s)
- Edgar M Espana
- Department of Molecular Pharmacology and Physiology, USA; Cornea, External Disease and Refractive Surgery, Department of Ophthalmology, University of South Florida, Morsani College of Medicine, Tampa, FL, USA
| | - David E Birk
- Department of Molecular Pharmacology and Physiology, USA.
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20
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Genomic analysis of 21 patients with corneal neuralgia after refractive surgery. Pain Rep 2020; 5:e826. [PMID: 32766464 PMCID: PMC7390595 DOI: 10.1097/pr9.0000000000000826] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 04/30/2020] [Accepted: 05/13/2020] [Indexed: 12/19/2022] Open
Abstract
Background Refractive surgery, specifically laser-assisted in situ keratomileusis and photorefractive keratectomy, are widely applied procedures to treat myopia, hyperopia, and astigmatism. After surgery, a subgroup of cases suffers from persistent and intractable pain of obscure etiology, thought to be neuropathic. We aimed to investigate the contribution of genomic factors in the pathogenesis of these patients with corneal neuralgia. Methods We enrolled 21 cases (6 males and 15 females) from 20 unrelated families, who reported persistent pain (>3 months), after refractive surgery (20 laser-assisted in situ keratomileusis and 1 photorefractive keratectomy patients). Whole-exome sequencing and gene-based association test were performed. Results Whole-exome sequencing demonstrated low-frequency variants (allele frequency < 0.05) in electrogenisome-related ion channels and cornea-expressed collagens, most frequently in SCN10A (5 cases), SCN9A (4 cases), TRPV1 (4 cases), CACNA1H and CACNA2D2 (5 cases each), COL5A1 (6 cases), COL6A3 (5 cases), and COL4A2 (4 cases). Two variants, p.K655R of SCN9A and p.Q85R of TRPV1, were previously characterized as gain-of-function. Gene-based association test assessing "damaging" missense variants against gnomAD exome database (non-Finnish European or global), identified a gene, SLC9A3R1, with statistically significant effect (odds ratio = 17.09 or 17.04; Bonferroni-corrected P-value < 0.05). Conclusion These findings in a small patient cohort did not identify a common gene/variant among most of these cases, as found in other disorders, for example small-fiber neuropathy. Further studies of these candidate genes/variants might enhance understanding of the role of genetic factors in the pathogenesis of corneal neuralgia.
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21
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Wilson SE. Biology of keratorefractive surgery- PRK, PTK, LASIK, SMILE, inlays and other refractive procedures. Exp Eye Res 2020; 198:108136. [PMID: 32653492 DOI: 10.1016/j.exer.2020.108136] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2020] [Revised: 06/29/2020] [Accepted: 06/30/2020] [Indexed: 11/19/2022]
Abstract
The outcomes of refractive surgical procedures to improve uncorrected vision in patients-including photorefractive keratectomy (PRK), laser in-situ keratomileusis (LASIK), Small Incision Lenticule Extraction (SMILE) and corneal inlay procedures-is in large part determined by the corneal wound healing response after surgery. The wound healing response varies depending on the type of surgery, the level of intended correction of refractive error, the post-operative inflammatory response, generation of opacity producing myofibroblasts and likely poorly understood genetic factors. This article details what is known about these specific wound healing responses that include apoptosis of keratocytes and myofibroblasts, mitosis of corneal fibroblasts and myofibroblast precursors, the development of myofibroblasts from keratocyte-derived corneal fibroblasts and bone marrow-derived fibrocytes, deposition of disordered extracellular matrix by corneal fibroblasts and myofibroblasts, healing of the epithelial injury, and regeneration of the epithelial basement membrane. Problems with epithelial and stromal cellular viability and function that are altered by corneal inlays are also discussed. A better understanding of the wound healing response in refractive surgical procedures is likely to lead to better treatments to improve outcomes, limit complications of keratorefractive surgical procedures, and improve the safety and efficiency of refractive surgical procedures.
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Affiliation(s)
- Steven E Wilson
- Cole Eye Institute, I-32, Cleveland Clinic, 9500, Euclid Ave, Cleveland, OH, United States.
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22
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Wilson SE. Bowman's layer in the cornea- structure and function and regeneration. Exp Eye Res 2020; 195:108033. [PMID: 32339517 DOI: 10.1016/j.exer.2020.108033] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2020] [Revised: 03/09/2020] [Accepted: 04/07/2020] [Indexed: 12/13/2022]
Abstract
Bowman's layer lies immediately posterior to the epithelial basement membrane (EBM) and anterior to the stroma proper in humans, chickens, quail, zebra fish, deer, giraffe, antelope, California sea lions, guinea pig and several other species. It is not found in dog, wolf, cat, tiger, lions, rabbit, pigs, cows, goats, or horses. Developmental anomalies of Bowman's layer are rare, but acquired damage to Bowman's layer, or even complete destruction, is frequently seen in advanced bullous keratopathy or Fuchs' endothelial dystrophy. No detrimental effects of removal of Bowman's layer over the central 6-7 mm of central cornea have been noted in millions of patients who've had photorefractive keratectomy (PRK). Recent studies have suggested the randomly-oriented collagen fibrils that make up Bowman's layer do not have a significant barrier function in modulating the passage of moderate- to large-sized proteins. It is hypothesized that Bowman's layer develops in the corneas of those species that have one because of cytokine-mediated interactions occurring between corneal epithelial cells and underlying keratocytes, including negative chemotactic and apoptotic effects on the keratocytes by low levels of cytokines such as interleukin-1α that are gradually released as epithelial cells die and slough during their normal development. A "Bowman's like layer" can generate around stromal epithelial plugs after radial keratotomy, and possibly beneath the central corneal epithelial basement membrane many years after PRK.
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Affiliation(s)
- Steven E Wilson
- Cole Eye Institute, I-32, Cleveland Clinic, 9500, Euclid Ave, Cleveland, OH, United States.
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23
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Eleiwa TK, Elsawy A, Syed ZA, Roongpoovapatr V, Sayed AM, Yoo SH, Abou Shousha M. In-vivo Three-dimensional Characteristics of Bowman's Layer and Endothelium/Descemet's Complex Using Corneal Microlayer Tomography in Healthy Subjects. Curr Eye Res 2020; 45:659-667. [PMID: 32064952 DOI: 10.1080/02713683.2019.1691238] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
Purpose: To characterize the three-dimensional (3D) thickness profile and age-related changes of Bowman's layer (BL), and endothelium/Descemet's membrane (En/DM) complex among healthy individuals using Corneal Microlayer Tomography (CML-T), and to describe its repeatability and accuracy.Methods: Sixty-six eyes of 41 healthy volunteers; 27 eyes (< 40 years old), and 39 eyes (>40 years old) were imaged using HD-OCT. Automatic and manual segmentation of the corneal layers was performed, and 3D thickness maps were generated, using custom-built CML-T software. A regional analysis of mean thickness parameters between the 2 age groups was performed. A regression analysis was used to assess the correlation between age, and thickness maps. Intraclass Correlation Coefficients (ICC), Coefficients of Variation (COV), and Bland-Altman plots were used to assess the reliability of the repeated measurements in 198 locations.Results: CML-T successfully mapped the BL and En/DM in all included eyes. Thickness maps showed a significant increase in corneal thickness (CT), BL thickness (BMT), and En/DM complex thickness (DMT) toward the periphery with a mean difference 28 µm (p < .001), 1.1 µm (p < .001), and 1.4 µm (p < .001), respectively. There was a strong correlation between age and central DMT (r = 0.61; p < .001), while there was no correlation between age and both CT, and BMT. ICC values ranged from 0.9 (BMT) to 0.997 (DMT), and from 0.808 (BMT) to 0.979 (CT) for intraoperator repeatability of manual measurements, and the accuracy of auto matic measurements, respectively. COV values were lower than 7.5% in all cases.Conclusion: CML-T is a novel tool that can generate 3D-thickness maps of both BL and En/DM. CT, BMT, and DMT increase toward the periphery in healthy corneas. DMT increases with aging, while BMT does not. We also report excellent repeatability, accuracy and good agreement between automatic and manual measurements.
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Affiliation(s)
- Taher K Eleiwa
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA.,Department of Ophthalmology, Faculty of Medicine, Benha University, Benha, Egypt
| | - Amr Elsawy
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA.,Electrical and Computer Engineering, University of Miami, Miami, FL, USA
| | - Zeba A Syed
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA.,Wills Eye Hospital, Thomas Jefferson University, Philadelphia, PA, USA
| | | | - Ahmed M Sayed
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA.,Biomedical Engineering Department, Helwan University, Helwan, Egypt
| | - Sonia H Yoo
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA
| | - Mohamed Abou Shousha
- Bascom Palmer Eye Institute, University of Miami Miller School of Medicine, Miami, FL, USA.,Electrical and Computer Engineering, University of Miami, Miami, FL, USA.,Biomedical Engineering, University of Miami, Miami, FL, USA
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24
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Clinical Trials of Limbal Stem Cell Deficiency Treated with Oral Mucosal Epithelial Cells. Int J Mol Sci 2020; 21:ijms21020411. [PMID: 31936462 PMCID: PMC7014181 DOI: 10.3390/ijms21020411] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2019] [Revised: 01/04/2020] [Accepted: 01/07/2020] [Indexed: 12/11/2022] Open
Abstract
The corneal surface is an essential organ necessary for vision, and its clarity must be maintained. The corneal epithelium is renewed by limbal stem cells, located in the limbus and in palisades of Vogt. Palisades of Vogt maintain the clearness of the corneal epithelium by blocking the growth of conjunctival epithelium and the invasion of blood vessels over the cornea. The limbal region can be damaged by chemical burns, physical damage (e.g., by contact lenses), congenital disease, chronic inflammation, or limbal surgeries. The degree of limbus damage is associated with the degree of limbal stem cells deficiency (partial or total). For a long time, the only treatment to restore vision was grafting part of the healthy cornea from the other eye of the patient or by transplanting a cornea from cadavers. The regenerative medicine and stem cell therapies have been applied to restore normal vision using different methodologies. The source of stem cells varies from embryonic stem cells, mesenchymal stem cells, to induced pluripotent stem cells. This review focuses on the use of oral mucosa epithelial stem cells and their use in engineering cell sheets to treat limbal stem cell deficient patients.
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25
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Abstract
PURPOSE OF REVIEW Bowman layer transplantation is a novel technique that may stabilize progressive ectatic corneal changes in eyes with keratoconus, which are too steep or too thin for ultraviolet corneal crosslinking or intracorneal ring segments. In this way, patients can maintain stable vision with contact lenses, and avoid or postpone more invasive corneal transplants, such as penetrating keratoplasty or deep anterior lamellar keratoplasty. This review aims to summarize the currently available literature on Bowman layer transplantation. RECENT FINDINGS Bowman layer transplantation seems to be a promising, minimally invasive procedure for managing advanced keratoconus with a reported 5-year success rate of 84%. The procedure allows patients to maintain acceptable visual acuity with glasses or contact lens correction. Although graft preparation and surgical technique can be challenging, adaptation of technologies, such as femtosecond laser and intraoperative anterior segment optical coherence tomography, may help overcome these barriers to enable Bowman layer transplantation to become a more widely adopted procedure. SUMMARY Bowman layer transplantation may offer an alternative, less invasive treatment option for eyes with advanced, progressive keratoconus.
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26
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Volatier TLA, Figueiredo FC, Connon CJ. Keratoconus at a Molecular Level: A Review. Anat Rec (Hoboken) 2019; 303:1680-1688. [DOI: 10.1002/ar.24090] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2018] [Revised: 10/19/2018] [Accepted: 11/02/2018] [Indexed: 12/12/2022]
Affiliation(s)
| | | | - Che J. Connon
- Institute of Genetic MedicineNewcastle University Newcastle upon Tyne UK
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27
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Differential epithelial and stromal protein profiles in cone and non-cone regions of keratoconus corneas. Sci Rep 2019; 9:2965. [PMID: 30814630 PMCID: PMC6393548 DOI: 10.1038/s41598-019-39182-6] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 01/18/2019] [Indexed: 12/14/2022] Open
Abstract
Keratoconus (KC) is an ectatic corneal disease characterized by progressive thinning and irregular astigmatism, and a leading indication for corneal transplantation. KC-associated changes have been demonstrated for the entire cornea, but the pathological thinning and mechanical weakening is usually localized. We performed quantitative proteomics using Sequential Windowed Acquisition of All Theoretical Fragment Ion Mass Spectrometry (SWATH-MS) to analyze epithelial and stromal changes between the topographically-abnormal cone and topographically-normal non-cone regions of advanced KC corneas, compared to age-matched normal corneas. Expression of 20 epithelial and 14 stromal proteins was significantly altered (≥2 or ≤0.5-fold) between cone and non-cone in all 4 KC samples. Ingenuity pathway analysis illustrated developmental and metabolic disorders for the altered epithelial proteome with mitochondrion as the significant gene ontology (GO) term. The differential stromal proteome was related to cellular assembly, tissue organization and connective tissue disorders with endoplasmic reticulum protein folding as the significant GO term. Validation of selected protein expression was performed on archived KC, non-KC and normal corneal specimens by immunohistochemistry. This is the first time to show that KC-associated proteome changes were not limited to the topographically-thinner and mechanically-weakened cone but also non-cone region with normal topography, indicating a peripheral involvement in KC development.
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28
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29
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Demarcation Line in the Human Cornea After Surface Ablation Observed by Optical Coherence Tomography and Confocal Microscopy. Eye Contact Lens 2018; 44 Suppl 2:S19-S23. [PMID: 29210827 DOI: 10.1097/icl.0000000000000459] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE To investigate the long-term changes in anterior corneal structure after surface ablation. METHODS In this retrospective study, patients who received surface ablation including laser-assisted subepithelial keratomileusis (LASEK) and epipolis laser in situ keratomileusis at the Department of Ophthalmology of Fudan University Eye and Ear, Nose and Throat (EENT) Hospital (Shanghai, People's Republic of China) were telephoned. Patients were asked to follow-up at the refractive center. Changes in the anterior cornea (from the epithelium to the anterior stroma) were examined by optical coherence tomography (OCT) and in vivo confocal microscopy. RESULTS Thirty-four eyes of 18 patients (10 years or more after operation), 16 eyes of 8 patients (4 years after operation), 12 eyes of 6 patients (1 year after operation), 8 eyes of 4 patients (6 months after operation), and 12 eyes of 6 patients (1 month after operation) were included. Under OCT, a smooth, continuous, and highly reflective demarcation line between the epithelial layer and the stroma was noted in all eyes that received surgeries more than 1 year previously. For eyes at 6 months after operation, the complete formation of this demarcation line was detected in 12.5% (1/8) of eyes and a partial formation of this demarcation line was observed in 87.5% (7/8) of eyes. A partial formation of this demarcation line was observed in 100% (12/12) of eyes in patients at 1 month after surgery. CONCLUSIONS A demarcation line in the human cornea can be detected after corneal surface ablation. It was completely formed around postoperative 6 to 12 months. The functions and components of this structure merit investigation.
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Abhari S, Eisenback M, Kaplan HJ, Walters E, Prather RS, Scott PA. Anatomic Studies of the Miniature Swine Cornea. Anat Rec (Hoboken) 2018; 301:1955-1967. [PMID: 30288945 DOI: 10.1002/ar.23890] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 04/11/2018] [Accepted: 05/01/2018] [Indexed: 01/01/2023]
Abstract
The domestic swine eye resembles the human eye both anatomically and physiologically. Xenotransplantation of the swine cornea to humans in need of full keratoplasty shows promise as a potential therapeutic strategy to restore vision in individuals with advanced corneal disease, especially those residing in developing nations. That said, we characterized the morphology of corneas from miniature swine, which are smaller in size, easier to handle, and more cost-effective compared to domestic swine. Eyes (N = 15) were harvested from miniature swine from different age groups: 1 month (N = 3), 2 month (N = 3), 4 month (N = 3), 8 month (N = 3), as well as 24 month old adult domestic swine (N = 3). They were immediately submerged in fixative and processed for histological examination at the light and transmission electron microscopic level. Gross anatomic measurements of the cornea were significantly less (P value ≤ 0.05) in miniature swine versus domestic swine. Corneal strata exhibited morphological characteristics similar to the domestic swine cornea. Adult miniature swine corneas show similar overall corneal thickness at 8 months of age versus domestic swine. Miniature swine exhibit similar corneal morphology with the domestic pig and humans, with the exception of Bowman's layer, which is absent in pigs. Therefore, miniature pigs may be a useful resource of corneal tissue for humans in need of full keratoplasty, as well as serve as a large eye model for ophthalmology residents to develop surgical skills and for development and testing of ocular therapeutic strategies that translate to humans. Anat Rec, 301:1955-1967, 2018. © 2018 Wiley Periodicals, Inc.
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Affiliation(s)
- Sarag Abhari
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky
| | - Michael Eisenback
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky
| | - Henry J Kaplan
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky.,Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky.,Department of Microbiology and Immunology, University of Louisville, Louisville, Kentucky
| | - Eric Walters
- Division of Animal Science, University of Missouri-Columbia, Columbia, Missouri.,National Swine Resource and Research Center, University of Missouri-Columbia, Columbia, Missouri
| | - Randall S Prather
- Division of Animal Science, University of Missouri-Columbia, Columbia, Missouri.,National Swine Resource and Research Center, University of Missouri-Columbia, Columbia, Missouri
| | - Patrick A Scott
- Department of Ophthalmology and Visual Sciences, University of Louisville, Louisville, Kentucky.,Department of Anatomical Sciences and Neurobiology, University of Louisville, Louisville, Kentucky
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Chen Z, You J, Liu X, Cooper S, Hodge C, Sutton G, Crook JM, Wallace GG. Biomaterials for corneal bioengineering. ACTA ACUST UNITED AC 2018; 13:032002. [PMID: 29021411 DOI: 10.1088/1748-605x/aa92d2] [Citation(s) in RCA: 71] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Corneal transplantation is an important surgical treatment for many common corneal diseases. However, a worldwide shortage of tissue from suitable corneal donors has meant that many people are not able to receive sight-restoring operations. In addition, rejection is a major cause of corneal transplant failure. Bioengineering corneal tissue has recently gained widespread attention. In order to facilitate corneal regeneration, a range of materials is currently being investigated. The ideal substrate requires sufficient tectonic durability, biocompatibility with cultured cellular elements, transparency, and perhaps biodegradability and clinical compliance. This review considers the anatomy and function of the native cornea as a precursor to evaluating a variety of biomaterials for corneal regeneration including key characteristics for optimal material form and function. The integration of appropriate cells with the most appropriate biomaterials is also discussed. Taken together, the information provided offers insight into the requirements for fabricating synthetic and semisynthetic corneas for in vitro modeling of tissue development and disease, pharmaceutical screening, and in vivo application for regenerative medicine.
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Affiliation(s)
- Zhi Chen
- ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, AIIM Facility, Innovation Campus, University of Wollongong, Squires Way, Fairy Meadow, New South Wales 2519, Australia
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Sharma B, Dubey A, Prakash G, Vajpayee RB. Bowman's layer transplantation: evidence to date. Clin Ophthalmol 2018; 12:433-437. [PMID: 29551887 PMCID: PMC5842778 DOI: 10.2147/opth.s141127] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Surgical management of keratoconus (KC) has undergone a paradigm shift in the last two decades and component corneal transplantation technique of deep anterior lamellar keratoplasty has established itself as a modality of choice for management of advanced cases of KC. Every now and then, new minimalist modalities are being innovated for the management of KC. On the same lines, a new technique, Bowman's layer transplantation, for surgical management of moderate to advanced KC has been reported in recent years. The procedure has shown to be beneficial in reducing ectasia in advanced KC with minimal intraoperative and postoperative complications. In this review, we intend to describe available information and literature with reference to this new surgical technique - Bowman's layer transplantation.
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Affiliation(s)
- Bhavana Sharma
- Department of Ophthalmology, All India Institute of Medical Sciences, Bhopal, India
| | - Aditi Dubey
- Department of Ophthalmology, Gandhi Medical College, Bhopal, India
| | - Gaurav Prakash
- Cornea and Refractive Surgery Services, NMC Eye Care, New Medical Center Specialty Hospital, Abu Dhabi, United Arab Emirates
| | - Rasik B Vajpayee
- Vision Eye Institute, Melbourne, VIC, Australia.,Royal Victorian Eye and Ear Hospital, Melbourne, VIC, Australia.,North West Academic Centre, University of Melbourne, Melbourne, VIC, Australia
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RNA-Seq analysis and comparison of corneal epithelium in keratoconus and myopia patients. Sci Rep 2018; 8:389. [PMID: 29321650 PMCID: PMC5762683 DOI: 10.1038/s41598-017-18480-x] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Accepted: 12/12/2017] [Indexed: 12/12/2022] Open
Abstract
Keratoconus is a common degenerative corneal disease that can lead to significant visual morbidity, and both genetic and environmental factors have been implicated in its pathogenesis. We compared the transcriptome of keratoconus and control epithelium using RNA-Seq. Epithelial tissues were obtained prior to surgery from keratoconus and myopia control patients, undergoing collagen cross-linking and photorefractive keratectomy, respectively. We identified major differences in keratoconus linked to cell-cell communication, cell signalling and cellular metabolism. The genes associated with the Hedgehog, Wnt and Notch1 signaling pathways were down-regulated in keratoconus. We also identified plasmolipin and Notch1 as being significantly reduced in keratoconus for both gene and protein expression (p < 0.05). Plasmolipin is a novel protein identified in human corneal epithelium, and has been demonstrated to have a key role in epithelial cell differentiation in other tissues. This study shows altered gene and protein expression of these three proteins in keratoconus, and further studies are clearly warranted to confirm the functional role of these proteins in the pathogenesis of keratoconus.
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Puzzolo D, Pisani A, Malta C, Santoro G, Meduri A, Abbate F, Montalbano G, Wylegala E, Rana RA, Bucchieri F, Ieni A, Aragona P, Micali A. Structural, ultrastructural, and morphometric study of the zebrafish ocular surface: a model for human corneal diseases? Curr Eye Res 2017; 43:175-185. [PMID: 29111817 DOI: 10.1080/02713683.2017.1385087] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
PURPOSE A morphological and morphometric study of the adult zebrafish ocular surface was performed to provide a comprehensive description of its parts and to evaluate its similarity to the human. MATERIALS AND METHODS The eyes of adult zebrafish were processed for light, transmission and scanning electron microscopy, and for immunohistochemical stain of corneal nerves; a morphometric analysis was also performed on several morphological parameters. RESULTS The corneal epithelium was formed by five layers of cells. No Bowman's layer could be demonstrated. The stroma consisted of lamellae of different thickness with few keratocytes. The Descemet's membrane was absent as the flat and polygonal endothelial cells directly adhered to the deepest corneal lamella. The immunohistochemical stain of neurofilaments failed to demonstrate corneal nerve fibers. The conjunctival epithelium was stratified, overlying the stroma formed by a subepithelial and a deep layer, this latter connected to the scleral cartilage. In the peripheral cornea and in the conjunctiva, many goblet and rodlet cells were observed. The morphometric analysis showed that the peripheral cornea epithelium was thicker when compared to the other parts of the ocular surface, with smaller superficial cells. Desmosomes and hemidesmosomes in the conjunctiva were significantly fewer in number than the other parts of the ocular surface. The stroma was thinner in the conjunctiva than in the cornea, while corneal lamellae were thicker in the intermediate stroma. CONCLUSIONS The zebrafish ocular surface showed significant differences compared to the human, such as the absence of Bowman's layer, Descemet's membrane and corneal nerve fibers, the reduced stromal thickness, and the presence of rodlet cells. On the basis of these original findings, it is suggested that the use of the zebrafish as a model for studying normal or pathological human corneas should be undertaken with particular caution.
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Affiliation(s)
- Domenico Puzzolo
- a Department of Biomedical Sciences , University of Messina , Messina , Italy
| | - Antonina Pisani
- a Department of Biomedical Sciences , University of Messina , Messina , Italy
| | - Consuelo Malta
- a Department of Biomedical Sciences , University of Messina , Messina , Italy
| | - Giuseppe Santoro
- a Department of Biomedical Sciences , University of Messina , Messina , Italy
| | - Alessandro Meduri
- a Department of Biomedical Sciences , University of Messina , Messina , Italy
| | - Francesco Abbate
- b Department of Veterinary Sciences, Laboratory of Zebrafish Neuromorphology , University of Messina , Messina , Italy
| | - Giuseppe Montalbano
- b Department of Veterinary Sciences, Laboratory of Zebrafish Neuromorphology , University of Messina , Messina , Italy
| | - Edward Wylegala
- c Clinical Department of Ophthalmology, School of Medicine with the Division of Dentistry in Zabrze , Medical University of Silesia , Katowice , Poland
| | - Rosa Alba Rana
- d Department of Medicine and Science of Aging , University of Chieti , Chieti , Italy
| | - Fabio Bucchieri
- e Department of Experimental Medicine, Section of Anatomy , University of Palermo , Palermo , Italy
| | - Antonio Ieni
- f Department of Human Pathology , University of Messina , Messina , Italy
| | - Pasquale Aragona
- g Department of Biomedical Sciences, Regional Referral Center for the Ocular Surface Diseases , University of Messina , Messina , Italy
| | - Antonio Micali
- a Department of Biomedical Sciences , University of Messina , Messina , Italy
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Wilson SE, Marino GK, Torricelli AAM, Medeiros CS. Injury and defective regeneration of the epithelial basement membrane in corneal fibrosis: A paradigm for fibrosis in other organs? Matrix Biol 2017. [PMID: 28625845 DOI: 10.1016/j.matbio.2017.06.003] [Citation(s) in RCA: 65] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Myofibroblast-mediated fibrosis is important in the pathophysiology of diseases in most organs. The cornea, the transparent anterior wall of the eye that functions to focus light on the retina, is commonly affected by fibrosis and provides an optimal model due to its simplicity and accessibility. Severe injuries to the cornea, including infection, surgery, and trauma, may trigger the development of myofibroblasts and fibrosis in the normally transparent connective tissue stroma. Ultrastructural studies have demonstrated that defective epithelial basement membrane (EBM) regeneration after injury underlies the development of myofibroblasts from both bone marrow- and keratocyte-derived precursor cells in the cornea. Defective EBM permits epithelium-derived transforming growth factor beta, platelet-derived growth factor, and likely other modulators, to penetrate the stroma at sustained levels necessary to drive the development of vimentin+ alpha-smooth muscle actin+ desmin+ (V+A+D+) mature myofibroblasts and promote their persistence. Defective versus normal EBM regeneration likely relates to the severity of the stromal injury and a resulting decrease in fibroblasts (keratocytes) and their contribution of EBM components, including laminin alpha-3 and nidogen-2. Corneal fibrosis may resolve over a period of months to years if the inciting injury is eliminated through keratocyte-facilitated regeneration of normal EBM, ensuing apoptosis of myofibroblasts, and reorganization of disordered extracellular matrix by repopulating keratocytes. We hypothesize the corneal model of fibrosis associated with defective BM regeneration and myofibroblast development after epithelial or parenchymal injury may be a paradigm for the development of fibrosis in other organs where chronic injury or defective BM underlies the pathophysiology of disease.
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Affiliation(s)
- Steven E Wilson
- The Cole Eye Institute, The Cleveland Clinic, Cleveland, OH, United States.
| | | | | | - Carla S Medeiros
- The Cole Eye Institute, The Cleveland Clinic, Cleveland, OH, United States
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He M, Wang W, Ding H, Zhong X. Comparison of Two Cap Thickness in Small Incision Lenticule Extraction: 100μm versus 160μm. PLoS One 2016; 11:e0163259. [PMID: 27655417 PMCID: PMC5031463 DOI: 10.1371/journal.pone.0163259] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2016] [Accepted: 09/05/2016] [Indexed: 11/19/2022] Open
Abstract
PURPOSE To compare the changes of biomechanical properties, endothelial cell density (ECD), and posterior corneal elevation (PCE) after femtosecond small incision lenticule extractions (SMILEs) with 100μm versus 160μm cap thicknesses. METHODS A total of 12 rabbits were randomly assigned into two groups of 6 each. SMILE was performed at a depth of either 160μm (160-cap group) or 100μm (100-cap group). Corneal biomechanics, PCE, ECD were evaluated pre-operatively, 1week, 1 month, 2 months, 3 months, and 4 months post-operatively by Pentacam, Corvis ST, in vivo confocal microscopy (IVCM) respectively. The Young's modulus was obtained by strip-extensometry test 4 months after surgery. RESULTS At each time point, the second applanation time (A2T) was similar between the groups with the exception of 4 months after surgery (22.66±0.16 ms in the 160-cap group versus 21.75±0.29 ms in the 100-cap group, p = 0.004). Neither deformation amplitude (DA) nor the first applanationtime (A1T) were significantly different between the two groups. The postoperative posterior surface did not shift forward, the changes of PCE and ECD were not significantly different between the two groups at any observation time. Young's modulus was higher in the 160-cap group than that in the 100-cap group with no statistical significance (P>0.05). Regression analyses showed that the PCE changes and Young's modulus were not affected by cap thickness (CT) or residual stromal bed thickness (RBT) (All P>0.05). CONCLUSIONS The differences of corneal biomechanics, posterior surface elevation, or ECD changes were quite small when using 100μm or 160μm cap thicknesses in SMILE.
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Affiliation(s)
- Miao He
- Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-Sen University, Guangzhou, People’s Republic of China
| | - Wei Wang
- Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-Sen University, Guangzhou, People’s Republic of China
| | - Hui Ding
- Hainan Eye Hospital, Zhongshan Ophthalmic Center, Sun Yat-sen University, Haikou, Hainan Province, China
| | - Xingwu Zhong
- Zhongshan Ophthalmic Center, State Key Laboratory of Ophthalmology, Sun Yat-Sen University, Guangzhou, People’s Republic of China
- Hainan Eye Hospital, Zhongshan Ophthalmic Center, Sun Yat-sen University, Haikou, Hainan Province, China
- * E-mail:
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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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Wang X, Huang Y, Jastaneiah S, Majumdar S, Kang JU, Yiu SC, Stark W, Elisseeff JH. Protective Effects of Soluble Collagen during Ultraviolet-A Crosslinking on Enzyme-Mediated Corneal Ectatic Models. PLoS One 2015; 10:e0136999. [PMID: 26325407 PMCID: PMC4556688 DOI: 10.1371/journal.pone.0136999] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 08/11/2015] [Indexed: 11/19/2022] Open
Abstract
Collagen crosslinking is a relatively new treatment for structural disorders of corneal ectasia, such as keratoconus. However, there is a lack of animal models of keratoconus, which has been an obstacle for carefully analyzing the mechanisms of crosslinking and evaluating new therapies. In this study, we treated rabbit eyes with collagenase and chondroitinase enzymes to generate ex vivo corneal ectatic models that simulate the structural disorder of keratoconus. The models were then used to evaluate the protective effect of soluble collagen in the UVA crosslinking system. After enzyme treatment, the eyes were exposed to riboflavin/UVA crosslinking with and without soluble type I collagen. Corneal morphology, collagen ultrastructure, and thermal stability were evaluated before and after crosslinking. Enzyme treatments resulted in corneal curvature changes, collagen ultrastructural damage, decreased swelling resistance and thermal stability, which are similar to what is observed in keratoconus eyes. UVA crosslinking restored swelling resistance and thermal stability, but ultrastructural damage were found in the crosslinked ectatic corneas. Adding soluble collagen during crosslinking provided ultrastructural protection and further enhanced the swelling resistance. Therefore, UVA crosslinking on the ectatic model mimicked typical clinical treatment for keratoconus, suggesting that this model replicates aspects of human keratoconus and could be used for investigating experimental therapies and treatments prior to translation.
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Affiliation(s)
- Xiaokun Wang
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Yong Huang
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Sabah Jastaneiah
- Ophthalmology, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
| | - Shoumyo Majumdar
- Department of Material Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jin U. Kang
- Department of Electrical and Computer Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Samuel C. Yiu
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Walter Stark
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Jennifer H. Elisseeff
- Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Material Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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Ţălu Ş, Stach S, Sueiras V, Ziebarth NM. Fractal analysis of AFM images of the surface of Bowman's membrane of the human cornea. Ann Biomed Eng 2015; 43:906-16. [PMID: 25266935 DOI: 10.1007/s10439-014-1140-3] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2014] [Accepted: 09/23/2014] [Indexed: 02/07/2023]
Abstract
The objective of this study is to further investigate the ultrastructural details of the surface of Bowman's membrane of the human cornea, using atomic force microscopy (AFM) images. One representative image acquired of Bowman's membrane of a human cornea was investigated. The three-dimensional (3-D) surface of the sample was imaged using AFM in contact mode, while the sample was completely submerged in optisol solution. Height and deflection images were acquired at multiple scan lengths using the MFP-3D AFM system software (Asylum Research, Santa Barbara, CA), based in IGOR Pro (WaveMetrics, Lake Oswego, OR). A novel approach, based on computational algorithms for fractal analysis of surfaces applied for AFM data, was utilized to analyze the surface structure. The surfaces revealed a fractal structure at the nanometer scale. The fractal dimension, D, provided quantitative values that characterize the scale properties of surface geometry. Detailed characterization of the surface topography was obtained using statistical parameters, in accordance with ISO 25178-2: 2012. Results obtained by fractal analysis confirm the relationship between the value of the fractal dimension and the statistical surface roughness parameters. The surface structure of Bowman's membrane of the human cornea is complex. The analyzed AFM images confirm a fractal nature of the surface, which is not taken into account by classical surface statistical parameters. Surface fractal dimension could be useful in ophthalmology to quantify corneal architectural changes associated with different disease states to further our understanding of disease evolution.
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Affiliation(s)
- Ştefan Ţălu
- Discipline of Descriptive Geometry and Engineering Graphics, Department of AET, Faculty of Mechanical Engineering, Technical University of Cluj-Napoca, 103-105 B-dul Muncii St., 400641, Cluj-Napoca, Cluj, Romania,
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Luo J, Yao P, Li M, Xu G, Zhao J, Tian M, Zhou X. Quantitative Analysis of Microdistortions in Bowman’s Layer Using Optical Coherence Tomography After SMILE Among Different Myopic Corrections. J Refract Surg 2015; 31:104-9. [DOI: 10.3928/1081597x-20150122-05] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2014] [Accepted: 12/19/2014] [Indexed: 11/20/2022]
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Torricelli AAM, Wilson SE. Cellular and extracellular matrix modulation of corneal stromal opacity. Exp Eye Res 2014; 129:151-60. [PMID: 25281830 DOI: 10.1016/j.exer.2014.09.013] [Citation(s) in RCA: 84] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2014] [Revised: 08/08/2014] [Accepted: 09/30/2014] [Indexed: 01/23/2023]
Abstract
Stromal transparency is a critical factor contributing to normal function of the visual system. Corneal injury, surgery, disease and infection elicit complex wound healing responses that serve to protect against insults and maintain the integrity of the cornea, and subsequently to restore corneal structure and transparency. However, in some cases these processes result in prolonged loss of corneal transparency and resulting diminished vision. Corneal opacity is mediated by the complex actions of many cytokines, growth factors, and chemokines produced by the epithelial cells, stromal cells, bone marrow-derived cells, lacrimal tissues, and nerves. Myofibroblasts, and the disorganized extracellular matrix produced by these cells, are critical determinants of the level and persistence of stromal opacity after corneal injury. Decreases in corneal crystallins in myofibroblasts and corneal fibroblasts contribute to cellular opacity in the stroma. Regeneration of a fully functional epithelial basement membrane (BM) appears to have a critical role in the maintenance of corneal stromal transparency after mild injuries and recovery of transparency when opacity is generated after severe injuries. The epithelial BM likely has a regulatory function whereby it modulates epithelium-derived growth factors such as transforming growth factor (TGF) β and platelet-derived growth factor (PDGF) that drive the development and persistence of myofibroblasts from precursor cells. The purpose of this article is to review the factors involved in the maintenance of corneal transparency and to highlight the mechanisms involved in the appearance, persistency and regression of corneal opacity after stromal injury.
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Yoon JJ, Ismail S, Sherwin T. Limbal stem cells: Central concepts of corneal epithelial homeostasis. World J Stem Cells 2014; 6:391-403. [PMID: 25258661 PMCID: PMC4172668 DOI: 10.4252/wjsc.v6.i4.391] [Citation(s) in RCA: 73] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 08/20/2014] [Accepted: 09/01/2014] [Indexed: 02/06/2023] Open
Abstract
A strong cohort of evidence exists that supports the localisation of corneal stem cells at the limbus. The distinguishing characteristics of limbal cells as stem cells include slow cycling properties, high proliferative potential when required, clonogenicity, absence of differentiation marker expression coupled with positive expression of progenitor markers, multipotency, centripetal migration, requirement for a distinct niche environment and the ability of transplanted limbal cells to regenerate the entire corneal epithelium. The existence of limbal stem cells supports the prevailing theory of corneal homeostasis, known as the XYZ hypothesis where X represents proliferation and stratification of limbal basal cells, Y centripetal migration of basal cells and Z desquamation of superficial cells. To maintain the mass of cornea, the sum of X and Y must equal Z and very elegant cell tracking experiments provide strong evidence in support of this theory. However, several recent studies have suggested the existence of oligopotent stem cells capable of corneal maintenance outside of the limbus. This review presents a summary of data which led to the current concepts of corneal epithelial homeostasis and discusses areas of controversy surrounding the existence of a secondary stem cell reservoir on the corneal surface
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Alessio G, L'Abbate M, Furino C, Sborgia C, La Tegola MG. Confocal microscopy analysis of corneal changes after photorefractive keratectomy plus cross-linking for keratoconus: 4-year follow-up. Am J Ophthalmol 2014; 158:476-84.e1. [PMID: 24878307 DOI: 10.1016/j.ajo.2014.05.024] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2014] [Revised: 05/19/2014] [Accepted: 05/21/2014] [Indexed: 11/18/2022]
Abstract
PURPOSE To analyze corneal confocal microscopy changes after combined photorefractive keratectomy (PRK) plus the cross linking (CXL) procedure. DESIGN Prospective interventional case series. METHODS At the Department of Basic Medical Sciences, Neuroscience, and Sense Organs of the University of Bari, Bari, Italy, 17 eyes of 17 patients with progressive keratoconus underwent confocal microscopy examination before and after 1, 3, 6, 12, 18, and 48 months following PRK plus the CXL procedure. The main outcome measures were mean superficial epithelial cell density; mean basal epithelial cell density; mean anterior, mid and posterior keratocyte density; qualitative analysis of stromal backscatter; sub-basal and stromal nerve density parameters; and mean endothelial cell density. RESULTS During the 4-year follow-up, the mean superficial epithelial cell density, mean basal epithelial cell density and mean endothelial cell density remained unchanged (P > 0.05). The anterior mid-stromal keratocyte density showed a significant decrease (P < 0.05) as compared with preoperative values, and the posterior stromal keratocyte density showed a significant increase at 1 and 3 months of follow-up. Sub-basal and stromal nerve density parameters were significantly decreased until postoperative month 6 (P < 0.05 at 1, 3, and 6 months) and then tended to increase up to preoperative values by the 18th postoperative month. CONCLUSION Corneal changes after the PRK plus CXL procedures seem to be pronounced and long lasting as far as keratocyte density of the anterior and mid stroma is concerned. Sub-basal nerve densities tend to reach preoperative values 6 months after surgery.
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Affiliation(s)
- Giovanni Alessio
- Clinica Oculistica, Department of Basic Medical Sciences, Neuroscience, and Sense Organs, University of Bari, Bari, Italy
| | - Milena L'Abbate
- Clinica Oculistica, Department of Basic Medical Sciences, Neuroscience, and Sense Organs, University of Bari, Bari, Italy
| | - Claudio Furino
- Clinica Oculistica, Department of Basic Medical Sciences, Neuroscience, and Sense Organs, University of Bari, Bari, Italy
| | - Carlo Sborgia
- Clinica Oculistica, Department of Basic Medical Sciences, Neuroscience, and Sense Organs, University of Bari, Bari, Italy
| | - Maria Gabriella La Tegola
- Clinica Oculistica, Department of Basic Medical Sciences, Neuroscience, and Sense Organs, University of Bari, Bari, Italy.
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Yao P, Zhao J, Li M, Shen Y, Dong Z, Zhou X. Microdistortions in Bowman’s Layer Following Femtosecond Laser Small Incision Lenticule Extraction Observed by Fourier-Domain OCT. J Refract Surg 2013; 29:668-74. [DOI: 10.3928/1081597x-20130806-01] [Citation(s) in RCA: 58] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2012] [Accepted: 05/13/2013] [Indexed: 11/20/2022]
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Aragona P, Rania L, Roszkowska AM, Spinella R, Postorino E, Puzzolo D, Micali A. Effects of amino acids enriched tears substitutes on the cornea of patients with dysfunctional tear syndrome. Acta Ophthalmol 2013; 91:e437-44. [PMID: 23617248 DOI: 10.1111/aos.12134] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
PURPOSE To evaluate the effect of aminoacid enriched artificial tears on the ocular surface of patients with dysfunctional tear syndrome (DTS). METHODS Forty patients were divided into two groups: group 1 treated for 90 days with sodium hyaluronate (SH) 0.15% 1 drop × 5 times/day; group 2 treated for 90 days with SH 0.15% + aminoacids mixture 1 drop × 5 times/day. Symptom score questionnaire, tear break-up time (TBUT), corneal fluorescein stain, Shirmer's I test and confocal microscopy were performed at baseline and after 30 and 90 days. Confocal images underwent morphometric analysis. RESULTS Both treatments improved symptoms after 1 month. Group 2 patients showed at 1 month an improvement of TBUT and corneal stain, maintained throughout the study. Also Shirmer's I test improved after 3 months. In group 1, an improvement of TBUT and corneal stain was observed after 3 months. The morphometric analysis of confocal images demonstrated at month 1 an improvement of nerve tortuosity in group 2; after 3 months both groups showed a significant improvement versus baseline. The epithelium showed, in both groups, a reduction in hyperreflective large cells starting from 1 month; the area of the cells was significantly reduced after 3 months, with a significant higher reduction in group 2. The perineural stromal opacity was significantly increased after 3 months, particularly in group 2. CONCLUSION This is the first study addressing corneal changes after amino acids administration in a DTS population. The treatment with amino acids enriched SH can be considered a useful tool in the treatment of DTS.
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Affiliation(s)
- Pasquale Aragona
- Department of Experimental Medical-Surgical Sciences, Ocular Surface Diseases Unit, University of Messina, Italy.
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Biomaterials-Enabled Regenerative Medicine in Corneal Applications. Regen Med 2013. [DOI: 10.1007/978-94-007-5690-8_22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022] Open
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Jóhannesson G, Hallberg P, Eklund A, Koskela T, Lindén C. Change in intraocular pressure measurement 2 years after myopic laser-assisted subepithelial keratectomy. J Cataract Refract Surg 2012; 38:1637-42. [DOI: 10.1016/j.jcrs.2012.04.033] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2011] [Revised: 04/12/2012] [Accepted: 04/27/2012] [Indexed: 10/28/2022]
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Donahue DA, Avalos J, Kaufman LE, Simion FA, Cerven DR. Ocular irritation reversibility assessment for personal care products using a porcine corneal culture assay. Toxicol In Vitro 2011; 25:708-14. [DOI: 10.1016/j.tiv.2010.12.008] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Revised: 11/09/2010] [Accepted: 12/10/2010] [Indexed: 11/26/2022]
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Rocha-Azevedo BD, Jamerson M, Cabral GA, Marciano-Cabral F. Acanthamoeba culbertsoni: Analysis of amoebic adhesion and invasion on extracellular matrix components collagen I and laminin-1. Exp Parasitol 2010; 126:79-84. [DOI: 10.1016/j.exppara.2009.08.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Revised: 08/12/2009] [Accepted: 08/14/2009] [Indexed: 11/28/2022]
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Knupp C, Pinali C, Lewis PN, Parfitt GJ, Young RD, Meek KM, Quantock AJ. The architecture of the cornea and structural basis of its transparency. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2009; 78:25-49. [PMID: 20663483 DOI: 10.1016/s1876-1623(08)78002-7] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The cornea is the transparent connective tissue window at the front of the eye. In the extracellular matrix of the corneal stroma, hybrid type I/V collagen fibrils are remarkably uniform in diameter at approximately 30 nm and are regularly arranged into a pseudolattice. Fibrils are believed to be kept at defined distances by the influence of proteoglycans. Light entering the cornea is scattered by the collagen fibrils, but their spatial distribution is such that the scattered light interferes destructively in all directions except from the forward direction. In this way, light travels forward through the cornea to reach the retina. In this chapter, we will review the macromolecular components of the corneal stroma, the way they are organized into a stacked lamellar array, and how this organization guarantees corneal transparency.
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Affiliation(s)
- Carlo Knupp
- Structural Biophysics Group, School of Optometry & Vision Sciences, Cardiff University, Cardiff CF24 4LU, UK
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