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Bains KK, Young RD, Koudouna E, Lewis PN, Quantock AJ. Cell-Cell and Cell-Matrix Interactions at the Presumptive Stem Cell Niche of the Chick Corneal Limbus. Cells 2023; 12:2334. [PMID: 37830548 PMCID: PMC10571731 DOI: 10.3390/cells12192334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2023] [Revised: 09/16/2023] [Accepted: 09/19/2023] [Indexed: 10/14/2023] Open
Abstract
(1) Background: Owing to its ready availability and ease of acquisition, developing chick corneal tissue has long been used for research purposes. Here, we seek to ascertain the three-dimensional microanatomy and spatiotemporal interrelationships of the cells (epithelial and stromal), extracellular matrix, and vasculature at the corneo-scleral limbus as the site of the corneal stem cell niche of the chicken eye. (2) Methods: The limbus of developing (i.e., embryonic days (E) 16 and 18, just prior to hatch) and mature chicken eyes was imaged using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and the volume electron microscopy technique, serial-block face SEM (SBF-SEM), the latter technique allowing us to generate three-dimensional reconstructions from data sets of up to 1000 serial images; (3) Results: Data revealed that miniature limbal undulations of the embryonic basement membrane, akin to Palisades of Vogt (PoV), matured into distinct invaginations of epithelial cells that extended proximally into a vascularized limbal stroma. Basal limbal epithelial cells, moreover, occasionally exhibited a high nuclear:cytoplasmic ratio, which is a characteristic feature of stem cells. SBF-SEM identified direct cell-cell associations between corneal epithelial and stromal cells at the base of structures akin to limbal crypts (LCs), with cord-like projections of extracellular matrix extending from the basal epithelial lamina into the subjacent stroma, where they made direct contact with stomal cells in the immature limbus. (4) Conclusion: Similarities with human tissue suggest that the corneal limbus of the mature chicken eye is likely the site of a corneal stem cell niche. The ability to study embryonic corneas pre-hatch, where we see characteristic niche-like features emerge, thus provides an opportunity to chart the development of the limbal stem cell niche of the cornea.
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Affiliation(s)
| | | | | | | | - Andrew J. Quantock
- Structural Biophysics Group, School of Optometry and Vision Sciences, Cardiff University, Maindy Road, Cardiff CF10 3AT, UK; (K.K.B.); (R.D.Y.); (E.K.); (P.N.L.)
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Sanap SN, Bisen AC, Agrawal S, Kedar A, Bhatta RS. Ophthalmic nano-bioconjugates: critical challenges and technological advances. Ther Deliv 2023; 14:419-441. [PMID: 37535389 DOI: 10.4155/tde-2023-0031] [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] [Indexed: 08/04/2023] Open
Abstract
Ophthalmic disease can cause permanent loss of vision and blindness. Easy-to-administer topical and systemic treatments are preferred for treating sight-threatening disorders. Typical ocular anatomy makes topical and systemic ophthalmic drug delivery challenging. Various novel nano-drug delivery approaches are developed to attain the desired bioavailability in the eye by increasing residence time and improved permeability across the cornea. The review focuses on novel methods that are biocompatible, safe and highly therapeutic. Novelty in nanocarrier design and modification can overcome their drawbacks and make them potential drug carriers for eye disorders in both the anterior and posterior eye segments. This review briefly discussed technologies, patented developments, and clinical trial data to support nanocarriers' use in ocular drug delivery.
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Affiliation(s)
- Sachin Nashik Sanap
- Pharmaceutics & Pharmacokinetics Division, CSIR-Central Drug Research Institute, Lucknow, 226031, India
- Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Amol Chhatrapati Bisen
- Pharmaceutics & Pharmacokinetics Division, CSIR-Central Drug Research Institute, Lucknow, 226031, India
- Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Sristi Agrawal
- Pharmaceutics & Pharmacokinetics Division, CSIR-Central Drug Research Institute, Lucknow, 226031, India
- Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, 201002, India
| | - Ashwini Kedar
- Pharmaceutics & Pharmacokinetics Division, CSIR-Central Drug Research Institute, Lucknow, 226031, India
| | - Rabi Sankar Bhatta
- Pharmaceutics & Pharmacokinetics Division, CSIR-Central Drug Research Institute, Lucknow, 226031, India
- Academy of Scientific & Innovative Research (AcSIR), Ghaziabad, 201002, India
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Sanap SN, Kedar A, Bisen AC, Agrawal S, Bhatta RS. A recent update on therapeutic potential of vesicular system against fungal keratitis. J Drug Deliv Sci Technol 2022. [DOI: 10.1016/j.jddst.2022.103721] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Comparison of Subjective and Objective Methods of Corneoscleral Limbus Identification from Anterior Segment Optical Coherence Tomography Images. Optom Vis Sci 2021; 98:127-136. [PMID: 33534377 DOI: 10.1097/opx.0000000000001637] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
SIGNIFICANCE This study evaluates the reliability and validity of an automatic method of the external and internal limbal points identification from anterior segment optical coherence tomography (OCT) images in comparison with manual delineation. PURPOSE The purpose of this work was to evaluate the repeatability and precision of a previously proposed automatic method of external and internal limbal points identification and to compare them with the manual delineation by experienced clinicians in terms of limbus diameter. METHODS Optical coherence tomography tomograms obtained for 12 healthy volunteers without a history of eye diseases were analyzed. Fifteen OCT tomograms were captured for each patient. For all the images, the external and internal limbal points were determined using both the automatic and manual methods. The external and internal limbus diameters were used as the comparative parameter between the methods under consideration. The statistical analysis included mean, standard deviation, the Passing-Bablok regression, and the Pearson correlation coefficient. RESULTS A strong linear dependence between the automatic and manual methods was identified. While compared with the subjective estimates from clinicians, the automatic technique overestimated the external limbus diameter (bias equals 0.21 mm for optometrist and 0.23 mm for ophthalmologist) and slightly underestimated the internal limbus diameter (bias equals 0.13 mm for optometrist and 0.04 mm for ophthalmologist). The automatic method showed significantly better repeatability than the manual method in the case of external limbal points identification and comparably high repeatability for internal limbal points recognition. CONCLUSIONS Because of high precision and excellent repeatability, the automatic method of limbal points identification may be successfully used for estimation of the dynamic changes in the geometry of the anterior segment of the eye, where the large number of captured OCT images needs to be processed automatically with high precision.
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Guo P, Miao Y, Jing Y, Akella S, Wang F, Park CY, Zhang C, Chuck RS. Changes in Collagen Structure and Permeability of Rat and Human Sclera After Crosslinking. Transl Vis Sci Technol 2020; 9:45. [PMID: 32934895 PMCID: PMC7463178 DOI: 10.1167/tvst.9.9.45] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2019] [Accepted: 07/11/2020] [Indexed: 11/25/2022] Open
Abstract
Purpose To use second harmonic generation imaging and fluorescence recovery after photobleaching to demonstrate alterations in scleral collagen structure and permeability after crosslinking in rat and human eyes. Methods Excised rat and human scleras were imaged ex vivo with an inverted two-photon excitation fluorescence microscope before and after photochemical crosslinking using riboflavin and 405-nm laser light. Fluorescence recovery after photobleaching was applied to measure the diffusion of fluorescein isothiocyanate–dextran across the sclera. Results Crosslinking caused scleral collagen fibers to become wavier and more densely packed, with surface collagen being more affected than deeper collagen fibers. Crosslinked sclera showed significantly decreased permeability in the irradiation zone and also extended as far as 250 µm outside the irradiation zone. Conclusions Photochemical crosslinking induced changes in scleral structure and permeability that extended to tissue even outside the irradiation zone. Translational Relevance Ultrastructural changes associated with the emerging clinical technique of photochemical scleral crosslinking have not been well characterized. We demonstrate not only changes in scleral collagen by second harmonic generation imaging but also the associated functional changes in tissue permeability by fluorescence recovery after photobleaching. We report the novel finding of reduced permeability extending well beyond the direct irradiation zone. This has implications for control in the clinical setting.
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Affiliation(s)
- Peng Guo
- Department of Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY, USA.,Analytical Imaging Facility, Albert Einstein College of Medicine, Bronx, NY, USA.,Gruss-Lipper Biophotonics Center, Albert Einstein College of Medicine, Bronx, NY, USA
| | - Yuan Miao
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA.,Aier School of Ophthalmology, Central South University, China
| | - Yang Jing
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Sruti Akella
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Fang Wang
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Choul Yong Park
- Department of Ophthalmology, Dongguk University Ilsan Hospital, Goyang, South Korea
| | - Cheng Zhang
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
| | - Roy S Chuck
- Department of Ophthalmology and Visual Sciences, Albert Einstein College of Medicine, Montefiore Medical Center, Bronx, NY, USA
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Two-Photon Microscopy of the Mouse Peripheral Cornea Ex Vivo. Cornea 2016; 35 Suppl 1:S31-S37. [PMID: 27631351 DOI: 10.1097/ico.0000000000001006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
PURPOSE To investigate the 3-dimensional (3D) cell and extracellular matrix (ECM) structure of mouse peripheral corneas in normal and corneal neovascularization tissues using 2-photon microscopy (TPM) based on both intrinsic and extrinsic moxifloxacin contrasts. METHODS Peripheral corneas in freshly enucleated mouse eyes were imaged by TPM based on both intrinsic and extrinsic contrasts. Intrinsic autofluorescence and second harmonic generation were used to image cells and ECM collagen, respectively. Moxifloxacin ophthalmic solution was applied to image cells. The peripheral cornea, limbus, and sclera were imaged in 3D. In addition to normal mice, mouse models of suture-induced corneal neovascularization were imaged to visualize changes in the microstructure. RESULTS Complex 3D cell and ECM structures in the cornea, limbus, and sclera were visualized by TPM. TPM images based on intrinsic contrasts visualized both cell and ECM structures, and TPM images based on moxifloxacin visualized cell structures with enhanced contrast. On the limbus side of the mouse peripheral cornea, TPM images visualized the vasculature in the limbus, the trabecular meshwork/Schlemm canal, iris, and ciliary body. On the scleral side, TPM images visualized cell and ECM structures in the sclera and multiple cell layers below the sclera. TPM images of the peripheral cornea in the corneal neovascularization condition visualized the extension of vasculature from the limbus to the cornea. CONCLUSIONS TPM imaging based on both intrinsic and external moxifloxacin contrasts visualized detailed 3D cell and ECM microstructures in the mouse peripheral cornea. TPM based on moxifloxacin might be advantageous for studying cell structures by enhancing image contrast.
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Gonzalez JM, Ko MK, Masedunskas A, Hong YK, Weigert R, Tan JCH. Toward in vivo two-photon analysis of mouse aqueous outflow structure and function. Exp Eye Res 2016; 158:161-170. [PMID: 27179411 DOI: 10.1016/j.exer.2016.05.009] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Revised: 05/05/2016] [Accepted: 05/09/2016] [Indexed: 12/29/2022]
Abstract
The promise of revolutionary insights into intraocular pressure (IOP) and aqueous humor outflow homeostasis, IOP pathogenesis, and novel therapy offered by engineered mouse models has been hindered by a lack of appropriate tools for studying the aqueous drainage tissues in their original 3-dimensional (3D) environment. Advances in 2-photon excitation fluorescence imaging (TPEF) combined with availability of modalities such as transgenic reporter mice and intravital dyes have placed us on the cusp of unlocking the potential of the mouse model for unearthing insights into aqueous drainage structure and function. Multimodality 2-photon imaging permits high-resolution visualization not only of tissue structural organization but also cells and cellular function. It is possible to dig deeper into understanding the cellular basis of aqueous outflow regulation as the technique integrates analysis of tissue structure, cell biology and physiology in a way that could also lead to fresh insights into human glaucoma. We outline recent novel applications of two-photon imaging to analyze the mouse conventional drainage system in vivo or in whole tissues: (1) collagen second harmonic generation (SHG) identifies the locations of episcleral vessels, intrascleral plexuses, collector channels, and Schlemm's canal in the distal aqueous drainage tract; (2) the prospero homeobox protein 1-green fluorescent protein (GFP) reporter helps locate the inner wall of Schlemm's canal; (3) Calcein AM, siGLO™, the fluorescent reporters m-Tomato and GFP, and coherent anti-Stokes scattering (CARS), are adjuncts to TPEF to identify live cells by their membrane or cytosolic locations; (4) autofluorescence and sulforhodamine-B to identify elastic fibers in the living eye. These tools greatly expand our options for analyzing physiological and pathological processes in the aqueous drainage tissues of live mice as a model of the analogous human system.
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Affiliation(s)
- Jose M Gonzalez
- Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Minhee K Ko
- Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA
| | - Andrius Masedunskas
- Intracellular Membrane Trafficking Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - Young-Kwon Hong
- Department of Surgery, Department of Biochemistry and Molecular Biology, Norris Comprehensive Cancer Center, Keck School of Medicine, University of Southern California, Los Angeles, CA, USA
| | - Roberto Weigert
- Intracellular Membrane Trafficking Section, National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD, USA
| | - James C H Tan
- Doheny Eye Institute and Department of Ophthalmology, David Geffen School of Medicine, University of California, Los Angeles, CA, USA.
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Gonzalez JM, Ammar MJ, Ko MK, Tan JCH. Optimizing two-photon multiple fluorophore imaging of the human trabecular meshwork. Mol Vis 2016; 22:203-12. [PMID: 27122962 PMCID: PMC4835224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2015] [Accepted: 02/29/2016] [Indexed: 11/25/2022] Open
Abstract
PURPOSE Advances in two-photon (2P) deep tissue imaging provide powerful options for simultaneously viewing multiple fluorophores within tissues. We determined imaging parameters for optimally visualizing three fluorophores in the human trabecular meshwork (TM) to simultaneously detect broad-spectrum autofluorescence and multiple fluorophores through a limited number of emission filters. METHODS 2P imaging of viable human postmortem TM was conducted to detect Hoechst 33342-labeled nuclei, Alexa-568-conjugated phalloidin labeling of filamentous actin, and autofluorescence of the structural extracellular matrix (ECM). Emission detection through green (500-550 nm), near-red (565-605 nm), and far-red (590-680 nm) filters following 2P excitation at 750, 800, 850, and 900 nm was analyzed. Region-of-interest (ROI) image analysis provided fluorescence intensity values for each fluorophore. RESULTS Red-channel Alexa 568 fluorescence was of highest intensity with 2P 750 nm and 800 nm excitation. Alexa 568 was imperceptible with 900 nm excitation. With excitation at 750 nm and 800 nm, Hoechst 33,342 intensity swamped autofluorescence in the green channel, and marked bleed-through into red channels was seen. 850 nm excitation yielded balanced Hoechst 33342 and autofluorescence intensities, minimized their bleed-through into the far-red channel, and produced reasonable Alexa 568 intensities in the far-red channel. CONCLUSIONS 2P excitation at 850 nm and long-wavelength emission detection in the far-red channel allowed simultaneous visualization of the specific mix of endogenous and exogenous fluorophores with reasonably balanced intensities while minimizing bleed-through when imaging the human TM.
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Affiliation(s)
- Jose M. Gonzalez
- Doheny Eye Institute; University of California, Los Angeles, Los Angeles, CA
| | - Michael J. Ammar
- Keck School of Medicine, University of Southern California, Los Angeles, CA
| | - MinHee K. Ko
- Doheny Eye Institute; University of California, Los Angeles, Los Angeles, CA
| | - James C. H. Tan
- Doheny Eye Institute; University of California, Los Angeles, Los Angeles, CA,Department of Ophthalmology, University of California, Los Angeles, Los Angeles, CA
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