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Wieghofer P, Engelbert M, Chui TYP, Rosen RB, Sakamoto T, Sebag J. Hyalocyte origin, structure, and imaging. EXPERT REVIEW OF OPHTHALMOLOGY 2022; 17:233-248. [PMID: 36632192 PMCID: PMC9831111 DOI: 10.1080/17469899.2022.2100762] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Introduction Hyalocytes have been recognized as resident tissue macrophages of the vitreous body since the mid-19th century. Despite this, knowledge about their origin, turnover, and dynamics is limited. Areas covered Historically, initial studies on the origin of hyalocytes used light and electron microscopy. Modern investigations across species including rodents and humans will be described. Novel imaging is now available to study human hyalocytes in vivo. The shared ontogeny with retinal microglia and their eventual interdependence as well as differences will be discussed. Expert opinion Owing to a common origin as myeloid cells, hyalocytes and retinal microglia have similarities, but hyalocytes appear to be distinct as resident macrophages of the vitreous body.
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Affiliation(s)
- Peter Wieghofer
- Cellular Neuroanatomy, Institute of Theoretical Medicine, Medical Faculty, University of Augsburg, Universitätsstraße 2, 86159 Augsburg, Germany,Corresponding authors: Peter Wieghofer. , J Sebag.
| | - Michael Engelbert
- Vitreous Retina Macula Consultants of New York, New York, NY 10022, USA.,LuEsther T. Mertz Retinal Research Center, Manhattan Eye, Ear and Throat Hospital, New York, NY 10065, USA.,Department of Ophthalmology, New York University School of Medicine, New York, NY 10016, USA
| | - Toco YP Chui
- Department of Ophthalmology, New York Eye and Ear Infirmary of Mount Sinai, New York, New York; Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Richard B Rosen
- Department of Ophthalmology, New York Eye and Ear Infirmary of Mount Sinai, New York, New York; Department of Ophthalmology, Icahn School of Medicine at Mount Sinai, New York, New York
| | - Taiji Sakamoto
- Department of Ophthalmology, Kagoshima University Graduate School of Medical and Dental Science, Kagoshima, Japan
| | - J Sebag
- Doheny Eye Institute, UCLA, Los Angeles, CA, USA.,Clinical Ophthalmology, Stein Eye Institute, Geffen School of Medicine, UCLA, Los Angeles, CA, USA.,VMR Institute for Vitreous Macula Retina, Huntington Beach, CA, USA.,Corresponding authors: Peter Wieghofer. , J Sebag.
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da Silva RA, Roda VMDP, Matsuda M, Siqueira PV, Lustoza-Costa GJ, Wu DC, Hamassaki DE. Cellular components of the idiopathic epiretinal membrane. Graefes Arch Clin Exp Ophthalmol 2021; 260:1435-1444. [PMID: 34842983 DOI: 10.1007/s00417-021-05492-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2021] [Revised: 10/24/2021] [Accepted: 11/04/2021] [Indexed: 01/19/2023] Open
Abstract
Idiopathic epiretinal membrane (iERM) is a fibrocellular proliferation on the inner surface of the retina, which leads to decreased visual acuity and even central visual loss. As iERM is associated to advanced age and posterior vitreous detachment, a higher prevalence is expected with increasing life expectancy and aging of the global population. Although various cell types of retinal and extra-retinal origin have been described in iERMs (Müller glial cells, astrocytes, hyalocytes, retinal pigment epithelium cells, myofibroblasts, and fibroblasts), myofibroblasts have a central role in collagen production and contractile activity. Thus, myofibroblast differentiation is considered a key event for the iERM formation and progression, and fibroblasts, Müller glial cells, hyalocytes, and retinal pigment epithelium have been identified as myofibroblast precursors. On the other side, the different cell types synthesize growth factors, cytokines, and extracellular matrix, which have a crucial role in ERM pathogenesis. In the present review, the major cellular components and their functions are summarized, and their possible roles in the iERM formation are discussed. By exploring in detail the cellular and molecular aspects of iERM, we seek to contribute for better understanding of this fibrotic disease and the origin of myofibroblasts, which may eventually drive to more targeted therapeutic approaches.
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Affiliation(s)
- Rafael André da Silva
- Department of Cell & Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, 05508-000, Brazil
| | - Vinicius Moraes de Paiva Roda
- Department of Cell & Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, 05508-000, Brazil
| | - Monique Matsuda
- Laboratory of Investigation in Ophthalmology (LIM-33), Division of Ophthalmology, Faculty of Medicine, University of São Paulo, São Paulo, SP, Brazil
| | - Paula Veloso Siqueira
- Department of Cell & Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, 05508-000, Brazil
| | - Gabriela Jesus Lustoza-Costa
- Department of Cell & Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, 05508-000, Brazil
| | - Davi Chen Wu
- Department of Cell & Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, 05508-000, Brazil.,Department of Ophthalmology, Irmandade de Misericórdia da Santa Casa de São Paulo, São Paulo, SP, Brazil
| | - Dânia Emi Hamassaki
- Department of Cell & Developmental Biology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, SP, 05508-000, Brazil.
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Awwad S, Abubakre A, Angkawinitwong U, Khaw PT, Brocchini S. In situ antibody-loaded hydrogel for intravitreal delivery. Eur J Pharm Sci 2019; 137:104993. [DOI: 10.1016/j.ejps.2019.104993] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2019] [Revised: 07/09/2019] [Accepted: 07/10/2019] [Indexed: 10/26/2022]
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Abstract
Hyalocytes of the vitreous body are variety of tissue macrophages that exercise various functions - from ensuring the synthesis of extracellular matrix components and modulating the immune response in the vitreous body to participating in different stages of inflammatory processes. Some aspects of the biology of hyalocytes remain poorly understood and controversial. However, the vitreous cells are starting to be considered a potential point of application in the treatment of diseases of the vitreous body and the retina.
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Affiliation(s)
- A A Suetov
- State Scientific Research Test Institute of Military Medicine, 4 Lesoparkovaya St., Saint Petersburg, Russian Federation, 195043
| | - E V Boiko
- North-Western State Medical University named after I.I. Mechnikov, Department of Ophthalmology, 41 Kirochnaya St., Saint Petersburg, Russian Federation, 191015; S.M. Kirov Military Medical Academy, Department of Ophthalmology, 5 Klinicheskaya St., Saint Petersburg, Russian Federation, 194044; Saint Petersburg branch of S.N. Fyodorov Eye Microsurgery Federal State Institution, 21 Yaroslava Gasheka St., Saint Petersburg, Russian Federation, 192283
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Sano Y, Matsuda K, Okamoto M, Takehana K, Hirayama K, Taniyama H. Characterization of equine hyalocytes: their immunohistochemical properties, morphologies and distribution. J Vet Med Sci 2016; 78:937-42. [PMID: 26888584 PMCID: PMC4937152 DOI: 10.1292/jvms.15-0511] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
In horse, the characterizations of hyalocytes under the steady state are still unclear. Therefore, we
investigated characterizations of hyalocytes in normal equine eyes by their immunohistochemical phenotype,
histomorphology and distribution. Thirty-one eyes from 18 horses, divided into 4 groups (G) by age, were used:
early (G1) and late gestation (G2) fetuses, 1- to 3-year-old (G3) and 8- to 24-year-old (G4) horses. Equine
hyalocytes were histologically classified into 4 types, and they immunohistochemically expressed MHC II and
CD163. Hyalocytes were detected on and/or around ciliary processes and pars plana in G2, G3 and G4, but were
not located on retina and optic papilla. A significant increase in distribution was found between G2 and both
G3 and G4, and the largest distribution was found at ciliary processes in these groups. Equine hyalocytes were
characterized as residential ocular macrophage and MHC II antigen-bearing cell, accompanied by a pleomorphic
appearance and located in the contiguous ciliary body. Our data provided characterizations of hyalocytes in
normal equine eyes and may well contribute to improving the understanding of pathogenesis of equine ocular
disease.
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Affiliation(s)
- Yuto Sano
- Department of Veterinary Pathology, School of Veterinary Medicine, Rakuno Gakuen University, Ebetsu, Hokkaido 069-8501, Japan
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Yu Y, Lau LCM, Lo ACY, Chau Y. Injectable Chemically Crosslinked Hydrogel for the Controlled Release of Bevacizumab in Vitreous: A 6-Month In Vivo Study. Transl Vis Sci Technol 2015; 4:5. [PMID: 25774331 PMCID: PMC4356035 DOI: 10.1167/tvst.4.2.5] [Citation(s) in RCA: 75] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2014] [Accepted: 11/03/2014] [Indexed: 01/27/2023] Open
Abstract
PURPOSE To evaluate the biocompatibility and 6-month in vivo release of bevacizumab from a hyaluronic acid/dextran-based in situ hydrogel after intravitreal injection in rabbit eye. METHODS The in situ hydrogel was formed by the catalyst-free chemical crosslinking between vinylsulfone functionalized hyaluronic acid (HA-VS) and thiolated dextran (Dex-SH) at physiological condition. The pH 7.4 buffered mixture containing HA-VS, Dex-SH, and bevacizumab were injected into the vitreous of rabbit eyes by a 30-G needle. The biocompatibility was evaluated by intraocular pressure measurement, binocular indirect ophthalmoscope (BIO), full-field electroretinogram (ERG), and histology. The concentrations of both total and active bevacizumab in rabbit vitreous were determined by enzyme-linked immunosorbent assay. The concentration of bevacizumab in rabbit vitreous after bolus injection was simulated by one-compartment first order elimination model. RESULTS A transparent gel was seen in the vitreous after injection. BIO images, ERG, and histology showed that the gel does not induce hemorrhage, retinal detachment, inflammation, or other gross pathological changes in rabbit eyes after injection. While the bolus intravitreal injected bevacizumab follows the first order elimination kinetics in rabbit eye, the in situ gel formation was able to prolong the retention of bevacizumab in rabbit eye at therapeutic relevant concentration for at least 6 months. The concentration of bevacizumab 6 months after injection was about 107 times higher than bolus injection. CONCLUSIONS The new in situ hydrogel formulation of bevacizumab was biocompatible and able to prolong the retention of drug in rabbit eyes in vivo at therapeutic relevant concentration for at least 6 months. TRANSLATIONAL RELEVANCE Although proven to be effective, monthly intravitreal injection of bevacizumab or other protein drugs may cause various complications. Extending the residence time of protein therapeutics in the eye can reduce the injection frequency, its associated complications, and treatment cost, which will be beneficial to both the patients and doctors. In this study, we showed that the in situ hydrogel-based controlled release system is a feasible option to tackle this problem.
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Affiliation(s)
- Yu Yu
- Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon Hong Kong, China
| | - Laurence Chi Ming Lau
- Department of Ophthalmology, The University of Hong Kong, Pok Fu Lam, Hong Kong, China
| | - Amy Cheuk-yin Lo
- Department of Ophthalmology, The University of Hong Kong, Pok Fu Lam, Hong Kong, China
| | - Ying Chau
- Division of Biomedical Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon Hong Kong, China
- Department of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, China
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Abstract
PURPOSE To review the present understanding of hyalocytes. METHODS A review of recent studies that investigated the roles of hyalocytes in the pathophysiology of the vitreous cavity. RESULTS Studies on immunocytochemistry and chimeric mice with green fluorescent protein transgenic mice show that hyalocytes belong to the monocyte/macrophage lineage and derive from bone marrow. The effects of hyalocytes on the vitreous cavity environment can be divided into three categories: synthesis of extracellular matrix, regulation of the vitreous cavity immunology, and modulation of inflammation. In noninflamed eyes, vitreous cavity is an immune-privileged site that is maintained by a system called vitreous cavity-associated immune deviation, in which hyalocytes play the role of antigen-presenting cells. However, cultured hyalocytes proliferate in response to inflammatory molecules and secrete vascular endothelial growth factor and urokinase-type plasminogen activator. A collagen gel embedded with hyalocytes contracts over time, which is enhanced by transforming growth factor-β but is inhibited by Rho kinase inhibitor. These results suggest that hyalocytes can be an exacerbating factor in inflamed eyes. Clinically, hyalocytes are frequently found in the surgically removed specimens of epiretinal membrane or proliferative vitreoretinopathy. CONCLUSION Elucidating the properties of hyalocytes is important to understand the biology of vitreous cavity and to develop novel treatments for vitreoretinal diseases.
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Crooke A, Guzmán-Aranguez A, Peral A, Abdurrahman MKA, Pintor J. Nucleotides in ocular secretions: their role in ocular physiology. Pharmacol Ther 2008; 119:55-73. [PMID: 18562011 DOI: 10.1016/j.pharmthera.2008.04.002] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Accepted: 04/28/2008] [Indexed: 12/15/2022]
Abstract
The eye is the sense organ that permits the detection of light owing to the existence of a sophisticated neuronal array, called the retina, which is responsive to photons. The correct functioning of this complex system requires the coordination of several intraocular structures that ultimately permit the perfect focusing of images on the neural retina. Light has to pass through different media: the tear, the cornea, aqueous humour, lens, and vitreous humour before it reaches the retina. Moreover, the composition and structure of some of these media can change due to several physiological mechanisms. Nucleotides are active components of the humours bathing relevant ocular structures. The tear contains nucleotides and dinucleotides that control the process of tearing, wound healing and protects of superficial infections. In the inner eye, the aqueous humour also presents a collection of mono and dinucleotides that affect pupil contraction, aqueous humour production and accommodation. Behind the lens and between this structure and the retina the vitreous humour can modify the physiology of the retinal cells, mostly the ganglion cells. By investigating the actions of nucleotides and dinucleotide present in the ocular humours we will be able not only to understand the functioning of the ocular structures but also to develop new pharmacological therapies for pathologies such as dry eye, glaucoma or retinal detachment.
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Affiliation(s)
- Almudena Crooke
- Departamento de Bioquímica, E.U. Optica, Universidad Complutense de Madrid, 28037 Madrid, Spain
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Nishitsuka K, Kashiwagi Y, Tojo N, Kanno C, Takahashi Y, Yamamoto T, Heldin P, Yamashita H. Hyaluronan production regulation from porcine hyalocyte cell line by cytokines. Exp Eye Res 2007; 85:539-45. [PMID: 17707370 DOI: 10.1016/j.exer.2007.07.006] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2007] [Revised: 06/26/2007] [Accepted: 07/05/2007] [Indexed: 11/22/2022]
Abstract
The objective of this study were to establish a cell line derived from porcine hyalocytes and to investigate the regulation of hyaluronan (HA) synthesis in response to cytokines. After 50 passages of the cells derived from porcine vitreous tissue, a cell line was generated. The immortalized cells showed fibroblastic morphology. The cell doubling time was 56.9h. In the mRNA level, the cells expressed plate-derived growth factor (PDGF) alpha receptor, PDGF beta receptor, transforming growth factor-beta (TGF-beta) type I receptor, TGF-beta type II receptor, CD44, collagen type I, collagen type II, glial fibrillary acidic protein (GFAP), hyaluronan synthase (HAS) 2, HAS 3 and beta-actin. In the protein level, GFAP was expressed in this cell line. S-100 protein and cytokeratin were not detected. Stimulation with TGF-beta1 and/or PDGF-BB induced a marked increase in the expression level of HAS2 mRNA, and induced HA production. TGF-beta1 stimulated HAS2 expression through the signal transduction pathway including Smad 2,3,4. In summary, this report constitutes the first successful immortalization of porcine hyalocyte cells. The production of HA was induced from the generated porcine hyalocyte cell line under the stimulation of TGF-beta1 and/or PDGF-BB, which may be related to the pathogenesis of proliferative membrane formation in proliferative vitreo-retinal diseases.
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Affiliation(s)
- Koichi Nishitsuka
- Department of Ophthalmology and Visual Science, Yamagata University School of Medicine, 2-2-2 Iidanishi, Yamagata 990-9585, Japan.
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Sommer F, Kobuch K, Brandl F, Wild B, Framme C, Weiser B, Tessmar J, Gabel VP, Blunk T, Goepferich A. Ascorbic acid modulates proliferation and extracellular matrix accumulation of hyalocytes. ACTA ACUST UNITED AC 2007; 13:1281-9. [PMID: 17518733 DOI: 10.1089/ten.2006.0274] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Ascorbic acid is known to influence proliferation and functional properties of several cell types and is therefore widely used in tissue engineering. In this study, the effect of ascorbic acid on the proliferation and functional properties of hyalocytes was evaluated. Hyalocytes were cultured with different amounts of ascorbic acid in classical two-dimensional (2-D) cultures and a three-dimensional (3-D) pellet culture system. Ascorbic acid enhanced hyalocyte proliferation dose-dependently at concentrations between 0.1 and 3 microg/mL; proliferation was constant over a wide concentration range up to 150 microg/mL, concentrations of 500 microg/mL showed toxic effects. In 2-D hyalocyte culture, the accumulation of glycosaminoglycans (GAG) and collagens increased in response to ascorbic acid supplementation of 10 or 200 microg/mL. Normalized to the cell number, GAG production was not influenced, whereas collagen production increased. These results could be verified in a pellet-like 3-D culture system. Ascorbic acid also influenced hyalocytes on the mRNA level; the expression of COL11A1 was clearly enhanced by ascorbic acid. To conclude, ascorbic acid modulates proliferation and collagen accumulation of hyalocytes; it also influences mRNA expression of the cells. Taken together with the fact that ascorbic acid is present in high concentrations in the vitreous body, this vitamin seems to be an important factor for in vitro hyalocyte culture.
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Affiliation(s)
- Florian Sommer
- Department of Pharmaceutical Technology, University of Regensburg, Regensburg, Germany
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Sonoda KH, Sakamoto T, Qiao H, Hisatomi T, Oshima T, Tsutsumi-Miyahara C, Exley M, Balk SP, Taniguchi M, Ishibashi T. The analysis of systemic tolerance elicited by antigen inoculation into the vitreous cavity: vitreous cavity-associated immune deviation. Immunology 2005; 116:390-9. [PMID: 16236129 PMCID: PMC1802422 DOI: 10.1111/j.1365-2567.2005.02239.x] [Citation(s) in RCA: 62] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The immune privilege that exists in the eye is maintained by various mechanisms. One of the best studied is a form of systemic tolerance termed anterior chamber-associated immune deviation (ACAID). We have investigated the mechanisms by which ocular inflammation associated with the vitreous cavity (VC) is reduced, by injecting either ovalbumin (OVA) or allogeneic splenocytes into the VCs of mice, and assessed the effect of this on delayed type hypersensitivity (DTH) responses. After antigen inoculation into the VC, antigen-specific DTH responses were significantly impaired and we named this phenomenon 'vitreous cavity-associated immune deviation' (VCAID). VCAID could also be induced by inoculating antigen-pulsed macrophages into the VC. However, VCAID did not develop either in mice with inflamed eyes, whether as a result of experimental autoimmune uveitis or coadministration of interleukin (IL)-6 in the VC, or in knockout mice deficient for natural killer T (NKT) cells. Finally, we found that so-called 'hyalocytes' are the only cells present in the VCs of normal mice, uniformly distributed on the retinal surface. Interestingly, they express F4/80, suggesting that hyalocytes are candidate antigen-presenting cells (APCs) responsible for mediating VCAID. As for the anterior chamber model, systemic tolerance can be induced in the VC in non-inflamed eyes and in the presence of invariant NKT cells.
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Affiliation(s)
- Koh-Hei Sonoda
- Department of Ophthalmology, Graduate School of Medical Science, Kyushu University, Maidashi, Fukuoka, Japan.
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Qiao H, Hisatomi T, Sonoda KH, Kura S, Sassa Y, Kinoshita S, Nakamura T, Sakamoto T, Ishibashi T. The characterisation of hyalocytes: the origin, phenotype, and turnover. Br J Ophthalmol 2005; 89:513-7. [PMID: 15774935 PMCID: PMC1772586 DOI: 10.1136/bjo.2004.050658] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AIM To determine the characterisation of hyalocytes: the origin, phenotype, and turnover in the rodent. METHODS To characterise the ultrastructure and distribution of hyalocytes, transmission and scanning electron microscopy was performed in rat eyes. Immunophenotypical analysis was performed by either anti-ED1 or ED2 antibodies. To examine the origin of the hyalocytes, the chimeric mice were created and were used to transplant the bone marrow (BM) cells from enhanced green fluorescent protein (EGFP) transgenic mice. The turnover of hyalocytes was examined at 0, 4, 6, 7, and 12 months after BM transplantation. RESULTS Hyalocytes were distributed especially in the vitreous cortex and had an irregular shape with a spherical granule. Immunophenotypical studies demonstrated that most of the hyalocytes in rat eyes expressed ED2 but not ED1. In the chimeric mice, the hyalocytes were GFP negative right after BM transplantation. Interestingly, more than 60% of hyalocytes were replaced within 4 months and approximately 90% within 7 months after BM transplantation. CONCLUSIONS The rodent hyalocytes were shown to express tissue macrophage marker, were derived from BM, and totally replaced within 7 months. These data provide the characterisation of hyalocytes in physiological conditions, especially their origin, distribution, and turnover, and may contribute to the better understanding of the pathogenesis of vitreoretinal disease.
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Affiliation(s)
- H Qiao
- Department of Ophthalmology, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan
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Haddad A, Salazar JJ, Laicine EM, Ramírez AI, Ramírez JM, Triviño A. A direct contact between astrocyte and vitreous body is possible in the rabbit eye due to discontinuities in the basement membrane of the retinal inner limiting membrane. Braz J Med Biol Res 2003; 36:207-11. [PMID: 12563522 DOI: 10.1590/s0100-879x2003000200007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Different from most mammalian species, the optic nerve of the rabbit eye is initially formed inside the retina where myelination of the axons of the ganglion cells starts and vascularization occurs. Astrocytes are confined to these regions. The aforementioned nerve fibers known as medullated nerve fibers form two bundles that may be identified with the naked eye. The blood vessels run on the inner surface of these nerve fiber bundles (epivascularization) and, accordingly, the accompanying astrocytes lie mostly facing the vitreous body from which they are separated only by the inner limiting membrane of the retina. The arrangement of the astrocytes around blood vessels leads to the formation of structures known as glial tufts. Fragments (N = 3) or whole pieces (N = 3) of the medullated nerve fiber region of three-month-old male rabbits (Orictolagus cuniculus) were fixed in glutaraldehyde followed by osmium tetroxide, and their thin sections were examined with a transmission electron microscope. Randomly located discontinuities (up to a few micrometers long) of the basement membrane of the inner limiting membrane of the retina were observed in the glial tufts. As a consequence, a direct contact between the astrocyte plasma membrane and vitreous elements was demonstrated, making possible functional interactions such as macromolecular exchanges between this glial cell type and the components of the vitreous body.
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Affiliation(s)
- A Haddad
- Departamento de Biologia Celular e Molecular e Bioagentes Patogênicos, Faculdade de Medicina de Ribeirão Preto, Universidade de São Paulo, Ribeirão Preto, SP, Brasil.
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Ogawa K. Scanning electron microscopic study of hyalocytes in the guinea pig eye. ARCHIVES OF HISTOLOGY AND CYTOLOGY 2002; 65:263-8. [PMID: 12389665 DOI: 10.1679/aohc.65.263] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ultrastructure and distribution of hyalocytes were examined in guinea pig eyes by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Hyalocytes were distributed randomly on the vitreous surface of the retinal inner limiting membrane, where they were elongated in shape with a spherical perikaryon and a few stout processes. On the epithelial surface of the ciliary body, however, the cells were stellate with some short processes. The cells of both regions included typical dense hyalocyte granules in the cytoplasm. The surface morphology of hyalocytes indicates that the cells are wandering macrophages. The abundance of free cells in the ciliary body epithelium suggests that the area is a site for the emigration of hyalocytes or their precursors from the ciliary stroma. The homogeneous population of hyalocytes in the posterior part of the eyeball may be useful for experimental studies of the cell in vivo or their isolation for study in vitro.
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Affiliation(s)
- Koichi Ogawa
- Department of Anatomy, Fukuoka University School of Medicine, Japan.
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