Age‐dependent accumulation of lipofuscin in perivascular and subretinal microglia in experimental mice

Fundus autofluorescence (AF) imaging by confocal scanning laser ophthalmoscopy has been widely used by ophthalmologists in the diagnosis/monitoring of various retinal disorders. It is believed that fundus AF is derived from lipofuscin in retinal pigment epithelial (RPE) cells; however, direct clinicopathological correlation has not been possible in humans. We examined fundus AF by confocal scanning laser ophthalmoscopy and confocal microscopy in normal C57BL/6 mice of different ages. Increasingly strong AF signals were observed with age in the neuroretina and subretinal/RPE layer by confocal scanning laser ophthalmoscopy. Unlike fundus AF detected in normal human subjects, mouse fundus AF appeared as discrete foci distributed throughout the retina. Most of the AF signals in the neuroretina were distributed around retinal vessels. Confocal microscopy of retinal and choroid/RPE flat mounts demonstrated that most of the AF signals were derived from Iba‐1+ perivascular and subretinal microglia. An age‐dependent accumulation of Iba‐1+ microglia at the subretinal space was observed. Lipofuscin granules were detected in large numbers in subretinal microglia by electron microscopy. The number of AF+ microglia and the amount of AF granules/cell increased with age. AF granules/lipofuscin were also observed in RPE cells in mice older than 12 months, but the number of AF+ RPE cells was very low (1.48 mm−2 and 5.02 mm−2 for 12 and 24 months, respectively) compared to the number of AF+ microglial cells (20.63 mm−2 and 76.36 mm−2 for 6 and 24 months, respectively). The fluorescence emission fingerprints of AF granules in subretinal microglia were the same as those in RPE cells. Our observation suggests that perivascular and subretinal microglia are the main cells producing lipofuscin in normal aged mouse retina and are responsible for in vivo fundus AF. Microglia may play an important role in retinal aging and age‐related retinal diseases.

[1]  J. Forrester,et al.  Turnover of resident retinal microglia in the normal adult mouse , 2007, Glia.

[2]  D. Riga,et al.  Brain Lipopigment Accumulation in Normal and Pathological Aging , 2006, Annals of the New York Academy of Sciences.

[3]  C. Futter.  The molecular regulation of organelle transport in mammalian retinal pigment epithelial cells. , 2006, Pigment cell research.

[4]  S. Aspengren,et al.  Studies of pigment transfer between Xenopus laevis melanophores and fibroblasts in vitro and in vivo. , 2006, Pigment cell research.

[5]  M. Tso,et al.  Activation of microglia and chemokines in light-induced retinal degeneration. , 2005, Molecular vision.

[6]  Giovanni Staurenghi,et al.  Classification of fundus autofluorescence patterns in early age-related macular disease. , 2005, Investigative ophthalmology & visual science.

[7]  C. Zhang,et al.  Identification of sequential events and factors associated with microglial activation, migration, and cytotoxicity in retinal degeneration in rd mice. , 2005, Investigative ophthalmology & visual science.

[8]  J. Liversidge,et al.  Leukocyte diapedesis in vivo induces transient loss of tight junction protein at the blood-retina barrier. , 2005, Investigative ophthalmology & visual science.

[9]  M. Boulton,et al.  RPE lipofuscin and its role in retinal pathobiology. , 2005, Experimental eye research.

[10]  J. Woulfe,et al.  Lipofuscin and aging: a matter of toxic waste. , 2005, Science of aging knowledge environment : SAGE KE.

[11]  A. Bird,et al.  Fundus autofluorescence in patients with leber congenital amaurosis. , 2004, Investigative ophthalmology & visual science.

[12]  A. Bird,et al.  Fundus autofluorescence in Stargardt macular dystrophy-fundus flavimaculatus. , 2004, American journal of ophthalmology.

[13]  G. Wolf.  Lipofuscin and macular degeneration. , 2004, Nutrition reviews.

[14]  A. Dick,et al.  Generation of activated sialoadhesin-positive microglia during retinal degeneration. , 2003, Investigative ophthalmology & visual science.

[15]  A. Milam,et al.  Activated microglia in human retinitis pigmentosa, late-onset retinal degeneration, and age-related macular degeneration. , 2003, Experimental eye research.

[16]  G S Rubin,et al.  Fundus autofluorescence imaging compared with different confocal scanning laser ophthalmoscopes , 2002, The British journal of ophthalmology.

[17]  J. Forrester,et al.  Leukocyte trafficking in experimental autoimmune uveitis: breakdown of blood-retinal barrier and upregulation of cellular adhesion molecules. , 2003, Investigative ophthalmology & visual science.

[18]  U. Brunk,et al.  Lipofuscin: mechanisms of age-related accumulation and influence on cell function. , 2002, Free radical biology & medicine.

[19]  Noemi Lois,et al.  Fundus autofluorescence in patients with age-related macular degeneration and high risk of visual loss. , 2002, American journal of ophthalmology.

[20]  Janet Liversidge,et al.  Improved leukocyte tracking in mouse retinal and choroidal circulation. , 2002, Experimental eye research.

[21]  Aize Kijlstra,et al.  Distribution, markers, and functions of retinal microglia , 2002, Ocular immunology and inflammation.

[22]  J. Streilein,et al.  Light-induced migration of retinal microglia into the subretinal space. , 2001, Investigative ophthalmology & visual science.

[23]  C K Dorey,et al.  Age-related accumulation and spatial distribution of lipofuscin in RPE of normal subjects. , 2001, Investigative ophthalmology & visual science.

[24]  Noemi Lois,et al.  Quantitative evaluation of fundus autofluorescence imaged “in vivo” in eyes with retinal disease , 2000, The British journal of ophthalmology.

[25]  P. McMenamin.  Subretinal macrophages in the developing eye of eutherian mammals and marsupials , 1999, Anatomy and Embryology.

[26]  K. Kunert,et al.  Microglia increase as photoreceptors decrease in the aging avian retina. , 1999, Current eye research.

[27]  J. Forrester,et al.  Cytokine regulation of granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) production by human retinal pigment epithelial cells , 1999, Clinical and experimental immunology.

[28]  Y. Fukuuchi,et al.  Microglia-specific localisation of a novel calcium binding protein, Iba1. , 1998, Brain research. Molecular brain research.

[29]  A. Kijlstra,et al.  Polarized secretion of IL‐6 and IL‐8 by human retinal pigment epithelial cells , 1998, Clinical and experimental immunology.

[30]  J. Forrester,et al.  Cytokine regulation of RANTES production by human retinal pigment epithelial cells. , 1998, Cellular immunology.

[31]  U. Brunk,et al.  Lipofuscin: Mechanisms of formation and increase with age , 1998, APMIS : acta pathologica, microbiologica, et immunologica Scandinavica.

[32]  J. Provis,et al.  Modulation of major histocompatibility complex class II expression in retinas with age-related macular degeneration. , 1997, Investigative ophthalmology & visual science.

[33]  T. Chan‐Ling.  Glial, vascular, and neuronal cytogenesis in whole‐mounted cat retina , 1997, Microscopy research and technique.

[34]  U. Brunk,et al.  Lipofuscin formation in cultured retinal pigment epithelial cells exposed to photoreceptor outer segment material under different oxygen concentrations , 1996, APMIS : acta pathologica, microbiologica, et immunologica Scandinavica.

[35]  U. Brunk,et al.  Formation of lipofuscin in cultured retinal pigment epithelial cells exposed to pre‐oxidized photoreceptor outer segments , 1996, APMIS : acta pathologica, microbiologica, et immunologica Scandinavica.

[36]  A. Dick,et al.  Flow cytometric identification of a minority population of MHC class II positive cells in the normal rat retina distinct from CD45lowCD11b/c+CD4low parenchymal microglia. , 1995, The British journal of ophthalmology.

[37]  F W Fitzke,et al.  Distribution of fundus autofluorescence with a scanning laser ophthalmoscope. , 1995, The British journal of ophthalmology.

[38]  C K Dorey,et al.  In vivo fluorescence of the ocular fundus exhibits retinal pigment epithelium lipofuscin characteristics. , 1995, Investigative ophthalmology & visual science.

[39]  Ian J Constable,et al.  Lipofuscin of the retinal pigment epithelium: A review , 1995, Eye.

[40]  T. Hirobe.  Structure and function of melanocytes: microscopic morphology and cell biology of mouse melanocytes in the epidermis and hair follicle. , 1995, Histology and histopathology.

[41]  P F Sharp,et al.  Digital fundus imaging using a scanning laser ophthalmoscope. , 1993, Physiological measurement.

[42]  J. Robertson,et al.  Retinal pigment epithelial cells produce interleukin-1β and granulocyte-macrophage colony-stimulating factor in response to interleukin-1α , 1993 .

[43]  J. Robertson,et al.  Retinal pigment epithelial cells produce interleukin-1 beta and granulocyte-macrophage colony-stimulating factor in response to interleukin-1 alpha. , 1993, Current eye research.

[44]  A C Bird,et al.  Confocal imaging of the fundus using a scanning laser ophthalmoscope. , 1992, The British journal of ophthalmology.

[45]  R. Strieter,et al.  Interleukin-6 (IL-6) gene expression and secretion by cytokine-stimulated human retinal pigment epithelial cells. , 1992, Experimental eye research.

[46]  B. Rollins,et al.  Monocyte chemotactic protein gene expression by cytokine-treated human retinal pigment epithelial cells. , 1991, Laboratory investigation; a journal of technical methods and pathology.

[47]  P. McMenamin,et al.  Cells resembling intraventricular macrophages are present in the subretinal space of human foetal eyes , 1990, The Anatomical record.

[48]  R. Strieter,et al.  Neutrophil chemotactic factor (IL-8) gene expression by cytokine-treated retinal pigment epithelial cells. , 1990, The American journal of pathology.

[49]  J. Weiter,et al.  Cell loss in the aging retina. Relationship to lipofuscin accumulation and macular degeneration. , 1989, Investigative ophthalmology & visual science.

[50]  Sohal Rs,et al.  Lipofuscin as an indicator of oxidative stress and aging. , 1989 .

[51]  R. S. Sohal,et al.  Lipofuscin as an indicator of oxidative stress and aging. , 1989, Advances in experimental medicine and biology.

[52]  M. Naash,et al.  Effect of light history on retinal antioxidants and light damage susceptibility in the rat. , 1987, Experimental eye research.

[53]  R. E. Anderson,et al.  Evidence for rod outer segment lipid peroxidation following constant illumination of the rat retina. , 1983, Investigative ophthalmology & visual science.

[54]  J. Dowson.  Neuronal Lipofuscin Accumulation in Ageing and Alzheimer Dementia: A Pathogenic Mechanism? , 1982, British Journal of Psychiatry.

[55]  B. Strehler,et al.  GEE MV: Rate and magnitude of age pigment accumulation in the human myocardium. , 1959, Journal of gerontology.