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      In vitro Study of the Effects of Lens Extract on Rat Retinal Neuron Survival and Neurite Outgrowth

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          Abstract

          Background: Optic nerve regeneration has previously been achieved by injuring the lens, which results in the release of lentogenic factors. However, these lentogenic factors are still unknown. Objectives: To investigate what were the lentogenic factors by examining the effects of lens extract and macrophage-conditioned medium (MCM) on the survival and the neurite outgrowth of rat retinal neurons in vitro. Methods: Retinal neurons were cultured in 4 groups: (1) Dulbecco’s modified Eagle’s medium (DMEM), (2) DMEMcontaining lens extract, (3) DMEM containing macrophage-conditioned medium (MCM-D), (4) DMEM and medium from macrophages grown with lens extract (MCM-L). Neurite outgrowth and neuron survival time were observed. The density of retinal neurons with neurites and the longest neurites of the cells were measured on days 1, 3 and 5. Results: Retinal neurons survive for 12–14 days in DMEM containing lens extract. However, the cells only survive for 6 days in DMEM and only 7 days in DMEM containing MCM-L or MCM-D. The present results indicate that lens extract may directly promote survival of rat retinal neurons and neurite outgrowth in vitro. The MCM also promoted cell survival and neurite outgrowth but its effects were weaker than that of the lens extract. We postulate that lens extract exerts its effect by direct neurotrophic effects and/or indirectly by activating macrophagesin vitro.

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          Most cited references 10

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          The macrophage response to central and peripheral nerve injury. A possible role for macrophages in regeneration

          Using mAbs and immunocytochemistry we have examined the response of macrophages (M phi) after crush injury to the sciatic or optic nerve in the mouse and rat. We have established that large numbers of M phi enter peripheral nerves containing degenerating axons; the M phi are localized to the portion containing damaged axons, and they phagocytose myelin. The period of recruitment of the M phi in the peripheral nerve is before and during the period of maximal proliferation of the Schwann cells. In contrast, the degenerating optic nerve attracts few M phi, and the removal of myelin is much slower. These results show the clearly different responses of M phi to damage in the central and peripheral nervous systems, and suggest that M phi may be an important component of subsequent repair as well as myelin degradation.
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            Lens-injury-stimulated axonal regeneration throughout the optic pathway of adult rats.

            Axonal regrowth and restoration of visual function were studied in adult rats. The optic nerve was completely cut behind the eye. The proximal and distal nerve stumps were realigned and the meninges sutured back together. During the same surgical procedure, the lens was lesioned in order to induce secondary cellular cascades, which are known to strongly support the survival of retinal ganglion cells (RGCs) and to promote axonal regeneration. The anatomical and topographic restoration of the visual pathway was assessed neuroanatomically with the aid of anterograde and retrograde tracing using fluorescent dyes. It appeared that the axons formed growth cones at the junction of the suture soon after injury, before glial cells and extracellular matrix proteins were able to cause local scar formation. Growth cones first entered the distal optic nerve stump 3 days after injury, grew through it to reach the optic chiasm approximately 3 weeks after the lesion was made, and terminated within the retinoreceptive layers of the superior colliculus 5 weeks after lesioning. Quantification of the retrogradely labeled cell bodies within the regenerating retina revealed that up to 30% of the RGCs, which includes all major cell types, were capable of regenerating their axons along the entire visual pathway. To assess whether topography was restored, double-labeling experiments were performed, revealing only crude topographic restoration during the initial stages of regeneration. However, visual-evoked potentials could be recorded, indicating that synaptic transmission in higher visual areas was relatively intact. The data show, in principle, that cut axons can regenerate over long distances within the white matter of a central nerve like the adult optic nerve, spanning over 11 mm to the chiasm and between 12 and 15 mm to the thalamus and midbrain. The findings suggest, for the first time, that lentogenic stimulation of RGCs is sufficient to induce the formation of growth cones that can override inhibitors at the site of injury, grow through the white matter of the optic nerve, pass through the optic chiasm, and make synaptic connections within the brain. (c)2001 Elsevier Science.
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              Microtubule-associated proteins: their potential role in determining neuronal morphology.

               I A Matus (1987)
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                Author and article information

                Journal
                ORE
                Ophthalmic Res
                10.1159/issn.0030-3747
                Ophthalmic Research
                S. Karger AG
                0030-3747
                1423-0259
                2009
                July 2009
                28 May 2009
                : 42
                : 1
                : 29-35
                Affiliations
                aDepartment of Ophthalmology, Southwest Hospital, Third Military Medical University, Chongqing, and bDepartment of Ophthalmology, Affiliated Hospital of Medical College of Chinese People’s Armed Police Force, Tianjin, cThe Hospital of the Chinese People’s Armed Police Forces No. 8650, Jingzhong City, PR China; dDepartment of Clinical Ophthalmology, Save Sight Institute, University of Sydney, Sydney,N.S.W., Australia
                Article
                219682 Ophthalmic Res 2009;42:29–35
                10.1159/000219682
                19478538
                © 2009 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 7, References: 21, Pages: 7
                Categories
                Original Paper

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