title: Astroglial permissivity for neuritic outgrowth in neuron-astrocyte cocultures depends on regulation of laminin bioavailability.
abstract: The molecular determinants underlying the failure of axons to regenerate in the CNS after injury were studied in an in vitro model of astrogliosis and neuronal coculture. Mechanically lesioned neuron-astrocyte mouse cortical cocultures were treated with antisense glial fibrillary acidic protein (GFAP)-mRNA in order to inhibit the formation of gliofilaments that occurs in response to injury. This inhibition relieves the blockage of neuron migration and neuritic outgrowth observed after lesion, and migrating neurons reappeared, supported by a laminin-labeled extracellular network (permissive conditions). We then questioned the relationship between this permissivity and laminin production. Follow-up studies on the concentration of laminin indicated that, after antisense treatment, the laminin level was increased in the cocultures and was under the control of astrocyte-neuron interactions. The addition of exogenous laminin favored neuronal migration and neurite outgrowth, whereas neutralizing laminin bioavailability with antibodies recognizing the astroglial laminin resulted in an inhibition of both neuronal access to the lesion site and neurite outgrowth, suggesting an active role for laminin in the permissive process. This permissive process could be associated with modulation of extracellular matrix (ECM) molecule degradation by proteinases. Among the latter, matrix metalloproteinases (MMPs) are involved in the breakdown of the ECM component. Our investigation showed a net decrease of the matrix metalloproteinase MMP-2 expression and activity and an increase of its endogenous inhibitor TIMP-2 expression. Both proteins associated with permissivity should be involved in the laminin stabilization and cell-matrix interactions. High levels of laminin and laminin bioavailability, consequent to a reduction in astrogliosis, may be important permissive elements for neuronal migration and neurite outgrowth postlesion.
authors.affiliation: INSERM U-421, Medical Faculty, Creteil, France.
authors.forename: Silvia
authors.initials: S
authors.lastname: Costa
authors.forename: Thierry
authors.initials: T
authors.lastname: Planchenault
authors.forename: Cecile
authors.initials: C
authors.lastname: Charriere-Bertrand
authors.forename: Yann
authors.initials: Y
authors.lastname: Mouchel
authors.forename: Christiane
authors.initials: C
authors.lastname: Fages
authors.forename: Sharon
authors.initials: S
authors.lastname: Juliano
authors.forename: Thierry
authors.initials: T
authors.lastname: Lefrançois
authors.forename: Georgia
authors.initials: G
authors.lastname: Barlovatz-Meimon
authors.forename: Marcienne
authors.initials: M
authors.lastname: Tardy
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D000906:Antibodies / Q000494:pharmacology; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002450:Cell Communication / Q000187:drug effects / Q000502:physiology*; D002540:Cerebral Cortex / Q000166:cytology / Q000293:injuries / Q000378:metabolism; D002921:Cicatrix / Q000378:metabolism / Q000503:physiopathology; D018920:Coculture Techniques; D005109:Extracellular Matrix / Q000187:drug effects / Q000378:metabolism*; D005904:Glial Fibrillary Acidic Protein / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D005911:Gliosis / Q000378:metabolism / Q000503:physiopathology / Q000517:prevention & control*; D007150:Immunohistochemistry; D007797:Laminin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases / Q000235:genetics; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009414:Nerve Growth Factors / Q000378:metabolism / Q000494:pharmacology; D009416:Nerve Regeneration / Q000187:drug effects / Q000502:physiology*; D016501:Neurites / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000037:antagonists & inhibitors / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000235:genetics; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D000906:Antibodies; D005904:Glial Fibrillary Acidic Protein; D007797:Laminin; D008869:Microtubule-Associated Proteins; D009414:Nerve Growth Factors; D012333:RNA, Messenger; C085284:microtubule-associated protein 1B; D019716:Tissue Inhibitor of Metalloproteinase-2; D053504:Matrix Metalloproteinases, Membrane-Associated; D008666:Metalloendopeptidases; D020778:Matrix Metalloproteinase 2