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Spatial and temporal distribution of laminins in permanent focal ischemic brain damage of the adult rat

Authors

  • Antti Väänänen,

    1. The Brain Laboratory, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
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  • Juha Risteli,

    1. Department of Clinical Chemistry, University of Oulu, Oulu, Finland
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  • Päivi Liesi

    Corresponding author
    1. The Brain Laboratory, Department of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland
    • The Brain Laboratory, Department of Biological and Environmental Sciences, University of Helsinki, Biocenter 3, P.O. Box 65 (Viikinkaari 1), 00014 University of Helsinki, Finland
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Abstract

Laminins are extracellular matrix glycoproteins with multiple functions in the central nervous system, including maintenance of the blood–brain barrier. Because ischemic brain damage results in rapid degradation of extracellular matrix, we used immunocytochemistry on rat central nervous system after permanent focal ischemia to identify laminins involved in pathophysiology of stroke. At 24 hr after stroke, laminin-1 is transiently expressed by neurons inside the ischemic core, but from 2–3 days to 28 days it is expressed only in basement membrane structures. During the first 24 hr, α1, α5, β1, and γ1 laminins are transiently expressed in neurons within the ischemic core as an acute reaction of the brain to ischemia. Rapid induction of γ1 laminin but no other laminin in reactive astrocytes surrounding the ischemic core is clear at 24 hr, and importantly, expression of γ1 laminin in astrocytes surrounding the ischemic core intensifies during the first days and persists up to 28 days after stroke. At 2–3 days, γ1 laminin immunoreactive barrier of reactive astrocytes is already fully formed, isolating the ischemic area from the healthy brain. Similar to γ1 laminin, its KDI domain localizes in reactive astrocytes isolating the ischemic core. Results indicate that γ1 laminin and its KDI domain are rapidly induced in glial cells after stroke and their expression persists, forming a molecular barrier between the healthy and the damaged brain. Thus, γ1 laminin is involved in pathology of stroke and is likely to serve a protective function, considering its potent neuroprotective role after spinal cord injury and in neurodegenerative disorders. © 2008 Wiley-Liss, Inc.

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