ENHANCED EXPRESSION OF THE DEVELOPMENTALLY REGULATED EXTRACELLULAR-MATRIX MOLECULE TENASCIN FOLLOWING ADULT BRAIN INJURY

Tenascin is an extracellular matrix molecule synthesized and released by young astrocytes during embryonic and early postnatal development o f the nervous system, and it is concentrated in boundaries around emer ging functional neuronal units. In the adult nervous system, tenascin can be detected only in very low levels. Distinct spatial and temporal distributions of tenascin during developmental events suggest a role in the guidance and/or segregation of neurons and their processes with in incipient functional patterns. We show here, using in situ hybridiz ation and immunocytochemistry, that stab wounds of the adult mouse cer ebellar and cerebral cortices result in an enhanced expression of tena scin in a discrete region around the lesion site that is associated wi th a subset of glial fibrillary acidic protein-positive astrocytes. Te nascin up-regulation in the lesioned adult brain may be directly invol ved in failed regeneration or indirectly involved through its interact ions with other glycoconjugates that either inhibit or facilitate neur ite growth.