Journal of Neuroscience, Vol 15, 8096-8108, Copyright © 1995 by Society for Neuroscience
A distinct subset of tenascin/CS-6-PG-rich astrocytes restricts neuronal growth in vitro
S Meiners, EM Powell and HM Geller
Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, Piscataway 08854, USA.
Astrocytes provide an optimal surface for attachment, migration, and growth
of CNS neurons. Nonetheless, not all astrocytes are alike: our previous
work demonstrated a heterogeneity in the ability of cultured astrocyte
monolayers to support neuronal growth. Areas displaying a fibrous, uneven
surface ("rocky" astrocytes) were shown to be restrictive substrates,
whereas surrounding, flat areas were permissive substrates. However,
whether these cell types are in fact different cannot be addressed using
mixed cultures. Therefore, in the current study we used morphological
criteria to isolate the two subpopulations from mixed astrocyte cultures
established from the cerebral cortex of neonatal rats. Following isolation,
the purified populations only produced progeny with the same phenotype as
the parent cells. We then measured production of several extracellular
matrix molecules putatively involved in neuronal guidance during
development and quantitatively assessed neuronal behavior on the purified
populations. Immunocytochemistry and immunoblotting showed that rocky
astrocytes were enriched in tenascin and chondroitin-6- sulfate-containing
proteoglycans, but not in laminin or fibronectin. In addition, these
astrocytes, as well as their isolated matrix, were a less permissive
substrate for neuronal growth than flat astrocytes/matrix. Neurite
outgrowth was significantly increased on rocky astrocytes following
treatment with chondroitinase ABC or AC, but not heparitinase or
hyaluronidase. These data support a critical role for matrix-bound
chondroitin-6-sulfate-containing proteoglycans. We hypothesize that rocky
astrocytes represent a subtype of cells which form barriers to neuronal
growth during cortical development.