A distinct subset of Tenascin CS-6-PG-rich astrocytes restricts neuronal growth in vitro

Department of Pharmacology, UMDNJ-Robert Wood Johnson Medical School, Piscataway 08854, USA.
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 01/1996; 15(12):8096-108.
Source: PubMed


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.

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    • "It was demonstrated that its expression was limited to specific astrocyte cell lines or subpopulations during CNS development [66] [67]. Paradoxically, TN-C was considered both as a repulsive substrate for neuronal and astrocytic growth [68] [69] and as a permissive one, by providing axonal guidance cues [66] [67] [70] [71]. Depending on the context, such as the expression of other ECM molecules, TN-C can have the opposite differential effects on neuronal growth. "
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    ABSTRACT: Matricellular proteins are secreted, nonstructural proteins that regulate the extracellular matrix (ECM) and interactions between cells through modulation of growth factor signaling, cell adhesion, migration, and proliferation. Despite being well described in the context of nonneuronal tissues, recent studies have revealed that these molecules may also play instrumental roles in central nervous system (CNS) development and diseases. In this minireview, we discuss the matricellular protein families SPARC (secreted protein acidic and rich in cysteine), Hevin/SC1 (SPARC-like 1), TN-C (Tenascin C), TSP (Thrombospondin), and CCN (CYR61/CTGF/NOV), which are secreted by astrocytes during development. These proteins exhibit a reduced expression in adult CNS but are upregulated in reactive astrocytes following injury or disease, where they are well placed to modulate the repair processes such as tissue remodeling, axon regeneration, glial scar formation, angiogenesis, and rewiring of neural circuitry. Conversely, their reexpression in reactive astrocytes may also lead to detrimental effects and promote the progression of neurodegenerative diseases.
    Full-text · Article · Jan 2014 · Neural Plasticity
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    • "Tenascin-C has been shown to be expressed and secreted by numerous populations of astrocytes (Mahler, et al., 1996; Meiners, et al., 1995). Although astrocytes have been shown to exert negative affects on neurons in vitro and in grafting paradigms, these studies utilized astrocytes in latter developmental stages (Krobert, et al., 1997; Meiners, et al., 1995). Also, it is likely that the mechanical dissociation involved in the present investigation resulted in isomorphic astrogliosis (Liberto, et al., 2004). "
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    ABSTRACT: The poor survival rate (5-20%) of grafted embryonic dopamine (DA) neurons is one of the primary factors preventing cell replacement from becoming a viable treatment for Parkinson's disease. Previous studies have demonstrated that graft volume impacts grafted DA neuron survival, indicating that transplant parameters influence survival rates. However, the effects of mesencephalic cell concentration on grafted DA neuron survival have not been investigated. The current study compares the survival rates of DA neurons in grafts of varying concentrations. Mesencephalic cell suspensions derived from E14 Fisher 344 rat pups were concentrated to 25,000, 50,000, 100,000 and 200,000 cells/microl and transplanted into two 0.5 microl sites in the 6-OHDA-denervated rat striatum. Animals were sacrificed 10 days and 6 weeks post-transplantation for histochemical analysis of striatal grafts. The absolute number of DA neurons per graft increased proportionally to the total number of cells transplanted. However, our results show that the 200,000 cells/microl group exhibited significantly higher survival rates (5.48+/-0.83%) compared to the 25,000 cells/microl (2.81+/-0.39%) and 50,000 cells/microl (3.36+/-0.51%) groups (p=0.02 and 0.03, respectively). Soma size of grafted DA neurons in the 200,000 cells/microl group was significantly larger than that of the 25,000 cells/microl (p<0.0001) and 50,000 cells/microl groups (p=0.004). In conclusion, increasing the concentration of mesencephalic cells prior to transplantation, augments the survival and functionality of grafted DA neurons. These data have the potential to identify optimal transplantation parameters that can be applied to procedures utilizing stem cells, neural progenitors, and primary mesencephalic cells.
    Full-text · Article · Oct 2007 · Journal of Neuroscience Methods
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    • "After incubation for two weeks, fibrous astrocytes and protoplasmic astrocytes, which became tile-shaped with cell contact were observed. A similar finding has been reported by Meiners et al. (1995), who examined cultures of astrocytes from the cerebral cortices of newborn Sprague-Dawley rats and found that fibrous astrocytes assume "rocky" shapes and express TN at extremely high levels. As fibrous astrocytes did not appear in the primary cultures of astrocytes from the TN-deficient mice it appears that tenascin is required for the development of fibrous astrocytes. "
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    ABSTRACT: Astrocytes in primary culture can be classified morphologically into two types: fibrous astrocytes and protoplasmic astrocytes. To examine the role of tenascin-C (TN) in an in vitro astrocyte culture, primary cultures of astrocytes prepared from the brains of wild-type and of TN-deficient embryonic mice were analyzed. In primary culture of astrocytes from TN-deficient mice fibrous astrocytes did not appear and astrocytes did not become tile-shaped when they came in contact with each other. The rate of 5-bromo-2'-deoxyuridine incorporation in a cell proliferation assay was much lower for astrocytes from TN-deficient mice than for astrocytes from wild-type mice. These results suggest that TN is an essential molecule for maintaining the proliferation and proper morphology of astrocytes in primary culture.
    Preview · Article · Jul 2007 · In vivo (Athens, Greece)
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